- Email: [email protected]
Parts Presentation to Multi-Arm Assembly Robots
Parts Presentation to Multi-Arm Assembly Robots A. H. Redford. E. K. Lo and P. J. Killeen, Department of Aeronautical and Mechanical Engineering, University of Salford - Submitted by A. W. J. Chisholm. Research Professor of Engineering, University of Salford ( 1 )
Of t h e pan:, m t h o d s o f o r i e n t i n o a n d p r e s e n t i n g ? a r ~ b l yn a c h i n e s , t h e 7,:ibrz:qry i s b y f a r t h e rmst cfxmm d e v i c e b e c a u s e o f i t s l a r z g e c a y ; a c i t y , n i g h r a t e of c o n p a c t s t r u c t u r e a n d a b i l i t j ' t o d e a l wit!: a wide a r t sl.;ipes. ' : h C o r t u n a t e :y are r e l a t i v e l y e x p e n s i v e b o t h i n terms of c a u i n r c n nd changeover costs, e s p e c i i s i n t e r j r a t e d i n a n u l t i - a r n r o b o t i c a s s e r h 1 . y syst t d t i l i s i t i o n i s 1oi.i inci f r e q u i p r e n t s c h a n g e o v e r s a r e n e c e s s a r y d u e t o t h e recyui r c n c r t t o assemJj1.e d i f f e r c n sliown t l i l t i t i n t h e 4 i s p r a 1 1 c r t i a n a t e l v h i g h m s t c,f t5e fee(l:nq e q t i i r m e f i t , r : i makes r o b o t i c a s s e r ? b l y s y s t e m s d i f f i c u ; t t o j u s t i f y e c o n o m : c a l l y a n d t h c r costs a s s o c i a t e d w i t h t h i s e q u i p m e n t c o n s i d e r a b l y . A l i n e a r v i b r a t o r y f e e m b l y c q u i p m e n t i s c u r r e n t l y b e i n q d e v e l o p e d a t t h e I n i v e r s i t : , n f s.:..!forc?. T t i s a n t ? c:p a t c d t h a t t h c u s c o f r u l t i p l c L i n e d r f e e d t r a c k s n o u n t e d on a common d r i v e i i i i l n o t o n l y r c d u c c t h c c a p i t a l c o s t o f t h e e q u i n m e a t p e r track. a n d t h e chan5:ecY:er c o s t s b u t alsc t h z t o f t h e r i r i e n t i r q c:e.ilce p r o d u c t i o n s i n c c s i r n p l e s t r a i q h t f e e d t r a c 2 s x i l l be p r c d u c e d o n a n :?C m a c h i n i n ? c e n t r e u s i n g i s t e r a c t i v e computer-aide6 p a r t prooramninq. 'This n a p e r d e s c r i b e s t h e p h i l o s o p l i y 3 : t h e d ? y r o a c h , t h e d e s i r n , C o n s t r u c t i o n a n d t e s t i n q o f t h e b a s i c f e e d e r and t h e n a r t ? r n q r m F i n q nct.hods f n r s i n p l e : , r j c n t i n ? s y s terns. LUC
1.1
TO A MULTI-ARZ' ASSEW3LY RORO?
Introduction ~
Of t h e v a r i o u s t y y s of a u t o r r . a t i c a s s e m b l y , mu1ti.-arm r o b o t i c assembly n i f f c r s from a l l o t h e r forms i n t h a t a s s e m b l y i s c a r r i e d o g t i n s e r i e s r d t h e r t h a n i n pm-al l e l , i . e . f o r a l l f o r n s o f l i n e asserbly w h e t h e r i t . u s e s d e d i c a t e d workheads or s i n n l c a r n r o b o t i c d e v i c e s , a p r o d u c t i s assembled e v e r y r a c h i n e c y c l e i r h e r e a s i n multi-arm robotic assembly, a p r o d u c t is o n l y dsscmblcd a f t c r a number o f c y c l c s a n d t h i s is d e t e r r r . i n c d by t h e number o f a r m s and t h e n u v b e r of D a r t s i n t h c product. T h u s , f o r m u l t i - a r m r o b o t i c assemilly t h e n e c e s s a r y r a t e o f s u p p l y o f p a r t s is g e n e r a l l y v e r y much l e s s t h a n t h a t w h i c h a u t o m a t i c f c e d i n c d e v i c e s a r e c a p a b l e of s u p p l y i n ? a n d t h i s results i n i n c f f i c i e n t u s e o f t h e f e e d i n g d e v i c e s and a c o n s c q u c n t i a l i n c r e a s e i n t h e f e c d i n u cost o f e a c h p a r t d e l i v e r e d . F u r t h e r , t r a d i t i o n a l a u t o r a t i c p a r t s f e e d i n g and o r i e n t a t i o n i s c a r r i e d o u t by a f e e d i n g d e v i c e which i s c o n f i q u r e d t o m e e t t h e r e q u i r e m e n t s of d p a r t i c u l a r or, a t t h e most, a very r e s t r i c t e d ranqc of p a r t types. '",. L . ~ U S , althouc!h d e d i c a t e d f e e d e r s c a u s e f e w p r o b l c v s i n h a r d a u t o m a t i o n where p r o d u c t i o n r u n s a r e v e r y l o n q , c h a n a e s i n p r o d u c t d e s i q n arc rare a n d .where p r o d u c t i o n r a t e s a r c h i g h , t h e y are u s u a l l y too i n f l e x i b l e f o r r o b o t i c a s s e m b l y w h i c h h a s t o c o p e w i t h d rilnne o f product s t y l e s manufactured in r c l a t j v c l y snali b a t c h e s a t low speed.
o u t ( 1 ) t o e x a m i n e tl:e c o s t o f p a r t s f e e d i n q t o series assembly robotic d c v i ces u s i n g a v a r i e t y o f e x i s t i n g a n d h y p o t h e t i c a l f e c d i n q systems.
A r e c e n t s t u d y has been c a r r i e d
1.2
Feedinq Systems Considered
1). D e d i c a t e d f e e d c r s .
Levcl b o w l f e e d e r w h i c h i s c a p a b l e o f d c l i v c r i n q y s r t s s i n o l y b u t not i n o r i e n t a t i o n , a set o f p a r t s r e v e r s i n ? u n i t s , a movinc- s o l i d s t a t e c l n e r a and t h e a s s o c i a t e d image p r o c c s s i n q e q u i p m e n t . P a r t s are f e d i n t o t!:e r e v c r s i - n g u n i t s s c a n n e d by t h e c a r e r a a n d ej t h e r a c c c p t e d o r r f v e r s c d and r e - s c a n n e d . Pdrts i n ii l i m i t e d n u r b e r o f o r i e n t a t i o n s a r e t h e n p i c k e d u: by t.hc r o h o t a n d t u r n e c i i n t o t h e r e q u i r e d o r i e n t a tion. B e c a u s e t!ie b o w l s do n o t n e e d t o b e c o n f i g u r e d to p e r f o r r r p a r t s o r i e n t i n ? , t h e y :Ire e a s i l y a d a p t e d to accommodate d i f f e r e n t p a r t t y p e s b u t t h e r a n o f o f o a r t s h a p e s c a p d l ~ l eo f beint! d k d b y t h i s t y p e of s y s t e m is l i m i t e d . 5!
Xu1 t i - p n r t
feeder
T!w m u l t i - p a r t f e e d e r i s a n o n - s t a n d a r d f e e d l n q y s t e m desiiined t o f e e d and o r i e n t s e v e r a l p a r t s f o r r e s e n t a t i o n t o a robot u s i n ? m u l t i p l e t r a c k s b u t a cocimon d r i v e u n i t ( 3 ) . Tn t h e s t u d y i t i i a s a s s u n e d t h a t t h e f e e d e r w o u l d b c c a p a b l e o f handlinr: two di f f c r c n t p i r t t y p e s . fi}
!+iq;izine s y s t e m s
Bec2usc a u t o m a t i c f e e d i n g s y s t e m s f o r r o b o t i c assembly c: a t w e l l b e l o r maxin?um r a t c , i t a d v a n t a a e c o u l d be g a i n e d b y ny d u t o m a t i c p a r t s f c c d e r s worknd t h e n t r a n s f e r r i n a t h e p a g a z i n c s t c l t!ie r o b o t a s s e m b l y p o i n t s . A l t h o u g h t h e macjdzines w o u l d L e e x p e n s i v e t h i s t.ype of s y s t e m h a s t h e f u r t h e r a d v a n t a q e o f p r o v i d i n g a n i n s p e c t i o n f u n c t i o n 2 n d also d e - c o u p i i n p the i n s e r t i o n o p e r a t i o n f r o m t h e h a n d l i n g operation. I n t h e s t u d y , magazines l o a d e d by d e d i c i i t e d f c e d e r s , proprsmmable f e e d e r s and m u l t i - p a r t f e e d e r s w e r e a11 considered. Tn a d d i t i o n t o t h e a b o v e , two f u r t h e r m a q a z i n c f e e d i n g s y s t e m s were e x a m i n e d , m a n u a l l o a d i n ? o f r a g a z i n c s a n d m a q a z i n e s l o a d e d a t t h e p o i n t of p i e c e p a r t m a n u f a c t u r e
T h i s s y s t c r . *would c o n s i s t , t y p i c a l l y , o f v i b r a t o r y b o ~ l f e c d e r s each o f w h i c h w o u l d u s e d e d i c a t e d b o w l s , 7) 3anual fecdinq o r i e n t i n q d e v i c e s and a n c i l l i a r y cquipeent f o r each ks a r c f e r c n c e f o r c o r r p a r i n q t h e v a r i o u s f e e d i n r r s y s p a r t t y p e . ' G I U S , t h e number o f b o w l s n e c e s s a r y f o r a t e m , m a n u a l l o a d i n q of a s s c m b l y r o b o t s w a s analysecl p l a n n e d v a r i e t y o f p r o d u c t s w i l l be e q u a l t o t h e numxhere an o p e r a t o r w o u l d l o a d p a r t s i n t o f e e d t r a c k s h e r o f d i s t i n c t p a r t types w h i l s t t h e nurber of d r l v e i n s u i t a b l e l o c a t i o n s i n t h e r o b o t ' s iiork a r e a . u n i t s n e e d e d w i l l be e q u a l t o t h e masimun, number of p a r t s i n any s t y l e of t h e p r o d u c t . 1 . 3 Cost o f Feedin2 2).
Programmable f e e d e r s
A p r o g r a m m a b l e f e e d e r is c o n s i d e r e d t o be o n e w h i c h
by t h e use of s u i t a b l e a u t o m a t i c a l l y a d j u s t a b l e t o o l i n g i s versatile enouqh to f e e d and o r i e n t a wide v a r i e t y of p a r t s , i n d e p e n d e n t o f t h e i r s h a p e , s i z e e t c . T h u s , t h e number o f feeders r e q u i r e d w i l l b e e q u a l t o t h e maximum nu?rber of p a r t . t y p e s f o r a n y o f t h e p r o d u c t s t y l e s and c h a n q e o v e r t i n e f o r t h e f e e d e r w i l l be s e n s i b l y zero a l t h o u c h t h e t i n e t a k e n t o n d j u s t o r change a n c i l l i a r y equipment w i l l s t i l l n e e d to be taken i n t o account. 3)
D e d i c a t e d f e e d e r s s e r v i n g more t h a n one r o b o t .
As m e n t i o n e d p r e v i o u s l y , d f d i c a t c d f c e d e r s a r e u n d e r -
u t i l i s e d when u s e d i n r o b o t i c a s s e m b l y a p p l i c a t i o n s a n d i t w c s t h o u y h t t h a t d e d i c a t e d f e e d e r s s e r v i n c more t h a n o n e robot w o u l d r e s u l t i n more e f f c c t i v e u s e o f t h e feeders. C l e a r l y , t h i s t y ? e of s y s t c m w o u l d o n l y be p r a c t i c a l i f a number o f m u l t i - a r m r o b o t s w e r e b e i n n used i n rlosc p r o x i m i t y . 4)
F e e d e r s w i t h s i m p l e computcr v i s i o n
The v i s i o n s y s t e r ? c o n s i d e r e d was m o d e l l e d o n e q u i p m e n t d e v e l o p e d b y H I t a c h i (2) w h i c h c o n s i s t s o f n mi11 t i -
Annals of the ClRP Vol. 32/1/1983
G e n e r a l l y , t h e c o s t o f f e e d i n g p a r t s c o n s i s t s o f two e l e r r e n t s : d i r e c t l a b o u r costs and d e n r e c i a t i o n o f c a p i t a l equipment. The f o r m e r c a n b e c l a s s i f i e d i n t o m a t e r i a l h a n d l i n g cost, s y s t e r t e n d i n q cost, f a u l t c o r r e c t i o n cost a n d c h a n p e o v e r c o s t . T h e l a t t e r c a n h e c l a s s i f i e d as b a s i c e y u i p x e n t d e p r e c i a t i o n a n d toolin? depreciation and t h e values assigned to these w i 1 1 d c p e n d o n w h e t h e r t h e f e c d c r s o r p a r t s of f e e d e r s , a r c e x c l u s i v e t o t h e f e e d i n ? o f a : > a r t i c u l a r ?art o r w h e t h e r t h e y are q e n e r a l f o r a l l o p e r a t i o n s . 1.4
Xesults
The a l p r i t h n i s d e v e l o p e d f o r d e t e r m i n i n g p a r t s f e e d i n g costs were t e s t e d u s i n a two d i f f c r e n t p r o d u c t f a r r i l i e s W i t h t h e same sets o f c o s t a n d t i r e d a t a f o r t h e :'drious t y p e s of f e e d j n q e q u i p m e n t . Both f a m i l i e s c o n s i s t e d of t e n d i f f e r e n t p r o d u c t s c a c h c o n s i s t i n a o f n parts. For o n e p r o d u c t f a m i l y s i x t y - s i x d i f f c r e n t r t s were u s e d w h i l s t f o r t h e o t h e r o n l y t w e n t y f f e r e n t p a r t s were u s e d . T o t - a 1 demand f o r e a c h p r o d u c t w a s t h e same ( 2 0 0 , 0 0 0 p r o d u c t s ) and f o r s i m p l i c i t y i t WAS a s s u m e d that I)atcli s p l i t t i n r j w o u l d he of equal batch s i z e s whatever t h e s i z e of t h e batch. Tile s m a l l e s t . b a t c h s i z e w a s f i f t y :->roductsw h i l s t thc ! a r q e s t YRS 1 3 5 0 and tor both s t u d i e s i t X R S
399
a t :he r o b o t wou:il i ~ o -Jne ?F?r1 e.:Tir-j l:'ircc% (217.
t h e F e e d e r St1uj.v 4.
