DFM_Handbook

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DFM Hand book

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Product Design for Manufacture and Assembly
ISBN: 0-8247-0584-X This book is printed on acid-free paper. Headquarters Marcel Dekker, Inc. 270 Madison Avenue, New York, NY 10016 tel: 212-696-9000; fax: 212-685-4540 Eastern Hemisphere Distribution Marcel Dekker AG Hutgasse 4, Postfach 812, CH-4001 Basel, Switzerland tel: 41-61-261-8482; fax: 41-61-261-8896 World Wide Web http: //www.dekker. com The publisher offers discounts on this book when ordered in bulk quantities. For more information, write to Special Sales/Professional Marketing at the headquarters address above. Copyright © 2002 by Marcel Dekker, Inc. All Rights Reserved. Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming, and recording, or by any information storage and retrieval system, without permission in writing from the publisher. Current printing (last digit): 10 9 8 7 6 5 4 3 2 1 PRINTED IN THE UNITED STATES OF AMERICA
MANUFACTURING ENGINEERING AND MATERIALS PROCESSING A Series of Reference Books and Textbooks EDITOR loan Marinescu University of Toledo Toledo, Ohio FOUNDING EDITOR Geoffrey Boothroyd Boothroyd Dewhurst, I m Wakefield, RIi ode Island 1. Computers in Manufacturing, U. Rembold, M. Seth, and J. S. Weinstein 2. Cold Rolling of Steel, William L. Roberts 3. Strengthening of Ceramics: Treatments, Tests, and Design Applications, Harry P. Kirchner 4. Metal Forming: The Application of Limit Analysis, Betzalel Avitzur 5. Improving Productivity by Classification, Coding, and Data Base Standard- ization: The Key to Maximizing CAD/CAM and Group Technology, William F. Hyde 6. Automatic Assembly, Geoffrey Boothroyd, Corrado Poli, and Laurence E. Murch 7. Manufacturing Engineering Processes, Leo Alting 8. Modern Ceramic Engineering: Properties, Processing, and Use in Design, David W. Richerson 9. Interface Technology for Computer-Controlled Manufacturing Processes, Ulrich Rembold, Karl Armbruster, and Wolfgang Ulzmann 10. Hot Rolling of Steel, William L. Roberts 11. Adhesives in Manufacturing, edited by Gerald L. Schneberger 12. Understanding the Manufacturing Process: Key to Successful CAD/CAM Implementation, Joseph Harrington, Jr. 13. Industrial Materials Science and Engineering, edited by Lawrence E. Murr 14. Lubricants and Lubrication in Metalworking Operations, Elliot S. Nachtman and Serope Kalpakjian 15. Manufacturing Engineering: An Introduction to the Basic Functions, John P. Tanner 16. Computer-Integrated Manufacturing Technology and Systems, Ulrich Rembold, Christian Blume, and Ruediger Dillman 17. Connections in Electronic Assemblies, Anthony J. Bilotta 18. Automation for Press Feed Operations: Applications and Economics, Edward Walker 19. Nontraditional Manufacturing Processes, Gary F. Benedict 20. Programmable Controllers for Factory Automation, David G. Johnson 21. Printed Circuit Assembly Manufacturing, Fred W. Kear
22. Manufacturing High Technology Handbook, edited by Donatas Tuunelis and Keith E. McKee 23. Factory Information Systems: Design and Implementation for CIM Manage- ment and Control, John Gaylord 24. Flat Processing of Steel, William L. Roberts 26. Flexible Manufacturing Systems in Practice: Applications, Design, and Simulation, Joseph Talavage and Roger G. Hannam 27. Flexible Manufacturing Systems: Benefits for the Low Inventory Factory, John E. Lenz 28. Fundamentals of Machining and Machine Tools: Second Edition, Geoffrey Boothroyd and Winston A. Knight 29. Computer-Automated Process Planning for World-Class Manufacturing, James Nolen 30. Steel-Rolling Technology: Theory and Practice, Vladimir B. Ginzburg 31. Computer Integrated Electronics Manufacturing and Testing, Jack Arabian 32. In-Process Measurement and Control, Stephan D. Murphy 33. Assembly Line Design: Methodology and Applications, We-Min Chow 34. Robot Technology and Applications, edited by Ulrich Rembold 35. Mechanical Deburring and Surface Finishing Technology, Alfred F. Scheider 36. Manufacturing Engineering: An Introduction to the Basic Functions, Second Edition, Revised and Expanded, John P. Tanner 37. Assembly Automation and Product Design, Geoffrey Boothroyd 38. Hybrid Assemblies and Multichip Modules, Fred W. Kear 39. High-Quality Steel Rolling: Theory and Practice, Vladimir B. Ginzburg 40. Manufacturing Engineering Processes: Second Edition, Revised and Ex- panded, Leo Alting 41. Metalworking Fluids, edited by Jerry P. Byers 42. Coordinate Measuring Machines and Systems, edited by John A. Bosch 43. Arc Welding Automation, Howard B. Cary 44. Facilities Planning and Materials Handling: Methods and Requirements, Vbay