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TURNER, NSQF LEVEL - 5, , 4th Semester, TRADE THEORY, SECTOR: Production & Manufacturing, , DIRECTORATE GENERAL OF TRAINING, MINISTRY OF SKILL DEVELOPMENT & ENTREPRENEURSHIP, GOVERNMENT OF INDIA, , NATIONAL INSTRUCTIONAL, MEDIA INSTITUTE, CHENNAI, Post Box No. 3142, CTI Campus, Guindy, Chennai - 600 032, , Copyright @ NIMI Not(i)to be Republished
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Sector, , : Turner, , Duration : 2 - Years, Trade, , : Turner 4th Semester - Trade Theory - NSQF level 5, , Copyright© 2018 National Instructional Media Institute, Chennai, First Edition :, , December 2018, , Copies : 1,000, , Rs.230/-, , All rights reserved., No part of this publication can be reproduced or transmitted in any form or by any means, electronic or mechanical,, including photocopy, recording or any information storage and retrieval system, without permission in writing from the, National Instructional Media Institute, Chennai., , Published by:, NATIONAL INSTRUCTIONAL MEDIA INSTITUTE, P. B. No.3142, CTI Campus, Guindy Industrial Estate,, Guindy, Chennai - 600 032., Phone : 044 - 2250 0248, 2250 0657, 2250 2421, Fax : 91 - 44 - 2250 0791, email : chennai-nimi@nic.in, nimi_bsnl@dataone.in, Website: www.nimi.gov.in, , Copyright @ NIMI(ii)Not to be Republished
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FOREWORD, The Government of India has set an ambitious target of imparting skills to 30 crores people, one out of, every four Indians, by 2020 to help them secure jobs as part of the National Skills Development Policy., Industrial Training Institutes (ITIs) play a vital role in this process especially in terms of providing skilled, manpower. Keeping this in mind, and for providing the current industry relevant skill training to Trainees,, ITI syllabus has been recently updated with the help of Mentor Councils comprising various stakeholder's, viz. Industries, Entrepreneurs, Academicians and representatives from ITIs., The National Instructional Media Institute (NIMI), Chennai has now come up with instructional material to, suit the revised curriculum for Turner 4th Semester Trade Theory NSQF Level - 5 in Production &, Manufacturing Sector under Semester Pattern. The NSQF Level - 5 Trade Theory will help the trainees, to get an international equivalency standard where their skill proficiency and competency will be duly, recognized across the globe and this will also increase the scope of recognition of prior learning. NSQF, Level - 5 trainees will also get the opportunities to promote life long learning and skill development. I have, no doubt that with NSQF Level - 5 the trainers and trainees of ITIs, and all stakeholders will derive, maximum benefits from these IMPs and that NIMI's effort will go a long way in improving the quality of, Vocational training in the country., The Executive Director & Staff of NIMI and members of Media Development Committee deserve, appreciation for their contribution in bringing out this publication., Jai Hind, , RAJESH AGGARWAL, , Director General/ Addl.Secretary, Ministry of Skill Development & Entrepreneurship,, Government of India., , New Delhi - 110 001, , Copyright @ NIMI Not(iii)to be Republished
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PREFACE, The National Instructional Media Institute (NIMI) was established in 1986 at Chennai by then Directorate, General of Employment and Training (D.G.E & T), Ministry of Labour and Employment, (now under Directorate, General of Training, Ministry of Skill Development and Entrepreneurship) Government of India, with technical, assistance from the Govt. of the Federal Republic of Germany. The prime objective of this institute is to, develop and provide instructional materials for various trades as per the prescribed syllabi under the Craftsman, and Apprenticeship Training Schemes., The instructional materials are created keeping in mind, the main objective of Vocational Training under, NCVT/NAC in India, which is to help an individual to master skills to do a job. The instructional materials, are generated in the form of Instructional Media Packages (IMPs). An IMP consists of Theory book,, Practical book, Test and Assignment book, Instructor Guide, Audio Visual Aid (Wall charts and, Transparencies) and other support materials., The trade practical book consists of series of exercises to be completed by the trainees in the workshop., These exercises are designed to ensure that all the skills in the prescribed syllabus are covered. The, trade theory book provides related theoretical knowledge required to enable the trainee to do a job. The, test and assignments will enable the instructor to give assignments for the evaluation of the performance, of a trainee. The wall charts and transparencies are unique, as they not only help the instructor to effectively, present a topic but also help him to assess the trainee's understanding. The instructor guide enables the, instructor to plan his schedule of instruction, plan the raw material requirements, day to day lessons and, demonstrations., IMPs also deals with the complex skills required to be developed for effective team work. Necessary care, has also been taken to include important skill areas of allied trades as prescribed in the syllabus., The availability of a complete Instructional Media Package in an institute helps both the trainer and, management to impart effective training., The IMPs are the outcome of collective efforts of the staff members of NIMI and the members of the, Media Development Committees specially drawn from Public and Private sector industries, various training, institutes under the Directorate General of Training (DGT), Government and Private ITIs., NIMI would like to take this opportunity to convey sincere thanks to the Directors of Employment & Training, of various State Governments, Training Departments of Industries both in the Public and Private sectors,, Officers of DGT and DGT field institutes, proof readers, individual media developers and coordinators, but, for whose active support NIMI would not have been able to bring out this materials., , Chennai - 600 032, , R. P. DHINGRA, EXECUTIVE DIRECTOR, , Copyright @ NIMI(iv)Not to be Republished
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INTRODUCTION, TRADE THEORY, The manual of trade theory consists of theoritical information for the Fourth Semester couse of the Turner, Trade. The contents are sequenced according to the practical exercise contained in the manual on Trade, practical. Attempt has been made to relate the theoritical aspects with the skill covered in each exercise to, the extent possible. This co-relation is maintained to help the trainees to develop the perceptional capabilities, for performing the skills., The manual is divided into six modules. The distribution of time for the practicals in the six modules are given, below., Module 1, , Introduction to CNC, , 25 Hrs, , Module 2, , CNC Turning, , 75 Hrs, , Module 3, , Tool setting and data input, , 75 Hrs, , Module 4, , Programme and Simulation, , 75 Hrs, , Module 5, , CNC Turning operations, , 75 Hrs, , Module 6, , Advance Turning, , 200Hrs, , Total, , 525 Hrs, , The Trade Theory has to be taught and learnt along with the corresponding exercise contained in the manual, on trade practical. The indication about the corresponding practical exercise are given in every sheet of this, manual., It will be preferable to teach/learn the trade theory connected to each exercise atleast one class before, performing the related skills in the shop floor. The trade theory is to be treated as an integral part of each, exercise., The material is not the purpose of self learning and should be considered as supplementary to class room, instruction., TRADE PRACTICAL, The trade practical manual is intended to be used in workshop . It consists of a series of practical exercies to, be completed by the trainees during the Fouth Semester course of the Turner trade supplemented and, supported by instructions/ informations to assist in performing the exercises. These exercises are designed, to ensure that all the skills in the prescribed syllabus are covered., The skill training in the computer lab is planned through a series of practical exercises centered around some, practical project. However, there are few instance where the individual exercise does not form a part of project., While developing the practical manual a sincere effort was made to prepare each exercise which will be easy, to understand and carry out even by below average trainee. However the development team accept that there, is scope for further improvement. NIMI, looks forward to the suggestions from the experienced training faculty, for improving the manual., , Copyright @ NIMI(vi)Not to be Republished
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CONTENTS, Lesson No., , Title of the Lesson, , Page No., , Module 1: Introduction to CNC, 4.1.111, , CNC Technology basics, , 1, , 4.1.112, , Machine model, control system and specification, , 6, , 4.1.113, , Axis convention of CNC machine, , 18, , 4.1.114, , Importance of feedback system and Concept of co-ordinate geometry, , 23, , 4.1.115, , Coordinate Geometry & Machine Axis, , 25, , Module 2: CNC Turning, 4.2.116 -117, , Preparation of part programming, , 30, , 4.2.118, , Operational modes, , 44, , 4.2.119, , Types of offsets, , 48, , 4.2.120, , Tool path study of machining operation (Straight turning), , 52, , 4.2.121 -122, , Cutting parameters, cutting speed and feed, depth of cut,CSM,, tool wear, tool life, , 60, , Module 3: Tool setting and Data Input, 4.3.123-124, , Cutting tool materials for Turning, , 68, , 4.3.125, , Tool Geometry, Insert Type, Nomenclature of Inserts, , 74, , 4.3.126, , Describe tooling system for turning, , 77, , 4.3.127, , Setting work and tool offset, , 79, , 4.3.128, , Describe tooling system for CNC Turning centres, , 80, , 4.3.129, , Cutting tool material for CNC turning, , 81, , 4.3.130, , ISO Nomenclature for Turning tool holder, boring tool holder, indexable insert, , 82, , 4.3.131, , Tool holders and inserts for radial grooving, face grooving,, threading and drilling, , 85, , Module 4: Programme and Simulation, 4.4.132, , Preparation of Part programming as per drawing, , 87, , 4.4.133, , Checking using CNC Simulator, , 93, , 4.4.134, , Process and tool selection (CNC), , 94, , 4.4.135, , Part programme for Grooving, , 95, , 4.4.136, , Part progarmme for drilling, , 96, , 4.4.137, , Part progarmme for boring, , 97, , 4.4.138, , Part progarmme for threading, , 99, , Copyright @ NIMI Not(vii)to be Republished
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Lesson No., , Title of the Lesson, , Page No., , Module 5: CNC Turning Operations, 4.5.139, , Programming on CNC Tapping, , 101, , 4.5.140, , CNC Programme for Grooving (OD/ID), , 103, , 4.5.141, , CNC Programming for threading, , 105, , 4.5.142, , Trouble shooting in CNC machines, , 107, , 4.5.143, , Factors affecting quality & productivity, , 114, , 4.5.144, , Parting off Operation in a CNC, , 119, , 4.5.145, , Bar Feeding System through Bar Feeder, , 117, , 4.5.146, , Input and Output of data, , 118, , 4.5.147, , DNC system, , 123, , 4.5.148, , Use of CAM Programme, , 124, , Module 6 : Advance Turning, 4.6.149, , Setting of tool for taper threads, calculation of taper setting and thread depth, , 126, , 4.6.150, , Interchangeability meaning, procedure for adoption, quality control, procedure for quality production, , 135, , 4.6.151-152, , Importance of Technical term used in Industry, , 158, , 4.6.153, , Terms used in part drawings and Geometrical tolerances, and symbols, , 175, , 4.6.154-156, , Automatic lathe - types - parts, toolholders, theory of calculation, , 184, , Copyright @ NIMI(viii), Not to be Republished
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LEARNING / ASSESSABLE OUTCOME, On completion of this book you shall be able to, • Set (Both job and tool) CNC turning centre and produce components, as per drawing by preparing part programme., • Manufacture and assemble components to produce utility items, by performing different operations and observing principle of, interchangability and check functionality item (screw jack, vice, spindle, box nut, marking block, drill chuck, collet chuck etc, by, different operation)., • Threading (Square thread) BSW, ACME, Metric, thread on taper,, different boring operations., • Make a process plan to produce components by performing, special operations on lathe and check for accuracy., • Perform special operation in CNC lathe worm shaft cutting, boring,, threading etc.,., , Copyright @ NIMI Not(ix)to be Republished
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SYLLABUS, Fourth Semester, Week, No., 79, , 80-82, , Duration: Six Month, , Ref. Learning, Outcome, •, , Set (both job and, tool) CNC turn, centre and produce, components as per, drawing by, preparing part, programme., , -do-, , Professional Skills, (Trade Practical), with Indicative hours, 111. Personal and CNC machine, Safety: Safe handling of tools,, equipment and CNC, machine. (2 hrs.), 112. Identify CNC machine, CNC, console. (5 hrs.), 113. Demonstration of CNC lathe, machine and its parts - bed,, spindle motor and drive,, chuck, tailstock, turret, axes, motor and ball screws, guide, ways, LM guides, console,, control switches,coolant, system, hydraulic system,, chip conveyor, steady rest., (7 hrs.), 114. Working of parts explained, using Multimedia based, simulator for CNC parts, shown on machine. (6 hrs.), 115. Identify machine over travel, limits and emergency stop., (1 hrs.), , 116. Conduct a preliminary check, of the readiness of the CNC, turning centre viz., cleanliness, of machine, referencing – zero, return, functioning of, lubrication, coolant level,, correct working of sub-system., (2 hrs.), 117. Identification of safety, switches and interlocking of, DIH modes. (1 hrs.), 118. Machine starting & operating, in Reference Point, JOG and, Incremental Modes. (12 hrs.), 119. Check CNC part programming, with simple exercises and, using various programming, codes and words. (12 hrs.), 120. Check the programme, simulation on machine OR, practice in simulation software, in respective control system., (12 hrs.), , Professional Knowledge, (Trade Theory), CNC technology basics:, Difference between CNC and, conventional lathes., Advantages and disadvantages of, CNC machines over conventional, machines., Machine model, control system, and specification., Axes convention of CNC machine, - Machine axes identification for, CNC turn, centre., Importance of feedback devices, for CNC control., Concept of Co-ordinate geometry,, concept of machine axis., , Programming – sequence, formats,, different codes and words., Co-ordinate system points and, simulations., Work-piece zero points and ISO/, DIN G and M codes for CNC., Different types of programming, techniques of CNC machine., Describe the stock removal cycle in, CNC turning for OD / ID operation., L/H and R/H tool relation on speed., Describe CNC interpolation, open, and close loop control systems. Coordinate systems and Points., Program execution in different, modes like manual, single block, and auto., Absolute and incremental, programming., Canned cycles., Cutting parameters- cutting speed,, feed rate , depth of cut, constant, surface speed, limiting spindle, speed, tool wear,, tool life, relative effect of each, cutting parameter on tool life., , Copyright @ NIMI(x)Not to be Republished
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83-85, , -do-, , 86-88, , -do-, , 121. Absolute and incremental, programming assignments, and simulations. (12 hrs.), 122. Linear interpolation, and, Circular interpolation, assignments and, simulations on soft ware. (24hrs.), , Selection of cutting parameters from, a tool manufacturer’s catalog for, various operations., Process planning & sequencing,, tool layout & selection and cutting, parameters selection., Tool path study of machining, operations., Prepare various programs as per, drawing., , 123. Perform Work and tool setting:, - Job zero/work coordinate, system and tool setup and live, tool setup. (12 hrs.), 124. Carryout jaw adjustment, according to Diameter and, tooling setup on Turret., (12hrs.), 125. CNC turning centre operation in, various modes: JOG, EDIT,, MDI, SINGLE BLOCK, AUTO., (12 hrs.), 126. Program entry. (2 hrs.), 127. Set the tool offsets, entry of, tool nose radius and, orientation. (12 hrs.), 128. Conduct work off set, measurement, Tool off set, measurement and entry in, CNC Control. (8 hrs.), 129. Make Tool nose radius and, tool, orientation entry in CNC control., (6 hrs.), 130. Jaw removal and mounting on, CNC Lathe. (4 hrs.), 131. Manual Data Input (MDI) and, MPG mode operations and, checking of zero offsets and, tool offsets. (9 hrs.), , Tool Nose Radius Compensation, (G41/42) and its importance, (TNRC)., Cutting tool materials, cutting tool, geometry – insert types, holder, types, insert cutting edge, geometry., - Describe Tooling system for, turning, - Setting work and tool offsets., - Describe the tooling systems, for CNC TURNING Centers., - Cutting tool materials for CNC, Turning and its applications, - ISO nomenclature for turning tool, holders, boring tool, holders, indexable inserts., - Tool holders and inserts for, radial grooving, face grooving,, threading, drilling., , 132. Program checking in dry run,, single block modes. (6 hrs.), 133. Checking finish size by over, sizing through tool offsets., (9 hrs.), 134. Part program preparation,, Simulation & Automatic Mode, Execution for the exercise on, Simple turning & Facing (step, turning) (10 hrs.), 135. Part program preparation,, Simulation & Automatic Mode, Execution for the exercise on, Turning with Radius / chamfer, with TNRC. (10 hrs.), , Prepare various part programs as per, drawing & check using CNC simulator., Processes and Tool selection related to, grooving, drilling, boring & threading, , Copyright @ NIMI Not(xi)to be Republished
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136. Part program preparation,, Simulation & Automatic Mode, Execution of CNC Machine for, the exercise on Blue print, programming contours with, TNRC. (10 hrs.), 137. Machining parts on CNC lathe, with parallel, taper, step, radius, turning, grooving & threading., (15 hrs.), 138. Carryout Drilling /Boring cycles, in CNC Turning. (15 hrs.), (First 60 % of the practice is on, CNC machine simulator,, followed by 40 % on machine.), 89-91, , -do-, , 139. Geometry Wear Correction., Geometry and wear offset, correction. (10 hrs.), 140. Produce components on CNC, Machine involving different, turning operations viz.,, • h Stock removal cycle OD, • h Drilling / boring cycles, • h Stock removal cycle ID, • h Carryout threading in different, pitches. (18 hrs.), 141. Produce components by involving, turning operation and part, programme exercises of, C N C, turning viz.,, • h Grooving and thread cutting, OD, • h Grooving and thread cutting, ID, • h Threading cycle OD, • h Sub programs with repetition, • h Using Sub Programs &, Cycles in the Main Program., (18 hrs.), 142. Part off: Part Prog. (4 hrs.), 143. Produce job involving profile, turning, threading on taper,, boring, etc. operations. (22, hrs.), 144. Demo on M/C on bar feeding, system. (simulation/ video), (1 hrs.), 145. DNC system setup., (Optional), 146. Run the machine on DNC, mode.(Optional), 147.CAM programme, execution.(Optional), 148. Data Input-Output on, CNCmachine. (2 hrs.), , - Describe Tapping on CNC, turning., - Programming for, Grooving/Threading on OD/, ID in CNC Turning., - Trouble shooting in CNC, lathe machine, - Identify Factors affecting, turned part quality/, productivity., - Parting off operation, explanation., - Bar feeding system, through bar feeder., - Input and Output of Data., - DNC system. Interlacing, with PC., - Use of CAM Programme., (Optional), , Copyright @ NIMI(xii)Not to be Republished
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92 - 93, , 94-95, , 96, , 97, , Manufacture and, assemble components, to produce utility items, by performing different, operations & observing, principle of, interchangeability and, check functionality., [Utility item: - screw, jack/ vice spindle/, Box nut, Marking, block, drill chuck,, collet chuck etc.;, different operations:, - threading (Square,, BSW, ACME,, Metric), Thread on, taper, different, boring (Plain,, stepped)], -do-, , -do-, , Make a process, plan to produce, components by, performing special, operations on lathe, and check for, accuracy. [Accuracy, - ±0.02mm or proof, machining &, ±0.05mm bore;, Special operation Worm shaft cutting, (shaft) boring,, threading etc.], , 149. Theard on taper, surface(Vee form), (50 hrs.), , Setting of tool for taper, threadscalculation of taper, setting and thread depth., Heat treatment – meaning &, procedure hardening,, tempering, carbonizing etc., Different types of metal used, inengineering application., , 150.Manufacturing&, Assembly of Screw, jack/vice/Box nut by, performing different lathe, operation.(To use earlier, produce screw jack)., (50 hrs.), , Interchangeability meaning,, procedure for adoption, quality, control procedure for quality, production., , 151. Prepare different types, of documentation as, per industrial need by, different methods of, recording information., (4 hrs.), 152. Turn Bevel gear blank., (21 hrs.), , Importance of Technical English, terms, used in industry –(in simple, definition, only)Technical forms, process, charts,, activity logs in required formats of, industry, estimation, cycle time,, productivity reports, job cards., , 153. Read a part drawing,, makeaprocess plan, , Terms used in part drawings and, interpretation of drawings –, tolerances,, geometrical symbols - cylindricity,, parallelism. etc., , Copyright @ NIMI Not(xiii)to be Republished
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98, , -do-, , 154. Practice of special operations, on lathes - worm gear cutting., (Shaft) (25 hrs.), , 99, , -do-, , 155. Boring on lathe using soft jaws, to make bush with collar, (standard) on non ferrous metal, and check with dial bore gauge, to accuracy of +/- 0.05 mm., (15 hrs.), 156. Make Arbor support bush., (Proof Machining) (10 hrs.), , 100 -101, , Automatic lathe-its main parts,, types diff. Tools used-circular, tool etc, , Related theory and, calculation., , In-plant training/ Project work (Any Project to be done onCNC machine), 1. Taper Sunk, 2. Socket With Split Collet, 3. Screw Jack, 4. Spindle With Hub, 5. Morse Taper Eccentric, 6. Crank Shaft With Taper Sleeve, , 102-103, , Revision, , 104, , Examination, , Copyright @ NIMI(xiv), Not to be Republished
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Production & Manufacturing, Turner - Introduction to CNC, , Related Theory for Exercise 4.1.111, , CNC Technology basics, Objectives: At the end of this lesson you shall be able to, • describe the fundamentals of NC controls, • state the present status of CNC technology, • state the different between conventional lathe and CNC lathe, • state the specification of CNC lathe, • state the advantages and disadvantages of CNC., When the computer was invented, the inventor himself, must not have dreamt of the use of computers in various, fields of life which is drastically changing the entire, scenario of the Universe. It is now an integral part of our, day to day life. There is lot of research going on with the, help of computers in the field of factory automation. The, declining cost of computers coupled with the invention of, Multi task high speed micro processors, really made an, industrial revolution and there seems to be no end for, this. A distinct trend can be observed in industries which, include an increase in the use of Computer controlled, Machine tools, the application of new manufacturing, systems, such as laser beam machines and appearance, of new generation of industrial robots in the production, line, the manufacturing management through MRP I, MRP, II & MRP III etc.(Material Resource Planning), , -, , The next logical extension is a fully automated factory, which employs a flexible manufacturing system (FMS), and Computer Aided Design/Computer Aided, Manufacturing (CAD/CAM) techniques., , -, , The latest of the above is Computer Integrated, Manufacturing (CIM) which includes battery of CNC, machines, with flexible modules for manufacturing tool, head changers, automatic material handling system, like AGV's (Automated Guided Vehicle) etc with, minimum number of operating personnels., , Fundamentals of NC controls, , Evolution of automation, , NC equipment has been defined by Electronics Industries, Association (EIA) as "A system in which actions are, controlled by the direct insertion of numerical data at some, point. The system must automatically interpret at some, portion of the data"., , Automatically controlled factory is nothing more than the, latest development in the industrial revolution that began, in Europe two centuries ago and progressed through the, following stages:, , In a typical NC system the part program is prepared on a, punched tape. The part programme is arranged in blocks, of information needed for processing a segment of work, piece, the segment of length, speed, etc., , -, , Mechanisation started in 1870 at the beginning of, industrial revolution with simple production machines., , Advantage of NC machine are, , -, , In 18th Century fixed automatic mechanism and, transfer lines came into existence for faster output, and shorter production time., , -, , Simple automatic control machines and copying, machines were invented in the later part of the 18th, century. After 1950 the industrial automation was, started. In this second phase of the industrial, automation/revolution, workers, instead of physically, performing all the task are placed in the control of the, machines., , Progressive change after 1950 is as follows, -, , The introduction of numerical control (NC) in 1952, opened a new era in automation., , -, , The extension of NC was Computerised Numerical, Control (CNC) machine tools in which computer (Micro, Processor) is included as an integral part of the control, system., , -, , Commercial Industrial robot was manufactured in, 1961 along with CNC systems. The use of these, robots, are well utilised only after 1970's., , -, , Complex shapes can be machined easily, , -, , Accuracy and repeatability is achieved., , -, , High production rate, , -, , Reduced component rejection, , -, , Less operator skill and involvement, , There are many disadvantages of NC system:, -, , If tape is spoiled the entire programme of, manufacturing will be affected, , -, , Editing of the program in tape is not very easy., , -, , Manual loading of tape is a laborious job., , -, , Instruction are read, block by block and carried out, which is slow when compared to CNC machine tools:, , -, , If the punch reader is not reading the program properly, then the entire production is lost., , Computer numerical control, A dedicated micro processor or mini computer on the, machine control makes the computer numerical control., CNC machines are very popular coupled with lots of other, advantages:, , Copyright @ NIMI Not to be Republished, , 1
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Advantages, , 4 Changing of cutting :, conditions, , Step less Speed, feed etc are, changed easily through, programming instruction., , 5 In process control, , Self diagnosing and gauging, through measuring probes, the parts and tools are, available as an in-process, control., , -, , Accuracy and repeatability is very high, , -, , Reduced scrap and rework, , -, , Reduced inspection time, , -, , Ease of inter changeability of machined parts, , -, , Reduced space, , -, , Reduced, material handling, -, , B Keeping machining time to minimum, , -, , Less paper work, , Higher metal removal rate through, , -, , Less lead time, , -, , Proper cutting tools, , -, , Less inventory, , -, , Rigid machine spindle, , -, , Easy editing of programme, , -, , Higher spindle power, , -, , Complicated shapes and contours are easily, manufactured with quality assurance and better, production management., , -, , Higher feed power, , -, , Rigid structure, , -, , Multi spindle, , -, , Multi turrets etc., , :, , -, , Better utilisation of machines., , -, , Reduced tooling, , -, , Reduced operator skill, , Higher quality is achieved, , -, , Jig not used but with minimum fixtures, , -, , Servo mechanism, , -, , -, , Reduced floor space, , For correction of feed, through motors, , -, , Higher level of integration such as DNC, FMS, CAD/, CAM, CIM etc.,, , -, , Curvic coupling, , -, , For quick indexing, , -, , Linear motion guides -, , For heavy load movement, of slides., , -, , Linear ball screw, , -, , For accurate friction free, backlash free movement, , -, , Encoders and tacho, generator, , -, , For accurate positioning, and velocity error correction, etc., , Disadvantages of CNC machines, -, , High cost of machine, , -, , High cost of training needs, , -, , High Maintenance cost, , Major advantages of CNC machines are, -, , Higher production, , -, , High quality production, , These are achieved through:, Higher production, , In automobile, aircraft and general engineering industry,, CNC machines are common sight now a days. CNC is, used to control almost all types of machines and some of, the commonly used machines are listed below:, -, , CNC lathes, , A., , Keeping idle time as minimum as possible, , -, , CNC Milling/drilling machine, , B., , Keeping machining time to a minimum, , -, , CNC turning centres., , -, , CNC Turn mill centre, , -, , CNC Machine centre, Multi machining centre, , -, , CNC Tool and cutter grinding., , -, , CNC Grinding machine, surface, cylindrical etc., , Kept as minimum by ATC,, quick change tool turret etc., (max.time is less than 8, sec.), , -, , CNC boring and jig boring machines etc., , -, , CNC EDM, Wire cut EDM etc., , -, , CNC Gear hobbing, gear shaping, gear grinding etc., , Rapid movement is easily, achieved through best servo, feedback motors, , -, , CNC Electron beam welding, , -, , CNC Laser/plasma/arc welding machine etc, , A Keeping idle time as minimum, 1 Loading/unloading, , 2 Tool Change time, , 3 Movement of slide, , 2, , Applications of CNC, , :, , :, , :, , Through quick work holding, and work handling system, like pallets, robots etc., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.1.111
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-, , CNC Co-ordinate measuring machines, , -, , CNC Nibbling press, press brakes, turret, , Present status CNC technology, Now a days, CNC controllers with system like Sinumeric,, Fanuc, Friera, Allen Brandly, Mazak etc come with graphic, , Some latest controls are having "DOS" front end with, CAD/CAM facility in which one can design a component, and get the computer assisted part programmes (CAPP), and proving the component on the machine control itself, without wasting much time and money. Modern machine, tools have multi spindle with a spindle speed of 75000, , display of tool, paths, along with other software's have, considerably reduce the manual part programming of, three dimensional jobs., User defined parametric programming, Standard Cycles, like stock removal, drilling milling pattern etc are now a, day's standard component of the Systems., , rpm; Cutting feed rate of 5000 mm/min, and rapid traverse, of 20000 mm/min. Use of multi various sensing elements, with adaptive controls, remote diagnostics system makes, the machine more versatile and free from accidents., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.1.111, , 3
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The silent and salient use of computers in factory, automation and in factory management will boost the, quality and quantity in production, which in turn will, definitely change the lifestyle of the people in future., Advantages of CNC machines over conventional, lathes, , -, , Production rate is more., , -, , Profitability is high., , -, , Repeatability is very high compared to conventional, lathe., , -, , One operator can operate more than one machine., , -, , Lesser production cost., , -, , Reduced part inventory., , -, , Less manual work., , -, , Semi skilled operator can operate the machine., , -, , Reduced floor space requirements., , -, , Greater accuracy., , -, , Improved manufacturing control., , -, , More flexibility., , -, , Complicated parts shape can be easily machined., , -, , Alteration in dimension is easier through programme., , -, , More number of tools are made available, , -, , Simulation is possible with that we can verify the, dimensions of the component., , Disadvantages of CNC machines, , Difference between conventional and CNC lathes, Conventional lathe, 1, , Involves more manual, work, , Less manual work, , 2, , Skilled labour needed, , Basic Skill is enough, , 3, , Less accuracy, , More accuracy, , 4, , Less flexible, , More flexible, , 5, , No part programming, , Part programming, required, , 6, , Any alteration is, difficult, , Re-programming for, dimensional changes, made easier manually, Once the programme is, done, the computer, takes care, , 7 For every component, machining is done, with great care., , 4, , CNC, , 8, , Simulation or trial, run not possible, , Simulation or trial run, possible and correction, may be done if required., , 9, , Less production rate, , More production rate, , 10 Repeatability is not, possible, , Rate of repeatability, is high, , 11 Individual operator, required for each, machine, , One operator can, operate more than, one machine, , -, , Higher investment cost., , -, , Higher maintenance cost., , -, , Training of CNC operator involves more cost., , -, , Semi skilled or unskilled operator cannot do, programming in CNC., , -, , Cost of spare parts and tool cost are high., , -, , Suitable for mass production only., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.1.111
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SPECIFICATIONS OF C.N.C LATHE, 1, , No. of controlled axis, , 2, , 2, , Interpolation, , Linear/circular/parabolic, , 3, , Maximum swing over bed, , 320 mm, , 4, , Maximum machining length, , 245 mm, , 5, , Collet, , ID = 56 mm OD = 48 mm, , 6, , Spindle taper hole, , ∅52 mm, , 7, , Maximum bar dia, , ∅38 mm, , 8, , Spindle head type, , A2 - 5, , 9, , Spindle speed range, , 60 to 5000 R.P.M, , 10, , Main motor, , 3.70 KW, , 11, , Chuck size, , ∅200 mm, , 12, , Chuck type, , Hydraulic, solid, , 13, , Rapid transfer speed on x axis, , 18 metre/min, , 14, , Rapid transfer speed on z axis, , 18 metre/min, , 15, , X axis travel, , 200 mm, , 16, , Z axis travel, , 320 mm, , 17, , Guideway type, , Linear guideway, , 18, , Turret type, , Gang type, , 19, , Turret tool, , Boring bar size 20/20 mm ∅20 mm, , 20, , Weight, , 1700 Kg, , 21, , Dimensions, , 1600x1250x1650 mm, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.1.111, , 5
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Production & Manufacturing, Turner - Introduction to CNC, , Related Theory for Exercise 4.1.112, , Machine model, control system and specification, Objectives : At the end of this lesson you shall be able to, • explain the control panel, • list the control keys and learn technical specification of CNC machine, • list the address keys., , 6, , Copyright @ NIMI Not to be Republished
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Introduction, The CNC control system of a machine tool includes mainly, control unit and the motion control system. The motion, control system includes servo motor, drives, axis, postioning devices. The control systems are classified, , as contouring system, point to point system, closed loop/, open loop system and based on number of axis of the, machine.The details of the control unit and the control, systems are shown in the following pages., , 1 Power consumption main motor (relative display), 2 Chuck open/closed, 3 Sleeve forwards, 4 Sleeve backwards, 5, 6 Central lubrication manual with display, 7 Tool turret, manual operation, 8 Coolant On/Off with display, 9 Single item for bar feed with display, 10, 11 Drives On, 12 Drives off, 13 Control On, 14 Feed rate override switch 0-120%, 15 Emergency-off button, , EMCO CONTROL PANEL, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.1.112, , 7
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Keys and display field, , Display field, , Alarm (red), The display is bright whenever an alarm occurs. The alarm number is displayed on the, screen. The alarms are explained in the, alarm list., Position not yet reached (green), The display is bright until the set position, has been reached., Feed stop (red), The display is bright if the feed is stopped, while the program is running., Program running (green), The display is bright until the program has, been completed. Even if the machine is not, moving., Key assignment display (yellow), If the "key assignment display is bright, the, lower-case function (the bottom function) of, a dual-function key is displayed in the input, line when the dual function key is depressed., If the "key assignment." Display is not bright,, the upper function is entered. Switchover is, executed automatically by the controller after a word has been entered in the parts, cases, switchover can be executed by, means of key in the address keypad., , 8, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.1.112
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Address keys/numeric keys, x), Start of program, , x), Skip block, , x), Address block number, , x), Address path condition, , SINUMERIC 810 T, , Alternate changeover to top and, bottom functions. The display is then, either bright or dark., Number 7, Address Position data, , Number 8, Address Position data, Number 9, Address Position data, , x), Address Position data, x), Address Position data, , SINUMERIC 810 M, Address keys, numeric keys and symbol keys, , Number 4, Address Interpolation parameter, Number 6, Address Interpolation parameter, Number 5, Address Interpolation parameter, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.1.112, , 9
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Number 6, , Space character, , Address Interpolation parameter, , Address Auxiliary function, , x), , Additional, , Address Radius B, , unassigned x), Address Radius U, , Mulitiplication, Address Angle A, Number 1, , End of block, , x), In the input line characters appear which are not normally permitted for normal programming., The characters a,b,c,d,e,f are required to enter or modify, commands in CLB00 machine code.(@----)., Input and correction, , Address Feed, Number 2, Address tool correction, Number 3, Address Subroutine, , x), Address No. of passes, Subtractio n, Address Additiona l function, Sign input line, Address Additiona l function, , Number 0, Address Spindle speed, Decimal point, , Delete input, The input line is deleted character-bycharacter. If the key remains depressed, the characters entered are deleted in, sequence until the input line is empty., Delete word/block, The word identified by the correction, pointer is deleted in the parts program, memory if the respective address is in, the input line. A complete block is, deleted if the respective block number, is in the input line., Modifying a word, The word identified with the correction, pointer is replaced by the word in the, input line. The addresses of both words, must be identical., Entering a word, The word in the input line is transferred, to the parts program memory, or into, list displays or input forms., , Address Tool number, , 10, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.1.112
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Control keys, Channel selection switch, The CRT display is switched to the channel, selected. Selection is by repeated depressing of the channel selection switch., Acknowledging alarms, , Correction pointer left/right, The correction pointer is moved to the left, or right word-by-word. The correction pointer, jumps from the beginning of the block to the, end of the previous block or from the end of, the block to the beginning of the following, block. If the key remains depressed, the, correction pointer goes to the beginning or, end of the program., , Alarm form alarm No. 3000 onwards, e.g., "General programming error" alarm can be, acknowledged with this key. "Rest alarm is, not acknowledged!, Actual value display selection with, double-height characters, If the key is depressed again, the previous, display reappears., Diagnostics and start up, , Correction pointer backwards/forwards, , Selection of machine data and switching to, start-up state after entering pass word., , The correction pointer is moved backwards, or forwards block-by-block., , Search key, , If the key remains depressed, the correct, pointer goes to the beginning or end of the, program., Paging backwards/forwards, The CRT display is paged up or down one, page at a time., , Searching for a particular address or word, in the parts program memory. The expression appearing in the input line when the, search key is depressed is looked for. After, the search key has been depressed, the correction pointer marks the next expression, found., Integrated machine control panel, , Integrated machine control panel, , SINUMERIC 810 T, , SINUMERIC 810 M, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.1.112, , 11
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Reset, , Operating mode selection key, , The running program is aborted Alarms, are deleted (up to alarm No. 2999). The, controller is brought to the basic state!, , The following modes can be selected via a, soft key:, , Single block, The parts program is processed blockby-block. Start is by means of "Program, START"., Program STOP, The running program is interrupted The, program can be resumed with "Program, START"., Program START, A parts program is started. The functions, stored are transferred to the PLC in automatic mode., Spindle STOP/START, Feed STOP/START, , Direction keys, When the direction keys are actuated,, the axes are traversed in jog mode., , PRESET, MDI AUTOMATIC, JOG INC 1 TO INC 10,000, (manual encoder), REPOS, AUTOMATIC, REFPOINT, Spindle speed slower/faster, The programmed spindle speed can be, modified in increments of 5 % in the range, of 50 % to 120 % . If the key is depressed, constantly, the final position is approached, in increment of 5 %. The percentage value, set is shown in the basic display., Feed slower/faster, The programmed feed is modified in the following increments from 0% to 120 % 0%, 1% 2% 4% 6% 8% 10% 20% 30% 40% 50%, 60% 70% 75% 80% 85% 90% 95% 100%, 105% 110% 115% 120%., If the key is depressed constantly the end, position is approached. The percentage, value set is displayed in the basic display., In rapid traverse mode the 100% value is, not exceed., , Rapid traverse override key, , Universal interface port, , If this key is depressed simultaneously, with the direction keys the axes are traversed in rapid traverse mode., , 12, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.1.112
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CALL PROGRAM FORM MEMORY FOR EXECUTION, , Switch control to reset, , Main program or subroutine, , Enter program number, , Store, , Program control, if desired (see next page), Single block, if desired, Cycle start, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.1.112, , 13
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PROCEDURE FOR BLOCK SEARCHING:, , 9 Press > (etc key) to bring Over Store., , 1 Select the AUTOMATIC pressing MODE button., , 10 Enter necessary Tool number, Spindle speed, "T",, "D","S","M" code., , 2 Close the feed rate completely., 3 Press (Etc key) and bring the BLOCK SEARCH menu., 4 Enter the necessary block number/sub program block, number., 5 Press START., 6 Confirm whether the required block reached on the, Monitor at N, 7 Press MODE button for bringing the REPOS mode,, and select REPOS., , 11 Press CYCLE START key., 12 Bring Automatic mode by pressing MODE key., 13 Press ACTUAL BLOCK (Look at the Cursor and the, block search complete)., 14 Continue to Run the program by pressing Cycle Start, key and watch Distance to go Actual position and the, Actual values. ('G' codes, M,F,S,T,D, etc.), , 8 Bring the offset values to Zero by Pressing the necessary (+) or (-) direction keys X,Y,Z and feed rate control switch at > 0%, , BLOCK SEARCHING AND RUNNING PROGRAMME, AUTOMATIC, , 14, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.1.112
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Machine models, CNC machines are generally grouped under 2 axis and, 3 axis or multi axis system. Horizontal 2 axis (x and z), are termed as CNC lathe and the vertical CNC machines, are called as machining centre., The machine models are also based on the spindle drives, namely., -, , Separately excited DC shut motor, , -, , 3 Phase AC induction motor, , The CNC machine models are also based feed drives, are, -, , AC servometer, , -, , DC servometer, , -, , Brushless DC servometer, , -, , Stepper motor or liner motor, , Technical Specification of CNC machines, 1, , 2, , Traverse, , Pallet, , x’ - 600 mm, , (Saddle movement), , y’ - 450 mm, , (Head movement), , z’ - 420 mm, , (Column movement), , Pallet size - 500x500mm, Max load - 500 Kgf, indexing position - 360 degree, , 3, , 4, , Spindle, , 11.Kw continuous 14.2 (intermitent), , Type of motor, and drive, , AC, , Bearing dia, , 100 mm, , Spindle taper, , ISO 40, , Spindle speeds, Spindle range, , 40 - 4000 Rpm or, 60 - 6000 Rpm (optional), , 5, , 6, , Constant range, , 40- 4000 Rpm or, 60 - 1500 Rpm (Optional), , Constant power, range, , 1000-4000 Rpm or, 1500-6000 Rpm (Optional), , Feeds, Rapid traverse, , 20 M/min, , x,y,z Axis cutting, feed rate, , 1 to 10000 mm/min, , Feed Motor, Torque X and, , 18.5 Nm, , Y axes z - Axis, , 29 Nm, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.1.112, , 15
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7, , Thrust Capacity, X - Axis, Y - Axis, Z - Axis, , 8, , 600 Kgf, 600 Kgf, 1000Kgf, , Ball Screw, Pitch, Dia, , 9, , 12 mm, 50 mm, , Auto Tool changer, No of tools, Max. Tool Dia, Max. Tool Weight, Max.Tool length, Tool changing time, , 10, , Twin pallet changer, No of pockets, Pallet changing Time, , 11, , 2 Nos, 25 Sec, , Hydraulic, Motor power, Tank Capacity, , 12, , 24 Nos, 10 mm, 15 Kgf, 350 mm, 6 to 12 seconds based on tools, , 3.7 Kw, 90 litres Indian Oil servo 32 or equivalent, , Machining capacity, Milling capacity (steel, 55 - 65 Kg/mm square), , 100 cc/min, , Drilling capacity (Steel, 55-65 Kg/mm square), , 30 mm diameter, Tapping Capacity (Steel, 55 -65 Kg/mm square), , 13, , Machining capacity, Machining capacity, , 10000Kg, , Floor space requirement, Basic machine, , 5900mm (w) x, 5550mm (L), x 3100 (H), , 15, , Air requirement, , 16 Ipm at 5 kg/ Sq.cm, , 16, , Electrical supply, , 50 KVA, , 14, , M 24 x 1.5 mm, , Control System, In CNC machines there are mainly two types of control, system,namely, , control also. These system are not good where extremely, accurate positioning is required., , 1 Open loop control system (Fig 1), 2 Closed loop control system (Fig 2), Open lop control system (Fig 1), In an open loop control system (Fig 1) in which there is no, arrangement for detecting or comparing the actual position, of the cutting tool on the job with the command studies., , Closed loop control system (Fig 2), , Therefore, this system is not providing any check to see, that the commanded position has actually been, achieved.There is no feed back of information to the, , Closed loop control (Fig 2) is a term which is used very, often when we talk about CNC machines. This term, signifies, that the control system has provisions to ensure, , 16, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.1.112
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tha the tool reaches the desired position, at the correct, feed rate, even if some errors creep in due to unforeseen, reasons., For instance in the previous example 60,000 pulses sent, in 2minutes by the control should cause a tool travel of, 60 mm at 30 mm/min, but even if the control sends these, pulses it cannot be ensured that the tool has really, travelled exactly 60 mm., A closed loop control has a device called encoder and this, can continuously ascertain the distance actually travelled, by the tool and then monitor the same, in the form of, feedback signals to the control. The control studies this, feedbacck information and takes corrective action in case, any error is detected in the tool position/feed rate., , Another control system is based on 5 axis & above, •, , Motion type CNC control system, , •, , Loop control system, , •, , Number of axis type CNC control, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.1.112, , 17
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Production & Manufacturing, Turner - Introduction to CNC, , Related Theory for Exercise 4.1.113, , Axis convention of CNC machine, Objectives: At the end of this lesson you shall be able to, • identify CNC machine by number of axes, • identify CNC machines by orientation of axes, • understand NC coordinate and learn X and Y axis movement., Types of CNC milling machines, , CNC vertical machining centre, , - VMC, , Milling machines can divided into three categories, , CNC horizontal machining centre, , - HMC, , 1 by the no of axes, , CNC horizontal boring mill, , (two, three or more), , Vertical Machining Centres (Fig 1), , 2 by the orientation of axes, (vertical or horizontal), 3 by the presence or absence of a tool changer., The spindle motion is up and down in vertical milling/, machining centre., The spindle motion is in and out in horizontal milling/, machining centre., These machines are capable to perform the following, operations:, Drilling, Reaming, boring, tapping, profiling, thread cutting, and many other operations., ATC: Automatic Tool changer., APC: Automatic pallet changer, CNC: Computer Numerical Control, With the above advanced features built in milling, machines become the new breed of machine tools called, machining centres., Machine axes, The machining centres are provided with minimum three, axes of ‘X’,’Y’&’Z’ axis and fourth axis machines become, more flexible i.e the fourth axis ‘A’ for vertical model and, ‘B’ of horizontal model. The machine with five or more, axes is of higher level of capacity., In aircraft industry 5 axes profile milling machine is used, for complex shapes and to reach cavities and various, angles., Meaning of half / full axis in NC language (what is half /, full axis machine), A full axis vertical machine has X,Y,Z as primary axes, and indexing table designated as ‘A’ axis which can, position but cannot rotate simultnesously is called 3 1/2, axes machine. If the machine is equipped with full rotating, table, simultaneously then it is called four axis machine, tool., In the milling systems, three most common machine tools, are, 18, , VMC is for flat type of work where the machining is done, on only one face of the part in single set up., An optional fourth axis can be provided by mounting rotary, table to the main table either vertically or horizontally, depending on the desired results and the model type., In the combination with a tailstock (usually supplied) the, fourth axis in the vertical configuration can be used for, machining long parts,which need support at both ends., For programming two types of systems are followed. In, one type programming always takes place form the view, point of the spindle, not the operators eye, view as if, looking straight down at 90o towards the machine, for, development of the tool motion., In the second type, various markers located some where, in the machine itself, show the positive and negative, motion of the machine axes. For programming,these, markers should be ignored. The programming directions, are exactly opposite to the markers on the machine tool., Horizontal machining centers (Fig 2), Horizontal CNC machining centres are also categorized, as multi - tool and versatile machines, and are used for, , Copyright @ NIMI Not to be Republished
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cubical parts, where the majority of machining has to be, done on more than one face in a single setup., , define the positive direction of the coordinate axes as, per the Fig 4., , Z - axis (Fig 5), , There are many applications in this area. Common, examples are large parts, such as pump housings, gear, cases, manifolds, engine blocks and so on. Horizontal, machining centres always include a special indexing table, and are typically equipped with a pallet changer and other, features., , The axis of the main (i.e. principle) machine spindle,, whether it be the axis of the tool spindle or the axis about, which the work piece rotates, is denoted as the Z axis., On machine tools, which do not possess principle spindle, (e.g. planning machines) the Z - axis is perpendicular to, the work holding surface., , Axis - nomenclature, The basic designation of the axis (i.e.), in Fig 3 which is, X, Y, Z, is decided by the right hand thumb rule and the, main spindle axis. The thumb indicates X - axis, fore finger, indicates Y - axis and the middle finger indicates Z - axis., , X - axis, The X - axis is always horizontal, parallel to the work, holding surface and perpendicular to the z - axis., Auxillary axes on NC machine, Apart from each side movement axes on the machine,, some other auxillary axes can exist. E.g. Rotary table., This rotary table axis is designed as A axis if it is parallel, to X direction. Similarly B and C axes for Y and Z, respectively., Right hand rule, , Y - axis, The Y - axis is perpendicular to both Z and X axis., Milling tool coordinate system (Fig 6), Classification of machines., CNC machines can be classified by various ways,, a) According to number of axis, , CNC machine can be classified as, The rotary movements about X, Y and Z are designated, • 2 axis machine, as A, B and C respectively. The right hand rule is used to, Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.1.113, , Copyright @ NIMI Not to be Republished, , 19
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• 3 axis machine, , Straight cut control, , • 4 axis machine, , The system provides feed motion in two axes (but not, simultaneously) and hence their capability is limited to, performing milling either along X axis or along Y axis., (Fig 8), , It should be noted that each axis has it own drive motor., b) According to CNC system, There are three types of CNC systems based on their, capability in providing feed in different axes., , • 1 Point -to- point control, , Contouring control, This can provide feed control in 3 axes. They are also, capable of providing simultaneous feed in 2 or 3 axis., Milling machine with contouring control can mill contours, made up of straight lines and arc/circular elements.., Depending on the number of axes that can be, simultaneously fed, contouring controls are further, classified as 2D control, 2 1/2D control and 3D control., i) 2D control, Machines with 2D control can be simultaneous feed only, in two of the 3 axes. They can mill only contours with, constant depth that too in just one plane ( X-Y) (Fig 9, & 10), •, , 2 Straight cut control, , ii) 2 1/2D control, , •, , 3 Contouring control, , Machines with 2 1/2D control can have simultaneous, feed of any of the two axis X-Y, X-Z,Y,Z and, hence they, can mill contours (of constant depth) in any one of the 3, planes. (Figs 11 & 12), , Point-to-point control, Machines with point-to-point control provide only one feed, axis while the other two axes can perform only rapid, motion. Machines with point-to-points control are suited, only for drilling operations. (Fig 7 ), , 20, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.1.113
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Part programming for turning centers, Diameter programming, The dimensioning of a turned component is generally, specified by its diameters. However, in turning operation,, the tool should approach the work piece in radial direction, for matching. Hence, for the sake of simplicity, most of, the turning centers are provided with diameter, programming facility., This means that all the movements of the tool along, X-axis should be doubled to represent the diametral rather, than radial movement. The selection of radius or diameter, programming depends upon the system variable set, during the integration of controller with the machine tool., , Axis system(Fig 2), In turning centers, the spindle axis is designated as Z., The radial axis perpendicular to the z-axis and away, toward the principle tool post is termed as x-axis .The, machine datum or home position may be the intersection, of spindle axis and clamping plane. At the start, the, controller display will show the axis position with respect, to home The work piece datum is fixed by the programmer, on the work piece for the convenience of part, programming. The difference between the tool tip position, and the turret datum is termed as offset., , Machine axis identification, NC coordinates system (Fig 1), All the NC machine toolmaker’s use of Cartesian, coordinate system for the sake of simplicity. The guiding, coordinate system followed for designating the axes is, the well known as right hand coordinate system., Designation of axes, First axes to be identified is the z axis .This is then followed, by x and y axes respectively., , Z-axis, The z-axis motion is along the spindle axis or parallel to, the spindle axis. In the case of machine without a spindle, such as shapers and planers, the z-axis is perpendicular, to the work holding surface., For machines such as milling, drilling and lathe, the cutting, tools move in the negative z direction to move a tool into, the work piece. The positive z motion increases the, clearance between the tool holder and work piece surface., When there are several spindles and slide ways, the, spindle perpendicular to the work holding surface may, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.1.113, , 21
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be chosen as the principle spindle. The primary Z motion, is then related to the primary spindle. The tool motions of, other spindles or slides, designated as U, V, W and P, Q,, R respectively.(Fig 3), X-axis, The principle motion direction of cutting tool on the work, piece is designated as x-axis .It is perpendicular to the, z-axis and should be horizontal and parallel to the work, holding surface whenever possible., , 22, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.1.113
