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A Short Course in

Industrial Design

Eskild Tjalve

Senior Lecturer, Department of Engineering

Design, The Technical University o f Denmark

NEWNES- B U T T E R W O R T H S

L O N D O N - B O S T O N

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UNITED KINGDOM A U S T R A L I A C A N A D A NEW Z E A L A N D SOUTH AFRICA USA

THE BUTTERWORTH GROUP Butterworth & Co (Publishers) Ltd London; 88 Kingsway, WC2B 6AB Butterworths Pty Ltd

Sydney: 586 Pacific Highway, Chatswood, NSW 2067 Also at Melbourne, Brisbane, Adelaide and Perth Butterworth & Co (Canada) Ltd

Scarborough: 2265 Midland Avenue, Scarborough, Ontario, MIP 4SI Butterworths of New Zealand Ltd

Wellington: Τ & W Young Building,

7 7 - 8 5 Customhouse Quay 1, CPO Box 472 Butterworth & Co (South Africa) (Pty) Ltd Durban: 1 5 2 - 1 5 4 Gale Street

Butterworths (Publishers) Inc

Boston: 10 Tower Office Park, Woburn, Mass. 01801

First published in Denmark in 1976 as 'Systematisk udformning af industriprodukter'

First published in English 1979 © E. Tjalve, 1979

All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, including photocopying and recording, without the written permission of the copyright holder, application for which should be addressed to the publisher. Such written permission must also be obtained before any part of this publication is stored in a retrieval system of any nature. This book is sold subject to the Standard Conditions of Sale of Net Books and may not be re-sold in the UK below the net price given by the Publishers in their current price list.

B r i t i s h L i b r a r y C a t a l o g u i n g in P u b l i c a t i o n D a t a

Tjalve, Eskild

A short course in industrial design. 1. Engineering design

I. Title

620'.0042 TA174 78-41280 ISBN 0-408-00388-X

Typeset by Butterworths Litho Preparation Department Printed in Scotland by Thomson Litho Ltd., East Kilbride

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Preface

T h e c r e a t i o n o f a n e w p r o d u c t takes in m a n y levels o f a c t i v i t y a n d m a n y skills, o f w h i c h t h e f i r s t a n d f o r e m o s t are those o f design engineers a n d i n d u s t r i a l designers. It is easy t o recognise t h e e x t r e m e s w h e n c o m p a r i n g t h e responsibilities o f t h e design engineer a n d t h e i n d u s t r i a l designer, b u t n o t so easy t o say w h e r e t h e r e s p o n s i b i l i t y o f one ends a n d t h e o t h e r begins.

T h e design engineer is i n v o l v e d in design w h i c h is o f t e n k n o w n b y o t h e r names, e.g. s k e t c h i n g , detail design, d i m e n s i o n i n g , etc. A c o n s i d e r a b l e p a r t o f t h e w o r k o f design engineers a n d i n d u s t r i a l designers consists o f t h e same a c t i v i t i e s , i.e. f o r m u l a t i o n o f suggestions o f shape, ' m o d e l l i n g ' o f these ( s k e t c h i n g , d r a w i n g or h a r d w a r e m o d e l l i n g ) , investigating and appraising t h e various possibilities. These activities i n v o l v e t h e creative m i n d at m a n y levels and are t h e subject o f t h i s b o o k , w h i c h n o t o n l y i n t r o d u c e s t h e s t u d e n t t o t h e p r i n c i p l e s o f e v o l v i n g a design, b u t surveys t h e c r i t e r i a b y w h i c h these are assessed. T h r o u g h o u t this b o o k t h e w o r d 'designer' has been used as a b l a n k e t t e r m f o r people w o r k i n g w i t h design (i.e. engineers, designers and others) o f p r o d u c t s .

T h e c o n t e n t s o f t h i s b o o k s h o u l d be seen as p a r t o f t h e design t e c h n i q u e . In t h e overall p l a n f o r p r o j e c t e v a l u a t i o n a n d design o n l y t h e m e t h o d s c o n n e c t e d w i t h t h e f i n a l phases o f design p r o j e c t have been d e s c r i b e d .

T h e danger o f f o r m u l a t i n g s y s t e m a t i c m e t h o d s in c o n n e c t i o n w i t h c o n s t r u c t i o n w o r k , is t h a t o t h e r s are led i n t o t h i n k i n g t h a t a s y s t e m a t i c a p p r o a c h necessarily gives t h e r i g h t answer. T h i s is just n o t so. T h e m o s t e f f e c t i v e s o l u t i o n is achieved b y t h e r i g h t balance o f systematics a n d i n t u i t i o n . T h e s y s t e m a t i c a p p r o a c h s h o u l d t h e r e f o r e be seen as t h e f o u n d a t i o n f o r t h e a p p r o p r i a t e a t t i t u d e t o i n n o v a t i o n , n a m e l y an under­ s t a n d i n g o f t h e f a c t t h a t one c a n , t h r o u g h a c o n s c i o u s e f f o r t l o o k o b j e c t i v e l y a n d s y s t e m a t i c a l l y at all t h e design c r i t e r i a a n d premises o n w h i c h a n y p a r t i c u l a r s o l u t i o n is based.

E x i s t i n g p r o d u c t s have t o a great e x t e n t been used as e x a m p l e s . These are i n c l u d e d p a r t i c u l a r l y w h e r e t h e y illustrate d i f f e r e n t approaches t o t h e same p r o b l e m a n d d i f f e r e n t results — a n d n o t because t h e y are p a r t i c u l a r l y g o o d o r b a d . T h e r e is t h u s n o i m p l i e d e v a l u a t i o n in t h e i r p r e s e n t a t i o n .

I w o u l d like t o t h a n k those c o m p a n i e s w h i c h have c o n t r i b u t e d t o t h e e x a m p l e s b y s u b m i t t i n g m a t e r i a l o f various k i n d s . T h e p h o t o g r a p h s w h i c h are n o t a c k n o w l e d g e d w e r e t a k e n o n m y b e h a l f b y F r a n k S c h m i d t , t o w h o m I a m very g r a t e f u l .

It is m y h o p e t h a t m a n y o f those w h o are i n v o l v e d in t h e e v o l u t i o n o f p r o d u c t s w i l l f i n d this b o o k useful w h e t h e r t h e y are engineers o r designers. I also h o p e t h a t t h e b o o k w i l l f i l l a gap in t h e l i t e r a t u r e c o n n e c t e d w i t h t h e t e a c h i n g o f engineering design in t h e schools o f e n g i n e e r i n g . In t h e t r a d i t i o n a l a p p r o a c h , a m a t e r i a l o b j e c t requires a r o u g h d r a w i n g b e f o r e one can get d o w n t o t h e necessary specific c a l c u l a t i o n s and d e t a i l i n g . A l o t o f t i m e is r i g h t l y used o n these essential p r o c e d u r e s , y e t so o f t e n n o one w i l l q u e s t i o n h o w t h e idea be­ h i n d a n y p a r t i c u l a r scheme has e m e r g e d . It is t o o c o m m o n a m i s t a k e t o regard t h e f i r s t idea f o r a design as t h e o n l y one or even as t h e best. Lastly I h o p e t h a t t h e b o o k m a y be an i n s p i r a t i o n t o i n d u s t r i a l designers in t r a i n i n g a n d in p r a c t i c e , as it m u s t be i m p o r t a n t f o r designers t o get an idea o f t h e phases a c o m p l e x p r o d u c t goes t h r o u g h , as w e l l as a general v i e w o f t h e relevant c r i t e r i a f o r e v a l u a t i o n .

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1 CREATION OF A PRODUCT

1.1 T h e idea o f f o r m 3

1.2 L i f e o f t h e p r o d u c t 6

1.3 Properties o f t h e p r o d u c t 7

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1. Creation of a Product

1.1 The idea of f o r m

A very great p a r t o f o u r w o r l d consists o f o b j e c t s w h i c h have one f u n d a m e n t a l p r o p e r t y , f o r m : i.e. a shape, a c e r t a i n a r r a n g e m e n t o f parts and an overall s t r u c t u r e . F o r m m a y arise as f o l l o w s ( F i g u r e 1 ) :

1 . A n u n c o n t r o l l e d process, w h e r e the f o r m depends solely o n t h e c o n d i t i o n s o f t h e en­ v i r o n m e n t , e.g. pebbles, m o u n t a i n ranges. 2. A process c o n t r o l l e d b y physical a n d c h e m i c a l

laws as w e l l as t h e c o n d i t i o n s o f t h e e n v i r o n ­ m e n t , e.g. ice crystals, m i c a .

