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SHW tackles PM's complex challenges
SHW tackles PM's complex challenges S H W c l a i m s to b e t h e w o r l d ' s o l d e s t i n d u s t r i a l c o m p a n y . It w a s a w a r d e d m i n i n g rights in B a d e n W ~ r t t e m b e r g in 1 3 6 5 . T o d a y t h e s t a t e still o w n s h a l f the c o m p a n y , t h e o t h e r h a l f b e l o n g s to M A N A G . T h e P M division fits w e l l w i t h S H W ' s o t h e r m a n u f a c t u r ing activities r a n g i n g f r o m c a s t p a r t s a n d m a c h i n e tools, t h r o u g h to h y d r a u l i c p u m p s . A m a n d a W e a v e r visited W a s s e r a l f i n g e n to s e e h o w S H W is f a c i n g u p to t h e 1 9 9 0 s .
S
This pulley with a 'nose' is for a GM six cylinder engine.
42 MPR December 1994
chwfibische Hfittenwerke (SHW) is a diversified group m a k i n g m a c h i n e tools, o p e r a t i n g e q u i p m e n t , process a n d e n g i n e e r i n g systems, rolls a n d drum, chill castings, cast parts, bright steel, shafts for hydraulic applications, brake disks a n d h y d r a u l i c p u m p s . It s t a r t e d p r o d u c i n g powder m e t a l l u r g y (PM) p a r t s on a small scale in the 1960s as p a r t of a drive to investigate new technologies which offered p r o m i s i n g o p p o r t u n i t i e s . But its real interest in PM did n o t come u n t i l t e n years later w h e n it b r o u g h t t h e PM a c t i v i t i e s of Demag, i n c l u d i n g the firm's e x i s t i n g p a r t s a n d customers. T h e PM d i v i s i o n n o w s e l l s s o m e DM35 million's worth of PM p a r t s each year a n d employs a r o u n d 200 people. Like m a n y of its c o m p e t i t o r s SHW has decided t h a t the way to succeed in the
G e r m a n PlY[ i n d u s t r y is to focus on specific types a n d families of parts. A strategy t h a t has been u n d e r d e v e l o p m e n t since 1990 w h e n c u r r e n t g e n e r a l m a n a g e r Michael Krehl j o i n e d the company. The m a i n family of p a r t s is the Duocentric a n d Trochocentric oil p u m p gears for which SHW owns the p a t e n t s . These offer less p u l s a t i o n , r e d u c e d losses in delivery, lower n o i s e a n d a g r e a t e r f r e e d o m in working tolerances, t h a n c o n v e n t i o n a l gyroc e n t r i c a n d i n v o l u t e gears. SHW m a k e s between 160 000 a n d 200 000 sets of gears a m o n t h , a c c o u n t i n g for 25% of its total turnover. Some 10% of these are c u r r e n t l y s u p p l i e d to SHW's hydraulic p u m p division for i n c l u s i o n in oil p u m p s , w h i l e t h e r e m a i n i n g 90% a r e sold o n t h e o p e n market. But this s i t u a t i o n is changing, says Krehl, car makers are increasingly buying-in complete oil p u m p a s s e m b l i e s from outside, r a t h e r t h a n b u i l d i n g t h e m in-house. SHW therefore expects to s u p p l y more gear sets to its sister division in the future. J o i n i n g of PM p a r t s to each o t h e r or to c o n v e n t i o n a l l y formed p a r t s u s i n g capacitor discharge welding is also a n SHW speciality. It is used to make p a r t s such as a steering c o l u m n lock used on all BMW models. Two high s t r e n g t h PM p a r t s are j o i n e d to form the lock, which has 7% e l o n g a t i o n a n d a tensile s t r e n g t h of 700 N / m m 2. The welded joint, which is achieved w i t h o u t a n y h e a t i n g of the part, can w i t h s t a n d 500 Nm torque. SHW m a k e s 600 000 of the locks each year. Welding is also used in the fabrication of stainless steel bosses for fixing rear view mirrors to car windscreens. "We are the only m a n u f a c t u r e r to j o i n o u r two piece m i r r o r bosses by welding," says Krehl, "the p e r m a n e n t n a t u r e of the j o i n t m e a n s t h a t they c a n n o t work loose." One of SHW's welded p r o d u c t s is also a crossover into a n o t h e r of the group's target areas: cam phasers. Krehl says t h a t m o d e r n car engines are required to have a s m o o t h t o r q u e curve with high t o r q u e available at a wide b a n d of r e v o l u t i o n s / m i n u t e (RPM). To achieve this the drive pulley has to be t i m e d relative to the crankshaft, which allows v a r i a t i o n in the valve o p e n i n g a n d closing times relative to the c r a n k s h a f t rotation. This is done u s i n g cam phasers. Krehl told us t h a t t h e r e are several different cam p h a s e r systems c u r r e n t l y in use in Europe,
0026-0657/94/$7.00 © 1994, Elsevier Science Ltd.
