metal injection molding process

The metal injection molding process consists of four steps: raw material preparation, molding, degreasing and final sintering.
Each step is briefly discussed below:

Prepare raw materials

The specified metal is atomized into a very fine powder, typically less than 20 microns, added to a heated thermoplastic binder, mixed thoroughly, and then cooled. This mixture is then granulated into uniform particles made of approximately 60% metal powder and 40% polymer binder.

injection molding

The raw material is remelted and injected into the same type of cavity mold used in plastic injection molding. The raw material cools and solidifies into the specified part design. During this process, parts are considered "green."

skim

Once the part cools and solidifies, the polymer is removed through one of three options: aqueous process, solvent process, or catalytic process. This reduces a significant amount of bulk per product, which is something to consider during the design process. During this process, the parts are considered "brown".

sintering

Parts are sintered in a high-temperature furnace, incorporating 17-22% of empty space depending on the alloy system. The result is a high-density part reaching 95-99% of the theoretical density of the forged material. The part will shrink to 75-85% of its pre-sintered size. Your MIM supplier needs to consider the shrinkage of each geometry, especially during the design phase.
MIM parts have good dimensional accuracy and typically do not require secondary operations to achieve tolerances. Benefits of Metal Injection Molding Metal injection molding can economically produce extremely complex geometries with high repeatability compared to competing technologies.