3. A process c o n t r o l l e d b y genes and t h e c o n ­ d i t i o n s o f the e n v i r o n m e n t , e.g. living organisms. 4 . A process c o n t r o l l e d b y t h e wishes o f m e n or animals a n d t h e c o n d i t i o n s o f t h e e n v i r o n m e n t , e.g. m a n u f a c t u r e d p r o d u c t s , a beaver's d a m , b i r d s ' nests. N o w t h a t m a n u f a c t u r e d p r o d u c t s increasingly d o m i n a t e o u r e v e r y d a y w o r l d — indeed w h e r e w h o l e e n v i r o n m e n t s are m a n - m a d e — w e need t o analyse m o r e closely t h e processes b y w h i c h f o r m is d e t e r m i n e d , so t h a t w e m a y design o u r e n v i r o n m e n t as m u c h t o o u r l i k i n g as possible.

As a f i r s t a t t e m p t at this analysis let us e x a m i n e t h e valve in Figure 2. T h e design o f t h e valve a n d t h e parts f r o m w h i c h it is assembled is as f o l l o w s :

T h e t w o c o n n e c t i n g pieces are hexagonal because one m u s t be able t o assemble t h e valve w i t h an adjustable spanner.

T h e r o t a t i n g n u t u n d e r t h e h a n d w e e l is also hex­ agonal so t h a t it can be t i g h t e n e d w i t h a spanner. T h e h a n d w h e e l is r o u n d because t h e h a n d m u s t be able t o grasp it f i r m l y in all p o s i t i o n s .

T h e spindle is t h r e a d e d because o f its f u n c t i o n , w h i c h is t o t r a n s f o r m t h e r o t a r y m o v e m e n t ( o f

t h e h a n d w h e e l ) i n t o one o f t r a n s l a t i o n (of t h e valve seat).

T h e valve seat is a n n u l a r because one m u s t be able t o face it o f f w i t h a m i l l i n g c u t t e r t o m a k e it f i t t i g h t l y against t h e gasket.

T h e inner c a v i t y o f t h e valve is shaped t o f a c i l i t a t e f l o w .

T h e o u t e r f o r m o f t h e valve consists o f t w o i n t e r s e c t i n g c y l i n d e r s .

T h e c y l i n d e r f o r m is d e t e r m i n e d b y t h e m o u l d f r o m w h i c h t h e valve h o u s i n g is cast.

S i m i l a r c o m m e n t s t o t h e above can be made o n t h e c u p a n d saucer s h o w n in Figure 3 :

T h e c u p a n d saucer have r o t a t i o n a l s y m m e t r y , e i t h e r because t h e y are t h r o w n o n t h e p o t t e r ' s w h e e l o r , (if t h e y were made in a m o u l d ) s i m p l y because cups and saucers t r a d i t i o n a l l y have r o t a t i o n a l s y m m e t r y .

T h e c u p is c y l i n d r i c a l because a c e r t a i n appearance was desired.

T h e c u p is smaller in d i a m e t e r at t h e base p a r t l y because i t is t h e n stackable a n d p a r t l y f o r reasons o f appearance.

T h e n o t c h in t h e base o f t h e c u p lets t h e w a t e r d r a i n a w a y if it is washed (upside d o w n ) in a w a s h i n g u p m a c h i n e .

T h e shape o f the handle ensures t h a t t h e part w h i c h is h e l d does n o t get t o o h o t w h e n t h e c u p is being used.

T h e edge o f t h e saucer is t u r n e d u p because it m u s t be able t o h o l d l i q u i d spilt f r o m t h e c u p .

Even if these t w o e x a m p l e s are a l i t t l e s i m p l i f i e d t h e y still s h o w c l e a r l y t h a t t h e design o f a p r o d u c t and its elements d e p e n d s o n m a n y d i f f e r e n t f a c t o r s .

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Creation of a Product 5

Figure 2 The form of the valve is determined by a large number of factors

e.g. m a n u f a c t u r i n g process, f u n c t i o n , ease o f h a n d ­ l i n g , appearance and e c o n o m i c s . A n o t h e r v e r y i m p o r t a n t f a c t o r , w h i c h w e m u s t n o t f o r g e t , is t h e person w h o designs t h e p r o d u c t . H o w e v e r m a n y r e q u i r e m e n t s t h e r e are in t h e s p e c i f i c a t i o n o f t h e design, t h e r e w i l l a l w a y s be r o o m f o r t h e designer t o express his ideas a n d personal j u d g e m e n t .

A n u n d e r s t a n d i n g o f t h e f a c t o r s w h i c h i n f l u e n c e t h e design m u s t be b u i l t o n a k n o w l e d g e o f t h e v a r i o u s stages in t h e life o f t h e p r o d u c t . In t h e f o l ­ l o w i n g pages, t h e r e f o r e , w e w i l l e x a m i n e a m o d e l o f t h e life o f a p r o d u c t f r o m i n c e p t i o n t o d e s t r u c t i o n , as w e l l as a m o r e d e t a i l e d m o d e l o f t h e w a y in w h i c h a p r o d u c t c o m e s i n t o b e i n g .

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6 Creation of a Produc t

1.2 Life of the product

A l l p r o d u c t s are c r e a t e d , used a n d e v e n t u a l l y dis­ c a r d e d . L e t us, t h e r e f o r e , e x a m i n e a l i t t l e m o r e closely w h a t happens t o a p r o d u c t b e f o r e , d u r i n g and after use.

W h e n a p r o d u c t is used i t p e r f o r m s a process w h i c h brings a b o u t an e x t e r n a l change f r o m o n e state t o a n o t h e r . I t is t h e need f o r t h i s t r a n s f o r ­ m a t i o n t h a t has caused t h e p r o d u c t t o be c r e a t e d , f o r e x a m p l e :

Scissors: A w h o l e sheet o f paper - paper d i v i d e d i n t o t w o pieces.

Fiie: A b l a n k w i t h burrs — a b l a n k w i t h c h a m f e r e d edges.

Television: A person w i t h a need f o r e n t e r t a i n m e n t and i n f o r m a t i o n — a person e n t e r t a i n e d a n d i n ­ f o r m e d .

Extruder: Plastic granules — c o n t i n u o u s l e n g t h o f plastic p r o f i l e w i t h t h e r e q u i r e d cross s e c t i o n .

B e f o r e t h e p r o d u c t is used t h e user has b r o u g h t it f r o m a dealer, w h o i n t u r n has b r o u g h t i t f r o m t h e m a n u f a c t u r e r . W h e n i t has e i t h e r served its pur­ pose, w o r n o u t o r b r o k e n , i t is d e s t r o y e d .

If these events are arranged in sequence, w e c a n illustrate t h e life o f t h e p r o d u c t as s h o w n in Figure 4 . T h e s t a r t i n g p o i n t is t h e use f o r w h i c h t h e p r o d u c t is i n t e n d e d . T h e f i r s t phase is t h e design process i n w h i c h possible m e t h o d s o f s a t i s f y i n g t h e user needs are e x a m i n e d , a n d in w h i c h t h e f i n a l l y chosen

