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Nippon Seisen learns from its MIM experience
Nippon Seisen learns from its M IM e x p e r i e n c e N i p p o n S e i s e n i n t r o d u c e d the W i t e c M I M p r o c e s s in 1 9 8 6 , a n d h a s since m a n u f a c t u r e d a v a r i e t y o f f e r r o u s M I M parts. T h e f i r m h a s also d e v e l o p e d M I M t e c h n o l o g y for s t a i n l e s s s t e e l s y s t e m s a n d n o w makes components from FEN8 and 316L grades. T y p i c a l p a r t s i n c l u d e t h o s e for i n f o r m a t i o n p r o c e s s e q u i p m e n t , m a c h i n e tools, c a r s a n d i n d u s t r i a l robots. K a z u h i r o A s a i d e s c r i b e s h o w the c o m p a n y g u a r a n t e e s d i m e n s i o n a l p r e c i s i o n on its m a s s p r o d u c e d parts.
Material
Dimensional precision
Application
FENO (Iron 100%)
4- 0.5%
Electrical components (with magnetic properties)
FEN8 (Iron + Ni 8%)
4- 0.5%
Mechanical parts, electrical components, automotive parts
FEN42 (Iron + Ni 42%)
± 0.5%
Electrical components (with magnetic properties)
FEN46 (Iron + Ni 46%)
4- 0.5%
Electrical components (with magnetic properties)
FEN100 (Ni 100%)
_+0.5%
Electrical components
SAE4600
___ 0.5%
Mechanical parts (relating to tooling)
316L Stainless steel
4- 0.6%
Mechanical parts, electrical (electronic) parts, ornaments
17-4PH Stainless steel
4- 0.7%
Mechanical parts, electronic parts
430 Stainless steel
_+ 0.6%
Electrical components
Kovar
4- 0.5%
Electronic parts
38 MPR October 1993
M
e t a l i n j e c t i o n m o u l d i n g (MIM) p e r m i t s t h e m a s s p r o d u c t i o n of high precision, c o m p l e x s h a p e d parts. However, to achieve a c c u r a c y in a mass production situation sophisticated p r o c e s s c o n t r o l t e c h n o l o g y is r e q u i r e d . Even with this t h e t o l e r a n c e range which can be achieved is w i d e r t h a n t h a t o b t a i n e d for m a c h i n e d parts. In t e r m s of m a t e r i a l q u a l i t y MIM p a r t s c a n n o t be e x p e c t e d to m a t c h t h e u n i f o r m i t y of c o m p o n e n t s m a d e from m e c h a n i c a l l y p r o c e s s e d rolled materials. Notwithstanding these drawbacks, MIM offers t h e o p p o r t u n i t i e s for s u b s t a n tial cost r e d u c t i o n in c o m p l e x p a r t s w h e r e t h e r e q u i r e m e n t s for d i m e n s i o n a l accuracy and mechanical strength are relatively low. In seven y e a r s of MIM p r o d u c tion Nippon Seisen has gained considerable experience of the technology. FEN8 is t h e c o m p a n y ' s m o s t widely u s e d s t a i n l e s s steel g r a d e in t e r m s of weight, a l t h o u g h a greater number of parts are p r o d u c e d from 316L. The n u m b e r of p a r t s p r o d u c e d from Kovar is also increasing. The d i m e n s i o n a l a c c u r a c y guara n t e e d varies d e p e n d i n g u p o n t h e m a t e r i a l used. Table 1 shows s o m e typical values. Figure 1 shows t h e d i m e n s i o n a l v a r i a t i o n in a part. The c o m p o n e n t is m a d e from FEN8 a n d weighs some 0.3 g. The s h a p e is one which p e r m i t s d i m e n s i o n a l precision to be easily achieved. The d a t a is from nine lots of such p a r t s m a d e between A u g u s t 1989 a n d March 1992. P r o d u c t i o n q u a n t i t y p e r lot is 20 000-30 000 p a r t s a n d a m o u l d c o m p r i s i n g four u n i t s is used. The m a x i m u m v a r i a t i o n was f o u n d in Lot No. 5, w h e r e t h e value was 0.024 mm. The v a r i a t i o n between lots was 0.32 mm. Converting to a p e r c e n t a g e d e v i a t i o n shows t h a t a precision of ± 0.3% is p o s s i b l e w h e n the parts are compact articles measuring less t h a n 5 m m ~ a n d weighing u n d e r 1 g. In c o n s i d e r i n g d i m e n sions, factors such as d e f o r m a t i o n and sink are included. Factors affecting d i m e n s i o n a l a c c u r a c y include:
PM
characteristics of the metal powders a n d binders; • mixing c o n d i t i o n s for the compound; •
SPECIAL
FEATURE
Parts A, dimensional variations of H (Material: FENB) Four cavities/mould
0.30 . Parts A~
