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Xantia provides a boost for automotive composites
CITRy~NO~ N
Xantia provides a b o o s t for automotive c o m p o s i t e s Citroi!n l e a d s E u r o p e ' s m o t o r i n d u s t r y in t h e u s e o f c o m p o s i t e s in m a s s p r o d u c t i o n cars a n d its l a t e s t m o d e l t h e X a n t i a is n o e x c e p t i o n . Like its p r e d e c e s sor, t h e BX, it f e a t u r e s an i n j e c t i o n m o u l d e d BMC h a t c h b a c k . T h e r e is a l s o a t w o p a r t f r o n t - e n d c o m p r i s i n g SMC a n d g l a s s r e i n f o r c e d p o l y i m i d e , a n d a c o m b i n e d c y l i n d e r h e a d c o v e r a n d air filter. As a f u r t h e r r e a f f i r m a t i o n o f its b e l i e f in c o m p o s i t e s Citroi!n h a s i n v e s t e d in f a c i l i t i e s to e n a b l e it to m a k e m a n y o f t h e parts i n - h o u s e .
he Xantia is aimed at the top end of the medium-size saloon cat" m a r k e t which, Citroen says, a c c o u n t s for more t h a n 20% of all car sales. The c o m p a n y plans to p r o d u c e 180 000 Xantias in 1993, 45% of which are destined for the French market. P r o d u c t i o n of the vehicle began at Citro~n's p l a n t in Rennes-la-Janais, France, in December 1992 and the car was l a u n c h e d across E u r o p e four m o n t h s later. A m a j o r c h a n g e in the p r o d u c t i o n of the Xantia is Citro~n's decision to make m a n y of the c o m p o s i t e p a r t s in its own factories r a t h e r t h a n use external moulders. It has invested in a new p r o d u c t i o n unit capable of m a k i n g 1200 h a t c h b a c k s a day and a bulk
T
Two pieces of the Xantia's hatchback are moulded inhouse by Citroen, Manducher makes the window frame.
:(
R E I N F O R C E D PLASTICS J U N E 1 9 9 3
moulding c o m p o u n d (BMC) machine capable of making one tonne of c o m p o u n d an hour. The Xantia h a t c h b a c k weighs 15 kg and is m o u l d e d in t h r e e p a r t s - an internal r e i n f o r c e m e n t panel, an e x t e r n a l lower panel and the rear window f r a m e . The first two p a r t s are m a d e by CitroSn. French m o u l d e r M a n d u c h e r , w h i c h m o u l d s the h a t c h b a c k for the CitroSn ZX model, fabricates the window frame. The process used to mould the h a t c h b a c k is the so-called IMBMC technique developed by Owens-Corning and M a n d u c h e r for the two piece ZX hatchback. For the larger Xantia the runs were too long to m o u l d in two pieces so the outer moulding was split, says Jacques Gerard of Owens-Corning. The join in the two sections of the exterior moulding is hidden by the rear window glass. The 1.2 kg window frame p a r t is made by M a n d u e h e r in its Pouranc~ plant. The PE7 BMC is c o m p o u n d e d by Manducher with 18% of Owens-Corning's R63SX3 roving as re i n f o r c e m e n t . The p a r t is m o u l d e d in a 900 t o n n e clamping press which includes a special a u t o m a t i c unit to c u t gates and preserve the geometry of the part during cooling. Manducher says t h a t it is currently making a r o u n d 1000 window frames a day; m a x i m u m capacity is 1450. The resin used for the BMC h a t c h b a c k is Disitron 2708 o r t h o p h t h a l i c u n s a t u r a t e d polyester from Alusuisse Italia. This is the same grade used in the Citroen AX and BX model hatchbacks. When the Disitron resin is combined with low profile additives from Union Carbide an excellent surface finish can be obtained, says Alusuisse. A p a r t direct from the press reveals no porosity and no show through. Alusuisse told Reinforced Plastics t h a t Disitron is the only polyester specified for use in Citroen h a t c h b a c k s -- in spite of having a higher price than many competitive resins. The reason for its choice, says the firm, is the consistent high quality it is able to offer. The resin is p r o d u c e d in 25 tonne lots u n d e r ISO 9002 conditions to a very tight specification. Alusuisse is a completely
0034 36179:]$6.00
( ' 1993, Elsex~ier S c i e n c e P u b l i s h e r s Ltd.