p r o d u c t is c o m p l e t e l y s p e c i f i e d . F o r p r o d u c t s w h i c h are t o be p r o d u c e d in great n u m b e r s , t h e design a n d c h o i c e o f p r o d u c t i o n m e t h o d f o l l o w n e x t , b u t f o r t h e sake o f c l a r i t y t h i s phase has been left o u t i n Figure 4 . N e x t comes t h e p r o d u c t m a n u f a c t u r i n g process, after w h i c h t h e p r o d u c t is sold t o t h e dealer, f r o m w h o m i t is resold t o t h e c o n s u m e r . O n l y n o w can t h e p r o d u c t f u n c t i o n a c c o r d i n g t o its i n t e n d e d p u r p o s e . T h e life o f t h e p r o d u c t ends w i t h destruc­ t i o n . T h i s process can be active, w h e r e t h e p r o d u c t m a y be c r u s h e d , t a k e n a p a r t o f m e l t e d d o w n , o r passive, w h e r e i t rusts, c r u m b l e s o r d e c o m p o s e s , etc. Figure 4 s h o w s t h a t , i d e a l l y , i n f o r m a t i o n is f e d i n t o t h e design process f r o m ail o t h e r p r o d u c t - r e l a t e d activities. E f f e c t i v e design is o n l y possible if t h e designer is aware o f w h a t happens b e y o n d t h e d r a w ­ ing b o a r d a n d i n o t h e r d e p a r t m e n t s . T h u s , t h e p r o d u c t is s p e c i f i e d d u r i n g t h e design process, b u t w i t h r e q u i r e m e n t s a n d wishes f r o m all t h e o t h e r stages i n m i n d . It is i m p o r t a n t t o realise t h a t Figure 4 s h o w s t h e general course o f an i n d u s t r i a l l y m a n u f a c t u r e d p r o d u c t . I n p r o d u c t s t h a t are designed a n d m a d e b y t h e same person t h e f i r s t t w o processes can be c o m ­ b i n e d . N o t e also t h a t t h e r e m a y be o t h e r i n p u t t o t h e design process o t h e r t h a n i n f o r m a t i o n o n need or f u n c t i o n , such as an idea f o r a p r o d u c t o r n e w c o m p e t i n g p r o d u c t s . T h e i n p u t s h o w n in Figure 4 , h o w e v e r , is c o n s i d e r e d t h e general o n e , because in t h e o t h e r s i t u a t i o n s o n e still has t o go back a n d start w i t h t h e need. Information Of need _ Feed-back information

r

1 Γ

DBSIGK/

Specificaéion of Ihe product

/f^iv mater Lais

UAKJUrACTUI^E

Object in, first state

^ SALE h

Product

DESmUCT/ON

)Ñaste mo^terials

USIKJQ PKOCESS

Object in second state

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Creation of a Product 7

1.3 Properties of the product

A n y o b j e c t ( p r o d u c t , m a c h i n e , or system) possesses characteristic p r o p e r t i e s . S o m e o f these p r o p e r t i e s m a y be desired, b u t o t h e r s m a y be m o r e o r less u n w a n t e d . T h e m o s t i m p o r t a n t p r o p e r t y o f all is t h e p r i m a r y f u n c t i o n o f t h e p r o d u c t , because it is this t h a t helps t h e user in his need. T h e o t h e r desir-able p r o p e r t i e s m a y b e : pleasing appearance, ease o f h a n d l i n g , s a f e t y , d u r a b i l i t y a n d r e l i a b i l i t y .

Before t h e p r o d u c t is designed t h e r e q u i r e d p r o p e r t i e s s h o u l d be listed b y t h e designer, perhaps in c o l l a b o r a t i o n w i t h t h e user. D u r i n g t h e design p e r i o d w h e n t h e p r o d u c t is c r e a t e d , it is these p r o p e r t i e s t h a t d e t e r m i n e t h e decisions a n d choices t h a t are m a d e .

U n f o r t u n a t e l y o n e c a n n o t design a p r o d u c t in such a w a y t h a t t h e desired p r o p e r t i e s are d e t e r m i n e d one after t h e o t h e r , f o r t h e y are n o t i n d e p e n d e n t variables. We f i n d , h o w e v e r , t h a t five p r o p e r t i e s can be d i s t i n g u i s h e d f r o m all o t h e r s , in t h a t t o g e t h e r t h e y c o m p l e t e l y d e f i n e t h e p r o d u c t . T h e y are:

For the product as a whole:

For each element:

S t r u c t u r e (i.e. t h e elements o f t h e p r o d u c t a n d t h e i r r e l a t i o n s h i p ) F o r m Material D i m e n s i o n Surface

These five p r o p e r t i e s are t h e basic properties. It is i m p o r t a n t t o emphasise t h a t these are t h e variables w h i c h t h e designer can m a n i p u l a t e , a n d it is b y successively d e c i d i n g o n these t h a t a p r o d u c t is c r e a t e d . T h u s all t h e o t h e r p r o p e r t i e s , desirable as w e l l as u n d e s i r a b l e , are d e r i v e d f r o m t h e basic p r o p e r t i e s . T h e a i m in designing is t h a t t h e q u a l i t i e s present in t h e f i n i s h e d p r o d u c t s h o u l d c o r r e s p o n d t o t h e p r o p e r t i e s r e q u i r e d . As t h i s a i m , h o w e v e r , is n o t al-w a y s achieved, al-w e m u s t d i s t i n g u i s h b e t al-w e e n t h e desired p r o p e r t i e s a n d t h e realised ones.

T h u s w e can arrive at a m o d e l o f t h e design process as s h o w n in Figure 5. T h i s s h o w s t h e step-by-step process f r o m t h e analysis o f t h e p r o b l e m t o t h e f i n i s h e d p r o d u c t .

In t h e i n i t i a l analysis stage, t h e p r o b l e m is ex-a m i n e d f r o m ex-all sides. T h i s results o n t h e o n e h ex-a n d in a c o n c r e t e f o r m u l a t i o n o f t h e desired f u n c t i o n , a n d o n t h e o t h e r h a n d , in a list o f t h e desired p r o p e r -ties w h i c h c o n s t i t u t e t h e c r i t e r i a t h a t m u s t m a k e u p t h e b a c k g r o u n d f o r t h e selection o f s o l u t i o n s .

N e x t f o l l o w s t h e stage o f synthesis, i.e. t h e stage in w h i c h t h e p r o d u c t is c r e a t e d . T h i s is d o n e b y r o u g h l y d e t e r m i n i n g step b y step o n t h e basic p r o p e r -ties o f s t r u c t u r e , f o r m , m a t e r i a l , d i m e n s i o n , a n d surface.

W h e n t h e basic p r o p e r t i e s are d e c i d e d o n , t h e design o f t h e p r o d u c t is f i n i s h e d , a n d i t c a n be m a n u -f a c t u r e d . A -f t e r m a n u -f a c t u r e t h e p r o d u c t exists, a n d possesses some 'realisedproperties., w h i c h h o p e f u l l y are close t o t h e 'desired p r o p e r t i e s ' t h a t w e r e f o r m u -lated d u r i n g t h e i n i t i a l analysis.

1.4 The step-by-step creation o f the product

T h e design m o d e l s h o w n in F i g u r e 5 is a g r e a t l y s i m p l i f i e d o n e , t h a t serves o n l y t o give a general v i e w o f t h e design process. It c a n n o t be used as a recipe f o r designing a p r o d u c t . I t c a n , h o w e v e r , be elab-o r a t e d t elab-o t r y t elab-o achieve t h i s . A s w e are p r i m a r i l y c o n c e r n e d w i t h t h e q u a l i t y o f ' f o r m ' , w e w i l l o n l y m a k e t h e m o d e l m o r e d e t a i l e d in t h e stages w h e r e t h e basic p r o p e r t i e s are laid d o w n .

We can call t h e d e t a i l e d m o d e l the product syn-thesis, as it s h o w s t h e i n d i v i d u a l steps t h r o u g h w h i c h DESlfZED

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Figure 5 Tfie basic properties are the variables which the designer can manipulate. The other properties of the product depend on these

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8 Creation of a Product

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Figure 6 The product synthesis. A model of the design process showing the stages in the creation of a product

t h e p r o d u c t is c r e a t e d , see Figure 6. T h e black a r r o w s s h o w t h e t i m e sequence. T h e p r o d u c t s y n ­ thesis takes as its s t a r t i n g p o i n t t h e t w o o u t p u t s f r o m t h e p r o b l e m analysis, n a m e l y o n t h e one h a n d t h e f o r m u l a t i o n o f t h e desired f u n c t i o n - t h e m a i n f u n c t i o n (possibly several s u b - o r d i n a t e m a i n f u n c ­ t i o n s ) o n t h e o t h e r h a n d the list of desired p r o p e r t i e s , w h i c h can also be described as c r i t e r i a f o r an o p t i m u m p r o d u c t .

In Figure 5 w e saw t h a t the n e x t step is t h e

d e t e r m i n a t i o n o f t h e s t r u c t u r e . In t h e p r o d u c t syn­ thesis this v e r y i m p o r t a n t stage is d i v i d e d i n t o a

series o f steps, b e g i n n i n g w i t h a d i v i s i o n o f t h e de­ sired f u n c t i o n i n t o s u b - f u n c t i o n s . T h e n f o l l o w s an e x a m i n a t i o n o f possible means o f realising t h e sub-f u n c t i o n s , a c o m b i n a t i o n o sub-f these i n t o a basic s t r u c t u r e and f i n a l l y an a d a p t a t i o n i n t o a q u a n t i f i e d s t r u c t u r e , w h e r e c r i t i c a l parameters are o p t i m i s e d and w h e r e t h e relative a r r a n g e m e n t o f t h e e l e m e n t s is d e t e r m i n e d .

