Theory and design of CNC systems

Springer Series in Advanced Manufacturing

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Professor D.T. Pham

Manufacturing Engineering Centre

Cardiff University

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ANEMONA

V. Botti and A. Giret

Suk-Hwan Suh • Seong-Kyoon Kang

Dae-Hyuk Chung • Ian Stroud

Theory and Design

of CNC Systems

123

Suk-Hwan Suh, PhD

School of Mechanical & Industrial

Engineering

POSTECH, San 31, Pohang, 790-784

Republic of Korea

Seong-Kyoon Kang, PhD

K&S International Patent and Law Firm

3F, Hanjin Bldg., 607-12 Yeoksam-dong,

Kangnam-gu, Seoul, 135-907

Republic of Korea

Dae-Hyuk Chung, PhD

Doosan Infracore Co., Ltd.

601-3, Namsan-dong, Changwon-Si,

Gyeongnam-Do

Republic of Korea

Ian Stroud, PhD

École Polytechnique Fédérale

de Lausanne (EPFL)

STI-IGM-LICP, Station 9,

1015 Lausanne

Switzerland

ISBN 978-1-84800-335-4 e-ISBN 978-1-84800-336-1

DOI 10.1007/978-1-84800-336-1

Springer Series in Advanced Manufacturing ISSN 1860-5168

British Library Cataloguing in Publication Data

Theory and design of CNC systems. - (Springer series in

advanced manufacturing)

1. Machine-tools - Numerical control 2. Machine-tools -

Numerical control - Programming

I. Suh, Suk-Hwan

621.9'023'0285

ISBN-13: 9781848003354

Library of Congress Control Number: 2008928587

© 2008 Springer-Verlag London Limited

Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted

under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or

transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case

of reprographic reproduction in accordance with the terms of licences issued by the Copyright Licensing

Agency. Enquiries concerning reproduction outside those terms should be sent to the publishers.

The use of registered names, trademarks, etc. in this publication does not imply, even in the absence of a

specific statement, that such names are exempt from the relevant laws and regulations and therefore free for

general use.

The publisher makes no representation, express or implied, with regard to the accuracy of the information

contained in this book and cannot accept any legal responsibility or liability for any errors or omissions that

may be made.

Cover design: eStudio Calamar S.L., Girona, Spain

Printed on acid-free paper

9 8 7 6 5 4 3 2 1

springer.com

This book is dedicated to:

Eun-Sook Choi,

Hyeon-Jeong Lee,

Hye-Jung Kim,

and Hildegarde Nagy-Stroud

and to the rest of our families

for their endurance of this headlong task.

Preface

CNC controllers, working as a brain for manufacturing automation, are high value￾added products accounting for over 30% of the price of machine tools. CNC technol￾ogy is generally considered as a measure of the level of manufacturing technology of

a nation, and is currently led by major advanced countries such as USA, Japan, and

Germany. CNC technology, which cannot be developed with one single technology

but needs to integrate computer technology, hardware technology, machining tech￾nology, and so on, is often referred to as “The Flower of Industrial Technology”, and

requires a strategic long-term support, mostly on a governmental level.

Despite its significant role, textbooks on CNC controllers are quite rare world￾wide, with a few published in the 1970s and some later. However, the earlier ones

mostly deal with conventional technologies, while the later ones deal with fragmental

contents, mostly focusing on part programming and machine operation. This book

is written by several authors in collaboration who have long experience in CNC de￾velopment, education, and research, and is designed as a highly focused textbook

to provide knowledge on the principles and development technologies of CNC con￾trollers. Therefore, this book can be used as a main textbook for courses related to

CNC in such departments as mechanical engineering, precision engineering and con￾trol engineering, and as a guide for those working on CNC development in industry.

If highly descriptive portions are taken out, it can also be used as lecture material in

technical colleges.

The framework of industrial CNC controllers has been established by integrat￾ing the structure and element technologies of CNC controllers under research and

development by the authors in their respective field of industry and academia over

the years. Furthermore, this book intends to encourage the spirit of development by

introducing actual realization cases.

This book is composed of two parts with a total of 11 chapters: Part I is composed

of Chapters 1–6 on the principle and design of CNC, and Part II is composed of an

open-architectural soft CNC system. Specifically, Chapter 1 provides general con￾cepts and mechanisms of numerically controlled machines, while Chapters 2 through

5 cover the element technologies of NCK in charge of controlling the transfer axis,

including interpreter, interpolator, control of acceleration and deceleration, and po￾vii

viii Preface

sition control system. In Chapter 6, NCK development cases are described together

with source code. Therefore, those who are interested in motion controllers can de￾velop independent control devices by referring to the contents of Chapters 2 through

6.

