Metal injection molding (MIM) is a manufacturing process which combines the versatility of plastic injection molding with the strength and integrity of machined, pressed or otherwise manufactured small, complex, metal parts.

The process involves combining fine metal powders with plastic and wax binders which allow the metal to be injected into a mold. The binders are then removed by solvent and thermal processes and the resultant metal part is then sintered at temperatures great enough to bind the particles but not melt the metal. The products of metal injection molding are up to 98% as dense as wrought iron and used in a broad range of applications (including medical, dental, aerospace, and automotive just to name a few.)

The window of economic advantage in metal injection molded parts is such that the complexity and small size of the part or perhaps difficulty of fabrication through other means make it cost inefficient or impossible to manufacture otherwise. Increasing complexity for traditional manufacturing methods typically does not increase cost in a metal injection molding operation due to the wide range of features possible through injection molding (undercuts, thread both internal and external, miniaturization, branding, etc.) Source from wikipedia