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F o r m is t r e a t e d in t w o parallel branches, since t h e t o t a l f o r m a n d t h e f o r m o f t h e c o n s t i t u e n t ele-m e n t s are d e t e r ele-m i n e d s i ele-m u l t a n e o u s l y . T h e d e t a i l e d f o r m o f t h e e l e m e n t s includes a s p e c i f i c a t i o n o f materials, d i m e n s i o n s a n d surfaces.

We see f r o m t h e p r o d u c t synthesis. Figure 6, t h a t t h e c r i t e r i a f o r an o p t i m u m p r o d u c t are used t h r o u g h t h e w h o l e design process as a g u i d e l i n e a n d c o n t r o l f o r each step w h e r e a decision is t a k e n .

T h e f o l l o w i n g paragraphs o u t l i n e t h e i n d i v i d u a l stages in t h e p r o d u c t synthesis a n d t y p i c a l e x a m p l e s are g i v e n .

Main functions

T h e main function o f a p r o d u c t is t h e w a y in w h i c h o u t p u t is d e t e r m i n e d b y i n p u t . If w e conceive t h e p r o d u c t as a c o m p o u n d s y s t e m w e can discuss f u n c -t i o n s a-t all levels f r o m -t h e f u n c -t i o n o f -t h e -t o -t a l system ( m a i n f u n c t i o n , o r p o s s i b l y several parallel m a i n f u n c t i o n s ) t o t h e f u n c t i o n s o f sub-systems a n d o f elements ( s u b - f u n c t i o n s ) .

T h e idea o f f u n c t i o n is a v e r y i m p o r t a n t t o o l f o r analysing a p r o b l e m i n t o a series o f clearly f o r m u l a t e d c o m p o n e n t s t h a t express w h a t t h e p r o d u c t m u s t be able t o d o .

Creation of a Product 9

Sub-functions and means

B y means, w e u n d e r s t a n d a s o l u t i o n , i.e. a m e t h o d , a sub-system o r an e l e m e n t , w i t h w h i c h a given f u n c t i o n can be realised. T h e d i v i s i o n o f t h e m a i n f u n c t i o n i n t o s u b - f u n c t i o n s a n d f u r t h e r i n t o sub-sub-f u n c t i o n s , e t c takes place a l t e r n a t e l y w i t h t h e search f o r means t o realise these. O n e possible p r o c e d u r e consists o f a r r a n g i n g a so-called f u n c t i o n / m e a n s t r e e . Figure 7 s h o w s h o w t h e f i r s t stages in t h e f u n c t i o n / means tree f o r an a u t o m a t i c t e a m a k e r m a y l o o k . T h e o r e t i c a l l y t h e f u n c t i o n / m e a n s tree can be d e t a i l e d u n t i l t h e means b e c o m e m a c h i n e e l e m e n t s , o r parts o f m a c h i n e e l e m e n t s . We s t o p w h e n w e have f o u n d means t o t h e m o s t i m p o r t a n t s u b - f u n c t i o n s .

Basic structure

A s o l u t i o n is achieved b y c o n n e c t i n g o n e process f o r each s u b - f u n c t i o n , w h i c h w e call t h e basic s t r u c t u r e . T h e basic s t r u c t u r e can be expressed in b l o c k dia-grams, w o r k i n g ( o r basic) d r a w i n g s ( m a c h i n e s y m b o l s , h y d r a u l i c , p n e u m a t i c , e l e c t r i c s y m b o l s , e t c ) o r o t h e r w i s e s i m p l i f i e d d r a w i n g s . N o decisions are m a d e at t h i s stage as t o ' q u a n t i t i e s ' such as d i m e n s i o n s , relative a r r a n g e m e n t e t c . Figure 1 8 s h o w s d i f f e r e n t basic s t r u c t u r e s o f t h e t e a m a k e r (see Figure 7 ) .

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10

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Creation of a Product 11

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12 Creation of a Product

Quantified structure

T h e q u a n t i f i e d s t r u c t u r e is one w h e r e t h e i m p o r t a n t parameters o f t h e i n d i v i d u a l elements are o p t i m i s e d and s p e c i f i e d , t o g e t h e r w i t h t h e relative a r r a n g e m e n t o f t h e elements. H o w e v e r , n o t h i n g is y e t d e c i d e d c o n c e r n i n g t h e f o r m design o f t h e e l e m e n t s . D i f f e r e n t q u a n t i f i e d s t r u c t u r e s are s h o w n in Figure 9.

Total form

T h e t o t a l f o r m o f t h e p r o d u c t is d e t e r m i n e d a l t e r n a t e l y w i t h t h e f o r m o f t h e e l e m e n t s . T h e r e q u i r e m e n t s o f t h e t o t a l design d e p e n d o n t h e p r o d u c t w e are dealing w i t h . If aesthetic c r i t e r i a are i m p o r t a n t (i.e. in cars, boats, cameras, etc) t h e design o f t h e e l e m e n t s m u s t be a d a p t e d t o t h e t o t a l design.

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Creation of a Product 13 4 .

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Figure 11 S/<etches made in connection with the detail design elements of the teamaker

If t e c h n i c a l and e c o n o m i c c r i t e r i a are w h a t m a t t e r s m o s t (i.e. c a r b u r e t t o r s , gearboxes, satellites, etc) t h e design o f t h e elements m u s t t a k e precedence over t h e t o t a l design.

Form of the elements

T h e f o r m design o f t h e i n d i v i d u a l elements is made at t h e detail design stage o f t h e p r o d u c t . T h e various c o n s i d e r a t i o n s o f t h e f o r m o f t h e f u n c t i o n a l areas m a k e a g o o d s t a r t i n g p o i n t f o r t h i s stage. T h e c r i t e r i a w h i c h m a t t e r at this stage are p r i m a r i l y d e t e r m i n e d b y f u n c t i o n , s t r e n g t h and m a n u f a c t u r i n g m e t h o d s .

T y p i c a l activities at this stage are, f i r s t o f a l l , c a l c u l a t i o n , s k e t c h i n g and d r a w i n g . Free-hand sketches d o n e in a q u i c k and l i g h t t e c h n i q u e are

e x t r e m e l y u s e f u l , see Figure 1 1 . G r a d u a l l y , as t h e f o r m o f t h e elements is s e t t l e d , t h e sketches are re­ placed b y l a y o u t s , p r e p a r e d w i t h a d r a w i n g m a c h i n e , and scale d r a w i n g s .

T h e f i n a l design o f each e l e m e n t requires decisions o n m a t e r i a l , d i m e n s i o n , surface, tolerance and p r o d u c t i o n t e c h n o l o g y .

T h e elements o f t h e p r o d u c t are specified in w o r k i n g d r a w i n g s w h i c h express f o u r o f t h e f u n d a ­ m e n t a l p r o p e r t i e s , f o r m , m a t e r i a l , d i m e n s i o n and surface, as w e l l as f u r t h e r i n f o r m a t i o n such as q u a n t i ­ ties t o be p r o d u c e d , possible m a n u f a c t u r i n g process, n u m b e r o f t h e d r a w i n g , d a t e , etc. T h e f i f t h f u n d a ­ m e n t a l p r o p e r t y , the s t r u c t u r e , is specified in assembly d r a w i n g s w h i c h s h o w h o w t h e c o m p o n e n t e l e m e n t s are t o be assembled, see Figure 12. T h e f i n i s h e d t e a m a k e r is s h o w n in Figure 13.

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14 Creation of a Product

Ί5)

Figure 12 Assembly drawing and working drawing

Product syntfiesis

Each phase in the p r o d u c t synthesis brings t h e designer nearer his goal - t h e f i n i s h e d p r o d u c t . In spite o f t h e c h a n g i n g c o n t e n t s o f t h e phases t h e y all s h o w a t y p i c a l c o u r s e :

1. T h e search f o r s o l u t i o n s , 2. E x a m i n a t i o n o f t h e s o l u t i o n s ,

3. E v a l u a t i o n and c h o i c e o f s o l u t i o n s f o r f u r t h e r w o r k .

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Creation of a Product 15

Figure 13 The finished teamaker (The Laboratory for Engineering design. The Technical University of Denmark)

T h i s course is i l l u s t r a t e d in F i g u r e 1 4 , w h e r e t h e n u m b e r o f s o l u t i o n s is s h o w n as a f u n c t i o n o f t i m e . Each peak c o r r e s p o n d s t o a phase in t h e p r o d u c t synthesis.