S. Sheth 45. Continuous Flow Manufacturing: Quality in Design and Processes, Pierre C. Guerindon 46. Laser Materials Processing, edited by Leonard Migliore 47. Re-Engineering the Manufacturing System: Applying the Theory of Con- straints, Robert €. Stein 48. Handbook of Manufacturing Engineering, edited by Jack M. Walker 49. Metal Cutting Theory and Practice, David A. Stephenson and John S. Agapiou 50. Manufacturing Process Design and Optimization, Robert F. Rhyder 51. Statistical Process Control in Manufacturing Practice, Fred W. Kear 52. Measurement of Geometric Tolerances in Manufacturing, James D. Mea- dows 53. Machining of Ceramics and Composites, edited by Said Jahanmir, M. Rarnulu, and Philip Koshy 54. Introduction to Manufacturing Processes and Materials, Robert C. Creese 55. Computer-Aided Fixture Design, Yiming (Kevin) Rong and Yaoxiang (Stephens) Zhu 56. Understanding and Applying Machine Vision: Second Edition, Revised and Expanded, Nello Zuech 57. Flat Rolling Fundamentals, Vladimir B. Ginzburg and Robert Ballas
58. Product Design for Manufacture and Assembly: Second Edition, Revised and Expanded, Geoffrey Boothroyd, Peter Dewhurst, and Winston Knight Additional Volumes in Preparation
Preface to the Second Edition This second edition of Product Design for Manufacture and Assembly includes three new chapters, describing the processes of sand casting, investment casting, and hot forging. These chapters, combined with the chapters describing design for machining, injection molding, sheet metalworking, die casting, and powder metals, cover a wide range of the most basic forming processes used in industry. In addition, substantial material has been added to the introductory chapter illustrating the effects that the application of design for manufacture and assembly (DFMA) has had on U.S. industry as a whole. Chapter 2, dealing with the selection of materials and processes for manufacture, now includes further material describing material selection specifically and the economic ranking of processes using a new software tool. Chapter 3, dealing with product design for manual assembly, includes an updated special section dealing with the effect of design on product quality. Finally, additional material has been added to Chapter 15 discussing links between computer-aided design (CAD) solid models and design analysis tools. As with the previous edition, we thank the various companies who have supported research on DFMA at the University of Rhode Island and the graduate students who have contributed to the research. We particularly acknowledge the help of Allyn Mackay, on whose work the new chapter on investment casting is largely based. Finally, thanks are due to Shirley Boothroyd for typing much of the new material and to Kenneth Fournier for preparing some of the additional artwork. Geoffrey Boothroyd Peter Dewhurst Winston Knight \\\
Preface to the First Edition We have been working in the area of product design for manufacture and assembly (DFMA) for over twenty years. The methods that have been developed have found wide application in industry—particularly U.S. industry. In fact, it can be said that the availability of these methods has created a revolution in the product design business and has helped to break down the barriers between design and manufacture; it has also allowed the development of concurrent or simultaneous engineering. This book not only summarizes much of our work on DFMA, but also provides the details of DFMA methods for practicing and student engineers. Much of the methodology involves analytical tools that allow designers and manufacturing engineers to estimate the manufacturing and assembly costs of a proposed product before detailed design has taken place. Unlike other texts on the subject, which are generally descriptive, this text provides the basic equations and data that allow manufacturing and assembly cost estimates to be made. Thus, for a limited range of materials and processes the engineer or student can make cost estimates for real parts and assemblies and, therefore, become familiar with the details of the methods employed and the assumptions made. For practicing manufacturing engineers and designers, this book is not meant as a replacement for the DFMA software developed by Boothroyd Dewhurst, Inc., which contains more elaborate databases and algorithms, but rather provides a useful companion, allowing an understanding of the methods involved. For engineering students, this book is suitable as a text on product design for manufacture and assembly and, in fact, is partially based on notes for a two- course sequence developed by the authors at the University of Rhode Island.