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- t!i;n 4 0 0 , b d t o i i s i z e s s c c o n d o r d e r e f f e c t , i . e . t h e rate o f d e c r e a s e c f f e e d i n g c o s t ',;ith i n c r e a s i n u i n t c h s i z e i s r e l . i t i - v ~ e ; ys ? , i l l .
becones
. I
2) F 3 r a l i Lypes r f f c c d i n q s y s t e n , t f e e d i n s T a r t s t o 3 muit:-arm rolwt is f i v e t o t e n tip.es 5 s c s p c n s l v e a s f e e d i n y g i r t s t o
.1
3i
? o r r e a s o n a b l e batc!i
s i z e s , t?.e d i f f e r e n c e b e t w e e n a n d tb,e .#orst i s surprisingly s m a l l (a o n e h u n d e r e c pcr c e n t c h a n g e ) . 4)
X i t h t h e e x c e p t i o n of t h e s y s t e r r x h e r e v a c a z i n e s
system
are l o a d e d at t h e p o i n t o f n a n u f a c t u r e , m a g a z i n e f e e c i z q by w h a t e v e r systcrr. o f l o a d i n g i s more e x p e n s i v e than bv
the
method of
1 n . p o r t a n t t h a t p d r t s w h i c h a r e r e j e c t e d c a n be :on*;eyed tij :i ? o u , i l i s e d drea f o r t r a n s f e r back t o t h e o r i e n t i n q tr,ick. Several possibiiities exist: tPe r e t u r n ?rack could u t i l i s e a s l a t t e d b e l t conveyor Fii t e r n a t i v e 1 y , t h e re t 11r n v i t il a p p r o p ri a t c e l e v a t i on t r s c k c o u i d b e a v i b r a t o r y conve:,:or w i t h some for. o f s e i e v a t o r a t -13 a u n r o p r i a t e p o s i t i o r . . After i r : a t i o n -f t h e v a r i o u s p o s s i b i l i t i e s a n d w i t h ZI icdye o f t h e mechanics o f vlbr;ltory conveycrs i t wiis d e c i d c d t h a t , w i t h c a r e f u l design, t h e o r i e n t i n ? :rack ~ n dt h e r e t u r n t r a c k c c u l 6 b e d r i v e n b y .I sirlc?le .Jibration source. For t h i s , i t is necessary t h a t t h e n r i a n t i n n t r n r k h a s ;1 sl i a h t n e c a t i v e i n c l i n a t i o n ,
directly.
t i o n and t h a t a v i b r a t i c n a n q i e i s chosen which x i 1 1 a l l o w f o r w a r d c o n v e y i n n on b o t h t h e o r i e n t i n ? a n d return tracks. '.'arious x e t h o d s o f e l e v a t i n g t h e p a r t s f r o m t h c c o l l e c t i . o n a r e a on t h e r e t u r n t r a c k t o t h e i n l c t a r e a t o the orientin? track are possible. The c u r r e n t d e s i n n o f f e e d e r u s e s a l i f t t y p e mechanism p o w e r e d ltlv a u n e i ; m a t i c c v l i n d e r a n d t h i s a o o e a r s to work * ~, s a t i s f a o t o r i ly. ~t i s a n t i c i p a t e d t h a t i n f u t u r e , the f e e d e r w i l l be re-desiqned such t h a t t h e e l e v a t i n g mechanism i s a t t h e e n d o f t h e o r i e n t i n g t r a c k as t h i s woJld a l l o w t h e r o b o t t o p e r f o r m t h e e l e v a t i n g f u n c t i o n and t h i s would e l i m i n a t e t h e need f o r 2 s e p a r a t e e l e v a t i n g mechanism. ~
51 R e d u c i n ? t h e n u r b c r o f u n i q u e p a r t t y p e s i n t h e p r o d u c t h a s a n i n f l u e n c e on t h e r e l a t i v e Ferits o f t h e v a r i o u s systems b u t c o n s i s t e n t l y , t h e simple v i s i o n s y s t e m , t h c m u l t i - p a r t f e e d e r s;'ster a n d t h e n a g a z i n i n g a t t h e p o i n t o f m a n u f a c t u r e s y s t e ~were t h e t h r c c m o s t economic s y s t e m throuohout t h e s t u d y . 6) The v i s i o n s y s t e r , was t h e m o s t a p p r o p r i a t e f o r p r o d u c t f a m i l i e s w i t h many u n i q u e p a r t t y p e s .
7) The m u l t i - p a r t f e e d e r was m o s t a p p r o p r i a t e f o r p r o d u c t f a m i l i e s w i t h r e l a t i v e l y few u n i q u e p a r t types. 2.
S P E C I F I C A T T O N F O R A MULTI-PART FEEDER
Because t h e r u l . t i - p a r t f e e d e r has been i d e n t l f i c d as t h e most e c o n o m i c ' v e r s a t i l e ' p a r t s f e e d e r , p a r t i c u l a r l y when t h e p r o d u c t f a m i l y d o e s n o t c o n t a i n many u n i q u c p a r t t y p e s , i t w i s d e c i d e d t h a t a s p e c i f i c a t i o n would be w r i t t e n f o r t h i s type o f f e e d e r and t h a t a f e e d e r would b e d e s i n n e d which would l n c o r p o r d t e t h e requirements of the s p e c i f i c a t i o n . T a b l e 1 shows t h e c h a r a c t e r i s t i c s of a v i b r a t o r y bowl f e e d e r and t h e requirements o f a multi-arm r o b o t i c f e e d e r and i t c a n b e s e e n t h a t w i t h t h e e x c e p t i o n of t h e c a p a b i l i t i e s o f b e i n g a b l e t o f e e d a n d o r i e n t il i i i d e v a r i e t y o f p a r t g e o m e t r i e s a n d t h e p h y s i c a l s i z e o f t h e feeder, t h e requirements o f d robotic f e e d c r d o n o t match t h e c h a r a c t e r i s t i c s o f a v i b r a t o r ; , bowl f e e d e r . I f i t i s a c c e p t e d t!?at t h e b a s i c r e q u i r e m e n t is t h 3 t a w i d e v a r i e t y of p a r t s h a p e s n e e d t o b e a c c o r r p o d a t e d , t h i s c a n o n l y r e a s o n a b l y be d c h i e v e d u s i n g a v i b r a t o r y fecder. If a further requirerent is t h a t the capital c o s t p e r p a r t f e d n e e d s t o h c lower t h a n f o r a d e d i c a t e d f e e d e r i t i s n e c e s s a r y t h a t a common d r i v e u n i t be used t o s u p p o r t s e v e r a l t r a c k s ; w h i l s t t h i s i s n o t i r r p o s s i b l e usin: a v i b r a t o r y bowl f e e d e r , i t i s v e r y much e a s i e r t o a c h i e v e t h i s o b j e c t i v e u s i n g a linear vibratory feeder. T h e main d i s a d v a n t a g e of a l i n e a r f e e d e r i s t h a t t h e r e is n o simple r e - c i r c u l a t i o n p a t h f o r p a r t s which a r e r e j e c t e d i n t h e o r i e n t i n g s e c t i o n s a n d t t i s r e c r u i r e m e n t h a s t o b e m e t by some n o n - v i b r a t o r L r r c a n i . Kowever, a f u r t h e r a d v a n t a g e o f l i n e a r o r i e n t i n g t r a c k s i s t h a t i t j.s easier t o c o n s t r u c t t h e o r i e n t i n g d e v i c e s than it w o u l d b e i n a bowl f e e d e r . W i t h m u l t i p l e t r a c k i n g p e r d r i v e u n i t , t h e basic c o s t p e r track is reduced b u t a f u r t h e r high c o s t element is t h a t a t t r i b u t a b l e t o t h e development o f o r i e n t i n g devices. For very simple o r i e n t i n g problens t h i s is r e l a t i v e l y i n e x p e n s i v e b u t i n many c a s e s t h e d e v e l o p ment work n e c e s s a r y t o a c h i e v e a s a t i s f a c t o r y s o l u t i o n is e x t e n s i v e a n d t y p i c a l l y a bowl f e e d e r c o n p l e t e w i t h all t h e n e c e s s a r y o r i e n t i n g d e v i c e s i s d o u b l e t h e cost of the basic feeder. Bowl f e e d e r o r i e n t i n ? d e v i c e s a r e g e n e r a l l y craftsman produced but a m o r e s a t i s f a c t o r y s o l u t i o n , o a r t i c u l a r l y f o r l i n e a r t r a c k s would b e t o p r o d u c e t h e o r i e n t i n o s e c t i o n s u s i n g an NC machininq c e n t r e . This oresupuoses t h a t t h e aeonetry of t h e d e v i c e s i s i n o w n a n d f o r t u n a t e l y , f o r many d e v i c e s , t h i s i n f o r m a t i o n c a n b e o b t a i n e d fron: t h e c l a s s i f i c a t i o n and coding system f o r p a r t s h a n d l i n g developed a t t h e University of Vassachusetts. Using t h e p a r t ' s c o d e a n d t h e p a r t s i z e i t was t h o u g h t r e a s o n a b l e t o develop computer s o f t w a r e x h i c h would r e s u l t i n t h c p r o d u c t i o n o f a n XC p a r t p r o q r a m w h i c h c o u l d b e used t o p r o d u c e a f u l l o r i e n t i n ? s y s t e m from s o l i d b a r ; t h i s w i l l be d e a l t w i t h i n t h e n e x t s e c t i o n . If I t 1 s accepted t h a t
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The f e e d e r , a s d e s i g n e d , i s shown i n I'ig.1; tile i n c l i n a t i o n o f t h e o r i e n t i n g t r a c k i s - 2 degrees, the ~ n c l i n a t i o no f t h e r e t u r n t r a c k i s -10 d e g r e e s a n d t h e v i b r a t i o n angle is 15 deqrees. 'rests t o d a t e o n a ,wide r a n g e o f p a r t s w i t h d i f f e r i n g f r i c t i o n a l c h a r a c t e r i s t i c s h a v e i n d i c a t e d t h a t s u c c e s s f u l convcyi n q c a n be a c t i i c v e d o n b o t h t r a c k s w i t h c o n v e y i n g v e l o c i t i e s o f 50mm p e r s e c o n d o n t h e o r i e n t i n g t r a c k m d 75rrm p e r s e c o n d o n t h e r e t u r n t r a c k . Further, t h e t r a c k a n g l e s and t h e vi.hration a n g l e have been chosen such t h a t conveying on t h e o r i e n t i n g t r a c k is smooth and t h a t problems a s s o c i a t e d w i t h e r r a t i c p a r t movement t h r o u g h o r i e n t i n g d e v i c e s , a s i s O f t e n e v i d e n t i n v i b r a t o r y b o w l f e e d e r s , are n o t p r e s e n t . Hecause l a r g e b u l k s t o r a g e o f p d r t s i s n o t n e c e s s a r y i t was t h o u g h t t h a t t h i s s y s t e m w o u l d b e q u i t e c a p a b l e of h o l d i n g s u f f i c i e n t p a r t s t o e n s u r e t h a t t h e tine i n t e r v a l b e t w e e n L o a d i n g p a r t s wou: d b e a c c c p t a b l e . 3. 3.1
COMPUTER-A1 DED O R I E N T I N ( ; TPACK IYANUFACTURE Introduction
B e f o r e i n t r o d u c i n o t h e methodoloyy o f o r i e n t i n q t r a c k production usin? i n t e r a c t i v e computer-aided p a r t programming, i t i s n e c e s s a r y to r e v i e w b r i e f l y t h e b a c k g r o u n d of work c a r r i e d o u t j o i n t l y by t h e U n i v e r s i t y o f M a s s a c h u s e t t s a n ? t'ic U n i v e r s i t y o f S o l f o r d o n "Design f o r A systematic classif i c a t i o n technique h a s been develryxd t o h e l p desiqners t o d e t e r m i n e t!ie d e g r e e o f a u t o m a t i o n o f a s s e m h l y w h i c h 1s e c o n o m i c a l f o r B p a r t i c u l a r p r o d u c t a n d t o r e d u c e t h e d i f f i c u l t i e s a n d h e n c e costs o f p a r t s h a n d l i n g and i n s e r t i o n . I t i n t r o d u c e s a method o f y u a n t i f y i n q d e s i q n e f f i c i e n c y f o r a s s e m b l y a n d shown how h i g h a s s e r h l y cost f e a t u r e s c a n b e i 6 e n t i f i e d . To t a c k l e t h c t r a d i t i o n a l l y d i f f i c u l t a r e a of a u t o m a t i c p a r t s f e e d i n u and o r i e n t i n q , a 3 - d i q i t s c o d i n g system. h a s bcen d e v i s e d t o d e s c r i b e t h e p a r t ' s f e e d i n g c h a r a c t e r i s t i c s by s p e c ing its basic shape, b a s i c symmetry a n d i m p o r t a n t ssymetricai f e a t u r e s ( 5 ) . Such a n a n a l y t i c a l approach o r o v i d e s a basis f o r the establishment o f a parts/orientino d e v i c e r e l a t i o n s h i u w h i c h is e s s e n t - i a l t o t h e P r e s e n t work. I n a d d i t i o n , a d c v i c f c o d i n y s y s t e m a s shown i n F i g . 2 has a l s o been developed t o c a t c g o r i s e o r i e n t i n ? d e v i c e s f o r v i b r a t i n g b o w l f e e d e r s (6) a n d t h i s t a k e s t h e f o r m o f a two d i g i t d e v i c e - c o d i n s s y s t e m . The f i r s t d i g i t represents the b a s i c device configuration ( c . y . f l a t or s l o p e d t r a c k ) w h i l s t t h e s e c o n d d i q i t distinguishes the various device modifications (e.g. rr?.il, s l o t , g a p ) . The s y s t e m d o e s n o t g e n e r a t e a u n i q u e c o d e f o r e a c h d e v i c e b u t t h e r e are sets o f e q u a t i o n s which can be uscd t o c a l c u l a t e d e v i c e parameters (e.9. width o f a narrowed t r a c k ) based on t h e i n p u t of c r i t i c a l . p a r t d i m e n s i o n s ( e . g . l e n g t h a n d w i d t h of t h e p a r t ) . The d e v e l o p m e n t o f t h e p a r t a n d d e v i c e c o d e s h a s l e d t o a n o t h e r comprehensive doculrent which relates a p a r t i c u l a r p a r t code t o a aroup o f o r i e n t i n g d e v i c e s w h i c h a r e c a p a b l e of c o l l e c t i v e l y p r e s e n t i n g t h e p a r t a t t h e o u t l e t of t h e system, i n a s i n g l e o r i e n t a t i o n t o p e t h e r w i t h a p r e d i c t i o n of t h e r a t e o f t h e p a r t s . T h i s p r o v i d e s a s y s t e m a t i c way o f a n a l y s i n a f e e d t r a c k desir;n, b u t I t does n o t h e l p to siropllfy feed track p r o d u c t i o n f o r c o n v e n t l o n a l v l b r ~ t o r yb o w l f e e d e r s a n d t h ~ 1s 9 o f t e n a t t m e - c o n s u m l n q a n d h e n c e e u p e n 4 t v c