GERMAN
most of which are based on helical gears. Up to now m a c h i n e d steel p a r t s have been used b u t PM is now s t a r t i n g to p e n e t r a t e this market. "PM allows the p r o d u c t i o n of cam p h a s e r parts with the same properties as m a c h i n e d versions b u t u p to 50% cheaper," says Krehl. The two piece welded cam p h a s e r SHW currently makes c o m b i n e s a sintered base with a solid steel ring to give a semifinished c o m p o n e n t . The c u s t o m e r t h e n m a c h i n e s a helical tooth form on the i n n e r a n d o u t e r of the part. "But", says Krehl, "we p l a n to press in a helical t o o t h form into the sintered p a r t in the n e a r future." Krehl also sees the d e v e l o p m e n t of high s t r e n g t h materials with good e l o n g a t i o n o p e n i n g u p new a p p l i c a t i o n s for PM. He says t h a t SHW is currently working with powder suppliers to develop these materials. He believes they will allow c o n v e n t i o n a l pressed a n d sintered p a r t s to break into areas previously d o m i n a t e d by forged parts, such as b e a r i n g caps, t r a n s m i s s i o n gears a n d con-rods. "The new powders will make such p a r t s possible," he says, "they will be b e t t e r a n d c h e a p e r t h a n c o m p e t i n g products such as powder forged parts." Krehl's view is t h a t pressed a n d sintered c o n n e c t i n g rods which have been direct h a r d e n e d in the s i n t e r i n g furnace, b u t n o t given any a d d i t i o n a l heat t r e a t m e n t , will be feasible for all types of a u t o m o t i v e engines. Initial a p p l i c a t i o n s are likely to be in lower p e r f o r m a n c e s engines. He also says t h a t the p r e s s i n g a n d s i n t e r i n g of helical gears u s i n g new high s t r e n g t h m a t e r i a l s is possible. SHW is currently working on a prototype part, he told us, a n d the first pilot p r o d u c t i o n p a r t s will be developed in 1995. The c o m p o n e n t u n d e r d e v e l o p m e n t is a n o t h e r cam p h a s e r with a n i n t e r n a l helical gear. PM t r a n s m i s sion gears will also be a reality for b o t h m a n u a l a n d a u t o m a t i c t r a n s m i s s i o n s , he believes, b u t t h e i r a p p l i c a t i o n will n o t h a p p e n in the n e a r future. "There are lots of other a p p l i c a t i o n s for PM to c o n q u e r before driving gears are attained," he says. "SHW is a l r e a d y w o r k i n g on t h e first a p p l i c a t i o n s in this area. For i n s t a n c e if drive shafts could be a s s e m b l e d u s i n g PM gears, in a similar m a n n e r to camshafts, the cost savings would be enormous. In a b o u t five years time we will be in a position to s t a r t looking at such applications." Unlike m a n y of his competitors, Krehl believes t h a t PM b e a r i n g caps c a n be p r o d u c e d e c o n o m i c a l l y in E u r o p e . The E u r o p e a n d e m a n d is for high p e r f o r m a n c e engines a n d the b e a r i n g caps are m u c h more complicated t h a n the versions used in the USA a n d require very different properties, he told us. Bearing caps for high performance engines with c o m p l e x caps
PM
SPOTLIGHT
%.,
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This pulley with protrusions for operating an engine management system is typical of the complex parts SHW specializes in.
SHW joins PM parts using capacitor discharge welding.
n e e d i n g high m e c h a n i c a l properties a n d high d i m e n s i o n a l r e q u i r e m e n t s will be an i n t e r e s t i n g business, he believes. SHW also sees safety c o m p o n e n t s for cars as a growing area for high s t r e n g t h PM parts. The c o m p a n y is already m a k i n g a p a r t to ignite the t e n s i o n e r for a seat belt in the event of crash. The t e n s i o n e r is held by a lock which is released in the impact. The r a d i u s of the p a r t which does this defines the time t a k e n to trigger the belt tensioner. S t a m p i n g w a s u n a b l e to p r o d u c e t h e
MPR December 1994 43
Two piece m i r r o r bosses are also welded together.
