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 NUNITED 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
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First published in Denmark in 1976 as 'Systematisk udformning af industriprodukter'
First published in English 1979 © E. Tjalve, 1979
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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
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 .
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
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 .
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 .
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^terialsUSIKJQ PKOCESS
Object in second stateCreation 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
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 .
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 ) ./ \ FUAJCT/OKJ
MEAKJS
Pass through i^ecittn^ sc/ir/fice Te(Pi process w ¿ M tea eKtractNormal tea process Tea process wLtk per/i/iSCOH
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10
Creation of a Product 11
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.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.
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 .
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
£xciniLhation ofsoLiAtcoMS T^meFigure 14 The search for and examination of solutions, evaluation and choice are a characteristic sequence in the product synthesis
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
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)
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
B a s i c s t r u c t u r e
ψ
-o
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
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 .
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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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)
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.
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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
2 5
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
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Figure 24 Microscope with different quantified structures. (Courtesy of Olympus and Monolynx)
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
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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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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.
3 3
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
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 .
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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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Figure 29 Quantified structures for a baling pump
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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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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 .
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 tTi
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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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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