T h e search f o r s o l u t i o n s is c a r r i e d o u t b y gener­ a t i n g ideas e i t h e r i n t u i t i v e l y o r s y s t e m a t i c a l l y , t h e m o s t a p p r o p r i a t e m e t h o d s d e p e n d i n g o n t h e phase. T h e a i m in seeking m a n y s o l u t i o n s in a given phase is t o e x p l o r e t h e 'space' c r e a t e d b y t h e great n u m b e r o f t h e o r e t i c a l l y possible s o l u t i o n s . It is s e l d o m pos­ sible t o e x a m i n e all s o l u t i o n s , as t h e y are usually i n n u m e r a b l e . B u t t h e ' s o l u t i o n space' s h o u l d still be e x a m i n e d t h o r o u g h l y so t h a t all t h e m a i n t y p e s o f s o l u t i o n are i n c l u d e d . O n l y t h e n w e can say w i t h reasonable c e r t a i n t y t h a t w e can choose t h e best s o l u t i o n . T h e e v a l u a t i o n o f t h e s o l u t i o n s is m a d e o n t h e basis o f c r i t e r i a w h i c h v a r y w i t h t h e phase a n d t h e degree o f d e t a i l in t h e s o l u t i o n s . A n i n t u i t i v e evalu­ a t i o n m a y t h u s be s u f f i c i e n t in t h e early phases, w h i l e later o n it m a y be necessary t o a p p l y q u i t e a n u m b e r o f m u t u a l l y w e i g h t e d c r i t e r i a . T h e f i n a l result — t h e p r o d u c t — t h u s d e p e n d s o n t w o f u n d a m e n t a l l y d i f f e r e n t f a c t o r s , f i r s t l y o n t h e ideas t h a t are b o r n , a n d s e c o n d l y o n t h e c r i t e r i a t h a t d e c i d e w h i c h ideas are c h o s e n . A closer analysis o f t h e idea o f f o r m can be m a d e f r o m these t w o p o i n t s o f v i e w . T h u s t h e n e x t c h a p t e r deals w i t h t h e m e t h o d s t h a t can be a p p l i e d in searching f o r f o r m ideas, w h i l e C h a p t e r 3 ' F o r m F a c t o r s ' is a b o u t t h e f a c t o r s t h a t m a k e u p t h e b a c k g r o u n d f o r t h e s e l e c t i o n c r i t e r i a . Number of

solutionis

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Figure 14 The search for and examination of solutions, evaluation and choice are a characteristic sequence in the product synthesis

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2 METHODS USED IN FORM DESIGN

2.1 L i m i t a t i o n s 1 9

2.2 S t r u c t u r e v a r i a t i o n 2 1

2.3 F o r m v a r i a t i o n 4 8

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2. Methods Used in Form Design

2.1 Limitations

T h e f i n a l decisions o n a p r o d u c t ' s f o r m n o r m a l l y t a k e place in t h e last phases o f t h e design process, b u t i t is i m p o r t a n t t o realise t h a t b e f o r e t h i s , t h e designer has already been r e f l e c t i n g a n d m a k i n g decisions t h a t have a f u n d a m e n t a l i n f l u e n c e o n t h e f o r m . In t h e previous c h a p t e r (section 1.4) w e saw an e x a m p l e o f t h i s . Let us, h o w e v e r , c o n s i d e r a n u m b e r o f e x a m p l e s w h i c h m o r e d i r e c t l y i l l u s t r a t e t h e i m p o r t a n c e o f t h e early decisions o n t h e f o r m o f t h e p r o d u c t .

T h e m a i n f u n c t i o n o f t h e p r o d u c t — established d u r i n g t h e f i r s t phase o f p r o d u c t synthesis - has a crucial i n f l u e n c e o n t h e t y p e o f p r o d u c t , e.g. w h e t h e r it is a m a c h i n e o r a t o o l . T w o p r o d u c t s w i t h d i f f e r e n t m a i n f u n c t i o n s w i l l t h e r e f o r e be so d i f f e r e n t t h a t it is i m p o s s i b l e t o create one ' i n b e t w e e n ' - t h e y are s i m p l y f u n d a m e n t a l l y d i f f e r e n t . F i g u r e 15 shows an e x a m p l e o f t h i s , n a m e l y a c a l c u l a t o r a n d an abacus. T h e c a l c u l a t o r f u l f i l l s t h e same need f o r an E u r o p e a n as t h e abacus f o r a Chinese. T h e w a y in w h i c h t h e m a i n f u n c t i o n is b r o k e n d o w n i n t o s u b - f u n c t i o n s , as w e l l as t h e means c h o s e n , t o satisfy t h e s u b - f u n c t i o n s is j u s t as i m p o r t a n t f o r t h e design as t h e m a i n f u n c t i o n . T h i s can be i l l u ­ s t r a t e d b y a c o m p a r i s o n o f t w o p r o d u c t s w i t h t h e same m a i n f u n c t i o n b u t w i t h a d i f f e r e n t basic struc­ t u r e .

Figure 16 s h o w s t w o d i f f e r e n t j a c k s , b o t h w i t h t h e m a i n f u n c t i o n - t o t r a n s f o r m a r o t a t i o n a l m a n u a l m o v e m e n t i n t o a v e r y p o w e r f u l v e r t i c a l o n e . T h e f o r m o f t h e t w o jacks d i f f e r s f u n d a m e n t a l l y , because d i f f e r e n t means have been used t o realize t h e i n d i ­ v i d u a l sub f u n c t i o n s , i.e. t h e basic s t r u c t u r e is d i f f e r e n t . We can also n o t e t h a t t h e f o r m o f o n e c a n n o t be g r a d u a l l y c h a n g e d i n t o t h e f o r m o f t h e o t h e r .

Figure 15 Desk calculator arid Japanese abacus or counting frame. The two products fulfil the same need, but the main function is different (Desk calculator reproduced by courtesy of Canon)

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2 0 Methods used in form design

Figure 16 Two car jacks having the same main func­ tion (i.e. similar input and output) but different basic

structures

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Figure 17 Two valves with the same basic structure but with different quantified structures. The lower illustration shows how one structure can be gradually changed into the other

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T h e q u a n t i f i e d s t r u c t u r e brings us t o a level in p r o d u c t synthesis w h e r e w e can m o v e g r a d u a l l y f r o m one s o l u t i o n t o a n o t h e r . In F i g u r e 17 t h e t w o valves have d i f f e r e n t q u a n t i f i e d s t r u c t u r e s b u t t h e same basic s t r u c t u r e , i.e. f r o m t h e p o i n t o f v i e w o f f u n c t i o n t h e y c o n t a i n t h e same e l e m e n t s . T h e y are d i s t i n g u i s h e d b y t h e d i f f e r e n t f o r m design o f t h e elements a n d b y t h e d i f f e r e n t angle o f t h e s p i n d l e a n d t h e h a n d w h e e l . T h e w a y in w h i c h t h e f o r m design o f t h e t w o valves can be m o d i f i e d , so t h a t w e can m o v e g r a d u a l l y f r o m one t o t h e o t h e r , is also i l l u s t r a t e d .

F o r m synthesis m e t h o d s a i m t o c o v e r t h e w h o l e range o f design s o l u t i o n s . We have seen t h a t f o r a chosen basic s t r u c t u r e t h e f o r m design can be c h a n g e d s m o o t h l y f r o m o n e s o l u t i o n t o a n o t h e r . T h e m e t h o d s f o r f o r m synthesis can t h e r e f o r e be n a t u r a l l y described as v a r i a t i o n m e t h o d s w h e r e s o m e

charac-Methods used in form design 21

2.2 Structure variation

Tfie structure variation method

C o n s i d e r t h e t h r e e c o f f e e m a k e r s s h o w n in F i g u r e 18. T h e y all w o r k o n t h e same p r i n c i p l e (i.e. w i t h a s i m i l a r basic s t r u c t u r e ) . B u t w h y are t w o o f t h e m a l i k e , w h i l e t h e t h i r d o n e is q u i t e d i f f e r e n t ? T h e answer lies in t h e q u a n t i f i e d s t r u c t u r e .

