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:

• solvent debinding – the binder is dissolved by a solvent or by water;

• thermal debinding – the binder is heated above the volatilization temperature.

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.

Metal injection molding method (MIM) is involved in processing carbon steels, stainless steels, nickel alloys, tungsten and molybdenum.

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• Powder metallurgy - introduction
• Powder preparation
• Die pressing of metallic powders
• Isostatic pressing of metallic powders
• Sintering of metals
• Methods of shape forming ceramic powders
• Sintering of ceramics
• Spark plasma sintering

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