Comparison between MIM metal injection parts and conventional powder metallurgy parts

Overview of metal injection molding:

Injection molding of metal powder metallurgy parts comes from plastic injection molding. In plastic injection molding, thermoplastic resin powder or particles are heated to the temperature of viscous fluid required for molding, and then injected into the mold. After the resin solidifies in the cold mold, it is separated from the mold and made into plastic parts of the required shape.

Comparison between metal injection molding and conventional powder metallurgy parts production

In the injection molding of MIM metal powder parts, thermoplastic resin or appropriate wax is used as the adhesive to mix it with metal powder. The mixture is injected into the mold and the adhesive is cured, then the parts with high enough strength are separated from the mold. After removing the adhesive, the parts are sintered.

The injection molding of MIM metal powder parts is the same as the general plastic injection molding, which can produce small parts with complex shapes that cannot be produced by conventional pressing. In addition, injection molded parts contain a considerable amount of binder after forming. After removing the binder, the parts are porous and the density is as low as 60% of the theoretical density. Therefore, in order to achieve the density close to that of cast or forged parts, injection molded parts must be sintered under the condition of shrinkage. When the injection molded parts are sintered, the shrinkage of the size is usually about 18%, while the size of the conventional pressed powder parts is difficult to control when sintered under this condition. However, in injection molding, the metal powder particles have no plastic deformation in the forming process, so the shrinkage of the parts during sintering is very uniform, and its size change can be predicted. Because injection molding can produce parts with complex shapes, this technology has developed very rapidly.