c,perati.;n. iic).,~evcr, i f r'. l i n e a r v i b r a t o r y o r i e n t i n r : t r a c k , i s to be used, t h e machini.ny oL t h o m j o r f e a t l l r e s of the o r i e n t i n c d c v i c o s on t h e t r a c k from s o l i d m e t a l b,lr becomes p o s s i b l e . I t i s envis:icred t l i r i t such il t a s k c a n b e perforn.ec1 e c w o T i c d l l y 011 a NC m a c h i n i n g c e n t r e i f p a r t p r o f l r a v m n c ccin b c a i d e d by t i l e u s e of a c o n p u t e r . 3.2
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k t t h i s p o i n t i t became a p p a r e n t t h a t b o t h t h c existi n g p a r t s a n d d c v i c e c o d e s werc n-,t s p e c i f i c enouok, t o s e t u p a u n i q u c r e l a t i o n s h i p bctwocn a c i , n p o n e n t p a r t a n d i t s c o r r e s p o n d l n g o r i e n t i n v des,iccs. As g e n e r a l i s s t i o n i s i n e v i t a b l e i n 3ny c o d i n a systerr., t n e same p a r t c o d e may r e f e r t o a number o f p a r t s r o u o f t h e sape s h a p e s a n d f e a t u r e s b u t i i h i c h m i c h t r an e n t i r e l y d i f f e r e n t s e t o f o r i e n t i n < ; d e v i c e s . d e v i c e code, w d s a l s o d e s i g n e d t o c o v e r a qr3up of d e v i c e s w i t h s i m i l a r c h a r a c t e r i s t i c s and h e n c c t h i s also I S b y n o means u n i q u e . H o v e v e r , i n s t e a d o f red e v i s i n g b o t h s y s t e m s to s u i t t h i s a p p l i c a t i o n , i t w a s d e c i d e d t h a t t h e oroblcrr w o u l d b e t a c k l e d b y a d o p t i n g i n t e r a c t i v c p r o n r a i n m i n y a n d by mdkinq u s e o f t h e f e o t u r e s o f p a r t s to i d e n t i f y t h e r e q u i r e d d e x J i c e . Thus, t h e pliysicai ran-rmchine i n t e r f a c e o f t h e system is d e f i n e d : t h e i n p u t o f a p a r t c o d e t h r o u q h a C O T E t o r t e r m i n a l wi.11 p r o m p t t h e s u ? g e s t i o n 3 f o n e o r Tore o r i e n t i n g d e v i c e c o n f i g u r a t i o n s c a p a b l e of o r i . e n t i n u the part. Confirnation of a particular tyoe of device then leads t o f u r t h e r rcqucsts concorninn c r i t i c a l p a r t d l n e n s i ~ se s s e n t i a l t o t h e e f f e c t i v e n e s s o f t h e device. The s y s t e m w i l l f i n a l l y q e n e r , a t c a NC p a r t p r o g r a m t o m a c h i n e t h e r e q u i r e d t r a c k from s o l i d b a r . A major c o n s i d e r a t i o n i n t h e d e s i q r . o f t h e s o f t w a r e a r c h i t e c t u r e is i t s e x p a n d a b i l i t y . I f t h e system is
u s e d t o g e n e r a t e p a r t pr0grarr.s f o r a q r o w i n u number of o r i e n t i n g t r a c k s , t h e v a r i c t y o f o r i e n t i n g d e v i c e i s l i k e l y t o i n c r e a s e a n d t h e s i z e o f t h e NC p r o g r a m g e n e r a t o r wi II s o o n e r or l a t o r e x c e e d t h e r e m o r y l i m i t lmposed by t h c o p c r a t i n o s y s t e m . R l t h o u a h u n d e r most o p e r a t i n g s y s t e c s u s e r ?rocirons c a n b c c h a i n e d tocjether, t h e need to r e c o r d c u r r e n t v a r i a b l e s b e f o r e chaining and t h e i r r e t r i e v a l t h e r e a f t e r is o f t e n t e d i o u s 2 n d t i m e c o n s u m i n g . An a l t e r n a t i v e i s t o adopt a s t r u c t u r e d approach such t h a t t h e e n t i r e o r i e n t i n q t r a c k i s c o n s i d e r e d t c be comuosed o f J. series of d c v i c c s , e a c h having its oyn i n d e p e n d e n t r o u t i n e f o r devi. ce qeorne t ry c a 1 c u 1 a t i on . 'I'hc?sc r o u t i n e s c a n be s t o r e d s e p a r a t e l y from t h c mrist.cr p r o g r a m g e n e r a t o r w h i c h i s r e s p o n s i b l e mainly- f o r t h e r o u g h i n g o p e r a t i o n s and f o r w r i t i n q p a r t programs block information onto t h e output f i l e . Thus, a p a r t i c u l a r d e v i c e r o u t i n e i s ' p u l l e d - i n ' and c o ~ p i l e d w i t h t h e master p r o g r a r . a e n e r a t o r o n l y when t h e d e v i c e i t r e p r e s e n t s .is r e q u i r e d f o r a p a r t i c u l a r o r i c n t i n q track. A l t h o u q h i t n e e d s more t i n e t o r u n a n unc o m p i l e d p r o g r a m , i t i s b e l i e v e d t h a t s u c h a r.odular approach w i l l minimise d a t a h a n d l i n y r e q u i r e m e n t s and h e n c e p r o g r a m r u n timc. One of t h e l i m i t a t i o n s i n u s i n ? a m a c h i n i n g c e n t r e f o r o r i e n t i n g device production is t h e diffj.c:ilty o f u t i . l i s i n g sm.all c u t t i n g t o o l s ( e n d r i l l s o r s l o t d r i l l s ) t o machine d e v i c e d e t j i l s which a r e c l o s e d to t h e i n n e r a p e x of t h e 1,-shape t r a c k . Small cutters are u s u a l l y s h o r t ( c u t t e r e d a e a n d s h a n k ) , and a n y c o l l i s i o n b e t w e c n t h e c h u c k of t h e tool h o l d e r a n d t h e w o r k p i e c e i s c l e a r l y u n a c c e p t a b l e . For example, a w i p e r b l a d e p r o j e c t e d f r o m t h e wall o f a f e e d t r a c k c a n e a s i l y b e m a c h i n e d f r o m a s o l i d lorn s q u a r e b a r as l o n u a s t h e r e i s a r e a s o n a b l e g a p s i z e between t h e blade and t h e s u r f a c e o f t h e t r a c k . Aovever, i f t h c dcvice r e q u i r e s to b e desiqned such t h a t t h e gap s i z c is small, a s m a L l diameter slot d r i l l of s u f f i c i e n t l e n g t h would b c i m p r a c t i c a l . Similarly, orienting device such a s s i l h o u e t t e s and s c a l l o p s u s u a l l y have a n i n f i n i t e v a r i e t y o f p r o f i l e s which c a n n o t b e r e a d i l y s t a n d a r d i s e d and t h e s e also nay r e q u i r e s m a l l and a c c u r a t e f e a t u r e s s u c h as s h a r p a c u t e c o r n e r s which are too d e t a i l e d t o b e p r o d u c e d by t h e s m a l l e s t o f s l o t d r i l l s . T h u s , a s i n g l e NC m a c h i n i n g c c n t r e i s n o t c a p a b l e of p r o d u c i n g many e n t i r e o r i e n t i n g t r a c k s d e s p i t e its v e r s a t i l i t y . I t was d e c i d e d , t h e r e f o r e , t h a t s t a n d a r d i n s e r t s such as wall proj e c t i o n s and s c a l l o p s would b e added t o c o n t r o l l e d reccsses p r o p e r l y m a c h i n e d o n t h e o r i e n t i n r r t r a c k a f t e r t h e l a t t e r !]as b e e n c o m p l e t e d . These i n s e r t s have b e e n s t a n d a r d i s e d a s f a r as i s p r a c t i c a b l e a n d t h e c o r r e c t p o s i t i o n i n a on t h e o r i e n t i n g t r a c k i s a c h i e v e d by m a c h i n i n < : a - J p r o p r i a t e l o c a t i o n s usincr t h e machininq- c e n t r e . 9efore software implementation c o u l d be a c h i e v e d i t x a s n e c e s s a r y t o s e l e c t t h e c u t t i n g t o o l s to be used. Even w i t h t h e geomct.ri a device well-defined, tho tool path t h a t will g e n e r a t e t h e r e q u i r e d p r o f i !e w i l l v a r y d c c o r d i n g t o t h e t y p e and t h e s i z e of c u t t e r u s e d . 'Thus, a f r e e c h o i c e a p p r o a c h t o t o o l s e l e c t i o n would h a v e c o r p l i cated t h e s o f t w a r e u n n e c e s s a r i l y w h i l s t c o n v c r s c ? l y , i f
ttle s o f t v n r o h.34 k e n t o o r i q i d l y s t r u c t u r e d , il t t e r s o f s p e c l f i c si z c s -xnu;c'. h c i s ,would lie linsccepta!>lt?. I t wi~s c o m p r a n i s e j i o , ~ l dhc
e fixed f o r t h e rOutir.c, d i f f e r e n t sri t h i n t h e ranc;e i i o u l d be c!:mpennated :-sin<. t h i s SyStCT, f 9 r ]q t h e u s e 3f t o o l o f f s e t s . too i s & r e s e l e c t e d f r o m 3 tr,ol l i b r a r y a c c o r d i n g 20 t h e t;:o1 d e s c r i p t i o n and t h e r a n q f of t.o.31 climeters deiined
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system 1r.plcmentation
3.3
3.3.1 :lardware C o n f i c f u r i t i o n ~5~ ? h i l o s o p h y o f a p p l y i n g c o m p u t e r - a l d e d z a n u f a c t u r i n q t e c h n i q u e s t o o r i e n t i z q t r a c k p r o d c c t i o n -was iPTle?lc".t e d u s i n g 3 K e a r n e y a n d n r e c k e r H.NS-l.jO0 SC m c h i n i n ? centre. The s o f t w a r e was w r i t t e n i n B a s i c - P l u s r u n n i n g ,dndcr RSTS/C I?.ounted c n a SYSTTXE SERIES 6 4 0 0 [IXC ~ n P 1 1 / 3 4P r o c e s s o r ) .
-
The tiblc 1 5 0 0 i s a -2-axis n u m e r i c a l l y c o n t r o l l e d , h o r i z o n t a l s p i n d l e r a c h i n i n q centre h a v i n a 3 l i n e a r a x i s (X, Y , Z) a n d a r o t a r y a x i s m o t i o n s , w i t h a 30 All. axes t7ol magazine randor, s e l e c t i o n tooi. changer. C ~ T :be commanded t o move i n e i t h e r a b s o l u t e or i n c r e m e n t a l mode a t c o n t r o l l e d f e e d r a t e s u s i n < ? t h e >"i I w a u k e e - h t i c w o r d - a d d r e s s p r o r r r a n w i n n f o r m a t . The maximum t r a v e l o f t h e m a c h i n e i n t h e X, Y , Z a x e s dre 1500m., l O O 0 m n m d jOOmn r e s p e c t i v e l y .
As t h e w o r k p i e c e s are s t a n d a r d r c i l d s t e e l b a r a p p r o x i T a t e l y 40nm s q u a r e a n d 800m l o n g , i t was d e c i d e d t h a t t h c o n l y p r a c t i c a l way of mkichining t h e s e w o u l d b e bjF m o u n t i n g t h e n on a f i x t u r e which i s a t t a c h e d to an a n g l e p l a t e v h i c h i n t a r n sits on t h e r o t a r y table (k'ig.3) . w i t ! > t h e l o n g a x i s o f t h e b a r p a r a l l e l t o t h e \' a x i s o f t h c m a c h i n e . By r o t a t i n ? t h e t a b l e 2 9 0 d e g r e e s c i t h c r l e f t or t h e r i g h t h a n d t r a c k s c a n bc machined w i t h t h e r e q u i r e d t r a c k a n c l e ( p o s i t i v e O r nqative) The f i x t u r e c o n s i s t s 0 5 four v e e - b l o c k s , two f i x e d a n d t w o movable, l o c a t e d b y d o s r e l p i n s o n T!ie t w o r;.ovablc v e c s ? r o v i d e ii g r o u n d b a c k p l a t e . a d c q u a t c s u p p o r t a t t h e mid-span o f t h e t r a c k a n d t h e i r p o s i t i o n s c a n b e a d j u s t e d t o allow t h r o u o h h o l e s t.o be m a c h i n e d a t v a r i o u s p o i n t s o n t h e t r a c k .
.