Figure 18 Three different coffee makers with the same basic structure. The shape of the top two products is a/most idéntica/. Why is the one below different?

(Courtesty of Melitta, NG Electric, Braun)

t e r i s t i c p a r a m e t e r s are v a r i e d in such a w a y t h a t t h e w h o l e s o l u t i o n space is c o v e r e d . T h e q u e s t i o n o f w h i c h p a r a m e t e r s can be p r o f i t a b l y varied w i l l be e x a m i n e d in t h e f o l l o w i n g c h a p t e r s , w h e r e t h e m e t h o d s are r e l a t e d t o t h e last phases in p r o d u c t s y n t h e s i s , n a m e l y t h e q u a n t i f i e d s t r u c t u r e , t h e t o t a l f o r m a n d t h e f o r m o f t h e e l e m e n t s .

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2 2 Methods used in form design In t h e f i r s t t w o t h e relative a r r a n g e m e n t o f t h e c o m p o n e n t elements is s i m i l a r , w h i l e in t h e last o n e it is d i f f e r e n t . T h e relative a r r a n g e m e n t o f t h e c o m ­ p o n e n t elements is an i m p o r t a n t f e a t u r e o f a q u a n t i f i e d s t r u c t u r e . A n o t h e r i m p o r t a n t f e a t u r e is t h e d i m e n s i o n s o f t h e parts, in t h i s case t h e sizes o f t h e c o n t a i n e r s a n d t h e distance b e t w e e n these.

T h e relative a r r a n g e m e n t a n d t h e d i m e n s i o n s o f t h e c o m p o n e n t elements can be used as v a r i a t i o n parameters in t h e search f o r design s o l u t i o n s . T h i s m e t h o d can be called ' t h e s t r u c t u r e v a r i a t i o n m e t h o d . ' T h e greatest e f f e c t is achieved if t h e i n d i v i d u a l s o l u t i o n s are i l l u s t r a t e d (possibly m o d e l l e d in t h r e e d i m e n s i o n s ) in a t e c h n i q u e w h e r e all super­ f l u o u s details are left o u t . In t h i s w a y one saves t i m e in t h e f o r m u l a t i o n o f t h e s o l u t i o n s as w e l l as c l a r i t y w h e n c o m p a r i n g t h e m .

Figure 19 s h o w s t h e basic s t r u c t u r e f o r c o f f e e m a k e r s , t o g e t h e r w i t h h o w a n u m b e r o f q u a n t i f i e d s t r u c t u r e s created b y v a r i a t i o n o f t h e relative arrange­ m e n t a n d o f t h e d i m e n s i o n s o f t h e elements.

Figure 2 0 shows examples o f t y p i c a l c o f f e e m a k e r s . It d e m o n s t r a t e s h o w a c o m m o n q u a n t i f i e d s t r u c t u r e f o r a n y t w o p r o d u c t s gives a c o m m o n de­ sign c h a r a c t e r , w h i l e d i f f e r e n t q u a n t i f i e d s t r u c t u r e s p r o d u c e w i d e d i f f e r e n c e s in t h e design. T h e s t r u c t u r e v a r i a t i o n m e t h o d is an easy m e t h o d o f g e n e r a t i n g ideas f o r a l t e r n a t i v e s t r u c t u r e s . T h e m e t h o d is based o n t h e v i e w t h a t a n u m b e r o f sug­ gested s o l u t i o n s are needed b e f o r e a s o l u t i o n can d e f i n i t e l y be characterised as g o o d . T h e m e t h o d has been t r i e d in d i f f e r e n t p r o j e c t s i t u a t i o n s , a n d it can be a p p l i e d at m a n y levels, e.g. in b o t h t h e b u i l d i n g u p o f t h e t o t a l system a n d in t h e c r e a t i o n o f small sub-systems. Q u a n t i f i e d s t r u c t u r e can be used f r o m t w o p o i n t s o f v i e w , w h i c h d i f f e r in w h e t h e r t h e f u n c t i o n a l c o n ­ n e c t i o n b e t w e e n t h e e l e m e n t s is i n c l u d e d o r n o t . If these f u n c t i o n a l c o n n e c t i o n s are i g n o r e d , t h e struc­ t u r e v a r i a t i o n m e t h o d gives a n u m b e r o f suggestions f o r a v e r y r o u g h c o n s t r u c t i o n o f t h e p r o d u c t . If t h e f u n c t i o n a l c o n n e c t i o n s are i n c l u d e d , w e get a d e f i n i t e f u r t h e r d e v e l o p m e n t o f t h e basic s t r u c t u r e , w i t h t h e a i m o f o p t i m i s i n g a n d s p e c i f y i n g t h e para­ meters i n v o l v e d . T h i s is s h o w n b y t h e e x a m p l e s given in t h e f o l l o w i n g paragraphs. Q U A N T I F I E D S T R U C T U R E S V a r i a t i o n of r e l a t i v e a r r a n g e m e n t

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2 3

Figure 20 Various types of coffee makers. See a/so quantified structures in Figure 19 (Courtesy of Siemens, Krups, Me/itta, Ptii/ips, and Braun)

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24 Methods used in form design s o r t i n g o f t h e s o l u t i o n s a c c o r d i n g t o such c r i t e r i a as space, o p e r a t i o n a n d appearance. Figure 2 1 shows a n u m b e r o f q u a n t i f i e d s t r u c t u r e s f o r a v a c u u m cleaner, t o g e t h e r w i t h t h e relative a r r a n g e m e n t o f t h e t h r e e m a i n e l e m e n t s . T h e f u n c ­ t i o n a l c o n n e c t i o n b e t w e e n t h e elements is n o t i n d i c a t e d . Figure 2 2 shows s o m e m o d e r n v a c u u m cleaners, w h e r e w e can see h o w g r e a t l y t h e relative a r r a n g e m e n t o f t h e elements influences t h e design.

Q U A N T I F I E D STRUCTURES Variatior^ of r e l a t i v e a r r a n g e m e n t S Y M B O L S t o r

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Figure 21 Quantified structures for vacuum cleaners

Structure variation of tfie main elements

T h e elements t h a t m o s t i n f l u e n c e a p r o d u c t ' s f o r m design are, o f c o u r s e , t h e m a i n ones. We m a y there­

f o r e c o n v e n i e n t l y a p p l y t h e s t r u c t u r e v a r i a t i o n m e t h o d t o a f e w o f t h e m a i n elements o f t h e p r o d u c t , in o r d e r t h a t a f i r s t survey o f t h e possibilities f o r t h e design m a y be c a r r i e d o u t . T h e sketches or m o d e l s made at this stage give a b a c k g r o u n d f o r a f i r s t r o u g h

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2 5

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2 6 Methods used in form design

Let us n o w see h o w t h e s t r u c t u r e v a r i a t i o n nnethod can be a p p l i e d t o a m i c r o s c o p e . T h e basic s t r u c t u r e o f t h e m i c r o s c o p e is characterised b y t h e lenses a n d image planes i n v o l v e d . T o d e t e r m i n e t h e derived s t r u c t u r e , one needs i n f o r m a t i o n o n t h e size and f o c a l length o f t h e lenses, t h e distance b e t w e e n t h e m a n d t h e i r relative a r r a n g e m e n t . F i g u r e 2 3 s h o w s q u a n t i f i e d s t r u c t u r e s based o n v a r i a t i o n o f t h e relative a r r a n g e m e n t o f t h e t u b e a n d t h e o b j e c t plane in r e l a t i o n t o t h e t a b l e .