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Production & Manufacturing, Turner - Introduction to CNC, , Related Theory for Exercise 4.1.114, , Imporatance of feedback system and Concept of co-ordinate geometry, Objectives: At the end of this lesson you shall be able to, • understand feedback system, • understand the cartesian coordinate system, • understand the four quadrants, • explain the difference between polar and rectangular coordinates., Importance of feed, Feed Back System:, •, , The feedback system is also referred to as the, measuring system., , •, , It uses position and speed transducers to continously, and monitor the position at which the cutting tool is, located at any particular instant., , •, , The MCU uses the difference between reference, signals and feedback signals to generate the control, signals for correcting position and speed errors.(Fig 1), The centre of the coordinate system (where the lines, intersect) is called the origin. The axes intersect where, both x and y are zero and is taken as origin The, coordinates of the origin are (0,0)., , A Cartesian coordinate system is coordinate system, that specifies each point uniquely in a plane by a pair of, numerical coordinates, which are the signed distance, to the point from two fixed perpendicular directed lines,, measured in the same unit of length. Each reference line, is called a coordinate axis of the system, and the point, where they meet is its orgin, at ordered pair (0,0). The, coordinates can also be defined as the positions of the, perpendicular projections of the point on to the two axes,, expressed as signed distances from the origin., One can use the same principle to specify the position of, any point in three-dimensional space by three cartesian, coordinates, its signed distances to three mutally, perpendicular planes (or, equivalently, by its perpendicular, projection onto three mutually perpendicular lines). In, general, n-cartesian coordinates (an element of real nspace) specify the point in an n-dimensioanl Euclidean, space for any dimension n. These coordinates are equal,, up to sign, to distances from the point to n mutually, perpendicular hyper planes., , An ordered pair contains the coordinates of one point in, the coordinate system. A point is named by its ordered, pair in the form of (x,y). The first number corresponds to, the X-coordinate and the second to the Y-coordinate., To graph a point, you draw a dot at the coordinates that, corresponds to the ordered pair. It’s always a good idea, to start at the orgin. The x-coordinate tells you how many, steps you have a take to the right (positive) or left, (negative) on the x-axis. And the y-coordinate tells you, how many steps to move up (positive) or down (negative), on the y-axis., The ordered pair (3,4) if found in the coordinate system, when you move 3 steps to the right on the x-axis and 4, upwards on the y-axis.(Fig 3), The ordered pair (-7, 1) is found in the coordinate system, when you mave 7 steps to the left on the x-axis and 1, step upwards on the y-axis.(Fig 3), , Coordinate system and ordered pairs, A coordinate system is a two-dimensional number line,, for example, two perpendicular number lines or axes., This is a typical coordinate system:, The horizontal axis is called the x-axis and the vertical, axis is called the y-axis., , Copyright @ NIMI Not to be Republished, , 23
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To find out the coordinates of a point in the coordinate, sysem you do the opposite. Begin at the point and follow, a vertical line either up or down to the x-axis. There is, your x-coordinate. And then do the same but following a, horizontal line to find the y-coordinate., Absolute coordinates, Absolute coordinates are based on the orgin (0,0), which, is the intersection of the X and Y axes. Use absolute, coordinates when you know the precise X and Y values, of the point., , To point: #0,3, To point: #-5,-3, Polar coordinate system, Points in the polar coordinate system with pole O and, polar axis L. The point with radial coordinate 3 and angular, coordinate 60 degrees or (3, 60°). and the point (4, 210°), represents polar coordinates., , With dynamic input, you specify absolute coordinates with, the # prefix is not used. For example, entering #3,4, specifies a point 3 units along the X axis and 4 units along, the Y axis from the orgin., The following example draws a line beginning at an X, value of -2, Y value of 1, and an endpoint at 3,4. Enter, the following in the tooltip., Command: line, From point: #-2,1, To point: #3,4, The line is located as follows:(Fig 4), , Relative coordinates or incremental coordinate, Relative coordinates are based on the last point entered., Use relative coordinates when you know the location of a, point in relation to the previous point., To specify relative coordinates, precede the coordinate, values with an @ sign. For example, entering @3,4, specifies a point 3 units along the X axis and 4 units along, the Y axis from the last point specified., The following example draws the sides of a triangle. The, first side is a line starting at the absolute coordinates -2,1, and ending at a point 5 units in the X direction and 0 units, in the Y direction. The second side is a line starting at the, endpoint of the first line and ending at a point 0 units in, the X direction and 3 units in the Y direction. The final line, segment uses relative coordinates to return to the starting, point., Command: line, , In mathematics, the polar coordinate system is a twodimensional coordinate system in which each point on a, plane is determined by a distance from a reference point, and an angle from a reference direction., The reference point (analogous to the orgin of a Cartesian, coordinate system) is called the pole, and the ray from, the pole in the reference direction is the polar axis. The, distance from the pole is called the radial coordinate or, radius, and the angle is called the angular coordinate,, polar angle., Uniqueness of polar coordinate & conversion to, cartesian coordinate., Adding any number full turns (360°) to the angular, coordinate does not change the corresponding direction., Similarly any polar coordinate is identical to the coordinate, with the negative radial component and in the opposite, direction. The polar co-ordinates ‘r’ and ø can be, converted into the cartesian coordinate (x,y) by using the, trignometric functions sine & cosine., x = r cos ø, , From point: #-2,1, , y = r sin ø, , To point: #5,0, , r=, , 24, , x2+y2 r = length of line, ø= its angle with axis, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.1.114
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Production & Manufacturing, Turner - Introduction to CNC, , Related Theory for Exercise 4.1.115, , Coordinate Geometry & Machine Axis, Objectives: At the end of this lesson you shall be able to, • understand the machine coordinate system, • state real number line, • understand cartesion coordinates system, • understand the cartesian coordinates of three-dimensional space., Machine coordinate system, Most of the CNC machinery have a default coordinate, assumed during power up of machine coordinate system., The origin of the system is called machine origin are home, zero location. Home zero is usually located at the tool, change position., In the manufacturing industry, with regard to numerically, controlled machine tools, the phrase machine coordinate, system refers to the physical limits of the motion of the, machine in each of its axes, and to the numerical coordinate, which is assigned (by the machine tool builder) to each of, these limits. CNC Machinery refers to machines and, devices that are controlled by the using programmed, commands which are encoded on to a storage medium,, and NC refers to the automation of machine tools that are, operated by abstract commands programmed and, encoded onto a storage medium., The cartesian coordinate system, Cartesian coordinates allow one to specify the location of, a point in the plane, or in three dimensional space. the, cartesian coordinates or rectangular coordinates system, of a point are a pair of numbers (in two dimensions) or a, triplet of numbers (in three - dimensions) that specified, signed distances from the coordinate axis. First we must, understand a coordinate system to define our directions, and relative positions (axis) and a reference position, (origin). A coordinate system can be rectangular or polar,, Just as points on the line can be placed in one to one, correspondence with the real number line, so points in, plane can be placed in one to one correspondence with, pairs of real number line by using two coordinate lines. To, do this, we construct two perpendicular coordinate line, that intersect at their origins, for convenience. Assign a, set of equally space graduations to the x and y axes, starting at the origin and going in both directions, left and, right (x axis) and up and down (y axis) point along each, axis may be established.We make one of the number, lines vertical with its positive direction upward and, negative direction downward. The other number lines, horizontal with its positive direction upward to the right and, negative direction to the left. The two number lines are, called coordinate axes; the horizontal line is the x axis, the, vertical line is the y axis, and the coordinate axes together, form the cartesian coordinate system or a rectangular, coordinate system. The point of intersection of the, coordinate axes is denoted by O and is the origin of the, coordinate system. See Fig 1., , It is basically, Two Real Number lines Put Together, one, going left - right, and the other going up- down. The, horizontal line is called x-axis and the vertical line is called, y-axis., The origin, The point (0,0) is given the special name “The Origin” ,, and is given the letter “O”., Rral number line, The basis of this system is the real number line marked at, equal intervals. The axis is labeled (X,Y or Z). One point, on the line is designated as the Origin. Numbers on one, side of the line are marked as positive and those to the, other side marked negative. See Fig 2., , Cartesian coordiantes of the plane, A plane in which a rectangular coordinate system has, been introduced is a coordinate plane or an x-y-plane. We, will now show how to establish a one to one, correspondence between points in a coordinate plane, and pairs of real number. If A is a point coordinate plane,, then we draw two lines through A, one perpendicular to, the x-axis and one perpendicular to the y-axis. If the first, line intersects the x-axis at the point with coordinate x and, the second line intersects the y-axis at the point with, coordinate y, then we associate the pair (x,y) with the A, (See Fig 2). The number a is the x-coordinate or abcissa, of P and the number b is the y-coordinate or ordinate of p;, we say that A is the point with coordinate (x,y) and denote, , Copyright @ NIMI Not to be Republished, , 25
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the point by A (x,y). The point (0,0) is given the special, name “The Origin” , and is sometimes given the letter “O”., Abscissa and Ordinate, The words “Abscissa” and “Ordinate” ... they are just the, x and y values:, •, , Abscissa: the horizontal (“x”) value in a pair of, coordinates: how far along the point is., , •, , Ordinate: the vertical (“y”) value in a pair of coordinates:, how far up or down the point is., , X and Y Axis, The horizontal line is called x-axis and vertical line is, called y-axis; both line runs through zero origin,(0,0) put, them together on a graph ... See Fig 6., It is basically, a set of two real Number lines., , Negative Values of X and Y, The Real Number Line, you can also have negative, values., Neagative: start at zero and head in the opposite direction;, See Fig 4, , Axis: The reference line from which distances are, measured., Example:, Point (6,4) is, Go along the x direction 6 units then go up 4 units up in the, y direction then “plot the dot”., And you can remember which axis is which by:, • the horizontal distance first,, • then the vertical distance., , So, for a negative number:, •, , go left for x, , •, , go down for y, , Ordered pair, , For example (-3,-5) means :, go left along the x axis 3 then go up 5 in the y-axis., (Quadrant II x is negative , y is positive), , The number are separated by a comma, and parentheses, are put around the whole thing like this: (7,4), Example: (7,4) means 7 units to the right (x-axis), and 4, units up(y-axis), , And (-3,-5) means :, go left along the axis 3 then go down 5 in the yaxis.(Quadrant III x is negative ,y is negative), Using Cartesian Coordinates, mark a point on a graph by, how far along and how far up it is; See Fig 5. The point, (12,5) is 12 units along the x-axis, and 5 units up on the yaxis., 26, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.1.115
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Cartesian coordinates of three dimensional space, In three-dimensional space (xyz space), oriented at right, angles to the xy-plane. The z axis, passes through the, origin of the xy-plane. Coordinates are determined, according to the east-west for x-axis north-south for yaxis, and up -down for the z-axis displacements from the, origin. The Cartesian coordinarte system is based on, three mutually perpendicular coordinate axes: the x-axis,, the y-axis, and the z-axis, See Fig 6 below. The three axes, intersect at the point called the origin. You can imagine, the origin being the point where the walls in the corner of, a room meet the floor. The x-axis is the horizontal line, along which the wall to your left and the floor intersect., The y-axis is the vertical line along which the wall to your, right and the floor intersect. the z-axis is the vertical line, alongwhich the walls intersect. the parts of the lines that, you see while standing in the room are the positive portion, of each of the axes. The negative part of these axes would, be the continuations of the lines outside of the room., Three-dimensional cartesian coordinate axes. A, representation of the three- dimensional cartesian, coordinate system. The positive x-axis , y-axis, and, positive z-axis are the sides labeled by x,y,z. The origin is, the intersection of all the axes. The branch of each axis, on the opposite side of the origin (the unlabeled side) os, the negative part., When dealing with 3-dimensional motion, is to set up a, suitable coordinate system. The most stright-forward, type of coordinate system is called a Cartesian system. A, Cartesian coordinate system consists of three mutually, perpendicular axes, the X, Y, and Z-axes. By convention,, the orientation of these axes is such that when the index, finger, the middle finger, and the thumb of the right -hand, are configured so as to be mutually perpendicular, the, index finger, the middle finger, and the thumb can be, aligned along the X,Y,Z-axes respectively. Such a, coordinate system is termed right-handed. See Fig 7. The, point of intersection of the three coordinate axes is, termed the origin of the coordinate system., , to the coordinate axis and opposite corners at the origin, and the given point., The points may now be defined in a three dimensional, volume or space. This permits to define points in three, dimensions from the origin. The Cartesian coordinates, (x,y,z) of a point in three-dimensions specify the signed, distance from the origin along the x,y, and z-axes,, respectively. Z-axis points become the third entry when, defining coordinate locations., Given the above corner-of-room analogy, we could form, the Cartesian coordinates of the point at the top of your, head,as follows. Imagine that you are five meters tall the, z-axis, and that you walk two meters from the origin along, the x-axis, then turn left and walk parallel to the y-axis four, meters into the room. the Cartesian coordinates of the, point at the top of your head would be (2,4,5)., For example, a notation of (2,4,5) corresponds to the, value of X2, Y4, and Z5. See Fig 9., , 3 DIMENSIONS, Cartesian coordinates can be used for locating points in 3, dimensions as in this example:, Figure 10. The point (2,4,5) is shown in three-dimensional, Cartesian coordinates., , The Cartesian coordinates of a point in three dimensions, are a triplet of numbers (x,y,z). The three numbers, or, coordinates, specify the signed distance from the origin, along the x,y, and z- coordinate axis respectively. They, can be visualized by forming the box with edges parallel, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.1.115, , 27
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(They are numbered in a counter clockwise direction), , QUADRANTS, The coordinate axes divide the plane into four parts,, called quadrants (See Fig 11). The quadrants are number, counter clockwise,starting from the upper right,labeled, I,II,III,IV with axes designations as shown in illustrations, below., , In Quadrant I : both x and y are positive, In Quadrant II : x is negative (y is still positive), In Quadrant III : both x and y are negative, In Quadrant IV : x is positive again, while y is negative., , When we include negative values, the x and y divide the, space up into 4 pieces:, , Quadrant, , X(Horizontal), , Y(Vertical), , Example, , l, , Positive, , Positive, , (3,2), , ll, , Negative, , Positive, , (-5,2), , lll, , Negative, , Negative, , (-2,-1), , lV, , Positive, , Negative, , (2,-5), , 28, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.1.115
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Example: the point “A” (3,2) is 3 units along the x-axis,, and 2 units up the y-axis., Both x and y are positive, so that point is i “Quadrant I”, Example: The point “C” (-2,-1) is 2 units along the axis in, the negative direction, and 1 unit down the y-axis in the, negative direction., Both x and y are negative, so that point is in “Quadrant III, DIMENSIONS: 1,2,3 AND MORE..., 1 The Real Number Line can only go:, •, , Left-right, , •, , So any position needs just one number., , 2 Cartesian coordinates can go:, •, , Left-right, and, , •, , Up-down, , •, , So any position needs two numbers, , 3 3 Dimensions, • Left-right,, •, , Up-down, and, , •, , Forward-backward, , •, , So any point can be located with (x,y,z) coordinates., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.1.115, , 29
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Production & Manufacturing, Turner - CNC Turning, , Related Theory for Exercise 4.2.116 & 4.2.117, , Preparation of part programming, Objectives : At the end of this exercise you shall be able to, • explain part programming preparation, • identify the G code and M codes., Introduction, , -, , Part programming comprises of collection of data,, arrangement of information in a standard format and, calculation of tool path, the data relates to dimensions of, feature, direction of cutting , tool required, sequencing,, and familiarity with NC system codes., , Decimal point should be not be allowed e.g. x = 7.875, will be represented as X07875 in a five system i.e., the last three digits are used for the decimal part of, the number. Some machines allow omission of leading, zeros, hence the same can be represented as X7875., , -, , It is recommended that dimensions should be, expressed in mm., , -, , All angular dimensions should be expressed as a, decimal fraction of a revolution., , -, , In absolute system, all dimensions should be positive., , -, , In incremental system the '+','-'sign represent the, direction of motion., , Preparation of part programming, 1 Block numbers / sequence number (N words), Each block of the program has a sequence number which, is used to identify the sequence of a block of data in it, which in ascending numerical order. When the part, program is read from the tape, each sequence number, is displayed on the panel of NC machine tool, as long as, that block commands are performed. This enables the, operators to know which sequence of block is being, performed practically by the tool. It consists of a character, 'N' followed by a three digit number raising from '0' to, '999'., 2 Preparatory Function (G-words), The preparatory function is used to initiate the control, commands, typically involve a cutter motion i.e. It, prepares the MCU to be ready to perform a specific, operation and interpret, the data which follows the way of, this function. It is represented by the character 'G' followed, by a two digit number i.e.'00 to 99'.These codes are, explained and listed separately., 3 Dimension words (X, Y & Z words), These dimension word are also known as 'co-ordinates'., Which give the position of the tool motion .These words, can be of two types:, a) Linear dimension words, -, , X, Y, Z for primary or main motion., , -, , U, V, W for secondary motion parallel to, X, Y, Z axes respectively., , -, , p, q, r for another third type motion parallel to X,Y,Z, axes respectively., , b) Angular Dimension Words, -, , a, b, c, for angular motion around X, Y, Z axes, respectively., , -, , I, J, K in case of thread cutting is for position of arc, centre; thread lead parallel to X, Y, Z axes., , These words are represented by an alphabet representing, the axes followed by five or six digits depending upon the, input resolution given. The following points may be noted, while calculating the number:, 30, , 4 Feed Rate Word(F - word), It is used to program the proper feed rate, to be given in, mm/min or mm/rev as determined by the prior 'G' code, selection G94 and G95 respectively. This word is, applicable to straight line or contouring machines, ,because in PTP systems a constant feed rate is used in, moving from point to point., It is represented by "F" followed by three digit number, e.g.F100 represents a feed rate of 100 mm/min., 5 Spindle speed / cutting speed word (S - word), It specifies the cutting speed of the process or the rpm of, spindle. It is also represented by 'S' followed by the three, digit number .If the speed is given in meter per min. then, the speed is converted in rpm rounded to two digit, accuracy, e.g. S-800 represents the 800 rpm of spindle., 6 Tool selection word (T - word), It consists of "T" followed by max five digits in the coded, number. Different numbers are used for each cutting tool., When the "t" numbers read from the tape ,the appropriate, tool is automatically selected by ATC(Automatic tool, changer).Hence this word is used only for machines with, ATC or programmable tool turret .e.g. T01,T02,T03, ………….. represents the tool selection word. Also,, sometimes T-word used for representing a tool offset, number corresponding to X Y and Z directions. With the, help of two additional digits, given after a decimal point, .(In HMT T-70,9 pairs of tools offset can be stored)., 7 Miscellaneous words (M-words), It consists of character M followed by two digit number, representing an auxiliary function such as turning ON/, OFF spindle ,coolant ON/OFF or rewinding the tape, .These functions do not relate two dimensional movement, of the machine. This is more explained in next topic., , Copyright @ NIMI Not to be Republished
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8 End of Block (EOB), , G70, , 00, , Finishing cycle, , It identifies the end of instruction block., , G71, , 00, , Multiple, turning, cycle, (Stock removal in turning), , G72, , 00, , Multiple, facing, cycle, (Stock removal in facing), , G73, , 00, , Pattern repeating cycle, , G74, , 00, , Peck drilling cycle, , G75, , 00, , Grooving cycle, , G76, , 00, , Multiple threading cycle, , G90, , 01, , Single turning cycle, , G92, , 01, , Single threading cycle, , G94, , 01, , Single facing cycle, , G96, , 02, , Constant surface speed, , *G97, , 02, , Constant RPM, , G98, , 05, , Feed per minute, , *G99, , 05, , Feed per revolution, , G and M codes (G-codes), This is the preparatory function word, consists of the, address character G followed by a two digit code number,, known as G-code. This comes after the sequence number, word and a Tab Code. There are two types of G codes, modal and non-modal. Modal codes remain active until, cancelled by a contradictory and code of same class .e.g., G70 is a modal code which defines that the dimensional, units are metric. It will remain active until cancelled by, G-71,which tells that the dimensional units are in inches, now. Non-modal G codes are active only in the block in, which they are programmed.G04 is non-modal code., List of G codes, G codes are instructions describing machine tool, movement. A G code quite often requires other, information such as feed rate or axes coordinates The, FANUC standard has a large selection of G codes, all of, which may not be available on all the machines. There, are three G code system: A, B and C. System A is the, most commonly used. Following is the list of some, common G codes of system A:, Code, , Group, , *G00, , 01, , Rapid traverse, , G01, , 01, , Linear interpolation, , G02, , 01, , CW circular interpolation, , G03, , 01, , CCW circular interpolation, , G04, , 00, , Dwell time, , G10, , 00, , Offset setting by program, , G20, , 06, , Inch data input, , G21, , 06, , mm data input, , G27, , 00, , Reference point (Home), return check, , G28, , 00, , Reference point (Home) return, , G30, , 00, , Return, to, second, reference point(Home), , G32, , 01, , Thread cutting, , G34, , 01, , Variable lead thread cutting, , G40, , 07, , G41, , 07, , G42, , 07, , G50, , 00, , G54-G59, , 14, , Description, , Tool nose radius, compensation cancel, Tool, nose, radius, compensation left, Tool nose radius, compensation right, Work coordinate change /, maximum spindle speed, setting, Work piece coordinate, system (G54 is default), , When the power is turned ‘ON’ or ‘Reset button’ is, pressed, the ‘G’ codes with * mark become active., List of M codes, The list given below is a typical representative list .All of, these may not be available on all the machines. On the, other hand, some machine may use some extra code, also. Note that most of the m codes, except a few such, as M00, M01, M02, M03, M04, M05, M06, M08, M09,, M19, M30, M98 and M99,are machine specific. Refer to, the specific machine manual for the list of available M, codes and their functions. M codes are defined and, implemented by the machine tool builder. The control, manufactured defines only G codes which are same on, all the machines with the same control., M00, , Program stop, , M01, , Optional stop, , M02, , End of program execution, , M03, , Spindle forward(CW , as viewed towards, the tail-stock), , M04, , Spindle reverse (C CW , as viewed, towards the tail-stock), , M05, , Spindle stop, , M06, , Auto tool change V (not needed on recent, controls), , M08, , Coolant ON, , M09, , Coolant OFF, , M10, , Chuck open (for machines with automatic, chuck), , M11, , Chuck close, , M13, , Spindle forward and coolant ON /sub-spindle, on, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.2.116 & 4.2.117, , 31
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M14, , Spindle reverse and coolant ON/sub OFF, , Example, , M19, , Spindle orientation, , O1203;, , M25, , Quill extend, , N1;, , M26, , Quill retract, , G28 U 0.0 W 0.0;, , M29, , DNC mode, , G50 S 1200 T 0300;, , M30, , Program reset and rewind, , M38, , Door open (for machines with automatic, door), , ________________ ;, ________________;, , M39, , Door close, , M40, , Parts catcher extend, , M41, , Parts catcher retract, , M43, , Swarf conveyor forward, , M44, , Swarf conveyor reverse, , M45, , Swarf conveyor stop, , M48, , Lock feed and speed at 100%, , M49, , Cancel M48 (default), , M52, , Threading pull out angle=90° (default), , M53, , Cancel M52, , M56, , Internal chucking, , M57, , External chucking, , M62, , Auxiliary output-1 on, , M63, , Auxiliary output-2 on, , M64, , Auxiliary output-1 off, , M65, , Auxiliary output-2 off, , M66, , Wait for input -1, , M67, , Wait for input-2, , M68, , Turret indexing (tool changes) onLy at, home position, , M69, , Turret indexing anywhere, , M70, , Mirror in X on, , M76, , Wait for input -1 to go low, , M77, , Wait for input -2 to go low, , M80, , Mirror in X off, , M98, , Subprogram call, , If the Decimal point is eliminated. The system read in, microns., , M99, , Return to the calling program, , X 50, , = 0.05mm, , Part program, , X 500, , = 0.5mm, , A set of commands given to the NC for machine motion, is called a program. A program is composed of number, of Blocks. Part program is use to specify the machining, process for the cutting tools., , X 5000 = 5.0mm, , Partprogram, , ________________ ;, M01;, N2;, G28 U 0.0 W 0.0;, G50 S 1200 T 0200;, ________________ ;, ________________ ;, , Part program, , ________________ ;, M01;, M30;, Decimal point input, Decimal point is used to input the units like Distance,, Time, and Angle ., X 25.0 is use for input the distance value . X25.0 equal to, 25mm or 25 inch., G04 X1.0 is used to input the dwell time value.X1.0 is, equal to one second., A45 is used for input the angle value.A90 is equal to 45°, The following are the same meaning, in the case of, decimal point., X20., X20.0, X20.00, , All are same meaning of, movement of X 20 mm, , X20.000, , Decimal point can be input for the following addresses., X, Z, U, W, A, B, C, I, J, K, P, R, Q, F., Note:, 1 micron=0.001mm, 1 mm=1000 microns, , 32, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.2.116 & 4.2.117
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1 inch=25.4mm, , Example, , 1 sec=1000 millisec, , N010 G00 Z50 M05(Spindle stops and rapidly moves up), , Structure or format of a part program, , Table common word addresses used in word address, format, , The complete part program for a given component, consists of a beginning code of %.A part program consists, of large number of blocks each representing an operation, to be carried out in the machining of the part. The words, in each block are usually given in the following order., -, , Sequence number(N-word), , -, , Preparatory word(G-word), , -, , Coordinates (X-,Y-,Z- words for linear axes; A-, B-, Cwords for rotational axes), , -, , Feed rate (F-word), , -, , Spindle speed(S-word), %, O3642, , Blocks, , (Program start), (Program number), , N010 ----------------------------------------N100 M02; (Program end), , -, , Tool selection(T-word), , -, , Miscellaneous command (M-word), , -, , End -of-block(EOB symbol), , The structure of part program used in Fanuc controller is, given below., Program number, Each of the program that is stored in the controller, memory requires an identification. It is used while running, and editing of the programs directly from the control, console. This identification is specified in terms of a, program number with ‘O’ word address. The number can, be a maximum of four digits., Sequence number (N-word), Each block in a part program always starts with a block, number, which is used as identification of the block. It is, programmed with a ‘N’ word address., Coordinate function, The coordinate values are specified using the word, address such as X, Y, Z, U, V, W, I, J, K, etc. All these, word address are normally signed along with decimal, point depending upon the resolution available in the, machine tool., Comments, Parentheses are used to add comments in the program, to clarify the individual function that are used to add, comments in the program .When the controller, encounters the opening parenthesis. It ignores all the, information till it reaches the closing parenthesis., , Address, , Function, , N, , Sequence number to identify, a block., , G, , Preparatory word that, prepares the controller for, instruction given in the block., , X, Y, Z, linear, , Coordinate data for three, axes., , U, V, W, , Coordinate data for, incremental moves in turning, in the X,Y and Z directions, respectively., , A, B, C, , Coordinate data for three, rotational axes X, Y and Z., , R, , Radius of arc, used in, circular interpolation., , I, J, K., , Coordinate values of arc, centre, corresponding to X, Y, and Z-axes respectively., , F, , Feed rate per minute or, revolution in either inches or, millimeters., , S, , Spindle rotation speed., , T, , Tool selection, used for, machine tools with automatic, tool changer or turrets., , D, , Tool diameter word used for, offsetting the tool., , P, , It is used to store cutter radius, data in offset register., It defines first contour block, number in canned cycles., , Q, , It defines last contour block, number in canned cycles., , M, , Miscellaneous function., , M01 - Optional stop, This function is same as ‘M00’, But it will stop only when, Optional stop button in the Machine panel is ‘ON’. Then, cycle is started to continue by pressing Cycle Start Button., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.2.116 & 4.2.117, , 33
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M02 - Programme end, , 2. G00 Z-----------;, , The code is inserted at the end of the program. The, machine stops permanently. Spindle rotation, Feed of, axis and coolant discharge all stops. The system is reset, by pressing Reset button in the machine panel and new, cycle is started by pressing Cycle start., , 3. G00 X------ Z----;, G00 - code used for the following operations, 1 Machining start, Making the tool approach the work piece., , M03 - Spindle ON clockwise, , 2 During machining, , By programming ‘M03’ the spindle is enabled to run in, the clockwise direction., , Moving the tool to next command position when, it is not in conduct with the work piece., , M04 - Spindle ON counter clockwise, , 3 Machine end, , By programming M04 the spindle is enabled to run in the, counter clockwise direction., M05 - Spindle stop, By programming ‘M05’ the spindle rotation is stopped., , Separating the tool from the work piece., G01 - Linear interpolation (straight cutting), , M08 - Coolant ON, , The cutter moves at specified feed rate. The feed rate is, specified by address 'F' in the program., , By programming ‘M08’ coolant motor switches ‘ON’., , Format, , M09 - Coolant OFF, , 1 G01 X------- F-----;, , By programming ‘M09’ coolant motor switches ‘OFF’., , Application, , M30 - Program end & rewind, , a Facing, , When CNC reads the code ‘M30’ the main program End, and Rewind . That is the CNC control returns the cursor, to the starting line of the program., , b, , G - Codes (preparatory functions), , Application, , G codes take active part in part program execution and, are programmed by letter G followed by two digits., , a. Straight turning, , Grooving etc., , 2 G01, , Z-----F-------;, , b. Drilling etc, , G codes once programmed, remains active until another., G code of the same group is programmed, after which, the previous one gets cancelled, are said to be modal., , 3 G01 X-----Z------F------;, , G codes which remains active only in the block in which, it is programmed, is said to be Blockwise active (or) one, shot G code., , a. Taper turning, b. Chamfering, Where ‘F’ is the cutting feedrate specified in mm/Rev., , G00 - Rapid traverse, The Tool moves at a rapid (fast) traverse rate with linear, interpolation. The rapid traverse rate depends upon the, machine type (for example maximum speed in a two, wheeler is 80-120 Km/hr depends on type of make)., This can be used in air movement like positioning,, relieving, non contact with work piece., Format, , Function F, The feed rate is used to move the tool from one point to, another point with constant feedrate. Feed is normally is, given mm/rev. or mm/min. The rapid traverse rate and, feed rate both are controlled by feed override switches in, the machine panel., Example, F, , 1. G00 X ---------;, 34, , Application, , Four digits number following, the address F, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.2.116 & 4.2.117
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G01 X 50.0 Z -50.0 F0.1; X -axis & Z - axis move with, feed 0.1mm/Rev., Circular interpolation (Fig.1), G02-Circular interpolation clockwise direction, G03-Circular interpolation Anti clockwise direction, , Example, G04 U 1.0 (Dwell of 1.0 second), Note, Decimal point is not available in ‘P’, Ex. Dwell of 2.5 seconds., G04 U 2.5, G04 X 2.5, G04 P 2500, G28 - Zero Return (Home Position, First Reference, value), , Format, , G02⎫, , ⎬ X − − Z − − R − − F − −;, , G03⎭, , G02⎫, , ⎬, , G03⎭, , OR, , X − − Z − − R − − F − −;, , Where, XZ -, , End point of Arc, , IK, , -, , Distance between start point of arc to, center point of arc in X & Z axis, , R, , -, , Radius of the arc, , F, , -, , Feed, , Command I and K specify the distance from the start, point of arc to the center point of arc must be specified, incrementally even under Absolute mode and sign (+) or, (-) for Values I & K is determined by the direction., , It is an inherent position on a machine axis. Automatic, Reference Point Return is a function to return each axis, to this inherent position automatically., 1 G28 U0, 2 G28 W0, 3 G28 U0 W0, G30 - Second reference return, It is same as G28.But is to settled before First Reference, Value (G28). It is called Temporary Reference Value., 1 G30 U0, 2 G30 W0, 3 G30 U0 W0, G50 - Co-ordinate value setting & maximum, spindle speed setting, 1 G50 X---Z---;, Ex. G50 X 300.0 Z 150.0;, 2 G50 X---Z---S---;, , Example, G02 X 40.0 Z-5.0 R 5.0 F 0.1, , Ex. G50 X300.0 Z 150.0 S 3000, , G03 X 40.0 Z-5.0 R5.0 F 0.1, , G96-Constant Surface Speed Control, (Cutting Speed Specification), , Where, R=Radius, , The G96 is used with an "S"-Function., The G96 is used when the cutting speed is specified., , G04-Dwell, If a block with G04 is real during automatic operation, the, feed is stopped for the time followed U, X, P, and then, the next block will be executed., , When G96 command is used the spindle speed is, changed automatically, as the cutting diameter is, changed. That is for smaller work piece of its cutting, diameter, the spindle speed becomes higher., , Format, , Calculation for cutting speed, , G04 (U, X, P) time, , V=, , π DN, 1000, , = mtr/min, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.2.116 & 4.2.117, , 35
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Where, , the number on offset screen (WEAR), , V = cutting speed, D = Diameter of the work piece in ‘millimeter’, N = spindle speed in rpm, G97-Constant Surface Speed Control Cancel (Spindle, Speed Specification), The G97 is used when the spindle rotating speed is, specified., , 2 Tool Geometry offset, The distance from top of the tool fixed on turret at machine, zero point to the work piece zero point is input as tool, geometry offset with this the CNC recognizes the position, of work piece zero point. Input the offset amount to the, same number as the number on offset screen, (Geometry)., , Ex. G97 S300 M03., With this spindle rotates at 300 rpm., For the following should use G97 always, a. Threading, b. Tapping, c. Drilling etc, Tool geometry offset (Fig.3), , Tool function (Fig.2), , This offset amount is not need to be cancelled after every tool use because the next input of tool geometry offset cancels former offset automatically., Tool wear offset, , Address: T, A four digits number address T Specifies the tool number, and tool offset number., Format, Example : T01 01, Tool Number, The left most two digits specify the number of tool., Offset Number, The right most two digits specify the number of tool offset., , The tool wear offset is used to modify the finished work, piece dimension in order to keep them within their, tolerances. The programmed path is shifted by the offset, amount parallel to X and Z axes. The offset amount is, input to "TOOL OFFSET /WEAR"., When the control reads T0101 and executes, the tool is, shifted by amount which is input in the tool wear offset, number (X-0.600, Z0.300)., After the machining the tool is returned near the starting, point and if T0100 (Tool wear offset cancel) is executed,, it returns to the starting point before offset. The same, movement is executed for other tools, only to assign tool, wear offset numbers which are required on the, programming and the amount to be offset should be, decided by the operator., Procedure for setting work coordinate system (Fig.4), Step 1, , Make sure that the component is securely, clamped., , Step 2, , Now bring one of the tool near the face of the, job., , Step 3, , I. Select MDI mode., II. Press PROGRAM button., , Step 4, , Enter S500, , 1 Wear offset, , Step 5, , The tool is moved adding the wear amount to part program. Input the offset amount to the same number as, , Select handle/jog mode and select the, appropriate feed., , Step 6, , Rotate the spindle in CW or CCW depending, on the type of the tool., , Types of Offsets, There are two types offsets:, , 36, , 1, , Wear offset, , 2, , Geometrical offset, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.2.116 & 4.2.117
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Step 7, , Light facing out be taken up to the center., , Step 8, , After the finish cut, move the tool back in x only., do not disturb Z-axis., , Step 9, , Now switch off the spindle., , Step 10 Press MENU offset. The wear geometrical, and work shift are displayed on CRT., Step 11 Now, press GEOM soft key and position the, cursor using cursor movement buttons to be, required offset number corresponding to the, tool used., Step 12 Press measure(m) key and press Z. Enter, Zero(MZ0)., Step 13 Now rotate the spindle in appropriate direction, and machine on OD, Step 14 Do not move X., Step 15 Take Z away from the job., Step 16 Stop the spindle., Step 17 Press MENU OFFSET PB., Step 18 Press 'GEOM' soft key., Step 19 Position the cursor to the required tool offset, number., Step 20 Press M….X…., Step 21 Input "The OD dimension measured. The XThe X-offset for the said tool is set., , All the travel commands for tool are mean their coordinate value from the work piece zero point (X0, Z0)., Position, , X, , Z, , 1, , 30.0, , 0.0, , 2, , 30.0, , - 10.0, , 3, , 40.0, , - 10.0, , 4, , 40.0, , - 25.0, , 5, , 50.0, , - 25.0, , 6, , 50.0, , - 45.0, , In the above figure, points 1 to 6 can be specified as, follows in absolute dimension programming., Incremental method (Fig.6), In this system, tool move from the previous point. In the, incremental programming the address "U" (diametrical), for "X" axis and the address "W" for "Z" axis are used to, distinguish incremental program from the absolute, program., The incremental command should have the direction (+/, -) and distance from currently specified point to next, command point., , Step 22 Repeat the procedure for all tools., Step 23 After taking offset, select MDI and issue S0., Programming method, In CNC for programming in Lathe, Absolute Command, and Incremental Command are available., Absolute method (Fig.5), In absolute dimensions programming, all the points of, the tool is coming from the datum point (or) zero point. In, CNC Lathe machines "X" and "Z" is the absolute input., The "X" means diameter of work piece and the "Z" means, distance from the finished end surface of work piece., , Example, In the Fig.6 the points, 1 to 6 can be specified as follows, in incremental dimension programming., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.2.116 & 4.2.117, , 37
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Position, , U, , W, , 1, , 30.0, , 0.0, , 2, , 0.0, , -10.0, , 3, , 10.0, , 0.0, , 4, , 0.0, , -15.0, , 5, , 10.0, , 0.0, , 6, , 0.0, , -20.0, , The tool path for finish cutting of a profile can be easily, derived by offsetting the nose radius. However, at the, beginning and end of inclined path, it is necessary to make, calculation based on simple trigonometry for the offset, point from the original contour. By using the cutter, compensation, the need for all complex calculations will, be eliminated. The programming for the finishing cutting, will be the direct path of the actual contour to be machined., (Fig.7), , – Give in the program (finish turning and boring). G41, (Tool Left) or G42 (Tool Right), The position of tool, viewing along the traveling direction and G40 (Tool, Nose Radius Compensation Cancel). (Fig.9), , – Input nose radius of tool to R in geometry offset., – Input the imaginal nose position to T in geometry offset., (Figs 10&11), , However, even after compensating the nose radius, the, point of contact between the tool nose and the work piece, will still be along the nose radius periphery which will be, changing depending upon the orientation of the tool with, respect to the cut surface. For example, the tool will leave, a small amount of metal along the inclined surface, when, the tool nose radius compensation is not active. For this, purpose, the turning centre controllers will provide the, necessary correction., If the correction is active, then the controller automatically, compensates and removes the unwanted material., However, in order for the correction to be active, the, controller will have to know the correct orientation of the, nose radius with respect to the machining surface. For, this purpose, nose radius direction is included in the, tool-offset registers., Tool nose radius compensation (Fig.8), , The following data's must be specified to carry out, automatic tool nose radius compensation, to obtain, required profile exactly., 38, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.2.116 & 4.2.117
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Part programming, Objectives : At the end of this lesson you shall be able to, • define the part programming, • list the APT programming sequence., Part programming, Definition wise "The part program is a sequence of, instructions which describe the work which has to be done, on a part, in the form required by a computer under the, control of an NC computer program"., Actually, part programming for NC production consists, of the collection of all data required to produce the part,, the calculation of the tool path etc. in a standard format,, which is in the form acceptable to its MCU or in other, words, it is the task of preparing a program sheet. All, data is fed into the NC system using a standardized, perforated or punched tape. Hence, the methods of part, programming can be of two types depending upon the, two techniques employed to produce a punched tape:, , translation of APT program; automatically generate the, absolute locations of paths for repetitive jobs, with the, help of a program., Procedure for developing manual part programme, The part programming requires an NC programmer to, consider some fundamental elements before the actual, programming steps of a part takes place. The elements, to be considered are as follows:, -, , Type of dimensioning system, , -, , Axis designation, , -, , NC words, , -, , Standard G and M codes, , -, , Manual part programming, , -, , Tape programming format, , -, , Computer aided part programming, , -, , Machine tool zero point setting, , Manual part programming, , Automatically programmed tools (APT), , In manual part programming, the data required for, machining, is written in a standard format known as, program manuscripts. Each horizontal line in a manuscript, represents a "block" of information., , Introduction, , Computer aided part programming, , Computer Aided Part Programming (CAPP) offer solution, to these type of complex programmes. It makes use of, repeated patterns of events which occur often on most of, the engineering components., , If the component requires a great deal of machining such, as in case of milling machines or contouring application,, calculation of cutter paths requires more calculations and, sometimes if a machining centre is used then selecting, different tool for drilling, tapping, boring and milling makes, all this part programming more tedious and time, consuming. More mistakes are also likely to occur. Thus,, we use a general purpose computer as an add, to reduce, labour involved in part programming. Also one of the, high level language such as APT (Automatically, Programmed Tools), ADAPT, SPLIT, 2CL, AUTO STOP, is used for writing a computer programme, which has, English like statements. A translator known as 'compiler', program is used to translate it in a form acceptable to, MCU., , With the advent of programming languages the job of, part programmer has reduced to:, , The work load of a part programmer is greately reduced,, because he has to do only following things:, , Different types of languages available for NC programing, are:, , a. Define the work part geometry by defining it in the, form line segments, circles, arcs etc., , APT, , b. If there is any repetition work such as drilling a number, of equal size and equal speed holes, then only defining, the dimensions of single hole., c. Specifying the operation sequence and the relative, position of repetitive job as in case of (b) with other, locations., , i. Define the geometry of work piece., ii. Specify the sequence of operations and tool path., The job of computer in CAPP consists of the following, steps, a. Input translation, b. Arithmetic calculation, c. Cutter offset computation, d Post processor, Programming languages, , APT is an acronym for Automatically Programmed Tools., It is the oldest and largest Computer Aided Programming, Language is developed by MIT. It is used for 5 axis control, of the 'tool' in three dimensional space. The tool can be a, drafting pencil, a point spray nozzle or even a cutting flame, torch., , This language is nowadays used for positioning systems, as well as will perform the mathematical calculations, 39, Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.2.116 & 4.2.117, , A computer aided programming method would do the, , Copyright @ NIMI Not to be Republished
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required for complex continuous path surface, applications., , -, , General information used to identify the part such, as PART NO, diameter of the cutter tool with, CUTTER/ .0975. These type of information is, required by post processor for calculation and, identifying purpose, coming under miscellaneous, information. NO POST, CLRPRNT, INTOL and, OUTTOL are other statements coming under this, category., , -, , Geometrical statements that define the geometry, of the tool movements with reference to work part., The starting of these statements is from defining, points by POINT statement. These all are almost, self-explanatory., , -, , Movement statements directing the sequence of, movement of tool for following a particular path., , -, , Auxilliary statement for setting speed, feed and tool, change etc., , ADAPT, It is an 'Adaptation of APT. It is a smaller version of APT, used on small computer. It is very mach suitable for 2½, axis control., AUTOMAP, Another subset of APT used for Numerical control, programming., EXAPT, Extended subset of APT using same instruction with, additional boring and turning data also. Sometimes having, facility to automatically calculate feeds and speeds., PROMPT, Interactive language mainly designed for lathes,, machining centres and flame cutters etc., The APT language, , d In some cases, the computer produces the computed, tool positions., e The final computer output after post processing is, given on magnetic tape or punched card., f, , The APT language is the NC language. It is also used as, the computer program which performs the calculations, to generate cutter positions based on APT statements., These statements are given as under:, i, , c The program either typed with keyboard on computer, or punched on cards or tape., , Geometry Statements / Definition statements (Define, the geometric elements of the work piece)., , ii Motion statements/movement statements (Define the, path taken by the cutting tool)., iii Post processor statements (Define the feeds and, speeds and to actuate other features of the machine)., iv Auxiliary Statements/Miscellaneous statements, (Define the part, tool tolerance etc). It is a 3-D system, that can be used to control up to five axes. This can, be used to control a variety of different machining, operations., APT programming sequence, There are approximately 400 words in APT vocabulary., The operations of developing a programme in APT are, followed in a sequence as follows:, , This magnetic tape or punched cards are fed into, Reader Unit, of machine to start machining., , The syntax rules for APT are very near to FORTRAN, language. It uses alphabets from A, B….YZ and numerals, 0, 1, 2, 3….8, 9. Special symbols used are: '/' used, sometimes for separating a single statements into two, parts ',' (comma) for separating different entities., '()' used for nested definition , Arithmetic operators are, '+' (add), '-' (subtract), '*' (multiply). '/' (division), '**' for, exponentiation. The symbols used for defining geometric, elements are:, -, , POINT, , -, , LINE, , -, , CIRCLE, , -, , PLANE, , -, , CENTER, , -, , RADIUS, , Parametric subroutines, Consider a component as shown in Fig 1, which has a, repetition feature namely square recess., , a Labelling the part. The part on the drawing is divided, into some basic geometric elements like lines, planes, and circles. Different elements are given different, labels and names. These elements are also needed, to be specified by their Cartesian co-ordinates., b Prepare the program manuscript. The programme in, APT is then transferred on manuscript paper; the four, type of instructions are written in a program:, 40, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.2.116 & 4.2.117
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Writing a programme for such a component would involve, making a cycle of some moves which can be referred to, as a "routine" for producing just one recess., , Fig 5 (c) Nesting of two subroutines., , "A subroutine is a portion of a programme, complete in, itself, which is stored in computer after programming, once. It is called with required data when required again, in a program". It is usually placed at the end of main, programme. Consider another example in Fig 2., , The table given below shows the difference between, canned cycle, loops and subroutines:, S.no, , A group of 5 holes occur in same geometric pattern. A, simple solution may be giving a D0-loop, but making, 'subroutine' will simply further the programming by placing, the single pattern in 'Subroutine', even if the holes at, location 1 are of different size than at 2., The major difference between canned cycles and, subroutines is that canned cycles are more of fixed type, and they cater for easy programming of machine features, that are often required, hence are more suitable for, general situations. But if sometimes a part requires a, pattern, that is required a no. of times on a particular, component, then a subroutine is the best solution. The, parametric subroutine is useful for turning, roughing outs,, thread cutting, keyway milling, drilling etc. Where a, sequence of motions is evolved. A few of them are given, in Fig 3 below:, Fig 3 (a) Turning subroutine, , Canned cycle, , Loops, , Subroutine, , 1, , Consist of some These are,, very common, repeating, (general) moves some moves, of different m/cs on a, coded., component, for a fixed, no. of times, , These are,, some moves, (operations)on, a component, for a variable, number of, times., , 2, , They don’t allow They allow to, optimisation of, change only, program in their the no. of, times, movements, fixed for operation.operations are, to be repeated., , They allow to, make their, own cycles, with different, parametric, dimensions at, different, locations i.e., user defined, carried cycles., , Nesting, The best way of writing an efficient part programme is to, place one or more loops in a subroutine i.e. repeating, some pattern at a fixed relative position within a subroutine program. This is known as "Nesting" of subroutines., This is explained with the help of Fig 3 and Fig 4., Normally the machine movements (operations) are written, in a subroutine without dimensions and while calling the, subroutine, the X, Y, Z etc. Parameters are passed simply., The general format for writing a subroutine is:, , Fig 4 (b) Milling subroutine, , 1 Subroutine, 2 Program information, 3 End of subroutine, Defining a subroutine, a The subroutine is not defined by a subroutine number, but is simply added with a sequence number following the main program., b All blocks in a subroutine are numbered from 'N001', onwards as if independent program., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.2.116 & 4.2.117, , 41
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Again some G - codes or M-codes are to be assigned, for:, i, , Jump to a subroutine location (Call a sub) by a code, e.g. G25, M98, G37., , N004, , Y - 02000, , At location (2), , N005, , X + 02000, , At location (3), , N006, , Y + 02000, , At location (4), , ii Start of subroutine., , N007 G80, , Cancel cycle, , iii End of subroutine e.g. G26, M99, G39., , N008 G00 X+05000, Y-01000, , Move to next relative, position B, , N009 M99, , Return back to main, prog., , L code is used to describe how many times a, subroutine is to be repeated., For our reference purpose, we will use M98,, M99 for respective coding of Begin, calling and, End of subroutine., Ex: Make use of subroutines for making part, programme of part shown in Fig 6., The thickness of plate is 5 mm. R-plane may be assumed, at 2 mm above plate surface. Z-0 at plate surface., , Main programme, N001 G00 G71 G80 G90, , Metric mode cancel, , G80 G90, , any previous cycle., Set absolute mode, , N002 S3500 F105 M06, , Set speed feed,, replace, tool and start spindle, , T1 M03, N003 G00 X02000, Y02000 M08, , Set position to ‘A’, , N004 P009 M98, , Call the subroutine of, drilling 5 holes, at, program location ‘P009’, , N006 G90 G80 Z00000, M09, , Absolute mode, cancel, cycle coolant off, , N007 G00 X00000, Y00000 M05, , Rapid to (0,0) spindle, stop, , N008 M30, , End of programme, , : 009, , Start of subrouting, , N001 G91, , Set incremental mode, , N002 G81 Z00700 R-00200 Drill hole at that very, location i.e.centre, N003 X-01000 Y+01000, 42, , Drill hole at location (1), , Explanation: (main programme), N001 & N002 : Setting feed, speed & Tool., N003, , : Locate tool above position 'A'., , N004, , : Call the subroutine for "drilling final, holes and locating drill at a distance, of 50 mm"., , N005, , : Call subroutine for two times for at, 70mm (i.e. at location 50 mm apart), and 120 mm (i.e. at, location 50 mm + 50 mm apart), , N006, , : Cancel cycle, , N007, , : Retract tool, , N008, , : End, , (Subroutine), N001, , : Incremental mode, , N002, , : Drill here itself because drill located, at centre of pattern., Z - depth = (Plate thickness + chip, clearance), = 5 mm + 0.3 dia of drill (6mm), = 5 + 0.3 x 6 = 5 + 2 = 7 mm (appx), R = -2 mm (given), , N003, , : Drill by moving on path (1) i.e., X ← X - 10, Y ← Y + 10, , N004, , : Drill hole following path (2), i.e., X←same, Y←Y - 20, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.2.116 & 4.2.117