3 . 3.2
D.itabase
In o r d e r t o allow f o r e a s y c h a n q e s o f t h e i n p u t i n f o r n a t i o n , n o t a b l y t h e g e o m e t r y a n d c o n p o s i t i o n of t h e f e e 6 t r a c k , t h e s i z e s o f t h e c u t t i n g tools, and t h e c o n d i t i o n s o f c u t t i n g , t h e concept o f d a t a independency has been adopted i n t h e design o f t h e software. 0 p e r a t j . n g p a r a m e t e r s a r e s e p a r a t e d f r o m t!ic a p p l i c a t i o n p r o g r a m a n d a r e s t o r e d i n d i f f c r e n t f i l e s f o r m i n q t.hc datdba.5f o f t h e s y s t e m (Fip.4). ? h e r e a r e t h r e e i n p u t d a t a f i l e s , t h e s e are:
il) The T r a c k S t r u c t u r e F i l e ; t h i s r e c o r d s t h e s t r u c t u r e of a feed t r a c k desifled to o r i e n t a s g e c i f i c component. Each r e c o r d i s made up o f t h e p a r t c o d e o f t h e c o m p o n c n t , a record n u n b e r ( u s e d to i d e n t i f y d i f f e r e n t t r a c k s u s e d by t h e same p a r t c o d e ) , 2nd a maximum o f 1 2 d e v i c e s . Data is s t o r e d u s i n g B a s i c - P l u s ' s R e c o r d 11'0 f i l i n g f a c i l i t y a n d c a n b e u p d a t e d and r e t r i e v e d randomly. Althouuh t h e r c is n o pictorial aid to t h e operator during t h e d a t a e n t r y s t a g e , t h e s y s t e m p r o v i d e s sone r - e a s u r e s t o c h e c k t h e v a l i d i t y o n t h e p h y s i c a l r e l a t i o n s h i p b e t w e e n two c o n s e c u t i v e d e v i c e s ( e . 9 . a h a l f n r e s s u r e b r e a k nrust he c u t p r i o r t o a r a i l ) . ( 2 ) The T o o l L i b r a r y ; t h e t o o l l i b r a r y r e c o r d s i n f o r m a t i o n o f t h e a v a i l a b l e tools which i n c l u d e :
.
. . . .
t h e t o o l c o d e ( e . a . T@@2@@) t h e tool d e s c r i p t i o n ( e . 9 . l o n o s e r i e s 3 f l u t e slot cutter) t h e diameter and l e n g t h o f t h e t o o l t h e s p i n d l e s p e e d a n d s p i n d l e code ( f o r m i l d s t e e l ) and t h e feed rates ( t r a v e r s i n g and s i n k i n c ) .
T h s s y s t e m a l s o c h e c k s t h e v a l i d i t y o f t h e worda d d r e s s f o r m a t s t o b e used b y t h e ? a r t proqram. (3) The C u t t i n g P a r a m e t e r F i l e ; t h i s c o n t a i n s d a t a r e l o t i n g t o t!ic b a s i c d i m e n s i o n s of t h e t r a c k ( e . g . thickness o f w a l l and base, angles of i n c l i n a t i o n o f p o s i t i v e and n e g a t i v e t r a c k s , and l e n g t h s o f o r i e n t i n g d e v i c e s ) , and t o t h e operatinq- c o n d i t i o n s o f t h e m a c h i n e ( c . g . p o s i t i o n o f f i x t u r e , z e r o r e f e r e n c e s of t h e JXCS e t c ) A l i o f t h e s t o r e d i n f o r r a t i o n h a s to tic r e a d i n t o t h e p r o u r a m u e n e r a t o r b e f o r e i t c a n b e properly run.
.
401
3. 3 . 3
I':irt I ' r ~ q r d r . Generator
d n d a b i i i t y of t h c s o f t w a r e , t h e a t o r i s di.;ided i n t o t h r c c p a r t s : r, t h e m : i s t e r p r o r r a m y r n c r d t o r a n d tke device f i l e .
(1) X o n i t o r ; t h i s i s a f r o n t p r o c e s i n g proyrorr. x h i ch upon t h c i n p u t o f a p a r t c o d e , s c a r c es d e v i c e r o u t i n e s frcm t h e D e v i c e r i l e f o r t h c r c q u i r c p r t o r i c n t a t i o x a n d i n s e r t s t h e r e l e v d n t S t a t e I r e n t s i n t o t h c >!aster Procjrom G c n c r a t ( i r t o r i c n r r o t e a neil B a s i c o r o g r n m . I t t h e n " c h a i n s " i t s e l f t,o the l a t t e r w h i c h is t cun:pi.led a n d r u n . R e l c v a n t Lnfor1::ation o n tile f t r a c k s t r u c t u r c i s r i l s r j p a s s c d t o t h e new p r o g r a r r through t h e syst c m ' s facl l i t y . ( 2 ) Master P r o g r a m G e n e r a t o r : t h i s i s p a r t o f ti:c P a r t Program G e n e r a t o r and i s s t o r e d i n i t s secjUentia.1 t e x t f o r m ( i . e . n o t a B a s i c p r o q r a r ; . ) . Cpon b e i n g a c c c s s c d by t h e ' M o n i t o r ' , r o u t i n e s t a t c m e n t s r e l e v a n t t o a n o r i e n t i n g & v i c e a r e i n s e r t e d i n t o t h c rndster o r o g r a m t o c o n v e r t i t i n t o a complete 3 a s j . c p r o g r m t h a t w i l l prudu:e t h e r e q u i r e d NC t a p f . 'The ? a s t e r p r c c r a m G c n c r a t o r c o n s i s t s m a i n l y of :our p n r t s a n d t h c s c are:
( a ) R o u g h i n g r o u t i n e s : - A s t'nc l e v c l o f t n c t r a c k s u r f a c e may chancre c o n s i d e r a b l y r h r o u q h o u t t h e e n t i r e t r a c k l e n g t h , t h e f i r s t t a s k t h e g e n e r a t o r h a s to p e r f o r m i s to a n a l y s e t h e s t r u c t u r e o f t h e f e c d t r a c k so t h a t t h e maximum t r a c k t h i c k n e s s ( a t i t s s t a r t i n g p o s i n t ) may be c a i c u l a t c d . The program t h e n c a i c u l a t c s t h e c x t r e d t i e s o f tool. l o c a t i o n s usi.ng t h e g e o m e t r y t r a n s f o r m a t i o n r o u t i n c , s c l e c t s t h c a p p r o p r i a t e tooli n g u s i n g t h e tool s e l e c t i o n r o u t i n e a n d p r i n t s t h o p a r t p r o g r a r . ( b l o c k 1.: block) f o r roughing o n t o t h e output f i l e using standard p r i n t routines. 'The t r a c k . s u r f a c e t h u s o b t a i n e d is t h e n n e m r i s e d a s t h c rc f e r e n c e s u r f ace f o r s u b s e q u e n t d e v i c e - b y - d e v i c e cuttiny operations. ( b ) Gcomctry T r a n s f o r m a t i o n Routine:- T h i s s t a n d a r d r o u t i n e is w r i t t e n t o t r a n s f o r m r c f c r r n c c p o i n t s d e f i n e d o n t h e c r o s s - s e c t i o n o f t h e t r a c k to i t s c o r r e s p o n d i n g X-2 m a c h i n e c o - o r d i n a t e s , w i t h t h e o r i g i n t a k e n a t t h e c e n t r e of t h e r o t a r y t a b l e . If t 5 c d i r e r : t i o n o f c u t t i n g i.s p a r a l l e l t o t h e Y- a x i s eovemcnt, t h e program a I s 0 a t t c n l p t s t o e v a l u a t e t h e e x t r e m c tool l o c i t i o n s i n t h c x a n d Z a x c s so t h a t t h e number of p o s s e s , t h e l e n g t h o f trar.c?ls, a n d s o m e t i m e s , t h e p c r m i s s i b l c r a n g e o f t o o l diarncter ( t o s u i t t h e d c s i g n t o o 1 p a t h ) c a n be c a l c u l a t e d .
4.2 A t P r e s e n t about 2 0 devicc r o u t i n c has bccn I n y e n e r a l t h e y are c a p a b l e o f w r i t t c n and p r o v e d . ( J r i c n t i n q the dcsiqnc?tl p a r t s t h o u c h m i n o r m o d i f i c a t i o n s t o SOT- :!r.u.i(:e p a r a n c t c r c q u o t i o n s may b e n e c e s s a r y . 4.3 ?'he p r e s e n t x o r i w i l l be e x t e n d e d t o c o v e r n o r e d e v i c e s ancl t o ilsc a sr.:a:ler SC m a c h j n e t o p r o d u c e c r i t i c a l s m a l i d e t a i l s on i n s e r t s .
4.3. The d e c i s i o n t u p r o d u c e Z r i e n t i n q t r a c k s f r o m m i l d s t c e l was p c r h a p s unwise. >!!achinina t i r r e s a r e I o n u Find t h e t r a c k s arc heavy. I t is t h o c c h t t h a t f i i t u r e trLicl:s w i 1 . l b c m a n u f a c t u r e d f r o m an a l u m i n i u m .>llo;. a n d i t w i l l he a c c e p t e d t h a t t r a c k s w i l l n o t !If a s r e s i s t a n t t o wear a s m i l d s t e e l o n e s .
REFEREXCES i.
R e d f o r d , A . H . , L o , E . K . a n d K i l l c c n , P. J . , " P a r t s F e e d e r C o s t R n a l y s i s f o r hlul t i - P a r t H o b o t i c A s s e m b l y " l5TH CIRP 1n t c r n a t i o n a l S c n i n a r o n M a n u f a c t u r i n n S y s t e x s . A m h e r s t , Mass. June 1983.
2.
Suzuki, '1'. a n d Xohno, M., "The F l e x i b l e P a r t s F e e d e r w h i c h h e l p s a r o b o t asscrhlc a u t o n a t i c a l l y " Assembly A u t o m a t i a n , Feb. 1981.
3.
R e d f o r d , A. H . a n d C r o s s l e y , T. R . , " D e s i g n F o r R o b o t i c Assembly P r o g r e s s Keport" P r o c e e d i n g s o f the SERC Ro!mtic I n i t i a t i v e G r a n t e e s C o n f e r e n c e , I3irmingham, S e p t . , 1 9 8 2 .
1.
S w i f t , R. G. ancl R e d f o r d , A. I I . , " P r o d u c t D e s i g n f o r Automatic Asse&ly" P r o c e c d i n y s o f t h e 2nd I n t e r n a t i o n a l C o n f c r c n c c on Assembly A u t o m a t i o n , D r i y h t o n , Mdy 1981.
5.
" D c s i g n f o r A s s c m b l y Handbook" P u b l i s h e d b y S a l f o r d tinivcrsit.y I n d u s t r i a l Centre L t d . , S a l f o r d , Enqland, O c t . 1982.
6.
"IlandLook o f F e e d i n g a n d O r i e n t i n g T c c h n i q u e s f o r S m a l l P a r t s " P u b l i s h c d by U n i v e r s i t y o f M a s s a c h u s e t t s , A n h e r s t , X a s s a c h u s e t t s , 1976.
REQUIREMENTS OF A MULTI_ _ _ i l _ -
(c) T o o l S c l e c t i o n R o u t i n e : iu'ith s n c c i f i c a t i o n s o n t o o l d e s c r i p t i o n ancl t o o l c l i a r e t c r , t h i s r o u t i n c : s e l e c t s t h e a p p r o p r i a t e t o o l f r o m t h e l i b r a r y . The r e i c v a n t tool c o d e , s p i n d l e c o d e , d i a m e t o r and i c e d rates a r e r e t u r n e d t o t h e P a r t Program G e n e r a t o r . (d) Printing Routines:N C p a r t programming b l u c k s are w r i t t e n o n t o a n o u t n u t f i l e d c s i g n a t c d on a s p c c i f i c c h a n n e l by a n u n b c r of s t - a n d a r d p r i n t i n g routincs. The i d e a of s t r u c t u r e d p r o q r a m m i n g i s a d o p t e d silctl t h a t e a c h r o u t i n e is o n l y r e s p o n s i b l e f o r t h e h a n d l i n g of a s p e c i f i c c u t t i n g o p e r a t i o n . The r o u t i n e s i n c l u d e :
. . . . . . . . .
.
s e q u c n c c number c o u n t . i n q tool s c l c c t i n g a n d c h a n g i n g rotary table turning i n i t i a l tool approachin: coolant control r o u g h i n g w i t h tool compensation linear a n d c i r c u l a r c o n t o u r i n g d r i l l i n ? and tappinn opti.ona1 s t o p p i n g e n d of program p r o c e s s i n g
Device F i l e
(3)
This device-dependcnt t e x t f i l c contains b a s i c p r o g r a m i n g s t a t e m e n t s t h a t are i n s e r t e d i n t o t h e Master P r o g r a m G e n e r a t o r when t h e d e v i c e is c a l l e d for. Each d c v i c c r o u t i n e , upon e x e c u t i o n , w i l l r e q u e s t p a r t s geometry i n p u t r e l e v a n t t o t h a t d e v i c c , c o n v e r t i t t o d e v i c e p a r a m e t c r s , and c a l c u l a t c t h e r e l a t e d c o - o r d i n a t e s on t h e w o r k p i e c e f o r p a r t program o u t p u t . 3.3.4
systcm Output
The s y s t c n o u t p u t s f o u r d o c u n e n t s ; a n :IC p a r t p r o g r a m punched t a p e , a f o r m a t t e d p a r t procram l i s t i n q , a n o p e r a t i n g i n s t r u c t i o n , and t h c tool l i s t . 4.
COWCLUSTOXS A X D FLJHTHER WORK
4.1 The p h i l o s o p h y o f a p p l y i n g c o m p u t e r - a i d e d m a n u f a c t u r i n g t o f e e d t r a c k m a n u f a c t u r e i s implcmcnted. NC t o p e s o u t p u t f r o m t h e s y s t c m h a v c b e e n t e s t e d a n d used t o c u t mild steel workpiece ( F i q . 5 ) . The a v e r a g e c u t t i n g t i m e p e r t r a c k is f i v e h o u r s .
402
ARM ROBOT FEEDER
Compact
Compact
R e l a t 1 ve 1y c v p e n s 1 vc
Inexpensive
Long F e e d t r a c k
s h o r t Feed t r a c k
L a r g e b ~ l ks t o r a y e
S m a l l hulk storage
l l l y h reed r a t e
Low F e e d r a t e
1
u p c n s i v e t o Re-tool
A b i l i t y to o r i c n t a w i d e v a r e i t y of p a r t s
T n e x p c n s i v c t o Re-tool A b i l i t y t o o r i e n t a wide v a r i e t y of p a r t s .
TABLE 1
.
