MIM vs Investment Casting.
- Thread starter SIGSHR
- Start date
ActivShootr
New member
MIM is usually used for small parts that are hard to machine. Investment casting is usually used for large parts that will need to be machined anyway. I'm not sure one outweighs the other.
They seldom compete directly. A part that lends itself well to investment casting will seldom be commercially viable in MIM and vice-versa. Generally.
This is as good as any as an intro to investment casting:
http://en.wikipedia.org/wiki/Investment_casting
MIM is being beat to death in a separate thread.
Investment cast may be done with parts large and small. How large? Well, how about a Sherman tank hull? How small? Ruger casts bolts (cylinder stops).
I prefer investment casting to MIM. MIM is used for small parts and while MIM can be made to very precise tolerances, it is only case hardened and once you wear away that surface, it wears very quickly.
I prefer investment casting to MIM. MIM is used for small parts and while MIM can be made to very precise tolerances, it is only case hardened and once you wear away that surface, it wears very quickly.
Bill DeShivs
New member
MIM or IC parts can be heat treated just like any other part-depending on the metal they are made from. All MIM/IC parts aren't case-hardened.
It bears pointing out that investment cast products can and often do contain voids within the material. It takes a significant amount of work to minimize casting voids.
A casting void is essentially an air pocket or bubble in the liquid metal. If the pour into the mould is done improperly, small air pockets can form as the metal cools. These, of course, can make the product weaker than forged steel.
Steel forging uses hammers and pressure to drive out the air pockets and form the metal into a cohesive piece. This is not done on investment cast parts. This is one reason some parts of a Ruger (e.g. topstrap) are thicker than on Colt, S&W and other forged metal frames.
MIM uses a powdered metal blended with a polymer. This is injected into an oversized mould (oversized for the finished part). This "green" part is then heated to drive off the polymer and fuse the metal together in a process called sintering. During the heating process, the part shrinks predictably and tolerances of the finished part often require no secondary machining steps. MIM is especially good for smaller parts with complex shapes that would normally require several machining steps.
MIM reportedly is around 98% as dense as wrought iron so it is better than investment casting for strength in small parts. Tensile strength of properly treated MIM parts is close to that of mill forged steel.
A casting void is essentially an air pocket or bubble in the liquid metal. If the pour into the mould is done improperly, small air pockets can form as the metal cools. These, of course, can make the product weaker than forged steel.
Steel forging uses hammers and pressure to drive out the air pockets and form the metal into a cohesive piece. This is not done on investment cast parts. This is one reason some parts of a Ruger (e.g. topstrap) are thicker than on Colt, S&W and other forged metal frames.
MIM uses a powdered metal blended with a polymer. This is injected into an oversized mould (oversized for the finished part). This "green" part is then heated to drive off the polymer and fuse the metal together in a process called sintering. During the heating process, the part shrinks predictably and tolerances of the finished part often require no secondary machining steps. MIM is especially good for smaller parts with complex shapes that would normally require several machining steps.
MIM reportedly is around 98% as dense as wrought iron so it is better than investment casting for strength in small parts. Tensile strength of properly treated MIM parts is close to that of mill forged steel.