required r a d i u s b u t PM p e r m i t s the s h a p e to be m a d e accurately. With 2-4 such p a r t s a car this is big area in the future, says Krehl. Krehl believes t h a t c o n c e n t r a t i n g on high s t r e n g t h m a t e r i a l s is the only way for the G e r m a n PM i n d u s t r y to stay a h e a d of other c o u n t r i e s with lower l a b o u r costs. "Although G e r m a n y has high m a n u f a c t u r ing costs the i n d u s t r y also has good knowledge of the PM process," he says. "To be successful in PM we m u s t make use of t h a t knowledge, either by p r o d u c i n g c o m p l e x p a r t s from special m a t e r i a l s or by concent r a t i n g on m e e t i n g high tolerance levels. Low technology p a r t s are already m a d e outside G e r m a n y in c o u n t r i e s with lower costs, w h e n high s t r e n g t h m a t e r i a l s become
widely available simple parts made from t h e m will rapidly follow suit." Almost all SHW's n e w p a r t s have ' s o m e t h i n g special' a b o u t them. Krehl believes t h a t s u c h a s t r a t e g y is t h e o n l y w a y t o g u a r a n t e e survival. SHW's belief t h a t m a k i n g c o m p l e x p a r t s is the best strategy for the future often leads it to a t t e m p t p a r t s other PM c o m p a n i e s have failed to make or rejected. The seat belt t e n s i o n e r release was one such p a r t a n d a p u l l e y for a G M / L o t u s e n g i n e m a n a g e m e n t system is another. The pulley features a four projections at 90 ° from one surface, each projection is a r o u n d 50 m m long, 5-10 m m wide a n d a b o u t 3 m m thick. In spite of Krehl's concerns a b o u t the cost of PM p r o d u c t i o n in G e r m a n y he is optimistic a b o u t the future. Especially with regard to p a r t s for the a u t o m o t i v e sector, which a c c o u n t s for 85% of SHW's business. F o u r of SHW's five m a j o r c u s t o m e r s are automotive: BMW, VW, Opel, Mercedes. The only m a j o r n o n - a u t o m o t i v e c u s t o m e r is a Swiss s u b s i d i a r y of Bosch. A u t o m o t i v e PM p a r t s are the m o s t c o m p l e x a n d challenging, he says, b u t PM's ability to replace t r a d i t i o n a l m a t e r i a l s more economically has seen it c o n t i n u e to grow even w h e n the a u t o m o t i v e m a r k e t is static. He expects the PM i n d u s t r y to grow a r o u n d 5% a year over the n e x t few years a n d says t h a t SHW's d e v e l o p m e n t will be in-line with this. However, he agrees with m a n y of his rivals t h a t the G e r m a n PM i n d u s t r y has too m u c h capacity. "Many of the c o m p a n i e s are too small to s u p p o r t the activities needed for c o m p o n e n t s u p p l i e r s such as sales a n d development," he told us. "This s i t u a t i o n of overcapacity c o u p l e d with lots of small c o m p a n i e s leads to poor prices for the p a r t s . " K r e h l e x p e c t s to see m e r g e r s between some of the G e r m a n PM p a r t s makers a n d says t h a t SHW is in discussion with o t h e r PM c o m p a n i e s a b o u t possible j o i n t ventures.
PM part production at Wasseralfingen
SHW believes automotive safety parts such as this one will be important in the future.
44 MPR December 1994
SHW uses a r o u n d 2000-2500 t o n n e s of powder a year. A r o u n d 70% of this comes from HSganiis a n d the r e m a i n d e r from M a n n e s m a n n , says Krehl. The c o m p a n y finds it both b e t t e r a n d c h e a p e r to buy its powder p r e m i x e d a n d there are no longer any i n - h o u s e b l e n d i n g facilities. The tool shop is s i t u a t e d on a s e p a r a t e site in Wasseralfingen a n d makes a b o u t 50% of t h e tooling used by SHW's PM division, it also sells PM tooling externally. Krehl says t h a t this a r r a n g e m e n t offers b e t t e r flexibility. The tools are set up o u ts ide the c o m p a c t i o n presses wherever possible a n d in m o s t cases t h e r e is m o r e t h a n one
GERMAN
SHW's stainless steel capacity is being p u t to good use in a newly l a u n c h e d p r o d u c t for the diesel e n g i n e d t r u c k industry. Diesel engines have less c a r b o n m o n oxide a n d hydrocarbon emissions t h a t petrol engines, b u t they do p r o d u c e soot. SHW's Particulate Trap is able to remove soot particles from the e x h a u s t . It consists of a stainless steel wire mesh mats with stainless steel powder b o n d e d to t h e m by high t e m p e r a t u r e