C i n t e g r a t e d p r o d u c e r of u n s a t u r a t e d p o l y e s t e r with its own m a l e i c a n h y d r i d e facility (see I n d u s t r y News). T h e injection m o u l d i n g p r e s s e s u s e d by C i t r o e n to m a k e t h e h a t c h b a c k i n n e r a n d lower e x t e r i o r p a r t s are built by ACB Loire. Two of t h e firm's M C P / F C P 2000 p r e s s e s h a v e b e e n i n s t a l l e d in t h e c a r m a k e r ' s Rennes factory. T h r e e s i m i l a r p r e s s e s are u s e d by M a n d u c h e r a n d I n e r g a of S p a i n to m a k e t h e ZX h a t c h b a c k . ACB says t h a t C i t r o e n c h o s e to use its p r e s s e s f o r t h r e e r e a s o n s : to c o n s e r v e i n t e r n a l know-how, to d e v e l o p its u n d e r s t a n d i n g of t h e f a b r i c a t i o n of BMC, a n d to gain a m a s t e r y of t h e m o u l d i n g of t h e r m o sets. The two p r e s s e s installed at Citro~ a r e c a p a b l e of p r o d u c i n g 1250 u n i t s a day, working on a three shift system. The m a c h i n e s h a v e a vertical f o r m a t r a t h e r t h a n t h e m o r e c o n v e n t i o n a l layout. This gives access f r o m b o t h sides of t h e p r e s s as well as r e d u c i n g t h e floor s p a c e required. The p r e s s e s a r e set into a p i t w h i c h also c o n t a i n s the h y d r a u l i c p o w e r p a c k s for t h e m a c h i n e a n d t h e i n j e c t i o n u n i t . E a c h p r e s s is e q u i p p e d with a injection m o u l d i n g a n d m a t e r i a l feed system, an a u t o m a t e d u n l o a d ing r o b o t a n d a n a u t o m a t e d m o u l d h a n d l i n g system. The forces a r e a p p l i e d u s i n g four small s t r o k e h y d r a u l i c cylinders. T h e u n i t s f e a t u r e integral p a r a l l e l i s m c o n t r o l to deal with e c c e n t r i c loadings. This is n e c e s s a r y b e c a u s e of the s l a n t e d c o n f i g u r a t i o n of t h e h a t c h b a c k , says ACB. T h e p r e s s is c a p a b l e of injection, c o m p r e s s i o n or c o m p r e s s i o n / i n j e c tion m o u l d i n g o p e r a t i o n s . Press o p e r a t i o n is c o n t r o l l e d by t h e ACB CIMEP c o m p u t e r b a s e d system. This p r o r i d e s a g r a p h i c analysis facility w h i c h displays t h e o p e r a t i n g d a t a . A curve s h o w i n g e i t h e r t h e c u r r e n t o p e r a t i n g p r o c e s s or t h e o p e r a t i n g p a r a m e t e r s of t h e p r e s s c a n be displayed. The CIMEP s y s t e m also offers a h i s t o r i c a l r e c o r d of t h e p r e s s ' o p e r a t i o n which allows r e p e a t a b i l i t y of a p a r t i c u l a r p r o c e s s a n d h e l p s in m a c h i n e m a i n t e n a n c e . An o p e r a t o r c a n a l s o u s e C I M E P to simulate a new process and determine p a r a m e t e r s . Qualifying r u n s c a n t h e n be c a r r i e d o u t a n d t h e p a r a m e t e r s s t o r e d in the s y s t e m w h e n t h e y are optimized. C I M E P is a real t i m e m o n i t o r i n g a n d c o n t r o l system, says ACB. As well as t h e h a t c h b a c k t h e X a n t i a f e a t u r e s a c o m p o s i t e t e c h n i c a l front-end. This r e p l a c e s an a s s e m b l y of several m a j o r s t r u c t u r a l p a r t s in p r e v i o u s models. The
ITROEN XANTIA