Fig.1
Linear Parts Feeder
Fig.2
Fig.3 Hardware Configuration
Coding System for Orienting Devices SECOND C Wide Track
0
Narrowed Track
1
Slot or groove
2
Inserts
3
Flat Tracl
cn U
403
PROGRAM GENERATOR
PROGRAM
.._..
-Fin - w -4-
Inform;ation Flow in the Computer- Aided Feed Track Manufacturing System
Fig. 5
404
FEED TRACK
Selection of Feed Tracks
I
7
Of t h e pan:, m t h o d s o f o r i e n t i n o a n d p r e s e n t i n g ? a r ~ b l yn a c h i n e s , t h e 7,:ibrz:qry i s b y f a r t h e rmst cfxmm d e v i c e b e c a u s e o f i t s l a r z g e c a y ; a c i t y , n i g h r a t e of c o n p a c t s t r u c t u r e a n d a b i l i t j ' t o d e a l wit!: a wide a r t sl.;ipes. ' : h C o r t u n a t e :y are r e l a t i v e l y e x p e n s i v e b o t h i n terms of c a u i n r c n nd changeover costs, e s p e c i i s i n t e r j r a t e d i n a n u l t i - a r n r o b o t i c a s s e r h 1 . y syst t d t i l i s i t i o n i s 1oi.i inci f r e q u i p r e n t s c h a n g e o v e r s a r e n e c e s s a r y d u e t o t h e recyui r c n c r t t o assemJj1.e d i f f e r c n sliown t l i l t i t i n t h e 4 i s p r a 1 1 c r t i a n a t e l v h i g h m s t c,f t5e fee(l:nq e q t i i r m e f i t , r : i makes r o b o t i c a s s e r ? b l y s y s t e m s d i f f i c u ; t t o j u s t i f y e c o n o m : c a l l y a n d t h c r costs a s s o c i a t e d w i t h t h i s e q u i p m e n t c o n s i d e r a b l y . A l i n e a r v i b r a t o r y f e e m b l y c q u i p m e n t i s c u r r e n t l y b e i n q d e v e l o p e d a t t h e I n i v e r s i t : , n f s.:..!forc?. T t i s a n t ? c:p a t c d t h a t t h c u s c o f r u l t i p l c L i n e d r f e e d t r a c k s n o u n t e d on a common d r i v e i i i i l n o t o n l y r c d u c c t h c c a p i t a l c o s t o f t h e e q u i n m e a t p e r track. a n d t h e chan5:ecY:er c o s t s b u t alsc t h z t o f t h e r i r i e n t i r q c:e.ilce p r o d u c t i o n s i n c c s i r n p l e s t r a i q h t f e e d t r a c 2 s x i l l be p r c d u c e d o n a n :?C m a c h i n i n ? c e n t r e u s i n g i s t e r a c t i v e computer-aide6 p a r t prooramninq. 'This n a p e r d e s c r i b e s t h e p h i l o s o p l i y 3 : t h e d ? y r o a c h , t h e d e s i r n , C o n s t r u c t i o n a n d t e s t i n q o f t h e b a s i c f e e d e r and t h e n a r t ? r n q r m F i n q nct.hods f n r s i n p l e : , r j c n t i n ? s y s terns. LUC
1.1
TO A MULTI-ARZ' ASSEW3LY RORO?
Introduction ~
Of t h e v a r i o u s t y y s of a u t o r r . a t i c a s s e m b l y , mu1ti.-arm r o b o t i c assembly n i f f c r s from a l l o t h e r forms i n t h a t a s s e m b l y i s c a r r i e d o g t i n s e r i e s r d t h e r t h a n i n pm-al l e l , i . e . f o r a l l f o r n s o f l i n e asserbly w h e t h e r i t . u s e s d e d i c a t e d workheads or s i n n l c a r n r o b o t i c d e v i c e s , a p r o d u c t i s assembled e v e r y r a c h i n e c y c l e i r h e r e a s i n multi-arm robotic assembly, a p r o d u c t is o n l y dsscmblcd a f t c r a number o f c y c l c s a n d t h i s is d e t e r r r . i n c d by t h e number o f a r m s and t h e n u v b e r of D a r t s i n t h c product. T h u s , f o r m u l t i - a r m r o b o t i c assemilly t h e n e c e s s a r y r a t e o f s u p p l y o f p a r t s is g e n e r a l l y v e r y much l e s s t h a n t h a t w h i c h a u t o m a t i c f c e d i n c d e v i c e s a r e c a p a b l e of s u p p l y i n ? a n d t h i s results i n i n c f f i c i e n t u s e o f t h e f e e d i n g d e v i c e s and a c o n s c q u c n t i a l i n c r e a s e i n t h e f e c d i n u cost o f e a c h p a r t d e l i v e r e d . F u r t h e r , t r a d i t i o n a l a u t o r a t i c p a r t s f e e d i n g and o r i e n t a t i o n i s c a r r i e d o u t by a f e e d i n g d e v i c e which i s c o n f i q u r e d t o m e e t t h e r e q u i r e m e n t s of d p a r t i c u l a r or, a t t h e most, a very r e s t r i c t e d ranqc of p a r t types. '",. L . ~ U S , althouc!h d e d i c a t e d f e e d e r s c a u s e f e w p r o b l c v s i n h a r d a u t o m a t i o n where p r o d u c t i o n r u n s a r e v e r y l o n q , c h a n a e s i n p r o d u c t d e s i q n arc rare a n d .where p r o d u c t i o n r a t e s a r c h i g h , t h e y are u s u a l l y too i n f l e x i b l e f o r r o b o t i c a s s e m b l y w h i c h h a s t o c o p e w i t h d rilnne o f product s t y l e s manufactured in r c l a t j v c l y snali b a t c h e s a t low speed.
o u t ( 1 ) t o e x a m i n e tl:e c o s t o f p a r t s f e e d i n q t o series assembly robotic d c v i ces u s i n g a v a r i e t y o f e x i s t i n g a n d h y p o t h e t i c a l f e c d i n q systems.
A r e c e n t s t u d y has been c a r r i e d
1.2
Feedinq Systems Considered
1). D e d i c a t e d f e e d c r s .
Levcl b o w l f e e d e r w h i c h i s c a p a b l e o f d c l i v c r i n q y s r t s s i n o l y b u t not i n o r i e n t a t i o n , a set o f p a r t s r e v e r s i n ? u n i t s , a movinc- s o l i d s t a t e c l n e r a and t h e a s s o c i a t e d image p r o c c s s i n q e q u i p m e n t . P a r t s are f e d i n t o t!:e r e v c r s i - n g u n i t s s c a n n e d by t h e c a r e r a a n d ej t h e r a c c c p t e d o r r f v e r s c d and r e - s c a n n e d . Pdrts i n ii l i m i t e d n u r b e r o f o r i e n t a t i o n s a r e t h e n p i c k e d u: by t.hc r o h o t a n d t u r n e c i i n t o t h e r e q u i r e d o r i e n t a tion. B e c a u s e t!ie b o w l s do n o t n e e d t o b e c o n f i g u r e d to p e r f o r r r p a r t s o r i e n t i n ? , t h e y :Ire e a s i l y a d a p t e d to accommodate d i f f e r e n t p a r t t y p e s b u t t h e r a n o f o f o a r t s h a p e s c a p d l ~ l eo f beint! d k d b y t h i s t y p e of s y s t e m is l i m i t e d . 5!
Xu1 t i - p n r t
feeder
T!w m u l t i - p a r t f e e d e r i s a n o n - s t a n d a r d f e e d l n q y s t e m desiiined t o f e e d and o r i e n t s e v e r a l p a r t s f o r r e s e n t a t i o n t o a robot u s i n ? m u l t i p l e t r a c k s b u t a cocimon d r i v e u n i t ( 3 ) . Tn t h e s t u d y i t i i a s a s s u n e d t h a t t h e f e e d e r w o u l d b c c a p a b l e o f handlinr: two di f f c r c n t p i r t t y p e s . fi}
!+iq;izine s y s t e m s
Bec2usc a u t o m a t i c f e e d i n g s y s t e m s f o r r o b o t i c assembly c: a t w e l l b e l o r maxin?um r a t c , i t a d v a n t a a e c o u l d be g a i n e d b y ny d u t o m a t i c p a r t s f c c d e r s worknd t h e n t r a n s f e r r i n a t h e p a g a z i n c s t c l t!ie r o b o t a s s e m b l y p o i n t s . A l t h o u g h t h e macjdzines w o u l d L e e x p e n s i v e t h i s t.ype of s y s t e m h a s t h e f u r t h e r a d v a n t a q e o f p r o v i d i n g a n i n s p e c t i o n f u n c t i o n 2 n d also d e - c o u p i i n p the i n s e r t i o n o p e r a t i o n f r o m t h e h a n d l i n g operation. I n t h e s t u d y , magazines l o a d e d by d e d i c i i t e d f c e d e r s , proprsmmable f e e d e r s and m u l t i - p a r t f e e d e r s w e r e a11 considered. Tn a d d i t i o n t o t h e a b o v e , two f u r t h e r m a q a z i n c f e e d i n g s y s t e m s were e x a m i n e d , m a n u a l l o a d i n ? o f r a g a z i n c s a n d m a q a z i n e s l o a d e d a t t h e p o i n t of p i e c e p a r t m a n u f a c t u r e
T h i s s y s t c r . *would c o n s i s t , t y p i c a l l y , o f v i b r a t o r y b o ~ l f e c d e r s each o f w h i c h w o u l d u s e d e d i c a t e d b o w l s , 7) 3anual fecdinq o r i e n t i n q d e v i c e s and a n c i l l i a r y cquipeent f o r each ks a r c f e r c n c e f o r c o r r p a r i n q t h e v a r i o u s f e e d i n r r s y s p a r t t y p e . ' G I U S , t h e number o f b o w l s n e c e s s a r y f o r a t e m , m a n u a l l o a d i n q of a s s c m b l y r o b o t s w a s analysecl p l a n n e d v a r i e t y o f p r o d u c t s w i l l be e q u a l t o t h e numxhere an o p e r a t o r w o u l d l o a d p a r t s i n t o f e e d t r a c k s h e r o f d i s t i n c t p a r t types w h i l s t t h e nurber of d r l v e i n s u i t a b l e l o c a t i o n s i n t h e r o b o t ' s iiork a r e a . u n i t s n e e d e d w i l l be e q u a l t o t h e masimun, number of p a r t s i n any s t y l e of t h e p r o d u c t . 1 . 3 Cost o f Feedin2 2).
Programmable f e e d e r s
A p r o g r a m m a b l e f e e d e r is c o n s i d e r e d t o be o n e w h i c h
by t h e use of s u i t a b l e a u t o m a t i c a l l y a d j u s t a b l e t o o l i n g i s versatile enouqh to f e e d and o r i e n t a wide v a r i e t y of p a r t s , i n d e p e n d e n t o f t h e i r s h a p e , s i z e e t c . T h u s , t h e number o f feeders r e q u i r e d w i l l b e e q u a l t o t h e maximum nu?rber of p a r t . t y p e s f o r a n y o f t h e p r o d u c t s t y l e s and c h a n q e o v e r t i n e f o r t h e f e e d e r w i l l be s e n s i b l y zero a l t h o u c h t h e t i n e t a k e n t o n d j u s t o r change a n c i l l i a r y equipment w i l l s t i l l n e e d to be taken i n t o account. 3)
D e d i c a t e d f e e d e r s s e r v i n g more t h a n one r o b o t .
As m e n t i o n e d p r e v i o u s l y , d f d i c a t c d f c e d e r s a r e u n d e r -
u t i l i s e d when u s e d i n r o b o t i c a s s e m b l y a p p l i c a t i o n s a n d i t w c s t h o u y h t t h a t d e d i c a t e d f e e d e r s s e r v i n c more t h a n o n e robot w o u l d r e s u l t i n more e f f c c t i v e u s e o f t h e feeders. C l e a r l y , t h i s t y ? e of s y s t c m w o u l d o n l y be p r a c t i c a l i f a number o f m u l t i - a r m r o b o t s w e r e b e i n n used i n rlosc p r o x i m i t y . 4)
F e e d e r s w i t h s i m p l e computcr v i s i o n
The v i s i o n s y s t e r ? c o n s i d e r e d was m o d e l l e d o n e q u i p m e n t d e v e l o p e d b y H I t a c h i (2) w h i c h c o n s i s t s o f n mi11 t i -
Annals of the ClRP Vol. 32/1/1983
G e n e r a l l y , t h e c o s t o f f e e d i n g p a r t s c o n s i s t s o f two e l e r r e n t s : d i r e c t l a b o u r costs and d e n r e c i a t i o n o f c a p i t a l equipment. The f o r m e r c a n b e c l a s s i f i e d i n t o m a t e r i a l h a n d l i n g cost, s y s t e r t e n d i n q cost, f a u l t c o r r e c t i o n cost a n d c h a n p e o v e r c o s t . T h e l a t t e r c a n h e c l a s s i f i e d as b a s i c e y u i p x e n t d e p r e c i a t i o n a n d toolin? depreciation and t h e values assigned to these w i 1 1 d c p e n d o n w h e t h e r t h e f e c d c r s o r p a r t s of f e e d e r s , a r c e x c l u s i v e t o t h e f e e d i n ? o f a : > a r t i c u l a r ?art o r w h e t h e r t h e y are q e n e r a l f o r a l l o p e r a t i o n s . 1.4
Xesults
The a l p r i t h n i s d e v e l o p e d f o r d e t e r m i n i n g p a r t s f e e d i n g costs were t e s t e d u s i n a two d i f f c r e n t p r o d u c t f a r r i l i e s W i t h t h e same sets o f c o s t a n d t i r e d a t a f o r t h e :'drious t y p e s of f e e d j n q e q u i p m e n t . Both f a m i l i e s c o n s i s t e d of t e n d i f f e r e n t p r o d u c t s c a c h c o n s i s t i n a o f n parts. For o n e p r o d u c t f a m i l y s i x t y - s i x d i f f c r e n t r t s were u s e d w h i l s t f o r t h e o t h e r o n l y t w e n t y f f e r e n t p a r t s were u s e d . T o t - a 1 demand f o r e a c h p r o d u c t w a s t h e same ( 2 0 0 , 0 0 0 p r o d u c t s ) and f o r s i m p l i c i t y i t WAS a s s u m e d that I)atcli s p l i t t i n r j w o u l d he of equal batch s i z e s whatever t h e s i z e of t h e batch. Tile s m a l l e s t . b a t c h s i z e w a s f i f t y :->roductsw h i l s t thc ! a r q e s t YRS 1 3 5 0 and tor both s t u d i e s i t X R S
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2) F 3 r a l i Lypes r f f c c d i n q s y s t e n , t f e e d i n s T a r t s t o 3 muit:-arm rolwt is f i v e t o t e n tip.es 5 s c s p c n s l v e a s f e e d i n y g i r t s t o
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s i z e s , t?.e d i f f e r e n c e b e t w e e n a n d tb,e .#orst i s surprisingly s m a l l (a o n e h u n d e r e c pcr c e n t c h a n g e ) . 4)
X i t h t h e e x c e p t i o n of t h e s y s t e r r x h e r e v a c a z i n e s
system
are l o a d e d at t h e p o i n t o f n a n u f a c t u r e , m a g a z i n e f e e c i z q by w h a t e v e r systcrr. o f l o a d i n g i s more e x p e n s i v e than bv
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1 n . p o r t a n t t h a t p d r t s w h i c h a r e r e j e c t e d c a n be :on*;eyed tij :i ? o u , i l i s e d drea f o r t r a n s f e r back t o t h e o r i e n t i n q tr,ick. Several possibiiities exist: tPe r e t u r n ?rack could u t i l i s e a s l a t t e d b e l t conveyor Fii t e r n a t i v e 1 y , t h e re t 11r n v i t il a p p r o p ri a t c e l e v a t i on t r s c k c o u i d b e a v i b r a t o r y conve:,:or w i t h some for. o f s e i e v a t o r a t -13 a u n r o p r i a t e p o s i t i o r . . After i r : a t i o n -f t h e v a r i o u s p o s s i b i l i t i e s a n d w i t h ZI icdye o f t h e mechanics o f vlbr;ltory conveycrs i t wiis d e c i d c d t h a t , w i t h c a r e f u l design, t h e o r i e n t i n ? :rack ~ n dt h e r e t u r n t r a c k c c u l 6 b e d r i v e n b y .I sirlc?le .Jibration source. For t h i s , i t is necessary t h a t t h e n r i a n t i n n t r n r k h a s ;1 sl i a h t n e c a t i v e i n c l i n a t i o n ,
directly.
