Dr. Dmitri Kopeliovich
Metal injection molding (MIM) is a method of compaction of a metal powder fed and injected into a mold cavity by means of a screw rotating in cylinder.
The method is similar to the injection molding of polymers.
The principal scheme of the injection molding method is shown in the picture:
The processing technology comprises the following stages:
1. Mixing the metal powder with 30% - 40% of a binder – low melt polymer.
2. Injection of the warm powder with molten binder into the mold by means of the screw.
3. Removal of the part from the mold after cooling down of the mixture.
4. Debinding – removal of the binder.
There are two debinding methods:
5. Sintering the "green" compact at a temperature close (but below) to the melting point .
Metal injection molding method (MIM) is widely used for manufacturing small parts having complex shapes.
The molding cycle in the injection molding method is about 10 sec, which much less, than the molding time in the alternative methods – 10-20 min.
The method permits to produce part with close tolerance, due to the consistent shrinkage. This shrinkage is taken into account in the mold design.