Part II describes the open-architectural soft CNC system, including the principles

of major modules of numerically controlled machines, except the NCK (dealt with in

Part 1), and the system design process for the composition of the overall system from

the perspective of open-architectural soft CNC systems. Specifically, Chapter 7 ex￾plains the PLC, controlling most mechanical motions except the transfer axis, while

Chapter 8 presents the principles of the Man-Machine Interface (MMI) and the ma￾jor modules for the development of conversational programming methods. Real-time

operation concepts and methods necessary for designing real-time controllers are de￾scribed in Chapter 9, Chapter 10 describes the architecture design of CNC systems

based on personal computers. This is discussed from the perspective of soft CNC,

including several approaches to the architecture of open-style CNC system with free

external interfaces, and the design process of those approaches. The concept and pri￾mary elements of STEP-NC are introduced in Chapter 11, which has recently come

under the spotlight as a method of realizing intelligent CNC machines. Therefore,

those who are interested in designing and realizing open-style soft CNC devices can

refer to the topics covered in Chapters 7 through 11 to materialize intelligent open￾style NC devices.

As authors of this book, we recommend that instructors have their students ac￾tually code the NCK technologies (Chapters 2 through 5), which are the core ele￾ments, and finish a computer simulation system, one similar to the development case

covered in Chapter 6, and verify the performance. One step further, if the interface

board (encoder signal and PLC signal processing) and the XY-table can actually be

connected by the students, the effect of learning can be doubled.

Those students who want to learn the general technologies related with CNC sys￾tems can achieve their goals by studying the PLC, conversational programming sys￾tem, particularly actual cases of system programming methods to realize soft CNC,

as covered in Part 2, Chapters 7 through 11.

To complete this book it took over three years to collect and organize all sorts of

material accumulated over a period of many years, including technical papers and

patent data materials. However, we feel there are many shortcomings. Some of the

excuses we can offer could include the fact that CNC technology has been developed

by industry itself and that each element technology derives from a completely dif￾ferent domain of knowledge. Therefore, for integrating them under the umbrella of

CNC for academic purposes, many problems are posed such as un- or mis-defined

technical terminologies and lack of systematic knowledge bases. However, despite

this, the authors decided to publish this book in the hope that it will contribute to the

advancement of CNC technology both at home and abroad, in consideration of the

sheer reality that no proper textbooks are available for education or training in CNC

technology. With lots of input from the readers, we hope this book can improve its

contents in the future.

Preface ix

This book was originally published in Korean and has now been translated into

English. We would like to take this opportunity to express our appreciation to Ms.

Eunsook Choi, who encouraged preparation of the English version of the original

Korean text book, Mr. Suho Jung and students of the Center for ubiquitous manu￾facturing at POSTECH for help in the editing, and Springer who willingly accepted

publication of it.

We would also like to express our appreciation to Dae-Jung Seong of Doosan

Infracore in charge of CNC development for providing contemporary industrial per￾spectives.

Postech, Suk-Hwan Suh, Seong-Kyoon Kang,

March 2008 Dae-Hyuk Chung, Ian Stroud

Contents

Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii

Part I Principles and NCK Design of CNC Systems

1 Introduction to NC Systems ..................................... 3

1.1 Introduction . . ............................................. 3

1.2 The History of NC and NC Machine Tools . . . . . . . . . . . . . . . . . . . . . 6

1.3 CNC Driving System Components . . . ......................... 8

1.3.1 Driving Motor and Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.3.2 Linear Movement Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

