MIM or Classic Casting – Which Is the Right Process for My Application?

The stirrup is a steel part of a saddle and ... also the smallest bone in our body, located in the middle ear. It is only a few millimeters in size and weighs about three grams. Producing it for medical purposes, for example, as a stainless steel implant, is very costly. This type of production is simplified with the Metal Injection Molding (MIM) process. MIM applications are implemented in a wide range of industries, covering medical devices, the automotive and construction industries, and even the leisure sector.

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A Precise Process: MIM

The roots of MIM are in plastics injection molding technology. With this process, challenging or very small components with complex geometry can also be indirectly manufactured from metal. The MIM process combines the advantages of injection molding with geometric design freedom, even for metals / alloys that are difficult or impossible to machine or cast. In MIM, metal powder mixed with a thermoplastic binder is used instead of the plastic granules and can thus be used for all alloys. After demolding, the binder is removed from the component in a downstream sintering process, leaving the sintered finished part, which typically has a shrinkage of 15 %.

MIM or Classic Casting

In this context, the term “classic casting” means investment casting, which is the alternative to MIM. Before starting production in investment casting, it is necessary to prepare a wax pattern and a ceramic mold in an upstream process. MIM, on the other hand, involves direct injection into a permanent mold. However, due to the high tooling costs, MIM only makes sense for batch sizes of 10,000 to 15,000 parts per year. Classic casting can therefore be the better solution for smaller batch sizes, with the exception of alloys that cannot be casted properly. The important thing is: It is not the process that determines the molded part, but the molded part that determines the process.  

Finding the Right Process by Using Simulation

When deciding between classic injection molding and MIM, a simulation with SIGMASOFT Virtual Molding can be a useful solution: It can simulate both the investment casting process and the MIM process from mold filling to the finished component, while providing crucial information for the selection and optimization of the appropriate process.