Engineering Design- A Systematic Approach Escrito Por Gerhard Pahl

Gerhard Pahl, em. Pro f. Dr. h.c. mult . Dr.-Ing. E.h. Dr.-Ing. Fachbe reich Maschine nbau Tcchnischc Univcrsitiit Da rmstadt Magdale ns trasse 4 64298 Darmstadt Germa ny

1" Wolfgang Beitz, Prof. Dr.-Ing.

)org Feldhusen, Prof. Dr.-lng. Institut für Allgeme ine

Karl-Heinrich Gro te, Prof. Dr.-Ing. [nstitut für Maschinenko nstruktio n Otto-von-Guer icke-Universitiit Magde burg Universitatsplatz 2 39106 Magdeburg Germa ny

Konstruktionslehre

d es Maschinenbaus Rhe inisch Westfalische Technische Hochschule Aachen Steinbachstrasse 548 52074 Aa che n Germa ny

E.h. Dr.-Ing.

1935-1998

British Library Cataloguing in Publication Data Engineering design :a systematic approach. - 3rd ed. l. Engineering de.sign l. Pahl, G. (Gerhard), 1925- 11. Wallace, Ken 620'.0042 ISBN- JO: 1846283 183 Library of Con greS> Control Number: 2006938893 ISBN 978- 1-84628-3 18·5 3rd cdition

e-ISBN 978-1-84628-319-2 3rd cdition

Printed o n acid-free paper

ISBN 3-540-19917-9 2nd edition

e Springer-Verlag London Limitcd 2007 Translation from theGerman Languageedition: Komtrukt ionslel~re by Gerhard Pahl et al. Copyright @Springer·Yerlag Berlín Heidelberg 2003. All rights reserved. 3rd English edition, Springer 2007 2nd English edition, Springer 1996 1st English edition publishcd by The Design Council, London, UK (ISBN 085072239X) Aparl from any f'air dealing for the purposcs of rescarch or private stud)'t 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 ofthe publishers,or in thecase of reprographlc reproducti.on in accordance with the terms of licenc.es is.sued by the Copyright Licensing Agency. Enquiries coatcerniatg reproductioo outsidc those tcnns should be sent to the publishers.

The use oí registered names, trademarh, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the re]evant la:ws and regulations and therefore free for general use. The ptablisher makes no representation, expres.s or implied, with regard to the accuracy of the information contained in this book and cannot accept an)' legal respon::;.ibility or liability for any errors or omis.sions that may be made. 987654321

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Contents

1

lntroduction .. ..... ... ... ... ... .. . . .. ... . • .. .. .. . . .. . . 1.1 The Engineering Designer ... . ....... ... . ... . ..... . . 1.1. 1 Tasks a nd Activities . ... ... ... . .. .... . . .... . . J. 1.2 Position of the Design Process within a Company . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.1.3 Trends . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . 6 1.2 Necessity fo r Systematic Desig n . . . . . . . . . . • . . . . • . . . . . 9 1.2.1 Requirements and the Need fo r Systematic Design . . . . . . . . . . . . . . . . . . . . . . . 9 1.2.2 Historical Background . . . . . . . . . . . . . . • . . . . . . . 10 1.2.3 Cu rren! Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 1.2.4 Aims and Objectives of this Book . . . . . . . • . . . . . 19

2

l'undame ntals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 Fundament.als ofTech nical Systems ... . . ..... .. ... . . . 2.1.1 Systems, Plant, Equipme nt, Machines, Assemblies and Componcnts . . . . . . . . . . . . . . . . . 2.1 .2 Conversion of Ene rgy. Materia l and Signals . . . . 2.1.3 Functional lnterrelationship . . . . . . . . . . . . . . . . . 2.1.4 Working Jnterrelatio nship . . . . . . . . . . . • . . . . . . . 2.1.5 Co nstructionalln terrelationship .. ... ... .... .. 2. 1.6 System lnterrelationship.. . . . . . . . . . . . . . . . . . . . 2. 1.7 Systematic Guideline . . . . . . . . . . . . . . . .. . . . . . . . 2.2 Fund amentals of the Systematic Approach . . ..... . . . . . 2.2.1 Problem Solving Process ... . ..... .. ..... . . . . . 2.2.2 Characteristics o f Good Problem Solvers. . . . . . . 2.2.3 Prob le m So lvi ng as In formatio n Processing . . . . 2.2.4 General Wo rking Mcthodo logy . . . . . . . . . . . . . . . 2.2.5 Generally App licable Methods . . . . . . . . • . . . . . . . 2.2.6 Role of Comp uter Support . . . . . . . . . . . . . . . . . . .