t i o n and t h a t a v i b r a t i c n a n q i e i s chosen which x i 1 1 a l l o w f o r w a r d c o n v e y i n n on b o t h t h e o r i e n t i n ? a n d return tracks. '.'arious x e t h o d s o f e l e v a t i n g t h e p a r t s f r o m t h c c o l l e c t i . o n a r e a on t h e r e t u r n t r a c k t o t h e i n l c t a r e a t o the orientin? track are possible. The c u r r e n t d e s i n n o f f e e d e r u s e s a l i f t t y p e mechanism p o w e r e d ltlv a u n e i ; m a t i c c v l i n d e r a n d t h i s a o o e a r s to work * ~, s a t i s f a o t o r i ly. ~t i s a n t i c i p a t e d t h a t i n f u t u r e , the f e e d e r w i l l be re-desiqned such t h a t t h e e l e v a t i n g mechanism i s a t t h e e n d o f t h e o r i e n t i n g t r a c k as t h i s woJld a l l o w t h e r o b o t t o p e r f o r m t h e e l e v a t i n g f u n c t i o n and t h i s would e l i m i n a t e t h e need f o r 2 s e p a r a t e e l e v a t i n g mechanism. ~
51 R e d u c i n ? t h e n u r b c r o f u n i q u e p a r t t y p e s i n t h e p r o d u c t h a s a n i n f l u e n c e on t h e r e l a t i v e Ferits o f t h e v a r i o u s systems b u t c o n s i s t e n t l y , t h e simple v i s i o n s y s t e m , t h c m u l t i - p a r t f e e d e r s;'ster a n d t h e n a g a z i n i n g a t t h e p o i n t o f m a n u f a c t u r e s y s t e ~were t h e t h r c c m o s t economic s y s t e m throuohout t h e s t u d y . 6) The v i s i o n s y s t e r , was t h e m o s t a p p r o p r i a t e f o r p r o d u c t f a m i l i e s w i t h many u n i q u e p a r t t y p e s .
7) The m u l t i - p a r t f e e d e r was m o s t a p p r o p r i a t e f o r p r o d u c t f a m i l i e s w i t h r e l a t i v e l y few u n i q u e p a r t types. 2.
S P E C I F I C A T T O N F O R A MULTI-PART FEEDER
Because t h e r u l . t i - p a r t f e e d e r has been i d e n t l f i c d as t h e most e c o n o m i c ' v e r s a t i l e ' p a r t s f e e d e r , p a r t i c u l a r l y when t h e p r o d u c t f a m i l y d o e s n o t c o n t a i n many u n i q u c p a r t t y p e s , i t w i s d e c i d e d t h a t a s p e c i f i c a t i o n would be w r i t t e n f o r t h i s type o f f e e d e r and t h a t a f e e d e r would b e d e s i n n e d which would l n c o r p o r d t e t h e requirements of the s p e c i f i c a t i o n . T a b l e 1 shows t h e c h a r a c t e r i s t i c s of a v i b r a t o r y bowl f e e d e r and t h e requirements o f a multi-arm r o b o t i c f e e d e r and i t c a n b e s e e n t h a t w i t h t h e e x c e p t i o n of t h e c a p a b i l i t i e s o f b e i n g a b l e t o f e e d a n d o r i e n t il i i i d e v a r i e t y o f p a r t g e o m e t r i e s a n d t h e p h y s i c a l s i z e o f t h e feeder, t h e requirements o f d robotic f e e d c r d o n o t match t h e c h a r a c t e r i s t i c s o f a v i b r a t o r ; , bowl f e e d e r . I f i t i s a c c e p t e d t!?at t h e b a s i c r e q u i r e m e n t is t h 3 t a w i d e v a r i e t y of p a r t s h a p e s n e e d t o b e a c c o r r p o d a t e d , t h i s c a n o n l y r e a s o n a b l y be d c h i e v e d u s i n g a v i b r a t o r y fecder. If a further requirerent is t h a t the capital c o s t p e r p a r t f e d n e e d s t o h c lower t h a n f o r a d e d i c a t e d f e e d e r i t i s n e c e s s a r y t h a t a common d r i v e u n i t be used t o s u p p o r t s e v e r a l t r a c k s ; w h i l s t t h i s i s n o t i r r p o s s i b l e usin: a v i b r a t o r y bowl f e e d e r , i t i s v e r y much e a s i e r t o a c h i e v e t h i s o b j e c t i v e u s i n g a linear vibratory feeder. T h e main d i s a d v a n t a g e of a l i n e a r f e e d e r i s t h a t t h e r e is n o simple r e - c i r c u l a t i o n p a t h f o r p a r t s which a r e r e j e c t e d i n t h e o r i e n t i n g s e c t i o n s a n d t t i s r e c r u i r e m e n t h a s t o b e m e t by some n o n - v i b r a t o r L r r c a n i . Kowever, a f u r t h e r a d v a n t a g e o f l i n e a r o r i e n t i n g t r a c k s i s t h a t i t j.s easier t o c o n s t r u c t t h e o r i e n t i n g d e v i c e s than it w o u l d b e i n a bowl f e e d e r . W i t h m u l t i p l e t r a c k i n g p e r d r i v e u n i t , t h e basic c o s t p e r track is reduced b u t a f u r t h e r high c o s t element is t h a t a t t r i b u t a b l e t o t h e development o f o r i e n t i n g devices. For very simple o r i e n t i n g problens t h i s is r e l a t i v e l y i n e x p e n s i v e b u t i n many c a s e s t h e d e v e l o p ment work n e c e s s a r y t o a c h i e v e a s a t i s f a c t o r y s o l u t i o n is e x t e n s i v e a n d t y p i c a l l y a bowl f e e d e r c o n p l e t e w i t h all t h e n e c e s s a r y o r i e n t i n g d e v i c e s i s d o u b l e t h e cost of the basic feeder. Bowl f e e d e r o r i e n t i n ? d e v i c e s a r e g e n e r a l l y craftsman produced but a m o r e s a t i s f a c t o r y s o l u t i o n , o a r t i c u l a r l y f o r l i n e a r t r a c k s would b e t o p r o d u c e t h e o r i e n t i n o s e c t i o n s u s i n g an NC machininq c e n t r e . This oresupuoses t h a t t h e aeonetry of t h e d e v i c e s i s i n o w n a n d f o r t u n a t e l y , f o r many d e v i c e s , t h i s i n f o r m a t i o n c a n b e o b t a i n e d fron: t h e c l a s s i f i c a t i o n and coding system f o r p a r t s h a n d l i n g developed a t t h e University of Vassachusetts. Using t h e p a r t ' s c o d e a n d t h e p a r t s i z e i t was t h o u g h t r e a s o n a b l e t o develop computer s o f t w a r e x h i c h would r e s u l t i n t h c p r o d u c t i o n o f a n XC p a r t p r o q r a m w h i c h c o u l d b e used t o p r o d u c e a f u l l o r i e n t i n ? s y s t e m from s o l i d b a r ; t h i s w i l l be d e a l t w i t h i n t h e n e x t s e c t i o n . If I t 1 s accepted t h a t
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The f e e d e r , a s d e s i g n e d , i s shown i n I'ig.1; tile i n c l i n a t i o n o f t h e o r i e n t i n g t r a c k i s - 2 degrees, the ~ n c l i n a t i o no f t h e r e t u r n t r a c k i s -10 d e g r e e s a n d t h e v i b r a t i o n angle is 15 deqrees. 'rests t o d a t e o n a ,wide r a n g e o f p a r t s w i t h d i f f e r i n g f r i c t i o n a l c h a r a c t e r i s t i c s h a v e i n d i c a t e d t h a t s u c c e s s f u l convcyi n q c a n be a c t i i c v e d o n b o t h t r a c k s w i t h c o n v e y i n g v e l o c i t i e s o f 50mm p e r s e c o n d o n t h e o r i e n t i n g t r a c k m d 75rrm p e r s e c o n d o n t h e r e t u r n t r a c k . Further, t h e t r a c k a n g l e s and t h e vi.hration a n g l e have been chosen such t h a t conveying on t h e o r i e n t i n g t r a c k is smooth and t h a t problems a s s o c i a t e d w i t h e r r a t i c p a r t movement t h r o u g h o r i e n t i n g d e v i c e s , a s i s O f t e n e v i d e n t i n v i b r a t o r y b o w l f e e d e r s , are n o t p r e s e n t . Hecause l a r g e b u l k s t o r a g e o f p d r t s i s n o t n e c e s s a r y i t was t h o u g h t t h a t t h i s s y s t e m w o u l d b e q u i t e c a p a b l e of h o l d i n g s u f f i c i e n t p a r t s t o e n s u r e t h a t t h e tine i n t e r v a l b e t w e e n L o a d i n g p a r t s wou: d b e a c c c p t a b l e . 3. 3.1
COMPUTER-A1 DED O R I E N T I N ( ; TPACK IYANUFACTURE Introduction
B e f o r e i n t r o d u c i n o t h e methodoloyy o f o r i e n t i n q t r a c k production usin? i n t e r a c t i v e computer-aided p a r t programming, i t i s n e c e s s a r y to r e v i e w b r i e f l y t h e b a c k g r o u n d of work c a r r i e d o u t j o i n t l y by t h e U n i v e r s i t y o f M a s s a c h u s e t t s a n ? t'ic U n i v e r s i t y o f S o l f o r d o n "Design f o r A systematic classif i c a t i o n technique h a s been develryxd t o h e l p desiqners t o d e t e r m i n e t!ie d e g r e e o f a u t o m a t i o n o f a s s e m h l y w h i c h 1s e c o n o m i c a l f o r B p a r t i c u l a r p r o d u c t a n d t o r e d u c e t h e d i f f i c u l t i e s a n d h e n c e costs o f p a r t s h a n d l i n g and i n s e r t i o n . I t i n t r o d u c e s a method o f y u a n t i f y i n q d e s i q n e f f i c i e n c y f o r a s s e m b l y a n d shown how h i g h a s s e r h l y cost f e a t u r e s c a n b e i 6 e n t i f i e d . To t a c k l e t h c t r a d i t i o n a l l y d i f f i c u l t a r e a of a u t o m a t i c p a r t s f e e d i n u and o r i e n t i n q , a 3 - d i q i t s c o d i n g system. h a s bcen d e v i s e d t o d e s c r i b e t h e p a r t ' s f e e d i n g c h a r a c t e r i s t i c s by s p e c ing its basic shape, b a s i c symmetry a n d i m p o r t a n t ssymetricai f e a t u r e s ( 5 ) . Such a n a n a l y t i c a l approach o r o v i d e s a basis f o r the establishment o f a parts/orientino d e v i c e r e l a t i o n s h i u w h i c h is e s s e n t - i a l t o t h e P r e s e n t work. I n a d d i t i o n , a d c v i c f c o d i n y s y s t e m a s shown i n F i g . 2 has a l s o been developed t o c a t c g o r i s e o r i e n t i n ? d e v i c e s f o r v i b r a t i n g b o w l f e e d e r s (6) a n d t h i s t a k e s t h e f o r m o f a two d i g i t d e v i c e - c o d i n s s y s t e m . The f i r s t d i g i t represents the b a s i c device configuration ( c . y . f l a t or s l o p e d t r a c k ) w h i l s t t h e s e c o n d d i q i t distinguishes the various device modifications (e.g. rr?.il, s l o t , g a p ) . The s y s t e m d o e s n o t g e n e r a t e a u n i q u e c o d e f o r e a c h d e v i c e b u t t h e r e are sets o f e q u a t i o n s which can be uscd t o c a l c u l a t e d e v i c e parameters (e.9. width o f a narrowed t r a c k ) based on t h e i n p u t of c r i t i c a l . p a r t d i m e n s i o n s ( e . g . l e n g t h a n d w i d t h of t h e p a r t ) . The d e v e l o p m e n t o f t h e p a r t a n d d e v i c e c o d e s h a s l e d t o a n o t h e r comprehensive doculrent which relates a p a r t i c u l a r p a r t code t o a aroup o f o r i e n t i n g d e v i c e s w h i c h a r e c a p a b l e of c o l l e c t i v e l y p r e s e n t i n g t h e p a r t a t t h e o u t l e t of t h e system, i n a s i n g l e o r i e n t a t i o n t o p e t h e r w i t h a p r e d i c t i o n of t h e r a t e o f t h e p a r t s . T h i s p r o v i d e s a s y s t e m a t i c way o f a n a l y s i n a f e e d t r a c k desir;n, b u t I t does n o t h e l p to siropllfy feed track p r o d u c t i o n f o r c o n v e n t l o n a l v l b r ~ t o r yb o w l f e e d e r s a n d t h ~ 1s 9 o f t e n a t t m e - c o n s u m l n q a n d h e n c e e u p e n 4 t v c