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N005, , N006, , : Drill hole following path (3), X ← X + 20, Y = same, : Drill hole following path (4), i.e., X = same, Y←Y + 20, , N007, , : Cancel cycle don't drill more, , N008, , : Locate drill at 50 mm apart on x-axis, and 10 mm below Ylast position, i.e., X ←X + 50, , There are four components a,b,c,&d, 1. ‘a’ has two diameter ø1 and ø2, 2. ‘b’has ø2 portion increased in length, 3. ‘c’ has ø1 portion increased in diameter, 4. ‘d’ has ø2 portion eliminated, Mirror image, It reverses simply the sign + ve or - ve of an axis direction, as in Fig 9, , Y ← Y - 10, N009, , : Return, , MACROS, Macros are another type of subroutines which are given, an identify and stored within memory or macrofile used, for machining a complete component. A macro may have, fixed dimensions or it may have parametric variables., This is also sometimes referred to as only 'Parametric, subroutines'. These are very useful when programming, a family of parts that have same shape but vary in size as, shown in Fig 8, , T, , h, , e, , r, , Calling the centre line of this part as X0, Y0 the pattern is, machined. Then mirror imaging along X-axis by calling, subroutine and then mirroring both components along, Y-axis to get final shapes., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.2.116 & 4.2.117, , 43
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Production & Manufacturing, Turner - CNC Turning, , Related Theory for Exercise 4.2.118, , Operational modes, Objectives : At the end of this lesson you shall be able to, • state the various operational modes, • state the work piece zero point., • state the tool zero point, • explain the machine reference point, • list the various types of offset, • prepare the part program for facing, plain turning, step turning, chamfering turning, radius turning and, drilling., Operational modes, Single block mode, This mode will function when the mode switch is set in, AUTO mode only. If we switch on the single block switch, and push the cycle start button, then the single block in, the programme only will be executed. For the execution, of the next block then again cycle start button should be, pressed. If the single block switch is in off position, then, the program will be executed continuously., Auto mode, For this mode, the mode switch is set in AUTO mode. In, this mode the program will be executed continuously one, block after another block., , by moving the slides so that the cutting tool is placed in, the desired position in relation to the work pieces. This is, known as floating zero point., Machine zero point or machine datum (M), It is a fixed point on a machine specified by the, manufacturer. This point is the zero point for the, coordinate system of the machine controller. In turning, centre, the machine zero point is generally at the centre, of the spindle nose face as shown in Fig 1. In machining, centres, it is either fixed at centre of the table or a point, along the edge of the traverse range., , In this mode if we press the cycle start button, the current, program in the CRT panel will be executed., Manual mode: MDI mode, MDI mode means manual data input. With this mode,, we can input the program command manually and, execute the program., Jog mode, Jog mode is used for moving the turret in X and Z direction, .After selecting jog mode if we press 'X+' axis button, the, turret will move in 'X+' direction. In the same manner we, can move in the ‘Z’ direction also., Incremental jog mode, This mode is used to move the turret in micron level. By, pressing the axis button, in this mode, we can move the, button in 0.001, 0.01, 0.1, 1 mm range., , Work piece zero point (W), This point determines the work piece coordinate system, in relation to the machine zero point as shown in Fig 2., This point is chosen by the part programmer and input to, the machine controller. The position of this point may be, chosen in such a way that the dimensions of the work, piece drawing can be easily converted into coordinate, values. For turned components, it is placed along the, spindle axis in line with the right or left end face of the, work piece. It is also known as program zero point., , Edit mode, This mode is used to edit the program. In this mode edit, key should be in 'ON' position, to input a program., Zero points and reference points, Zero point, In CNC machines, tool movements are controlled by, coordinate systems. The origin of the co-ordinate system, is considered as zero point. In some of the CNC, machines, the zero point may be located at a fixed place, and cannot be changed. This is known as fixed zero point., Some other machines, a zero point may be established, 44, , Copyright @ NIMI Not to be Republished
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Tool zero point (T), , Operation devices, , When machining a work piece, the tool must be controlled, in precise relationship with the work piece along the When, machining a work piece, the tool must be controlled in, precise relationship with the work piece along the, machining path. This requires a point in the tool turret be, taken as reference point, which is known as tool zero, point., , Edit alphanumeric keys, , At the tools in the tool turret have different shapes and, sizes, the Offset distance between the tool zero point and, work piece zero point is measured and entered in to the, computer. This known as tool offset setting., Machine reference point (R), Machine reference point is also known as home position, as shown in Fig 3. It is used for calibrating the measuring, system of the sides and tool movements. It is determined, by the manufactures., , Used to edit the part program, tool offsets, work offsets, etc.., Feed rate override switch, Enables manual overriding of the programmed feed rate, during part machining. Can be varied between 0% and, 120% of the programmed feed rate, in steps of 10%., Rapid rate override switch, Enables manual overriding of the rapid traverse rate, during rapid motions. Can be varied between 0% and, 100% of the programmed feed rate, in steps if 25%., Spindle speed override switch, Enables manual overriding of the spindle speed during, part machining., Feed hold, Stops the motion of all axes temporarily during machining., Cycle start, Machine rest, Stops all functions being executed, like spindle rotation,, axes motion, etc., Emergency stop, , The value of the machine reference coordinates (XMR,, ZMR) is fixed and cannot be changed by the user. The, positioning of the reference point is accurately, predetermined in every transverse axis by the trip dogs, and limit switches., Programming details (Fig 4), -------------, , This line indicates the tool moves at rapid, feed (G00), , -------------, , This line indicates the tool moves at, linear interpolation (G01), , Used when the machine is to be halted suddenly, like in, case of tool breakage. Pressing it shuts down all systems, of the machine except the console-axes drives, spindle, drive, coolant pump, hydraulic power pack etc., Single block ON/OFF, When OFF, execution of the part program is automatic, and continuous. When ON, part program is executed, block-wise. In block-wise execution the cycle start button, must be pressed to execute each block., Coolant ON/OFF Controls the coolant., Data input/output, Used to transfer data between the machine and an, external device like a PC. Data that can be transferred is, part program, PLC data, tool offset and work offset., Chip conveyor forward backward Moves the chip, conveyor., Dry run, Sets the Dry run mode ON or OFF. The Dry run mode is, used to check the part program by executing it without, actually cutting a part. During this mode commanded, feedrate in the part program is not effective, and the axes, moves at a fixed Dry run feed rate. Dry run feed rate is, typically 1000 mm/min to 5000mm/min., Machine lock and auxiliary function lock, Sets the Machine lock mode ON or OFF. The machine, lock mode is used to check the part program by executing, it without any axes motions and miscellaneous functions, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.2.118, , 45
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like tool change, spindle rotation, etc. The screen display, appears as during normal execution., , Ks=1800 N/mm² and a machine efficiency factor=0.75, are used., , Operational modes, − Auto mode, , P =, , − Edit mode, , kw, , 25, , III) Approximate value for surface finish, , − MDI mode (Manual data input), − Jog mode, , 2, , − MPG mode (manual pulse generation) data, − Input/output mode, − Zero return mode, I) Selection of tools, speed feed & depth of cut, D = work piece diameter, , mm, , V = cutting speed, , m/min, , S = Feed, , mm/r, , N = RPM, , r/min, , A = Depth of cut, , mm, , N = Efficiency, , for example 0.75, , Ks = Specific cutting force, , N/mm2, , V = Metal removal rate, , cm3/min, , P = power required, , kW, , R = nose radius, , mm, , K = Constant, , for example 1.4, , Rt = Profile depth, , μm, , Ra = Surface finish, , μm, , RPM, , n=, , Cutting speed, , v=, , Profile depth R t = k, , s 1000, 8r, , The constant k is dependant on two factors, the work, piece material and how well the cutting edge profile is, reproduced on the work piece. In normal machine steel, k=1.4, Surface finish Ra = Rt/3.5., Surface Ra = s2.50/R, IV) Effect of nose radius and feed rate on the surface, finish requirements, The table below gives the recommended maximum, values of feed rate for finishing normal steels, when, turning materials which give rise to edge build-up, the, cutting speed must be sufficiently, high to avoid such, tendencies, if possible When turning highly abrasive, materials, the feed rates should be reduced by about 20%, .To convert Ra to CLA multiply by 40., Nose radius, mm, , v . 1000, πD, , π .D.n, 1000, , =r/min, , 0.2, , m/min, , V = V.S.A cm3/min, , Power required, , P =, , v . s . A. k s, , kW, , 6 0 0 0η, , II) Approximate value for power required, The above formula for power is exact but the specific, cutting force ks is included. The ks-value is hard to set, because it is dependent on many factors. Such as work, piece materials, chip breaker, cutting rake, feed setting, angle chip thickness., A simplified formula for approximate power required is, shown below, Based on the most common type of, application-medium rough to rough turning of normal, steel, with a light-cutting edge-a specific cutting force., , 0.4, , 0.8, , 1.2, , 1.6, , 2.4, , Feed rate, mm/rev, , Ra value, , 0.6, , 0.05, , 0.07, , 0.10, , 0.12, , 0.14, , 0.17, , 1.6, , 0.08, , 0.12, , 0.16, , 0.20, , 0.23, , 0.29, , 3.2, , 0.12, , 0.26, , 0.23, , 0.29, , 0.33, , 0.40, , 0.23, , 0.33, , 0.40, , 0.47, , 0.57, , 0.40, , 0.49, , 0.57, , 0.69, , 6.3, 8.0, , Metal removal rate, , 46, , v .s .A., , A large nose radius will usually result in a better surface, finish, provided that the cutting edge is sufficiently sharp, and that the larger nose radius does not give rise to, vibrations. It is recommended that the depth of cut for, finishing should be more than the nose radius of the, chosen insert. Fillet, etc on the component often restrict, the choice of nose radius on finishing., V) Cutting speed-wear life, Providing the machining conditions are good i.e. stability, of the work piece and tool, it is possible to increase the, wear life of the insert., To achieve longer wear life, the cutting speed must be, reduced. Multiply the recommended cutting speeds by, the following factors, The cutting speeds given in this guide are for 30 min.wear, life. If higher surface speeds are required that wear life, will decrease., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.2.118
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Approx. wear life, in minutes, * 15, * 30, 45, , Factor, 1.25 x V, 1.00 x V, 0.89 x V, , VI) Edge condition factors (Fig.5), -, , Fixed conditions, , -, , Material specification, , -, , Amount of material to be removed, , -, , Component dimension, , -, , Component shape, , -, , Hardness, , -, , Surface condition, , -, , Operation, , -, , Finish requirement, , -, , Type of machine, , -, , Condition of machine, , -, , Power available, , -, , Chucking or clamping method, , Once the fixed conditions have been considered, the, tooling and data parameters can be variable conditions, -, , Select carbide grade, , -, , Select radius, , -, , Select insert shape, , -, , Select insert size, , -, , Select insert rake, , -, , Select tool size, , -, , Select tool-holder shank size, , -, , Select tool-holder style, , Now the cutting speed, depth of cut and the feed over, revolution can be selected., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.2.118, , 47
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Production & Manufacturing, Turner - CNC Turning, , Related Theory for Exercise 4.2.119, , Types of offsets, Objective: At the end of this lesson you shall be able to, • list the types of offsets used in CNC machine, • trace the tool path from the given program., Types of offsets, , The procedure for geometrical offset is given below, , There are three types of offsets used in CNC machine, operation., , Clamp the job in the chuck of the machine, Set the tool in the required order in the machine turret, , They are:, , Select the jog mode or MPG mode, , i, , Select the first tool and touch the face of the job, , Work offset (or) zero offset, , Check with a piece of paper whether the contact of tool, with the job is proper, , ii Geometrical offset, iii Wear offset, Work offset (or) zero offset., Every manufacturer fix a reference point on the spindle, of the machine according to the design of manufacturing., The tool will take the command and move with reference, to this machine reference point., To make the tool to move with reference to the job, work, offset or zero offset has to be taken., Procedure for taking work offset, Clamp the job in the chuck of the machine., Set the tool in the required order set in the machine turret., Set the jog mode or the tool and touch the face of the job., With the use of a paper check the proper contact of tool, with the face., Now select the work co-ordinate system from G54 to G59., Enter the z value in the selected work co-ordinate system, Now touch the diameter with the same tool., Check the contact of the tool with the job using a paper., Now enter the diameter of the job in the tool contact point, in the x value in the selected work co-ordinate system., This particular work co-ordinate system should be, mentioned in the part program., Geometrical offset, The tools used in CNC machine are of different geometry., The length of the tools vary accordingly., , Now take the geometrical offset page and enter under, the tool number the command MZ 0 (zero), This command will clear any previous values and will, measure the current tools tool offset in Z axis, Now touch the tool to a know diameter on the component, Again in the tool-geometry page enter the command MX, (The value of the diameter) for example if the diameter is, 50mm then MX50, Follow the same procedure for the remaining tools, enter the MZ and MX commands for various tools in the, under respective tool number., Wear offset, Because of long running the tool tip may wear out and, the dimension of the job may increase or decrease from, the original programmed dimension, To recitify this defect wear offset is used, Procedure for entering wear offset, If the programmed size is X40.49 and the machine size, is 40.44 in this 0.04 mm is reduced due to tool wear., To rectify this take the tool offset number of the worn out, tool., In that tools wear offset number enter the value U0.04., In the inner diameter defects instead of positive value, put U-0.04 in the wear offset number., Tool offset number and wear offset number are same., , Even if the work offset is taken for a tool it will not suit the, other tools, So for every tool offset is taken and entered in tool offset, value in work co-ordinate system, Because of this every tool will take the work zero point as, origin, 48, , Copyright @ NIMI Not to be Republished
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Production & Manufacturing, Turner - CNC Turning, , Related Theory for Exercise 4.2.121 &122, , Cutting parameters, cutting speed and feed, depth of cut,CSM, tool wear, tool, life, Objectives: At the end of this lesson you shall be able to, • differentiate between cutting speed and feed, • state select the recommended cutting speed for different materials from the chart, • state the factors governing the cutting speed, • state the factors governing feed & learn about interpolation., Cutting speed (Fig 1), , When more material is to be removed in lesser time, a, higher cutting speed is needed. This makes the spindle, to run faster but the life of the tool will be reduced due to, more heat being developed. The recommended cutting, speeds are given in a chart. As far as possible the, recommended cutting speeds are to be chosen from the, chart and the spindle speed calcualted before performing, the operation. (Fig 2) correct cutting speed will provide, higher tool life under normal working condition., , Cutting speed is the speed at which the cutting edge, passes over the material, and it is expressed in metres, per minute. When a work of a diameter ‘d’ is turned in, one revolution the length of the portion of work in contact, with the tool is πxdxn. This is converted into metres and, expressed in a formula form as, V, , .D .N, 1000, , metre /min., , Where V = cutting speed in m/min, π = 3.14, D = diameter of the work in mm, N = RPM, , Cutting speed 120m/min, , 60, , length of metal passing, cutting tool in 1 revolution, , calculated r.p.m. of spindle, , ____ 78.56mm, , 1528, , ____ 157.12mm, , 756, , ___ 235.68mm, , 509.3, , Copyright @ NIMI Not to be Republished
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Example, Find out the rpm of a spindle of a 50mm bar to cut at, 25m/minute ; V =, 1000× 25, 3.14 x 50, , =, , 500, 3.14, , π × DN, 1000, , ; N=, , 1000 V, π ×D, , = 159 r.p.m, , Factors governing the cutting speed, Finish required, depth of cut, tool geometry, properties and rigidity of the cutting tool and its mounting, properties of the workpiece material, rigidity of the workpiece, type of cutting fluid used, rigidity of the machine tool, Feed (Fig 3), The feed of the tool is the distance it moves along the, work for each revolution of the work, and it is expressed, in mm/rev., , Cutting speeds and feeds for H.S.S. tools, TABLE 1, , Factors governing feed, Tool geometry, surface finish required on the work, , Material being, turned, , Feed, mm/rev, , Cutting speed, m/min, , rigidity of the tool, , Aluminium, , coolant used, , Brass (alpha)-ductile 0.2-1.00, , 50-80, , Rate of metal removal, , Brass (free cutting), , 0.2-1.5, , 70-100, , The volume of metal removal is the volume of chip that is, removed from the work in one minute, and is found by, multiplying the cutting speed, feed rate and the depth of, cut., , Bronze(phosphor), , 0.2-1.00, , 35-70, , Cast iron(grey), , 0.15-0.7, , 25-40, , Copper, , 0.2-1.00, , 35-70, , For super HSS tools the feeds would remain, the same, but cutting speeds could be, increased by 15% to 20%., , Steel(mild), , 0.2-1.00, , 35-80, , 0.15-0.7, , 30-35, , A lower speed range is suitable for heavy, rough, cuts., , Steel (alloy high, tensile), , 0.08-0.3, , 5-10, , Thermosetting, plastics, , 0.2-1.00, , 35-50, , A higher speed range is suitable for light,, finishing cuts., The feed is selected to suit the finish required, and the rate of metal removal, When carbide tools are used, 3 to 4 times, higher cutting speed than that of the H.S.S., tools may be chosen., The recommended cutting speed and feed rate, for H.S.S. tools are listed on Table 1., , 0.2-1.00, , 70-100, , Steel, (medium-carbon), , Depth of cut, The depth of cut is the difference between machined and, un machined surface., If, , D1 = initial diameter, D2 = Final diameter, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.2.121 & 122, , 61
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Depth of cut, , D1− D2, , =, , 2, , The relationship between limiting spindle speed and, the constant cutting speed, when working with Constant cutting speed Mode, the, spindle speed increases as the tool moves towards the, axis. The spindle speed is calculated using the equation., πDN, , V(m et/m in) , , 1000, , of the, where D diameter, d, N = RPM of the spindle, , As per the above equation,at a specific cutting speed, (say V=250m/mm) when the dia is 30mm the spindle, speed shall be 2652 rpm. when the diameter is reduced, to 20mm the spindle speed would be 3978 and if the, diameter reduces to 1mm the spindle speed would go, up to 79577 rpm, and at certain diameter spindle speed, may go beyond the machine’s capacity. similarly when, to tool go near the axis point, the spindle speed RPM, would be theoritically infinity since the diameter at axis, is (D=0), , N, , 1000V, .D, , , , 1000V, .0, , , , However, the CNC machine has certain maximum, spindle speed permissible, which should be specified in, , our programme, and this is known as limiting spindle, speed. Once programmed, when the spindle reaches this, limiting value of speed, the controlled clamps it and the, rest of the operations are carried out at a constant speed,, limiting spindle speed. This will ensure that any possible, damage due to variationof spindle speed, is prevented., As an example, when we desire to carry out, at constant, cutting speed of 250m/min at 3000 RPM, the programme, as per Fanuc shall be, G96 S250, G92 S3000, What is the benefit of fixing Limiting spindle speed in the, programme?, If a component is rigidly fixed in the chuck and the, component is cylindrical, spindle maximum. speed is set, as limiting spindle speed. If the part is not circular or, cylindrical, and is held in a fixture, not balanced, the, centrifugal forces may cause the part to fly off, or it may, spoil the fixture itself, if the Limiting speed is not, programmed., At the axis of the part, in fact, the RPM would theoretically, be infinity (D is zero). The machine however has a certain, maximum spindle RPM, so in the CNC program we need, to specify what this maximum speed., , Interpolation, Objectives: At the end of this lesson you shall be able to, • define the interpolation, • state the purpose of interpolation, • list the type of interpolation., Interpolation, , iii) Radius and centre of a circle, , As the co - ordinates of points on the profile of the job, vary continuously, it is necessary to define the path of, small segment., , iv) Gradient angle for a line, , This tedious work is done by the computer by means of, “ interpolator”., , Types of interpolations, Interpolations are classified as, i) Linear interpolation, , Definition, , ii) Circular interpolation, , The methods by which control system calculate the, intermediate points and the speed of the motor is known, as interpolation., , iii) Helical interpolation, , The parameters supplied may be, i) Radius, ii) Start and end point of a curve, , 62, , iv) Parabolic interpolation, v) Logarithmic interpolation, vi) Exponential interpolation of these the linear and, circulate interpolators are commonly employed., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.2.121 & 122
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Linear interpolation, In this interpolation, the interpolated points lie on the, straight line joining a pair of given points. (Fig 1a), This is done in two or three dimensions., , Advantages of circular interpolation are, Better surface finish, The fast of linear interpolator is to supply velocity, commands to several axes simultaneously in pps (pulses, per second) (Fig 1b), By changing the frequency of the pulses, the feed can be, controlled., The linear interpolator consists of Digital Differential, Analyser (DDA) integrators one for each axis of motion, hence each integrator functions separately one for X- axis, and the other for Y - axis. (Fig 2a), Circular interpolation, In circular interpolation, the interpolated points lie on a, specific circle between a pair of fixed points., In most cases, the circular interpolation is limited to one, quadrant in the machine tool system. (Fig 2b), The input data should consists of the distances between, the initial point and the centre of the circle., Two Digital Differential Analysers (DDA) are required for, circular interpolation., , Greater accuracy, Less total machining time, Lower working costs., Circular interpolation, The circular interpolation,, •, , Code G02 (clockwise), , •, , Code G03 (anti - clockwise), , A circular interpolation permits the traversing of the tool, with a defined speed along a circular path from the present, Start-points to the programmed destionation point., Apart from the destination points co-ordinates, the control, unit here also needs statements about the sense of, rotation and the centre of the circle. The centre is entered, with I,J and K with incremental dimensions with the centre, points as origin., The following assignment applies:, , • I for the x - axis, • J for the Y - axis, • K for the Z - axis, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.2.121 & 122, , 63
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Principle of position control, Objectives: At the end of this lesson you shall be able to, • explain the principle of position control in a CNC machine, • explain the terms pulse and pulse frequency, • state the difference between closed loop and open loop control, • state feedback/measuring systems used in CNC machines., It has already been stated that the slides of CNC, machine are driven by servo motors., The feed rate and position to be reached by the slide, (tool) are indicated to the control by means of a, programme line such as the one given below., G91 G71 G01 x 60 F30, The meaning of the above instruction is that the tool, should travel a distance of 60 min along the x axis at a, feed rate of 30 mm/min from its existing positon. In other, words the tool should travel a distance of 60 mm in 2, minutes., , Therefore, this system is not providing any check to see, that the commanded position has actually been achieved., There is no feed back of information to the control also., These system are not good where extremely accurate, positioning is required., , Principle of position control, The above instruction requires that the feed motor should, rotate at a predetermined r.p.m for a period of 2 minutes:, and to achieve this, the feed motor should receive the, required quantity of electrical energy. This calls for, regulation of the input current to the motor and basically, what the computer in the CNC machine does for position, control is nothing but regulating the current input to the, feed motor., The control computer after receiving a travel instruction, perform certain calculations and arrive at the number of, pulsed to be sent out in the given time in order to achieve, the required travel. ( It may be noted that the basic output, from any computer is an intermittent supply of low strength, electric current called pulse or signal) Usually one pulse, sent out by the control causes a tool travel of 0.001, and, Hence, in the above example to achieve a travel of 60mm, in 2 minutes, the control after reading the above program, line would send 60,000 pulses(60#0.001) in 2 minutes., Pulse frequency, This term refers to number of pulses sent per second in, the above case the pulse frequency is 500/S (60,000/, 120). The pulse frequency , it may be noted, is, proportionate to the feed rate., The pulse output by the computer being of low strength, and intermitted in nature, is not directly send to the drive, motor, Instead the intermitted current is converted to an, equivalent continuous form, and is also strengthened, suitably., , Closed loop control (Fig 2 ), Closed loop control (Fig 2) is a term which is used very, often when we talk about CNC machines. This term, signifies, that the control system has provisions to ensure, that the tool reaches the desired position, at the correct, feed rate, even if some errors creep in due to unforeseen, reasons., For instance in the previous example 60,000 pulses sent, in 2 minutes by the control should cause a tool travel of, 60mm at 30 mm/min, but even if the control sends these, may pulses it cannot be ensured that the tool has really, travelled exactly 60 mm., A closed loop control has a device called encoder and, this can continuously ascertain the distance acutally travelled by the tool and then monitor the same, in the form, of feedback signals to the control. The control studies, this feedback information and takes corrective action in, case any error is detected in the tool position/feed rate., , The feed motor thus receives a regulated supply of, continuous current for a specified time interval, and hence,, ensures a tool travel as instructed by the programme, Open loop control system (Fig 1), In an open loop control system (Fig 1) in which there is, no arrangement for detecting or comparing the actual, position of the cutting tool on the job with the commanded, value., Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.2.121 & 122, , Copyright @ NIMI Not to be Republished, , 65
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Tool life, Objectives: At the end of this lesson you shall be able to, • state the relationship between cutting speed and tool life, • explain tool life index equation, • determine the maximum cutting speed for a given tool life., Relationship between cutting speed and tool life, , Vt n = C, , Duration of correct cutting to the anticipated surface finish, between grinding is termed as tool life. In metal cutting,, increase in cutting speed increases power requirement., Therefore, the mechanical energy is converted into heat, energy at the cutting edge. Much of the heat is absorbed, by the cutting tool with corresponding increase in, temperature, resulting in softening of the cutting tool,, which is the reason for inefficient cutting action. The, effect of this reduction in tool life is largely present in high, carbon steels. Hence, they have to be operated at lower, cutting speeds., , where V = cutting speed in m/min., , Cutting materials such as high speed steel, metallic, carbides and oxides can operate at much higher, temperatures without reduction in hardness., Fig 1 shows graphically the relationship between cutting, speed and tool life curve in logarithmic form. A small, increase in cutting speed from A to B causes large, reduction in tool life from C to D, while small reduction in, cutting speed causes a large increase in tool life., Thus when the machine gearbox does not give the, required cutting speed, it is better to use the next lower, speed rather than the higher speed., Tool life index, The relationship between tool life and cutting speed can, be represented by the following equation for most practical, purposes., , t = tool life in minutes, n and C are constants for a given set of conditions., The value of n lies between 0.1 to 0.2 and typical values, are given in the following table., The following example is shown to determine the maximum cutting speed for a given tool life., , Table, Tool life index, Material and conditions, , 66, , Tool material, , n, , 3 1/2% nickel steel, , Cemented carbide, , 0.2, , 3 1/2% nickel steel (roughing), , Highspeed steel, , 3 1/2% nickel steel (finishing), , Highspeed steel, , 0.14, 0.125, , High carbon, high chromium die steel, , Cemented carbide, , High carbon steel, , Highspeed steel, , Medium carbon steel, , High-peed steel, , Mild steel, , Highspeed steel, , Cast iron, , Cemented carbide, , Copyright @ NIMI Not to be Republished, , 0.15, 0.2, 0.15, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.2.121 & 122
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Example, The life of a lathe tool is 8 hours when operating at a, cutting speed of 40 m/min. Given that Vtn = C, find the, highest cutting speed that will give a tool life of 16 hours., The value of n is 0.125., (i) Determine the value of Log C from initial conditions., C = Vt1 where, n, , V = 40 m/min., t1 = 480 min., , From the calculations, tool life is doubled by reduction of, cutting speed by 8.3 percent, or reduction of tool life can, be calculated for an increase of 8.3 percent in cutting, speed. Hence, it is always important to select a lower, cutting speed, rather than a higher cutting speed, if the, machine controls do not give optimum value., Tool life calculations are useful in achieving optimum, operating conditions of cutting tools. Modern cutting tool, materials are singularly resistant to softening under the, heat of normal cutting and usually fail in two ways as, shown in Fig 2., , n = 0.125, Log C = Log V + n Log t1, = log40 + (0.125 Log480), =1.6021 + (0.125 x 2.681), =1.6021 + 0.3351, =1.9372, (ii) Determine Vmax for revised conditions, C, Vmax, =, n, t2, Where t2, Log Vmax, , = 960 min. (16x60), = Log C – n Log t2, = 1.9372 – (0.125 x log960), = 1.9372 – (0.125 x 2.9823), = 1.9372 – 0.3728, = 1.5644 antilog 0.5644, , a) Wear of clearance face, b) Crater of rake face, The above conditions can be corrected only by regrinding, immediately for effective metal cutting., , Vmax is 36.68 m/min., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.2.121 & 122, , 67
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Production & Manufacturing, Related Theory for Exercise 4.3.123-124, Turner - Tool setting and Data Input, Cutting tool materials for Turning, Objectives: At the end of this lesson you shall be able to, • explain the properties of cutting tool, • state the types of tool material., Cutting tool materials and their properties, , -, , 1980: First engineered carbide substrate, (cobalt-enrichment), , -, , 1982: First SiAION ceramic, , -, , 1985: First PVD coated carbide, , -, , Mid 80's: Modern cermets (TiCN-based), , -, , Late 80's: SiC whisker reinforced Al2o3 ceramic, , -, , Early 90's: Advanced Sialons, , -, , Mid 90's: thin film diamond coated carbide, , The most important properties required by a cutting tool, material are,, , -, , Late 90's: PVD coated PCBN, , Toughness, , -, , 2000: Advanced pre-coat & post-coat treatments, , Ability to withstand the various cutting forces during, machining., , Cutting tool materials, , Tool materials are the subject of intense development. They, are the product of an evolvement that has taken place, almost entirely during the twentieth century, and especially, since the thirties. Machining which took one hundred, minutes in 1900, today takes less than one minute. It is, not an exaggeration to say that the evolvement of tool, materials has been one of the major contributing factors, that has helped to make the modern, efficient industrial, world., Today, there is a tool material to optimize every metal, cutting operation-one that will cut a certain work piece,, under certain conditions in the best way. Not only have, completely new materials appeared but high speed steel,, which was the major break through at the beginning of the, century, has been developed to machine several times, faster. It is however, the introduction and continuous, improvement of hard materials that have really improved, metal cutting during the recent decades., Cutting tool properties, , Hardness, Ability to retain hardness under severe working conditions., High resistance to wear, The material must withstand excessive wear even though, the relative hardness of the tool materials changes., Frictional coefficient, The frictional coefficient must remain low for minimum, wear and reasonable surface finish., Cost and easiness in fabrication, The cost and easiness of fabrication should have within, reasonable limits., Evolution of cutting tools, -, , 1910-1920: High speed steel, , -, , 1920's: Cemented carbide, , -, , 1950's: Cermets (Tic -based), , -, , 1960's: Alumina-based ceramic, , -, , 1970: CVD coated carbide, , 68, , Metal cutting environment (Fig.1), -, , Heat (thermal deformation), , -, , Pressure (deformation, fracture), , -, , Wear (pure abrasion, chemical wear, notching), , -, , Interrupted cuts (thermal & mechanical cycling), , Types of tool materials, The selection of proper tool materials depends on the type, of service to which the tool is subjected. The commonly, used cutting materials are:, Carbon steels, -, , It is basically high carbon steel with percentage of, carbon in the range of 0.8 to 1.5, , -, , It may only be used in manufacture of tools operating, at low cutting speed (12m/min)., , -, , They are comparatively cheap, easy to forge and simple, to harden., , -, , Disadvantage of carbon tool steel is their comparatively, low heat and wear resistance., , Copyright @ NIMI Not to be Republished
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High speed steel, -, , It is the general purpose metal for low and medium, cutting speeds owing to its superior hot hardness and, resistance to wear., , -, , HSS can operate at cutting speeds 2 to 3 times higher, than for carbon steels and retain its hardness up to, 900°C., , -, , Tungsten in HSS provides hot hardness and form, stability. Molybdenum maintains keenness of the, cutting edge. Cobalt makes the cutting tool more, wear resistant., , -, , They can with stand temperature up to 1200°C and, can be used at cutting speeds 4 times that of carbide, and up to 40 times that of HSS., , -, , To give them increased strength often ceramic with, metal bond know as cermets is used., , -, , Heat conductivity of ceramics being very low the tools, are generally used without coolant., , Cermets, Cermets -Ceramics and Metal, Characteristics of cermets, , Stellites, , -, , High Hardness, , -, , Stellites is the trade name of a non-ferrous cast alloy, composed of cobalt, chromium and tungsten., , -, , High Hot Hardness, , -, , The range of elements in these alloys is 40% to 48%, cobalt, 30% to 35%, chromium and tungsten., , -, , Resist oxidation, , -, , Low Friction, , -, , Stellites can be operated on steel at cutting speeds 2, times higher than for HSS., , -, , They are used for non metal cutting application such, as rubbers, plastics etc.,, , Carbides, -, , They are composed principally of carbon mixed with, other elements., , -, , The basic ingredient of most carbides is tungsten, carbide, which is extremely hard. Pure tungsten, powder, is mixed under high heat(1500°C) with pure, carbon in the ratio of 94% and 6% weight., , -, , The two types of carbides are the tungsten and titanium, and both are more wear resistant., , Advantage of cermets, -, , High efficiency, , -, , Long life, , -, , Large batch, , -, , Avoid Build Up Edge, , -, , Surface Finish Control, , -, , Cermets Have the properties of higher cutting speed, and wear resistance which enables hard part turning., , Coated carbides, -, , The coated carbide has substrate and coating layer, , -, , Substrate-for toughness having hard material and soft, material (cobalt + carbide), , -, , Coating -Layer of carbide (very hard), , -, , Perform well on all work material, , -, , Better impact strength to resist fracture, , -, , Allow good coating adhesion, , Ceramics, -, , The latest development in the metal cutting tool uses, aluminium oxide, generally referred to as ceramics., , -, , Compacting aluminium oxide powder in a mould at, about 280 kg/sq.cm or more makes ceramic tools. The, part is then sintered at 2200 °C. This method is known, as cold pressing., , -, , Ceramic tool material are made in the form of tips that, are to be clamped on metal shanks, , -, , The tools have low conductivity and extremely high, compressive strength, but they are quite brittle and, have a low bending strength., , Diamond, -, , The diamond is the hardest known material and can, be run at cutting speed about 50 times greater than, that of HSS tool and 5 to 6 times of tool life than, carbide., , -, , Diamond is incompressible, readily conducts heat and, has low coefficient of friction., , -, , Diamond are suitable for cutting very hard material, such as glass, non-ferrous materials, plastics etc.,, , -, , For poly crystalline diamond (PCD) the tool life is 30, times of carbide., , The following picture shows the comparison of the, various materials in terms of their properties. (Fig 2), Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.3.123 & 124, 69, , Copyright @ NIMI Not to be Republished
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The second letter specifies the relief angles (Fig.4)., , Tool inserts, Carbides and other harder tool materials are very costly., Moreover, they cannot be machined. So, only tool tips are, made for such materials using powder metallurgy, technique. In this method, the tool material is taken in a, powder form. It is mixed with a suitable binder (in powder, form) and compressed in the shape of an insert., , Symbol, , Relief Angle, , N, , 0°, , A, , 3°, , B, , 5°, , C, , 7°, , Inserts are available in various shapes such as triangle,, square, rectangle, pentagon, hexagon, octagon, diamond, shaped and circle. They cannot be resharpened, but they, have a number of cutting edges. (Fig 3), , P, , 11°, , D, , 15°, , E, , 20°, , Inserts are produced in various sizes and thicknesses., Smallest possible size is chosen to produce the desired, depth of cut. Thickness of an insert affects its strength., Hence, for a large depth of cut and feed, a thicker insert is, chosen., , F, , 25°, , G, , 30°, , ISO standard is commonly followed for specifying inserts., An example is CNMG120408. The first letter, C in this, case , indicates the shape of the insert. The common, types are:, Symbol, , Shape, , S, , Square, , T, , triangular, , H, , hexagonal, , O, , octagonal, , P, , pentagonal, , L, , rectangular, , R, , round, , A, B, K, , 70, , Significance of the fourth letter, The fourth letter describes the overall geometrical features, of the insert (refer table). For example, an insert may or, may not have a hole at the centre. The hole may be, cylindrical or cylindrical with single or double, countersink.The insert may or may not have a chip-breaker., The chip-breaker may be single-sided or double-sided.-, , parallelogram (nose angles, 85°, 82° and 55° respectively), , C, D, E, F, M, V, , W, , The third letter specifies tolerances on various dimensions, (Fig.4) (e.g., thickness) of the insert. The different tolerance, classes are A, F, C, H, E, G (absolute values) and J, K,, L,M,N,U (tolerance values depend on the diameter of the, inscribed circle of the insert), , Diamond shaped or rhombic, (nose angles 80°, 55°, 75°, 50°,, 86°, 35 ° respectively), Trigon (nose angle 80°), , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.3.123 & 124
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Symbol, , Hole, , Shape of Hole, , N, R, , Chip-Breaker, without, , without, , no hole, , single-sided, , F, , double -sided, , A, , cylindrical, , without, , M, , single-sided, , G, , double -sided, , W, , cylindrical, with 40o-60o, countersiink, , T, Q, , with, , without, single sided, , cylindrical, with 40°-60°, double, countersink, , without, , without, , H, , cylindrical, with 70°-90°, countersink, , C, , cylindrical, , without, , J, , with 70°-90°, double, countersink, , double-sided, , B, , X, , double-sided, , single-sided, , special shape, , Cutting edge condition (Fig.5a), , Cutting direction (Fig.5b), L for machining with left - rotated (CCW) spindle (M04),, R for machining with right - rotated (CW) spindle (M03), and N for both left-and right - rotated., The appropriate character designations are appended to, the right, after the radius specification., Tool holders for lathe, There is an ISO designation system for tool holders also,, to suit various types of inserts. The first five characters, describe insert clamping method, compatible insert shape,, insert holding style of the tool holder (side cutting edge, angle/end cutting edge angle and straight shank/offset, shank), clearance angle and cutting direction, respectively., Next four digits specify shank height and shank width in, mm (two digits for each). Tool length is specified next, by, a character code. The next and the last two digits specify, , F for sharp,, T for chamfered,, E for honed and, S for chamfered and honed., This information , however, is non-obligatory., ., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.3.123 & 124, , 71
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1st character, Insert holding, method, M=top clamp, and lock pin via, the bore, P = lock pin via the, bore only, C=top clamp only, , 2nd, , TABLE 1, ISO designation for lathe tool holders (Contd.), character, 3rd character, 4th character, , Insert shape, A-85°, parallelogram, B = 82°, parallelogram, C=80° diamond, , S=centre, screw lock only, , D=55° diamond, , X = other methods, , E = 75°, diamond, H = hexagon, K = 55°, parallelogram, L = rectangle, M = 86° diamond, O = octagon, P = pentagon, R = round, , S = square, T = triangle, V = 35°, W = 80°, trigon, , 72, , Tool holder, style, A = 0° side, cutting, shank, B = 15° side cutting, cutting straight shank, C = 0° end cutting, straight shank, D = 45° side cutting,, 45°end cutting,, straight shank, E = 30° side, cutting, straight shank, F = 0° end, cutting, offset shank, G = 0° side, cutting, offset shank, H = -17.5° side, cutting, offset shank, J = -3° side, cutting,offset shank, K=15° end cutting,, offset shank, L=5°sidecutting,5°, cutting, offset shank, M=40°side cutting, 50° end cutting,, straight shank, N=27°sidecutting,, straight shank, P=-27.5°side cutting,, offset shank, R=15°side diamond, cutting, offset shank, S = 45° side, cutting, offset shank, T=30°side cutting,, offset shank, U=3°endcutting,offset, shank, V=17.5°side cutting,, straight shank, W = 30° end cutting,, offset, shank, Y= 5° end cutting, offfsest, shank, , 5th character, , Insert relief, (clearance), N = 0°, , Hand, R = right -hand, striaght, , A = 3°, , L = left-hand, , B = 5°, , N - neutral, , C = 7°, , P = 11°, D = 15°, E = 20°, F = 25°, G = 30°, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.3.123 & 124
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cutting edge length in mm. Manufacturers, specific, codes may be appended in the end. (Figs 6 & 7), Insert clamping method (S), , Retained via central, screw, , Compatible insert shape (C), , 80° diamond, , Style of the tool holder body (L), , -5° side cutting, edge angle, 5° end, cutting edge angle, and offset shank, , angle and cutting edge length have the same, representation for tool holders as well as boring bars., For a boring bar, the cutting. If cutting is possible with, clockwise rotation (MO3) of the spindle. The example,, considered in the figure is S32u SSKCR12 type boring, bar. Manufacturer-specific information may be appended, in the end, after a gap. Separating dash (1) is also used, in place of gaps. Referring to Table 1 and Figs 8&9, the, description of S32U SKKCR12 is as follows:, Shank type (S), , Steel shank, , Clearance angle (C), , 7°, , Shank diameter (32), , f 32 mm, , Cutting direction (R), , Right-hand, , Tool length (U), , 350 mm, , Shank height (25), , 25 mm, , Insert clamping method, , Retained via central screw, , Shank width (25), , 25 mm, , Compatible insert shape (S) Square, , Tool length (M), , 150 mm, , Cutting edge length (12), , 12 mm, , Style of the boring bar, body (R), , -15 o end cutting edge, angle. offset shank., , Clearance angle (C), , 7o, , Cutting direction (R), , Right-rotated (CW spindle), , Cutting edge length (12), , 12 mm, , Manufacture specific information None, Boring bars for lathe (Figs 8&9), There is a similar ISO designation system for the internal, tool hodlders also (which are called boring bars). See, Fig.8 and Fig.9 for details. Refer to Table 1 also for shapes, not shown in these figures. In fact, tool length, clamping, method, compatible insert shape, body style, clearance, , Manufacturer - specific, information, , Copyright @ NIMI Not to be Republished, , None, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.3.123 & 124, , 73
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Production & Manufacturing, Turner - Tool setting and Data Input, , Related theory for Exercise 4.3.125, , Tool Geometry, Insert Type, Nomenclature of Inserts, Objectives: At the end of this lesson you shall be able to, • discuss the features of tool geometry, • identify various tool angles, • state what is a negative rake angle and its features, • learn various types of inserts, • understand nomendature of insert and ISO designation., Tool Geometry, , 1, , Approach angle, , The tool geometry of cutting tool is a complicated subject., It is very difficult to determine the scope of the tool face., The straight edged tool moving with a constant velocity un, the direction perpendicular to the work is known as tool, geometry. The cutting tool geometry deals mainly with, factors like approach angle,cutting angle, training angle,, clearance angles,rake angle . The following sketches, indicates various angles (tool geometry) relating to fFcinf, tool,rough turning tool,finish turning tool,parting tool,boring, tool. The advantages of negative rake is also explained., , 2, , Cutting angle, , 3, , Trailing angle, , The carbide turning tools generally used for various turning, operations are listed below., -, , Straight round nose, , -, , Right hand and left hand roughing tool, , -, , Facing tool, , -, , Right and left hand knife edge tool, , -, , Heavy duty roughing tool, , -, , Cranked round nose tool, , -, , Recessing tool, , -, , Parting tool, , -, , Screw cutting tool., , 4a, , Front clearance-primary, , 4b, , Front clearance-secondary, , 5a, , Side clearance-primary, , 5b, , Side clearance-secondary, , 6, , Top rake-negative, , 7, , Side rake, , These angles for various tools are shown in the figures., (IS 2163-1973 and 2163-1976), Generally the manufacturers of carbide tools maintain, these angles while manufacturing these tools. Hence it is, only needed to maintain these angles while re-sharpening., The illustrations are as indicated below., 1, , Facing tool (Fig 2), , The various cutting angles provided in these tools are as, follows. (Fig 1), , 2 Rough turning tool (Fig 3), , 74, , Copyright @ NIMI Not to be Republished
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3, , Finish turning tool (Fig 4), , Negative rake angle, 4 Parting off tool (Fig 5), , It is used to achieve the following advantages., -, , The cutting edge becomes stronger., , -, , It can withstand excessive compressive loads., , -, , The tool can be operated at higher cutting speeds., , -, , It decreases tool wear and increases the tool life., , -, , Heavier depth of cut can be given., , The limiting conditions for the applications of negative rake, turning tools are:, – the machine must have a wider range of high spindle, speeds, 5, , Boring tool (Fig 6), , – the machine and the tool-holding devices must be quite, rigid and must be free from vibrations since the, cemented carbide tip may chip off under vibrations, – provision must be there for quickly dissipating the higher, degree of heat generated during machining, – the power of the motor of the machine must be atleast, 10 to 15% higher than that provided on machines on, which positive rake tools are used under similar working, conditions., Tool inserts, , Negative rake is used in cemented carbide tip tool for rough, turning., The true rake angle is the resultant of front rake and side, rake angles. The top rake may be positive, zero or negative, as shown in Figure 7., Most of the cutting tools have positive rake angles. Turning, tools for brass have zero rake as the metal chips are short, and do not exert excessive cutting pressure on the tool, face while cutting. Zero rake increases the strength of the, tool and prevents the cutting edge from digging into the, work., , Carbides and other harder tool materials are very costly., Moreover, they cannot be machined. So, only tool tips are, made for such materials using powder metallurgy, technique. In this method, the tool material is taken in a, powder form. It is mixed with a suitable binder (in powder, form) and compressed in the shape of an insert., Inserts are available in various shapes such as triangle,, square, rectangle, pentagon, hexagon, octagon, diamond, shaped and circle. They cannot be resharpened, but they, have a number of cutting edges. (Fig 8), Inserts are produced in various sizes and thicknesses., Smallest possible size is chosen to produce the desired, depth of cut. Thickness of an insert affects its strength., Hence, for a large depth of cut and feed, a thicker insert is, chosen., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.3.125, , 75
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The second letter specifies the relief angles (Fig 9)., , ISO standard is commonly followed for specifying inserts., An example is CNMG120408. The first letter, C in this, case , indicates the shape of the insert. The common, types are:, , Symbol, , Relief Angle, , N, , 0°, , A, , 3°, , Symbol, , Shape, , B, , 5°, , S, , Square, , C, , 7°, , T, , triangular, , P, , 11°, , H, , hexagonal, , D, , 15°, , O, , octagonal, , E, , 20°, , P, , pentagonal, , F, , 25°, , L, , rectangular, , G, , 30°, , R, , round, , A, B, K, C, D, E, F, M, V, , W, , 76, , parallelogram (nose angles, 85°, 82° and 55° respectively), Diamond shaped or rhombic, (nose angles 80°, 55°, 75°,, 50°, 86°, 35 ° respectively), , The third letter specifies tolerances on various dimensions, (Fig.4) (e.g., thickness) of the insert. The different tolerance, classes are A, F, C, H, E, G (absolute values) and J, K, L,, M, N, U (tolerance values depend on the diameter of the, inscribed circle of the insert)., , Trigon (nose angle 80°), , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.3.125
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Production & Manufacturing, Turner - Tool setting and Data Input, , Related Theory for Exercise 4.3.126, , Describe tooling system for turning, Objectives: At the end of this lesson you shall be able to, • learn about the tooling system used in lathe understand the characteristics of tool material, • learn about the fixing of tool - tips., Tooling System, For ordinary lathe turning (SSSC) lathe the operator such, as sliding, surfacing, screw cutting and taper turning, operation, We use the standard element of the lathe itself, namely compound rest., , cartridges are available in different sizes to hold different, sizes to hold different inserts of multi-cutting edges., , The compound rest can hold only one tool at a fine, and was, replaced square tool post in which for tools can be held on, each face., Important Tooling System includes self chuck, fonjaw, chuck, collect chuck, faceplate chuck to hold the job., In older days high speed steel, hardened was used as a tol,, which was ground to required tool shape. But modern days, the tool holder are made out of medium carbon steel shank, with the tool brazed or filled in the form of topped tool. the, parts of a throw-away tip tool is shown in Fig 1, The tool-holder for holding throw-way tips are specially, designed. They are made to accommodate different shapes, of inserts. Othe rfeatures like different angles and chip, breakers are incorporated in the tool-holders. They are, made up of alloy steel., Parts of a throw-away tip tool-holder (Fig 1), , The parts of a throw-away tool-holder are as shown in, Fig 1 above. Different types of tool-holders are used for, holding different shapes of throw-away tips.(Fig 2), Tool-holders for internal machining (Fig 3 & 4), The cartidges (one of the parts of an internal tool-holder, of carbide is called the cartridge) are used for internal, boring work. It as used along with the standard bar. The, , Copyright @ NIMI Not to be Republished, , 77
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With light duty cartrudges minimum size of bore will be 32, mm (1.26”), and with medium duty cartridges the sizes will, be 45 mm (1.77”)., , Fig 5 indicates threading tool held on a square tool post,, used for threading a component., , The following are the points to be noted when using carbide, throw-away inserts for machining., •, , Select proper tool post., , •, , Select the correct size and shape of tool-holder to fix, the tool bit., , •, , Ensure the tool is set at the centre of the axis., , •, , Do not overhang the tool-holder., , •, , Use appropriate spped and feed while using the throwaway tips., , •, , Use copious supply of coolant while machining with, throw-away tips., , 78, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.3.126