a d a p t o r for each press. Compaction presses range from 15-650 t o n n e s a n d are all from Dorst. Krehl says t h a t Dorst's science a n d technology are very good. On a n u m b e r of occasions SHW has a p p r o a c h e d a c u s t o m e r in con.junction with Dorst to offer a complete package for a new part, a strategy Krehl says has been very successful. I n t e g r a t i o n of hydraulics for the a d a p t o r s is done inhouse. There are three c o m p u t e r n u m e r i cally controlled (CNC) presses; a 650 tonne, 250 t o n n e a n d 125 tonne. All three feature m u l t i - p l a t e n adaptors. At the time of our visit the 650 t o n n e press was p r o d u c i n g a pulley with a 'nose' projecting from one surface. The part, which is for an Opel sixcylinder engine built in the UK, is pressed with the projection downwards a n d t h e n flipped over by a robot d u r i n g unloading. The pulley is weighed as it leaves the press on scales t h a t control the m a c h i n e a n d stop it if there is a problem. The powder fill height is also m o n i t o r e d a n d the press a d j u s t e d to keep t h e p a r t w i t h i n t h e specification. When the part reaches the t u r n t a b l e it is d e b u r r e d before sintering. This e n a b l e d the m a c h i n i n g o p e r a t i o n s on the p a r t to be reduced to a single process to m a c h i n e the tip of the nose. Sintering capacity includes three mesh belt furnaces l¥om Mahler, Cremer a n d Elino, o p e r a t i n g at 112ffC a n d two walking beam furnaces which r u n at 1230°C. One of the walking b e a m f u r n a c e s is used for ferrous parts a n d the other is reserved for stainless steel. Most s i n t e r i n g is done in endogas, a l t h o u g h N2/H 2 mixes are used for stainless steel sintering. After s i n t e r i n g some 80% of the p a r t s go on to be sized. P r e s s e s in t h e sizing d e p a r t m e n t include a b r a n d new 800 t o n n e Gr~ibener m u l t i - s t a g e c a l i b r a t i n g system (see Metal Powder Report, October 1994). We saw a rotor for a v a c u u m p u m p being sized. The p a r t s were moving into the press automatically, p a s s i n g t h r o u g h an oil b a t h on their way in. A two step sizing o p e r a t i o n
PM
SPOTLIGHT
sintering. The c o r r u g a t e d p l a t e s axe t h e n stacked u p a n d welded a l o n g two side t o form the filter. The s t a i n l e s s Steel p o w d e r layer has a p o r o s i ~ of a r o u n d 50% with: a n average poor size of 1:00 ~m. This is sufficient to remove 90% of the soot particles. SHW h a s t e a m e d u p i With M S a c o m p a n y Specializing i n t h e retxofitting of catalytic convertors, which will m a r k e t t h e P a r t i c u l a t e Trap to t h e t r u c k retrofitting m a r k e t in Germany.
was t h e n carried out a n d the p a r t s exited a u t o m a t i c a l l y . SHW also h a s a n o l d e r 400 t o n n e version of this press. Most of the o t h e r c a l i b r a t i n g presses are m a n u a l l y o p e r a t e d a n d include a 400 t o n n e Hydrap m a c h i n e a n d a n u m b e r of 300 a n d 200 t o n n e presses. Some 70% of the coined p a r t s t h e n go on to t h e m a c h i n e shop. The m a j o r i t y of m a c h i n i n g o p e r a t i o n s are g r i n d i n g or t u r n ing. For i n s t a n c e all rotors have to be ground. A high t h r o u g h p u t is achieved by u s i n g double dish grinding. By focusing on m a k i n g the p r o d u c t i o n facilities as flexible as possible Krehl has been able to improve the economics of p a r t p r o d u c t i o n at SHV¢. A l t h o u g h the company, like most PM p a r t s makers, prefers p a r t s with v o l u m e s in excess of 50 000 a year, it says t h a t s m a l l e r n u m b e r s can be h a n d l e d economically t h a n k s to i m p r o v e m e n t s in p r o d u c t i o n flexibiliW, "This e n a b l e s us to react to orders for existing p a r t s within a few days," says Krehl. This flexibility is also d e m o n s t r a t e d in the firm's c o m m i t m e n t to getting new p a r t s into p r o d u c t i o n as quickly as possible. The lead time is n o r m a l l y four m o n t h s b u t for c o n v e n t i o n a l p a r t s can be reduced to three m o n t h s . But the u l t i m a t e test of SHW's flexibility came w h e n a car m a k e r asked it to make a c o u n t e r weight for a n e x h a u s t s~stem in j u s t eight weeks. The firm has already a n n o u n c e d the l a u n c h of a new model before the p r o b l e m was discovered, SHW m a n a g e d to meet the car m a k e r ' s target. "But," says Krehl, "there was a lot of pressure." As one of the smallest of the G e r m a n PM p a r t s m a k e r s SHW may lack the muscle of its larger rivals. But it does n o t lack the c o m m i t m e n t to m a k i n g PM p r o f i t a b l e b u s i n e s s by developing a p p l i c a t i o n s previously t h e d o m a i n of more t r a d i t i o n a l m e t a l s t e c h n o l o g i e s a n d by striving to meet the t o u g h e s t challenges t h r o w n at it by customers. 1
MPR D e c e m b e r 1994 45
S
This pulley with a 'nose' is for a GM six cylinder engine.