c,perati.;n. iic).,~evcr, i f r'. l i n e a r v i b r a t o r y o r i e n t i n r : t r a c k , i s to be used, t h e machini.ny oL t h o m j o r f e a t l l r e s of the o r i e n t i n c d c v i c o s on t h e t r a c k from s o l i d m e t a l b,lr becomes p o s s i b l e . I t i s envis:icred t l i r i t such il t a s k c a n b e perforn.ec1 e c w o T i c d l l y 011 a NC m a c h i n i n g c e n t r e i f p a r t p r o f l r a v m n c ccin b c a i d e d by t i l e u s e of a c o n p u t e r . 3.2
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k t t h i s p o i n t i t became a p p a r e n t t h a t b o t h t h c existi n g p a r t s a n d d c v i c e c o d e s werc n-,t s p e c i f i c enouok, t o s e t u p a u n i q u c r e l a t i o n s h i p bctwocn a c i , n p o n e n t p a r t a n d i t s c o r r e s p o n d l n g o r i e n t i n v des,iccs. As g e n e r a l i s s t i o n i s i n e v i t a b l e i n 3ny c o d i n a systerr., t n e same p a r t c o d e may r e f e r t o a number o f p a r t s r o u o f t h e sape s h a p e s a n d f e a t u r e s b u t i i h i c h m i c h t r an e n t i r e l y d i f f e r e n t s e t o f o r i e n t i n < ; d e v i c e s . d e v i c e code, w d s a l s o d e s i g n e d t o c o v e r a qr3up of d e v i c e s w i t h s i m i l a r c h a r a c t e r i s t i c s and h e n c c t h i s also I S b y n o means u n i q u e . H o v e v e r , i n s t e a d o f red e v i s i n g b o t h s y s t e m s to s u i t t h i s a p p l i c a t i o n , i t w a s d e c i d e d t h a t t h e oroblcrr w o u l d b e t a c k l e d b y a d o p t i n g i n t e r a c t i v c p r o n r a i n m i n y a n d by mdkinq u s e o f t h e f e o t u r e s o f p a r t s to i d e n t i f y t h e r e q u i r e d d e x J i c e . Thus, t h e pliysicai ran-rmchine i n t e r f a c e o f t h e system is d e f i n e d : t h e i n p u t o f a p a r t c o d e t h r o u q h a C O T E t o r t e r m i n a l wi.11 p r o m p t t h e s u ? g e s t i o n 3 f o n e o r Tore o r i e n t i n g d e v i c e c o n f i g u r a t i o n s c a p a b l e of o r i . e n t i n u the part. Confirnation of a particular tyoe of device then leads t o f u r t h e r rcqucsts concorninn c r i t i c a l p a r t d l n e n s i ~ se s s e n t i a l t o t h e e f f e c t i v e n e s s o f t h e device. The s y s t e m w i l l f i n a l l y q e n e r , a t c a NC p a r t p r o g r a m t o m a c h i n e t h e r e q u i r e d t r a c k from s o l i d b a r . A major c o n s i d e r a t i o n i n t h e d e s i q r . o f t h e s o f t w a r e a r c h i t e c t u r e is i t s e x p a n d a b i l i t y . I f t h e system is
u s e d t o g e n e r a t e p a r t pr0grarr.s f o r a q r o w i n u number of o r i e n t i n g t r a c k s , t h e v a r i c t y o f o r i e n t i n g d e v i c e i s l i k e l y t o i n c r e a s e a n d t h e s i z e o f t h e NC p r o g r a m g e n e r a t o r wi II s o o n e r or l a t o r e x c e e d t h e r e m o r y l i m i t lmposed by t h c o p c r a t i n o s y s t e m . R l t h o u a h u n d e r most o p e r a t i n g s y s t e c s u s e r ?rocirons c a n b c c h a i n e d tocjether, t h e need to r e c o r d c u r r e n t v a r i a b l e s b e f o r e chaining and t h e i r r e t r i e v a l t h e r e a f t e r is o f t e n t e d i o u s 2 n d t i m e c o n s u m i n g . An a l t e r n a t i v e i s t o adopt a s t r u c t u r e d approach such t h a t t h e e n t i r e o r i e n t i n q t r a c k i s c o n s i d e r e d t c be comuosed o f J. series of d c v i c c s , e a c h having its oyn i n d e p e n d e n t r o u t i n e f o r devi. ce qeorne t ry c a 1 c u 1 a t i on . 'I'hc?sc r o u t i n e s c a n be s t o r e d s e p a r a t e l y from t h c mrist.cr p r o g r a m g e n e r a t o r w h i c h i s r e s p o n s i b l e mainly- f o r t h e r o u g h i n g o p e r a t i o n s and f o r w r i t i n q p a r t programs block information onto t h e output f i l e . Thus, a p a r t i c u l a r d e v i c e r o u t i n e i s ' p u l l e d - i n ' and c o ~ p i l e d w i t h t h e master p r o g r a r . a e n e r a t o r o n l y when t h e d e v i c e i t r e p r e s e n t s .is r e q u i r e d f o r a p a r t i c u l a r o r i c n t i n q track. A l t h o u q h i t n e e d s more t i n e t o r u n a n unc o m p i l e d p r o g r a m , i t i s b e l i e v e d t h a t s u c h a r.odular approach w i l l minimise d a t a h a n d l i n y r e q u i r e m e n t s and h e n c e p r o g r a m r u n timc. One of t h e l i m i t a t i o n s i n u s i n ? a m a c h i n i n g c e n t r e f o r o r i e n t i n g device production is t h e diffj.c:ilty o f u t i . l i s i n g sm.all c u t t i n g t o o l s ( e n d r i l l s o r s l o t d r i l l s ) t o machine d e v i c e d e t j i l s which a r e c l o s e d to t h e i n n e r a p e x of t h e 1,-shape t r a c k . Small cutters are u s u a l l y s h o r t ( c u t t e r e d a e a n d s h a n k ) , and a n y c o l l i s i o n b e t w e c n t h e c h u c k of t h e tool h o l d e r a n d t h e w o r k p i e c e i s c l e a r l y u n a c c e p t a b l e . For example, a w i p e r b l a d e p r o j e c t e d f r o m t h e wall o f a f e e d t r a c k c a n e a s i l y b e m a c h i n e d f r o m a s o l i d lorn s q u a r e b a r as l o n u a s t h e r e i s a r e a s o n a b l e g a p s i z e between t h e blade and t h e s u r f a c e o f t h e t r a c k . Aovever, i f t h c dcvice r e q u i r e s to b e desiqned such t h a t t h e gap s i z c is small, a s m a L l diameter slot d r i l l of s u f f i c i e n t l e n g t h would b c i m p r a c t i c a l . Similarly, orienting device such a s s i l h o u e t t e s and s c a l l o p s u s u a l l y have a n i n f i n i t e v a r i e t y o f p r o f i l e s which c a n n o t b e r e a d i l y s t a n d a r d i s e d and t h e s e also nay r e q u i r e s m a l l and a c c u r a t e f e a t u r e s s u c h as s h a r p a c u t e c o r n e r s which are too d e t a i l e d t o b e p r o d u c e d by t h e s m a l l e s t o f s l o t d r i l l s . T h u s , a s i n g l e NC m a c h i n i n g c c n t r e i s n o t c a p a b l e of p r o d u c i n g many e n t i r e o r i e n t i n g t r a c k s d e s p i t e its v e r s a t i l i t y . I t was d e c i d e d , t h e r e f o r e , t h a t s t a n d a r d i n s e r t s such as wall proj e c t i o n s and s c a l l o p s would b e added t o c o n t r o l l e d reccsses p r o p e r l y m a c h i n e d o n t h e o r i e n t i n r r t r a c k a f t e r t h e l a t t e r !]as b e e n c o m p l e t e d . These i n s e r t s have b e e n s t a n d a r d i s e d a s f a r as i s p r a c t i c a b l e a n d t h e c o r r e c t p o s i t i o n i n a on t h e o r i e n t i n g t r a c k i s a c h i e v e d by m a c h i n i n < : a - J p r o p r i a t e l o c a t i o n s usincr t h e machininq- c e n t r e . 9efore software implementation c o u l d be a c h i e v e d i t x a s n e c e s s a r y t o s e l e c t t h e c u t t i n g t o o l s to be used. Even w i t h t h e geomct.ri a device well-defined, tho tool path t h a t will g e n e r a t e t h e r e q u i r e d p r o f i !e w i l l v a r y d c c o r d i n g t o t h e t y p e and t h e s i z e of c u t t e r u s e d . 'Thus, a f r e e c h o i c e a p p r o a c h t o t o o l s e l e c t i o n would h a v e c o r p l i cated t h e s o f t w a r e u n n e c e s s a r i l y w h i l s t c o n v c r s c ? l y , i f
ttle s o f t v n r o h.34 k e n t o o r i q i d l y s t r u c t u r e d , il t t e r s o f s p e c l f i c si z c s -xnu;c'. h c i s ,would lie linsccepta!>lt?. I t wi~s c o m p r a n i s e j i o , ~ l dhc
e fixed f o r t h e rOutir.c, d i f f e r e n t sri t h i n t h e ranc;e i i o u l d be c!:mpennated :-sin<. t h i s SyStCT, f 9 r ]q t h e u s e 3f t o o l o f f s e t s . too i s & r e s e l e c t e d f r o m 3 tr,ol l i b r a r y a c c o r d i n g 20 t h e t;:o1 d e s c r i p t i o n and t h e r a n q f of t.o.31 climeters deiined
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system 1r.plcmentation
3.3
3.3.1 :lardware C o n f i c f u r i t i o n ~5~ ? h i l o s o p h y o f a p p l y i n g c o m p u t e r - a l d e d z a n u f a c t u r i n q t e c h n i q u e s t o o r i e n t i z q t r a c k p r o d c c t i o n -was iPTle?lc".t e d u s i n g 3 K e a r n e y a n d n r e c k e r H.NS-l.jO0 SC m c h i n i n ? centre. The s o f t w a r e was w r i t t e n i n B a s i c - P l u s r u n n i n g ,dndcr RSTS/C I?.ounted c n a SYSTTXE SERIES 6 4 0 0 [IXC ~ n P 1 1 / 3 4P r o c e s s o r ) .
-
The tiblc 1 5 0 0 i s a -2-axis n u m e r i c a l l y c o n t r o l l e d , h o r i z o n t a l s p i n d l e r a c h i n i n q centre h a v i n a 3 l i n e a r a x i s (X, Y , Z) a n d a r o t a r y a x i s m o t i o n s , w i t h a 30 All. axes t7ol magazine randor, s e l e c t i o n tooi. changer. C ~ T :be commanded t o move i n e i t h e r a b s o l u t e or i n c r e m e n t a l mode a t c o n t r o l l e d f e e d r a t e s u s i n < ? t h e >"i I w a u k e e - h t i c w o r d - a d d r e s s p r o r r r a n w i n n f o r m a t . The maximum t r a v e l o f t h e m a c h i n e i n t h e X, Y , Z a x e s dre 1500m., l O O 0 m n m d jOOmn r e s p e c t i v e l y .
As t h e w o r k p i e c e s are s t a n d a r d r c i l d s t e e l b a r a p p r o x i T a t e l y 40nm s q u a r e a n d 800m l o n g , i t was d e c i d e d t h a t t h c o n l y p r a c t i c a l way of mkichining t h e s e w o u l d b e bjF m o u n t i n g t h e n on a f i x t u r e which i s a t t a c h e d to an a n g l e p l a t e v h i c h i n t a r n sits on t h e r o t a r y table (k'ig.3) . w i t ! > t h e l o n g a x i s o f t h e b a r p a r a l l e l t o t h e \' a x i s o f t h c m a c h i n e . By r o t a t i n ? t h e t a b l e 2 9 0 d e g r e e s c i t h c r l e f t or t h e r i g h t h a n d t r a c k s c a n bc machined w i t h t h e r e q u i r e d t r a c k a n c l e ( p o s i t i v e O r nqative) The f i x t u r e c o n s i s t s 0 5 four v e e - b l o c k s , two f i x e d a n d t w o movable, l o c a t e d b y d o s r e l p i n s o n T!ie t w o r;.ovablc v e c s ? r o v i d e ii g r o u n d b a c k p l a t e . a d c q u a t c s u p p o r t a t t h e mid-span o f t h e t r a c k a n d t h e i r p o s i t i o n s c a n b e a d j u s t e d t o allow t h r o u o h h o l e s t.o be m a c h i n e d a t v a r i o u s p o i n t s o n t h e t r a c k .
.