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f r o n t - e n d p r o v i d e s a f r a m e w o r k for a t t a c h ing lighting e q u i p m e n t , t h e front b u m p e r , the bumper beam and the shock absorbers. The p a r t weighs 3.9 kg a n d is m o u l d e d by I n o p l a s t of F r a n c e using low s h r i n k s h e e t m o u l d i n g c o m p o u n d (SMC) f r o m Mauves C o m p o s i t e s reinforced with 28% of OwensC o r n i n g ' s R07EX1 roving. I n o p l a s t says t h a t it is c u r r e n t l y m a k i n g a r o u n d 900 f r o n t - e n d s a day; full c a p a c i t y is 1300. Citroi!n selected I n o p l a s t to m o u l d the p a r t b e c a u s e of the firm's p r e v i o u s e x p e r i e n c e on s i m i l a r c o m p o n e n t s for t h e C i t r o e n XM, Volvo 850, P e u g e o t 405 a n d R e n a u l t Safrane. Previous SMC front-ends, such as t h a t u s e d on the P e u g e o t 405, h a v e included t h e holes to s u p p o r t t h e fan. But it is e x p e n s i v e to c u t o u t t h e s e h o l e s a s a f i n i s h i n g o p e r a t i o n , G e r a r d told Reinforced Plastics. The s o l u t i o n Citroi!n h a s a d o p t e d for t h e X a n t i a is to m a k e t h e s t r u c t u r a l l y d e m a n d ing f r o n t - e n d f r o m SMC, with t h e p a n e l which s u p p o r t s t h e v e n t i l a t o r a n d v e n t i l a t o r
R E I N F O R C E D P L A S T I C S ,JUNE 1 9 9 3
Schematic diagram showing the major composite parts in the Xantia.
Inoplast moulds the SMC technical frontend. A reinforced polyimide fan support is used on this model.
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ITROEN
XANTIA
m o t o r b e i n g m a d e f r o m 30% glass fibre r e i n f o r c e d polyimide. In t h e longer t e r m , G e r a r d believes t h a t it m a y be p o s s i b l e to injection m o u l d BMC f r o n t - e n d s in t h e s a m e w a y t h a t h a t c h b a c k s a r e c u r r e n t l y m a d e . The p r o b l e m w i t h t h i s is t h e d i f f i c u l t l y in p r e d i c t i n g flow of t h e c o m p o u n d a n d t h e n e e d to c o n s t a n t l y r e - e n g i n e e r t h e injection tool to a c h i e v e a p a r t with t h e specified d i m e n s i o n s . It will be m o r e t h a n five y e a r s b e f o r e s u c h t e c h n o l o g y a p p e a r s on t h e m a r k e t , he says, b u t w h e n it is a v a i l a b l e it will p e r m i t t h e e c o n o m i c a l m a n u f a c t u r e of o n e - p i e c e BMC f r o n t - e n d s with t h e holes i n c o r p o r a t e d a t t h e m a n u f a c t u r i n g stage. T h e u s e of p o l y p r o p y l e n e b a s e d glass m a t t h e r m o p l a s t i c (GMT) for t h e f r o n t - e n d w a s also a possibility. A p a r t of t h i s type is a l r e a d y u s e d on t h e VW Golf A3. However, SMC h a s b e t t e r d i m e n s i o n a l s t a b i l i t y t h a n GMT. T h i s m e a n s t h a t it is p o s s i b l e to a c c u r a t e l y p o s i t i o n t h e wings of t h e c a r by fixing t h e m to t h e f r o n t - e n d . W h e r e GMT f r o n t - e n d s a r e u s e d t h e wings m u s t be fixed to a steel b e a m r u n n i n g a c r o s s t h e f r o n t of t h e c a r . P r o d u c t i o n v o l u m e is a l s o a c o n s i d e r a t i o n -- GMT is a m o r e e c o n o m i c a l p r o c e s s for high v o l u m e s a n d five t i m e s as m a n y Golfs a r e built as Xantias. T h e f a s t e n i n g s u s e d on t h e f r o n t - e n d a r e Rivkle blind n u t rivet f r o m Otalu SA. T h e s e p r o v i d e a precision, high s t r e n g t h t h r e a d in t h i n - w a l l e d c o m p o n e n t s , says t h e firm. A l t h o u g h C i t r o e n c l a i m s t h a t it h a s a
REINFORCED PLASTICS JUNE 1993