• anisotropy and homogedeviation in lot. neity of the green parts; Maximum dimensional 0.02mm (0.44%) ooo>o mm i deviation for nine lots. • residual b i n d e r q u a n t i t y 5,530 in the parts for debinding; 5,520 • the o x i d a t i o n c o n d i t i o n of lhe metal powder in 5.510 debinding; anti • the t e m p e r a t u r e increase 5.500 profile a n d a t m o s p h e r e d u r i n g sintering. 5.490 The homogeneity of green m u s t be controlled d u r i n g the m o u l d i n g process, resiI I I I I . I I I I I | ] t ! I J ! I LOT NO. t 2 3 4 5 6 7 8 9 dual binder quantity and DATE 890826 890922 EI91020 900122 910213 91:[109 911121 920218 920316 o x i d a t i o n condition of the powder are controlled durFIGURE 1: Example of dimensional deviation. ing d e b i n d i n g and the tern perature pr(,lile and a t m o s p h e r e are m a n a g e d d u r i n g sintering. facture of w.,ry large products. The largest In Nippon Seisen's experience, control in c o m p o n e n t s made by Nippon Seisen are the m o u l d i n g a n d d e b i n d i n g p r o c e s s e s 75 g for ferrous systems a n d 61 g for greatly influencq,s the ability to achieve stainless steel. To make heavier p r o d u c t s d i m e n s i o n a l stability. coarser powders with a b e t t e r d e b i n d i n g Deformation, i n c l u d i n g sink, is also of p e r f o r m a n c e would be required. i m p o r t a n c e in the m a n u f a c t u r e of MIM MIM p a r t s are susceptible to a n u m b e r p a ~ s . The delo:cmation is caused by the of defects, in m a n y cases these can be gravitational s i n t e r i n g of d e b o u n d parts. avoided at the design or processing stage. Setters can be used to prevent deformation. D i m e n s i o n a l defects in the m a i n affect large However, when small r u n s of m a n y different p a r t s a n d c o m p o n e n t s m a d e from stainless parts are I)eing produced the need for steel. Cracks are mostly caused by welding. special setters lot each part, e l i m i n a t e s any This can lead the breakage of high s t r e n g t h cost saving MIM may have made possible. p a r t s or leaks in parts used in sealing Also the use of setters does not completely applications. These critical defects can be prevent all types of deformation. Nippon p r e v e n t e d by t h o r o u g h checking d u r i n g Seisen uses a range of s t a n d a r d setters processing. which are c o m b i n e d with each other to For parts finished by plating, such as p e r m i t sintering of the various shapes being electrical parts, the trace of the gate m u s t manufac.tured. Any d e f o r m a t i o n s w h i c h be t r e a t e d a p p r o p r i a t e l y to p r e v e n t pener e m a i n can be corrected by pressing. When t r a t i o n a n d oozing of solution after plating. very high precision is needed c u t t i n g or Large voids may be formed if air is t r a p p e d d u r i n g the m o u l d i n g operation. grinding o p e r a t i o n s are performed. One of the a d v a n t a g e s of MIM c o m p a r e d These voids c a n n o t easily be detected, since with c o n v e n t i o n a l powder metallurgy (PM) t h e y are i m p o s s i b l e to see. T h e r e f o r e is its suitability lot the m a n u f a c t u r e of c o u n t e r m e a s u r e s to the f o r m a t i o n m u s t be thin walled parts. A part can be m a d e t a k e n in t e r m s of m o u l d d e s i g n a n d m o u l d i n g conditions. by MIM providing there is sufficient area Nippon Seisen has been involved at MIM to provide a gate for injection. This gives at a commercial level since the early days of a practical m i n i m u m of 0.3 m m thick, the technology. At the b i r t h of the technola l t h o u g h t h i c k n e s s differs a c c o r d i n g to ogy an exaggerated e s t i m a t i o n was m a d e of the area. When very' t h i n p l a t e s h a p e d the capabilities of MIM. Over the years this parts are made c o r r u g a t i o n s are always has evened out with MIM p r o d u c e r s a n d f o r m e d a f t e r s i n t e r i n g . T h e s e c a n be users b e c o m i n g more aware of the advancorrected by sizing. N i p p o n Seisen has tages a n d d i s a d v a n t a g e s of the technique. made p a r t s with wall thicknesses of j u s t N i p p o n Seisen believes t h a t the future for 0.2 mm in some areas. MIM lies in its use in fields where conven3'he metal powder used in the MIM tional PM a n d lost wax processes c a n n o t feedstock has an average powder d i a m e t e r easily be a p p l i e d , r a t h e r t h a n in t h e of 6-8 jam, which makes the d e b i n d i n g r e p l a c e m e n t of these processes. operation difficult and p r e v e n t s the m a n u -
