MIM (Metal Injection Molding) is a metal working process to creat complex metal part, containing four steps: compounding, injection, debinding and sintering.
Atomized metal powders are being compounded with a binder material to create a feedstock. The feedstock is processed by using injection molding. The molding process allows to produce complex parts in high volumes within tight tolerances as well as thin walls and excellent surfaces.
Feedstock
The Feedstock consists of fine metal powders with less than 25 Micrometer particle size which are mixed with thermoplastic and wax binders in special mixing equipment. The compounding is finished when the metal particles in the binder are fully homogenized. During the mixing process the mass is being heated. After the completion of the process the material is granulated into pellets while cooling down.
Injection
In this process step the feedstock is injected into a mold under high pressure using conventional injection molding machines. In this way MIM combines the advantages of design freedom that comes with plastic injection molding with the excellent mechanical and thermal characteristics of metallic materials. Depending on the complexity of the parts and the desired quantities, the moulds have up to 32 cavities.
The result of the injection is the so called “green part” which is at an average 20% larger than the final part.
Debinding
Depending on the binder system debinding can be done catalytically, thermally or by solvent. The binder is hereby removed from the component except of a rest binder content of 2 to 3 percent. This backbone guarantees stability of the “brown part” for the subsequent process.
Sintering
In the last step the components are sintered at temperatures between 1200°C and 1400°C depending on the material. During this step the remaining binder is completely removed. During sintering the parts shrink isotropically to their desired dimensions. Sintered parts have densities of >97% and have thus similar characteristics to parts created using cutting technologies.
Post Processing
In some cases finishing operations are necessary. MIM parts can be heat treated as any other metal parts and they can also be further processed with any type of machining operations to achieve tolerances that are more precise. AMTMIM offers a broad range of post-processing technologies like cutting, hardening, laser technologies, surface technologies including assemblies.
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