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Production & Manufacturing, Turner - Tool setting and Data Input, , Related Theory for Exercise 4.3.127, , Setting work and tool offset, Objective: At the end of this lesson you shall be able to, • list the types of offsets used in CNC machine, • trace the tool path from the given program., Types of offsets, There are three types of offsets used in CNC machine, operation., They are:, i, , Work offset (or) zero offset, , ii Geometrical offset, iii Wear offset, work offset (or) zero offset., Every manufacturer fix a reference point on the spindle of, the machine according to the design of manufacturing., The tool will take the command and move with reference, to this machine reference point., To make the tool to move with reference to the job, work, offset or zero offset has to be taken., Procedure for taking work offset, Clamp the job in the chuck of the machine., Set the tool in the required order set in the machine turret., , Because of this every tool will take the work zero point as, origin, The procedure for geometrical offset is given below, Clamp the job in the chuck of the machine, Set the tool in the required order in the machine turret, Select the jog mode or MPG mode, Select the first tool and touch the face of the job, Check with a piece of paper whether the contact of tool, with the job is proper, Now take the geometrical offset page and enter under the, tool number the command MZ 0 (zero), This command will clear any previous values and will, measure the current tools tool offset in Z axis, Now touch the tool to a know diameter on the component, Again in the tool-gemetry page enter the command MX, (The value of the diamter) for example if the diameter is, 50mm then MX50, Follow the same procedure for the remaining tools, , Set the jog mode or the tool and touch the face of the job., , enter the MZ and MX commands for various tools in the, under respective tool number., , With the use of a paper check the proper contact of tool, with the face., , Wear offset, , Now select the work co-ordinate system from G54 to G59., Enter the z value in the selected work co-ordinate system, Now touch the diameter with the same tool., Check the contact of the tool with the job using a paper., Now enter the diameter of the job in the tool contact point, in the x value in the selected work co-ordinate system., This particular work co-ordinate system should be, mentioned in the part program., Geometrical offset, The tools used in CNC machine are of different geometry., The length of the tools vary accordingly., Even if the work offset is taken for a tool it will not suit the, other tools, , Because of long running the tool tip may wear out and the, dimension of the job may increase or decrease from the, original programmed dimension, To recitify this defect wear offset is used, Procedure for entering wear offset, If the programmed size is X40.49 and the machine size is, 40.44 in this 0.04 mm is reduced due to tool wear., To rectify this take the tool offset number of the worn out, tool., In that tools wear offset number enter the value U0.04., In the inner diameter defects instead of positive value put, U-0.04 in the wear offset number., Tool offset number and wear offset number are same.=, , So for every tool offset is taken and entered in tool offset, value in work co-ordinate system., , Copyright @ NIMI Not to be Republished, , 79
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Production & Manufacturing, Turner - Tool setting and Data Input, , Related Theory for Exercise 4.3.128, , Describe tooling system for CNC Turning centres, Objective: At the end of this lesson you shall be able to, • learn what are the elements of a tooling system in CNC, • understand the locking fixture and roleution knob, • learn the factors of selecting a tool holder., The Tooling System for a CNC machine includes, universal, quide change chuck, adopters for drilling, reaming and, tapping adjustable adopter floating holders,, non-reversible quick change tapping chuck, hydraulic, chuck., The fixture to hold the tool is to be designed based on the, turret head. A tool holder locking fixture is shown below at, Fig 1, , Tools can be convenients and quickly clamped to tool, handers, for which collet type chucks are used. The Fig 2, indicates CNC tool holder with ER collets., The collets have a shoot range and comes in different, sizes. A set of collets is shown in the Fig 2, Tool holders for machining cetre provide a standard spindle, nose taper (Fig 3) and size for insertion of tool holders. The, tool holder knob in the tool holder allows the locking. The, locking drawbar to pull the tool firmly into the spindle and, to released auomatically. The retention knob is either, flange type, threaded type or tapered size., , 80, , Selection of tool holder, The three factors that determine the selection of tool, holders for a job include flange type, spindle taper nunmber, and cutting tool to be used. In selection of an adapter, the, following must be considered, • Gauge distance, • Diameter of cutting tool shawk, • Adapter outside daimeter, , Copyright @ NIMI Not to be Republished
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Production & Manufacturing, Turner - Tool setting and Data Input, , Related Theory for Exercise 4.3.129, , Cutting tool material for CNC turning, Objective: At the end of this lesson you shall be able to, • identify the cutting tool material for CNC, • learn the characteristics of cutting tool making., Cutting tool for CNC, Though carbon steels, containing 0.9% C, 1% manganese,, duly hardened for 62 HRC used in older days, High speed, steel is invariably used for ordinary lathe turning. HSS also, used for tools like drill, reverse taps, dies etc;but had a, maximum cutting speed of 60m/min However for CNC, coated carbide or sintered carbide were used which had, high thermal conductivity., Presently Coated Carbide tools, using titanium nitride,, titanium carbide and Aluminium oxide with a thickness, upto 15 micron is used for increased tool life. Cubic boron, nitride (CBN) a hardest material is used for machining alloy, and tool steel. These tool bits are coated with thick layer, of poly crystaline boron nitride sintered onto a carbide, substrate under pressure and this can have as high as 310, metres/min of cutting speed., , tool life is estimated using formula V(T)n = C Where, V = cutting speed , m/min., T = Tool life in minutes, C = Cutting speed for tool life of 1 minute, n = Taylor exponent, Tool material, , Typical ‘n’ value, , HS steel, , 0.08 - 0.2, , Cast alloy, , 0.1 - 0.15, , carbide, , 0.2 - 0.5, , ceramic, , 0.5 - 0.7, , Diamond tools are for more specific application, replacing, (PCD), polycrystalline diamond. This tool can be used for, very high speed machining. Aluminium Alloys and, non-metallic material. This tool can go up to a high cutting, speed of 2000m/min., The tool life of a CNC tool is more important factor and the, , Copyright @ NIMI Not to be Republished, , 81
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Production & Manufacturing, Turner - Tool setting and Data Input, , Related Theory for Exercise 4.3.130, , ISO Nomenclature for Turning tool holder, boring tool holder, indexable, insert, Objective: At the end of this lesson you shall be able to, • understand ISO nomenclature for turning tool holder, • learn about boring tool holder, • learn about indexable inserts., Turning holders names follows an ISO nomenclature, standard If you are working on a CNC shop floor in the lathe,, knowing ISO nomenclature is a must. The name looks, complicated but actually it is very easy to interpret, , P, , C, , 1, , 2, , L, 3, , N, , L 25 25 M, , 4 5, , 6 7, , 8, , -, , 8 Holder length, , When selecting a holder there are in fact only 4 parameters, that you really need to understand to select the right holder, for your application. There are numbers marked as Nos., 2,3,4 and 9 respectively. The others are automatically, decided., , 9, , 2 Insert shape, 3 Holder style, , In the table below you have to use only your brain in, selecting the parameter, Where there is a brain symbol in, the rows., , 4 Insert clearance angle, 5 Hand of holder, , 82, , 7 shank width, 9 Insert cutting edge length., , 12, , 1 Insert clamping method, , Sl.No, , 6 Shank length, , Parameter, , Brain, , How is this decided, , 1, , Insert clamping method, , Selection based on cutting forces top clamping, is the most steady,screw clamping is the best., , 2, , Insert type, , Decided by the contour that you want to turn, , 3, , Holder style, , 4, , Insert clearance cycle, , Positive/negative based on applicaton, , 5, , Hand of holder, , Decided based whether you want to cut towards, the chuck or away from chuck and turret position, , 6, , Shank height, , Decided by machine, , 7, , Shank width, , 8, , Holder length, , Decision based on part Geometry, , 9, , Insert cutting edge length, , Decision based on depth of cut you want to use, , Copyright @ NIMI Not to be Republished
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Tool holders for lathe, There is an ISO designation system for tool holders also,, to suit various types of inserts. The first five characters, describe insert clamping method, compatible insert shape,, insert holding style of the tool holder (side cutting edge, angle/end cutting edge angle and straight shank/offset, shank), clearance angle and cutting direction, respectively., Next four digits specify shank height and shank width in, mm (two digits for each). Tool length is specified next, by, a character code. The next and the last two digits specify, cutting edge length in mm. Manufacturers, specific codes, may be appended in the end. (Figs 6 & 7), , angle and cutting edge length have the same, representation for tool holders as well as boring bars., For a boring bar, the cutting. If cutting is possible with, clockwise rotation (MO3) of the spindle. The example,, considered in the figure is S32u SSKCR12 type boring, bar. Manufacturer-specific information may be appended, in the end, after a gap. Separating dash (1) is also used in, place of gaps. Referring to Table 1 and Figs 8&9, the, description of S32U SKKCR12 is as follows:, Shank type (S), , Steel shank, , Shank diameter (32), , f 32 mm, , Tool length (U), , 350 mm, , Insert clamping method, , Retained via central screw, , Compatible insert shape (S) Square, Style of the boring bar, body (R), , -15o end cutting edge, angle. offset shank., , Clearance angle (C), , 7o, , Cutting direction (R), , Right-rotated (CW spindle), , Cutting edge length (12), , 12 mm, , Manufacturer-specific, information, , None, , Insert clamping method (S), , Retained via central, screw, , Compatible insert shape (C), , 80° diamond, , Style of the tool holder body (L), , -5° side cutting, edge angle, 5° end, cutting edge angle, and offset shank, , Clearance angle (C), , 7°, , Cutting direction (R), , Right-hand, , Shank height (25), , 25 mm, , Shank width (25), , 25 mm, , Tool length (M), , 150 mm, , Indexable Insert, , Cutting edge length (12), , 12 mm, , Inserts are very for machining various application. This, can be used either in lathe or in a milling machine. The, selective indexable insert commonly used are shown, below:, , Manufacturer specific information None, Boring bars for lathe (Figs 1&2), , 1 Boring insert, There is a similar ISO designation system for the internal, tool hodlders also (which are called boring bars). See Fig.1, This is mainly used for internal machining including boring, and Fig.2 for details. Refer to Table 1 also for shapes not, operation., shown in these figures. In fact, tool length, clamping, method, compatible insert shape, body style, clearance, Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.3.130, 83, , Copyright @ NIMI Not to be Republished
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2 Cut-off insert, , 4 Threading insert, , These type of inserts are used to parting or cutting purpose,, generally referred as cut-off inserts., , This type is mainly used for fine threading both in lathe, and in a milling machine., , 3 Grooving insert, This insert is mainly used when grooving is needed in a, component., , 84, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.3.130
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Production & Manufacturing, Turner - Tool setting and Data Input, , Related theory for Exercise 4.3.131, , Tool holders and inserts for radial grooving, face grooving, threading and, drilling, Objectives: At the end of this lesson you shall be able to, • understand the ISO designation of tool holders for CNC machine, • learn about various shapes of tool inserts, • learn about the type of clamping for tool holder, • understand the clearance angle and included angle of inserts., Tool holders, For CNC machine tool, we need special tool holders, and, the conventional holders used in ordinary lathe and other, machine tool may not fit. The tool holders for CNC, machines are specified under ISO designation holders. It, can be clamp type, screw type, locking pin via the bore, etc;, , The shape of the tool holder can be either straight shank, type or off-set shank type. Another classification of the, tool holder is Right hand (R), left hand (L) and neutral type, (N) The tool holders are so designed to suit the various, shapes of available inserts., The nomenclature and ISO designation of lathe tool holder, is shown in Table1., , ISO designation for lathe tool holders (Contd.), 1 character, , character, , 3rd character, , 4th character, , 5th character, , Insert holding, method, , Insert shape, , Tool holder, style, , Insert relief, (clearance), , Hand, , M=top clamp, and lock pin via, the bore, , A-85°, parallelogram, , A = 0° side, cutting striaght, shank, , N = 0°, , R = right -hand, , P = lock pin via the, bore only, , B = 82°, parallelogram, , B = 15° side cutting, cutting straight, shank, , A = 3°, , L = left-hand, , C=top clamp only, , C=80° diamond, , C = 0° end cutting, , B = 5°, straight shank, , N - neutral, , S=centre, screw lock only, , D=55° diamond, , D = 45° side cutting,, 45° end cutting,, straight shank, , C = 7°, , X = other methods, , E = 75°, diamond, , E = 30° side, cutting, straight, shank, , P = 11°, , H = hexagon, , F = 0° end, cutting, offset shank, , D = 15°, , K = 55°, parallelogram, , G = 0° side, cutting, offset shank, , E = 20°, , L = rectangle, , H = -17.5° side, cutting, offset shank, , F = 25°, , M = 86° diamond, , J = -3° side, cutting,offset shank, , G = 30°, , O = octagon, , K = 15° end, cutting, offset shank, , P = pentagon, , L = 5° side cutting, 5°end, cutting, offset shank, , st, , 2, , nd, , Copyright @ NIMI Not to be Republished, , 85
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The included angle of the tool inserts generally varies 55°, to 85°. The inserts can be rectangular pentagonal,, hexagonal, triangular, circular, diamond shape etc., There is a special tool holder used in CNC machines for, boring bars, Which is generally steel shank type, with a, length of 350 mm, retained through central screw, with, offset shank. The clearance angle for boring bar tool is, around 7°.The details of boring bar is shown in, Shank height (25), , 25 mm, , Shank width (25), , 25 mm, , Tool length (M), , 150 mm, , Cutting edge length (12), , 12 mm, , Manufacturer specific information None, , 86, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.3.131
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Production & Manufacturing, Related Theory for Exercise 4.4.132, Turner - Programming and Simulation, Preparation of Part programming, Objectives: At the end of this lesson you shall be able to, • define the part programming, • state the purpose of preparatory (G codes) & Miscellanious function (M codes), • develop the part programming., Part programming, , Type of dimensioning, , Definition wise “the part program is a sequence of instructions, which describe the work which has to be done on a part, in, the form required by a computer under the control of an NC, computer program”., , After deciding what NC machines is best suitable and, available for the application, we determine what type of, dimensioning system “he machine uses i.e., whether an, absolute or incremental dimensional system. (Explained, in previous chapter)., , Actually, part programming for NC production consists of, the collection of all data required to produce the part, the, calculation of the tool path etc. in a standard format. The, methods of part programming can be of two types depending, upon the two techniques employed to produce a punched, tape, -, , Manual part programming, , -, , Computer aided part programming., , Manual part programming, In manual part programming, the data required for machining,, is written in a standard format known as program, manuscripts. Each horizontal line in a manuscript represents, a ‘block’ of information., Computer aided part programming, If the component requires a great deal of machining such, as in case of milling machines or contouring applications,, calculation of cutter paths requires more calculations and, sometimes if a machining centre is used then selecting, different tool for drilling, tapping, boring and milling makes, all this part programming more tedious and time consuming., More mistakes are also likely to occur Thus, we use, general purpose computer as an add, to reduce labour, involved in part programming. Also one of the high level, language such as APT (Automatically Programmed Tools),, ADAPT, SPLIT, 2CL, romance, auto stop is used for writing, a computer programme., Procedure for developing manual part program, , Axis designation, Another consideration is designation the axis of the machine, tool. In most cases the programmer already known this, fundamental element when he select the NC machine tool, for his job. The most important factor in axis designation is, the location and position of the spindle., The part programmer also determines how many axes are, available on machine tool i.e. X, Y, Z, a, bar c and so on., Also whether machine tool has a continuous path and point, to point control system., NC words, In order to understand the language of NC information, processing the following definitions should be understood, A ‘bit’ is the basic unit of information represented by either, the absence or the presence of a hole punched on the tape., Bit is an abbreviation of “Binary digit”, which can be ‘0’ or’1'., A code or character is the series of combination of ‘1’ s and, ‘0’ s. It represents a number of an alphabet or any symbol., An NC word is a unit of information, such as a dimension, (e.g. X01 000 orY1 0025) or feed rate (e.g. F1000 and so on., A block is a collection of complete group of NC words, representing a single NC instruction (e.g. N1G01 X100, Z100 F100). An end of block (EOB) symbol is used to, separate the blocks., Block number/sequence number (N - words), , Types of dimensioning system, , Each block of the program has a sequence number which, is used to identify the sequence of a block of data in it which, is in ascending numerical order. This enables the operator, to know which sequence of block is being preformed, practically by the tool. It consists of a character ‘N’ followed, by a three digit number raising from ‘0’ to ‘999’., , -, , Axis designation, , Preparatory functions (G - words), , -, , NCwords, , -, , Standard G and M Codes, , -, , Tape programming format, , -, , Machine tool zero point setting, , The preparatory function is used to initiate the control, commands, typically involving a cutter motion i.e. it prepares, the MCU to be ready to perform a specific operation and, interpret, the data which follows the way of this function. It, is represented by the character ‘G’ followed by a two digit, , The part programming requires an NC programmer to, consider some fundamental elements before the actual, programming steps of a part takes place. The elements to, be considered are as follows., , Copyright @ NIMI Not to be Republished, , 87
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number i.e. ’00 to 99'. These codes are explained and listed, separately., Dimension words (X,Y and Z words), These dimension words are also known as ‘co - ordinates’., Which give the position of the tool motion. These words can, be of two types., Linear dimension words, -, , X,Y,Z for primary or main motion., , -, , U, V, W for secondary motion parallel to X, Y, Z axes, respectively., , -, , p, q, r for another third type motion parallel to X, Y, Z, axes respectively., , model and non - model. Model codes remain active until, cancelled by a contradictory and code of same class. e.g., G70 is a model code which defines that the dimensional, units are metric. It will remain active until cancelled by G, - 71, which tells that the dimensional units are in inches, now. Non - model G codes are active only in the block in, which they are programmed. G04 is non- model code., CNC program procedure (Figs 1 & 2), , Angular dimension words, -, , a, b, c for angular motion around X,Y, Z axes respectively., , -, , I,J,K in case of thread cutting is for position of arc, centre, thread lead parallel to X, Y, Z axes., , These words are represented by an alphabet representing, the axes followed by five or six digits depending upon the, input resolution given., Feed rate word (F - word), It is used to program the proper feed rate, to be given in mm/, min or mm/rev as determined by the prior ‘G’ code selection, G94 and G95 respectively., It is represented by ‘F’ followed by three digit number e.g., F100 represents a feed rate of 100 mm/ min., Spindle speed/cutting speed word (S) - word), It specifies the cutting speed of the process or the rpm of, spindle. It is also represented by ‘S’ followed by the three, digit number. If the speed is given in meter per min. Then, the speed is converted in rpm rounded to two digit accuracy,, e.g. S - 800 represents the 800 rpm of spindle., Tool selection word (T - word), It consists of ‘T’ followed by max five digits in the coded, number Different numbers are used for each cutting tools., When the T number is read from the tape, the appropriate, tool is automatically selected by ATC (Automatic Tool, Changer). Hence this word is used only for machines with, ATC or programmable tool turret. e.g. T01, T02, T03…….., represents the tool selection word., Miscellaneous words (M - words), It consists of character M followed by two digit number, representing an auxiliary function such as turning ON/OFF, spindle, coolant ON/OFF., , The following are the steps involved in the development of, a part program and its proving., Process planning: The programmer carryout a careful, study of part drawing to prepare the process plan. It, includes the following, -, , Machine tools used, , -, , Fixtures required, , End of Block (EOB), , -, , Sequence of operations, , It identifies the end of instruction block., , -, , Cutting tools required, , G and M codes (G, codes), , -, , Process parameters, , This is the preparatory function word, consists of the, address character G followed by a two digit code number,, known as G - code. This comes after the sequence number, word and a tab code. There are two types of G - codes, , Axes - selection: The reference axes should be chosen so, that the coordinates for various features can be determined, easily., , 88, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.4.132
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Tool selection: Various tools are feasible for a given, operation, but some of them would be more economical, than others So it is essential to chose the right tool for the, job., Cutting process parameters planning: For a given tool, and the operation, the appropriate process parameters, such as speed, feed and depth of cut are to be selected., These may be taken from the handbooks supplied by the, cutting tool manufacturer or based on the shop experience., Job and tool setup planning: The initial position of job, and tool are defined carefully., Tool path planning: A careful planning of the tool path, ensures that the required manufacturing specifications are, achieved at the lowest cost., Part program writing: This involves the actual writing of, the part programs undertaking the format and syntax, restrictions into account, Part program providing: Once the part program is, created, ‘it should be verified before it can be loaded on the, machine controller for the manufacture of the component., A trial run can be carried out with or without the tool or work, piece to enable visualization of movements taking place,, and any collision possible between the tool, the work piece, and the clamping device., Definition of character, word and block, Bit: A binary digit is called a bit. In includes 0 or 1. In, punched tape, the values 0 or 1 are represented by the, absence or presence of a hole in a certain row and column, position., , Fixed sequential format with tab ignored: This is the, same as the fixed sequential format except that TAB codes, are used to separate the words for easier reading., Example, 001, , 00, , 70, , 30, , 03, , 002, , 00, , 70, , 60, , 03, , Tab sequential format: This is same as fixed sequential, format with tag ignored except that words with the same, value as in the preceding block can be omitted in the, sequence., Example, 001, , 00, , 002, , 00, , 70, , 30, , 03, , 60, , Word address format: This format uses a letter prefix to, identify the type of word. Repeated words can be omitted., The words run together, which makes the code difficult to, read., Example, N001G00X70Y30M03, N002Y60, Word address format with tab separation and variable, word order: This is the same format as word address, format except that words are separated by TAB, and the, words in the block can be listed in any order. It is the block, format used on all modern CNC controllers., Example, , Character: A character is formed from a row of bits. A, character is a combination of bits representing a numerical, digit (0 to 9), an alphabetical letter (A - Z and a - z ), or a, symbol., , N001, , G00, , N002, , Y60, , Word: Award is formed from a sequence of characters. A, word specifies a detail about the operation, such as X position, Y - position, feed rate, or spindle speed., , The complete part program for a given component consists, of a beginning code of %. A part program consists of large, number of blocks each representing an operation to be, carried out in the machining of the part. The words in each, block are usually given in the following order., , Block: A block is formed from a collection of words. A block, is one complete NC instruction. It specifies a destination, for the move, the speed and feed of the cutting operation,, and other commands that determine what the machine will, do., , X70, , Y30, , M03, , Structure or format of a part program, , -, , Sequence number (N - word), , -, , Preparatory word (G - word), , -, , Coordinates (X -, Y-,Z- words for linear axes; A-, B-,Cwords for rotational axes), , The order in which words appear in a block of instruction is, called the format. The following are the block formats used, in NC programming., , -, , Feed rate (F -word), , -, , Spindle speed (S - word), , Fixed sequential format: This formal was used on many, of the first commercially available NC machines. Each, instruction block contain five words in only numerical data, and in a very fixed order., , -, , Tool selection (T·· word), , -, , Miscellaneous command (M - word), , -, , End - of - block (EOB symbol), , Block format, , Example, 00100703003, 00200706003, , The structure of part program used in fanuc controller is, given below. ., %;, , (program start), , 03642 (program number), , N010, Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.4.132, , Copyright @ NIMI Not to be Republished, , 89
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Blocks, , ................, N100 M02; (program end), M30 (program rewind), , Program number, Each of the program that is stored in the controller memory, requires an identification. It is used while running and, editing of the programs directly from the control console., This identification is specified in terms of a program number, with 0 word address. The number can be a maximum off our, digits., Sequence number (N - word), Each block in a part program always starts with a block, number, which is used as identification of the block. It is, programmed with a N word address., Coordinate function, The coordinate values are specified using the word address, such as X,Y, Z, U, V, W, I, J, K, etc. All these word, addresses are normally signed along with decimal point, depending upon the resolution available in the machine, tool., , Address, , Function, , N, , Sequence number to identify a block., , G, , Preparatory word that prepares the, controller for instruction given in the block., , X,Y,Z, , Coordinate date for three linear axes., , U,V,W, , Coordinate data for incremental moves, in turning in the X, Y and Z directions, respectively, , A,B,C, , Coordinate data for three rotational axes, X, Y and Z respectively., , R, I,J,K, , Radius of are, used in circular, interpolation., Coordinate values of arc centre,, corresponding to X,Y and Z-axes, respectively., , F, , Feed rate per minute or revolution in, either inches or millimeters., , Comments, , S, , Spindle rotation speed., , Parentheses are used to add comments in the program to, clarify the individual functions that are used in the program., When the controller encounters the opening parenthesis,, it ignores all the information till it reaches the closing, parenthesis., , T, , Tool selection, used for machine tools, with automatic tool changer or turrets., , D, , Tool diameter word used for offsetting, the tool., , Example, , P, , N010 GOO Z50 M05 (Spindle stops and rapidly moves up), Table - common word addresses used in word address, format., , It is used to store cutter radius data in, offset register. It defines first contour, block number in canned cycles., , Q, , It defines last contour block number in, canned cycles., , M, , Miscellaneous function., , Types of offsets, Objective: At the end of this lesson you shall be able to, • list the types of offsets used in CNC machine., Types of offsets, There are three type of offsets used in CNC machine, operation. They are:, , To make the tool to move with reference to the job, work, offset or zero offset has to be taken., Procedure for taking work offset, , (i) Work offset (or) zero offset, , Clamp the job in the chuck of the machine, , (ii) Geometrical offset, , Set the tool In the required order set in the machine turret, , (iii) Wear offset, , Set the jog mode or the tool and touch the face of the job., , Work offset (or) zero offset, , With the use of 2 paper check the proper contact of tool with, the face., , Every manufacturer fix a reference point on the spindle of, the machine according to the design of manufacturing., The tool will take the command and move with reference to, this machine reference point., 90, , Now select the work co - ordinate system from G54 to G59., Enter the Z value in the selected work co - ordinate system., Now touch the diameter with the same tool., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.4.132
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Check the contact of the tool with the job using a paper., Now enter the diameter of the job in the tool contact point, in the X value in the selected work co - ordinate system, This particular work co - ordinate system should be, mentioned in the part program., Geometrical offset, The tools used in a CNC machine are of different, geometry. The length of the tools vary accordingly., Even if the work offset is taken for a tool it will not suit the, other tools., So for every tool offset is taken and entered in tool offset, value in work co - ordinate system., Because of this every tool will take the work zero point as, origin., , This command will clear any previous values and will measure the current tools tool offset in Z axis., Now touch the tool to a know diameter on the component., Again in the tool - geometry page enter the command X, (The value of the diameter) for example if the diameter is, 50 mm then X50., Follow the same procedure for the remaining tools, Enter the Z and X commands for various tools in the under, respective tool number., Wear offset, Because of long running the tool tip may wear out and the, dimension of the job may increase or decrease from the, original programmed dimension., To rectify this defect wear offset is used., , The procedure for geometrical offset is given below., , Procedure for entering wear offset, , Clamp the job in the chuck of the machine., , If the programmed size is X40.48 and the machine size is, 40.44 in this 0.04 mm is reduced due to tool wear., , Set the tools in the required order in the machine turret., Select the jog mode or MPG mode., Select the first tool and touch the face of the job., Check with a piece of paper whether the contact of tool, with the job is proper., Now take the geometrical offset page and enter under the, tool number the command Z 0 (zero)., , To rectify this take the tool offset number of the worn out, tool., In that tools wear offset number enter the value U0.04, In the inner diameter defects instead of positive value put, U - 0.04 in the wear offset number., The tool offset number and wear offset number are same., , Reference points of CNC machines, Objective: At the end of this lesson you shall be able to, • explain the features of reference point applied in CNC machine tools., Zero and reference points on CNC machine tools, , -, , Initial set - up of the machine., , Reference zero points are the base or starting points that, are chosen as the reference for calculating the coordinates of the other points. Also, reference zero points are, called the zero points. CNC controls use the following, zero points to facilitate the programming of tool paths., , -, , As the reference point for other reference points such, as reference return points, work zeros, and program, zeros., , -, , As the tool change position., , M Machining reference zero point, W Work part zero point, R Relative point, Machine zero point, M, The machine zero point is the origin of the machine coordinate system. It is set by the machine tool manufacturer, and cannot be changed., The machine zero is labelled with an M and represented, by the symbol shown above., Normally the machine zero is not directly used as the, reference point for writing part programs. It may be used, in one of the following three applications., , Work part zero point, W, A work part zero point is the origin of the work piece's, coordinate system. It is used to determine the work's coordinate system in relation to the machine zero point. The, work zero points are often referred to as set - up points, because they are the location for setting up the workpiece, on the machine table. some CNC controls allow the use, of multiple work zero points in one machine set up or, operation. The work zero point is labelled by W and represented by the symbol above., The work zero point can be chosen by the programmer at, any convenient location within the working envelope of the, machine. It is recommended that you place the workpiece, zero point in a way that it can be easily located and measured on the workpiece., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.4.132, , 91
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Reference return point, R, In Fig 1 reference return points are the locations to which, the machine table or the spindle is returned. They are, identified by the letter R and are represented by the above, symbol., , 92, , The location of the first reference return point is precisely, predetermined in each moving axis in relation to the machine zero point. Because of this, it can be used for calibrating and regulating the measuring system of the slide, table and spindle., Specifically, the reference point is used in four situations, -, , When the control is powered up, all axes always must, be positioned at the reference return point to calibrate, the measuring system., , -, , The machine must be re-positioned to the reference, return point for re-establishing the proper coordinate, value in situations such as losing the current position, data due to electrical failure or improper operation., , -, , All axes must be retracted to the reference point, before the tool change can take place., , -, , At the end of the program, all axes must be retracted, to the reference return point to reset the control system for re - running the part program or running a new, program., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.4.132
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Production & Manufacturing, Related Theory for Exercise 4.4.133, Turner - Programming and Simulation, CNC Simulation Process, Objectives: At the end of this lesson you shall be able to, • understand the function of a CNC simulation, • learn the benefits of simulator., Simulation process in a CNC machine system is a program, verification activity. Most of the CNC machines come with, suitable simulation software installed., This software simulates the tool movement on a graphic, screen. The software first checks the program syntax., When the program is found correct, the simulation starts., In simulation, the dimensions of the given component is, shown on the screen and the chosen tool start moving with, respect to the program command., The resulting shape that will be obtained on completion of, simulation represents the final size & shape of component., , Purpose of Simulator, The purpose of CNC Simulator Pro is to provide the CNC, community with a versatile Full 3D simulator with CAD/, CAM capability. In the simulator you may find different type, of machines like milling machines, router, lathes, cutter,, 3D printer etc,., It automatically adapt your part programmes to different, CNC machines. The simulator solution provides the break, down of the details of tools used during the job, the, positioning of fixtures & part for multi-setup operation;, through providing a shop floor documentation., , With this software, it is easily possible to analyse the tool, path, during the turning process., , The traditional APT-based simulation system, only simulate, the planned tool-path where as modern advance control, Enulator, delivers a more meaning simulation, recreating, how the machine will react the G-code generated by your, post-processor. It provides powerful validation method, allowing users to determine the association between, G-code & specific operations inside the NC program., , The flow chart for simulation process is shown below:-, , Ex:, , Simulation (verification of program) can be done block by, block., , G04, , X2.0 [Dwell at 2 second], , X30.25, , Y5.00, , G03, , X35.25 Y10.00, , G01, , X35.25 Y50.10 - Toolpath, , G03, , X5.00, , G03, , X35.25 Y10.00, , Y50.10, , Most common used of simulator:•, , Technical Training for programmers & operators in, Training center., , •, , Editing/simulation in design dept., , •, , Machining time estimate., , •, , In preparing equation processing., , Copyright @ NIMI Not to be Republished, , 93
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Production & Manufacturing, Related Theory for Exercise 4.4.134, Turner - Programming and Simulation, Process and tool selection (CNC), Objectives: At the end of this lesson you shall be able to, • understand selection of tool for CNC, • understand the factors contributing for tool selection, • learn about MachiningCloud APP., The main factors that should be considered while writing a, CNC programme, is what type of tooling should be selected, for a specific job. Making the right selection depends on, how well one understand the vital factors that may have, impact on the job., The selection of tool is based on:, •, , The machine being used for the manufacture., , •, , The material used for the job., , •, , The quantity of machining parts., , •, , The requirement of the customer., , •, , The specification of the tool to be used., , All the above five factors are related and interlinked. All the, information are avaliable in Router of Tool Directory., The tool used for CNC mainly depends on the type of, material used, type of workdone, quality of finish needed, the no.of components to be run etc,., CNC machine may have different tool configuration. One, should know which tool configuration is suitable for hard, material or a typical raw material. The Direction of cut, is, another factor which affects the tool life, and quality of the, cut based on customer specification, the cutting speed,, spindle speed & feed are important in the manufacturing, process., The tool selection has to be done following the steps shown, below:, step 1: What type of machining is needed?, Collect the machine drawing of the finished part, and collet important information such as, size,shape, stock material,speed & feed for various, operation, namely turning, facing, boring etc., step 2: What is the work piece material?, Ascertain the workpiece material & the parameters, like chip forming, material hardness, alloy, elements.These information have significant, influence on the spindle speed & feed rates., step 3: What are the Capabilties of your machine?, , workpiece clamping. Similarly tool holding details, such as Holding strength, axis/radial runout, tool, overhang etc needs to be considered., step 4: What Machining Operation needed?, The operation can be face turning, OD turning, ID, turning (Boring), grooving/profiling, threading of, the components. Geometry & tolerances, permissible such as dimensional accuracy,, surface finish, part distortion, surface integerity, etc., step 5: In what order should operations to be performed?, This includes minimising tool changes, travel, distance between operations, achiving shortest, cycle time, maintaining consistency etc,., spet 6: What type of tool are needed?, Parameters such as part material/tool mateial,, depth of cut to be given, smallest concave radius, etc are to be taken into consideration to decide, the tool material, inserts, shape, tolerance etc,., C & W inserts are used for rough machining, D & V inserts are used for finish machining., Square or round shape inserts used for grooving., 3 point inserts are used for threading., step 7: Are the required tools available?, MachiningCloud APP is an independent provider, of CNC cutting tool product data. This provides, most up-to-date information, directly obtained, from the manufacturer. Information can be obtained, by download Machining Cloud APP., step 8: What feeds & speeds should I use?, Material run better at specific SFM. The, recommended SFM for cutting aluminium is 150, to 400. SFM is the combination of cut diameter &, RPM. SFM is constant for a material. RPM mode, G97 is useful for centre cutting operations (drilling), CSS mode (G96) is useful for good surface finish,, better tool life. (SFM- Surface Feet / Minute,, CSS- Common Surface Speed), , This includes machine HP, stability, horizontal or, vertical type, spindles type & size, no.of axes,, 94, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.4.133
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Production & Manufacturing, Related Theory for Exercise 4.4.135, Turner - Programming and Simulation, Part programe for Grooving, Objectives: At the end of this lesson you shall be able to, • learn about G75 grooving cycle, • understand that grooving linking with parting, • follow the part programme of a grooving cycle., Grooving canned cycle [G75], , Introduction, Grooving is an important & complicated operation in, turning. G75 is the grooving cycle in ‘X’ in a CNC machine., Grooving is an operation in which the tool is plunged into, surface of the work piece until the proper depth is reached., The grooving has to be done step by step and grooving, cycles have been developed which allows for wide grooves, to be cut with multiple passes by a specific shift value with, a Q-word, and P word for depth of cut., , Grooving cycle (G75), %, O0013, N1;, , In grooving, the grooving tool is positioned to the start point,, then call the canned cycle. The tool will take an initial cut, to the finished diameter. Then it will retract to the starting, X-position & move over in the Z axis by the amount specified, with the P-word. The tool will make several passes until it, reaches the programmed Z cooridnate. If the X coordinate, is programmed to zero grooving will become parting., The syntax of G75 code is as follows:, G75 R___;, G75 X___Z___P___Q___F___;, Where,, , G28, , U0, , W0;, , G97, , S600, , M03;, , T0303; [4mm groove width], G00, , X31.0, , Z5.0, , G01, , Z-29.0 F0.1;, , G75, , R1.0;, , G75, , X20.0, , G00, , X35.0;, , Z5.0, , M09;, , G28, , U0, , M08;, , Z-37.0 P500, , Q4000 F0.08;, , W0;, , M05;, M30;, , R = Reliving the tool, X = Groove diameter (mm), Z = Groove length (mm), P = Depth of cut in ‘x’ axis in microns (radial value), Q = Shift value in Z axis microns, F = Feed, , Copyright @ NIMI Not to be Republished, , 95
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Production & Manufacturing, Turner - CNC Turning Operation, , Related Theory for Exercise 4.5.139, , Programming on CNC Tapping, Objectives : At the end of this lesson you shall be able to, • learn what is G84 code in CNC, • understand tapping cycle, • learn the differefce between rigid tapping & long form tapping., G84 code in CNC progrmming refers to tapping cycle in, CNC. This is carried out with tapping heads, and Tension/, Compression tap holders., , Tapping comes under canned cycle with intermittent feed,, with Dwell spinlde CW with feed retraction in Z direction as, shown in table below., , G84 code is commonly used program for tapping, used on, threaded holes. There are two ways of tapping program., , Example: Tap 1/4-20 thread 0.500” deep at 0,, , •, , One using tapping cycle with rigid tapping capabilities., , • Long Form (no canned cycle needed) programming, when a tapping head is used that do not have rigid tapping., To use rigid tapping, the CNC machine should support the, synchronnisation of feed motion with the spindle speed., , Here is the Gcode, M03;, M8 (Speed & feed rate), S400, , F20 (Tapping), , Z1.0;, , G84 code is tapping RH threads with M3 spindle rotation., , G00, , X0.0, , G74 code is tapping LH threads with M4, , G01, , M29;, , Rigid motion mode is used in Fanuc control using M29, code., , G84, , Z-0.5, , Advantages, •, , •, , •, , A tapping head may have a gear ratio that allows it to, retract faster. You will want to change feed rate when, retracting., A Dwell at the bottom of the hole may be helpful as the, spindle reverse to even out the amount of spring, adjustment being used., It is possible to drag the feed rate a bit., , Y0.0;, R02;, , M03 spindle in right direction, M8 collant ON, S400 Spindle speed 400rpm & feed rate 20, Next we move to save Z&XY., Switch G01 & M29 to turn rigid tapping lastly G84 is run, with Z indicating coordinate & R retracting coordinate., If we had more holes to be tapped we can list their XY, coordinate, viz, G84, , Z-0.5, , R0.2;, , X0.0, , Y1.0 etc etc;, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.5.139, , 101
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TABLE 1, Canned cycle used in OMC, , 102, , G-code, , Application, , Z-direction, , operation at the, bottom of the hole, , Retraction in, Z direction, , G73, , High speed peck drilling, , Intermittent feed, , Dwell-spindle rotates, CW spindle orientation, Tool tip moved opposite, to cutting & retracted, , Feed, , G76, , Fine boring, , Feed, , -------, , -------, , G80, , Canceling of G81-G89, , ------Cycles, , -------, , -------, , G81, , Centre/spot drilling, , Feed, , -------, , -------, , G82, , Counter bore/counter sink, , Feed, , Dwell, , Rapid traverse, , G83, , Peck/deep hole drilling, , Intermittent feed, , -------, , Rapid traverse, , G84, , Tapping cycle, , Feed, , Dwell spindle CW, , Feed, , G85, , Boringcycle, , Feed, , -------, , Feed, , G86, , Boring, , cycle, , Feed Spindle stop, , Rapid traverse, , G87, , Back boring cycle, , Feed, , Spindle CW, , Rapid traverse, , G88, , Boring cycle, , Feed, , Dwell-spindle stop, , Manual retract, , G89, , Boring, , Feed, , Dwell, , Feed, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.5.139
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Production & Manufacturing, Turner - CNC Turning Operation, , Related Theory for Exercise 4.5.141, , CNC programming on Threading, Objectives : At the end of this lesson you shall be able to, • learn about G-WIZARD software, • programme for thread canning cycle, • understand the difference between single line and double line command., The important thing in thread authing operation is to fix up, the thread start and thread end positions. The end position, is easier in Z axis, as we know the length of threaded, component. For thread cutting in CNC lathe, G-Wizard, thread calculator software, provides complete database, for all threads., The start position is interesting as we start threading, somewhere from outside the threads. You need to leave, some allowance in Z to give CNC machineto synchronize, the feed rate with spindle rotational position, Cutting, thread puts more stress on the cutter. Thread height, taper, amount, thread pitch or lead, therad infeed angle (TN, angle) are important in making the programme., G76 is threading cycle followed in CNC Program., Tips & thoughts on passes in threading cycle is detailed, below., G76 Threading Cycle Tips and Thoughts on Passes, Passes, The number of passes that must be cut to make your, thread is very important. Take too few passes, and surface, finish is apt to be poor and you might even break your, threading tool by forcing it to work too hard. Take too, many passes and you're going to waste a lot of time., You can't change most of the information relating to the, thread's specifications, so your primary tools for controlling, the number of passes include:, – Start Position: Turn things down as I describe above, to minimize the work the threading tool must do., – First Pass Depth: Pick the largest pass you can. GWizard Calculator will give you a good recommendation, here., – Minimum Pass Depth: Try to avoid using this parameter, too much and set it to your Finish Allowance., – Finish Allowance: A smaller finish allowance can mean, larger roughing passes remove most of the material., Just remember, too small an allowance will force your, cutter to rub., – Spring Passes: You shouldn't need more than 2 passes, and 1 may suffice. Experiment with your particular, situation to see if you can get by with 1 or perhaps, even no spring passes., Your next challenge will be in determining how many, passes the cycle will actually make. This is not easy as, G76 will dynamically change the depth of each pass after, the first to equalize the amount of material removed. You, , have to do quite a lot of calculation to figure out exactly, how many passes will be made., But there if you have a GCode Simulator, it may be able, to help out. Take a look at this screen shot of G-Wizard, Editor:, Fanuc Double Line G76 Threading Cycle, G76 P(m) (r) (a) Q(dmin) R(d), G76 X(U) Z(W) R(i) P(k) Q(d) F(L), P Word: The P-word has 6 digits consisting of three 2digit clusters for m, r, and a., m: Repetitive finishing count (1 to 99)-spring passes., r: Chamfering amount (1 to 99), a: Angle of Tool Nose. Select 80, 60, 55, 30, 29 or 0, degrees., Q Word: dmin is the Minimum Cutting Depth. If the depth, of either a roughing or finish pass is less than this, it is, clamped to be at least this much., R Word: d is the finish allowance., X/Z/U/W words (2nd line): Specify the coordinates of the, end point. X, Z use the current mode (absolute or relative), while U, W can be used to specify a relative position., R Word (2nd line): i is the taper amount when cutting, tapered threads., P Word (2nd line): k is the thread height expressed as a, radius (not diameter) value., Q Word (2nd line): d is the depth of the first cut., F Word (2nd line): L is the lead of the thread., Example: Fanuc 2 line G76 cutting a tapered pipe thread:, Fanuc Single Line G76 Threading Cycle, G76 X.. Z.. I.. K.. D.. F.. A.. P.., X = Diameter of last threading pass, Z = Position of the thread end, I = Taper over total length, K = Single depth of the thread - positive, D = Depth of first threading pass - positive, A = Included angle of the insert - positive, P = Infeed method (one of 4), Haas G76 Threading Cycle, , K.. X.. Z.. U.. W.. I.. P.. F.. A.., Copyright @ NIMI Not toG76, beD..Republished, , 105
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D = Initial cut depth, , Q = Compound slide angle (optional), , K = Thread height, , H = Spring passes (optional), , Z* = Z-axis absolute ending location. Determines thread, length., , E = Distance along drive line for taper, , U* = X-axis incremental distance to end. May be used, instead of X., W* = Z-axis incremental distance to end. May be used, instead of Z., I* = Thread taper amount (radius measure)., P* = Subsequent pass positioning method (1-4), F* = Feedrate, A* = Tool nose angle (0 -120 degrees. 0 assumed if not, specified), LinuxCNC / PathPilot G76 Threading Cycle, G76 P.. Z.. I.. J.. R.. K.. Q.. H.. E.. L.., P = Thread pitch in distance per revolution, Z = Final position of threads, I = Thread Peak offset. Negative for external, positive for, internal., , L = Which end of the thread gets tapered. L0 = no taper., L1 = entry taper. L2 = exit taper. L3 = entry and exit, taper., Mach 3 G76 Threading Cycle, G76 X.. Z.. Q.. P.. H.. I.. R.. K.. L.. C.. B.. T.. J.., X = X end, Z = Z end, P = Pitch, H = Depth of first pass, I = Infeed angle, R = X Start (optional), K = Z Start (optional), L = chamfer (optional), C = X Clearance, B = Depth Last Pass (optional), , J = Initial cut depth, , T = Taper (optional), , K = Full thread depth, , J = Minimum depth per pass (optional), , R = Depth digression (optional). R = 1 is constant depth,, R =2 is constant areas., , 106, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.5.141
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Production & Manufacturing, Turner - CNC Turning Operation, , RelatedTheory for Exercise 4.5.142, , Trouble shooting in CNC machines, Objectives : At the end of this lesson you shall be able to, • learn trouble shooting of CNC machines, • understand electrical/electronic problems & remedy, • understand hydraulic problem & remedy., Introduction: A CNC Machine operates on, electrical,electronics mechanical, pneumatic and hydraulic, system invovled in its automation. If one of the above, elements doesnot function or function partially the whole, machine will come to stand still position. In CNC machine, trouble shooting arises due to electrical,servo and, mechanical problems., The trouble shooting can be split in to:, 1 PLC trouble shooting, 2 Low voltage problem, 3 Power up problem, 4 Zero return problem, 5 Door inter lock circuit problems, 6 Relay board repair and problems, 7 Hydraulic system trouble shooting, General causes of failure in electrical and electronic, devices, , 3 Dust particles results in short circuit,corrosion of tracts,, PCBs and fuse getting blown. To avoid this dust, protective guards should be fitted., 4 Improper ventillation results in malfunctioning of, electronic circuits., 5 Poor supply voltage with poor voltage regulation affects, the sensitive electronic device. Suggested not to operate, welding machines near CNC machine., 6 Electrostatic charges transfer from human body may, damage electronic components,leads to lose of data, and hence, store PCBs in anti-static covers., Poor switching devices like contactors,chokes., Transformers are to be grouped & separated from CNC, system. The AC cables should not run parallel for long, distance., Safety Interlocks in CNC machines:, Power chucks should be damped befroe execution in, MDA, Auto mode or single mode., During cycle, in case of pressure failure, both spindle and, axis should stop., , •, , Poor earthing, , •, , Loose connection, , •, , Dust particles or coolant entry, , •, , Improper ventillation, , •, , Blocked air circulation, , •, , Poor supply voltage condition, , •, , Sag for duration less than 2.5 seconds, , •, , Surge for duration less than 2.5 seconds, , •, , Spike (very high voltage lasting for few micro seconds), , •, , Blockout/Brown out greater than 2.5 seconds, , •, , EMI (electromagnetic interference) affect switching, drill, leads to data corruption., , Tips, , If slide lubrication system fail, cycle may continue till M30/, M02 of programme. The fault has to be rectified for cycle, restart., Jogging of axis is not permitted when the cycle is in, progress. Spindle & collant stops automatically with M30/, M02 command., If an unspecified battery is used (For memory, pulse coder), it may explode. Replace the battery only with the specified, one (A02B-0177-K106). Dispose used batteries in, accordance with applicable laws., Trouble shooting of Alarm 960 due to abnormal 24V input, power (Fish bone diagram) is shown., , 1 Earthing between servo amplifier and CNC machine is, a wrong practice. CNC mchine and electrical cabinet, should be earthed directly individually., 2 Loose connections leads to failure of CRT monitors,, input/output cards, measuring circuit, interfaces., , Copyright @ NIMI Not to be Republished, , 107
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Shaft jammed, Defective motor, PLC malfunction, Fuse on, spindle drive etc are other causes., Effects :, Spindle not rotating, The cause and effect diagram shown, can be further, developed by adding some more causes., By carrying out the corrective action the problem can be, sorted out., , Trouble shooting on specific elements, Elements, , Sympton, , 1 Motor Surface, , Cutting fluid on motor, , Remedy, Clean the motor, , 2 Fan motor, , Not rotating, remove dirt etc, , Tighten the loose connection,, , 3 Motor shaft bearing, , Unusual sound, , Replace Bearing, , 4 Abnormal vibration, , Noise, , 5 Cooling air path, , Clogged with dust, , 6 Interlock safety circuit, , control cabinet, , Check all Bearing, belts,etc, Clean air path, Check all interlock keys fully, engaged at rest., Check interlock module in, control cabinet, check, contacters, , 7 Chuck/Actuator, , Hyd, pump not running, , Check ladder diagram, Power ON and test, set, the pressure higher, Check input signal of foot switch, , 8 Soft over travel machine, alarm occurs on zero returning, 9 CNC is crashed (some slips, during machine switch), Backup battery, , Brake does not stop axis, CNC control gets goofed up, Needs replacement, , Lubrication pump problem, , Noise in axis, Axis motor overload alarms, , Reset after completing zero, return, Power down & then backup or, reset, Keep encoder position when, power is shut off, Double the oil, Check for leaks, Check the distribution mainfold, Clean the filter if clogged, ensure, correct oil is fed., , 108, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.5.142