3

27 27 27 29 31 38 42 42 43 45 45 49 51 53 58 62

Product Planni.ng, Solut ion Fi.nding and Evaluation . . . . . . . . 63 3.1 Product Planning... . ..... . .... .. ..... .. .... . ...... 63 3. 1.1 Degree o f Novelty of a Product . . . . • . .. .. . . . . . 64

xviii

Contents

3.1.2 Product Life Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.3 Com pany Goals a nd Their Effec t . .. .... . ..... . 3. 1.4 Product Plan n ing . . . . . . . . . . . . . . . . . . . . . . . . • . . So lution Fi nd ing Methods . . . . . . . . . . . • . . . . . . • . . . . . . . 3.2.1 Convcntio nal Mcthod s . . . . . . . . . . . . . . . . . . . . . . 3.2.2 lntuitive Method s . . . . . . . . . . . . . . . . . . . • . . . . . . . 3.2.3 Discursive Methods . . . . . . . . . . . . . . . . . • . . . . . . . 3.2.4 Method s for Com bin ing So lutions .... . . ..... . Selection and Evaluation Methods . . .. _. . . .. _..•.. _ . . 3.3.1 Selecting Solu tion Variants .... . .... . . • . . ... . . 3.3.2 Evaluating So lution Variants . ... .... . . ... . . . .

64 65 66 77 78 82 89 103 106 106 109

4

Product Development Process .... .. ... .... ... ... ... ..• .. 4.1 General Problem So lving Process .. . .......... . ..... . 4.2 Flow o fWork Duri ng the Process ofDesig ning ... ... .. 4.2.1 Activity Plan ning . ... .. .... ... .. ..... .. .... . 4.2.2 Timing and Schedu ling .. .. . . .. .. .... .. ..... . 4.2.3 Plan ning Project and Produc t Costs ... .. ..... . 4.3 Effcctivc Organ isation Structures . .. ..... .. .... . . ... . 4.3.1 lnterd isciplinary Cooperation ... .. . . ......... 4.3.2 Leadersh ip and Team Behaviour . ... • . . .. . .. . .

125 125 128 128 134 136 138 138 141

5

Task Clarificat ion . .. _. . . .. .. . . .. .. . .. . .. • . . . .. . • . .. . .. . 5.1 lmportance o f Task Clarification . ... ... . . .... .. ... .. 5.2 Setting Up a Requirements List (Design Specification) .. . ..... . . .... • . ..... • . ... .. . 5.2.1 Contents .. .. .... .. ..... . . . . . . . . . ... . . .... .. 5.2.2 Format .... . .... . . ..... . ..... . . .... .. .... . . 5.2.3 lde ntifying the Requ ire ments ... .. ..... . ..... 5.2.4 Rcfin ing and Extcnding thc Rcquircmcnts . .. .. 5.2.5 Compiling the Requ irements List . .... .. .. . .. . 5.2.6 Examp les . .. .. _. . . ..... . ..... . . .... • . ... _.. 5.3 Using Requiremen ts Lists .. .. .......... • . ..... • ..... 5.3.1 Updating .. . .... . . ..... . ... ... • . . .. •.. .. _. . 5.3.2 Partial Req uirements Lists .. ..... .. .... • . .... 5.3.3 Further Uses .. .... .. .... ... ... ... ... . . .... . 5.4 Practica! Application of Requirements Lists . ... . • . .. ..

145 145

Conceptual Design .. . .. . ..... . .. .. . .. .. . .. . .. . . . . .. . .. . 6.1 Steps of Conceptual Design . .. . . .. .. . . .. ... ... ... ... 6.2 Abstracting to Identify the Essential Problems . ... ... . 6.2.1 Aim of Abstraction .. ..... . .... . . ..... . .. _ .. 6.2.2 Broaden ing the Problem For mulat ion . .. ..... . 6.2.3 Idcntifying the Esscn tial Problcms from the Requ irements List . .... .. ... . . . . . .. . 6.3 Establishing Fu nction Structures .. . .. . . • . ..... • .. . ..

159 159 161 161 162

3.2

3.3

6

146 146 147 149 151 152 153 153 153 156 157 157

164 169

CoJHeJHS

6.3.1 Overall Function 6.3.2 Breaking a Functio n Down into Subfu nctions .. 6.3.3 Practica! Applications of Function Structures .. Developing Working Structures .... . ..... . .......... 6.4.1 Scarcbing for Working Principies . ... .... .. ... 6.4.2 Combining Working Principies ............... 6.4.3 Selecting Working Str uctures . . . ...... . .... .. 6.4.4 Practica! Application ofWorking Structures .... Developing Concepts .... . . ... . . ............ . ..... . 6.5.1 Firming Up into Pri ncipie Solution Variants .... 6.5.2 Evaluating Principie Solution Variants . . ..... .. 6.5.3 Practica! Application of Developing Concepts .. Examples o f Co nceptual Design .... . ..... . ..... . .... 6.6.1 One-Handed Househ old Water Mixing Tap . . ... 6.6.2 Jmpu lse-Loading Test Rig . .. ... ... ... .... .. ..