42 MPR December 1994
chwfibische Hfittenwerke (SHW) is a diversified group m a k i n g m a c h i n e tools, o p e r a t i n g e q u i p m e n t , process a n d e n g i n e e r i n g systems, rolls a n d drum, chill castings, cast parts, bright steel, shafts for hydraulic applications, brake disks a n d h y d r a u l i c p u m p s . It s t a r t e d p r o d u c i n g powder m e t a l l u r g y (PM) p a r t s on a small scale in the 1960s as p a r t of a drive to investigate new technologies which offered p r o m i s i n g o p p o r t u n i t i e s . But its real interest in PM did n o t come u n t i l t e n years later w h e n it b r o u g h t t h e PM a c t i v i t i e s of Demag, i n c l u d i n g the firm's e x i s t i n g p a r t s a n d customers. T h e PM d i v i s i o n n o w s e l l s s o m e DM35 million's worth of PM p a r t s each year a n d employs a r o u n d 200 people. Like m a n y of its c o m p e t i t o r s SHW has decided t h a t the way to succeed in the
G e r m a n PlY[ i n d u s t r y is to focus on specific types a n d families of parts. A strategy t h a t has been u n d e r d e v e l o p m e n t since 1990 w h e n c u r r e n t g e n e r a l m a n a g e r Michael Krehl j o i n e d the company. The m a i n family of p a r t s is the Duocentric a n d Trochocentric oil p u m p gears for which SHW owns the p a t e n t s . These offer less p u l s a t i o n , r e d u c e d losses in delivery, lower n o i s e a n d a g r e a t e r f r e e d o m in working tolerances, t h a n c o n v e n t i o n a l gyroc e n t r i c a n d i n v o l u t e gears. SHW m a k e s between 160 000 a n d 200 000 sets of gears a m o n t h , a c c o u n t i n g for 25% of its total turnover. Some 10% of these are c u r r e n t l y s u p p l i e d to SHW's hydraulic p u m p division for i n c l u s i o n in oil p u m p s , w h i l e t h e r e m a i n i n g 90% a r e sold o n t h e o p e n market. But this s i t u a t i o n is changing, says Krehl, car makers are increasingly buying-in complete oil p u m p a s s e m b l i e s from outside, r a t h e r t h a n b u i l d i n g t h e m in-house. SHW therefore expects to s u p p l y more gear sets to its sister division in the future. J o i n i n g of PM p a r t s to each o t h e r or to c o n v e n t i o n a l l y formed p a r t s u s i n g capacitor discharge welding is also a n SHW speciality. It is used to make p a r t s such as a steering c o l u m n lock used on all BMW models. Two high s t r e n g t h PM p a r t s are j o i n e d to form the lock, which has 7% e l o n g a t i o n a n d a tensile s t r e n g t h of 700 N / m m 2. The welded joint, which is achieved w i t h o u t a n y h e a t i n g of the part, can w i t h s t a n d 500 Nm torque. SHW m a k e s 600 000 of the locks each year. Welding is also used in the fabrication of stainless steel bosses for fixing rear view mirrors to car windscreens. "We are the only m a n u f a c t u r e r to j o i n o u r two piece m i r r o r bosses by welding," says Krehl, "the p e r m a n e n t n a t u r e of the j o i n t m e a n s t h a t they c a n n o t work loose." One of SHW's welded p r o d u c t s is also a crossover into a n o t h e r of the group's target areas: cam phasers. Krehl says t h a t m o d e r n car engines are required to have a s m o o t h t o r q u e curve with high t o r q u e available at a wide b a n d of r e v o l u t i o n s / m i n u t e (RPM). To achieve this the drive pulley has to be t i m e d relative to the crankshaft, which allows v a r i a t i o n in the valve o p e n i n g a n d closing times relative to the c r a n k s h a f t rotation. This is done u s i n g cam phasers. Krehl told us t h a t t h e r e are several different cam p h a s e r systems c u r r e n t l y in use in Europe,
0026-0657/94/$7.00 © 1994, Elsevier Science Ltd.