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Remedies For Chart 1, a Any or all of the following: Replace dirty filters. When, strainers in solvent compatible with system fluid. Clean, clogged inlet line. Clean reservoir breather vent. Change, system fluid. Change to proper pump drive motor speed., Overhaul or replace super-charge pump. Fluid may be, too cold., b Any or all of the following: Tighten leaky inlet, connection. Fill reservoir to proper level (with rate, exception all return lines should be below fluid level in, reservoir). Bleed air from system. Replace pump shaft, seal (and shaft if worn at seal journal)., c Align Unit and check condition of seals, bearings and, coupling., d Install pressure gauge and adjust to correct pressure., e Overhaul or replace., , d Install pressure gauge and adjust to correct pressure, (keep atleast 125 psi difference between valve settings), e Overhaul or replace., f, , Change filters and also system fluid if improper viscosity., Fill reservoir to proper level., , g Clean cooler and/or cooler strainer. Replace cooler, control valve. Repair or replace cooler., Remedies For Chart 3, a Any or all of the following : Replace dirty filters, clogged, inlet line. Clean reservoir breather vent. Fill reservoir to, proper level. Overhaul or replace supercharger pump., b Tighten leaky connection. Bleed air from system., c Check for damaged pump or pump drive. Replace and, align coupling., d Adjust, e Overhaul or replace., f, , Check-position of manually operated controls. Check, electrical circuit on solenoid operated controls. Repair, or replace pressure pump., , g Reverse for rotation., h Replace with correct unit., Remedies For Chart - 4, a Replace dirty filters and system fluid., b Tighten leak connecitons (fill reservoir to proper level, and bleed air from system)., c Check gas valve for leakage. Charge to correct, pressure. Overhaul of defectives., d Adjust., e Overhaul or replace., Remedies For Chart - 5, a Fluid may be too-cold or should be changed to clean, fluid of correct viscosity., b Locate bind and repair., c Adjust, repair or replace., Remedies For Chart 2, a Any or all following: Replace dirty filters.clean clogged, inlet line. Clean reservoir breather vent. Change system, fluid. Change to proper pump drive motor speed., Overhaul or replace supercharge pump., b Any or all the following: Tighten leaky inlet connections., Fill reservoir to proper level (with rare exception all return, lines should be below fluid level in reservoir). Bleed air, from system. Replace pump shaft seal (and shaft if, worn at seal journal)., , d Clean and adjust or replace. Check conditons of system, fluid and filters., e Overhaul or replace., f, , Repair command console or interconnecting wires., , g Lubricate., h Adjust, repair or replace counterbalance valve., , c A link unit and check condition of seals and bearings., Locate and correct mechanical binding., Check for work load in excess of circuit design., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.5.142, , 109
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110, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.5.142
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112, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.5.142
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Production & Manufacturing, Turner - CNC Turning Operation, , Related Theory for Exercise 4.5.143, , Factors affecting Quality & Productivity, Objectives : At the end of this lesson you shall be able to, • understand the definition of quality, • learn characteristic & elements of quality, • learn the increased productivity through implements TPM., Introduction, Quality & Productivity are vital requirements of modern, advanced manufacturing techonologies. Better quality is, achieved through adopting (TQM) and higher productivity, can be achieved through implementing Total Productive, Maintenance (TPM)., To achieve exact quality, we should know the real meaning, of quality which is defined by many Quality Experts such, as,, , •, , Durability of product life, , •, , Providing service after sales & fully resolving problems, & complaints, , •, , Customer handling and care is a highly sensitivity area, , •, , Meeting customer’s delight through improving aesthetics, , •, , Estabilishing reputation through past performance and, other intangible efforts., , Quality characteristic:, , Quality:, , It can be broadly grouped under Design, Conformance,, Assurance & Control,, , •, , Is fitness for use, , Quality of Design, , •, , Should be aimed at needs of customer, , •, , As the conformance to requirements, , •, , Meeting the customer satisfaction, , •, , Meeting all the characteristic of a product as per, specification, , •, , As per ISO defined as ratio of P/E, with P performance, & E Expectation, , Importance of Quality:, •, , Quality can be result in,, , •, , Bringing out customer delight, , •, , Increasing market share, easy marketability, , •, , Increasing customer base, customers, , •, , Increased profitability, , •, , Becoming an industrial hero,entering globalisation, , •, , Increased morale of the employees of ISO unit, , with more repeated, , The various paramters of quality of a product can be, listed out as:, , •, , Performance of the product, , •, , Features of the product, , •, , Conformance with the requirement of product standard, , •, , Reliability of the product not failing within stipulated life, cycle, , 114, , Quality of conformance, Quality of conformance is the fidelity with which a product, or a service conforms to the specified requirements., Quality Assurance, Quality Assurance comprises of all those planned and, systematic actions necessary to provide adequate, confidence that a material, structure, component or system, will perform satisfactorily in service. Quality assurance, includes quality control., Quality Control, , Dimensions of Qulaity:, •, , Quality of design is the excellence of the design in relation, to the ease of manufacture and meeting the customer, requirements., , Quality control comprises of all those quality assurance, actions related to the physical characteristics of a material,, structure, component or system which provide the means, to measure and maintain the material, structure,, component or system to pre-determined requirements. The, main aim of quality control is defect prevention., Predictive Maintenance, In predictive technique, on the prediction of any fault,, maintenance is being done. It is comparatively a newer, maintenance technique., In this technique, equipment condition is measured, periodically or on a continuous basis., This enables maintenance staff to take a timely action, such as equipment adjustments, repairs and overhaul., Predictive maintenance extends the service life of an, equipment without any fear of failure., , Copyright @ NIMI Not to be Republished
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TPM Implementation (Fig 1), , work culture resulting in better product quality and, productivity., Objectives, Get operators in touch with their equipment to make them, more familiar with it, develop curiosity and sense of, belonging of ownership and concern., Establish and maintain basic equipments conditions by, thorough cleaning, lubricating and Tightening., Increase the availability of plant and Machinery, capacity, utilization and to improve overall equipment efficiency., TPM Target, , For a productive manufacturing system, a good, maintenance is the fundamental requirement. TPM is all, about keeping the plant and equipment at its highest, productive level through co-operation of all areas of the, organization. This approach does not disregard the, techniques such as predictive and preventive maintenance., Predictive maintenance and preventive maintenance are, the basis for a successful TPM environment., Benefits of TPM, The properly implemented TPM has made excellent, progress in a number of areas. These include:, • Increased equipment productivity, • Improved equipment reliability, • Reduced equipment downtime, • Increased plant capacity, • Extended machine line, • Lower maintenance and production costs, • Approaching zero equipment - caused defects, •, , Improved team work between operators and, maintenance people, , •, , Enhanced job satisfaction, , •, , Improved return on investment, , •, , Improved safety, , P Productivity improvement…………., • Reduction in Number of Sporadic, Failure ……………………………, • Equipment Operating……………, Q Reduction in Product Defects…….., Reduction in Customer Claims……, , TPM implementation calls for change in attitude of, operational personnel. It requires patience, perseverance, and persuasion to encourage workmen to think., , 1/10 to 1/250, 1.5 to 2 times, 1/10, 1/4, , C Reduction in Maintenance Cost…., , 30%, , D Reduction in Product Inventories.., , 0, , S Reduction in Accident, Elimination, of Pollution …………………………, , 0, , M Increase in Number of Employee, Suggestions ……………………, , 5 to 10 times, , The Goals OF TPM, Maximize equipment effectiveness (Improve Overall, efficiency), Equipment effectiveness increases the productivity by, minimizing input and aiming maximum output. Though, "Output" means not only the quantity of production, but, also the better quality, lower cost, timely delivery, improved, industrial safety & hygiene, higher moral and favourable, working environment. Equipment effectiveness is increased, by the reduction of the following six big losses:, •, , Downtime losses, • Break down, , Total Productive Maintenance (TPM), TPM is system oriented structured approach towards, excellence in all spheres of Industrial Management and, powerful means to achieve high level product quality and, productivity through efficient utilization of all resources like,, man, Machine, Material, Money, Minute, space and, opportunity by Total employee participation through group, activities and Autonomous Maintenance., , 1.5 to 2 times, , • Setup & adjustment, •, , Speed losses, • Idling & Minor stoppages, • Reduced speed, , •, , Defect losses, • Defects in the process and reworks, • Reduced yield between machine startup and stable, production, , It is my machine and I have to maintain it : I operate this, machine and someone else maintains it" though change, of attitude is slow to achieve but has dramatic effect on, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.5.143, , 115
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Types of TPM, , 2 Scheduled or Routine Maintenance, , •, , Corrective or Breakdown Maintenance, , •, , Scheduled or routine maintenance, , •, , Preventive Maintenance, , •, , Predictive Maintenance, , Scheduled maintenance is a stitch-in-time procedure, aimed at avoiding breakdowns. This includes all work, undertaken to keep the production equipment in efficient, condition. It may cover periodic inspection, cleaning,, lubrication, overhaul, repair, replacement etc., , 1 Corrective or Breakdown Maintenance, Corrective maintenance implies that repairs are made after, the failure of machine or equipment. It says wait until a, failure occurs and then remedy the situation as quickly as, possible. For example, replacing gears in a machine only, after the gears get failed and become inoperative., , 116, , 3 Preventive Maintenance, Preventive maintenance is carried out before the failure, arises or prior to the equipment actually breaks down. It is, a safety measure designed to minimize the possibility of, unanticipated breakdowns and interruptions in production, It involves repetitive and periodic upkeep, overhauling,, servicing to the equipment to prevent breakdown., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.5.143
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Production & Manufacturing, Turner - CNC Turning Operation, , Related Theory for Exercise 4.5.144, , Parting off Operation in a CNC, Objectives : At the end of this lesson you shall be able to, • understand what is G75 command, • learn the parting off operation, • aware of latest techniques in parting off., Out of all the turning operation like turing, facing, grooving,, taper turning etc, parting off operation is the one which, causes trouble to most operators. ‘Parting off’ is definitely, a challenging operation when you look at it mechanically,, because the cutting tool is fairly thin, plunging deep into the, material., , Many of the machine controls have a peck option on G75, grooving code, which is used for parting off. In conventional, CNC mode, there is a provision for “Parting off with peck”, option Fanuc’s G75 is newer control uses a two line format:, G75, , R0.002, , Once the tool tip is deep down in the parting groove of the, material, getting chips out & lubrication of cutting tool, is, a real program. If the lathe is sturdier, and has good rigidity, parting may be easier. In manual parting, the operator with, draws the tool from the groove whenever he hears a, squeaks. The parting tool should be set to exact centre of, the job, otherwise there is a definite possibility of an, accident, involving tool breakage, or job getting damaged., , G75, , X1.0, , But parting in CNC is different where the “touchs” of manual, machining is absent, hence the idea of “Peck Parting” was, developed., , P0.125 F10 (Refer Fig 1), , Where R is the amount of retraction after each peck (X1.0,, Z-10.0) is the lower left corner of the grooving to its, reference point and the grooving is being done from right to, left. P is the depth of cut for each peck at a feed rate of F., So each peck cuts a distance of P retracts a distance R,, Then re-engages the material and does another peck of, distance p and cycle goes on till the bottom is reached., If ‘Q’ value is specified with a Z value, then it means the, groove is wider than tool widths, , Most machinist will be familar with peck drilling cylces,, where the drill bit is retracted a little to break a chip or a lot, to help extract chips from a deep hole over and over again., In parting off also we get the benefit if the tool retaces for, every advances., , Copyright @ NIMI Not to be Republished, , 117
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Production & Manufacturing, Turner - CNC Turning Operation, , Related Theory for Exercise 4.5.145, , Bar Feeding System through Bar Feeder, Objectives : At the end of this lesson you shall be able to, • learn about the bar feeding operation, • learn the advantages of bar feeding mechanism, • learn the limitations of the system., The Bar feeding mechanism is a metal cutting machine tool, designed to feed the metal. This machine is exclusively, intended for mass production and they represent faster and, more efficient way to feed a stock. Automatic Bar Feeding, mechanism (ABF) consists of three major blocks. They, are:, •, , Metal feed mechanism, , •, , Bar clamping mechanism, , •, , IR sensor unit, , The IR unit determines the dimension for cutting the bar, clamping is through pneumatic system, which is highly, reliable and effective., Need for Automation of Bar feeding, , The motor will be rotated, so that the bar is moving from, initial position to the determined position., IR sensor unit is used to deternmine the bar dimension to, be cut., The compressed air from the compressor reaches the, solenoid valve. The solenoid valve changes the direction of, flow according to the signal from the sensor unit., The pneumatic cylinder is used to clamp the work piece, automatically with the help of IR sensor unit., Advantage, 1 Simple in construction than mechanical hacksaw., 2 It is a compact one, 3 Less maintenance, 4 Fast production, , •, , To achieve mass production in manufacturing process., , •, , To reduce man power employed., , •, , To increase the efficiency of the machine., , •, , Additional cost is required to do the automation., , •, , To reduce the workload & production cost., , •, , Leakage of air affects the working of the unit., , •, , To reduce material handling & production time., , •, , To reduce the fatique of workers., , •, , To achieve good product quality., , •, , To reduce maintenance cost., , 118, , Limitation, , Application, •, , Small and medium scale industries Application., , •, , Metal Cutting Industries and Work Shops., , Copyright @ NIMI Not to be Republished
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Production & Manufacturing, Turner - CNC Turning Operation, , Related Theory for Exercise 4.5.146, , Input and Output of data, Objectives : At the end of this lesson you shall be able to, • understand the importance of input/output data for a CNC, • learn about output data, CNC parameter, • learn about pitch error, custom macro variables., The Input/Output data is very important elements in a CNC, machine. The CNC stores parameters like pitch error, compensation PMC parameter CNC parameters, took, compensation amount etc. The conrtrol of input and output, datas through set of keys and commands are indicated, below., Setting procedure of parameters, Parameter writing is enabled with following steps 1 to 3., 1 Set to MDI mode or emergency stop state., 2 Press function key several times or press soft key, [SETTING] to display SETTING (HANDY) screen., 3 Set the cursor to PARAMETER WRITE and, press and, keys in this order. Here alarm 100 will be displayed., 4 Press function key several times to display the following, screen., →, ⇒, ⇐, , PARAMETER, 0000, , 0, , 0, , (SETTING), SEQ, 0, 0, , 0001, , 0, 0, 0, 0, 0012RMV, X, 0, 0, 0, 0, Y, 0, 0, 0, 0, Z, 0, 0, 0, 0, B, 0, 0, 0, 0, 0020 I/O CHANNEL, , 1234 N12345, , 0, , 0, , 0, , 0, , 0, 0, 0, 0, , 0, 0, 0, 0, , INI ISO TVC, 0 0, 0, FCV, 0 0, 0, MIR, 0 0, 0, 0 0, 0, 0 0, 0, 0 0, 0, S, , REF **** *** ***, [PARAM][DGNOS][, , 0 T0000, , 10: 15: 30, ][SYSTEM][(OPRT)], , To make the cursor display in bit unit, press the cursor key, or ., 5 Press soft key [(OPRT)] and the following operation, menu is displayed., <1> Soft key [NO. SRH] :, Searched by number., Examination) Parameter number, , [NO. SRH]., , <3> Soft key [OFF : 0] :, Item with cursor position is set to 0 (bit parameter), <4> Soft key [+INPUT] :, Input value is added to the value at cursor, <5> Soft key [INPUT] :, Input value is replaced with the value at cursor, <6> Soft key [F INPUT] :, Parameters are input from reader/puncher, interface., <7> Soft key [F OUTPUT] :, Parameters are output to reader/puncher interface., 6 After the parameters have been input, set PARAMETER, WRITE on the SETTING screen to 0. Press key to, release alarm 100., 7 Convenient method, <1> To change parameters in bit unit, press cursor, key or , then the cursor becomes bit length and, you can set parameters bit by bit (Bit parameter, only)., <2> To set data consecutively, use key., (Ex.1), This key sequence sets data as follows:, , (Ex.2), , 0, 0, 0, 0, , ⇒, , 1234, 4567, 9999, 0, , This key sequence sets data as follows:, 0, 1234, 0, 0, 0, 9999, 0, 0, <3> To set the same data sequentially, press = ., (Ex.1), This key sequence sets data as follows:, 0, 1234, 0, 1234, 0, 1234, 0, 0, <4> Bit parameters can be set as follows:, , <2> Soft key [ON : 1] :, Item with cursor position is set to 1 (bit parameter), , Copyright @ NIMI Not to be Republished, , 119
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(Ex.1), This key sequence sets data as follows:, 00000000, 00000000, 00000000, 00000000, 8, , 00011000, 00011000, 00011000, 00000000, , #7, 0101, , NFD, ASI, , After the required parameters are set, set, PARAMETER WRITE to 0., , Inputting/ Oupputting Data, The CNC memorized the following data., , SB2, , Outputting the data I/O device while the CNC is running, normally., 1 CNC parameter, , 0102, , #6, , #5, , #4, , NFD, , #3, , #2, , #1, , ASI, , #0, SB2, , 0: Feed is output when data is output., 1: Feed is not output when data is output., (*) 0: EIA or ISO code is used for input/output, data., (input: automatic detection, output: setting, of bit 1 (ISO) of parameter No. 0000), 1: ASCII code is used., (To use the ASCII code, set bit 1 (ISO) of, parameter No. 0000 to 1. ), 0: No. of stop bits is 1., (*) 1: No. of stop bits is 2., Number specified for the input/output device, , Set value, Input/output device, 0, RS-232-C (Used control codes DC1 to DC4), , 2 PMC parameter, 3 Pitch error compensation amount, 4 Custom macro variable values, 5 Tool compensation amount, , 1, , FANUC CASSETTE ADAPTOR 1 (FANUC, CASSETEE B1/B2), , 2, , FANUC CASSETTE ADAPTOR 3 (FANUC, CASSETEE F1), , 6 Part program (machining program, custom macro, program), , FANUC PROGRAM FILE Mate, FANUC FA, Card Adaptor, FANUC FLOPPY CASSETTE ADAPTOR,, FANUC Handy File, FANUC SYSTEM P-MODEL H, , Conforming the Parameters Reqiured for Data Input/, Output, , 3, , Be sure that data output cannot be done in an alarm, status., , 4, , The following parameters are needed to input/output data, with a reader or puncher:, , RS-232-C (Not used control codes DC1 to, DC4), , 5, , Portable tape reader, , 6, , FANUC PPR, FANUC SYSTEM P-MODEL G, FANUC, SYSTEM P-MODEL H, , In addition, (*) indicates the standard setting for input/, output devices made by FANUC. Change these settings, according to the unit you actually use., (Parameter can be changed in MDI mode or emergency, stop status.), #7, #6, #5, #4 #3, #2 #1 #0, 0000, , ISO, , 0020, , 0: Output with EIA code, 1: Output with ISO code (for RS-232-C serial, port 1 or 2), Selection of I/O channel, , NOTE, In the operation examples in this chapter, data input/output is done with an I/O device connected to, JD36A. (I/O channel = 0), , Baud Rate, , 1: 50, 3: 110, 4: 150, 6: 300, , ISO, , (*) 0: Channel 1 (RS-232-C serial port 1: JD36A, of mainboard), 1: Channel 1 (RS-232-C serial port 1: JD36A, of main board), 2: Channel 2 (RS-232-C serial port 2: JD36B, of main board), 4: Memory card interface, 5: Data Server interface, , 120, , 0103, , #7, , #6, , 7: 600 11: 9600, 8: 1200 12: 19200 [BPS], 9: 2400, (*)10: 4800, #5, , #4, , #3, , #2, , #1, , 0139, , ISO, , ISO, , 0: ASCII code input/output, 1: ISO code input/output (with memory card), #7, , #6, , #5, , #4, , 0908, , ISO, , #0, , #3, , #2, , #1, , #0, ISO, , 0: ASCII code input/output, 1: ISO code input/output (with Data Server), , Outputting CNC Parameters, 1 Enter EDIT mode or the emergency stop condition., , 2 Press function key and soft key [PARAMETER] to, select a parameter screen., Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.5.146, , Copyright @ NIMI Not to be Republished
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3 Press soft key [(OPRT)] and continuous menu key ., 4 Press soft keys [F OUTPUT] and [EXEC], and the, parameters are started to be output., Outputting Pitch Error Compensation Amount, If pitch error compensation is enabled, a pitch error, compensation amount is output., 1 Select EDIT mode., 2 Press the function key ., 3 Press continuous menu key several times, then press, soft key [PITCH] to select the pitch error compensation, setting screen., 4 Press soft key [(OPRT)] and continuous menu key ., 5 Press soft keys [F OUTPUT] and [EXEC], then pitch, error compensation amount is started to be output., Outputting Custom Macro Variable Values, When custom macro function is valid, values of variable, No. 500 and later are output., 1 Press function key ., 2 Press continuous menu key several times, then press, soft key [MACRO] to select custom macro variable, screen., 3 Press soft key [(OPRT)] and then continuous menu, key., 4 Press soft keys [F OUTPUT] and [EXEC], then custom, macro variable values are output., , NE8 (*) 0: Programs of 8000s are edited., 1: Programs of 8000s can be protected., (Protected programs are not output.), 2 Select EDIT mode., 3 Press the function key and then the soft key, [PROGRM] to select the program content display, screen., 4 Press soft key [(OPRT)] and press continuous menu, key ., 5 Input a program number to be output. To output all, programs input as:, 6 Press soft keys [F OUTPUT] and [EXEC], then program, output is started., Inputting CNC Parameters, 1 Set to the emergency stop state., 2 Press the function key and then the soft key [SETTING], to select the setting screen. Confirm “PARAMETER, WRITE=1” on the setting screen., 3 Press function key and soft key [PARAMETER] to, select the parameter screen., 4 Press soft key [(OPRT)] and continuous menu key ., 5 Press soft keys [F INPUT] and [EXEC]. Then input of, parameters are started., 6 Upon completion of parameter input, turn off the power, then turn on the power again., , Outputting Tool Compensation Amount, , 7 Alarm 300 is issued if the system employs an absolute, pulse coder. In such a case, perform reference position, return again., , 1 Select EDIT mode., , Inputting Pitch Error Compensation Amount, , 2 Press function key and soft key [OFFSET] to display, the tool compensation amount screen., , If pitch error compensation is enabled, a pitch error, compensation amount is input., , 3 Press soft key [(OPRT)] and continuous menu key ., , 1 Select EDIT mode., , 4 Press soft keys [F OUTPUT] and [EXEC], and the, tool compensation amount is started to be output., , 2 Confirm that PARAMETER WRITE=1 on the setting, screen., , Outputting Part Program, , 3 Press the function key ., , 1 Confirm the following parameters. If their setting does, not match those indicated with the asterisk, select, the MDI mode and re-set them and keep them re-set, only while this work is being done., , 5 Press soft key [(OPRT)] and continuous menu key., , However, if you changed the parameter setting, restore, the original value after finishing this work., #7, 3202, , #6, , #5, , #4, , #3, NE9, , #2, , #1, , #0, NE8, , NE9 (*) 0: Programs of 9000s are edited., 1: Programs of 9000s can be protected., (Protected programs are not output.), , 4 Press continuous menu key several times, then press, soft key [PITCH] to select the pitch error compensation, setting screen., 6 Press soft keys [F INPUT] and [EXEC], then pitch, error compensation amount is started to be input., 7 After a pitch error compensation amount is input,, display the setting screen and reset “PARAMETER, WRITE” to “0” on the setting screen., Inputting Custom Macro Variable Values, When custom macro function is valid, input the variable, values., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.5.146, , 121
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1 Select EDIT mode., 2 Turn off the program protect (KEY2=1)., 3 Press the function key ., 4 Press continuous menu key several times, then press, soft key [MACRO] to select the custom macro variable, screen., 5 Press soft key [(OPRT)] and continuous menu key., 6 Press soft keys [F INPUT] and [EXEC], then custom, macro variable values is started to be input., Inputting Tool Compensation Amount, , #7, 3201, , 2 Turn off the program protect (KEY=1)., 3 Press the function key ., 4 Press soft key [OFFSET] to display the tool, compensation amount display screen., 5 Press soft key [(OPRT)] and continuous menu key., 6 Press soft keys [F INPUT] and [EXEC], then tool, compensation amount is started to be input., Inputting Part Programs, 1 Confirm the following parameters. If their setting does, not match those indicated with the asterisk, select, the MDI mode and re-set them and keep them re-set, only while this work is being done., , #6, , #5, , #4, , #3, , #2, , NPE, , #1, , #0, , RAL, , NPE When programs are registered in part program, storage area, M02,M30 and M99 are:, 0: Regarded as the end of program., (*) 1: Not regarded as the end of program., RAL When programs are registered:, (*) 0: All programs are registered., 1: Only one program is registered., #7, , 1 Select EDIT mode., , 122, , However, if you changed the parameter setting, restore, the original value after finishing this work., , #6, , 3202, , #5, , #4, , #3, , #2, , #1, , NE9, , #0, NE8, , NE9 (*) 0: Programs of 9000s can be edited., 1: Programs of 9000s are protected., NE8 (*) 0: Programs of 8000s can be edited., 1: Programs of 8000s are protected., 2 Select EDIT mode., 3 Turn off the program protect (KEY3=1)., 4 Press the function key and then the soft key, [PROGRM] to select the program content display, screen., 5 Press soft key [(OPRT)] and press continuous menu, key ., 6 Press soft keys [F INPUT] and [EXEC], then program, input is started., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.5.146
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Production & Manufacturing, Turner - CNC Turning Operation, , Related Theory for Exercise 4.5.147, , DNC system, Objectives : At the end of this lesson you shall be able to, • learn about the DNC system, • learn type the DNC system, • understand the advantage of DNC., DNC System, It is a manufacturing system in which number of machines, are controlled by a computer through direct-connection, and in realtime. It is also a system connecting to a set of, NC. Machines to common memory for a part programme, or machine programme storage with provision of, on-demand distribution of data to machines., The main components of a DNC are;, 1 Central computer., 2 Bulk memory with storage of part programme., 3 Telecommunication lines and set of NC machine tools., A schematic sketch indicating a set of NC machine, connected to a DNC is shown below:, , instruction to machine tools. The cost of BTR system is, very less. The special machine control unit replace a, regular controler, with the control unit capable of facilating, communication between machine tool and computer. This, system achives very high accuracy of interpolation and fast, metal removal rate., Functions of DNC, The function of DNc system is to perform., 1 NC with out punched tape., 2 NC part programme storage., 3 Data collection, processing and reporting., 4 Communication., A communication Network accomplishes the previous, functios of DNC. This links DNC with central computer and, machine tools, Central computer and NC part programmer, terminal, central computer and Bulk Memory., Advantages of DNC system, It eliminates punched tape and tape reader., It is convenient to store are NC part programme in computer, files., It has greater computational capability and flexibility., It can report the shop performance at the click of a button., DNC’s are very convenient in editing and dignoistic feature., , There are two types of DNC machines namely 1. Behind, the Tape Reader System (BTR), 2. Special Machine, Control Unit (MCU). In BTR system computer is linked, directly to NC controler unit the operation of the system is, very similar to conventional NC. The controler unit, uses, two temporery storage buffer to receive instruction from, DNC computer and convert them in to machine action. One, buffer receives Data the other is providing controlling, , DNC is a first step in the development of production plant, automated with computer., , Copyright @ NIMI Not to be Republished, , 123
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Production & Manufacturing, Turner - CNC Turning Operation, , Related Theory for Exercise 4.5.148, , Use of CAM Programme, Objectives : At the end of this lesson you shall be able to, • understand usefulness of CAM in manufacturing process, • learn the output format of CAM programe, • understand terms like CAD/CAE/DNC etc., Introduction:, , Usefulness of CAM, , Computer-aided manufacturing (CAM) is the use of a, software to control machines and the related devices &, equipment in the manufacture of components. CAM software, also assist in all operations such as process planning,, production management, product transportation within the, plant, storage of semi finished/finished product., , Good CAM software is equally as important to manufacturers, as the powerful machines and tool they use to cut desired, parts. Machine shops of all sizes and budgets are reaping, benefits of good CAM software beyond efficiency, programming their machining jobs. Users can structure, their job, set their Toolpath, then use the simulation, function to make sure their plan goes accordingly. Part, gouges or collisions can potentially ruin a very crucial and, expensive CNC machine, threatening to affect that shop’s, profitablilty or ability to take on additional projects. It is, much easier to readjust a Toolpath in the CAM software, than it is to fix or repalce a CNC machine!, , The purpose of CAM is to increase productivity and improve, tooling, to enhance greater consistency of quality,, minimising raw material wastage. CAM software is also, useful for training & academic educational purposes., CAM process has come out of CAD and sometimes CAE, computer aided engineering, as a model generated by, CAD, verfied by CAE and put into CAM software, which, controls the CNC machine tool, CAM is a numerical control (NC) programming tool, for 2D/, 3D models generated in CAD. CAM does not eliminate the, need for skilled professionals, but assists manufacturing, personnel in building skills through visualisation, simulation, and optimization tools. Integration of CAD with other, components of CAD/CAM/CAE, Product Life Cycle (PLC), management environment requires an effective CAD data, exchange, such as IGES/STL/ Parasolid formats. The, output from CAM is usually a text file of G-code/M-code,ad, thousands of commands, which can be transfered to a, DNC programme., CAM is specifically effective in typical areas like., •, , High speed machining, streamlining tool paths., , •, , Multifunction machining., , •, , 5-axis machining & Automatic machining., , A finished components has to undergo different machining, process in its conversion from raw material i.e,, a Rough machining: From raw stock,raw casting passes, through zig-zag clearing, plunge roughing, rest roughing,, trohoidal milling aiming at maximum material removal, in the least amount of time, maintaining dimensional, accuracy., b Semi-finishing: In this process, small amount of material, only removed, to enable the tool to cut accurately such, as Raster passes, constant step-over process, pencil, milling etc., c Finishing machining: It involve very light material removal, to produce polished finish product. The feed is increased, to target SFM with high speed refered as highspeed, machining (HSM) CAM is mainly useful for contour, milling on four or more axis., 124, , Structuring your job with CAM Software, Let’s take s sprocket for example. You created your, sprocket using CAD software, now how will you make it?, CAM software looks at what designed& determines how to, machine it out of materials. For starters, most CAM, software products provide a standard “Job Tree” for, machining strategy organization. Then you will need to set, up and save the features of the machine from your shop, within the CAM software. This is important for developing, programs that are specific to your machine, allowing you, to easily machine future projects, editing machine setting, as needed. Next, you will identify your stock, allowing you, to set initial work cooridinates, material type and the tools, to be used during machining. Lastly, you set your cutting, conditions, tool patterns, tool crib and tool holder for errorfree CNC programming. One of the greatest benefits of, CAM software is the ability to save the information you put, in the system, making future projects much more easily, programmed., Setting your Toolpaths within the CAM software:, Once you have your starting points clearly identified, (machine, tools and stock), you can move into the next, phase of developing your machining operations. Start with, your stock. Decide the toolpaths for your roughing and, finishing cycles that will ultimately determine your desired, part design. Your Job Tree comes into play now, keeping, your machining operations organized and correctly, sequenced. CAD-CAM software, like that from BobCADCAM, used wizard guides that act as a series of dialog, boxes that walk you through the process step-by-step until, your Toolpath is properly created. Wizards are sort of a, fool-proof way to make sure all your information is entered, in correctly, reducing programming time significantly for, users., , Copyright @ NIMI Not to be Republished
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After you created a Toolpath for each of your operations,, you can move into most critical aspect of CAM software;, simulation. This allows you to see your machine create, your part in a digital environment. There are three major, things that are being accomplished during the time:, 1 Part deviation analysis- the CAM software identified, what’s not cut by the tool or where the tool went too, deep using multiple colors to represent different levels, of deviation., , After you structure your job, creat your Toolpath and run, simulations to satisfaction, you are ready for post, processing. This is the final step before your part is, machined. G-code is created by the CAM software, which, is the NC file that is read by the CNC machine. Think of the, G-code as the GPS in your car; it basically tells the, machine where to go. Each machine’s G-code can vary, so, it’s important you have the proper post processor added to, your CAM software., , 2 Costly gauges or collisions are digitally detected prior, to engaging your shop’s machine., 3 Cycle time can be easily calculated., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.5.148, , 125
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Production & Manufacturing, Turner - Advanced Turning, , Related Theory for Exercise 4.6.149, , Setting of tool for taper threads calculation of taper setting and thread depth., Objectives : At the end of this lesson you shall be able to, • state the application of taper thread, • state the methods of producing taper threads, • describe methods of turning tapers on a lathe with its merits and demerits., Taper thread, , -, , Taper threads are used on fasteners and pipe. A, common example of a fastener with a taper thread is wood, screw. The threaded pipes used in some plumbing, installations for the delivery of fluids under pressure have, a threaded section that is slightly conical. Examples are, NPT and BSP series. The seal provided by a threaded, pipe joint is created when a tapered externally threaded, into an end with internal threads., Inside tapered threads, -, , Insert the pipe into the chuck of the lathe and tighten, down the chucks with an Allen wrench. Install the tap, in the opposite chuck of the lathe. Move the ram forward, until the tapping tool reaches the inside of the pipe., Center the tapping tool to the interior of the pipe., , -, , Start the ram and slowly close the tapping tool., Lubricate the tapping tool periodically with metal cutting, fluid as it machines the tapered threads. Reverse the, ram of the lathe and slowly back the tapping tool out of, the interior of the pipe. Check the tapered threads with, a thread gauge., , -, , Set the steel plate, with holes drill holes, on the base, plate of the drill press and secure it in place. Insert a, tapping tool in the chuck of the drill press and secure, with a chuck tool. Fill the drilled hole with metal cutting, fluid and slowly lower the tapping tool. Align the tapping, tool before machining the tapered threads., , Cutting taper thread, Whereas the axial moment required for pitch feed is, provided by the machine, the radial moment required in, addition for producing a tapered thread is obtained by the, tool slide feed. Do not clamp the slide by tightening locking, screw .During thread cutting both the machine feed and, the feed of the head must be in continuous engagement., Same as per taper turning ,the sensitiveness to release of, retaining pin must be reduced to the minimum by means, of regulating screw stop rod must not be displaced by, changing over from clockwise to anti-clockwise rotation, from the position held., Depending on the pitch of thread, taper angles will vary, with varying cross feeds. The tool mounting and depth, adjustment are same as taper turning attachment method., The method of operation is the same as for straight thread, cutting., The taper for the taper thread is prepared by using normal, taper turning attachment methods., Tapers may be produced by any conventional methods, according to the requirement and die sets are also used, for producing taper threads., Tailstock offset method (Fig 1), , Outside tapered threads, -, , Insert the pipe in the lathe's chuck and secure it in, place, similar to the way you secured the pipe when, machining inside tapered threads. Open the mouth of, the opposite chuck and insert a threading die, instead, of attaching a tapping tool to the opposite chuck., Tighten down the chuck. Align the threading die with, the outside of the pipe., , -, , Cover both the end of the pipe and the interior of the, die with metal cutting fluid .Start the lathe and close, the ram slowly until it starts machining the tapered, threads. Pour more cutting fluid on the end of the pipe, as you continue to close the ram of the lathe. Reverse, the lathe ram after reaching the desired thread depth., Checks the threads with the thread gauge., , 126, , Insert the screw, bold or rod in the chuck of the lathe., Install a threading die in the opposite chuck of the lathe, and machine the tapers threads, similar to the way, you cut the threads on the outside of the pipe., , Copyright @ NIMI Not to be Republished
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In this method the job is held at an angle and the tool, moves parallel to the axis. The body of the tailstock is, shifted on its base to an amount corresponding to the, angle of taper., Tail stock set over (Fig 2), , Calculation of Thread depth formula., BSN, , - 0.6403 x Pitch, , Metric - 0.6134 x Pitch, Square - 0.5 x Pitch, Acme - 0.5 x Pitch, B.A - 0.6134 x Pitch, Buttress - 0.75 x Pitch, Worm thread - 0.68 x Pitch, Taper turning by attachment (Fig 3), This attachment is provided on a few modern lathes. Here, the job is held parallel to the axis and the tool moves at an, angle. The movement of the tool is guided by the, attachment., , Taper, Tapers may be produced by any conventional methods, according to the requirement and die sets are also used, for producing taper threads., The taper can be turned between centres only and this, method is not suitable for producing steep tapers.The, amount of offset is found by the formula. (Fig 3), Offset =, , Taper angle is found by formula (Fig 3), , Tanφ =, , D−d, 2l, , (D − d) XL, 2l, , where, , D = big dia. of taper, d = small dia. of taper, l = taper length, L = total length of job, , Advantages, Power feed can be given, good surface finish can be obtained, maximum length of the taper can be produced, external thread on taper portion can be produced, , Advantages, Both internal and external tapers can be produced., , duplicate tapers can be produced, , Threads on both internal and external taper portions can, be cut., , Disadvantages, , Power feed can be given., , only external taper can be turned, , lengthy taper can be produced., , accurate setting of the offset is difficult, , Good surface finish is obtained, , taper turning is possible when work is held between centres only., , The alignment of the lathe centres is not disturbed., , damages the centre drilled holes of the work., , It is most suitable for producing duplicate tapers because, the change in length of the job does not affect the taper., , the alignment of the lathe centres will be disturbed, , The job can be held either in chuck or in between centres, , steep tapers cannot be turned, , Disadvantage, only limited taper angles can be turned., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.149, , 127
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Heat treatment of plain carbon steels, Objectives : At the end of this lesson you shall be able to, • state the purpose of heat treatment of steel, • state the types of structure, constituents and properties of plain carbon steels., Heat treatment and its purpose, , Structure of steel when heated (Fig 2), , The properties of steel depend upon its composition and its, structure. These properties can be changed to a, considerable extent, by changing either its composition or, its structure. The structure of steel can be changed by, heating it to a particular temperature, and then, allowing it, to cool at a definite rate. The process of changing the, structure and thus changing the properties of steel, by, heating and cooling, is called ‘heat treatment of steel’., Types of structure of steel (Fig 1), , If steel is heated, a change in its structure commences, from 723° C. The new structure formed is called, ‘AUSTENITE’. Austenite is non-magnetic. If the hot steel, is cooled slowly, the old structure is retained and it will have, fine grains which makes it easily machinable., , The structure of steel becomes visible when a piece of the, metal is broken. The exact grain size and structure can be, seen through a microscope. Steel is classified according, to its structure., steel is an alloy of iron and carbon. But the carbon content, in steel does not exceed 1.7%., Ferrite, Pig iron or steel with 0% carbon is FERRITE which is, relatively soft and ductile but comparatively weak., Cementite, When carbon exists in steel as a chemical compound of, iron and carbon it is called ‘iron carbide’or CEMENTITE.This, alloy is very hard and brittle but it is not strong., Eutectoid/Pearlite steel, , If the hot steel is cooled rapidly the austenite changes into, a new structure called “MARTENSITE’. This structure is, very fine grained, very hard and magnetic. It is extremely, wear-resistant and can cut other metals., Heat treatment processes and purpose, Because steel undergoes changes in structure on heating, and cooling, its properties may be greatly altered by, suitable heat treatment., The following are the various heat treatments and their, purposes., Hardening, , To increase wear resistance, Tempering:, , To remove extreme brittleness, caused by hardening to an extent., To induce toughness and shock, resistance, , Annealing:, , A 0.84% carbon steel or eutectoid steel is known as, PEARLITE steel. This is much stronger than ferrite or, cementite., , To relieve strain andstress, To eliminate strain/hardness, To improve machinability, To soften the steel, , Hypereutectoid steel, More than 0.84% carbon steel or hypereutectoid steel is, pearlite and cementite., 128, , To add cutting ability, , Normalising:, , To refine the grain structure of, the steel, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.149
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Hardening of carbon steel, Objectives : At the end of this lesson you shall be able to, • state the hardening of steel, • state the purpose of hardening steel, • state the process of hardening., What is hardening?, Hardening is a heart-treatment process in which steel is, heated to 30-50° C above the critical range, smoking time, is allowed to enable the steel to obtain a uniform, temperature throughout its cross-section. Then the steel, is rapidly cooled through a cooling medium., Purpose of hardening, To develop high hardness and wear-resistance properties., Hardening affects the mechanical properties of steel-like, strength, toughness, ductility etc., Hardening adds cutting ability., Process of hardening, Steel with a carbon content above 0.4% is heated to 3050°C above the upper critical temperature. (Fig1) A soaking, time of 5mts./10 mm thickness of steel is allowed. (Fig 1), , Then the steel is cooled rapidly in a suitable medium., Water, oil, brine or air is used as a cooling medium,, depending upon the composition of the steel and the, hardness required., , Tempering the hardened steel, Objectives : At the end of this lesson you shall be able to, • state what is tempering, • state the purpose of tempering, • relate the tempering colours and temperatures with the tools to be tempered, • state the process of tempering of steels., What is tempering?, , -, , to decrease the brittleness, , Tempering is a heat-treatment process consisting of, reheating the hardened steel to a temperature below 400°C,, followed by cooling., , -, , to restore some ductility, , -, , to induce shock resistance, , Purpose of tempering the steel, Steel in its hardened condition is generally too brittle to be, used for certain functions. Therefore, it is tempered., The aims of tempering are:, -, , to relieve the internal stresses, , -, , to regulate the hardness and toughness, , Process of tempering the steel, The tempering process consists of heating the hardened, steel to the appropriate tempering temperature and soaking, at this temperature, for a definite period., The period is determined from the experience that the full, effect of the tempering process can be ensured only, if the, tempering period is kept sufficiently long. Table 1 shows, the tempering temperature and the colour for different tools., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.149, , 129
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TABLE 1, Tools or, articles, , Temperature, in degrees (ºC), , Turning tools, Drills and, milling cutters, Taps and shear, blades, Punches,, reamers, twist, drills, Rivets,snaps, Press tools,, cold chisels, Cold set for, cutting steels, Springs, screw, drivers, , For toughening, without undue, hardness, , Colour, , 230, , Pale straw, , 240, 250, , Dark straw, Brown, , 260, 270, , Reddish brown, Brown purple, , 280, , Dark purple, , 290, , Light blue, , 300, 320, 340, , Dark blue, Very dark blue, Greyish blue, , 450-700, , No colour, , Annealing of steel, Objectives : At the end of this lesson you shall be able to, • state the purpose of annealing, • state the process of annealing., The annealing process is carried out by heating the steel, above the critical range, soaking it for sufficient time to, allow the necessary changes to occur, and cooling at a, predetermined rate, usually very slowly, within the furnace., Purpose, -, , To soften the steel, , -, , To improve the machinability, , -, , To increase the ductility, , -, , To relieve the internal stresses, , -, , To refine the grain size and to prepare the steel for, subsequent heat treatment process, , Annealing process, Annealing consists of heating of hypoeutectoid steels to 30, to 50°C above the upper critical temperature and 50°C, above the lower critical temperature for hypereutectoid, steels. (Fig 1), , 130, , Soaking is holding at the heating temperature for 5 mts/, 10mm of thickness for carbon steels., The cooling rate for carbon steel is 100 to 150°C/hr, Steel, heated for annealing, is either cooled in the furnace, itselfby switching off the furnance or its covered with dry, sand, dry lime or dry ash., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.149
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Normalising of steel, Objectives : At the end of this lesson you shall be able to, • state the meaning of normalising steel and its purpose, • state the process of normalising steel, • state the precaution to be taken while normalising steel., The process of removing the internal defects or to refine the, structure of steel component is called normalising., Purpose, -, , To produce fine grain size in the metal, , -, , To remove stresses and strains formed in the internal, structure due to repeated heating and uneven cooling or, hammering, , -, , To reduce ductility, , -, , To prevent warping, , Process, To get the best results from normalising, the parts should, be heated uniformly to a temperature of 30 to 40°C above, the upper critical temperature (Fig1), followed by cooling in, still air, free from drought, to room temperature. Normalizing, should be done in all forgings, castings and work-hardened, pieces., , Precautions, Avoid placing the component in a wet place or wet air,, thereby restricting the natural circulation of air around the, component. Avoid placing the component on a surface that, will chill it., , Heating / Quenching steel for heat treatment, Objectives : At the end of this lesson you shall be able to, • differentiate between the lower critical and the upper critical temperatures, • state the three stages in the heat treatment process, • determine the upper critical temperature for different carbon steels from the diagram., Critical Temperatures, Lower critical temperature, The temperature, at which the change of structure to, austenite starts-723°C, is called the lower critical, temperature for all plain carbon steels., Upper critical temperature, The temperature at which the structure of steel completely, changes to AUSTENITE is called the upper critical, temperature. This varies depending on the percentage of, carbon in the steel. (Fig 1), Example, 0.57% and 1.15% carbon steel: In these cases the lower, critical temperature is 723°C and the upper critical, temperature is 800°C., , Three stages of heat treatment, , For 0.84% carbon steel, both LCT and UCT are 723°C. This, steels is called eutectoid steel., , -, , Heating, , -, , Soaking, , -, , Quenching, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.149, , 131
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When the steel on being heated reaches the required, temperature, it is held in the same temperature for a period, of time. This allows the heating to take place throughout the, section uniformly. This process is called soaking., , The most widely used quenching media are:, , Soaking time, This depends upon the cross-section of the steel, its, chemical composition, the volume of the change in the, furnace and the arrangement of the charger in the furnace., A good general guide for soaking time in normal conditions, is five minutes per 10mm of thickness for carbon and low, alloy steels, and 10 minutes per 10 mm of thickness for, high alloy steels., Heating steel, This depends on the selection of the furnace, the fuel used, for heating, the time interval and the regulation in bringing, the part up to the required temperature. The heating rate, and the heating time also depend on the composition of the, steel, its structure, the shape and size of the part to be, heat-treated etc., Preheating, Steel should be preheated at low temperature up to 600°C, as slowly as possible., Quenching, , -, , brine solution, , -, , water, , -, , oil, , -, , air, , Brine solution gives a faster rate of cooling while air cooling, has the slowest rate of cooling., Brine solution (Sodium chloride) gives severe quenching, because it has a higher boiling point than pure water, and, the salt content removes the scales formed on the metal, surfaces due to heating. This provides a better contact with, the quenching medium and the metal being heat-treated., Water is very commonly used for plain carbon steels., While using water as a quenching medium, the work, should be agitated. This can increase the rate of cooling., The quenching oil used should be of a low viscosity., Ordinary lubricating oils should not be used for this, purpose. Special quenching oils, which can give rapid and, uniform cooling with less fuming and reduced fire risks, are, commercially available. Oil is widely used for alloy steels, where the cooling rate is slower than plain carbon steels., Cold air is used for hardening some special alloy steels., , Depending on the severity of the cooling required, different, quenching media are used., , Induction hardening, Objectives : At the end of this lesson you shall be able to, • state the process of the induction hardening method, • state the advantages of the induction hardening process., Induction hardening, This is a production method of surface-hardening in which, the part to be surface-hardened is placed within an induction, coil through which a high frequency current is passed., (Fig 1) The depth of penetration of the heating becomes, less, as the frequency increases., , The depth of hardening for high frequency current to, 1.0mm. The depth of hardening for medium frequency, current is 1.5 to 2.0 mm. Special steels and unalloyed, steels with a carbon content of 0.35 to 0.7% are used., After induction-hardening of the workpieces, stress, relieving is necessary., The following are the advantages of this type of hardening, , 132, , -, , The depth of hardening, distribution in width and the, temperature are easily controllable., , -, , The time required and distortion due to hardening are, very small., , -, , The surface remains free from scales., , -, , This type of hardening can easily be incorporated in, mass production., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.149
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Carburising of steel, Objectives: At the end of this lesson you shall be able to, • state the process of pack carburising, • state the process of liquid carbursing, • state the process of gas carburising., Pack carburising (Fig.1), The parts are packed in a suitable metal box in which they, are surrounded by the carburising medium, such as wood,, bone, leather or charcoal, with barium carbonate as an, energiser., , about 0.9% carbon, and the core will still contain 0.15%, carbon. There will be a gradual transition carbon content, between the case and the core. (Fig 2), , The lid is fitted to the box and sealed with fireclay and tied, with a piece of wire so that no carbon gas can escape and, no air can enter the box to cause de-carburisation., , Owing to the prolonged heating, the core will be coarse and, in order to produce a reasonable toughness, it must be, refined., To refine the core, the carburised steel is reheat about 870°, C and held at that temperature long enough to produce a, uniformitly of structure, and is then rapidly to prevent grain, growth during cooling., The temperature of this heating is much higher the suitable, for the case, therefore, an extremly brittle martensite will be, produced., , Liquid carburising, Carburising can be done in a heated salt bath. (Sodium, carbonatte,sodium cyanide and barium chloride are typical, carburising salts). For a constant time and temperature of, carburising, the depth of the case depends on the cyanide, content., , The case and the outer layers of the core must be refined., , This is suitable for a thin case, about 0.25 mm deep. Its, advantage is that heating is rapid and distortion is minimised,, and it is suitable for batch production., , Finally the case is tempered at about 200° C to relive, quenching stresses., , Gas carburising, , The refining is done by reheating the steel about 760º to suit, the case, and quenching it., Tempering, , Fig 3 illustrates the apperance of the structure across its, section produced by case hardening., , The work is placed in a gas-tight container which can be, heated in a suitable furnace, or the furnace itself may be the, container., The carburising gas ‘methane or propane’s is admitted to, the container, and the exit gas is vented., Fig 2 illustrates the appearance of the structure across its, section produced by carburising., Heat treatment, After carburising has been done, the case will contain, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.149, , 133