c o m m i t m e n t to using c o m p o s i t e p a r t s on c u r r e n t a n d f u t u r e m o d e l s of its cars t h e SMC b o n n e t on t h e BX h a s b e e n d r o p p e d in f a v o u r of m e t a l one on t h e Xantia. C u r r e n t E u r o p e a n t e c h n o l o g y for SMC p r o c e s s i n g w o u l d h a v e m a d e a n SMC b o n n e t uneconomic, says Gerard. If a one piece b o n n e t is u s e d ribs a r e r e q u i r e d for stiffness. However, i n - m o u l d c o a t i n g s c a n n o t be u s e d w i t h r i b b e d p a r t s . The r e s u l t i n g p a r t h a s signific a n t p o r o s i t y a n d t h e a m o u n t of rework n e e d e d m a k e s it u n e c o n o m i c for m e d i u m high v o l u m e cars. If a t e c h n o l o g y can be found which eliminates the porosity then SMC b o n n e t s m a y a g a i n b e c o m e feasible. In t h e USA, B u d d is u s i n g v a c u u m technology for both compounding and m o u l d i n g of SMC. The p a s t e is m i x e d a n d t h e n a v a c u u m a p p l i e d to get rid of air i n t r o d u c e d by t h e filler. During the m o u l d i n g o p e r a t i o n t h e tool is e v a c u a t e d w h e n seiniclosed to s u c k t h e air o u t of t h e c o m p o u n d . The tool is t h e n fully closed a n d t h e SMC can m o v e s m o r e easily. The t e c h n o l o g y u s e d by B u d d w a s d e v e l o p e d by O w e n s - C o r n i n g in t h e early 1980's says Gerard. T h e u s e of t h e r m o s e t c o m p o s i t e s in cars h a s c o m e u n d e r t h r e a t in t h e p a s t few years, mainly stemming from concerns about recycling. Citro~n's c o n t i n u e d e n t h u s i a s m for BMC a n d SMC in a r e a s w h e r e t h e y can offer m a n u f a c t u r i n g a n d e c o n o m i c a d v a n t a g e s is a b a d l y n e e d e d b o o s t for t h e a u t o m o t i v e c o m p o s i t e s sector. •
Xantia provides a b o o s t for automotive c o m p o s i t e s Citroi!n l e a d s E u r o p e ' s m o t o r i n d u s t r y in t h e u s e o f c o m p o s i t e s in m a s s p r o d u c t i o n cars a n d its l a t e s t m o d e l t h e X a n t i a is n o e x c e p t i o n . Like its p r e d e c e s sor, t h e BX, it f e a t u r e s an i n j e c t i o n m o u l d e d BMC h a t c h b a c k . T h e r e is a l s o a t w o p a r t f r o n t - e n d c o m p r i s i n g SMC a n d g l a s s r e i n f o r c e d p o l y i m i d e , a n d a c o m b i n e d c y l i n d e r h e a d c o v e r a n d air filter. As a f u r t h e r r e a f f i r m a t i o n o f its b e l i e f in c o m p o s i t e s Citroi!n h a s i n v e s t e d in f a c i l i t i e s to e n a b l e it to m a k e m a n y o f t h e parts i n - h o u s e .
he Xantia is aimed at the top end of the medium-size saloon cat" m a r k e t which, Citroen says, a c c o u n t s for more t h a n 20% of all car sales. The c o m p a n y plans to p r o d u c e 180 000 Xantias in 1993, 45% of which are destined for the French market. P r o d u c t i o n of the vehicle began at Citro~n's p l a n t in Rennes-la-Janais, France, in December 1992 and the car was l a u n c h e d across E u r o p e four m o n t h s later. A m a j o r c h a n g e in the p r o d u c t i o n of the Xantia is Citro~n's decision to make m a n y of the c o m p o s i t e p a r t s in its own factories r a t h e r t h a n use external moulders. It has invested in a new p r o d u c t i o n unit capable of m a k i n g 1200 h a t c h b a c k s a day and a bulk
T
Two pieces of the Xantia's hatchback are moulded inhouse by Citroen, Manducher makes the window frame.