T h e f u n c t i o n a l c o n n e c t i o n s b e t w e e n t h e elements (e.g. t h e d i r e c t i o n o f t h e rays and focussing) are n o t i n c l u d e d in t h e q u a n t i f i e d s t r u c t u r e s , b u t t h e y can be d r a w n v e r y q u i c k l y . T h e t w o m i c r o s c o p e s i n Figure 2 4 are c o n s t r u c t e d w i t h d i f f e r e n t q u a n t i f i e d s t r u c t u r e s , w h i c h can be c l e a r l y seen f r o m t h e i r v e r y d i f f e r e n t designs. O f t e n it is possible t o use y e t a n o t h e r v a r i a t i o n p a r a m e t e r , n a m e l y t h e n u m b e r o f each o f t h e c o n ­ s t i t u e n t t y p e s o f e l e m e n t . In p r i n c i p l e a v a r i a t i o n o f t h e n u m b e r belongs t o t h e basic s t r u c t u r e , b u t in cases w h e r e an e l e m e n t can be d i v i d e d i n t o several or d o u b l e d — w i t h o u t a l t e r i n g t h e c h a r a c t e r o f t h e basic s t r u c t u r e — t h e n u m b e r m a y w i t h equal r i g h t be v a r i e d u n d e r t h e q u a n t i f i e d s t r u c t u r e . QUANTIFIED STRUCTURES Variation of relative a r r a n g e m e n t

BASIC STRUCTURE

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27

Figure 24 Microscope with different quantified structures. (Courtesy of Olympus and Monolynx)

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2 8 Methods used in form design

In Figure 2 5 , n o t e t h a t t h e range o f s o l u t i o n s is n a r r o w e d c o n s i d e r a b l y d u e t o t h e f a c t t h a t all t h e wheels m u s t be o n t h e same level, a n d t h a t n o ele­ m e n t m a y lie b e l o w t h i s level.

In Figure 2 5 , n o t e also t h a t t h e k e y t o t h e syste­ m a t i c a r r a n g e m e n t c o v e r i n g t h e w h o l e s p e c t r u m o f s o l u t i o n s lies in t h e small f r a m e d figures. These

QUANTIFIED STRUCTURFi^ SYMBOLS

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Figure 25 Quan tified structures for road rollers Figure 2 5 shows possible q u a n t i f i e d s t r u c t u r e s f o r

road rollers, w h e r e t h e v a r i a t i o n parameters are t h e relative a r r a n g e m e n t a n d t h e n u m b e r o f t h e elements. T h e elements w e e x a m i n e are: wheels, engine a n d p o s i t i o n o f t h e o p e r a t o r . O n l y r o a d rollers b u i l t o n t h e t r a d i t i o n a l p r i n c i p l e , w h e r e r o l l i n g wheels a n d t r a n s p o r t wheels are i d e n t i c a l are c o n s i d e r e d .

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3 0 E L E M E N T S ON TWO LEVELS 2 W h e e l s

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3 2 Methods used in form design

Figure 26 Road rollers. (See also Figure 25)

figures express t h e levels o n w h i c h t h e elements lie a reasonable n u m b e r ( f o u r , in t h i s case) o f categories, in r e l a t i o n t o t h e e a r t h . O f course an e l e m e n t (e.g. W h e n a given s t r u c t u r e is chosen f o r closer e x a m i n -t h e engine) m a y lie o n a level b e -t w e e n -t h e ones w e a -t i o n o n e m u s -t s-till feel f r e e -t o v a r y -t h e a r r a n g e m e n -t are c o n s i d e r i n g , b u t as t h e possibilities are o b v i o u s l y o f t h e e l e m e n t s , a l t h o u g h w i t h i n n a r r o w l i m i t s , i n n u m e r a b l e w e begin b y d i v i d i n g t h e p r o b l e m i n t o Figure 2 6 s h o w s s o m e m o d e r n e x i s t i n g r o a d rollers.

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3 3

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3 4 Methods used in form design

Range of solutions for two and three

elements

It is necessary t o ask ' H o w m a n y q u a n t i f i e d struc­ tures is it realistic t o d r a w u p , and is it possible t o get a clear v i e w o f t h e w h o l e range o f s o l u t i o n ? ' In m a n y cases this can be d o n e if o n l y t h e m o s t i m p o r t a n t elements are i n c l u d e d as a basis f o r t h e v a r i a t i o n s . T h e possibilities f o r t w o a n d t h r e e elements are e x a m i n e d b e l o w .

If w e e x a m i n e t h e relative a r r a n g e m e n t o f t w o elements o f a p p r o x i m a t e l y equal size w e can d r a w u p t h e possibilities s h o w n in Figure 2 7 . O b v i o u s l y

t h e angle o f t h e t w o elements can be varied g r a d u a l l y , b u t t h e range o f s o l u t i o n s can be i l l u s t r a t e d b y t h e angles s h o w n .

T h e relative a r r a n g e m e n t o f t h r e e e l e m e n t s o f t h e same o r d e r o f size can be s u b j e c t e d t o t h e same c o n ­ siderations. Figure 2 8 s h o w s a n u m b e r o f possibilities at t h e s h o w n level o f d e t a i l . T h e great n u m b e r o f s o l u t i o n s t h a t emerge t h r o u g h a p e r m u t a t i o n o f t h r e e d i f f e r e n t elements in each o f t h e p o s i t i o n s s h o w n w i l l a l w a y s be q u i c k l y l i m i t e d w h e n w o r k i n g o n a specific p r o d u c t . A n e x a m p l e o f t h i s is s h o w n in t h e e x a m p l e o n page 4 2 .

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3 5

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3 6 Methods used in form design

b o a t being used as t h e source o f energy f o r t h e p u m p . As t h e b o a t r o c k s , a p e n d u l u m o n a vertical axis swings f r o m side t o side and t h i s drives a p i s t o n p u m p . T h e inset o f Figure 2 9 shows t h e basic s t r u c t u r e .

Figure 2 9 also illustrates t h e f a c t t h a t t h e r e are m a n y possible v a r i a t i o n s , as t h e relative a r r a n g e m e n t and t h e d i m e n s i o n s can be changed c o n t i n u o u s l y . It is t h e r e f o r e i m p o r t a n t t o m a k e t h e v a r i a t i o n s at t h e c o r r e c t stage, w h i c h means t h a t t h e n u m b e r o f ele­ m e n t s c o n s i d e r e d m u s t n o t be t o o great (less i m p o r t a n t ones are k e p t f o r l a t e r ) , a n d t h a t t h e parameters m u s t be varied in suitable steps. T h u s each suggested s o l u t i o n s k e t c h e d m u s t be t h o u g h t o f as r e p r e s e n t i n g a c a t e g o r y o f s o l u t i o n s . L a t e r , w h e n c h o o s i n g t h e best suggestions, t h e i n d i v i d u a l categories m a y be e x a m i n e d m o r e c l o s e l y .

Structure variation in connection witfi

function

T h e f u n c t i o n a l c o n n e c t i o n b e t w e e n t h e m o s t i m p o r t ­ a n t elements is expressed in t h e basic s t r u c t u r e , m o s t o f t e n in some sort o f s k e t c h s h o w i n g t h e p r i n c i p l e o f t h e design, w h e r e c o m m o n l y accepted s y m b o l s f o r k n o w n elements ( m a c h i n e , h y d r a u l i c , p n e u m a t i c , electric s y m b o l s , etc) are used. So l o n g as this s k e t c h expresses t h e basic s t r u c t u r e it is e x e m p t f r o m a n y d e f i n i t e d i m e n s i o n s or f o r m , b u t it m a y be t h e s t a r t i n g p o i n t f o r a series o f q u a n t i f i e d s t r u c t u r e s b u i l t o n t h e s t r u c t u r e v a r i a t i o n m e t h o d w i t h t h e relative a r r a n g e m e n t a n d d i m e n s i o n s as parameters f o r each separate e l e m e n t in t h e basic s t r u c t u r e .