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Nitriding, Objectives: At the end of this lesson you shall be able to, • state the process of case hardening by gas nitriding, • state the process of case hardening by nitriding in a salt bath., In the nitriding process, the surface is enriched not with, carbon, but with nitrogen. There are two systems in, common use, gas nitriding and salt bath nitriding., Gas nitriding, The gas nitriding process consists of heating the parts at, 500°C in a constant circualtion of ammonia gas for up to, 100 hours and cooling them in air., Nitriding in salt bath, Special nitriding baths are used for salt-bath nitriding. This, process is suitable for all alloyed and unalloyed types of, steel, annealed or not annealed, and also for cast iron., Process, The completely stress-relieved workpieces are preheated, (about 400°C) before being put in the salt bath (about 520570°C). A layer 0.01to 0.02mm thick is formed on the, surface which consists of a carbon and nitrogen compound., The duration of nitriding depends on the cross-section of, the workpieces (half an hour to three hours). It is much, shorter than for gas nitriding. After being taken out of the, , 134, , bath, the workpieces are quenched and washed water and, dried., Advantages, The parts can be finish-machined before nitriding because, no quenching is done after nitriding, and, therefore, they will, not suffer from quenching distortion., In this process, the parts are not heated above the critical, temperature, and, hence warping or distortion does not, occur., The hardness and wear-resistance are exceptional. There, is a slight improvement in corrosion resistance as well., Since the alloy steels, used are inherently strong when, properly heat-treated, remarkable combinations of strength, and wear-resistance are obtained., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.149
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Production & Manufacturing, Turner - Advanced Turning, , Related Theory for Exercise 4.6.150, , Interchangeability meaning, procedure for adoption,quality control procedure, for quality production, Objectives : At the end of this lesson you shall be able to, • state the terms used under the BIS system of limits and fits, • define each term under the BIS system of limits and fits., Size, It is a number expressed in a particualr unit in the, measurement of length., , Maximum limit of size, It is the greater of the two limits of sizes.(Fig 2) (Table 1), Minimum limit of size, , Basic size, It is the size based on which the dimensional deviations, are given. (Fig 1), , It is the smaller of the two limits of size.(Fig 2) (Table 1), Table 1, (Examples), Sl. Size of, Upper, Lower, Max.limit Min limit, No. component deviation deviation of size, of size, 1 20, , 2 20, , 3 20, , +.008, -.005, , + 0.008, , - 0.005, , 20.008, , 19.995, , +.007 + 0.028, , - 0.007, , 20.028, , 20.007, , - 0.021, , 19.988, , 19.979, , +.028, , -.012, -.021, , + 0.012, , Hole, In ths BIS system of limits and fits, all internal features of, a component including those which are not cylindrical, are designated as hole. (Fig 3), , Actual size, It is the size of the component by actual measurement, after it is manufactured. It should be lie between the two, limits of size if the component is to be accepted., Limits of size, These are the extreme permissible sizes within which the, operator is expected to make the component. (Maximum, and minimum limits) (Fig 2), , Shaft, In the BIS system of limits and fits, all external features, of a component including those which are not cylindrical, are designated as shaft (Fig 3), Deviation, It is the algebraic difference between a size and its, corresponding basic size. It may be positive, negative or, zero.(Fig 2), , Copyright @ NIMI Not to be Republished, , 135
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Upper deviation, It is the algebraic difference between the maximum limit, of size and its corresponding basic size.(Fig 2) (Table 1), Lower deviation, It is the algebraic difference between the minimum limit of, size and its corresponding basic size.(Fig 2) (Table 1), Upper deviation is the deviation which gives the maximum, limit of size. Lower deviation is the deviation which gives, the minimum limit of size., Actual deviation, It is the algebraic difference between the actual size and, its corresponding basic size. (Fig 2), , The position of tolerance zone with respect to the zero, line is shown in Figs 6 and 7., , Tolerance, It is the difference between the maximum limit of size and, the minimum limit of size. It is always positive and is, expressed only as a number without a sign.(Fig 2), Zero line, In the graphical representation of the above terms, the, zero line represents the basic size. This lines is also called, the line of zero deviation .(Figs1 and 2), Fundamental deviation, There are 25 fundamental deviations in the BIS system, represented by letter symbols (capital letters for holes, and small letters for shafts),i.e. for holes-ABCD----Z, excluding I,L,O,Q and W. (Fig 4), , The fundamental deviations are for achieving the different, classes of fits.(Figs 8 & 9), , In addition to the above, four sets of letters JS, ZA, ZB and, ZC are included., For shafts, the same 25 letter symbols but in small letters, are used.(Fig 5), , 136, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.150
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Fundamental tolerance, This is also called ‘grade of tolerance’. In the B.I.S. system,, there are 18 grades of tolerances represented by number, symbols both for hole and shaft, denoted as IT01, IT0, IT1,, IT2 ______ IT16 (Fig 10), , A very wide range of selection can be made by the, combination of the 25 fundamental deviation and grades of, tolerance., Example, In figure 13, a hole is shown as 25± 0.2which means that, 25mm is the basic dimension and ± 0.2 is the deviation., As pointed out earlier, the permissible variation from the, basic dimension is called ‘DEVIATION’., The deviation is mostly given on the drawing with, dimensions., In the example, 25± 0.2 is the deviation of the hole of 25mm, diameter. (Fig 13) This means that the hole is of acceptable, size if its dimension is between., , A higher number gives a larger tolerance., , 25±0.2=25.2 mm; or 25-0.2=24.8 mm, , Grade tolerance refers to the accuracy of, manufacture., In a standard chart, the upper and lower deviations for, each combination of fundamental deviation and, fundamental tolerance are indicated for sizes ranging up, to 500mm. (Refer to IS 919). An extract up to 500 mm is, gien in Table 2., Tolerance size, This includes the basic size, the fundamental deviation, and the grade of tolerance., Examples, , 25.2mm is the maximum limit. (Fig 14), , 25H7-is the tolerance size of a hole whose basic size is, 25. The fundamental deviation is represented by the letter, symbol H and the grade of tolerance is represented by, the number symbol 7.(Fig 11), 25 e8 - is the tolerance size of a shaft whose basic size is, 25. The fundamental deviation is represented by the letter, symbol and the grade of tolerance is represented by the, number 8. (Fig 12), , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.150, , 137
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24.8 mm is the minimum limit (Fig 15), , The difference between the maximum and minimum limits, is the TOLERANCE. Tolerance here is 0.4 mm. (Fig 16), , All dimensions of the hole within the tolerance zone are of, an acceptable size as shown in Fig 17., , As per IS 696, while dimensioning the components as a, drawing convention, the deviations are expressed as, tolerance., , Fits and their classification as per the Indian standard, Objectives : At the end of this lesson you shall be able to, • define ‘fit’ as per the Indian standard, • list out the terms used in limits and fits as per the Indian standard, • state examples for each class of fit, • define the graphical representation of different classess of fits., Fit, It is the relationship exists between two mating parts, a, hole and a shaft, with respect to their dimensional, differences before assembly., Expression of a fit, A fit is expressed by writing the basic size of the fit first,, (the basic size which is common to both the hole and the, shaft) followed by the symbol for the hole, and the symbol, for the shaft., , Example, , Example, , 20 H7 / g6, , H7, 30 H7 / g6 or 30 H7 - g6 or 30 g6, , With the fit given, we can find the deviations from the chart., , Clearance, In a fit the clearance is the difference between the size of, the hole and the size of the shaft, when the hole is bigger, than the shaft., Clearance fit, , For a hole 20 H7 we find in table 2, + 21., These numbers indicate the deviations in microns., (1 micrometer = 0.001 mm), The limits of the hole are 20+0.021=20.021mm and, 20+0=20.000mm. (Fig 2), , for a shaft 20 g6 we find in the Table - 7, - 20, It is a fit which always provides clearnace. Here the, tolerance zone of the hole will be above the tolerance zone, of the shaft. (Fig 1), 138, Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.150, , Copyright @ NIMI Not to be Republished
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Interference, It is the difference between the size of the hole and the, shaft before assembly, and this is negative. In this case,, the shaft is always larger than the hole size., Interference fit, It is fit which always provides interference. Here the, tolerance zone of the the hole will be below the tolerance, zone of the shaft. (Fig 5), So the limits of the shaft are, 20 - 0.007 = 19.993 mm, and, , 20 - 0.020 = 19.980 mm. (Fig 3), , Maximum clearance, In a clearance fit or transition fit, the maximum clearance, is the difference between the maximum size hole and the, minimum size shaft. (Fig 4), , Example, Fit 25 H7 / p6 (Fig 6), , The limits of the hole are 25.000 and 25.035mm. and the, limits of the shaft are 25.022 and 25.035. The shaft is, always bigger than the hole. This is an interference fit., Maximum interference, In an interference fit, it is the algebraic difference between, the minimum hole and the maximum shaft. (Fig 7), , Minimum clearance, In a clearance fit, the minimum clearance is the difference, between the minimum hole and the maximum shaft. (Fig.4), The maximum clearance is 20.000 - 19.993 = 0.007mm., (Fig. 4), The maximum clearance is 20.021 - 19.980 = 0.041mm., (Fig. 4), There is always a clearance between the hole and the, shaft. This is the clearance fit., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.150, , 139
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Minimum interference, In an interference fit, it is the algebraic difference between, the maximum hole and minimum shaft. (Figs 7 and 8)., , The fundamental deviation symbol ‘H’ is chosen for the, holes, when the hole basis system is followed. This is, because the lower deviation of the ‘H’ hole is zero. It is, known as the “basic hole”. (Fig 10), , In the example shown in figure 6., the maximum interference is, , = 25.035-25.000, = 0.035, , the minimum interference is, , = 25.022-25.021, , Shaft basis system, , = 0.001, , In a standard system of limits and fits, where the size of, the shaft is kept constant and the variations are given to, the hole for obtaining different classes of fits, then it is, known as shaft basis system. The fundamental deviation, symbol ‘h’ is chosen for the shaft when the shaft basis is, followed. This is because the upper deviation of the ‘h’, shaft is zero. It is known as the ‘basic shaft’. (Fig 11), , Transition fit, It is a fit which may sometimes provide clearance, and, sometimes interference. When this class of fit is, represented graphically, the tolerance zones of the hole, and shaft will overlap each other. (Fig 8), , The hole basis system is removed mostly. This is because,, depending upon the class of fit, it will be always easier to, alter the size of the shaft as it is external, but it is difficult, to do minor alterations to a hole. Moreover the hole can be, produced by using standard toolings., , Example, Fit 75 H8 / j7 (Fig 9), , The three classes of fits, both under the hole basis and, the shaft basis, are illustrated in Fig 12., , The limits of the hole are 75.000 and 75.046 mm and those, of the shaft are 75.018 and 74.988 mm., Maximum clearance, , = 75.046 - 74.988, = 0.058 mm., , If the hole is 75.000 and the shaft 75.018 mm, the shaft is, 0.018mm bigger than the hole. This results in interference., This is a transition fit because it can result in a clearance, fit or an interference fit., Hole basis system, If a standard system of limits and fits, where the size of, the hole is kept constant and the size of the shaft is varied, to get the different classes of fits, it is known as the hole, basis system., , 140, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.150
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The B. I. S system of limits and fits - reading the standard chart, Objective : At the end of this lesson you shall be able to, • refer to the standard limit system chart and determine the limits of sizes., The standard chart covers sizes up to 500 mm (I.S.919 of, 1963) for both holes and shafts. It specifies the upper and, lower deviations for a certain range of sizes for all, combinations of the 25 fundamental deviations, and 18, fundamental tolerances., , Example, 30H7 (Fig 1), , The upper deviation of the hole is denoted as ES and the, lower deviation of the hole is denoted as EI. The upper, deviation of the shaft is denoted as ‘es’ and the lower, deviation of shaft is denoted as ‘ei’., es is expanded as ECART SUPERIOR and ei as, ECART INFERIOR., , It is an internal measurement. So we must refer to the, chart for ‘holes’., , Determining the limits from the chart, , Look for es, and ei values in microns for H7 combination, for 30mm basic size., , Note whether it is an internal measurement or an external, measurement., , It is given as + 25, +0, , Note the basic size., , Therefore, the maximum limit of the hole is 30 + 0.025 =, 30.025 mm, , Note the combination of the fundamental deviation and, the grade of tolerance., The deviations which are given in microns, with the sign., Accordingly add or subtract from the basic size and, determine the limits of size of the compnents., , The minimum limit of the hole is 30 + 0.000 = 30.000 mm., Refer to the chart and note the values of 40 g6., The table for tolerance zones and limits as per, IS2709 is attached. (Table 1), , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.150, , 141
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142, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.150, , +150, , +240, , +215, +30, , +140, , +200, , B11, , +310, , +560, , +280, , mm, +530, , N, G, +510, E, +260, , R, +460, , +390, S, +200, I, Z, +440, E, +220, , N, +380, A, +190, L, , +170, O, +340, , +330, , +160, , +290, , +150, , +260, , Copyright @ NIMI Not to be Republished, , 14, , Over, , Over, +830, up to, +580, , Over, +770, up to, +520, , Over, +710, up to, +460, , Over, +630, +180, , Over, +600, up to, +380, , Over, +550, up to, +360, , Over, +470, up to, +310, Over, +480, +130, Over, +530, up to, +340, , 24, , Over, +300, up to, , +33, , +15, , +18, , +2, , +15, , +1, , +12, , +1, , +10, , +9, +12, , 0, , +6, , k6, , +8, , -6.5, , +6.5, , -5.5, , +5.5, , -4.5, , +4.5, , +4, +8, , -3, , +3, , js6, , 0, , -13, , 0, , -11, , 0, , -9, , 0, , 0, +1, , -6, , 0, , h6, , 0, , -21, , 0, , -18, , 0, , -15, , 0, , 0, -4, , -10, , 0, , h7, , 0, , -52, , 0, , -43, , 0, , -36, , 0, , 0, -8, , -25, , 0, , h9, , 0, , -130, , 0, , -110, , 0, , -90, , 0, , 0, -12, , -60, , 0, , h11, , -9, , -20, , -7, , -17, , -6, , -14, , -5, , -4, -30, , -8, , -2, , g6, , -25, , -41, , -20, , -34, , -16, , -28, , -13, , -10, -75, , -16, , -6, , f7, , -50, , -73, , -40, , -59, , -32, , -47, , -25, , -20, -12, , -28, , -14, , e8, , -80, , -117, , -65, , -93, , -50, , -76, , -40, , -30, -22, , -45, , -20, , d9, , +151, , +108, , 180, , +133, , 180, , +100, , 160, , 160, , +125, , +92, , 140, , 140, , +117, , 120, , +101, , +71, , 100, A up to, +240 +410, , +93, , 80, , +59, , 100, , +78, , 80, , +53, , I, +72, , +43, , 65, , 65, , 40, M, up to, +180 +320, 50, , +106, , +68, , +93, , +65, , +90, , +63, , +88, , +76, 120, , +51, , +73, , +43, , +62, , +41, , +60, , +34, 50, , +43, , +68, , +37, +79, , +59, , +32, , +51, , +26, , +27, , +52, , +23, +54, , +45, , +20, , +39, , +17, , +3, , +28, , +3, , +25, , +2, , +21, , +2, , -22, , 0, , -19, , 0, , -16, , -12.5, , -25, , +12.5 0, , -11, , +11, , -9.5, , +9.5, , -8, , -40, , 0, , -35, , 0, , -30, , 0, , -25, , -100, , 0, , -87, , 0, , -74, , 0, , -62, , -250, , 0, , -220, , 0, , -190, , 0, , -160, , -39, , -14, , -34, , -12, , -29, , -10, , -25, , -83, , -43, , -71, , -36, , -60, , -30, , -50, , -148, , -85, , -126, , -72, , -106, , -60, , -89, , -245, , -145, , -207, , -120, , -174, , -100, , -142, , b11, , -240, , -110, , -205, , -95, , -170, , -80, , -70, -28, , -240, , -480, , -230, , -460, , -210, , -450, , -200, , -180, , -390, , -170, , -340, , -150, , -330, , -140, , -130, , -340, , -560, , -310, , -530, , -280, , -510, , -260, , -240, , -440, , -220, , -390, , -200, , -380, , -190, , -180, , -330, , -170, , -290, , -160, , -260, , -150, , -240, , -150, , -140, -60, , -140, +330, -120 -200, , - 60, , c11, , -120, , +42, , +22, , +28, , +12, , +23, , +10, , +19, , +16, +15, , +4, , +10, , n6, , -280, , +50, , +28, , +35, , +18, , +29, , +15, , +24, , +20, +19, , +6, , +12, , p6, , 40, , +59, , +35, , +41, , +23, , +34, , +19, , +28, , +23, 6, , +10, , +16, , r6, , 30, , 30, , 18, 24, , N, , +39, , +28, , 10, 14, , +48, , +23, , 18, , +32, , 6, , 10, , +14, , +27, , 3, , +20, , s6, , 3, up to, +270, , 1, , Over, up to, +430, , Over, +370, up to, +280, Over, up to, +400, Over, +290, up to, , up to, + 270, Over, +345, +70, +140, , A11, From, , -660, , -830, , -580, , -770, , -520, , -710, , -460, , -410, -400, , -600, , -380, , -550, , -360, , -530, , -340, , -320, -290, , -470, , -310, , -430, , -300, , -400, , -290, , -370, , -280, , -270, -145, , -330, , -270, , a11, , -105, , -133, , -93, , -125, , -85, , -117, , -77, , -66, -460, , -93, , -58, , -78, , -48, , -72, , -42, , -59, -340, , -34, , -48, , -27, , -39, , -21, , -32, , -17, , -15, -215, , -24, , -14, , S7, , -60, , -93, , -53, , -90, , -50, , -88, , -48, , -41, -630, , -73, , -38, , -62, , -32, , -60, , -30, , -50, -480, , -25, , -41, , -20, , -34, , -16, , -28, , -13, , -11, -345, , -20, , -10, , R7, , -68, , -28, , -59, -101, , -24, , -51, , -21, , -42, , -17, , -35, , -14, , -29, , -11, , -24, , -9, , -8, -27, , -16, , -6, , P7, , TABLE FOR TOLERANCE ZONES & LIMITS (DIMENSIONS IN μ m), , -52, , -12, , -45, -76, , -10, , -39, , -9, , -33, , -8, , -28, , -7, , -23, , -5, , -19, , -4, , -4, -23, , -14, , -4, , N7, , -28, , +12, , -25, , +10, , -21, , +9, , -18, , +7, , -15, , +6, , -12, , +6, , -10, , +5, , +3, -20, , -10, , 0, , K7, , -20, , +20, , -17.5, , +17.5, , -15, , +15, , -12.5, , +12.5, , -10.5, , +10.5, , -9, , +9, , -7.5, , +7.5, , +6, -16, , -5, , +5, , JS7, , 0, , +40, , 0, , +35, , 0, , +30, , 0, , +25, , 0, , +21, , 0, , +18, , 0, , +15, , +12, -9, , 0, , +10, , H7, , 0, , +63, , 0, , +54, , 0, , +46, , 0, , +39, , 0, , +33, , 0, , +27, , 0, , +22, , +18, -6, , 0, , +14, , H8, , 0, , +100, , 0, , +87, , 0, , +74, , 0, , +62, , 0, , +52, , 0, , +43, , 0, , +36, , +30, 0, , 0, , +25, , H9, , 0, , +250, , 0, , +220, , 0, , +190, , 0, , +160, , 0, , +130, , 0, , +110, , 0, , +90, , +75, 0, , 0, , +60, , H11, , +14, , +54, , +12, , +47, , +10, , +40, , +9, , +34, , +7, , +28, , +7, , +24, , +5, , +20, , +16, 0, , +2, , +12, , G7, , +43, , +106, , +36, , +90, , +30, , +76, , +25, , +64, , +20, , +53, , +16, , +43, , +13, , +35, , +28, 0, , +6, , +20, , F8, , +65, , +149, , +50, , +120, , +40, , +98, , +78, +10, , +20, , +60, , D10, , +80, , +85, , +185, , +72, , +159, , +60, , +145, , +305, , +120, , +260, , +100, , +134 +220, , +50, , +112 +180, , +40, , +92, , +32, , +75, , +25, , +61, , +50, +4, , +14, , +39, , E9, , +530, , +230, , +480, , +210, , +460, , +200, , +450, , +400, , +170, , +390, , +150, , +340, , +140, , +330, , +290, , +120, , +280, , +110, , +240, , +95, , +205, , +80, , +170, , +145, +20, , +60, , +120, , C11
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Mass production and interchangeable manufacture, Objectives: At the end of this lesson you shall be able to, • state the advantages and disadvantages of mass production, • outline the meaning of the term, interchangeability, • state the necessity for the limit system., Mass production, Mass production means production of a unit, component, or part in large numbers., , Maintenance is simpler because spares are easily, available. (Fig 2), , Advantages of mass production, Time for the manufacture of components is reduced, The cost of a piece is reduced, Spare parts can be made available quickly, Gauges are used to check the components, Even unskilled workers can be employed for checking, Measuring time is saved, Disadvantages of mass production, Special purpose machines are necessary, Jigs and fixtures are needed, Gauges are to be used, hence the initial expenditure will, be high, Selective assembly, Figures 1&2 illustrate the difference between a selective, assembly and a non-selective assembly. It will be seen in, Fig 1 that each nut fits only one bolt. Such an assembly, is slow and costly, and maintenance is difficult because, spares must be individually manufactured. spares must, be individually manufactured., , Non-selective assembly provides interchangeability, between the components., In modern engineering production, i.e. mass production,, there is no room for selective assembly. However, insome, special circumstances, selective assembly is still justified., Interchangeability, When components are mass-produced, unless they are, interchangeable, the purpose of mass production is not, fulfilled. By interchangeability, we mean that identical, components, manufactured by different personnel under, different environments, can be assembled and replaced, without any rectification during the assembly stage and, without affecting the functioning of the component when, assembled., Necessity of the limit system, If components are to be interchangeable, they need to be, manufactured to the same identical size which is not, possible, when they are mass-produced. Hence, it, becomes necessary to permit the operator to deviate by a, small margin from the exact size which he is not able to, maintain for all the components. At the same time, the, deviated size should not affect the quality of the assembly., This sort of dimensioning is known as limit dimensioning., , Non-selective assembly, , A system of limits is to be followed as a standard for the, limit dimensioning of components., , Any nut fits any bolt of the same size and thread type., Such an assembly is rapid, and costs are reduced., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.150, , 143
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Quality control, Objectives : At the end of this lesson you shall be able to, • state the features of quality control, • state the meaning of quality control, • sate the different factors of quality control, • state the recent trends in quality control, • state the different levels of inspection., Quality control, , Product specification, , The quality of a product is generally defined as its, usefulness towards the purpose for which it is, manufactured. In other words 'Fitness for use'., , The details regarding the product in question are collected, from the probable consumers (users) by the staff of the, marketing and sales departments., , In olden days, the manufacture of a product was in batches, ie., in smaller quantities, not exceeding say 10 or 100., In this case, the components were made to fit each other, through an inspection process, where the good ones were, segregated from the bad., , These details should truly reflect the requirements and, aspirations of the users. Thus, the conformance of the, real use with the product specification is the first step of, quality control., , With the advent of mass production, this method of, inspection caused a lot of rejections and the, manufacturers started to use preventive inspection where, in measures were taken to reduce the rejection to almost, zero., , The product specifications are scrutinized by various, experts from the production and product service, departments. Based on the recommendations of these, experts the technical specifications are prepared to very, minute details., , Thus, one started hearing about the concept of `zero, defects'. The aim of the inspection is to prevent rejection., This new approach towards producing products fit for use,, without the rejection losses and re–work called for the, imposition of controls at different stages of the manufacture, of a component. These controls ensured the required, quality, and thus quality control became an important, activity in the industries., , The correspondence between the product specification and, the technical specification is the second quality step., , It is thoroughly understood today that quality starts from, the customer and ends with the customer. Thus, the, customer has become a very important person in the minds, of the manufacturers of consumables and other products., So the quality of a product has to be built into the product, at the following stages. (Fig 1), , Technical specification, , Manufacturing the product, including packing and, forwarding to the customer, For the manufacture of the product the right type of raw, material, machinery and manpower should be involved so, that the end product conforms to the technical, specifications. Moreover, the product thus produced should, reach the consumer without any damage., This forms the third quality step., Thus, quality control is the culmination of all these activities, required for defining, quantifying, effecting and measuring, the quality of the product. The main objective of quality, control is to achieve fitness for use at the lowest cost., This calls for an understanding of the following points., -, , There is always an optimum quality level., , -, , All personnel in an enterprise are responsible for the, quality of a product., , -, , The quality must be controlled and built in at the, various stages planned. This requires well organised, cooperation between all the departments in the, enterprise., , -, , There is one quality level that strikes the optimum, level between the utility and cost of product, as shown, in Fig 2., , The two parameters, utility and cost in the graph, conform, to the following basic laws., , 144, , Utility increases with increase in quality but the trend is, decreasing beyond the optimum quality level. This is the, law of the decreasing marginal utility., Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.150, , Copyright @ NIMI Not to be Republished
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This is done by monitoring the quality in the different, steps and at different stages, and feed back this, information to the concerned functions., This monitoring should be based on costs, and penetrate, down to processes and operations so that detailed, information on quality costs are obtained., Quality costs are mostly classified as follows., Quality costs, Inspection costs, Labour, equipment, and overhead for, , Rejection costs, Internal, , External, , Preventive Segregation, , Rejections, , Guarantee, , Inspection, , Re-work, , Service, , This is the law of increasing marginal cost., , Delay, , Distance, , When the design is finalised and production starts, the, cost of the product quality can be illustrated as in the, graph. (Fig.3) A well controlled and efficient production, requires less inspection effort and vice versa. It is the total, cost of the production and the inspection/rejection that, has to be kept at a minimum. It is hence important to, avoid sub-optimising ie., keeping one or the other, parameter at a minimum. It is hence important to avoid, this. From the graph it is also evident that too high or too, low a quality is uneconomical., , Consequengoodwill, tial costs, etc. loss, etc., , The cost does also increase with increasing quality. The, increase is progressive., , The optimum quality should be estimated from the total, cost., Total costs cannot be precisely computed, due to practical, limitations in estimating and accounting, but it is obvious, that the cost should include more than that of the quality, and inspection function. In fact, it should include all the, functions., If all the functions are influencing the optimum quality,, they are also responsible for the quality., The old concept of quality control was that the inspection, or quality department was responsible for the quality. This, concept still persists to a considerable extent., This concept is wrong and is emanating from the, secondary duty of inspection. Namely, to sort out faulty, component or products and ensure an economical quality, level after the inspection. This is however a postmortem, activity and the primary duty of the inspection is to help, other functions to prevent mistakes., , Quality costs are often quite substantial and surveys of, the European and American markets have found that, aspect., The quality costs are collected and presented to the, concerned parties. This is the ground for improvement, and control. (Fig.4), , It must be possible to apply control of quality in all phases, of market use, design and production and a good quality, cost reporting system will indicate where the costs are, higher., When the weak quality spots (where failure costs are high), are located, all the concerned parties must work together, and find solutions for correcting and controlling the problem, with the drastic developments in technology, the user ie., the consumer is better placed today to demand reliability, of the product (ie. failure-free performance of the product, over a period of time). So the manufacturer has to widen, the sphere of quality control activities to quality assurance, and reliability, due to the stiff competition amongst the, manufacturers.The concept 'Looks first and function, foremost', is one way to stress the need for improving the, looks of a product. The importance of appearance of the, product and its dependable function is today being stressed, and realized all over. Only then, can one compete in the, international market., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.150, , 145
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We may find in the near future that quality control has, given way to the new concept namely Quality Engineering, wherein, the emphasis would be on the usefulness of a, product, not only for the individuals but also for the, entire humanity., The occurance of non–florification trading on nuclear, weapons is an apt example of such an understanding, with regard to the quality of a product., Quality control, , 2 The AQL, 3 When to inspect?, After 10 minutes, you will be able to understand the, reliability of an inspector's findings and take more informed, decisions based on an inspection report., If you have not started doing professional quality control,, you will need to understand these 3 concepts to make, sure the inspection plan meets your needs., 1 Inspection levels, , What is quality control?, Quality control is a set of methods used by organizations, to achieve quality parameters or quality goals and, continually improve the organization 's ability to ensure, that a software product will meet quality goals., Quality control process (Fig.5), , Why use random sampling?, Shipments often represent thousands of products., Checking 100% of the quality would be long and expensive., A solution is to select samples at random and inspect, them, instead of checking the whole lot., But how many samples to select? On the one hand., Checking only a few pieces might prevent the inspector, from noticing quality issues; on the other hand, the, objective is to keep the inspection short by reducing the, number of samples to check., The relevant standards purpose a standard severity, called, "normal level", which is designed to balance these two, imperatives in the most efficient manner., , The three class parameters that control software quality, are:, , Within this normal severity, there are three general levels:, I, II, and III. Level II is used for more than 90% of, inspections. For example, for an order of 8.000 products,, only 200 samples are checked., , – Plan - It is the stage where the quality control processes, are planned., , Military Standard 105 was created by the US Department, of Defence to control their procurements more efficiently., In 1994 they decided to relay on non-governmental, organizations to maintain this type of standard. The ANSI,, ISO, and other institutes have created their own standard,, but in essence they are similar. The major third -party QC, firms use the same standards and the same statistical, tables., , – Do- Use a defined parameter to develop the quality., , When to adopt a different level, , – Check- Stage to verify of the quality of the parameters, are met., , Suppose you source a product from a factory that often, ships substandard quality. You know that the risk is higher, than average. How to increase the Discriminating power, of the inspection? You can opt for level III, and more, samples will be checked., , – Products, – Processes, – Resources, The total quality control process consists of :, , – Act- Take corrective action if needed and repeat the, work., Quality control characteristics, – Process adopted to deliver a quality product to the, clients at best cost., – Goal is to learn from other organizations so that quality, would be better each time., – To avoid making errors by proper planning and, execution with correct review process., Quality control basic concepts, In this article I explain three fundamental concepts that, every buyer should be familiar with when it comes to quality, inspections:, 1 Inspection levels, 146, , Similarly, if a supplier has consistently delivered acceptable, products in the past and keeps its organization unchanged,, you can choose level I. As fewer samples have to be, checked, the inspection might take less time and be, cheaper., The relevant standards give no indication about when to, switch inspection levels, so most importers rely on their, "gut feeling"., The "special levels", Inspectors frequently have to perform some special tests, on the products they are checking. In some cases the, tests can only be performed on very few samples, for two, reasons:, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.150
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1 They might take a long time (e.g. doing a full function, test as per claims on the retail box)., , -, , Defects can be on the product itself, on the labeling or, on the packaging., , 2 They end up in product destruction. (E.g. unstitching a, jacket to check the lining fabric)., , -, , If one sample presents several defects, only the most, severe one is counted., , For these situations only, the inspector can choose a, "special level"., , How to read the AQL tables, , So we have three "general" inspection levels, and four, "special levels". For a given order quantity, each level gives, a different number of samples to check. Let's see how it, plays in two examples., 2 The AQL (acceptance quality limit), In part 1, we explained the different inspection levels that, can be used. Another basic concept rings familiar to many, importers, but is often not clearly understood: the AQL, (Acceptance Quality Limit)., There is no such thing as zero defect, First, as a buyer, you have to know what proportion of, defects is tolerated on your market. If you are in the aviation, business, any defective part might cause a disaster, so, your tolerance will be very, very low. But you will have to, accept a higher percentage of defects if you source, consumer products that are assembled by hand in china, or in India., An objective limit is necessary, So, how many defects are too many? It is up to you, as a, buyer, to make this decision. There are two reasons why, you should not leave this to the inspector's judgment:, 1 When it comes to giving instruction to an inspector,, you should never leave gray areas-as they might open, the door to corruption., , The master tables included in the relevant standards are, commonly called AQL tables. Let's take an example., You buy 8.000 widgets from a factory, and you choose, inspection level II. In the table below (which is only valid, for single sampling plans), you see that the corresponding, letter is L., Now let's turn to the next table (which is only appropriate, for normal-severity inspections). The letter L gives you the, number of samples to draw at random: 200 pcs., And what about the AQL? Let's say you follow the usual, practice of tolerating 0% of critical defects, 2.5% of major, defects, and 4.0% of minor defects. The maximum, acceptable number of defects is 10 major and 14 minor., In other words, the inspection is failed if you find at least 1, critical defect and /or at least 11 major defects and /or at, least 15 minor defects., 3 When to inspect?, The first two parts focused on the different inspection levels, and on the AQL tables. So you Know how to set the number, of samples to check and how many defects have to be, accepted. With these setting and your detailed product, specifications, a QC inspector can check your products, and reach a conclusion (passed or failed)., , The AQL is the proportion of defects allowed by the buyer., It should be communicated to the supplier in advance., , But importers face one more question when should the, products be inspected? This is an extremely important, issue for buyers willing to secure their supply chain., Spending a few hundreds of dollars to check and fix issues, early can be an excellent investment; if might save you, weeks of delay, shipments by air, and /or lower quality, products that you have to accept and deliver to your own, customers., , The three categories of defects, , Four types of inspections, , Some defects are much worse than others. Three, categories are typically distinguished:, , Let's picture the simplified model where one factory turns, raw materials into finished products. (If you also have to, manage the quality of sub = suppliers' products, the same, model can be applied to them), , 2 Your supplier should have clear criteria for acceptability,, or they will see rejections as unfair., , -, , Critical defects might harm a user or cause a whole, shipment to be blocked by the customs., , -, , Major defects are not accepted by most consumers,, who decide not to buy the product., , -, , Minor defects also represent a departure from, specifications, but some consumers would still buy, the product., , For most consumer products, critical defects are not, allowed, and the AQL for major defects and minor defects, are 2.5% and 4.0% respectively., , Pre-production inspection, This type of inspection is necessary if you want to check, the raw materials or components that will be used in, production. Buying cheaper materials can increase a, factory's margin considerably, so you should keep an eye, on this risk. It can also be used to monitor the processes, followed by the operators., During production inspection, , This inspection allows you to get a good idea of average, product quality, and to ask for corrections if problems are, A professional inspector will notice defects and evaluate, found. It can take place as soon as the first finished, their category by himself. But it is better if the buyer, products get off the line, but these samples might not be, himself describes the most frequent defects and, representative of the whole. So usually an inspection during, assigns categories to each one., production is done after 10-30% of the products are finished., Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.150, 147, , Some important remarks, -, , Copyright @ NIMI Not to be Republished
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Final (pre-shipment) inspection, Inspecting the goods after they are made and packed is, the standard QC solution of most importers. The inspector, can really check every detail, including counting the total, quantity and confirming the packaging. Final inspections, are usually performed in a hurry, just before shipment. To, avoid creating delays, inspectors can usually start after, all products are finished and 80% + of the shipment quantity, is packed., Loading supervision, , INSPECTION, RECORD, DATE, , BY, , ACCEPTED, , REJECTED, , In some cases, a buyer wants to make sure the factory, ships the right products, in the right quantity, and with the, right loading plan., Records maintained in shop floor by a worker, Job card: Each and every job is accompanied by job, card in a industry. The job card is very important document, to be maintained by an operator. It include the following, details., 1 Document No, 2 Date, 3 Customer Name, 4 Work order No, 5 Operator Name, 6 Time Record, 7 Operation Name / Number, 8 Quantity etc, , ACCEPTED, , _______________________, , Customer, , Inspection record, , W.O No, , __________________________, , The record is used for inspecting the workpiece by the, operator or quality inspector., , No PCB, , __________________________, , 1 Date of Inspection, , Part No., , __________________________, , Inspector, , __________________________, , Commented, , _______________________, , 2 Name of the component, 3 Inspected by (Operator/ Inspector), 4 Quantity accepted/Rejected, 5 Rework details if any, Accepted / Rejected / Rework tag : After inspecting the, work piece, accepted tag is enclosed with sign and date if, the work pieced are accepted and rejected tag is enclosed, is the pieces are rejected. If there is any rework, rework, tag is enclosed. The rework tag has the details of rework, to be done., , INSPECTED, READY, TO USE, SIGNED BY ___________________, DATE, , 148, , ______________, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.150
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Surface quality, Objectives: At the end of this lesson you shall be able to, • state the meaning of roughness value, • state the parameters on which surface quality depends, • state the method of measuring roughness, • define the symbols for surface roughness., When components are produced either by machining or by, hand processes, the movement of the cutting tool leaves, certain lines or patterns on the work surface. This is known, as surface texture. These are, in fact, irregularities, caused, by the production process with regular or irregular spacing, which tend to form a pattern on the workpiece., (Fig 1), , Examples, The components of surface texture, Roughness (Primary texture), The irregularities in the surface texture result from the, inherent action of the production process. These will, include traverse feed marks and irregularities within them., (Fig 2a), , In the case of slip gauges (Fig 3) the surface texture has, to be extremely fine with practically no waviness. This will, help the slip gauges to adhere to each other firmly when, wrung together., , Waviness (Figs 2b & 2c), This is the component of the surface texture upon which, roughness is superimposed. Waviness may result from, machine or work deflections, vibrations, chatter, heat, treatment or warping strain., The requirement of surface quality depends on the actual, use to which the component is put., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.150, , 149
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The cylinder bore of an engine (Fig 4) may require a certain, degree of roughness for assisting the lubrication needed for, the movement of the piston., , ‘Ra’ Values, The most commonly used method of expressing the, surface texture quality numerically is by using Ra value., This is also known as centre line average (CLA)., The graphical representation of Ra value is shown in, Figures 6 & 7. In Figure 6 a mean line is placed cutting, through the surface profile making the cavities below and, the material above equal., , For sliding surfaces the quality of surface texture is very, important., When two sliding surfaces are placed one over the other,, initially the contact will be only on the high spots. (Fig 5), These high spots will wear away gradually. This wearing, away depends on the quality of the surface texture., , The profile curve is then drawn along the average line so that, the profile below this is brought above., A new mean line (Fig 7) is then calculated for the curve, obtained after folding the bottom half of the original profile., , The distance between the two lines is the ‘Ra’ value of the, surface., , Due to this reason it is important to indicate the surface, quality of components to be manufactured., The surface texture quality can be expressed and assessed, numerically., , 150, , The ‘Ra’ value is expressed in terms of micrometre, (0.000001) or (m); this also can be indicated in the, corresponding roughness grade number, ranging from N1 to, N12., When only one ‘Ra’ value is specified, it represents the, maximum permissible value of surface roughness., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.150
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Lay: Symbols for designating the direction of lay are shown and interpreted in table 1., TABLE 1, Example showing, __, __, , Interpretation, Lay approximately parallel to the, line representing the surface to, which, the symbol is applied., , ⊥, , Lay approximately perpendicular, to the line representing the surface, to which the symbol is applied, , X, , Lay angular in both direction to line, representing the surface to which, the symbol is applied., , M, , Lay multidirectional., , C, , Lay approximately circular relative to the, centre of the surface to which the symbol, is applied., , R, , Lay approximately radial relative to the, centre of the surface of which the symbol, is applied., , P, , Direction of tool marks, , Lay particulate, non-directional, or, protuberant., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.150, , 151
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Surface texture measuring instruments, Objectives: At the end of this lesson you shall be able to, • distinguish the features of mechanical and electronic surface indicators, • name the parts of a mechanical surface indicator, • brief the features of electronic surface indicators (taly-surf)., The use of surface finish standards which we have seen, earlier is only a method of comparing and determining the, quality of surface. The result of such measurement very, much depends on the sense of touch and cannot be used, when a higher degree of accuracy is needed., The instruments used for measuring the surface texture, can be of a mechanical type or with electronic sensing, device., Mechanical surface indicator, This instrument consists of the following features. (Fig 1), , There are different types of electronic surface measuring, devices; one type of such an instrument used in workshops, is the taly-surf., Taly-surf (Electronic surface indicator): This is an, electronic instrument for measuring surface texture. This, instrument can be used for factory and laboratory use., (Fig 3), , 1 Measuring stylus, 2 Skids, 3 Indicator scale, 4 Adjustment screw, The stylus is made of diamond, and its contact point will, have a light radius., When the stylus is slowly traversed across the test surface, the stylus moves upward or downward depending on the, profile of the surface. (Fig 2) This movement is amplified, and transferred to the dial of the surface indicator.The, pointer movement indicates the surface irregularities., , The measuring head of this unit consists of a stylus (a), and a motor race (b) which controls the movement of the, instrument head across the surface. The movement of the, stylus is converted to electrical signals. These signals, are amplified in the surface analyser/amplifier (c) which, calculates the surface parameter and presents the result, on a digital or in the form of a diagram through a recorder, (d)., , When using a mechanical surface indicator, measurement, must be read as it is moved over the surface, and then a, profile curve is drawn manually to compute the mean value., , 152, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.150
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Machining symbols, Objectives: At the end of this lesson you shall be able to, • state the values of surface roughness, • state the indication of surface roughness., Letter symbols for tolerances, Indication of surface roughness values., S. No. Roughness value, Ra in microns, , Roughness grade, Number, , Roughness, Symbol, , Manufacturing process, , 1., , 50, , N12, , Flame cutting, hacksaw cut, bandsaw, cut, shot blast etc., , 2., , 25.0, , N11, , Sand casting, planning, shaping, filling etc., , 3., , 6.3, 3.2, 1.6, , N9, N8, N7, , Milling, drilling, die casting, turning,, forging, boring etc., , 4., , 0.8, 0.4, 0.2, , N6, N5, N4, , Centreless grinding, cylindrical grinding,, cold rolling, internal grinding, extrusion,, surface grinding, broaching, hobbing, EDM, reaming etc., , 5., , 0.1, 0.05, 0.025, , N3, N2, N1, , Super finishing, lapping honning etc., , Surface symbol indication, 1 The basic symbol consists of two legs of unequal length, inclined at approximately 60°., , 3 If the material removal is not permitted, a circle is added, to the basic symbol., , 2 If the material removal by machining is required, a bar, is added to the basic symbol., , 4 If some special characteristics have to be indicated, a, line is added to the larger leg., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.150, , 153
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5 Indication of surface roughness, a. Surface roughness obtained by any production, method., , c. Indicating the sampling length., , b. Surface roughness obtained by removal of material, by matching., , d. Direction of lay, surface pattern by the production, method employed., , b. Surface roughness obtained by removal of material, by matching., , e. Indication of allowance in mm., , 6 Indication of special surface roughness characteristics, a. Indicating the production method., , Surface texture, , b. Indicating the surface treatment or coating. Unless, otherwise stated, the numerical value of the, roughness, applies to the surface roughness after, treatment of coating., , 154, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.150
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Lapping, Objectives: At the end of this lesson you shall be able to, • state the purpose of lapping, • state the features of a flat lapping plate, • state the use of charging a flat lapping plate, • state the method of charging a cast iron plate, • explain between wet lapping and dry lapping., Lapping is a precision finishing operation carried out using, fine abrasive materials., Purpose: This process, – improves geometrical accuracy, – refines surface finish, – assists in achieving a high degree of dimensional, accuracy, – improve the quality of fit between the mating, components., Lapping process: In the lapping process small amount of, material are removed by rubbing the work against a lap, charged with a lapping compound. (Fig 1), , The commonly used abrasives are:, – Silicon Carbide, – Aluminium Oxide, – Boron Carbide and, – Diamond, Silicon carbide: This is an extremely hard abrasive. Its, grit is sharp and brittle. While lapping, the sharp cutting, edges continuously break down exposing new cutting, edges. Due to this reason this is considered as very ideal, for lapping hardened steel and cast iron, particularly where, heavy stock removal is required., Aluminium oxide: Aluminium oxide is sharp and tougher, than silicon carbide. Aluminium oxide is used in un-fused, and fused forms. Un-fused alumina (aluminium oxide), removes stock effectively and is capable of obtaining high, quality finish., Fused alumina is used for lapping soft steels and nonferrous metals., , Lap materials and lapping compounds, The material used for making laps should be softer than the, workpiece being lapped. This helps to charge the abrasives, on the lap. If the lap is harder than the workpiece, the, workpiece will get charged with the abrasives and cut the, lap instead of the workpiece being lapped., , Boron carbide: This is an expensive abrasive material, which is next to diamond in hardness. It has excellent, cutting properties. Because of the high cost, it is used only, in specialised application like dies and gauges., Diamond: This being the hardest of all materials, it is used, for lapping tungsten carbide. Rotary diamond laps are also, prepared for accurately finishing very small holes which, cannot be ground., , – copper, , Lapping vehicles: In the preparation of lapping compounds, the abrasive particles are suspended in vehicles. This, helps to prevent concentration of abrasives on the lapping, surfaces and regulates the cutting action and lubricates, the surfaces., , – brass or lead, , The commonly used vehicles are, , The best material used for making lap is cast iron, but this, cannot be used for all applications., , – water soluble cutting oils, , When there is excessive lapping allowance, copper and, brass laps are preferred as they can be charged more, easily and cut more rapidly than cast iron., , – machine oils, , Laps are usually made of:, – close grained iron, , Lead is an inexpensive form of lap commonly used for, holes. Lead is cast to the required size on steel arbor., These laps can be expanded when they are worn out., Charging the lap is much quicker., Lapping abrasives: Abrasives of different types are used, for lapping., , – vegetable oil, – petroleum jelly or grease, – vehicles with oil or grease base used for lapping ferrous, metals., Metals like copper and its alloys and other non-ferrous, metals are lapped using soluble oil, bentomite etc., In addition to the vehicles used in making the lapping, compound, solvents like water, kerosene, etc. are also, used at the time of lapping., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.150, , 155
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Abrasive of varying grain sizes from 50 to 800, are used for lapping, depending on the surface, finish required on the component., , Then place the workpiece on the plate and move along and, across, covering the entire surface area of the plate. When, carrying out fine lapping, the surface should be kept moist, with the help of kerosene., , The lapping compound consists of fine abrasive particles, suspended in a ‘vehicle’ such as oil, paraffin, grease etc., , Wet and dry lapping : Lapping can be carried out either, wet or dry., , The lapping compound which is introduced between the, workpiece and the lap chips away the material from the, workpiece. Light pressure is applied when both are moved, against each other. The lapping can be carried out manually, or by machine., , In wet lapping there is surplus oil and abrasives on the, surface of the lap. As the workpiece, which is being lapped,, is moved on the lap, there is movement of the abrasive, particles also., , Hand lapping of flat surfaces: Flat surfaces are handlapped using lapping plate made out of close grained cast, iron. (Fig.2) The surface of the plate should be in a true, plane for accurate results in lapping., , In dry method the lap is first charged by rubbing the, abrasives on the surface of the lap. The surplus oil and, abrasives are then washed off. The abrasives embedded on, the surface of the lap will only be remaining. The embedded, abrasives act like a fine oilstone when metal pins to be, lapped are moved over the surface with light pressure., However, while lapping, the surface being lapped is kept, moistened with kerosene or petrol. Surfaces finished by, the dry method will have better finish and appearance., Some prefer to do rough lapping by wet method and finish, by dry lapping., Honing, , The lapping plate generally used in tool rooms will have, narrow grooves cut on its surface both lengthwise and, crosswise forming a series of squares., While lapping, the lapping compound collects in the, serrations and rolls in and out as the work is moved., Before commencing lapping of the component, the cast, iron plate should be CHARGED with abrasive particles., This is a process by which the abrasive particles are, embedded on to the surfaces of the laps which are, comparatively softer than the component being lapped., For charging the cast iron lap, apply a thin coating of the, abrasive compound over the surface of the lapping plate., , Honing is a finishing process, in which a tool called hone, carries out a combined rotary and reciprocating motion, while the work piece does not perform any working motion., Most honing is done on internal cylindrical surface, such as, automobile cylindrical walls. The honing stones are held, against the work piece with controlled light pressure. The, honing head is not guided externally but, instead, floats in, the hole, being guided by the work surface (Fig.3) It is, desired that, 1 Honing stones should not leave the work surface, 2 Stroke length must cover the entire work length., In honing rotary and oscillatory motions are combined to, produce a cross hatched lay pattern as illustrated in Fig.3., , Use a finished hard steel block and press the cutting, particles into the lap. While doing so, rubbing should be, kept to the minimum. When the entire surface of the, lapping plate is charged, the surface will have a uniform, gray appearance. If the surface is not fully charged, bright, spots will be visible here and there., Excessive application of the abrasive compound, will result in the rolling action of the abrasive, between the work and the plate developing, inaccuracies., The surface of the flat lap should be finished true by, scraping before charging. After charging the plate, wash off, all the loose abrasive using kerosene., 156, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.150
