Metal injection moulding offers a unique combination of metal strength and durability with the design flexibility of injection moulding. At OptiMIM, two different types of metal injection moulding are available – standard and Multi-Slide. Both offer similar advantages, such as producing complex geometries, combining multiple parts, enhancing features, dramatically reducing cycle times, and achieving greater precision and consistency. Further details about each type will be shared in a future blog post. For now, let's discuss the steps in the MIM process.
Metal injection moulding process
The metal injection moulding process involves four steps: compounding, moulding, debinding, and sintering. These four steps, together with feedstock, will be the focus of the next five parts of this blog series. Here is a brief overview of each process.
Feedstock/compounding
MIM uses metal powders combined with a plastic and wax binder, known as feedstock, as the basis for producing parts. By mixing feedstock in-house, a wide range of metals can be offered, including NiFe, 316SS, 420SS, 17-4SS, titanium, and copper. Pre-alloyed metal powders are also available. Once mixed, the feedstock is processed through a twin-screw extruder and pelletised.
Moulding
The pellets are loaded into either a standard MIM machine or a proprietary Multi-Slide MIM machine. At this stage, the component is called a "green part". The final part will have the same geometry as the green part but will be about 20% smaller.
Debinding
In this step, some of the binder is removed from the feedstock. Heat, chemicals, or a combination of both are used to remove the binders and prepare the part for sintering. Once the binder is removed, the part is referred to as a "brown part".
Sintering
The brown part is placed in a continuous or batch vacuum furnace and subjected to temperatures near the material's melting point. This removes the remaining binder and densifies the part, resulting in the 20% shrinkage mentioned earlier. Sintering takes approximately 15-20 hours.
Part two of this series will focus exclusively on the feedstock aspect of the MIM process. To answer any questions or for further discussion, contact our engineering team today!
Other articles in the series:
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