169 170 178 181 181 184 186 186 190 190 192 198 199 199 210

Embodimcnt Dcsign ... .. ..... . ..... . ..... . . .... . • .... . 7.1 Steps o fEmbodiment Design ... . .... . . . .... . . .... .. 7.2 Checklist for Embod iment Dcsig n . . ..... .. ... . . . ... . 7.3 Basic Rules of Embodiment Design ... . .. . .. . • .. ... .. 7.3.1 Clarity ............. . ........ .. .. . . .. .. . ... 7.3.2 Simplicity . ... .... .. .... .. .... .. . .... .. ... .. 7.3.3 Safety ............................. • ....... 7.4 Princip ies of Embodiment Desig n . .... .. .... . . .... .. 7.4.1 Principies of Force Transm ission . .. .... . .... . 7.4.2 Principie of the Division ofTasks .. . ... .•.. .. . 7.4.3 Principie o f Self-Help ......... .. .... .. .... .. 7.4.4 Principies o f Stability and Bi-Stability . .. .... .. 7.4.5 Principies for Fault-Free Design ........ .... .. 7.5 Guidclincs for Embodimcnt Dcsig n . ... ... .... .. ... .. 7.5.1 General Considerations ........ . ..... . . . ..... 7.5.2 Design to Allow for Expansion ... .. ...... . ... 7.5.3 Design to Allow for Creep and Relaxation . ... .. 7.5.4 Design Against Corrosio n ..... . . .... . . ..... . 7.5.5 Design to Min imise Wear . . ..... • . .... . ..... . 7.5.6 Design for Ergonomics . ... .... . . .... . . .... .. 7.5.7 Design for Aesthetics .. ... . . . .... .. .... .. .... 7.5.8 Design for Productio n ....... ... .... . . .. .... 7.5.9 Dcsign for Assembly ... ... .... . . .... . . .... .. 7.5.10 Design for Maintenance .... .. . .. ... . .. . .. ... 7.5.11 Design for Recycling . ... .. ..... . . .... .. .... . 7.5.12 Design for Mínimum Risk . ..... • . ... . . ..... . 7.5.13 Design to Standards . ... . . .... • . . .... • .. ... .. 7.6 Evaluating Embodiment Desig ns ......... • .... . ..... 7.7 Example of Embodiment Design .. . . .. . • . . . . • .... . .. 7.8 Detail Design .. . ..... . .................... • .......

227 227 233 234 235 242 247 268 269 281 290 301 305 308 308 309 321 328 340 341 348 355 375 385 388 402 410 416 417 436

6.4

6.5

6.6

7

xix

xx

8

Contents

Mechanical Connections, Mechatronics and Adaptronics . . ..... ....... ..... ...... . .......... .. . 8.1 Mcchan ical Con ncctions .. .... .. .... ... .... .. .... .. 8.1.1 Ge neric Func tions and General Behavio ur ..... 8.1.2 Material Con ncctions .. .. ... .... ... ... .... .. 8.1.3 Form Connections . . .... . ...... • .... • ..... . . 8.1.4 Force Con nectio ns . . ..... . . .... • . .... .. .... . 8.1.5 Applicatio ns .. .... .. .... .. .... .. .... .. .... . 8.2 Mechatron ics . ..... . . .... . ..... . .. ... ... ... . . . . ... 8.2. 1 Ge neral Architecture a nd Termino logy ..... . .. 8.2.2 Go als and Limitations .... .. .... .. .... .. .... . 8.2.3 Development of Mechatronic Solutions . .... ... 8.2.4 Examp les .. . .. . ..... . ..... . ..... . .......... 8.3 Adaptronics . . .. . ..... . ................... • . .. .... 8.3.1 Fu ndame ntals a nd Termino logy .. .. ..•.. .. ... 8.3.2 Go als a nd Limitations . ... .. .... .. .... .. .... . 8.3.3 Development of Adap tron ic Solutions .... ... .. 8.3.4 Examples ........ . ..... . ..... . .. ... .... .. . .