vi Preface to the First Edition The original work on design for assembly was funded at the University of Massachusetts by the National Science Foundation. Professor K. G. Swift and Dr. A. H. Redford of the Universities of Hull and Salford, respectively, collaborated with G. Boothroyd in this early work and were supported by the British Science Research Council. The research continued at the University of Rhode Island and was supported mainly by U.S. industry. We thank the following companies for their past and, in some cases, continuing support of the work: Allied, AMP, Digital Equipment, DuPont, EDS, Ford, General Electric, General Motors, Gillette, IBM, Instron, Loctite, Motorola, Navistar, Westinghouse, and Xerox. We also thank all the graduate assistants and research scholars who over the years have contributed to the research, including: N. Abbatiello, A. Abbot, A. Anderson, J. Anderson, T. Andes, D. Archer, G. Bakker, T. Becker, C. Blum, T. Bassinger, K. P. Brindamour, R. C. Burlingame, T. Bushman, J. P. Cafone, A. Carnevale, M. Caulfield, H. Connelly, T. J. Consunji, C. Donovan, J. R. Donovan, W A. Dvorak, C. Elko, B. Ellison, M. C. Fairfield, J. Farris, T. J. Feenstra, M. B. Fein, R. P. Field, T. Fujita, A. Fumo, A. Girard, T. S. Hammer, P. Hardro, Y. S. Ho, L. Ho, L. S. Hu, G. D. Jackson, J. John II, B. Johnson, G. Johnson, K. Ketelsleger, G. Kobrak, D. Kuppurajan, A. Lee, C. C. Lennartz, H. C. Ma, D. Marlowe, S. Naviroj, N. S. Ong, C. A. Porter, P. Radovanovic, S. C. Ramamurthy, B. Rapoza, B. Raucent, M. Roe, L. Rosario, M. Schladenhauffen, B. Seth, C. Shea, T. Shinohara, J. Singh, R. Stanton, M. Stanziano, G. Stevens, A. Subramani, B. Sullivan, J. H. Timmins, E. Trolio, R. Turner, S. C. Yang, Z. Yoosufani, J. Young, J. C. Woschenko, D. Zenger, and Y. Zhang. We would also like to thank our colleagues, the late Professor C. Reynolds, who collaborated in the area of early cost estimating for manufactured parts, and Professor G. A. Russell, who collaborated in the area of printed circuit board assembly. Finally, thanks are due to Kenneth Fournier for preparing much of the artwork. Geoffrey Boothroyd Peter Dewhurst Winston Knight
Contents Preface to the Second Edition Hi Preface to the First Edition v 1. Introduction 1 1.1 What Is Design for Manufacture and Assembly? 1 1.2 How Does DFMA Work? 8 1.3 Reasons for Not Implementing DFMA 16 1.4 What Are the Advantages of Applying DFMA During Product Design? 21 1.5 Typical DFMA Case Studies 22 1.6 Overall Impact of DFMA on U.S. Industry 34 1.7 Conclusions 39 References 40 2. Selection of Materials and Processes 43 2.1 Introduction 43 2.2 General Requirements for Early Materials and Process Selection 45 2.3 Selection of Manufacturing Processes 46 2.4 Process Capabilities 48 2.5 Selection of Materials 55 2.6 Primary Process/Material Selection 65 2.7 Systematic Selection of Processes and Materials 71 References 83 vii
viii Contents 3. Product Design for Manual Assembly 85 3.1 Introduction 85 3.2 General Design Guidelines for Manual Assembly 86 3.3 Development of the Systematic DFA Methodology 93 3.4 Assembly Efficiency 93 3.5 Classification Systems 96 3.6 Effect of Part Symmetry on Handling Time 96 3.7 Effect of Part Thickness and Size on Handling Time 101 3.8 Effect of Weight on Handling Time 103 3.9 Parts Requiring Two Hands for Manipulation 104 3.10 Effects of Combinations of Factors 104 3.11 Effect of Symmetry for Parts that Severely Nest or Tangle and May