Figure 2 9 shows t h e q u a n t i f i e d s t r u c t u r e f o r a baling p u m p i n t e n d e d f o r k e e p i n g a m o o r e d b o a t e m p t y o f w a t e r b y t h e r o c k i n g m o v e m e n t o f t h e

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3 7

QUANTIFIED STRUCTURES BASIC STRUCTURE

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Figure 29 Quantified structures for a baling pump

Variation of: R e l a t i v e a r r a n g e n n e n t - Dinnensions

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3 8 Methods used in form design

Figure 3 0 shows a n u m b e r o f q u a n t i f i e d s t r u c t u r e s f o r a gear, d r a w n u p o n t h e basis o f t h e basic s t r u c t u r e i l l u s t r a t e d in t h e inset. Here t h e relative a r r a n g e m e n t a n d t h e d i m e n s i o n s are n o t i n d e p e n ­ d e n t l y v a r i e d . W h e t h e r it is useful t o keep t h e t w o parameters separate d u r i n g t h e search f o r s o l u t i o n s depends o n t h e n a t u r e o f t h e p r o b l e m , a f a c t w h i c h is also e v i d e n t f r o m t h e o t h e r examples in t h i s s e c t i o n . Figure 3 1 shows e x a m p l e s o f s t r u c t u r e v a r i a t i o n f o r a l a b e l l i n g m a c h i n e . T h e t o p i l l u s t r a t i o n s h o w s q u a n t i f i e d s t r u c t u r e s f o r f o u r e x i s t i n g l a b e l l i n g m a c h i n e s , a n d a n u m b e r o f o t h e r possibilities are s h o w n b e l o w . F i n a l l y , Figure 3 2 s h o w s s o m e q u a n t i ­ f i e d s t r u c t u r e s f o r an e x c a v a t o r , a n d Figure 3 3 d e m o n s t r a t e s h o w t h r e e o f these are e m p l o y e d in e x i s t i n g excavators. Q U A N T I F I E D STRUCTURES Variation o f : Relative a r r a n g e m e n t - D i m e n s i o n s BASIC STRUCTURE Ψ777Λ

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3 9 Q U A N T I F I E D STRUCTURES Variation o f : R e l a t i v e a r r a n g e m e n t - Dimensions B A S I C S T R U C T U R E Roll of l a b e l s Motor Label M j Roll for

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4 0 Q U A N T I F I E D STRUCTURES V a r i a t i o n p a r a m e t e r s A r r a n g e m e n t D i m e n s i o n s B A S I C STRUCTURE

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4 2 Methods used in form design

A coherent example: a tea-maker

In this s e c t i o n w e w i l l e x a m i n e h o w t h e t w o s t r u c t u r e v a r i a t i o n m e t h o d s can be e m p l o y e d successively.

F o r e x a m p l e , c o n s i d e r a t e a - m a k e r , w h e r e b o i l i n g w a t e r is p o u r e d o n t o tea leaves, a n d w h e r e t h e tea brews b e f o r e t h e leaves are r e m o v e d f r o m t h e f i n i s h e d tea. We imagine t h a t w e have reached a stage in t h e design w o r k w h e r e d i f f e r e n t basic struc­ tures have been c o n s i d e r e d , so t h a t t h e q u a n t i f i e d s t r u c t u r e m u s t be c o n s i d e r e d . As a f i r s t a p p r o a c h t o t h e q u a n t i f i e d s t r u c t u r e w e m a y l o o k at t h e relative a r r a n g e m e n t o f t h e t h r e e m a i n e l e m e n t s : a c o n t a i n e r f o r c o l d w a t e r , o n e f o r tea t h a t is b r e w i n g , a n d f i n a l l y one f o r t h e f i n i s h e d t e a , w h e r e t h e l a t t e r m a y perhaps be a t r a d i t i o n a l t e a p o t . T h e m a n y possibilities i l l u s t r a t e d in Figure 2 8 are r e d u c e d since s t r u c t u r e s w h i c h are s y m m e t r i c a l r o u n d a vertical axis are i d e n t i c a l . T h e relative arrangements are s h o w n in Figure 3 4 . N o t e h o w t h e s i m p l e sketches c o n t r i b u t e t o m a k i n g s y s t e m a t i c v a r i a t i o n easy. V a r i a t i o n s can be m a d e b y d r a w i n g f r o m o n e s o l u t i o n t o a n o t h e r .

A m o n g t h e s o l u t i o n s in F i g u r e 3 4 are s o m e w h i c h can be e x c l u d e d o n t h e basis o f c r i t e r i a such as h a n d l i n g (the t e a p o t o u g h t n o t t o be inside t h e o t h e r c o n t a i n e r s ) a n d q u e s t i o n s o f space (e.g. t h e t h r e e e l e m e n t s in a r o w c a n be o m i t t e d ) . T h e n e x t step in d e c i d i n g o n m o r e d e t a i l e d q u a n t i f i e d s t r u c t u r e s consists o f c o n n e c t i n g t h e usable s t r u c t u r e s in F i g u r e 3 4 w i t h a basic s t r u c t u r e w h i c h i t is assumed has been chosen b e f o r e t h e relative a r r a n g e m e n t o f t h e e l e m e n t s was c o n s i d e r e d . T h e inset in Figure 3 5 s h o w s a r o u g h s k e t c h o f a sug­ g e s t i o n f o r a basic s t r u c t u r e . T h e m a i n i l l u s t r a t i o n s h o w s t w e n t y d i f f e r e n t q u a n t i f i e d s t r u c t u r e s expres­ sing t h e relative a r r a n g e m e n t o f t h e elements a n d t h e f u n c t i o n a l r e l a t i o n s h i p b e t w e e n t h e m .

It is possible, in t h e l i g h t o f t h e diagrams i n F i g u r e 3 5 , t o discard s o m e s t r u c t u r e s . T h e f a c t o r s t h a t c a n be used as c r i t e r i a are: p r i c e ( c o m p l e x i t y ) , appear­ ance, h a n d l i n g a n d effectiveness. T h e f i n a l c h o i c e o f s t r u c t u r e can o n l y be safely m a d e a f t e r c o n s i d e r i n g t h e design possibilities f o r s o m e o f t h e m o s t p r o m i s i n g s t r u c t u r e s .

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4 3 Q U A N T I F I E D STRUCTURES V a r i a t i o n of r e l a t i v e a r r a n g e n n e n t SYMBOLS [K\ B o i l e r B r e w i n g vessel (ψ) Teapot

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H e a t i n g e l e m e n t w h i c h forces t h e b o i l i n g w a t e r i n t o t h e b r e w i n g vessel. A f t e r b r e w i n g , a r e m a i n i n g a m o u n t o f w a t e r is b o i l e d , w h e r e b y t h e tea is f o r c e d i n t o t h e t e a p o t

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4 6 Methods used in form design

Structure modelling

W h e n v a r y i n g t h e s t r u c t u r e it is a l w a y s necessary t o visualise t h e possibilities. Diagrams w i t h s i m p l i f i e d s y m b o l s are suitable f o r t h i s p u r p o s e . T h i s can be seen f r o m t h e previous e x a m p l e s in this s e c t i o n . M a k i n g t h r e e - d i m e n s i o n a l m o d e l s m a y , h o w e v e r , also be relevant. Figure 3 6 shows s o m e s t r u c t u r e s f o r a tea m a k e r m o d e l l e d w i t h s i m p l e t o y b r i c k s . (See also Figure 3 4 ) .

Where m o r e c o m p l e x s t r u c t u r e s are being c o n ­ sidered, sketches are n o t s u f f i c i e n t , a n d In such cases t h r e e - d i m e n s i o n a l m o d e l l i n g is t h e o n l y p o s s i b i l i t y . A t y p i c a l t h r e e - d i m e n s i o n a l m o d e l is s h o w n in Figure 3 7 , w h e r e q u a n t i f i e d s t r u c t u r e s f o r a test t u b e f i l l i n g m a c h i n e are s h o w n . ( F o r a m o r e d e t a i l e d d e s c r i p t i o n o f t h e m a c h i n e see page 5 6 ) . As t h e i n ­ t e n t i o n o f such a m o d e l is t o f i n d o u t w h i c h relative a r r a n g e m e n t s o f t h e e l e m e n t s are realistic, t h e m o d e l m u s t be c o n s t r u c t e d in such a w a y t h a t t h e e l e m e n t s can be q u i c k l y m o v e d t o n e w p o s i t i o n s . F o r t h i s pur­ pose b r i c k s o f p o l y s t y r e n e are e x t r e m e l y u s e f u l , p a r t l y because t h e y are easy t o carve, a n d p a r t l y be­ cause t h e i r l i g h t w e i g h t a l l o w s a b r i c k t o be h e l d fast in a n y p o s i t i o n b y j u s t being pressed d o w n o n t o a t h i n s p i k e . N o t e here t h a t w e are t a l k i n g a b o u t s t r u c t u r e m o d e l s a n d n o t a b o u t f o r m m o d e l s . T h i s means t h a t t h e c o m p o n e n t e l e m e n t s o n l y need t o be m o d e l l e d b y t h e space t h e y w i l l o c c u p y a n d n o t b y t h e i r f o r m details. (See also c h a p t e r 5, w h i c h also deals w i t h t h r e e - d i m e n s i o n a l s t r u c t u r e m o d e l s ) .

Figure 36 Mal<ing three-dimensional models of quantified structures for a teamaker with the aid of toy bricks. (See also Figure 34)

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4 7

Figure 37 Three-dimensional models of quantified structures for a test tube filling machine. On an evaluation of space and handling conditions the best structure may be chosen

References

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