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Honing tool, Lay pattern produced by combination of rotary and oscillatory, motion. (Fig.4), , Super abrasive honing stick with monolayer configuration,, where a layer of CBN grits are attached to stick by a, galvanically deposited metal layer, is typically found in, single stroke honing application., With the advent of precision brazing technique, efforts can, be made to manufacture honing stick with single layer, configuration with a brazed metal bond. Like brazed, grinding wheel such single layer brazed honing stick are, expected to provide controlled grit density, larger grit, protrusion leading to higher material removal rate and, longer life compared to what can be obtained with a, galvanically bonded counterpart., The important parameters that affect material removal rate, (MRR) and surface roughness (R) are:, , The honing stones are given a complex motion so as to, prevent every single grit from repeating its path over the, work surface., , 1 Unit pressure, P, , The critical process parameters are, , 3 Honing time, T, , 2 Peripheral honing speed, Vc, , 1 Rotation speed, 2 Oscillation speed, 3 Length and position of the stroke, 4 Honing stick pressure, With conventional abrasive stick, several strokes are, necessary to obtain the desired finish on the work piece., However, with introduction of high performance diamond, and CBN grits it is now possible to perform the honing, operation in just one complete stroke. Advent of precisely, engineered microcrystalline CBN grit has enhanced the, capability further. Honing stick with microcrystalline CBN, grit can maintain sharp cutting condition with consistent, results over long duration., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.150, , 157
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Production & Manufacturing, Turner - Advanced Turning, , Related Theory for Exercise 4.6.151-152, , Importance of Technical term used in Industry, Objectives : At the end of this lesson you shall be able to, • state the meaning of different terms used in industry, • calculate the machine time in turning., Engineering terminology, Broach (v) to finish the inside of a hole to a shape other, than round, as in a keyway (n) The tool for the process,, which has serrated edges and is pushed or pulled through, the hole to produce the required shape., Bushing (n) a smooth walled bearing (AKA a plain, bearing). Also a tool guide in a jig or fixture., Cam (n) A mechanical device consisting of an eccentric, or multiply curved wheel mounted on a rotating shaft, used, to produce variable or reciprocating motion in another, engaged for contacted part (Cam follower). Also Camshaft, Casting (n) any object made by pouring molten metal into, a mold., Chamfer (n) a flat surface made by cutting off the edge or, corner of a object (bevel) (v) the process of creating a, chamfer., Clevis (n) A U-shaped piece with holes into which a link is, inserted and through which a pin or bolt is run. It is used, as a fastening device which allows rotational motion., Collar (n) A Cylindrical feature on a part fitted on a shaft, used to prevent sliding (axial) movement., Collet (n) a cone-shaped sleeve used for holding circular, or rod like pieces in a lathe or other machine., Core (v) to form the hollow part of a casting, using a solid, form placed in the mould (n) the solid form used in the, coring process, often made of wood, sand, or metal. Mould, with core is final cast manifold., Counter bore (n) a cylindrical flat-bottomed hole, which, enlarges the diameter of an existing pilot hole. (v) The, process used to create that feature., Countersink (n) a conical depression added to an existing, hole to accommodate and the conic head of a fastener, recessing it below the surface of a face. (v) The process, used to create that feature., , Fillet (n) A rounded surface filling the internal angle, between two intersection surfaces. Also Rounds, Fit (n) The class of contact between two machined, surfaces, based upon their respective specified size, tolerances (Clearances, transitional, interference), Fixture (n) A device used to hold a work piece while, manufacturing operations are performed upon that work, piece., Flange (See bushing example) (n) a projecting rim or, edge for fastening, stiffening or positioning., Gauge (n) A device used for determining the accuracy of, specified manufactured parts by direct comparison., Gear Hobbing (v) A special form of manufacturing that, cuts gear tooth geometrices. It is the major industrial, process for cutting involute form spur gears., Idler (n) A mechanism used to regulate the tension in belt, or chain. Or, a gear used between a driver and follower, gear to maintain the direction of rotation., Jig (n) A special device used to guide a cutting tool (drill, jig) or to hold material in the correct position for cutting or, fitting together (as in welding or brazing), Journal (n) The part of a shaft that rotates within a bearing, key (woodruff key shown) (n) A small block or wedge, inserted between a shaft and hub to prevent circumferential, movement., Keyseat (n) A slot or groove cut in a shaft to fit a key. A, key rests in a keyseat., Keyway (n) A slot cut into a hub to fit a key. A key slides, in a keyway., Knurl (v) To roughen a turned surface, as in a handle or a, knob., Pinion (n) A plain gear, often the smallest gear in a gearset,, often the driving gear, May be used in conjuction with a, gear rack (rack and pinion, see below), , Coupling (n) A device used to connect two shafts together, at their ends for the purpose of transmitting power. May, be used to account for minor misalignment or for mitigating, shock loads., , Planetary Gears (n) A gear set characterized by one or, more planet gear (s) rotating around a sun gear. Epicyclic, gearing systems include an outer ring gear (known as an, planetary system), , Die (n) one of a pair of hardened metal plates or impressing, or forming desired shape. Also, a tool for cutting external, threads., , Rack (w/pinion gear) (n)A toothed bar acting on (or acted, upon ) by a gear ( pinion), , Face (v) to machine a flat surface perpendicular to the, axis of rotation of a piece., 158, , Ratchet (n) A space mechanical device used to permit, motion in one direction only., , Copyright @ NIMI Not to be Republished
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shims (n) a thin strip of metal inserted between two, surfaces to adjust for fit. (v) The process of inserted shims, Spline (n) A cylindrical pattern of keyways. May be, external (L) or Internal (R), Tap (v) To cut internal machine threads in a hole, (n) the, tool used to create that feature., Undercut (n) A cut having inward sloping sides, (v) to cut, leaving an overhanging edge., Definitions of technical terms- CNC SYSTEM, Absolute co - ordinates: The distance (or dimensions of, the current position from the origin (or zero point) of a, coordinate system (or measuring system) measured, parallel to each axis of the system., Address: A name (or label, or number) identifying a storage, area in a control system or computer memory., Analog: The use of physical quantity (like voltage) whose, amplitude represents that of another quantity (like distance), APT: Automatically programmed tools., , Co -ordinate system: A series of intersecting planes, or, planes and cylinders ( usually three) which form a reference, system., CPU: Central processing unit. The controlling unit in a, digital computer., Cutter diameter compensation: Provision in the control, system to modify the cutter offset by entering a numerical, correction to the cutting tool diameter., Cutter offset: Position of reference point on the tool., Cutting speed: The velocity of the cutting edge of the tool, relative to the work piece., Cycle: A sequence of operations which frequently repeated., Depth of cut: The amount of metal ( in mm or inch) removed, perpendicularly to the direction of feed in one pass of the, cutter over the work piece., Digit: a character used in a numbering system., Downtime: Time during which equipment is out of action, because of faults., , ASCII: American standard code for information interchange., , Dwell: A pause of programmed duration, usually to ensure, that a cutting action has time to be completed., , Auxiliary function: Another name for miscellanceous, function., , End-of-block mode: An agreed code which indicates the, completion of a block of input information on punched tape., , Axis: When associated with machine tools, an axis is a, direction in which a machine tool table or head can move., , Feed: The movement of a cutting tool into a work piece., , Backlash: The maximum movement at one end of a, mechanical system (such as geartrain) which does not, cause the other end to move., Base number: A base number (or radix) is an implied, number used when expressing a value numerically in the, normal decimal system, the base is 10 and 87 is a short, way to representing 8x101+7x10o=87 in binary notation, 1011 represents 1x23+0x22+1x21+1x20 = 8+2+1 = 11 in, decimals, , Feed rate: The rate, in mm/min or in. /min, at which the, cutting tool is advanced into the work piece., Format: An agreed order in which the various types of, words will appear within a block,, Hardware: Equipment e.g., Machine tool, or Control, or, computer., Incremental co-ordinates: The distance of current, position from the preceding position, measured in terms, of axial movements in the co-ordinate system., , Binary coded decimal number (BCD): The, representation of a number by groups of four binary digits, for each decimal digit in a number., , Interpolation: The process of supplying the positions of, a set of more closely spaced points between more widely, spaced points such as change points., , Binary digits: The characters 0 or 1 used in the binary, system to express any value ( see Base number), , IPM: Inches per minute (in. /min)., , Bit: A binary digit or its representation., Block: A collection of words in some agreed form. Usually, on a control tape, and separated from succeeding blocks, by an End of -Block code., , IPR: Inches per revolution (in. /rev) of a cutter or work, piece., ISO: International Organization for Standardization., , BIS - British Standards institution., , Machine language or machine instruction: The, instructions and data for computers are based on patterns, of bits., , Buffer: A temporary storage area where information is held, until it is moved into an operating area., , Machine zero: The machine zero point is at the origin of, the coordinate measuring system of the machine., , CCW: Counter clock wise., , Manual data input (MDI): A means, on the control panel,, of inserting numerical information into the control system., , Characters: The set of letters, decimal digits, signs (such, as + - :% etc), Circular interpolation: A contour control system with, circular interpolation cuts an arc of a circle from one block, on a control tape., , Manuscript: Handwritten program., Miscellaneous function: A control tape term for codes, such as M03 used to control machine tool functions such, as 'rotate spindle clockwise'., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.151 & 152, , 159
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NC: Numerical control., Preparatory function word: A word near the beginning, of a control tape block which calls for a change in mode., Preset tools: The setting of tools in special holders away, from the machine tool., Program: A systematic arrangement of instructions or, information to suit a piece of equipment., RPM: Revolutions per minute (rev/min), a measure of, spindle speed., Sequence number: The number allocated to a block or, group of blocks to identify them. Commonly takes a form, like N 278., , Servomechanism: A closed-loop positioning-control, system., Software: Programs, sequences of instructions, etc. Not, equipment (see Hardware)., Spindle speed: the rotational speed in RPM of the spindle, or shaft which supplies the cutting power., Subroutine: A sequence of computer-programming, statements or instructions which perform an operation, frequently required., Word: An agreed arrangement of characters and digits, (usually less than 10) which conveys one instruction, piece, of information, or idea., , Documentations - 1, Objectives: At the end of this lesson you shall be able to, • describe work organisation, • name the aspects of organisation of work, • state the common technical terms used in industry., Work organisation, , -, , Work teams, , Work organisation is to arrange and distribute the work, between the work teams in such a way that the best use, is made of the available labour, materials, tools and, equipment., , -, , Total productive maintenance, , -, , Total quality management, , -, , Outsourcing/ contracting out, , -, , to order the operations and activities of the work should, follow each other., , -, , to decide the various work teams., , -, , to decide the various work teams., , -, , to instruct and communicate correctly in order to avoid, misunderstandings., , Organisation of work, The organisation of work includes many aspects, such as, -, , Pace of work (speed of an assembly line, quotas)., , -, , Work load., , -, , Number of people performing a job (staffing levels)., , -, , Hours and days on the job., , -, , Length and number of rest breaks and days away from, work., , -, , Layout of the work., , -, , Skill mix of those workers on the job., , -, , Assignment of tasks and responsibilities and, , -, , Training for the tasks being performed., , Some common terms technically used in industry are as, follows:, -, , Lean production, , -, , Continuous improvement, , -, , Just-in-time production, , 160, , Lean production, An overall approach to work organisation that focuses on, elimination of any "waste" in the production / service, delivery process. It often includes the following elements:, "continuous improvement", "just-in-time production" and, work teams., Continuous improvement, A process for continually increasing productivity and, efficiency, often relying on information provided by employee, involvement groups or teams. Generally involves, standardizing the work process and eliminating microbreaks or any "wasted" time spent not producing/ serving., Just-in-time production, Limiting or eliminating inventories, including work-in-progress, inventories, using single piece production techniques often, linked with efforts to eliminate "waste" in the production, process, including any activity that does not add value to, the product., Work teams, Work teams operate within a production or service delivery, process, taking responsibility for completing whole, segments of work product. Another type of team meets, separately from the production process to "harvest" the, knowledge of the workforce and generate develop and, implement ideas on how to improve quality, production and, efficiency., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.151 & 152
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Total productive maintenance, , Outsourcing/ Contracting out, , Designed to eliminate all nonstandard, non-planned, maintenance with the goal of eliminating unscheduled, disruptions, simplifying (de-skilling) maintenance, procedures and reducing the need for "just-in-case", maintenance employees., , Transfer of work formerly done by employees to outside, organisations. In many workplaces undergoing restructuring,, worker knowledge about the productive/ service process is, gathered through "employee involvement" and then used, by management to "lean out" and standardize the work, process, thereby reducing reliance on worker skill and, creativity. This restructuring has resulted in job loss for, some underperformed, while increasing the work load and, work pace for those who remain on the job. The result of, these changes in work organisation is that it is no longer, just machines that are wearing out-it is the workers, themselves., , Total quality management, This is aimed towards zero defect or elimination of poor, quality in production. The quality concept of assuming the, best quality from inception to implementation throughout, the production process., , Different types of documentation as per industrial needs, Objectives : At the end of this lesson you shall be able to, • state the purpose of documentation, • list the different types of documentation, • explain the documents format - batch processing, BOM, cycle time, productivity report, manufacturing, inspection report., Documentation, , Process chart, , Documentation and records are used throughout the, manufacturing process as well as supporting processes, (quality control) must meet the basic requirements., Documentation is a set of documents provided on paper,, or online, or on digital or analog media, such as audio, tape or CDs. Examples are user guides, white papers,, online help, quick reference guides., -, , prepare, review, update and approve documents., , -, , identify changes and current revision status of, documents., , -, , use of applicable documents available at points of use, with the control documents of external origin, , A process chart is a graphical representation of the activities, performed during manufacturing or servicing jobs. Graphical, representation of the sequence of operations (workflow), constituting a process, from raw materials to finished, product., Process charts are used for examining the process in detail, to identify areas of possible improvements., The different types of process charts they are, - Operation process chart, - Flow process chart (man/ material/ equipment type), - Operator chart (also called two handed process chart), - Multiple activity chart, - Simo chart, , -, , identify and distribute relevant versions to be identifiable, and remain legible., , Batch record forms, , -, , prevent unintended use of obsolete documents and, archiving., , The stages of recording the documents is to, , The different types of documentation as per industrial, needs includes, -, , Processing charts, , -, , Bill of materials (BOM), , -, , Production cycle time format, , -, , Productivity reports, , -, , Manufacturing stage inspection report, , -, , Job cards format, , -, , Work activity log, , -, , Batch production record format, , -, , Estimation of work, , -, , Maintenace log format, , The documents used and prepared by the manufacturing, department provide step-by-step instructions for production-related tasks and activities, besides including areas, on the batch record itself for documenting such tasks., Batch production record is prepared for each batch should, include information on the production and control of each, batch. The batch production record should confirm that it, is the correct with standard operating procedure., These records should be numbered with a unique batch or, identification number and dated and signed when issued., The batch number should be immediately recorded in data, processing system. The record should include date of, allocation, product identity and size of batch., Documentation of completion of each significant step in, the batch production records (batch produciton and control records) should include :, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.151 & 152, , 161
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-, , Dates and when apporiate time., , -, , Major ewuipment used machinery and specified batch, numbers of raw materiala, reprocessed materials used, during manufacturing., , -, , Critical process parameters records., , -, , Trial products or sample (if reqiured)., , -, , Signatures of staff for sequence of operation., , -, , Laboratory test result and line inspection notes., , -, , Achieved production aganist target., , -, , Packaging and label (if any) details., , The batch processing record is signed with date, mentioning name of person responsible and their, designation. The remarks if any on the process should be, also mentioned then and there., Bill of materials (BOM) format - 2, The list of parts involved in manufacturing of an assembly, arranged in order is given in this format., The format shown is as per bureau of Indian Standards, IS:11666-1985 as example for Engineering Component, drawings., , Batch processing record: (Sample format - 1), , The BOM in the form of tabular columns has the, component marked with item number, and its name is, , The format 1 used in documentation of batch processing, record has the description of the job, necessarily, mentioned with part number and name of the part., , given under description and number of is mentioned under, quantity, with reference drawing ie., sub assembly/part, drawing number., , A predetermined batch quantity with batch number alloted, and identified with batch record number is documentation., The product reference is made with purchase order number., The production process is descriptively written about the, sequence of operation to be carried out on the product., The manufacturer organization name, period of manufacture, preferably the year with starting date of manufacture and, end date of manufacturer and number of pages of document, according to batch quantity processed, and total number, of pages of document, inclusive of inserted pages and, manufacturing facilities is provided with., , 162, , The material designation as per code of practice or, standards is mentioned, and any other specific notes are, given under remarks column., The BOM is placed on the manufacturing drawing, containing with assembly and parts in standard sheet sizes, of engineering drawing., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.151 & 152
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BATCH PROCESSING RECORD - FORMAT - 1, Batch Processing Record, Description of job, , Batch no. :, , Part no. :, , Batch quantity :, , Name of part :, , Batch record no. :, Purchase order no. :, , Description of process :, , Manufacturing Organisation :, Period of manufacture (Year - Qtr):, Number of pages according to batch:, , Start date of manufacture:, , End date of manufacture:, , Inserted pages:, , Manufacturing facilities:, , Total number of pages, 1. Operator / Technician, 2. Production in-charge:, 3. Section manager, 4. Plant in-charge:, 5. Production in-charge:, , Date, , Name and signature, , Date, , Name and signature, , Date, , Name and signature, , Date, , Name and signature, , Date, , Name and signature, , Remarks (if any), , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.151 & 152, , 163
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BILL OF MATERIAL (BOM) - FORMAT - 2, as per IS: 11666-1985, S.No, , Item No., , Description, , Quantity, , Reference, dwg no., , Material as, per standard, , Remark, , Cycle time, , Overall cycle time, , Cycle time is the total time from the beginning to the end, of the process. Cycle time includes process time, during, which a raw material worked with to bring it closer to, required form output, and delay time, during which the, workpiece waiting for next operation., , The complete time it takes to produce a single unit. This, term is generally used when speaking of a single machine, or process., , The time taken to perform one operation repeatedly, measured from “Start to Start” the starting point of one, product’s processing in a specified machine or, operationuntil the start of another similar product’s, processing in the same machine or process. Cycle time, is commonly categorized into same machine/process., Machine cycle time, The processing time of the machine working on a part., Auto cycle time, The time a machine runs un-aided (automatically) without, manual intervention., , 164, , Total cycle time, This includes all machines, processes, and classes of, cycle time through which a product must pass to become, a finished product. This is not lead time, but it does help, in determining it., Production cycle time (Format - 3), This format 3 should contain mentioning the organization, name department / section name. The process which is, being observed for analysing the cycle time is mentioned, with line in charge name and the date/time of the, operations, with operator name is indicated., The time observation on each operation, sequence noted, in the column, and lowest repeatable is also mentioned, for each operation. The times observation for machine, cycle time is also noted, with any notes be recorded in, respective operations in sequence., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.151 & 152
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PRODUCTION CYCLE TIME - FORMAT 3, Organisation Name:, , Process:, , Line Incharge:, , Date/Time:, , Department / Section :, , Operator :, , Machine, Cycle Time, , Operator, Sequence, , Observed Times, , Notes, , Lowest Repeatable, , Productivity report, , Daily production report (Format 4), , Productivity report to measure and review the efficiency of, a person, machine, factory, system, etc., in converting, inputs into useful outputs. Productivity report is computed, by dividing average output per period by the total costs, incurred or resources (capital, energy, material,, personnel) consumed in that period., , The output of production is shown in the format, referring, the job order no quantity, material and size, every process, involved, to produce a component, quality control,, packing should contain the details of planned quantity and, produced quantity is recorded in the document. This is, the base details for arriving the productivity report.The, incurred cost is worked out considering infrastructure, raw, materials and facilities., , The base document daily production report which reveals, the actual output against the target plan and on investment, cost incurred as mentioned above decides the cost, efficiency., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.151 & 152, , 165
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166, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.151 & 152, , Copyright @ NIMI Not to be Republished, , Job Order No., Quantity, Material & Size, , Job Order No., Quantity, Material & Size, , Job Order No., Quantity, Material & Size, , Job Order No., Quantity, Material & Size, , Job Order No., Quantity, Material & Size, , Date:, , Process-II, , Process-III, , Process-IV, , Quality Control, , Organisation Name:, , Packing, , Signature of section Incharge, , Planned Completed Planned Completed Planned Completed Planned Completed Planned Completed Planned Completed, , Process - I, , Section:, , Department:, , Daily Production Report, , DAILY PRODUCTION REPORT - FORMAT- 4
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Manufacturing stage inspection report (Format 5), , Inspection conducted by, Inspection Record No., , Status: From Date ..../..../...... To Date .../.../......, , Rejected, Accepted, Qty, Process, J.O Date, Job Order, No., Customer, Product ID/, Code, Date, , Organisation Name :, , P.O No. &, Date, , MANUFACTURING STAGE INSPECTION REPORT - FORMAT - 5, , The format 5 is to monitor the production in various stages, for which manufacturing stage inspection conducted for, documentation to review the productivity. The format gives, the details of product being inspected showing the details, of customer reference by purchase order (PO) number, , and date, job order number and date, process involved in, manufacture of product, the quality submitted for, inspection. The accepted and rejected quality recorded, with inspection record review date and the inspection, person signature who conducted the stage inspection is, recorded date wise for mentioned /specified period with, start and end dates., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.151 & 152, , 167
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Documentations - 2, Objectives : At the end of this lesson you shall be able to, • state the purpose of job card and its format details, • explain work activity log format details, • state the details of batch production format., Job card, A job card is a document showing the details of a job to be, performed in a production shop. It is used to authorize, and instruct the work team to take up the production work., Job card format - 1, Job card has the details of commencing the job, customer, name, work order no, document number, reference number, and date., , The details which have to be recorded about the product, line description showing the operations each into recording, of start time and total time of operation. The location time, recorded is to track if any delay/ reasons and necessary, actions if taken with remarks., If the product has to be completed with any of the further, operations in sequence, this card will travel along with job, for next workstations for further operations if any to complete, the requirement of job, and recorded till finishing of the, job., , JOB CARD - FORMAT-1, Doc No., Job Card, , Rev No., Date, , Order Starting Date, Customer, Work Order No., Details, S.No. Date, , 168, , Production Line, Description, , Time (Minutes), Start Time End Time Total Time, , Location, Time, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.151 & 152, , Remarks
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Work activity log format - 2, This document is to record the activity/operations performed, by the operator from time to time (format) shows time, duration as one hour (For whole day shift). The operator, , has to record every hour, activity description, equipment/, machinery/instrument used to perform the job., Any remarks may noted by the operator to complete this, record., , WORK ACTIVITY LOG - FORMAT-2, Organisation Name:, Department:, Section:, Employee Name:, Supervisor Name:, Date:, Start / Stop, , Operations, performed, , Equipment / Machinery/, Instruments used, , Remarks, , 8.00 to 9.00 a.m., 9.00 to 10.00 a.m., 10.00 to 11.00 a.m., 11.00 to 12.00 noon, 12.00 to 1.00 p.m., 1.00 to 2.00 p.m., 2.00 to 3.00 p.m., 3.00 to 4.00 p.m., 4.00 to 5.00 p.m., 5.00 to 6.00 p.m., , Batch production record format - 3, This document is for recording the details of production, covering the processing steps with documented page, number with deviation against each in short description., , This document is to be prepared under heading description, of job part number, batch number, name of the part. The, processing steps number serially for each process with, sequential operations in logical order with documented, page number. The description of deviation are noted against, each operations in sequence gives the detail of batch, production record for every part., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.151 & 152, , 169
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BATCH PRODUCTION RECORD - FORMAT-3, Batch Production Record in accordance with batch processing record, Manufacturing Organisation Name: _______________________, Description of job: ______________________, Name of part: __________________________, Batch No.: ____________________________, The following deviations have appeared (continued), No. process, step, 1, , 2, , Name of processing step, , Documented, page no., , Short description, of deviation, , Raw material preparation:, Operation 1: Descaling, , 1. _____________, , Operation 2: Degreasing, , 2. _____________, , Operation 3: Wire brushing, , 3. _____________, 4. _____________, , Sizing of material:, Operation 1: Shearing, , 1. _____________, , Operation 2: Deburring, , 2. _____________, 3. _____________, , Estimation and maintenance records, • state the purpose of estimation, • explain the details of formats for estimation sheet, • explain the details of formats for maintenance log, history sheet of machinery and equipment and checklist, for preventive maintenance., Estimation is the method of calculating the various, quantities and the expenditure to be incurred on a particular, job or process., In case the funds available are less than the estimated, cost the work is done in part or by reducing it or, specifications are altered,, The following essential details are required for preparing, an estimate., Drawings like plan, elevation and sections of important, parts., Detailed specifications about workmanship & properties, of materials, etc., , 170, , Standard schedule of rates of the current year., Estimating is the process of preparing an approximation, of quantities which is a value used as input data and it is, derived from the best information available., An estimate that turns out to be incorrect will be an, overestimate if the estimate exceeded the actual result,, and an underestimate if the estimate fell short of the actual, result., A cost estimate contains approximate cost of a product, process or operation. The cost estimate has a single total, value and it is inclusive of identifiable component, values., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.151 & 152
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Part No:3, , Part Name: Thumb Screw, , Material:Fe 3 10, , Assembly: Dial gauge holder, , Operation, No, , Operation, description, , Stock S 12:45x30, , Machine, , Estimated, time, , Rate / piece, per hr, , Instrument, , 01, , Job setting on, four jaw chuck, , Lathe, , 10 min, , 02, , Facing, , Lathe, , 5 min, , 03, , Centre drilling, , Lathe, , 15 min, , 04, , Turning 39.7, mm, , Lathe, , 5 min, , Vernier caliper, , 05, , Step turning, Ø22 mm, , Lathe, , 5 min, , Vernier caliper, , 06, , Form radius of, 4mm, , Lathe, , 10 min, , Radius caliper, , 07, , Space b/w,’div’, and ‘a’ hole, , Lathe, , 10 min, , 08, , Cut a internal, thread use, machine tap, , Lathe, , 20 min, , 09, , 1 x 450, Champer, , Lathe, , 5 min, , Lathe, , 7 min, , Lathe, , 10 min, , Lathe, Lathe, , 5 min, 10 min, , Lathe, , 20 min, , Lathe, , 15 min, , 10, , 11, , Reverse the hold, the job true it, Facing, , 12, , turn 39.7mm, and revolving, centre support, , 13, , clamp the, knurling tool, and knur the, surface, , 14, , 1 x 450 chamfer, of knur surface, , Steel rule, , thread a plug, gauge, , Vernier caliper, , Vernier caliper, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.151 & 152, , 171
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Maintenance log - Format 5, This format is made with details of maintenance activities performed machinewise,, MAINTENANCE LOG - FORMAT - 5, Organisation Name :, Department:, Section:, Name of the machine:, S.No, , Date, , Nature of fault, , Details of rectification done, , Signature of in-charge, , History sheet of machinery equipment - Format 6, The document recorded with historical data about the, machinery and equipment, contains all details about, supplier address, order no., date of receipt, installed and, placed, Date of commissioning and machine dimensions,, , 172, , weight, cost, particulars of drive motor, spare parts details,, belt specification, lubrication details, major repair/ overhauls, done with dates recorded then and there for analysing the, functional and frequency of breakdown etc.,, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.151 & 152
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MACHINERY AND EQUIPMENT RECORD FORMAT - 6, Organisation Name:, Department:, Section:, History sheet of machinery & Equipement, Description of equipment, Manufacturer’s address, Supplier’s address, Order No. and date, Date on which received, Date on which installed and place, Size : Length x Width x Height, Weight, Cost, Motor particular, , Watts/ H.P./, , r.p.m:, , phase:, , Volts:, , Bearings/ spares/ record, Belt specification, Lubrication details, , Major repairs and overhauls, carried out with dates, , Checklist for preventive maintenance inspection Format 7, The very essential document required to observe, the, functional aspects of each parts, defects and the, remedial measures taken is recorded., , This format enables to program the frequency of, maintenance schedules so as to minimise frequent, breakdown of machinery/equipments., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.151 & 152, , 173
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PREVENTIVE MAINTENANCE RECORD - FORMAT 7, Organisation Name, , :, , Department, , :, , Section, , :, , Name of the Machine :, Machine Number, , :, , Model No & Make, , :, Check list for machine inspection, , Inspect the following items and tick in the appropriate column and list the remedial measures for the defective, items., Items to be checked, , Good working, , Satisfactory, , Defective, , Remedial measures, , Level of the machine, Belt/chain and its tension, Bearing condition (Look, feel,, Listen noise), Driving clutch and brake, Exposed gears, Working in all the speeds, Working in all feeds, Lubrication and its system, Carriage & its travel, Cross-slide & its movement, Compound slide & its travel, Tailstock’s parallel movement, Electrical controls, Safety guards, Inspected by :, Signature :, Name :, Date :, , 174, , Signature of in-charge, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.151 & 152
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Production & Manufacturing, Turner - Advanced Turning, , Related Theory for Exercise 4.6.153, , Terms used in part Drawings and Geometrical tolerances, and symbols, Objective: At the end of this lesson you shall be able to, • state the meanings of various drawing terminology., Glossary of drawing terminology, Abstraction: The reduction of an image or object to an, essential aspect of its form or concept., Acute angle: An angle lesser than 90 degrees., Ascending planes: Flat surfaces not parallel to the ground, or floor planes whose vanishing points appear above the, horizontal line., Background: The most distance zone of space in a, three-dimensional illusion., Concave: A shape that is hollow and curved, like the, inside portion of a bowl., Convex: A shape that curved outward, like the surface of, a sphere., Content: The subject matter of a work of art, including its, emotional, intellectual, symbolic, the matic , and narrative, connotations, which together give the work its total, meaning., Descending planes: Flat surfaces not parallel to the, ground or floor planes whose vanishing points fall below, the horizon line., , Horizontal: Parallel to the plane of the horizon; flat and, even, level., Idealized drawing: A rendering which achieves a, satisfactory resemblance to the subject while, simultaneously eliminating imperfections., Kneaded eraser: A soft, malleable eraser that is used to, lighter values or as an aid in the creation of gradations., Layout: The placement of an image within a two dimensional format., Life drawing: Drawing from live forms in order to gain, visual understanding of the movements, gestures, and, physical capabilities of live bodies as aesthetically pleasing, art forms., Line: The pathway of a moving point as in the trail of a, scratch, a brush stroke, or the engraved deposition of, drawing material resulting from dragging a tool over a, receptive surface; visible by contrasts in value., Line quality: The visual traits and /or expressive character, of lines., Modeling: The change from light to dark across a surface;, a technique for creating the illusion of form and/or space., , Descriptive drawing: Highly detailed renderings intended, to articulately define what is seen., , Multiple perspectives: Difference eye levels and, perspectives used in the same drawing., , Design: A working plan or an arrangement of parts, form,, color etc., , Oblique: A slanting line or plane that is not parallel to the, edges of the picture plane., , Drawing: The act by which an artist records what he or, she sees or feels; The fine art of making a descriptive, visual expression by dragging a tool across a receptive, surface-usually a piece of fine-quality, toothed paper., , Obtuse angle: An angle greater than 90 degrees., , Full range: A complete gradation of tonal values from the, lightest to the darkest values whether black and white or, in a color context., , Parallel: Extending in the same direction at the same, distance a part, so as never to meet., , Geometric shape: Shape created by mathematical laws, and measurements, such as a circle or a square., Ground plane: The flat, horizontal plane on which the, view stands that extends to the horizon., Horizon line: A line corresponding to the eye level of the, viewer in linear perspective; Contains the vanishing points, in a one -point or two-point perspective drawing., , Orthogonal line: In linear perspective, an oblique line, that is drawn using a vanishing point., , Pattern: A repeated compositional element or regular, repetition of a design or single shape., Perpendicular: At right angles to a given plane or line, exactly upright or vertical., Perspective: A mathematical method of representing, forms as they recede in space and diminish in size using, converging lines that meet a central vanishing point on the, horizon line., , Copyright @ NIMI Not to be Republished, , 175
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Pictorial: Refers to a picture, not only its actual twodimensional space but also its potential for three, dimensional illusion., , Texture: The surface character or tactile qualities, experienced either through the sense of touch or through, the imagination., , Picture plane: the actual flat surface, or opaque plane,, on which drawing is produced. It also refers to the, imaginary, transparent "windows of nature" that represents, the format of a drawing mentally super imposed over realworld subject matter., , Three-dimensional: Having height, width and depth;, synonymous with form., , Planer analysis: A structural description of a form in which, its complex curves are generalized into major plane zones., , Three-point perspective: A system for depicting threedimensional depth on a two dimensional surface. In, addition to lines relending to two points on the horizon,, lines parallel and vertical to the ground appear to converge, to a third vanishing point located either above or below the, horizon line., , Plane: A perfectly flat surface as a geometric plane, or, floor plane;, Profile: The shape of a head (or) face (i.e.) seen or drawn, from the side., Rectilinear shapes: Two-dimensional shapes that are, characterized by having four sides that meet one another, at right angles; shapes based upon rectangle and squares., Render: To draw with an unusually high degree of detailed, representation., Scale: Size and weight relationships between forms., Sketch: A drawing, or an act of drawing done quickly with, minimal or no elaboration, but effectively captures the, essential form in space, with basic light and shadow., Tangent: Touching a curved surface at one point but not, intersecting it., Taper: To decrease gradually in width or thickness., , Three-dimensional space: the illusion of volume or, volumetric space., , Two -dimensional: Having height and width; synonymous, with shape., Two dimensional space: Space that has height and width, with little or no illusion of depth., Two-point perspective: A form of linear perspective which, the line receding into space converge at two vanishing, points on the horizon line(eye level), one to the left of the, object being drawn and one to the right., Unit of measure: A portion of a complex shape or threedimensional form that is used to measure all of the order, elements within the shape or form-the head serves as a, good unit of measure for determining proportional, relationships within human figure., Working drawings: The studies artists make in, preparation for a final work of art., , Geometrical tolerancing, Objectives: At the end of this lesson you shall be able to, • define geometrical tolerance, • state the necessity of using geometrical tolerances, • list the recommended symbols for tolerancing under the three groups of form, attitude and location., Form i.e. straightness, flatness, roundness, cylindricity, and profile of a line and a surface, Attitude i.e. parallelism, squareness and angularity, Location i.e. position, concentricity and symmetry, Definition of geometrical tolerance, Geometrical tolerance is the maximum permissible overall, variation of form or position of a feature., Reason for using geometrical tolerance, This will help the operator to produce the components,, particularly those parts which must fit together precisely., 176, , To have an international system which will overcome the, usual language barrier. This is achieved by the use of, symbols which represent geometrical characteristics., General principles of geometrical tolerances, The geometrical tolerance consists of a frame which, contains a symbol, representing the geometrical tolerance, zone, in this instance 0.05 for the characteristic of, parallelism. The symbol for flatness is shown, accompanied by the tolerance zone figure of 0.02 in the, lower frame. (Fig 1), Notice that from each of the frames a leader is drawn, so that it is normal, i.e. at 90° to the relevant face and, ending with an arrow-head against the face., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.153
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Characteristic, , Symbol, , Cylindricity, Profile of a line, Profile of a surface, The application of symbols is indicated in fig 3, where, (3a), (3b), (3c) & (3d) show the use of geometrical, tolerances controlling the straightness of a circular, section part. In (3a) and (3b) the leader lines from the, tolerance frame end in an arrow-head against the axis, applies to the full length of the part. The interpretation, at (3a) shows that for functional acceptance, the entire, main axis must lie between two parallel straight lines, 0,1 apart in that plane. At (3b) the symbol for the diameter, ® precedes the tolerance. This means that the entire, main axis must lie within a cylindrical tolerance zone 0.1, mm diameter., Notice also that from the ‘parallelism’ frame, another, leader is drawn terminating in a blacked-in equilateral, triangle on a projection drawn out from the base line., The blacked-in triangle (about 4.5 mm high from base to, apex) is the symbol used to represent a datum face or, line., , Figures (3c) and (3d) show the same geometrical, tolerance, applied this time to the diameter dimension of, the smaller diameter of the part., This means that the geometrical tolerance applies over, the length of the dimensional feature only., , An alternate method of arranging the frames and symbols, is shown in Fig 2 where the datum is given a letter and a, frame of its own and an independent leader line ending, in the blacked-in triangle, inverted and drawn against, the actual component base line. The datum letter ‘A’ is, then added as an extra component in the geometrical, tolerance frame., , Recommended symbols for geometrical tolerancing, Geometrical tolerances are arranged into three groups., They are tolerances of form, of attitude and of location., Tolerances of FORM are identified by the use of symbols, for the following characteristics., Characteristic, Straightness, Flatness, , Symbol, , Figure (3e) and figure (3f) deal with the geometrical, tolerance for flatness of a surface, where the symbol for, flatness is followed by the tolerance figure of 0.05. This, figure indicates that the actual surface (as previously, shown in Figure 1) must be between two parallel planes, 0.05 apart. If a particular form of direction is prohibited,, then this is stated in a note form against the tolerance, frame. Eg. ‘Not concave’., , Roundness, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.153, , 177
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In Fig.6 the geometrical tolerance is applied to linear, dimensions controlling the profile. The rectangular ‘boxes’, around the 250 centre dimension and the 50 radius is the, method used to indicate theoretical dimensions i.e. the, dimensions relevant to perfect form., , The geometrical tolerance controlling roundness of a part, is shown in figures (3g), (3h) and (3j). The interpretation, for (3g) and (3h) is that the true form of the periphery of, the part at any cross-section perpendicular to the axis, must lie between two concentric circles whose radial, distance apart is 0.02 for (3g) and 0.03 for (3h)., For the sphere shown in (3j) the geometrical tolerance, applies to concentric circles with the radial distance apart, 0.04 at the periphery at any section of maximum diameter., , The sphere controlling cylindricity is shown in Fig 4. Here, the interpretation shows, that for acceptance, the surface, of the part must be within two coaxial cylinders, whose, radial distance apart is 0.05., , The interpretation of the geometrical tolerance is that the, actual profile must be between two lines which touch a, succession of circles 0.2 dia. whose centre lies on the, theoretical profile., Tolerances of attitude are identified and indicated by the, use of symbols for the following., Characteristic, , Symbol, , Parallelism, Squareness, Fig.5 shows the method of applying a geometrical tolerance, to a curved surface. The symbol is followed by the tolerance, 0.05 which means that the actual surface must lie between, two surfaces enveloping a succession of sphere 0.05, diameter whose centre lies on the theoretical surface., , 178, , Angularity, A typical application of tolerances for these three, characteristics is shown in figures 7, 8 and 9. Fig. (7a), (7b) and (7c) show the application of tolerancing to control, ‘parallelism’. (7a) shows that the axis of the upper hole, must lie between the two lines 0.08 apart which are parallel, with the datum axis, i.e., the axis of the lower hole, as, indicated by the leader ending in the blacked-in triangle., In (7b) the method uses a separate datum letter ‘A’, which is added to the frame after the tolerance of 0.05, diameter. (Note the symbol Ø.) The requirement is that, the upper hole axis must lie within a cylindrical zone, 0.05 diameter with its axis parallel with the axis of the, datum hole ‘A’. Fig (7c) shows a component whose upper, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.153
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surface must be between two parallel planes 0.05, apart, parallel with the bottom datum surface. While, the overall tolerance zone is 0.05 as shown in the, upper section of the frame, the figures in the lower, section of the frame stipulate that over any length of 100, the parallelism tolerance is reduced to 0.02., , This shows that the right hand end face must lie between, two parallel planes 0.05 apart, which are perpendicular to, the datum axis. (8c), , Here the datum surface is indicated by a leader from the, frame. The requirement is that the right hand face must, lie within the two parallel planes, 0.05 apart, which are, perpendicular to the datum surface. (8d), , Examples of the application of the geometrical tolerance, for ‘squareness’ are shown in (8a) (8b) (8c) with (8a) (8b), and (8c) using the separate box method for indicating the, datum., The interpretation is as follows., The axis of the vertical hole must lie between two parallel, lines, 0.05 apart, which are perpendicular to the common, datum axis ‘A’ of the two horizontal wholes. (8a), The axis of the upper cylindrical portion must lie within, a cylindrical tolerance zone of 0.01 diameter, the axis of, which is perpendicular to the datum surface ‘A’. (8b), , Geometrical tolerances for the control of ANGULARITY, are shown in figures (9a) (9b) and (9c)., The figure (9a) shows that the requirement is the axis of, the hole must lie within the cylindrical tolerance zone 0.1, diameter, the axis of which must be included at the, theoretical angle of 60° to the datum surface A., In (9b) the requirement is that the right hand end face, must lie within the two parallel planes 0.08 apart which, are inclined at the theoretical angle of 75° to the datum, axis A of the through hole., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.153, , 179
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Figure (10b) shows the hole with the same true positions,, but with the geometrical tolerances arranged to give greater, tolerance along the horizontal axis.The resulting, requirement is that the axis of the hole must lie within a, rectangular box whose sides are 0.03 and 0.06, and length, equal to the width of the component., , Figure (9c) shows a component whose upper angle, face, must lie between the two parallel planes 0.05, apart which are inclined at the theoretical angle of 35°, to the base, the datum surface. Notice that the theoretical, angle in each example is boxed., , Tolerances of location are identified and indicated by, the use of symbols for the following characteristics., Characteristic, , In (10c) the two holes are shown with their true position, spaced at 45° on a 30mm pitch circle radius.The, geometrical tolerance shows that each actual hole centre, must lie within a cylindrical zone 0.08 diameter whose, axis lies at the true centre position. The tolerance cylinders, are disposed relative to the two datum features, namely, the axis of the smaller bore and the right hand end face., The datum letters are included in the tolerance frame., , Symbol, , Position, Concentricity, Symmetry, Figures (10), (11), (12) show typical examples of these, characteristics and symbols. In Figure (10a) the hole centre, dimensions of 25 and 30 are boxed to show that these, are the theoretical dimensions. The geometrical tolerance, requires that the hole centre must lie within a cylindrical, zone 0.05 diameter. The use of theoretical positions, also, known as ‘true positions’, implies that the axis of the, cylinder is square with the plane of the drawing., 180, , Examples of geometrical tolerance for ‘CONCENTRICITY’, are given in figures. (11a), (11b) and (11c). The, interpretations are as follows., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.153
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In figure (11a) the axis of the smaller diameter must lie, within the cylindrical zone 0.08 diameter which must, be coaxial with the datum axis i.e. the axis of datum, diameter ‘A’., , -, , (12a) the axis of the hole must lie between two, parallel planes, 0.08 apart which are symmetrically, disposed about the mean axial plane of datum width, ‘A’ and ‘B’, , In figure (11b) the axis of the two end portions must lie, within a cylindrical tolerance zone 0.08 dia., , -, , (12b) the mean plane of the slot must be between, two parallel planes, 0.05 apart symmetrically, disposed about the mean plane of the datum width, ‘W’, , -, , (12c) the median planes of the two end slots must, be between two parallel planes, 0.06 apart., , Figure (11c) The axis of the large central portion must, lie within a cylindrical zone 0.1 diameter which is coaxial, with the mean axis of the datum diameters ‘A’ and ‘B’., (Notice that to indicate the requirement of the mean axis, the datum letters are separated by a hyphen and enclosed, in the same compartment of the tolerance frame), , The geometrical tolerance of ‘SYMMETRY’ follows in, figures (12a), (12b) and (12c) where the interpretations, are:, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.153, , 181
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A detailed drawing which indicates geometrical tolerances. (Fig.13), , 182, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.153
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Geometric tolerance classes and types, A geometrical tolerance is the maximum permissible overall, variation of from or position from that shown in the drawing., , Class, Form, , Profile, , Orientation, , Location, , Run out, , Type, , Geometrical tolerances are applied apart from dimensional, tolerances, where it is necessary to control more precisely the form or shape of some feature of the part because of its functional requirements., Symbol, , Reference entry, , Straightnes, , Surface of revolution, axis,, straight edge, , Flatness, , Plane surface (not datum plane), , Circularity, , Cylinder, cone, sphere, , Cylindricity, , Cyclinder surface, , Line, , Edge, , Surface, , Surface (not datum plane), , Angularity, , Plane, surface, axis, , Parallelism, , Cyclinder, surface, axis, , Perpendicularity, , Planar surface, , Position, , Any, , Concentricity, , Axis, surface of revolution, , Symmetry, , Any, , Circular, , Cone, cylinder, sphere, plane, , Total, , Cone, cylinder, sphere, plane, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.153, , 183
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Production & Manufacturing, Turner - AdvancedTurning, , Related Theory for Exercise 4.6.154-156, , Automatic lathe - types - parts, toolholders, theory of calculation, Objectives: At the end of this exercise you shall be able to, • differentiate between a centre lathe and a production lathe, • list and name the parts of a capstan lathe, • specify a capstan lathe, • state the constructional features of a capstan lathe., Automatic lathes, , Single spindle automatic lathes, , Lathes, which are capable of automatically performing a preset cycle of operations by presenting the work, to the cutting tools and of ejecting the finished workpiece,, are known as automatic lathes., , There are many types of single spindle automatic lathes, in use. (Fig 1 ) The automatic screw machine is a, popular type. In a single spindle automatic machine,, only one component at a time is machined and this, machine is used for a wide range of operations., These operations vary from cutting small, screw, threads to machining castings and forgings., , The various types of automatic lathes are:, - automatic turret lathes, - single spindle automatic lathes, - multi–spindle automatic lathes., These machines are usually similar to their standard, types with the addition of automatic features. The degree to which a lathe is made automatic is determined, by the purpose for which it is to be used., Modern automatic lathes are available with the following, features., •, , Load the workpiece (manual)., , •, , Start the machine (manual)., , •, , Circulate the coolant (automatic)., , •, , Perform all cutting operations (automatic)., , •, , Change the speeds, feeds, and tools (automatic)., , •, , Gauge and inspect the finished workpiece (manual)., , •, , Unload the workpiece (automatic)., , •, , Repeat the cycle without attention, operator (automatic)., , from, , the, , Automatic turret lathes, The automatic turret lathe is sometimes called an, automatic chucking machine. It is similar in principle to, the standard turret lathe, and additionally, it is automatic, in operation except for the insertion and removal of the, work., These lathes vary in size and range from heavy duty, lathes for rapid and accurate production of components, to lathes used to manufacture small items from barstock., The feeding of tools, indexing of turret, movement of, turret slides and cross-slides and change of speeds, and feeds are automatically controlled by cams or a, plug board system., 184, , The control of feeds and speeds and the indexing of tools, may be done by cams, plug boards or the numerical, control system., Automatic screw machines, These machines are used to produce screws, bolts, and pins from bar stock. The cross slide, turret slide,, and bar–feed mechanism are all operated automatically., Multi-spindle automatic lathes, Multi-spindle automatic lathes represent an extremely, fast method of producing work. The work may be bar–, fed or held in a chuck. The bars are fed into the spindles, which are located in a spindle carrier. The spindles, are positioned in a circular pattern in the carrier., The carrier which is being operated by an indexing mechanism may accommodate 4, 6 or 8 spindles. The spindle rotates in the carrier and the carrier is indexed from, one tool station to the next tool station, according to the, sequence., The tooling set up for a six–spindle automatic lathe is, shown in Fig 2., , Copyright @ NIMI Not to be Republished