Require Tweezers for Grasping and Manipulation 104 3.12 Effect of Chamfer Design on Insertion Operations 105 3.13 Estimation of Insertion Time 108 3.14 Avoiding Jams During Assembly 109 3.15 Reducing Disc-Assembly Problems 111 3.16 Effects of Obstructed Access and Restricted Vision on Insertion of Threaded Fasteners of Various Designs 112 3.17 Effects of Obstructed Access and Restricted Vision on Pop-Riveting Operations 115 3.18 Effects of Holding Down 115 3.19 Manual Assembly Database and Design Data Sheets 118 3.20 Application of the DFA Methodology 119 3.21 Further Design Guidelines 125 3.22 Large Assemblies 128 3.23 Types of Manual Assembly Methods 130 3.24 Effect of Assembly Layout on Acquisition Times 133 3.25 Assembly Quality 137 3.26 Applying Learning Curves to the DFA Times 141 References 143 4. Electrical Connections and Wire Harness Assembly 147 4.1 Introduction 147 4.2 Wire or Cable Harness Assembly 149 4.3 Types of Electrical Connections 152 4.4 Types of Wires and Cables 159 4.5 Preparation and Assembly Times 160 4.6 Analysis Method 182 References 190
Contents ix 5. Design for High-Speed Automatic Assembly and Robot Assembly 191 5.1 Introduction 191 5.2 Design of Parts for High-Speed Feeding and Orienting 192 5.3 Example 196 5.4 Additional Feeding Difficulties 199 5.5 High-Speed Automatic Insertion 199 5.6 Example 201 5.7 Analysis of an Assembly 202 5.8 General Rules for Product Design for Automation 203 5.9 Design of Parts for Feeding and Orienting 208 5.10 Summary of Design Rules for High-Speed Automatic Assembly 210 5.11 Product Design for Robot Assembly 211 References 217 6. Printed Circuit Board Design for Manufacture and Assembly 219 6.1 Introduction 219 6.2 Design Sequence for Printed Circuit Boards 220 6.3 Types of Printed Circuit Boards 220 6.4 Terminology 222 6.5 Assembly of Printed Circuit Boards 223 6.6 Estimation of PCB Assembly Costs 238 6.7 Case Studies in PCB Assembly 244 6.8 PCB Manufacturability 249 6.9 Design Considerations 252 6.10 Glossary of Terms 263 References 266 7. Design for Machining 267 7.1 Introduction 267 7.2 Machining Using Single-Point Cutting Tools 267 7.3 Machining Using Multipoint Tools 275 7.4 Machining Using Abrasive Wheels 284 7.5 Standardization 290 7.6 Choice of Work Material 291 7.7 Shape of Work Material 293 7.8 Machining Basic Component Shapes 294 7.9 Assembly of Components 307 7.10 Accuracy and Surface Finish 308 7.11 Summary of Design Guidelines 311 7.12 Cost Estimating for Machined Components 313 References 337
Contents 8. Design for Injection Molding 339 8.1 Introduction 339 8.2 Injection Molding Materials 340 8.3 The Molding Cycle 342 8.4 Injection Molding Systems 344 8.5 Injection Molds 346 8.6 Molding Machine Size 351 8.7 Molding Cycle Time 353 8.8 Mold Cost Estimation 359 8.9 Mold Cost Point System 367 8.10 Estimation of the Optimum Number of Cavities 369 8.11 Design Example 372 8.12 Insert Molding 374 8.13 Design Guidelines 375 8.14 Assembly Techniques 376 References 379 9. Design for Sheet Metalworking 381 9.1 Introduction 381 9.2 Dedicated Dies and Press-working 383 9.3 Press Selection 403 9.4 Turret Pressworking 409 9.5 Press Brake Operations 413 9.6 Design Rules 416 References 422 10. Design for Die Casting 423 10.1 Introduction 423 10.2 Die Casting Alloys 423 10.3 The Die Casting Cycle 425 10.4 Die Casting Machines 426 10.5 Die Casting Dies 429 10.6 Finishing 430 10.7 Auxiliary Equipment for Automation 432 10.8 Determination of the Optimum Number of Cavities 433 10.9 Determination of Appropriate Machine Size 439 10.10 Die Casting Cycle Time Estimation 443 10.11 Die Cost Estimation 453 10.12 Assembly Techniques 457 10.13 Design Principles 458 References 459