GERMAN
most of which are based on helical gears. Up to now m a c h i n e d steel p a r t s have been used b u t PM is now s t a r t i n g to p e n e t r a t e this market. "PM allows the p r o d u c t i o n of cam p h a s e r parts with the same properties as m a c h i n e d versions b u t u p to 50% cheaper," says Krehl. The two piece welded cam p h a s e r SHW currently makes c o m b i n e s a sintered base with a solid steel ring to give a semifinished c o m p o n e n t . The c u s t o m e r t h e n m a c h i n e s a helical tooth form on the i n n e r a n d o u t e r of the part. "But", says Krehl, "we p l a n to press in a helical t o o t h form into the sintered p a r t in the n e a r future." Krehl also sees the d e v e l o p m e n t of high s t r e n g t h materials with good e l o n g a t i o n o p e n i n g u p new a p p l i c a t i o n s for PM. He says t h a t SHW is currently working with powder suppliers to develop these materials. He believes they will allow c o n v e n t i o n a l pressed a n d sintered p a r t s to break into areas previously d o m i n a t e d by forged parts, such as b e a r i n g caps, t r a n s m i s s i o n gears a n d con-rods. "The new powders will make such p a r t s possible," he says, "they will be b e t t e r a n d c h e a p e r t h a n c o m p e t i n g products such as powder forged parts." Krehl's view is t h a t pressed a n d sintered c o n n e c t i n g rods which have been direct h a r d e n e d in the s i n t e r i n g furnace, b u t n o t given any a d d i t i o n a l heat t r e a t m e n t , will be feasible for all types of a u t o m o t i v e engines. Initial a p p l i c a t i o n s are likely to be in lower p e r f o r m a n c e s engines. He also says t h a t the p r e s s i n g a n d s i n t e r i n g of helical gears u s i n g new high s t r e n g t h m a t e r i a l s is possible. SHW is currently working on a prototype part, he told us, a n d the first pilot p r o d u c t i o n p a r t s will be developed in 1995. The c o m p o n e n t u n d e r d e v e l o p m e n t is a n o t h e r cam p h a s e r with a n i n t e r n a l helical gear. PM t r a n s m i s sion gears will also be a reality for b o t h m a n u a l a n d a u t o m a t i c t r a n s m i s s i o n s , he believes, b u t t h e i r a p p l i c a t i o n will n o t h a p p e n in the n e a r future. "There are lots of other a p p l i c a t i o n s for PM to c o n q u e r before driving gears are attained," he says. "SHW is a l r e a d y w o r k i n g on t h e first a p p l i c a t i o n s in this area. For i n s t a n c e if drive shafts could be a s s e m b l e d u s i n g PM gears, in a similar m a n n e r to camshafts, the cost savings would be enormous. In a b o u t five years time we will be in a position to s t a r t looking at such applications." Unlike m a n y of his competitors, Krehl believes t h a t PM b e a r i n g caps c a n be p r o d u c e d e c o n o m i c a l l y in E u r o p e . The E u r o p e a n d e m a n d is for high p e r f o r m a n c e engines a n d the b e a r i n g caps are m u c h more complicated t h a n the versions used in the USA a n d require very different properties, he told us. Bearing caps for high performance engines with c o m p l e x caps
PM
SPOTLIGHT
%.,
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This pulley with protrusions for operating an engine management system is typical of the complex parts SHW specializes in.
SHW joins PM parts using capacitor discharge welding.
n e e d i n g high m e c h a n i c a l properties a n d high d i m e n s i o n a l r e q u i r e m e n t s will be an i n t e r e s t i n g business, he believes. SHW also sees safety c o m p o n e n t s for cars as a growing area for high s t r e n g t h PM parts. The c o m p a n y is already m a k i n g a p a r t to ignite the t e n s i o n e r for a seat belt in the event of crash. The t e n s i o n e r is held by a lock which is released in the impact. The r a d i u s of the p a r t which does this defines the time t a k e n to trigger the belt tensioner. S t a m p i n g w a s u n a b l e to p r o d u c e t h e
MPR December 1994 43
Two piece m i r r o r bosses are also welded together.