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MPR October 1993 39
Material
Dimensional precision
Application
FENO (Iron 100%)
4- 0.5%
Electrical components (with magnetic properties)
FEN8 (Iron + Ni 8%)
4- 0.5%
Mechanical parts, electrical components, automotive parts
FEN42 (Iron + Ni 42%)
± 0.5%
Electrical components (with magnetic properties)
FEN46 (Iron + Ni 46%)
4- 0.5%
Electrical components (with magnetic properties)
FEN100 (Ni 100%)
_+0.5%
Electrical components
SAE4600
___ 0.5%
Mechanical parts (relating to tooling)
316L Stainless steel
4- 0.6%
Mechanical parts, electrical (electronic) parts, ornaments
17-4PH Stainless steel
4- 0.7%
Mechanical parts, electronic parts
430 Stainless steel
_+ 0.6%
Electrical components
Kovar
4- 0.5%
Electronic parts
38 MPR October 1993
M
e t a l i n j e c t i o n m o u l d i n g (MIM) p e r m i t s t h e m a s s p r o d u c t i o n of high precision, c o m p l e x s h a p e d parts. However, to achieve a c c u r a c y in a mass production situation sophisticated p r o c e s s c o n t r o l t e c h n o l o g y is r e q u i r e d . Even with this t h e t o l e r a n c e range which can be achieved is w i d e r t h a n t h a t o b t a i n e d for m a c h i n e d parts. In t e r m s of m a t e r i a l q u a l i t y MIM p a r t s c a n n o t be e x p e c t e d to m a t c h t h e u n i f o r m i t y of c o m p o n e n t s m a d e from m e c h a n i c a l l y p r o c e s s e d rolled materials. Notwithstanding these drawbacks, MIM offers t h e o p p o r t u n i t i e s for s u b s t a n tial cost r e d u c t i o n in c o m p l e x p a r t s w h e r e t h e r e q u i r e m e n t s for d i m e n s i o n a l accuracy and mechanical strength are relatively low. In seven y e a r s of MIM p r o d u c tion Nippon Seisen has gained considerable experience of the technology. FEN8 is t h e c o m p a n y ' s m o s t widely u s e d s t a i n l e s s steel g r a d e in t e r m s of weight, a l t h o u g h a greater number of parts are p r o d u c e d from 316L. The n u m b e r of p a r t s p r o d u c e d from Kovar is also increasing. The d i m e n s i o n a l a c c u r a c y guara n t e e d varies d e p e n d i n g u p o n t h e m a t e r i a l used. Table 1 shows s o m e typical values. Figure 1 shows t h e d i m e n s i o n a l v a r i a t i o n in a part. The c o m p o n e n t is m a d e from FEN8 a n d weighs some 0.3 g. The s h a p e is one which p e r m i t s d i m e n s i o n a l precision to be easily achieved. The d a t a is from nine lots of such p a r t s m a d e between A u g u s t 1989 a n d March 1992. P r o d u c t i o n q u a n t i t y p e r lot is 20 000-30 000 p a r t s a n d a m o u l d c o m p r i s i n g four u n i t s is used. The m a x i m u m v a r i a t i o n was f o u n d in Lot No. 5, w h e r e t h e value was 0.024 mm. The v a r i a t i o n between lots was 0.32 mm. Converting to a p e r c e n t a g e d e v i a t i o n shows t h a t a precision of ± 0.3% is p o s s i b l e w h e n the parts are compact articles measuring less t h a n 5 m m ~ a n d weighing u n d e r 1 g. In c o n s i d e r i n g d i m e n sions, factors such as d e f o r m a t i o n and sink are included. Factors affecting d i m e n s i o n a l a c c u r a c y include:
PM
characteristics of the metal powders a n d binders; • mixing c o n d i t i o n s for the compound; •
SPECIAL
FEATURE
Parts A, dimensional variations of H (Material: FENB) Four cavities/mould
0.30 . Parts A~
