Metal injection molding prototypes using the MIM process

Rapid prototyping in metals can also be achieved by injection molding. In this so-called powder injection molding (PIM) process, metal powder, surrounded by a thermoplastic binder matrix, is injected into the mold cavity. The binder is then removed chemically and thermally and then the component is sintered. This produces solid filled components with smooth surfaces and excellent functional properties.

The following metals can be processed using the MIM process, among others:

• Various stainless steel alloys (316L, 17/4 PH, HK30, 420)
• Inconel 718
• Carbides
• Titanium alloys (TiMIM)

Not processed in the MIM process:

• Aluminium
• Tin and Zinc alloys
• Brass
• Magnesium alloys

These metals and alloys can be processed more cost-effectively by die casting and are therefore not used for MIM.

Metals in additive manufacturing

For some time now, different 3D printing methods have been available for processing metals. However, these processes are only preferred where conventional, non-manufacturable geometries are of great advantage. For example with hollow lightweight components.

The biggest disadvantage of these processes is still the coarse surface structure that is achieved. For many applications this means that mechanical finishing is required in order to produce mating surfaces and minimize stress concentrations. Therefore, the gains achieved compared to either conventional machining or finished metal casting are often quickly lost.

«Additive Tooling» for fast MIM prototypes

The «Additive Tooling» processes of Injex are also excellently adapted for metal injection molding. Throughput times for first samples previously over five months are now reduced to two to three weeks. With these samples the suitability of the MIM process for the respective application can be tested offering greatly reduced risk and high scalability.