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Tools may be preset in their respective tool-holders or, presetting fixtures which are usually situated away from, the machine. Change over from the manufacture of one, type of component to another type is confined to, change of tape and replacement of the preset tools,, collets and the raw material for the new component., This is done when the machine is numerically controlled., Circular form tools (Fig 3), , The tools are mounted in a cam or gear-operated tool, slides, which operate at right angles and parallel to the, spindle., The difference in operation between multi-spindle and other, automatic lathes is that in a multispindle machine the, rotating work is indexed from tool station to tool station, whilst in the others the tools themselves are indexed., The spindle–carrier assembly is a strong and precisely, made unit. It consists of a spindle carrier, work spindle,, spindle stop and start, and the indexing mechanisms., The nearly radial position of the cross slide directs all, cutting thrusts towards the centre of the carrier. This, arrangement permits heavy feeds, and provides extra, room for tooling without holder interference., The Index error is minimized by the tangential cutting, action., Tools and equipments, A wide range of tools are available for use on automats., The tool-holders used are interchangeable between, machines of the same series and frequently between, stations on the same machine., Standard tool-holders and attachments are designed to, cover most requirements, and when necessary, special holders are available to handle the less common, production processes., , In any type of automatic lathes, turning concave,, convex or any irregular shape on the component is, achieved using form tools. These form tools are of two, types, straight and circular. The straight types are used, for wider surfaces and the circular types are used for, narrower surfaces. Fig 4 illustrates forming operations, performed by straight and circular form tools., By using circular form tools many operations are, combined and performed, all in one stroke, by shaping, the circular form tools accordingly., While using circular form tools, special attention is, given for selecting the correct speeds and feeds. This is, due to the presence of a wider surface area coming, in contact with the circular form tools during the machining., The cross feed ranges from 0.01 to 0.08mm per revolution and the cutting speed is slightly less than that for, longitudinal turning., , Use of cams in automatic lathes, Objectives: At the end of this exercise you shall be able to, • classify the cams used on automatic lathes, • state use of cams in automatic lathes., Fully automatic or semi-automatic lathe machines, which rotates at constant speed, controls the movements, are often controlled with the help of drum cams and, of the tools. The turret head is indexed first and then, cam plates. The lathe tools necessary for production, the tool carriage and/or tool post is moved towards the, are mounted in one or more supports ie. drum turret or, workpiece at the correct feed rate., horizontal turret head. The drum cam or cam plate,, Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.154 & 156, 185, , Copyright @ NIMI Not to be Republished
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Cams are used to actuate various slides in the automatic lathes., , Fig 5 is the tool layout for the job shown in the worksheet, of Fig 4., , Cams may be classified according to their shapes, and mechanical designs into several distinct groups with, the subdivisions numbering a dozen or more., , Fig 6 is the cam layout for the job shown in Fig 4., , For practical purposes, all cams can be divided into, three classes; radial or plate (Fig 1), cylindrical or barrel, (Fig 2) and pivot beam type (Fig 3) which is found, useful in fixture designs., , In fully automatic lathes (generally used for machining bar stock) the workpiece feeding, clamping and, cutting off are also governed by the cam control system., A layout of a cam design worksheet is appended in Fig, 4., The various features considered at the time of preparing, cam design worksheets are sequence of operation,, speeds, feeds, depth of cuts, index of turret and other, slides (front, rear and top)., , 186, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.154 & 156
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inportant SHEET, , Automatic screw machine, , Short stroke, , Work spindle speeds rev/min., Fast, , Distance between turret and chuck, , Minimum, , Travel, , 46, , 35, , R.H, R.H, , Sequence of operation, , Feed stock, , 4995, , Throw, in mm, , Feed, mm, per, rev., , Dwell, , Index turret (one, station), Centre, , End of bar, , Dwell, , To clean up, , 3, , 0.15, , Index turret (one station), Turn Φ 8 and drill Φ 5.25, Dwell, To clean up, , 14.25, , 0.125, , Index turret (one station), Drill Φ 2.5 hole, Drop back To clear, Form, (over lapped), Dwell, To clean up, Index turret (one station), Cone bottom of Φ 5.25, Dwell, To Clean up, Index turret (one station), Ream Φ5.6 and cone, Dwell, To clean up, Index turret (over lapped), Cut off, Cross-slide(R), Cut off, Cross-slide(R), , Cutting speed m/min., , 6.5, , 0.07, , 2.4, , 0.012, , Turning, Drilling 5.25 dia., Drilling 2.5 dia., , Revs.of work spindle, for each over, Correc, operalapped ted, tion, open, , 0.07, , 26, , 4 1/2, , 26, , 26, , 4 1/2, , 20, , 29, , 5, , 6, , 1, , 26, , 26, , 4 1/2, , 114, , 117, 6, , 20, 1, , 26, , 26, , 4 1/2, , 93, , 93, , 16, , 9, (204), 6, , 1 1/2, (35), 1, , 26, , 26, , 4 1/2, , 46, , 50, 6, , 8 1/2, (1), , 26, , 26, , 4 1/2, , 200, , 12.75, , 0.25, , 51, , 53, 6, , 9, 1, , 1.5, 0.5, , 0.05, 0.07, , 26, 30, 7, , 26, 32, 3, , (4 1/2), 5 1/2, 1 1/2, , 12, , 2, , Clear cut off tool, Totals before correction, In an another type of single spindle automatic lathe the, slides are operated by individual cams. Fig 7 show the, various tools slides., The cams used on such a machine are shown in figures 8, and 9., , Hundreths, , 26, , 0.005, 3.2, , 150, 82, 46, , 92 1/2%, , 517, , 7 1/2, , Whereas, when one cam is made to actuate one slide,, the design part of it becomes easier. Only that particular, cam may be replaced in case a defect is noted in the, component. Moreover a set of cams designed for a, particular component may be useful for the manufacture, of components with the same shape and design, but, with slight dimensional variations., , A single cam to control the various slide movements, is a complicated one for designing and manufacturing., Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.154 & 156, , Copyright @ NIMI Not to be Republished, , 187
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Differences between centre lathe and production lathe, Centre lathe, , Production lathe, (Capstan and turret lathe), , 1, , Single-way tool post holds only one tool., , Four-way tool post accommodates different types, of tools in four ways., , 2, , At the end of every operation, the tool needs, to be changed. It requires more operation time., , Pre-set tool can be indexed. It avoids tool setting time., , 3, , Not suitable for production jobs., , Suitable for production jobs, , 4, , Most suitable for tool room jobs., , Most suitable for mass production jobs., , 5, , High skill is necessary to operate a centre, lathe, , A semi-skilled person can operate, pre-set turrent, of a capstan or turret lathe, , 6, , Combination cuts are employed, with difficulty., , Combination cuts can be given both on carriage, and turret head simultaneously., , 7, , By using a single point tool, various sizes of, thread can be cut, , Tap and dies are used to form threads; sometimes, short lead screw is provided to cut threads with, chasers, , 8, , Tailstock is provided to hold cutting tools, like drills and support the job with centres., , Turret is provided to hold six or more tools, , 9, , There is no separate bed over the, main bed for the tool movement, , There is an auxiliary bed provided for production, (capstan) for the auxiliary slide., , 10, , Job cannot be fed continuously after, completion of operation., , Job can be fed by a bar -feed attachment, , 11, , Time taken is more for producing a, workpiece., , Time taken is less for producing a workpiece, , 12, , The cost of machine is low., , The cost of machine is high., , 13, , Trips and stops are not provided for, stopping the tool slides., , Trips and stops are provided for rapid stopping and, starting, , 14, , Generally chuck work and in between, centre work can be carried out., , Generally bar works can be carried out., , 15, , The manufacturing cost of components is more., , The manufacturing cost of components is comparatively lower., , 188, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.154 & 156
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Tool-holding devices, The wide variety of work performed in a capstan lathe in, mass production necessitated designing of different types, of tools and tool-holders for holding the tools for typical, operations. The tool-holders may be mounted on turret, faces or on crossslide tool post, and may be used for, holding tools for bar and chuck work. Certain tool- holders, are used for holding tools for both bar and chuck work, while box tools are particularly adopted in bar-work. In the, capstan or turret lathe practice, the whole assembly of, the holder and its tool is designated according to the type, of the holder. Thus a slide tool holder with the tool mounted, in it is called a 'Slide tool' and a knee tool-holder with the, tool fitted into it is called a 'Knee tool'. Special tool-holders, are also sometimes designed for special purposes. The, most important and widely used tool-holders are listed, below., , the shaft is rotated by hand. On some of the more, elaborate turret lathes the stop shaft for the turret faces, has six sides with stops, and is automatically rotated to, synchronize with the turret., A similar principle is adopted in respect of the cross slide stops on most machines. A rotating bar is mounted, on the side of the cross-slide and carries four adjustable, stops at each end. Hand rotation of the shaft is used to, bring the stop at each end and to position for any particular, tool. To prevent swarfs from getting in the unit, it is generally, provided with a cover., Cutting speed, Similar to a centre lathe, the cutting speed in a capstan, or turret lathe is the rate at which any point on the work, passes over the tool, and this is expressed in metres per, minute., , – Straight cutter-holder, , Feed, , – Plain or adjustable angle cutter-holder, , It is the amount the tool moves per revolution of the work., This is expressed in mm per revolution., , – Roller steady turning tool-holder., – Recessing tool-holder., – Knee turning tool-holder., – Stop and centre drill-holder., – Combination tool-holder., Stops and trips, One of the features enabling the capstan and turret lathes, to produce quantities of similar parts is the system of, stops and trips for controlling the movements of the cutting, tools., The stops for controlling the travel of the saddle, and of, the turret slide of a turret lathe, are carried on a shaft, suspended on brackets from the front of the machine bed., An illustration of this, as applied to the saddle on a small, capstan lathe, is shown in Fig.1, where the stop shaft is, at the bottom of the illustration., , Depth of cut, It is the perpendicular distance measured between a, machined and an un-machined surface., Bar-feeding mechanism, The capstan and turret lathes while working on bar work, require some mechanism for bar-feeding. The long bars, which protrude out of the headstock spindle require to be, fed through the spindle up to the bar-stop after the first, piece is completed and the collet chuck is opened. In, simple cases, the bar may be pushed by hand. But this, process unnecessarily increases the total operational, time, because the spindle and the long, Principal parts of capstan and turret lathes, The capstan lathe has essentially the same parts as the, engine lathe except that the turret complex mechanism, incorporated in it makes it suitable for mass production, work. The different parts of a capstan lathe are shown in, Figs 1a,b and c., 1 Headstock, 2 Cross-slide tool post, 3 Hexagonal turret, 4 Saddle for auxiliary slide, 5 Auxiliary slide, 6 Lathe bed, 7 Feed rod, 8 Saddle for crossslide, , 9 Feed stop rod for turret, Provision is made for four stops round the shaft so that, 10 Hand wheel for turret slide., the travel of four tools may be controlled at any particular, time. It is arranged that the stop first trips out the feed, and then serves as a dead stop for the small handoperated, movement necessary to complete the travel. For bringing, each stop in position, when all the four are being used,, Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.154 & 156, , Copyright @ NIMI Not to be Republished, , 189
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Generally an all-geared headstock is used for rapid change, of the spindle speeds. This should be selected prior to, an operation by changing the lever or pressing the, speed-changing button. The spindle is hollow and the barstock should be passed through it., On the right side of the capstan lathe there is a hexagonal, turret head mounted on a vertical spindle. The turret face, has a bored hole on the centre which receives lengthy, tools like drills, reamers, holders for tools and split bushes., A star wheel is provided in front of the machine which, operates manually for the to and fro motion of the turret, head assembly. Power feed is also provided for the turret, head with suitable feed rate. The turret head is fully, retracted, and at the end of its travel a turret indexing, mechanism is automatically operated for the next position, of the tool. Each movement of the tool will be controlled, by adjustable stops. Each stop is set for correct travel of, the tool movement, which will stop further movement of, the tool., The type of the cross-slide depends upon the size of the, machine. The slide is positioned in between the headstock, and turret head over the saddle. If it has two tool posts,, one is at the front and the other is at the rear end of the, slide. The front tool post is moving inward to bring the, cutting tool into operation. The rear tool post is moving, inward when the front tool post is moving outward. The, rear tool post actually does the ending operation like parting, off, with or without chamfering. All the lateral movements, of the saddle and the cross - slide will be controlled by, trips and stoppers for correct movement of the tools in, operation., , A capstan lathe is specified by providing the following, features, -, , The maximum diameter of rod that can be passed, through the headstock spindle., , -, , The swing diameter of the work that can be rotated, over the lathe bedways., , -, , The minimum and maximum spindle speeds., , -, , Number of feeds available to the carriage and turret, saddle., , -, , The capacity of the motor. (H.P. of the machine), , The capstan lathe: construction, A capstan lathe consists of a lathe bed, headstock,, turret head or slide, saddle, carriage, cross-slide, tool, posts and feed rod., , The feed-rod controls the motion for the carriage in the, same way as in an engine lathe., The stop-rod is mounted below the bed in between the, gearbox housing and feed-rod housing. It has four splines, over the periphery to accommodate the stoppers in, measuring positions with respect to the related turning, operations for the saddle movements., bar must come to a dead stop before any adjustment can, be made. Thus in each case unnecessary long time is, wasted in stopping, setting and starting the machines., Various types of bar-feeding mechanism have, therefore,, been designed which push the bar forward immediately, after the collet releases the work without stopping the, machine, and thereby enable the setting time to be reduced to the minimum., Working principle of the bar feeding mechanism, (Fig 2), , The lathe bed of a capstan lathe is quite similar in, construction to that of a centre lathe, the only difference, is in the ways of the bed. The bed ways are provided flat, instead of in a combination (Vee and Flat) to receive, heavy loads during multiple cutting., 190, , The bar 6 is passed through the bar-chuck 3, through, the spindle of the machine and then through the collect, chuck. The bar-chuck 3 rotates in the sliding bracket body, 2 which is mounted on a long slide bar. The bar chuck 3, grips the bar centrally by two set screws 5 and rotates, with the bar in the sliding bracket body 2. One end of the, Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.154 & 156, , Copyright @ NIMI Not to be Republished
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chain 8 is connected to the pin 9 fitted on the sliding bracket, 10 and the other end supports the weight 4, the chain, running over to fixed pullys 7 and 11 mounted on the slide, bar. The weight 4 constantly exerts an end thrust on the, bar-chuck while it revolves on the sliding bracket and forces, the bar through the spindle, the moment the collet chuck, is released. Thus bar-feeding may be accomplished, without stopping the machine., , Turret heads, Objectives : At the end of this lesson you shall be able to, • state what is a turret head, • list the types of turrets, • state the constructional and functional features of a turret head., The turret head, The turret head is also known as a tool head. The turret, is a six sided (hexagonal) block mostly and it is carried, on the bed of the machine for accommodating and, bringing forward the tools. Each of the faces of the hexagon, is accurately machined, square to the axis of the lathe, and has four tapped holes to accommodate the clamping, bolts of the tool-holders or attachments. At the centre, of each face is a through hole into which the shanks, of the tool-holders may be accommodated and clamped., A pad bolt is often employed for the purpose of clamping., (Fig 1), Smaller types of capstan lathes have the turrets not, hexagonal but circular. They have six holes for, accommodating the tools. During the cycle of operation, it is necessary to bring each tool into position for its, work by indexing and locating the turret to the, successive position., On the turret lathe, the turret head is supported on a, free bearing. The turret can be pulled round easily by, hand when the clamping arrangement has been released., The turret is located in each of the six correct positions, by some hand-operated plunger. The machine operator, releases the clamp and locates the plunger before, indexing the turret manually., On the capstan lathe, means are provided whereby the, turret is automatically indexed to its next position, when, it reaches the extreme end of its withdrawal movement, from the previous operation., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.154 & 156, , 191
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Types of turret heads, Turret heads are classified according to the axis of rotation, which may be horizontal, vertical or inclined., Turret lathes with turret heads of vertical and inclined, axis are provided with cross-slides whereas those with, horizontal axis turrets have no cross-slides since the cross, feed of the tool is effected by the turret slide itself., Constructional features of a turret head with vertical, axis (Fig 2), , number corresponds to the number of the turrets', tool position is indexed through a gear transmission, simultaneously with the turret. The stops limit the travel, of the turret relative to the saddle (A). The stops are, adjusted when the machine is set up for operation., In the capstan lathe turret head stops are fitted in the, saddle. The overhang increases as the turret moves, towards the workpiece held in the headstock. This, overhang limits the strength and consequently the, capacity of the machine. In the turret lathe the overhang, is constant, permitting a heavier work load. Slide stops, in this type are fitted in the lathe bed. (Fig 3), In each machine the sliding movement of the turret, head is made by operating a handwheel. This turns the, pinion which mashes with the rack in the bed., Movement of the turret head back from the headstock, automatically indexes the turret., , This is movable along the bed-ways. The turret head can, be indexed by hand or automatically on the withdrawal of, the turret slide. As this takes place, the fork (1) along, with the cam (5) turns relative to the fixed stop (2). The, cam lifts the turret (9) through rollers (6). The flanges, (7 and 8) of the claw clutch, which serve to lock the, turret, come out of engagement., As the fork turns further, the ratchet gearing (3) indexes, the turret into the next position.The lock pins (11) prevent, the turret from overrun, performing a preliminary locking, function. When the slide is advanced the fork (1) turns in, the opposite direction, the cam (5) lowers the rollers (6), with turret (9) and flanges (7) and (8) of the claw clutch, come back into engagement, finally locking the turret in, position. The locking force is adjusted with the nut (10)., The stopper roller (12) with adjustable stops, whose, , Roller box turning tools, Objectives : At the end of this lesson you shall be able to, • state the purpose of roller box turning tool, • list the types of roller box turning tools, • state the constructional features of each type, • state the functional features of the each type., Roller box turning tools, Plain turning operations may be performed on capstan, and turret lathes by feeding the tool, -, , from the hexagonal turret, by the indexing tool post on crossslide, by feeding tools from both., , 192, , Turning operations carried out from the hexagon turret, provide rigid support to the tool for making heavy cuts., Tools used in the turret are of special design and are referred, to as box turning tools. Box turning tools are of two, types., , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.154 & 156
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-, , `V' steady turning tools, Roller steady turning tools, , `V' Steady tool–holder (Fig 1), , These holders are for turning brass and for making light, cuts on other free cutting materials. A short length of the, workpiece is hand–machined to the required diameter, and the steady is adjusted to this surface., The cutting tool is set slightly ahead of the Vee, steady. These tools may have single or multiple tool, blocks., A hardened adjustable Vee steady is positioned such, that it just touches the workpiece., The shank of the steady is mounted in an extension, arm in the turret., , In the tangential type the workpiece is supported by, two rollers running on the diameter being cut (following, rollers). The tool can be retracted at the end of the cut, by pulling the handle. By this, scoring of the workpiece, surface turned is avoided. Fine adjustment of the cutting, tool is achieved by the use of the micrometer dial. The, chips flow clear off the tool-holder ensuring that swarf, does not become clogged around the work area. (Fig 3), , Where good surface finish is needed on the turned, portion, it is preferable to have the cutting tool in, advance to the Vee steady, and where concentricity is, of prime importance, the cutting tool may be set behind, the Vee steady., The roller steady tool-holders (Fig 2), These holders are used for most turning operations. Each, holder has a limited size capacity. A short length of, the work is machined to the correct diameter. The, rollers and tool are set on this diameter. The cutting action, forces the workpiece against the rollers, producing a, high burnished finish on the work. The cutting tool is, set in advance of the rollers for most turning operations., This set up produces a good surface finish. Some, steadies are available with rollers set ahead of the cutting, tool., The roller steady tool-holders are of two types., •, , The tangential type (Fig 3), , •, , The ending type (Fig 4), , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.154 & 156, , 193
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In the ending type shown in figure 4 with leading or, forward rollers, the workpiece is supported by two rollers, on a previously cut diameter. Leading rollers ensure, that the diameter being turned is concentric to the, previously turned diameter on which the rollers run., , Figure 5 shows the geometry of a roller box showing, forces on the tool and the rollers., , Figure 6 shows the roller steady tool-holder adjustments., The forces F1, F2 and R1 are also illustrated., , The leading rollers may not produce the same standard, of surface finish., When using the ending type of roller steady tool-holder,, the cutting is taking place on the end of the workpiece., This is made possible by the use of the leading rollers., (Fig 4), , Turret lathes, Objectives: At the end of this lesson you shall be able to, • specify a turret lathe, • name the various attachments & accessories used on turret lathes, • distinguish between horizontal and vertical types of turret lathes., Specification of a turret lathe, , Turret : Pentagon, hexagon or octagon type., , A turret lathe is specified by giving the, , Tool-holders, , -, , maximum diameter of a rod that can be held, , -, , maximum spindle hole diameter, , -, , maximum swing over the bed, , -, , number of spindle speeds, , -, , number of feeds (carriage) cross-slide and longitudinal, , -, , number of feeds (turret carriage), , -, , power required for machine motor and coolant motors., , Straight cutter holder, Plain or adjustable angle cutter holder, Multiple cutter holder, Offset cutter holder, Combination tool-holder or multiple turning head, Slide tool-holder, Knee tool-holder, Drill holder, Boring bar holder or extension holder, Reamer holder, Knurling tool-holder, Recessing tool-holder, Form tool-holder, - straight, - circular, Tap-holder, , Accessories / attachments, Work-holding accessories, Self centering chuck, independent chuck, combination, chuck, air operated chuck, push-out type collet chuck,, draw in type collet chuck, dead length type collet chuck., 194, , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.154 & 156
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Die-holder, Balanced tool-holder (box tool), - V-steady box tool-holder, - roller box tool-holder, Bar ending tool-holder, Attachments, Taper turning attachment, Thread cutting attachment, Horizontal turret lathes are classified as:, - ram type turret lathes, - saddle type turret lathes, - chucking machine., Saddle type turret lathes (Fig 1a), The hexagonal turret is mounted directly on a saddle and, the whole unit moves back and forth on the bed ways to, apply feed. This type of turret lathe is heavier in construction, and is particularly adopted for larger diameter bar works, and chuck works. The machine can accommodate longer, workpieces., Ram type turret lathes (Fig 1b), The ram type turret lathe carries the hexagonal turret on a, ram or a short slide. The ram slides longitudinally on a, saddle positioned and clamped on lathe bedways. This, type of machine is lighter in construction and is suitable, for machining bars of smaller diameters. The tools are, mounted on the square turret and the six faces of the, hexagonal turret. The feeding movement is obtained when, the ram moves from the left to the right. When the ram is, moved backward the turret indexes automatically and, the tool mounted on the next face comes into operation., Chucking machine, The chucking machines are used to machine castings, and forgings that must be held in chucks or fixtures. This, type of machine handles a large variety of work which is, basically the same as that done on standard turret lathes, equipped for chuck work., , Vertical turret lathes, A vertical turret lathe is a machine with a vertical turret, head and a horizontal work table. Most of the operations, performed on a regular turret lathe are also done on this, type of machine. It is preferred for large and heavy work., The principal parts of a vertical turret lathe are the, , -, , base, column, rail, table, saddle and turret head, side head, , Many attachments are used on vertical turret lathes., , Dead stops and trips on capstan and turret lathes, Objectives : At the end of this lesson you shall be able to, • state the necessity of stops and trips, • list the types of stops and trips, • state the constructional and functional features of stops and trips, • types of stop and trip arrangements., Stop and trips, , suspended on brackets from the front of the machine bed., It is arranged that the stop first trips out the feed, and then, serves as dead stop for the small handoperated, movement necessary to complete the travel. For bringing, each stop into position, when several of them are being, used, the shaft is rotated by a hand wheel provided. On, some of the most elaborate turret lathes the stops for, saddle movement, which are four in number are provided on, , Stops and trips are meant for controlling the movement of, the cutting tool on the crossslide and on the hexagonal, turret. They serve the purpose of providing dimensional, accuracy on identical components produced in large, quantities. They minimize delays for measuring and, gauging. The stops for controlling the travel of the saddle, and of the turret of a turret lathe are carried on a shaft, Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.154 & 156, , Copyright @ NIMI Not to be Republished, , 195
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a shaft below the headstock. (Fig 1) The stop shaft for, the turret has six stops which are automatically rotated, to synchronize with the turret. (Fig 2), , The cross-slide is also provided with a shaft with stops, to control the depth of cuts of each tool on the, cross-slide tool post. (Fig 3), , Dead stops, A dead stop terminates the tool travel at a point where, a workpiece diameter or depth is correct to the drawing, specification. (Fig 6), , Finger stops, A finger stop is positioned radially on the hand wheel and, is aligned with a mark on the graduated scales when, the relevant dimension on the workpiece is down to size., There may be three or four finger stops, each aligned, to a different mark on the graduated scale. (Fig 4), Feed trips, A feed trip switches off the power feed to the tool when, the workpiece is almost to size. When the trip device, touches the stop, it trips the power feed. A further, manual movement of the slide, through a previously, determined distance will bring the slide to the dead stop, as shown. (Fig 5), 196, Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.154 & 156, , Copyright @ NIMI Not to be Republished
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Indexing a stop-bar or roll, A `stop-bar' is indexed to the position in conjunction with, the relevant tool. This may be carried out manually by, indexing the bar to present a letter, a record being made, of which letter goes with each tool.In the case of a turret,the, stop-bar will be indexed automatically with the turret and,, therefore, each stop is always presented for the same, turret station. (Fig 7), , Collets used on capstan and turret lathes, Objectives : At the end of this lesson you shall be able to, • list the collets used for bar work on the capstan and turret lathes, • state the constructional and functional features of each type of collet., The collet chuck, Collets provide a means of holding cold-drawn bar, materials or previously machined parts to undergo a, second operation. They maintain an accurate alignment, of the component to be machined with the rotating spindle, axis of the lathe., The working principle of the collet chuck is illustrated in, Fig 1., , The workpiece does not move when this type of collet, is operated; and, therefore, an accurate length of workpiece can be maintained., Draw back type (Fig 3), , The common constructional features of collets have already, been dealt with in the previous exercises., Types of collets, Dead length type (Fig 2), , Copyright @ NIMI Not to be Republished, , Production & Manufacturing : Turner (NSQF Level-5) - RT for Ex - 4.6.154 & 156, , 197
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This is also referred to as draw in collet. This collet is, usually screwed to a draw bar or tube which draws the, collet into the sleeve causing it to grip the bar. A keyway, located in the body of the collet accommodates the key, in the sleeve preventing rotation of the collet, which, ultimately prevents the collet getting unscrewed from, the draw bar during operation. This type of collet is not, suitable for accurate length workpiece as it tends to, pull the workpiece away from the bar-stop when closing., , Their range of adjustment is much greater than with solid, collets, usually about 1.5 mm. The collet pads are usually, not suitable for gripping short workpieces. These pads are, available in sets of three or four pieces. The pads are, available to accommodate hexagonal bars also. When, hexagonal bars are held, the bar must be rotated after, inserting so as to get the corners properly engaged., (Fig 6), , Pushout type (Fig 4), When this type of collet is closed by pushing against, the taper of the accommodating sleeve, it tends the bar, also to be pushed along with the collet against the barstop. Unless the turret hand wheel is held by pressing in, the anticlockwise direction, the component length may, show variations., , Master collet with interchangeable liners (Fig 5), , The master piece is of collet shape. This has a tapered, bore into which liners or pads, mostly three in number,, can be fitted. When the pads are fitted to the internal taper, of the master piece, the inner bore that results by the, assembly of the pads accommodates the bar. The, masterpiece controls the grip. The pads are assembled, to the master piece by means of stop screws., The collet pads are used in most of the larger sizes of, bar work., , 198, , Sometimes the collet pads are provided with spring, spacers to keep the collet pads apart when the chuck is, opened making the workpiece loading easier. (Fig 7), , Points to be remembered during selecting a solid, collet, The above type of collets accommodates only one, size of bar for which they are manufactured. If the bar, diameter differs by even 0.1 mm from the nominal size,, the operation of the collet will not be proper and the, accuracy of the collet will be lost., , Copyright @ NIMI Not to be Republished, , Production : Turner (NSQF Level-5) : RT for Ex No. 4.6.154 - 4.6.156
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Clean and deburr the workpiece and form a good chamfer, on the end face of the bar which enters the collet., , If the bar moves under pressure, open the chuck and, readjust the knurled cap., , Check that the collet just fits on the workpiece without, forcing., , Feed for correct adjustment on a manually operated chuck,, by feeling for resistance when closing the chuck. (Fig 9), , A round bar having a scaly unmachined, outer surface must never be held in a collet, chuck., , If long heavy bars are to be held, put the machine in, motion and check that the bar does not move in the collet, when accelerated up to the cutting speed., , Checking the collet tension, Index the bar-stop into position and apply force to the bar, using the star wheel of the turret slide. (Fig 8), , Turret lathes, , When soft materials and thin walled tubes are to be, held, check that no excessive damage has been caused, by the grip of the collet to the surface of the soft bar or, the diameter of the thin tube., , Comparison between turret and capstan lathes, Turret lathe, , Capstan lathe, , 1 The turret is mounted on the saddle which slides, directly on the bed., , The turret is mounted on an auxiliary slide which slides, on the saddle., , 2 The construction provides utmost rigidity to the tool, support as the entire cutting load is taken up by the, lathe bed directly., , The auxiliary bed feeds the tools into the work. The, overhanging of the auxiliary bed from the stationary, saddle presents a non-rigid construction which is, subjected to bending, deflection or vibration under heavy, cutting loads., , 3 The turret lathe can operate under severe cutting, conditions, accommodating heavier workpieces with, high cutting speeds, feeds and depth of cuts., , The capstan lathe can be operated under light cutting, conditions, accommodating workpieces with high cutting, speeds, feeds and less depth of cuts., , 4 The turret lathes are capable of turning bars up to 200, mm in diameter., , The capstan lathes are capable of turning bars up to a, maximum of 60 mm diameter only., , 5 Larger and heavier works can be done on turret lathes., , Smaller and lighter bar work can be done on a capstan, lathe., , 6 In the turret lathe, the hand feeding is a laborious, process due to the movement of the entire saddle, unit., , On a capstan lathe, the hexagonal turret can be moved, back and forth rapidly without having to move the entire, saddle unit., , Copyright, @ NIMI, to: RT, beforRepublished, Production : Turner, (NSQF Not, Level-5), Ex No. 4.6.154 - 4.6.156, , 199
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The constructional features of a turret lathe, , Types of turret lathes, , A turret lathe consists of a bed, an all-geared headstock,, and a crossslide on which a four-way tool post is mounted, to hold four different, single point tools. A tool post fitted, at the rear of the cross-slide holds a parting tool in, an inverted position. The tool post mounted on the, cross-slide is indexed by hand. In a turret lathe there is, no tailstock but in its place a hexagonal turret is mounted, on a saddle which is sliding on the bed. The six faces of, the turret can hold six different tools. The turret may be, indexed automatically or manually and each tool may be, brought in line with the lathe axis in a regular sequence., The workpieces are held in collets or on chucks., The longitudinal movements of the turret and cross-feed, movement of the crossslide are controlled by adjustable, stops. These stops enable different tools set at different, positions to move by a predetermined amount for, performing different operations on repetitive workpieces, without measuring the length (or) diameter of the machined, surfaces in each case., , Turret lathes can be classified into two main groups, -, , Horizontal type turret lathe., Vertical type turret lathe., , Horizontal type turret lathes, They are lathes which perform all the operations in a, horizontal position with the help of a cross-slide tool post, and turret head. These operations include turning, drilling,, boring, reaming, thread cutting, necking, chamfering and, cutting off., Vertical turret lathes, These are lathes with a vertical turret head and a horizontal, work table. All the operations performed on a regular turret, lathe can be done on this type of machine also. It is, preferred for large and heavy workpieces., Parts of a horizontal turret lathe. (Fig 1), , These special characteristics of the turret lathe enable it, to perform a series of operations such as turning, drilling,, boring, reaming, thread cutting, necking, chamfering,, cutting off and many other operations in a regular, sequence to produce a large number of identical pieces, in a minimum time., , 200, , Copyright @ NIMI Not to be Republished, , Production : Turner (NSQF Level-5) : RT for Ex No. 4.6.154 - 4.6.156
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Types of tool - holders in capstan and turret, Objective: At the end of this lesson you shall be able to, • state the different types of tool-holders and their uses., The following are the different types of tool-holders., Single cutter turner tool-holder, Roller steady turning tool-holder, Multiple cutter turner tool-holder, Combination end face and turner tool-holder, Quickacting slide tool-holder, Centre drilling tool-holder and bar-stop, Adjustable knee tool, Die head, Clutch type tap and die-holder, Floating tool-holder, Combination facing and spotting drill-holder, Taper shankdrill socket-holder, Drill chuck (drill-holder), Combination stock stop and centre-holder, Flanged tool-holder, Knee turning tool-holder, Recessing and boring tool-holder for boring, Recessing tool-holder., , Roller steady turning tool - holder (Fig 2), , Roller steady turning tool-holder is used mainly for turning, external diameters while a fairly good finish is needed on, the component. The roller steady supports the job when, a lengthier job is to be turned., Recessing and boring tool-holders (Fig 3), , Uses of the common tool holders used on turret lathes, Knee turning tool-holder (Fig 1), A knee turning tool is used while the job is held rigidly, in a chuck or fixture. It is used for machining components, by combined operations. The rigidity of this tool-holder, can be increased by using the overhead support bar, protruding from the headstock., Recessing and boring tool-holders are used in combination, for internal recessing and boring., Bar-stop and centre drill tool-holder (Fig 4), , A bar-stop is used for setting the bar stock protruding, to the required length to a preset position from the chuck., A centre drill tool-holder is used for centre drilling where, drilling is to be done in a job., , Copyright, @ NIMI, to: RT, beforRepublished, Production : Turner, (NSQF Not, Level-5), Ex No. 4.6.154 - 4.6.156, , 201
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Floating reamer-holder (Fig 5), , Combination facing and start drilling holder (Fig 6), , Where reaming is to be done in a turret lathe, a floating, reamer-holder is used to ream a drilled hole. The floating, holder facilitates by aligning itself with the axis of the drilled, hole without causing much load on the reamer., , Combination facing and start drilling holder is used to face, the end of the job and to provide a small hole for short, depth ready for a drilling operation., , Knee turning - holder and combination tool - holder, Objective : At the end of this lesson you shall be able to, • state the constructional features of a knee turning tool-holder and a combination tool-holder., Knee turning tool-holder (Figs 1a and 1b), , Combination tool-holder (Figs 2a and 2b), Work which is held in a chuck or in a turning fixture is, fairly rigid, and needs no additional support while machining, takes place. If the tool-holder mounted on the turret head, is meant for combined operations, like turning and forming,, the tool-holder must also be rigid and well supported. It, is also essential that some arrangement should be provided, to take up the heavy load which comes on the turret head., Such combination of operations is usually carried out with, a knee tool-holder. The rigidity of this type of tool-holder, can be increased by using the overhead support bar, protruding from the headstock. This engages the guide, bush on the tool-holder and maintains the alignment of, the turret and the spindle axis, preventing deflection of the, turret by the cutting force applied., A boring bar can also be fitted so that a hole can be, machined at the same time as the external surface is, being machined. The chuck or fixture should be fitted with, a guide bush to pilot the end of the boring bar, and again, maintain the geometry of the tool by reducing tool, deflections., 202, Production : Turner (NSQF Level-5) : RT for Ex No. 4.6.154 - 4.6.156, , Copyright @ NIMI Not to be Republished
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ie. by two combination tool-holders, one in the machine, and the other out for tool maintenance. When the tools, have been reground they are preset in position and the, complete tool-holder is changed. Presetting of boring tools, is facilitated by the use of a boring bar cutter micrometer., (Fig 3), The knee turning tool-holder has provision for only one, turning tool, and it has a greater range of adjustment., But the adjustment for positioning the turning tool head, in the combination type tool-holder is merely that of a tool, overhang in the tool post., , A further development of the knee tool-holder is the, combination tool-holder which can be fitted with two turning, tools and a boring bar. Thus simultaneous machining, operations are possible. By increasing the number of tools, in the boring bar, multi diameter bores can be machined, at the same time., Such set ups involve more complex and time consuming, tool setting and are only economic where the time saved, in machining outweigh the setting time. The machine down, time for setting can be reduced by the use of pre-set tooling,, , Methods of producing external threads on capstan lathes, Objectives : At the end of this lesson you shall be able to, • state various methods of producing external threads on capstan lathes, • state the construction and function of a self-opening die head, • state the types of self-opening die heads, • list and name the parts of a die insert., External threads are generally manufactured, -, , by using a single point tool with self opening die heads, by thread rolling heads., , Self-opening die heads (Fig 1), , In addition to dies/chasers for standard threads, many, dies/chasers for special threads are also available., The die head is fed to the work by the operator who then, allows it to feed itself along the work, and follows up, with the turret. The turret stop is set slightly short to the, thread length. When the die head movement is stopped, by the turret stop, the front portion of the die head continues, to feed forward under the self-feeding action until it is, pulled clear of the detent pin., Long accurate threads need a positive method of feeding, the die head over the work. On capstan lathes this is, achieved with a hexagon turret, leadon attachment. If the, machine is equipped with a crossslide and the thread, chasing attachment, the crossslide is linked to the, hexagon turret to provide positive lead., Advantages when using a self-opening die head, , Self-opening die heads are most commonly used in the, thread manufacturing process. They are made in a wide, range of sizes for producing threads up to about 100 mm, diameter., , The direction of workpiece rotation does not have to be, reversed., A roughing and finishing arrangement enables two cuts to, be made., , Copyright, @ NIMI, to: RT, beforRepublished, Production : Turner, (NSQF Not, Level-5), Ex No. 4.6.154 - 4.6.156, , 203
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An adjusting screw permits variations to be made from, the standard size, or enables several cuts to be made on, coarse threads., The cutting stresses maintain the die in the correct, position, preventing errors caused by die tilt or movement., , Thread rolling heads (Fig 4), Thread rolling is a modern method of producing threads, on turret lathes and automatic machines. They produce, threads with excellent grain flow, and the pitch, the form, and the accuracy of the threads are made to close, tolerances., , The two types of die heads in use are the radial die, heads and the tangential die heads., Radial die head (Fig 2), This die head uses radial cutting chasers. Adjustment, can be made to the thread cutting size and also for, roughing and finishing cuts to be made on the workpiece., , The dies (Fig 5), The markings on the die piece indicate the, , Tangential die head (Fig 3), , -, , die type, thread diameter, die number, thread relieved on the leading side, slots to locate the die in the die head., , These die heads use chasers of tangential type. These, chasers can be sharpened quite often. This gives them, a long life., , 204, , Copyright @ NIMI Not to be Republished, , Production : Turner (NSQF Level-5) : RT for Ex No. 4.6.154 - 4.6.156
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Accessories for capstan and turret lathe, Objectives: At the end of this lesson you shall be able to, • state the use of the knurling tool-holder, • state the use of the multiple-cutter holder, • state the use of the drill-holder, • state the use of the boring bar-holder, • state the use of the reamer-holder., Knurling tool-holder (Fig 1), , Multiple-cutter holder (Fig 4), , The knurling can also be performed by the tooling from, the turret head. The knurling tool-holder shown in Fig 1 is, mounted on the turret head. The position of the knurls, can be adjusted with the screw to accommodate different, diameters of the work. Different patterns of knurled surfaces, are obtained by tilting the knurls.(Figs 2 and 3), , The multiple-cutter holder accommodates more than one, tool. The one shown in Fig 4 enables turning of two different, diameters simultaneously. Turning and boring tools or, turning and facing tools can also be set in the holder, to perform multiple operations simultaneously., Drill holder (Fig 5), , The twist drills having morse taper shanks are usually, held in a socket which is parallel outside and tapered, inside. These sockets are inserted in the bracket of a, flange tool-holder and clamped to it by set screws. Straight, shank drills are mounted on Jacob's drill chuck, which in, turn is held by the flanged tool-holder and socket., Boring bar-holder (Fig 6), This holder is also called an extension holder or a flanged, tool-holder. These holders are intended for holding drills,, reamers, boring bars, etc., , Copyright, @ NIMI, to: RT, beforRepublished, Production : Turner, (NSQF Not, Level-5), Ex No. 4.6.154 - 4.6.156, , 205
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Reamer-holder, The standard practice of holding reamers in a capstan/, turret lathe is in some form of floating holder which permits, some amount of end movement of the reamer to align, itself with the work., , Fault analysis production turning, Objectives: At the end of this lesson you shall be able to, • list the common faults and state their causes and effects, • state the remedies for avoiding repetition of the faults., Common faults, Figure, , Cause, , Remedy, , Chatter (Fig 1), , Collet not gripping the bar, , Ensure collet tension is correct, , Lateral grooves and, ridges formed on the, workpiece giving a, moulted appearance., , The workpiece insecurely supported, , Hold the workpiece rigidly, , Play in the spindle bearings or tool Inform the supervisor, maintenance section, slideways, Spindle speed too high, Incorrect feed rate, Incorrect tool height, , Reduce the spindle speed, Adjust the feed rate suitably, Check the centre height of the tool and set, to correct height., , Incorrect tool geometry or a worn out Regrind the tool to the specification, tool bit., Play in the tool slideways, Incorrect or insufficient flow of cutting oil, , Inform the supervisor, , Change or adjust the flow of cutting oil, Overhang of the tool in the tool-holder too Set the tool back in the tool-holder with a, great, minimum overhang., Tool loose in the tool-holder, Clamp the tool rigidly, Play in the spindle bearings, Poor surface texture, (Fig.2), The cutting tool marks, widely spaced and / or torn, surface of the workpiece., , Incorrect tool geometry or worn out tool, bit, Insufficient coolant., Tool point too keen., Incorrect spindle speed, feed rate,, material or tool material., , 206, , Inform the supervisor, maintenance section., Regrind the tool bit to specification., Increase the coolant supply., Hone small radius on to the tool point unless, a sharp corner is specified., Check each against the specification and, adjust according to the requirement., , Copyright @ NIMI Not to be Republished, , Production : Turner (NSQF Level-5) : RT for Ex No. 4.6.154 - 4.6.156
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Figure, , Cause, , Eccentricity (Fig.3), , Breakage of tool (Fig 4), , Bar feed defective (Fig 5), , Dirty collect and collet sleeve, , Remove, clean and lubricate the collect sleeve., , Worn out collect., , Replace the collect., , Tool overhang too great., , Reset the tool with a minimum overhang., , Tool set below centre., , Reset the tool to the centre height., , The part-off too is too far from the collet., , Reset the tool as near as possible to the collet., , Incorrect spindle speed and feed rate., , Set the speeds and feed to those, recommended., , Loose or dirty collet., , Reset the collet tension and clean, if necessary., , Insufficient feed cord weight., , Increase the feed cord weight., , Jammed feed cord., , Examine the feed cord line and the pulleys., , Bell-mouthed hold (Fig.6) Chipped centering tool., , Pip leftout after parting, off (Fig 7), , Remedy, , Regrind or replace the centering tool., , The centering tool or the drill misaligned., , Reset the centering tool or drill centrally., , Worn out part-off tool, or incorrect tool, geometry., , Regrind the part-off tool to the specification., , Centre height of tool too high or too low., , Reset the centre height of the tool., , Copyright, @ NIMI, to: RT, beforRepublished, Production : Turner, (NSQF Not, Level-5), Ex No. 4.6.154 - 4.6.156, , 207
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Methods of producing internal threads on capstan / turret lathes, Objectives: At the end of this lesson you shall be able to, • state various methods of producing internal threads, • state construction details of a collapsible tap, • state the functional features of a collapsible tap., Internal threads are cut using 2 types of tools, – Single point thread cutting tool, – Solid tap, Internal threading by using a single point thread, cutting tool (Fig 1), , This precaution will prevent distortion of the thread., Excessive forward drive pressure will also distort the, thread., Forward motion of the tap should be stopped first before, it reaches the end of the hole being threaded. When using, the hexagon turret this distance is set with the turret stop., When the stop is reached by the advancing turret, the, automatic release operates, releasing the tap and allowing, it to revolve with the workpiece., Threading with a single point tool is usually carried out on, large workpieces or when special threads are required., , Reverse the headstock spindle rotation to drive the tap, back out of the threaded hole., , The tool may be mounted either on the hexagon turret or, on the square turret fitted to the cross-slide. A threading, drive accessory is fitted to the lathe, which enables the, tool to be fed along the work at the appropriate rate for, the desired pitch.Several cuts are normally made, each, slightly deeper than the previous cut, until the thread depth, appropriate to the selected pitch is obtained. The threading, tool is normally held in a bar mounted in a slide tool-holder., , Collapsible tap (Fig 3), , Solid taps, Solid taps are used for small diameter threads. They are, usually spiral fluted., The tap is fitted to the hexagon turret in a special tapholder. The holder is designed to release the tap, automatically at the end of the cut, permitting the tap to, rotate along with the workpiece. (Fig 2), The procedure for cutting the thread is as follows, Move the turret to the workpiece., Start the tap in the hole by exerting pressure on the turret, drive hand wheel., Keep slight forward pressure on the turret drive to prevent, the tap from pulling the turret along as the thread, cutting operation progresses., 208, , The collapsible tap is a mechanism in which thread cutting, chaser inserts, normally six in number, are positioned in, the slots provided in the head. These inserts are brought, to the cutting position by pulling the lever provided. At the, end of the threading operation, the tap collapses. The, tap may then be drawn directly out of the work without, reversing the rotation of the headstock spindle. This, reduces the production time. This facility is applicable, , Copyright @ NIMI Not to be Republished, , Production : Turner (NSQF Level-5) : RT for Ex No. 4.6.154 - 4.6.156
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only for cutting threads in holes of larger diameter due to, the presence of collapsible mechanism. For cutting, threads in successive pieces, the lever is again brought, to the engaging position so that the thread cutting inserts, are brought back from the collapsed or released state, to the cutting position., Threading attachment, To produce accurately pitched threads, when using a single, point thread cutting tool, the tool must be advanced into, the work at a rate determined by the thread pitch. The, technique for producing correct rate differs in the following, two set ups anyone of which may be provided in the, capstan or turret lathe., A thread lead attachment is used most commonly to, drive the turret of the capstan lathe and a thread chasing, attachment is used to drive the saddle of the turret lathe., Threading lead attachment (Fig 4), , This attachment is used on capstan lathes., A thread lead (lead screw) of the required pitch is fitted to, the turret drive. The turret is moved by the action of the, half nut engaging the lead screw. (Fig 4), The thread lead attachment includes a release mechanism, which is operated by the turret stops. The length of the, thread cut may be set automatically by adjusting the, position of the turret stops., Thread chasing attachment (Fig 5), This attachment is used on the turret lathes to drive the, saddle at the required rate for the threading operation., A threaded sleeve is fitted on the feed shaft and a meshing, threaded collar is fixed to the saddle. The collar draws, the saddle along the threaded sleeve., The pitch of the thread on the sleeve determines the pitch, of the thread cut on the workpiece., , Copyright, @ NIMI, to: RT, beforRepublished, Production : Turner, (NSQF Not, Level-5), Ex No. 4.6.154 - 4.6.156, , 209