• anisotropy and homogedeviation in lot. neity of the green parts; Maximum dimensional 0.02mm (0.44%) ooo>o mm i deviation for nine lots. • residual b i n d e r q u a n t i t y 5,530 in the parts for debinding; 5,520 • the o x i d a t i o n c o n d i t i o n of lhe metal powder in 5.510 debinding; anti • the t e m p e r a t u r e increase 5.500 profile a n d a t m o s p h e r e d u r i n g sintering. 5.490 The homogeneity of green m u s t be controlled d u r i n g the m o u l d i n g process, resiI I I I I . I I I I I | ] t ! I J ! I LOT NO. t 2 3 4 5 6 7 8 9 dual binder quantity and DATE 890826 890922 EI91020 900122 910213 91:[109 911121 920218 920316 o x i d a t i o n condition of the powder are controlled durFIGURE 1: Example of dimensional deviation. ing d e b i n d i n g and the tern perature pr(,lile and a t m o s p h e r e are m a n a g e d d u r i n g sintering. facture of w.,ry large products. The largest In Nippon Seisen's experience, control in c o m p o n e n t s made by Nippon Seisen are the m o u l d i n g a n d d e b i n d i n g p r o c e s s e s 75 g for ferrous systems a n d 61 g for greatly influencq,s the ability to achieve stainless steel. To make heavier p r o d u c t s d i m e n s i o n a l stability. coarser powders with a b e t t e r d e b i n d i n g Deformation, i n c l u d i n g sink, is also of p e r f o r m a n c e would be required. i m p o r t a n c e in the m a n u f a c t u r e of MIM MIM p a r t s are susceptible to a n u m b e r p a ~ s . The delo:cmation is caused by the of defects, in m a n y cases these can be gravitational s i n t e r i n g of d e b o u n d parts. avoided at the design or processing stage. Setters can be used to prevent deformation. D i m e n s i o n a l defects in the m a i n affect large However, when small r u n s of m a n y different p a r t s a n d c o m p o n e n t s m a d e from stainless parts are I)eing produced the need for steel. Cracks are mostly caused by welding. special setters lot each part, e l i m i n a t e s any This can lead the breakage of high s t r e n g t h cost saving MIM may have made possible. p a r t s or leaks in parts used in sealing Also the use of setters does not completely applications. These critical defects can be prevent all types of deformation. Nippon p r e v e n t e d by t h o r o u g h checking d u r i n g Seisen uses a range of s t a n d a r d setters processing. which are c o m b i n e d with each other to For parts finished by plating, such as p e r m i t sintering of the various shapes being electrical parts, the trace of the gate m u s t manufac.tured. Any d e f o r m a t i o n s w h i c h be t r e a t e d a p p r o p r i a t e l y to p r e v e n t pener e m a i n can be corrected by pressing. When t r a t i o n a n d oozing of solution after plating. very high precision is needed c u t t i n g or Large voids may be formed if air is t r a p p e d d u r i n g the m o u l d i n g operation. grinding o p e r a t i o n s are performed. One of the a d v a n t a g e s of MIM c o m p a r e d These voids c a n n o t easily be detected, since with c o n v e n t i o n a l powder metallurgy (PM) t h e y are i m p o s s i b l e to see. T h e r e f o r e is its suitability lot the m a n u f a c t u r e of c o u n t e r m e a s u r e s to the f o r m a t i o n m u s t be thin walled parts. A part can be m a d e t a k e n in t e r m s of m o u l d d e s i g n a n d m o u l d i n g conditions. by MIM providing there is sufficient area Nippon Seisen has been involved at MIM to provide a gate for injection. This gives at a commercial level since the early days of a practical m i n i m u m of 0.3 m m thick, the technology. At the b i r t h of the technola l t h o u g h t h i c k n e s s differs a c c o r d i n g to ogy an exaggerated e s t i m a t i o n was m a d e of the area. When very' t h i n p l a t e s h a p e d the capabilities of MIM. Over the years this parts are made c o r r u g a t i o n s are always has evened out with MIM p r o d u c e r s a n d f o r m e d a f t e r s i n t e r i n g . T h e s e c a n be users b e c o m i n g more aware of the advancorrected by sizing. N i p p o n Seisen has tages a n d d i s a d v a n t a g e s of the technique. made p a r t s with wall thicknesses of j u s t N i p p o n Seisen believes t h a t the future for 0.2 mm in some areas. MIM lies in its use in fields where conven3'he metal powder used in the MIM tional PM a n d lost wax processes c a n n o t feedstock has an average powder d i a m e t e r easily be a p p l i e d , r a t h e r t h a n in t h e of 6-8 jam, which makes the d e b i n d i n g r e p l a c e m e n t of these processes. operation difficult and p r e v e n t s the m a n u -
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MPR October 1993 39