3 . 3.2
D.itabase
In o r d e r t o allow f o r e a s y c h a n q e s o f t h e i n p u t i n f o r n a t i o n , n o t a b l y t h e g e o m e t r y a n d c o n p o s i t i o n of t h e f e e 6 t r a c k , t h e s i z e s o f t h e c u t t i n g tools, and t h e c o n d i t i o n s o f c u t t i n g , t h e concept o f d a t a independency has been adopted i n t h e design o f t h e software. 0 p e r a t j . n g p a r a m e t e r s a r e s e p a r a t e d f r o m t!ic a p p l i c a t i o n p r o g r a m a n d a r e s t o r e d i n d i f f c r e n t f i l e s f o r m i n q t.hc datdba.5f o f t h e s y s t e m (Fip.4). ? h e r e a r e t h r e e i n p u t d a t a f i l e s , t h e s e are:
il) The T r a c k S t r u c t u r e F i l e ; t h i s r e c o r d s t h e s t r u c t u r e of a feed t r a c k desifled to o r i e n t a s g e c i f i c component. Each r e c o r d i s made up o f t h e p a r t c o d e o f t h e c o m p o n c n t , a record n u n b e r ( u s e d to i d e n t i f y d i f f e r e n t t r a c k s u s e d by t h e same p a r t c o d e ) , 2nd a maximum o f 1 2 d e v i c e s . Data is s t o r e d u s i n g B a s i c - P l u s ' s R e c o r d 11'0 f i l i n g f a c i l i t y a n d c a n b e u p d a t e d and r e t r i e v e d randomly. Althouuh t h e r c is n o pictorial aid to t h e operator during t h e d a t a e n t r y s t a g e , t h e s y s t e m p r o v i d e s sone r - e a s u r e s t o c h e c k t h e v a l i d i t y o n t h e p h y s i c a l r e l a t i o n s h i p b e t w e e n two c o n s e c u t i v e d e v i c e s ( e . 9 . a h a l f n r e s s u r e b r e a k nrust he c u t p r i o r t o a r a i l ) . ( 2 ) The T o o l L i b r a r y ; t h e t o o l l i b r a r y r e c o r d s i n f o r m a t i o n o f t h e a v a i l a b l e tools which i n c l u d e :
.
. . . .
t h e t o o l c o d e ( e . a . T@@2@@) t h e tool d e s c r i p t i o n ( e . 9 . l o n o s e r i e s 3 f l u t e slot cutter) t h e diameter and l e n g t h o f t h e t o o l t h e s p i n d l e s p e e d a n d s p i n d l e code ( f o r m i l d s t e e l ) and t h e feed rates ( t r a v e r s i n g and s i n k i n c ) .
T h s s y s t e m a l s o c h e c k s t h e v a l i d i t y o f t h e worda d d r e s s f o r m a t s t o b e used b y t h e ? a r t proqram. (3) The C u t t i n g P a r a m e t e r F i l e ; t h i s c o n t a i n s d a t a r e l o t i n g t o t!ic b a s i c d i m e n s i o n s of t h e t r a c k ( e . g . thickness o f w a l l and base, angles of i n c l i n a t i o n o f p o s i t i v e and n e g a t i v e t r a c k s , and l e n g t h s o f o r i e n t i n g d e v i c e s ) , and t o t h e operatinq- c o n d i t i o n s o f t h e m a c h i n e ( c . g . p o s i t i o n o f f i x t u r e , z e r o r e f e r e n c e s of t h e JXCS e t c ) A l i o f t h e s t o r e d i n f o r r a t i o n h a s to tic r e a d i n t o t h e p r o u r a m u e n e r a t o r b e f o r e i t c a n b e properly run.
.
401
3. 3 . 3
I':irt I ' r ~ q r d r . Generator
d n d a b i i i t y of t h c s o f t w a r e , t h e a t o r i s di.;ided i n t o t h r c c p a r t s : r, t h e m : i s t e r p r o r r a m y r n c r d t o r a n d tke device f i l e .
(1) X o n i t o r ; t h i s i s a f r o n t p r o c e s i n g proyrorr. x h i ch upon t h c i n p u t o f a p a r t c o d e , s c a r c es d e v i c e r o u t i n e s frcm t h e D e v i c e r i l e f o r t h c r c q u i r c p r t o r i c n t a t i o x a n d i n s e r t s t h e r e l e v d n t S t a t e I r e n t s i n t o t h c >!aster Procjrom G c n c r a t ( i r t o r i c n r r o t e a neil B a s i c o r o g r n m . I t t h e n " c h a i n s " i t s e l f t,o the l a t t e r w h i c h is t cun:pi.led a n d r u n . R e l c v a n t Lnfor1::ation o n tile f t r a c k s t r u c t u r c i s r i l s r j p a s s c d t o t h e new p r o g r a r r through t h e syst c m ' s facl l i t y . ( 2 ) Master P r o g r a m G e n e r a t o r : t h i s i s p a r t o f ti:c P a r t Program G e n e r a t o r and i s s t o r e d i n i t s secjUentia.1 t e x t f o r m ( i . e . n o t a B a s i c p r o q r a r ; . ) . Cpon b e i n g a c c c s s c d by t h e ' M o n i t o r ' , r o u t i n e s t a t c m e n t s r e l e v a n t t o a n o r i e n t i n g & v i c e a r e i n s e r t e d i n t o t h c rndster o r o g r a m t o c o n v e r t i t i n t o a complete 3 a s j . c p r o g r m t h a t w i l l prudu:e t h e r e q u i r e d NC t a p f . 'The ? a s t e r p r c c r a m G c n c r a t o r c o n s i s t s m a i n l y of :our p n r t s a n d t h c s c are:
( a ) R o u g h i n g r o u t i n e s : - A s t'nc l e v c l o f t n c t r a c k s u r f a c e may chancre c o n s i d e r a b l y r h r o u q h o u t t h e e n t i r e t r a c k l e n g t h , t h e f i r s t t a s k t h e g e n e r a t o r h a s to p e r f o r m i s to a n a l y s e t h e s t r u c t u r e o f t h e f e c d t r a c k so t h a t t h e maximum t r a c k t h i c k n e s s ( a t i t s s t a r t i n g p o s i n t ) may be c a i c u l a t c d . The program t h e n c a i c u l a t c s t h e c x t r e d t i e s o f tool. l o c a t i o n s usi.ng t h e g e o m e t r y t r a n s f o r m a t i o n r o u t i n c , s c l e c t s t h c a p p r o p r i a t e tooli n g u s i n g t h e tool s e l e c t i o n r o u t i n e a n d p r i n t s t h o p a r t p r o g r a r . ( b l o c k 1.: block) f o r roughing o n t o t h e output f i l e using standard p r i n t routines. 'The t r a c k . s u r f a c e t h u s o b t a i n e d is t h e n n e m r i s e d a s t h c rc f e r e n c e s u r f ace f o r s u b s e q u e n t d e v i c e - b y - d e v i c e cuttiny operations. ( b ) Gcomctry T r a n s f o r m a t i o n Routine:- T h i s s t a n d a r d r o u t i n e is w r i t t e n t o t r a n s f o r m r c f c r r n c c p o i n t s d e f i n e d o n t h e c r o s s - s e c t i o n o f t h e t r a c k to i t s c o r r e s p o n d i n g X-2 m a c h i n e c o - o r d i n a t e s , w i t h t h e o r i g i n t a k e n a t t h e c e n t r e of t h e r o t a r y t a b l e . If t 5 c d i r e r : t i o n o f c u t t i n g i.s p a r a l l e l t o t h e Y- a x i s eovemcnt, t h e program a I s 0 a t t c n l p t s t o e v a l u a t e t h e e x t r e m c tool l o c i t i o n s i n t h c x a n d Z a x c s so t h a t t h e number of p o s s e s , t h e l e n g t h o f trar.c?ls, a n d s o m e t i m e s , t h e p c r m i s s i b l c r a n g e o f t o o l diarncter ( t o s u i t t h e d c s i g n t o o 1 p a t h ) c a n be c a l c u l a t e d .
4.2 A t P r e s e n t about 2 0 devicc r o u t i n c has bccn I n y e n e r a l t h e y are c a p a b l e o f w r i t t c n and p r o v e d . ( J r i c n t i n q the dcsiqnc?tl p a r t s t h o u c h m i n o r m o d i f i c a t i o n s t o SOT- :!r.u.i(:e p a r a n c t c r c q u o t i o n s may b e n e c e s s a r y . 4.3 ?'he p r e s e n t x o r i w i l l be e x t e n d e d t o c o v e r n o r e d e v i c e s ancl t o ilsc a sr.:a:ler SC m a c h j n e t o p r o d u c e c r i t i c a l s m a l i d e t a i l s on i n s e r t s .
4.3. The d e c i s i o n t u p r o d u c e Z r i e n t i n q t r a c k s f r o m m i l d s t c e l was p c r h a p s unwise. >!!achinina t i r r e s a r e I o n u Find t h e t r a c k s arc heavy. I t is t h o c c h t t h a t f i i t u r e trLicl:s w i 1 . l b c m a n u f a c t u r e d f r o m an a l u m i n i u m .>llo;. a n d i t w i l l he a c c e p t e d t h a t t r a c k s w i l l n o t !If a s r e s i s t a n t t o wear a s m i l d s t e e l o n e s .
REFEREXCES i.
R e d f o r d , A . H . , L o , E . K . a n d K i l l c c n , P. J . , " P a r t s F e e d e r C o s t R n a l y s i s f o r hlul t i - P a r t H o b o t i c A s s e m b l y " l5TH CIRP 1n t c r n a t i o n a l S c n i n a r o n M a n u f a c t u r i n n S y s t e x s . A m h e r s t , Mass. June 1983.
2.
Suzuki, '1'. a n d Xohno, M., "The F l e x i b l e P a r t s F e e d e r w h i c h h e l p s a r o b o t asscrhlc a u t o n a t i c a l l y " Assembly A u t o m a t i a n , Feb. 1981.
3.
R e d f o r d , A. H . a n d C r o s s l e y , T. R . , " D e s i g n F o r R o b o t i c Assembly P r o g r e s s Keport" P r o c e e d i n g s o f the SERC Ro!mtic I n i t i a t i v e G r a n t e e s C o n f e r e n c e , I3irmingham, S e p t . , 1 9 8 2 .
1.
S w i f t , R. G. ancl R e d f o r d , A. I I . , " P r o d u c t D e s i g n f o r Automatic Asse&ly" P r o c e c d i n y s o f t h e 2nd I n t e r n a t i o n a l C o n f c r c n c c on Assembly A u t o m a t i o n , D r i y h t o n , Mdy 1981.
5.
" D c s i g n f o r A s s c m b l y Handbook" P u b l i s h e d b y S a l f o r d tinivcrsit.y I n d u s t r i a l Centre L t d . , S a l f o r d , Enqland, O c t . 1982.
6.
"IlandLook o f F e e d i n g a n d O r i e n t i n g T c c h n i q u e s f o r S m a l l P a r t s " P u b l i s h c d by U n i v e r s i t y o f M a s s a c h u s e t t s , A n h e r s t , X a s s a c h u s e t t s , 1976.
REQUIREMENTS OF A MULTI_ _ _ i l _ -
(c) T o o l S c l e c t i o n R o u t i n e : iu'ith s n c c i f i c a t i o n s o n t o o l d e s c r i p t i o n ancl t o o l c l i a r e t c r , t h i s r o u t i n c : s e l e c t s t h e a p p r o p r i a t e t o o l f r o m t h e l i b r a r y . The r e i c v a n t tool c o d e , s p i n d l e c o d e , d i a m e t o r and i c e d rates a r e r e t u r n e d t o t h e P a r t Program G e n e r a t o r . (d) Printing Routines:N C p a r t programming b l u c k s are w r i t t e n o n t o a n o u t n u t f i l e d c s i g n a t c d on a s p c c i f i c c h a n n e l by a n u n b c r of s t - a n d a r d p r i n t i n g routincs. The i d e a of s t r u c t u r e d p r o q r a m m i n g i s a d o p t e d silctl t h a t e a c h r o u t i n e is o n l y r e s p o n s i b l e f o r t h e h a n d l i n g of a s p e c i f i c c u t t i n g o p e r a t i o n . The r o u t i n e s i n c l u d e :
. . . . . . . . .
.
s e q u c n c c number c o u n t . i n q tool s c l c c t i n g a n d c h a n g i n g rotary table turning i n i t i a l tool approachin: coolant control r o u g h i n g w i t h tool compensation linear a n d c i r c u l a r c o n t o u r i n g d r i l l i n ? and tappinn opti.ona1 s t o p p i n g e n d of program p r o c e s s i n g
Device F i l e
(3)
This device-dependcnt t e x t f i l c contains b a s i c p r o g r a m i n g s t a t e m e n t s t h a t are i n s e r t e d i n t o t h e Master P r o g r a m G e n e r a t o r when t h e d e v i c e is c a l l e d for. Each d c v i c c r o u t i n e , upon e x e c u t i o n , w i l l r e q u e s t p a r t s geometry i n p u t r e l e v a n t t o t h a t d e v i c c , c o n v e r t i t t o d e v i c e p a r a m e t c r s , and c a l c u l a t c t h e r e l a t e d c o - o r d i n a t e s on t h e w o r k p i e c e f o r p a r t program o u t p u t . 3.3.4
systcm Output
The s y s t c n o u t p u t s f o u r d o c u n e n t s ; a n :IC p a r t p r o g r a m punched t a p e , a f o r m a t t e d p a r t procram l i s t i n q , a n o p e r a t i n g i n s t r u c t i o n , and t h c tool l i s t . 4.
COWCLUSTOXS A X D FLJHTHER WORK
4.1 The p h i l o s o p h y o f a p p l y i n g c o m p u t e r - a i d e d m a n u f a c t u r i n g t o f e e d t r a c k m a n u f a c t u r e i s implcmcnted. NC t o p e s o u t p u t f r o m t h e s y s t c m h a v c b e e n t e s t e d a n d used t o c u t mild steel workpiece ( F i q . 5 ) . The a v e r a g e c u t t i n g t i m e p e r t r a c k is f i v e h o u r s .
402
ARM ROBOT FEEDER
Compact
Compact
R e l a t 1 ve 1y c v p e n s 1 vc
Inexpensive
Long F e e d t r a c k
s h o r t Feed t r a c k
L a r g e b ~ l ks t o r a y e
S m a l l hulk storage
l l l y h reed r a t e
Low F e e d r a t e
1
u p c n s i v e t o Re-tool
A b i l i t y to o r i c n t a w i d e v a r e i t y of p a r t s
T n e x p c n s i v c t o Re-tool A b i l i t y t o o r i e n t a wide v a r i e t y of p a r t s .
TABLE 1
.
Fig.1
Linear Parts Feeder
Fig.2
Fig.3 Hardware Configuration
Coding System for Orienting Devices SECOND C Wide Track
0
Narrowed Track
1
Slot or groove
2
Inserts
3
Flat Tracl
cn U
403
PROGRAM GENERATOR
PROGRAM
.._..
-Fin - w -4-
Inform;ation Flow in the Computer- Aided Feed Track Manufacturing System
Fig. 5
404
FEED TRACK
Selection of Feed Tracks
I
7