required r a d i u s b u t PM p e r m i t s the s h a p e to be m a d e accurately. With 2-4 such p a r t s a car this is big area in the future, says Krehl. Krehl believes t h a t c o n c e n t r a t i n g on high s t r e n g t h m a t e r i a l s is the only way for the G e r m a n PM i n d u s t r y to stay a h e a d of other c o u n t r i e s with lower l a b o u r costs. "Although G e r m a n y has high m a n u f a c t u r ing costs the i n d u s t r y also has good knowledge of the PM process," he says. "To be successful in PM we m u s t make use of t h a t knowledge, either by p r o d u c i n g c o m p l e x p a r t s from special m a t e r i a l s or by concent r a t i n g on m e e t i n g high tolerance levels. Low technology p a r t s are already m a d e outside G e r m a n y in c o u n t r i e s with lower costs, w h e n high s t r e n g t h m a t e r i a l s become
widely available simple parts made from t h e m will rapidly follow suit." Almost all SHW's n e w p a r t s have ' s o m e t h i n g special' a b o u t them. Krehl believes t h a t s u c h a s t r a t e g y is t h e o n l y w a y t o g u a r a n t e e survival. SHW's belief t h a t m a k i n g c o m p l e x p a r t s is the best strategy for the future often leads it to a t t e m p t p a r t s other PM c o m p a n i e s have failed to make or rejected. The seat belt t e n s i o n e r release was one such p a r t a n d a p u l l e y for a G M / L o t u s e n g i n e m a n a g e m e n t system is another. The pulley features a four projections at 90 ° from one surface, each projection is a r o u n d 50 m m long, 5-10 m m wide a n d a b o u t 3 m m thick. In spite of Krehl's concerns a b o u t the cost of PM p r o d u c t i o n in G e r m a n y he is optimistic a b o u t the future. Especially with regard to p a r t s for the a u t o m o t i v e sector, which a c c o u n t s for 85% of SHW's business. F o u r of SHW's five m a j o r c u s t o m e r s are automotive: BMW, VW, Opel, Mercedes. The only m a j o r n o n - a u t o m o t i v e c u s t o m e r is a Swiss s u b s i d i a r y of Bosch. A u t o m o t i v e PM p a r t s are the m o s t c o m p l e x a n d challenging, he says, b u t PM's ability to replace t r a d i t i o n a l m a t e r i a l s more economically has seen it c o n t i n u e to grow even w h e n the a u t o m o t i v e m a r k e t is static. He expects the PM i n d u s t r y to grow a r o u n d 5% a year over the n e x t few years a n d says t h a t SHW's d e v e l o p m e n t will be in-line with this. However, he agrees with m a n y of his rivals t h a t the G e r m a n PM i n d u s t r y has too m u c h capacity. "Many of the c o m p a n i e s are too small to s u p p o r t the activities needed for c o m p o n e n t s u p p l i e r s such as sales a n d development," he told us. "This s i t u a t i o n of overcapacity c o u p l e d with lots of small c o m p a n i e s leads to poor prices for the p a r t s . " K r e h l e x p e c t s to see m e r g e r s between some of the G e r m a n PM p a r t s makers a n d says t h a t SHW is in discussion with o t h e r PM c o m p a n i e s a b o u t possible j o i n t ventures.
PM part production at Wasseralfingen
SHW believes automotive safety parts such as this one will be important in the future.
44 MPR December 1994
SHW uses a r o u n d 2000-2500 t o n n e s of powder a year. A r o u n d 70% of this comes from HSganiis a n d the r e m a i n d e r from M a n n e s m a n n , says Krehl. The c o m p a n y finds it both b e t t e r a n d c h e a p e r to buy its powder p r e m i x e d a n d there are no longer any i n - h o u s e b l e n d i n g facilities. The tool shop is s i t u a t e d on a s e p a r a t e site in Wasseralfingen a n d makes a b o u t 50% of t h e tooling used by SHW's PM division, it also sells PM tooling externally. Krehl says t h a t this a r r a n g e m e n t offers b e t t e r flexibility. The tools are set up o u ts ide the c o m p a c t i o n presses wherever possible a n d in m o s t cases t h e r e is m o r e t h a n one
GERMAN
SHW's stainless steel capacity is being p u t to good use in a newly l a u n c h e d p r o d u c t for the diesel e n g i n e d t r u c k industry. Diesel engines have less c a r b o n m o n oxide a n d hydrocarbon emissions t h a t petrol engines, b u t they do p r o d u c e soot. SHW's Particulate Trap is able to remove soot particles from the e x h a u s t . It consists of a stainless steel wire mesh mats with stainless steel powder b o n d e d to t h e m by high t e m p e r a t u r e