:(
R E I N F O R C E D PLASTICS J U N E 1 9 9 3
moulding c o m p o u n d (BMC) machine capable of making one tonne of c o m p o u n d an hour. The Xantia h a t c h b a c k weighs 15 kg and is m o u l d e d in t h r e e p a r t s - an internal r e i n f o r c e m e n t panel, an e x t e r n a l lower panel and the rear window f r a m e . The first two p a r t s are m a d e by CitroSn. French m o u l d e r M a n d u c h e r , w h i c h m o u l d s the h a t c h b a c k for the CitroSn ZX model, fabricates the window frame. The process used to mould the h a t c h b a c k is the so-called IMBMC technique developed by Owens-Corning and M a n d u c h e r for the two piece ZX hatchback. For the larger Xantia the runs were too long to m o u l d in two pieces so the outer moulding was split, says Jacques Gerard of Owens-Corning. The join in the two sections of the exterior moulding is hidden by the rear window glass. The 1.2 kg window frame p a r t is made by M a n d u e h e r in its Pouranc~ plant. The PE7 BMC is c o m p o u n d e d by Manducher with 18% of Owens-Corning's R63SX3 roving as re i n f o r c e m e n t . The p a r t is m o u l d e d in a 900 t o n n e clamping press which includes a special a u t o m a t i c unit to c u t gates and preserve the geometry of the part during cooling. Manducher says t h a t it is currently making a r o u n d 1000 window frames a day; m a x i m u m capacity is 1450. The resin used for the BMC h a t c h b a c k is Disitron 2708 o r t h o p h t h a l i c u n s a t u r a t e d polyester from Alusuisse Italia. This is the same grade used in the Citroen AX and BX model hatchbacks. When the Disitron resin is combined with low profile additives from Union Carbide an excellent surface finish can be obtained, says Alusuisse. A p a r t direct from the press reveals no porosity and no show through. Alusuisse told Reinforced Plastics t h a t Disitron is the only polyester specified for use in Citroen h a t c h b a c k s -- in spite of having a higher price than many competitive resins. The reason for its choice, says the firm, is the consistent high quality it is able to offer. The resin is p r o d u c e d in 25 tonne lots u n d e r ISO 9002 conditions to a very tight specification. Alusuisse is a completely
0034 36179:]$6.00
( ' 1993, Elsex~ier S c i e n c e P u b l i s h e r s Ltd.
C i n t e g r a t e d p r o d u c e r of u n s a t u r a t e d p o l y e s t e r with its own m a l e i c a n h y d r i d e facility (see I n d u s t r y News). T h e injection m o u l d i n g p r e s s e s u s e d by C i t r o e n to m a k e t h e h a t c h b a c k i n n e r a n d lower e x t e r i o r p a r t s are built by ACB Loire. Two of t h e firm's M C P / F C P 2000 p r e s s e s h a v e b e e n i n s t a l l e d in t h e c a r m a k e r ' s Rennes factory. T h r e e s i m i l a r p r e s s e s are u s e d by M a n d u c h e r a n d I n e r g a of S p a i n to m a k e t h e ZX h a t c h b a c k . ACB says t h a t C i t r o e n c h o s e to use its p r e s s e s f o r t h r e e r e a s o n s : to c o n s e r v e i n t e r n a l know-how, to d e v e l o p its u n d e r s t a n d i n g of t h e f a b r i c a t i o n of BMC, a n d to gain a m a s t e r y of t h e m o u l d i n g of t h e r m o sets. The two p r e s s e s installed at Citro~ a r e c a p a b l e of p r o d u c i n g 1250 u n i t s a day, working on a three shift system. The m a c h i n e s h a v e a vertical f o r m a t r a t h e r t h a n t h e m o r e c o n v e n t i o n a l layout. This gives access f r o m b o t h sides of t h e p r e s s as well as r e d u c i n g t h e floor s p a c e required. The p r e s s e s a r e set into a