Contents xi 11. Design for Powder Metal Processing 461 11.1 Introduction 461 11.2 Main Stages in the Powder Metallurgy Process 463 11.3 Secondary Manufacturing Stages 464 11.4 Compaction Characteristics of Powders 468 11.5 Tooling for Powder Compaction 475 11.6 Presses for Powder Compaction 478 11.7 Form of Powder Metal Parts 481 11.8 Sintering Equipment Characteristics 484 11.9 Materials for Powder Metal Processing 489 11.10 Contributions to Basic Powder Metallurgy Manufacturing Costs 492 11.11 Modifications for Infiltrated Materials 511 11.12 Impregnation, Heat Treatment, Tumbling, Steam Treatment, and Other Surface Treatments 512 11.13 Some Design Guidelines for Powder Metal Parts 514 References 515 12. Design for Sand Casting 517 12.1 Introduction 517 12.2 Sand Casting Alloys 519 12.3 Basic Characteristics and Mold Preparation 519 12.4 Sand Cores 524 12.5 Melting and Pouring of Metal 525 12.6 Cleaning of Castings 526 12.7 Cost Estimating 527 12.8 Design Rules for Sand Castings 537 12.9 Example Calculations 542 References 546 13. Design for Investment Casting 549 13.1 Introduction 549 13.2 Process Overview 549 13.3 Pattern Materials 552 13.4 Pattern Injection Machines 552 13.5 Pattern Molds 554 13.6 Pattern and Cluster Assembly 554 13.7 The Ceramic Shell-Mold 555 13.8 Ceramic Cores 556 13.9 Pattern Meltout 556 13.10 Pattern Burnout and Mold Firing 557 13.11 Knockout and Cleaning 557
xii Contents 13.12 Cutoff and Finishing 557 13.13 Pattern and Core Material Cost 557 13.14 Wax Pattern Injection Cost 561 13.15 Fill Time 562 13.16 Cooling Time 562 13.17 Ejection and Reset Time 564 13.18 Process Cost per Pattern or Core 566 13.19 Estimating Core Injection Cost 567 13.20 Pattern and Core Mold Cost 567 13.21 Core Mold Cost 572 13.22 Pattern and Cluster Assembly Cost 572 13.23 Number of Parts per Cluster 574 13.24 Pattern Piece Cost 575 13.25 Cleaning and Etching 576 13.26 Shell Mold Material Cost 576 13.27 Investing the Pattern Cluster 577 13.28 Pattern Meltout 578 13.29 Burnout, Sinter, and Preheat 578 13.30 Total Shell Mold Cost 579 13.31 Cost to Melt Metal 579 13.32 Raw Base Metal Cost 583 13.33 Ready-to-Pour Liquid Metal Cost 584 13.34 Pouring Cost 584 13.35 Final Material Cost 584 13.36 Breakout 586 13.37 Cleaning 587 13.38 Cutoff 587 13.39 Design Guidelines 590 References 591 14. Design for Hot Forging 593 14.1 Introduction 593 14.2 Characteristics of the Forging Process 593 14.3 The Role of Flash in Forging 595 14.4 Forging Allowances 600 14.5 Preforming During Forging 603 14.6 Flash Removal 609 14.7 Classification of Forgings 610 14.8 Forging Equipment 613 14.9 Classification of Materials 622 14.10 Forging Costs 622 14.11 Forging Die Costs 631
Contents xiii 14.12 Die Life and Tool Replacement Costs 636 14.13 Costs of Flash Removal 637 14.14 Other Forging Costs 640 References 641 15. Design for Manufacture and Computer-Aided Design 643 15.1 Introduction 643 15.2 General Considerations for Linking CAD and DFMA Analysis 643 15.3 Geometric Representation Schemes in CAD Systems 645 15.4 Design Process in a Linked CAD/DFMA Environment 660 15.5 Extraction of DFMA Data from CAD System Database 663 15.6 Expert Design and Cost Estimating Procedures 665 References 668 Nomenclature 669 Index 683