1.3.3 Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

1.4 CNC Control Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

1.4.1 Semi-closed Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

1.4.2 Closed Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

1.4.3 Hybrid Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

1.4.4 Open Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

1.5 The Components of the CNC system . . . . . . . . . . . . . . . . . . . . . . . . . . 19

1.5.1 MMI Function. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

1.5.2 NCK Function. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

1.5.3 PLC Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

1.5.4 Real-time Control System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

1.6 The Progress Direction of the CNC System . . . . . . . . . . . . . . . . . . . . . 29

1.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

2 Interpreter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

2.2 Part Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

2.2.1 Program Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

2.2.2 Main Programs and Subprograms. . . . . . . . . . . . . . . . . . . . . . . 39

2.3 Main CNC System Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

2.3.1 Coordinate Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

xi

xii Contents

2.3.2 Interpolation Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

2.3.3 Feed Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

2.3.4 Tools and Tool Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

2.3.5 Spindle Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

2.3.6 Fixed-cycle Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

2.3.7 Skip Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

2.3.8 Program Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

2.3.9 Advanced Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

2.4 G&M-code Interpreter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

2.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

3 Interpolator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

3.2 Hardware Interpolator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

3.2.1 Hardware Interpolation DDA . . . . . . . . . . . . . . . . . . . . . . . . . . 71

3.2.2 DDA Interpolation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

3.3 Software Interpolator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

3.3.1 Software Interpolation Methods . . . . . . . . . . . . . . . . . . . . . . . . 78

3.3.2 Sampled-Data Interpolation . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

3.4 Fine Interpolation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

3.5 NURBS Interpolation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

3.5.1 NURBS Equation Form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

3.5.2 NURBS Geometric Characteristics . . . . . . . . . . . . . . . . . . . . . 100

3.5.3 NURBS Interpolation Algorithm . . . . . . . . . . . . . . . . . . . . . . . 101

3.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

4 Acceleration and Deceleration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

4.2 Acc/Dec Control After Interpolation . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

4.2.1 Acc/Dec Control by Digital Filter . . . . . . . . . . . . . . . . . . . . . . 109

4.2.2 Acc/Dec Control by Digital Circuit . . . . . . . . . . . . . . . . . . . . . 112

4.2.3 Acc/Dec Control Machining Errors . . . . . . . . . . . . . . . . . . . . . 121

4.2.4 Block Overlap in ADCAI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126

4.3 Acc/Dec Control Before Interpolation . . . . . . . . . . . . . . . . . . . . . . . . . 128

4.3.1 Speed-profile Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

4.3.2 Block Overlap Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

4.3.3 Corner Speed of Two Blocks Connected by an Acute Angle 142

4.3.4 Corner Speed Considering Speed Difference of Each Axis . . 144

4.4 Look Ahead . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

4.4.1 Look-Ahead Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147

4.4.2 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152

4.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155

Contents xiii

5 PID Control System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

5.2 The Servo Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158

5.3 Servo Control for Positioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160

5.4 Position Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161

5.4.1 PID Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162

5.4.2 PID Gain Tuning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166

5.4.3 Feedforward Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171

5.5 Analysis of the Following Error. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179

5.5.1 The Following Error of the Feedback Controller . . . . . . . . . . 179

5.5.2 The Following Error of the Feedforward Controller . . . . . . . . 182

5.5.3 Comparison of Following Errors . . . . . . . . . . . . . . . . . . . . . . . 183

5.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

6 Numerical Control Kernel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187

6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187

6.2 Architecture of ACDAI-type NCK . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187

6.2.1 Implementation of the Interpolator . . . . . . . . . . . . . . . . . . . . . . 188

6.2.2 Implementation of the Rough Interpolator. . . . . . . . . . . . . . . . 193

6.2.3 Implementation of an Acc/Dec Controller . . . . . . . . . . . . . . . . 199

6.2.4 Implementation of Fine Interpolator. . . . . . . . . . . . . . . . . . . . . 203

6.2.5 Implementation of the Position Controller. . . . . . . . . . . . . . . . 208

6.3 Architecture of an ADCBI-type NCK . . . . . . . . . . . . . . . . . . . . . . . . . . 211

6.3.1 Implementation of the Look-Ahead Module . . . . . . . . . . . . . . 213

6.3.2 Implementation of an Acc/Dec Controller . . . . . . . . . . . . . . . . 215

6.3.3 Implementation of the Rough Interpolator. . . . . . . . . . . . . . . . 222

6.3.4 The Mapping Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225

6.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226

Part II Open-architectural Soft CNC Systems

7 Programmable Logic Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229

7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229

7.2 PLC Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230

7.3 PLC Programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234

7.4 Machine Tool PLC Programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235

7.5 PLC System Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240

7.5.1 Software Model and Communication Model. . . . . . . . . . . . . . 242

7.5.2 Programming Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244

7.5.3 User Programming Languages . . . . . . . . . . . . . . . . . . . . . . . . . 245

7.6 Soft PLC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247

7.7 PLC Configuration Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248

7.7.1 PLC System Functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249

7.7.2 Executor Programming Sequence . . . . . . . . . . . . . . . . . . . . . . . 253

7.7.3 Executor Implementation Example . . . . . . . . . . . . . . . . . . . . . 254

xiv Contents

7.8 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268

8 Man–Machine Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271

8.1 MMI Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271

8.1.1 Area for Status Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271

8.1.2 Area for Data Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273

8.1.3 Area for MPG Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273

8.1.4 Area for Machine Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 273

8.2 Structure of the MMI System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275

8.3 CNC Programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278