439 439 440 440 441 443 447 448 448 450 450 451 458 458 459 460 461

Size Ranges and Modular Products ... ..... ...... . • ... .. .. 9.1 Size Ranges ..... . ..... . ........................... 9.1. 1 Similarity Laws .... ... ... ... ... ... ... ... ... . 9.1.2 Decimal-Geometric Preferred Number Series . . 9. 1.3 Representation and Selection of Step Sizes ... .. 9.1.4 Geometrically Simila r Size Ranges ... ... ... ... 9.1.5 Semi-Similar Size Ranges ........ . ... ..•.. ... 9. 1.6 Developm ent of Size Ranges ........ . . • .... . .. 9.2 Modular Products .... ... ... .... .. .... .. .... . . .... . 9.2.1 Modular Product Systematics ............. . .. 9.2.2 Modular Product Dcvclopmcnt .. ... .... ... . .. 9.2.3 Advantages and Limitations of Modular Systems 9.2.4 Examp les . .. .... .. .... .. ...... . ..... . .... .. 9.3 Recent Rationalisatio n Appro aches .. .... .. .... .. .... 9.3.1 Mod ularisation and Product Architecture . . .... 9.3.2 Platform Construction ... ... ... ... ... ... ... .

465 465 466 469 472 476 481 493 495 496 499 508 510 514 514 SI 5

l O Design for Quality .. ... ... ... ... ... .... . .... . .. ... . .. .. 10. 1 Applying a Systcmatic Approach . ... .... . . ... . . . .... 10.2 Faults and Disturbing Facto rs . . . .. ........ .. . .. . .... 10.3 Fault-Tree An alysis ... ... .... .. .... ... ... . ...... .. . 10.4 Failu re Mo de and Effect Analysis (FMEA) .... • .... . . . 10.5 Quality Function Deployment (QFD) ........ • .... . ..

517 517 521 522 529 531

9

11 Design for Mínimum Cost . ..... . . ... . . .. .. . • .. ... .. ..... 1 J. 1 Cost Factors . . ..... . ..... .. .... .. .... . ..... . • .... . 11.2 Fundamcntals o f Cost Calculations .. .... .. ... . • . ... . 11.3 Methods for Esti mati ng Costs .. . .. . .. . ..... . ........ 11.3.1 Comparing with Rclativc Costs ... ... ... .... .. 11.3.2 Estimating Using Share of Material Costs ...... 11.3.3 Estimating Using Regressio n Analysis . .. .... .. 11.3.4 Extrapolating Using Si milarity Relations . . ... . . 11.3.5 Cost Structures .. .. . . .. .. . . . .... .. .... .. .... 11.4 Target Costi ng . . . . . . . . . . . . . . . . • . . . . . . • . . . . • . . . . . . . 11.5 Rules for Minimising Costs . ... .. . ..... . . .... .. .... .

535 535 537 539 539 544 545 54 7

558 560 561

12 Summary ... .... ... ... ... ... ... ... . .. ... . . . .... .. .... . 563 12.1 The Systematic Approach . ............... • .. . . • ... . . 563 12.2 Exper ie nces of Applying the Systematic Approach in Practice . .... .. .... . . .... 567

References .... .. .... .. ..... . ..... . ..... . . .... . . .... . . .... . 571 English Bibliography . ..... . . ........... . ..... • ..... . ..... . 603 1ndex ..... . .. . .... ....... • .... . .... . . • ...... • .. . . • ....... 609

1

lntroduction

1.1 The Engineering Designer 1.1.1 Tasks and Activities The main task of engineers is to apply their scien tific and engineering knowledge to the so lution of technical problems, and then to optimise those solutions within the requircments and constraints set by material, tcchnological, economic, legal, e nvironmen tal and human-related consid erations. Problems become con crete tasks aftcr thc problems that cng inccrs havc to solvc to crcatc ncw tcchnical products (artefacts) are clari fied and defined . This happ ens in individual work as well as in teams in order to realise interdiscipli nary product d eve lopme nt. The mental creation o f a new product is the task o f d esign and development eng ineers, whereas its physical realisation is the responsibility o f production eogineers. In this book, designer is used synony mo usly to mean d esign and development engineers. Designers contribute to finding solu tions and developing products in a very specific way. They carry a heavy b urden of responsibility, since their id eas, k nowledge a nd skills determine the tech nical, economic a nd ecological properties of thc product in a dccisivc way. Desig n is an interesti ng engineeri ng activi ty that: • affects almost all a reas of hu ma n life • uses the laws and insights of science • b uilds u pon special experience • provid es the prerequisites for the physical realisation of solution i deas • requires professional integrity and responsibility. Dixon [1.39] and later Pen ny [l.l 44] placed thc work of engineering d csig ners al the centre of two intersecting cultural and tech nical streams (se e Fig ure l.l ). However, other models are also available. In psychological respec: ts, designing is a creative activity that calls for a sound g rounding in mathem atics, physics, chemistry, mechanics, thermodynamics, hydrodynam ics, electrical engineering, production eng ineering, materials techno logy, m achine elements and design theory, as well as knowledge and exp erience of the d omain o f interest. Initiative,

2

1 Jntroduction

Politks 1

Sociotogy. psychology 1

Ecanomi