p i t w h i c h also c o n t a i n s the h y d r a u l i c p o w e r p a c k s for t h e m a c h i n e a n d t h e i n j e c t i o n u n i t . E a c h p r e s s is e q u i p p e d with a injection m o u l d i n g a n d m a t e r i a l feed system, an a u t o m a t e d u n l o a d ing r o b o t a n d a n a u t o m a t e d m o u l d h a n d l i n g system. The forces a r e a p p l i e d u s i n g four small s t r o k e h y d r a u l i c cylinders. T h e u n i t s f e a t u r e integral p a r a l l e l i s m c o n t r o l to deal with e c c e n t r i c loadings. This is n e c e s s a r y b e c a u s e of the s l a n t e d c o n f i g u r a t i o n of t h e h a t c h b a c k , says ACB. T h e p r e s s is c a p a b l e of injection, c o m p r e s s i o n or c o m p r e s s i o n / i n j e c tion m o u l d i n g o p e r a t i o n s . Press o p e r a t i o n is c o n t r o l l e d by t h e ACB CIMEP c o m p u t e r b a s e d system. This p r o r i d e s a g r a p h i c analysis facility w h i c h displays t h e o p e r a t i n g d a t a . A curve s h o w i n g e i t h e r t h e c u r r e n t o p e r a t i n g p r o c e s s or t h e o p e r a t i n g p a r a m e t e r s of t h e p r e s s c a n be displayed. The CIMEP s y s t e m also offers a h i s t o r i c a l r e c o r d of t h e p r e s s ' o p e r a t i o n which allows r e p e a t a b i l i t y of a p a r t i c u l a r p r o c e s s a n d h e l p s in m a c h i n e m a i n t e n a n c e . An o p e r a t o r c a n a l s o u s e C I M E P to simulate a new process and determine p a r a m e t e r s . Qualifying r u n s c a n t h e n be c a r r i e d o u t a n d t h e p a r a m e t e r s s t o r e d in the s y s t e m w h e n t h e y are optimized. C I M E P is a real t i m e m o n i t o r i n g a n d c o n t r o l system, says ACB. As well as t h e h a t c h b a c k t h e X a n t i a f e a t u r e s a c o m p o s i t e t e c h n i c a l front-end. This r e p l a c e s an a s s e m b l y of several m a j o r s t r u c t u r a l p a r t s in p r e v i o u s models. The
ITROEN XANTIA
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f r o n t - e n d p r o v i d e s a f r a m e w o r k for a t t a c h ing lighting e q u i p m e n t , t h e front b u m p e r , the bumper beam and the shock absorbers. The p a r t weighs 3.9 kg a n d is m o u l d e d by I n o p l a s t of F r a n c e using low s h r i n k s h e e t m o u l d i n g c o m p o u n d (SMC) f r o m Mauves C o m p o s i t e s reinforced with 28% of OwensC o r n i n g ' s R07EX1 roving. I n o p l a s t says t h a t it is c u r r e n t l y m a k i n g a r o u n d 900 f r o n t - e n d s a day; full c a p a c i t y is 1300. Citroi!n selected I n o p l a s t to m o u l d the p a r t b e c a u s e of the firm's p r e v i o u s e x p e r i e n c e on s i m i l a r c o m p o n e n t s for t h e C i t r o e n XM, Volvo 850, P e u g e o t 405 a n d R e n a u l t Safrane. Previous SMC front-ends, such as t h a t u s e d on the P e u g e o t 405, h a v e included t h e holes to s u p p o r t t h e fan. But it is e x p e n s i v e to c u t o u t t h e s e h o l e s a s a f i n i s h i n g o p e r a t i o n , G e r a r d told Reinforced Plastics. The s o l u t i o n Citroi!n h a s a d o p t e d for t h e X a n t i a is to m a k e t h e s t r u c t u r a l l y d e m a n d ing f r o n t - e n d f r o m SMC, with t h e p a n e l which s u p p o r t s t h e v e n t i l a t o r a n d v e n t i l a t o r
R E I N F O R C E D P L A S T I C S ,JUNE 1 9 9 3
Schematic diagram showing the major composite parts in the Xantia.
Inoplast moulds the SMC technical frontend. A reinforced polyimide fan support is used on this model.