a d a p t o r for each press. Compaction presses range from 15-650 t o n n e s a n d are all from Dorst. Krehl says t h a t Dorst's science a n d technology are very good. On a n u m b e r of occasions SHW has a p p r o a c h e d a c u s t o m e r in con.junction with Dorst to offer a complete package for a new part, a strategy Krehl says has been very successful. I n t e g r a t i o n of hydraulics for the a d a p t o r s is done inhouse. There are three c o m p u t e r n u m e r i cally controlled (CNC) presses; a 650 tonne, 250 t o n n e a n d 125 tonne. All three feature m u l t i - p l a t e n adaptors. At the time of our visit the 650 t o n n e press was p r o d u c i n g a pulley with a 'nose' projecting from one surface. The part, which is for an Opel sixcylinder engine built in the UK, is pressed with the projection downwards a n d t h e n flipped over by a robot d u r i n g unloading. The pulley is weighed as it leaves the press on scales t h a t control the m a c h i n e a n d stop it if there is a problem. The powder fill height is also m o n i t o r e d a n d the press a d j u s t e d to keep t h e p a r t w i t h i n t h e specification. When the part reaches the t u r n t a b l e it is d e b u r r e d before sintering. This e n a b l e d the m a c h i n i n g o p e r a t i o n s on the p a r t to be reduced to a single process to m a c h i n e the tip of the nose. Sintering capacity includes three mesh belt furnaces l¥om Mahler, Cremer a n d Elino, o p e r a t i n g at 112ffC a n d two walking beam furnaces which r u n at 1230°C. One of the walking b e a m f u r n a c e s is used for ferrous parts a n d the other is reserved for stainless steel. Most s i n t e r i n g is done in endogas, a l t h o u g h N2/H 2 mixes are used for stainless steel sintering. After s i n t e r i n g some 80% of the p a r t s go on to be sized. P r e s s e s in t h e sizing d e p a r t m e n t include a b r a n d new 800 t o n n e Gr~ibener m u l t i - s t a g e c a l i b r a t i n g system (see Metal Powder Report, October 1994). We saw a rotor for a v a c u u m p u m p being sized. The p a r t s were moving into the press automatically, p a s s i n g t h r o u g h an oil b a t h on their way in. A two step sizing o p e r a t i o n
PM
SPOTLIGHT
sintering. The c o r r u g a t e d p l a t e s axe t h e n stacked u p a n d welded a l o n g two side t o form the filter. The s t a i n l e s s Steel p o w d e r layer has a p o r o s i ~ of a r o u n d 50% with: a n average poor size of 1:00 ~m. This is sufficient to remove 90% of the soot particles. SHW h a s t e a m e d u p i With M S a c o m p a n y Specializing i n t h e retxofitting of catalytic convertors, which will m a r k e t t h e P a r t i c u l a t e Trap to t h e t r u c k retrofitting m a r k e t in Germany.
was t h e n carried out a n d the p a r t s exited a u t o m a t i c a l l y . SHW also h a s a n o l d e r 400 t o n n e version of this press. Most of the o t h e r c a l i b r a t i n g presses are m a n u a l l y o p e r a t e d a n d include a 400 t o n n e Hydrap m a c h i n e a n d a n u m b e r of 300 a n d 200 t o n n e presses. Some 70% of the coined p a r t s t h e n go on to t h e m a c h i n e shop. The m a j o r i t y of m a c h i n i n g o p e r a t i o n s are g r i n d i n g or t u r n ing. For i n s t a n c e all rotors have to be ground. A high t h r o u g h p u t is achieved by u s i n g double dish grinding. By focusing on m a k i n g the p r o d u c t i o n facilities as flexible as possible Krehl has been able to improve the economics of p a r t p r o d u c t i o n at SHV¢. A l t h o u g h the company, like most PM p a r t s makers, prefers p a r t s with v o l u m e s in excess of 50 000 a year, it says t h a t s m a l l e r n u m b e r s can be h a n d l e d economically t h a n k s to i m p r o v e m e n t s in p r o d u c t i o n flexibiliW, "This e n a b l e s us to react to orders for existing p a r t s within a few days," says Krehl. This flexibility is also d e m o n s t r a t e d in the firm's c o m m i t m e n t to getting new p a r t s into p r o d u c t i o n as quickly as possible. The lead time is n o r m a l l y four m o n t h s b u t for c o n v e n t i o n a l p a r t s can be reduced to three m o n t h s . But the u l t i m a t e test of SHW's flexibility came w h e n a car m a k e r asked it to make a c o u n t e r weight for a n e x h a u s t s~stem in j u s t eight weeks. The firm has already a n n o u n c e d the l a u n c h of a new model before the p r o b l e m was discovered, SHW m a n a g e d to meet the car m a k e r ' s target. "But," says Krehl, "there was a lot of pressure." As one of the smallest of the G e r m a n PM p a r t s m a k e r s SHW may lack the muscle of its larger rivals. But it does n o t lack the c o m m i t m e n t to m a k i n g PM p r o f i t a b l e b u s i n e s s by developing a p p l i c a t i o n s previously t h e d o m a i n of more t r a d i t i o n a l m e t a l s t e c h n o l o g i e s a n d by striving to meet the t o u g h e s t challenges t h r o w n at it by customers. 1
MPR D e c e m b e r 1994 45