8.3.1 The Sequence of Part Programming . . . . . . . . . . . . . . . . . . . . . 278

8.3.2 Manual Part Programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279

8.3.3 Automatic Part Programming . . . . . . . . . . . . . . . . . . . . . . . . . . 280

8.4 Mazatrol Conversational System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289

8.4.1 Turning Conversational System . . . . . . . . . . . . . . . . . . . . . . . . 289

8.4.2 Programming Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292

8.5 Conversational Programming System Design . . . . . . . . . . . . . . . . . . . 294

8.5.1 Main Sequence for Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294

8.5.2 Key Design Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296

8.6 Development of the Machining Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . 305

8.6.1 Turning Fixed Cycle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305

8.6.2 Turning Cycle for Arbitrary Shape . . . . . . . . . . . . . . . . . . . . . . 306

8.6.3 Corner Machining Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310

8.6.4 Drilling Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312

8.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 314

9 CNC Architecture Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315

9.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315

9.2 Operating Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317

9.3 Real-time Programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319

9.4 Structure of a Real-time OS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321

9.5 Process Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323

9.5.1 Process Creation and Termination . . . . . . . . . . . . . . . . . . . . . . 324

9.5.2 Process State Transition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324

9.5.3 Process Scheduling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325

9.6 Process Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330

9.6.1 Semaphores . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330

9.6.2 Using Semaphores . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331

9.6.3 Events and Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331

9.7 Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334

9.7.1 System Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334

9.7.2 Mutual Exclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335

9.7.3 Deadlock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336

9.8 Inter-process Communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337

9.8.1 Shared Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337

Contents xv

9.8.2 Message System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338

9.9 Key Performance Indices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340

9.9.1 Task Switching Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340

9.9.2 Context Switching Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341

9.9.3 Semaphore Shuffling Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341

9.9.4 Task Dispatch Latency Time . . . . . . . . . . . . . . . . . . . . . . . . . . . 341

9.10 Hardware and Operating Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344

9.10.1 Architecture of Multi-processing Hardware . . . . . . . . . . . . . . 344

9.10.2 Operating System Configuration. . . . . . . . . . . . . . . . . . . . . . . . 347

9.10.3 CNC System Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348

9.11 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 350

10 Design of PC-NC and Open CNC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353

10.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353

10.2 Design of Software Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356

10.2.1 CNC System Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356

10.3 Design of Soft-NC System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359

10.3.1 Design of Task Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359

10.3.2 Design of the System Kernel . . . . . . . . . . . . . . . . . . . . . . . . . . . 361

10.3.3 PLC Program Scanning and Scheduling . . . . . . . . . . . . . . . . . 362

10.3.4 Task Synchronization Mechanism . . . . . . . . . . . . . . . . . . . . . . 365

10.3.5 Inter-Task Communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369

10.4 Motion Control System Programming Example . . . . . . . . . . . . . . . . . 376

10.4.1 Design of System Architecture . . . . . . . . . . . . . . . . . . . . . . . . . 377

10.4.2 Creating Tasks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378

10.4.3 Task Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378

10.4.4 Task Priority . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 381

10.4.5 Inter-Task Communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . 381

10.4.6 Create Event Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 384

10.5 Open-CNC Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 387

10.5.1 Closed-type CNC Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . 387

10.5.2 Open CNC Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389

10.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393

11 STEP-NC System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395

11.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395

11.2 Background of STEP-NC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397

11.2.1 Problems with G&M Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . 397

11.2.2 Historical Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 398

11.3 STEP-NC: A New CNC Interface Based on STEP . . . . . . . . . . . . . . . 399

11.3.1 Contents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 399

11.3.3 Objectives and Impacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 401

11.4 STEP-NC Data Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402

11.4.1 Part 1: Overview and Fundamental Principles. . . . . . . . . . . . . 403

11.3.2 Relationship Between STEP and STEP-NC . . . . . . . . . . . . . . . 399

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11.4.2 Part 10: General Process Data . . . . . . . . . . . . . . . . . . . . . . . . . . 405

11.4.3 Part 11: Process Data for Milling . . . . . . . . . . . . . . . . . . . . . . . 407

11.4.4 Part 12: Process Data for Turning . . . . . . . . . . . . . . . . . . . . . . . 407

11.4.5 Tools for Milling and Turning . . . . . . . . . . . . . . . . . . . . . . . . . . 408

11.5 Part Programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 410

11.5.1 Part Programming for the Milling Operation . . . . . . . . . . . . . 411

11.5.2 Part Programming for the Turning Operation . . . . . . . . . . . . . 414

11.6 STEP-CNC System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415

11.6.1 Types of STEP-CNC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 417

11.6.2 Intelligent STEP-CNC Systems . . . . . . . . . . . . . . . . . . . . . . . . 418

11.7 Worldwide Research and Development . . . . . . . . . . . . . . . . . . . . . . . . 422

11.7.1 WZL-Aachen University (Germany) . . . . . . . . . . . . . . . . . . . . 422

11.7.2 ISW-University of Stuttgart (Germany) . . . . . . . . . . . . . . . . . . 424

11.7.3 POSTECH (South Korea) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425

11.7.4 Ecole Polytechnic F´ed´erale of Lausanne (Switzerland) . . . . . 426

11.7.5 University of Bath (UK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427

11.7.6 NIST (USA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427

11.8 Future Prospects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428

A Turning and Milling G-code System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 431

A.1 Turning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 431

A.2 Milling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 434

A.3 Classification of G-code Groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437

Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 439

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 447