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ITROEN
XANTIA
m o t o r b e i n g m a d e f r o m 30% glass fibre r e i n f o r c e d polyimide. In t h e longer t e r m , G e r a r d believes t h a t it m a y be p o s s i b l e to injection m o u l d BMC f r o n t - e n d s in t h e s a m e w a y t h a t h a t c h b a c k s a r e c u r r e n t l y m a d e . The p r o b l e m w i t h t h i s is t h e d i f f i c u l t l y in p r e d i c t i n g flow of t h e c o m p o u n d a n d t h e n e e d to c o n s t a n t l y r e - e n g i n e e r t h e injection tool to a c h i e v e a p a r t with t h e specified d i m e n s i o n s . It will be m o r e t h a n five y e a r s b e f o r e s u c h t e c h n o l o g y a p p e a r s on t h e m a r k e t , he says, b u t w h e n it is a v a i l a b l e it will p e r m i t t h e e c o n o m i c a l m a n u f a c t u r e of o n e - p i e c e BMC f r o n t - e n d s with t h e holes i n c o r p o r a t e d a t t h e m a n u f a c t u r i n g stage. T h e u s e of p o l y p r o p y l e n e b a s e d glass m a t t h e r m o p l a s t i c (GMT) for t h e f r o n t - e n d w a s also a possibility. A p a r t of t h i s type is a l r e a d y u s e d on t h e VW Golf A3. However, SMC h a s b e t t e r d i m e n s i o n a l s t a b i l i t y t h a n GMT. T h i s m e a n s t h a t it is p o s s i b l e to a c c u r a t e l y p o s i t i o n t h e wings of t h e c a r by fixing t h e m to t h e f r o n t - e n d . W h e r e GMT f r o n t - e n d s a r e u s e d t h e wings m u s t be fixed to a steel b e a m r u n n i n g a c r o s s t h e f r o n t of t h e c a r . P r o d u c t i o n v o l u m e is a l s o a c o n s i d e r a t i o n -- GMT is a m o r e e c o n o m i c a l p r o c e s s for high v o l u m e s a n d five t i m e s as m a n y Golfs a r e built as Xantias. T h e f a s t e n i n g s u s e d on t h e f r o n t - e n d a r e Rivkle blind n u t rivet f r o m Otalu SA. T h e s e p r o v i d e a precision, high s t r e n g t h t h r e a d in t h i n - w a l l e d c o m p o n e n t s , says t h e firm. A l t h o u g h C i t r o e n c l a i m s t h a t it h a s a
REINFORCED PLASTICS JUNE 1993
c o m m i t m e n t to using c o m p o s i t e p a r t s on c u r r e n t a n d f u t u r e m o d e l s of its cars t h e SMC b o n n e t on t h e BX h a s b e e n d r o p p e d in f a v o u r of m e t a l one on t h e Xantia. C u r r e n t E u r o p e a n t e c h n o l o g y for SMC p r o c e s s i n g w o u l d h a v e m a d e a n SMC b o n n e t uneconomic, says Gerard. If a one piece b o n n e t is u s e d ribs a r e r e q u i r e d for stiffness. However, i n - m o u l d c o a t i n g s c a n n o t be u s e d w i t h r i b b e d p a r t s . The r e s u l t i n g p a r t h a s signific a n t p o r o s i t y a n d t h e a m o u n t of rework n e e d e d m a k e s it u n e c o n o m i c for m e d i u m high v o l u m e cars. If a t e c h n o l o g y can be found which eliminates the porosity then SMC b o n n e t s m a y a g a i n b e c o m e feasible. In t h e USA, B u d d is u s i n g v a c u u m technology for both compounding and m o u l d i n g of SMC. The p a s t e is m i x e d a n d t h e n a v a c u u m a p p l i e d to get rid of air i n t r o d u c e d by t h e filler. During the m o u l d i n g o p e r a t i o n t h e tool is e v a c u a t e d w h e n seiniclosed to s u c k t h e air o u t of t h e c o m p o u n d . The tool is t h e n fully closed a n d t h e SMC can m o v e s m o r e easily. The t e c h n o l o g y u s e d by B u d d w a s d e v e l o p e d by O w e n s - C o r n i n g in t h e early 1980's says Gerard. T h e u s e of t h e r m o s e t c o m p o s i t e s in cars h a s c o m e u n d e r t h r e a t in t h e p a s t few years, mainly stemming from concerns about recycling. Citro~n's c o n t i n u e d e n t h u s i a s m for BMC a n d SMC in a r e a s w h e r e t h e y can offer m a n u f a c t u r i n g a n d e c o n o m i c a d v a n t a g e s is a b a d l y n e e d e d b o o s t for t h e a u t o m o t i v e c o m p o s i t e s sector. •