Process

The powder injection molding process

An early developer of the process during the 1970s was Dr. Raymond E. Wiech Jr., who refined MIM technology as co-founder of a California company named Parmatech, the name being condensed from the phrase "particle materials technology".Wiech later patented^[4] his process, and it was widely adopted for manufacturing use in the 1980s. Competing processes included pressed powder sintering, investment casting, and machining.

MIM gained recognition throughout the 1990s as improvements to subsequent conditioning processes resulted in an end product that performs similarly to or better than those made through competing processes. MIM technology improved cost efficiency through high volume production to "near-net-shape", negated costly, additional operations left unrealized in competing processes, and met rigid dimensional and metallurgical specifications.

The process steps involve combining metal powders with wax and plasticbinders to produce the "feedstock" mix that is injected as a liquid into a hollow mold using plastic injection molding machines. The "green part" is cooled and de-molded in the plastic molding machine. Next, a portion of the binder material is removed using solvent, thermal furnaces, catalytic process, or a combination of methods. The resulting, fragile and porous (2-4% "air") part, in a condition called "brown" stage, requires the metal to be condensed in a furnace process called Sintering. MIM parts are sintered at temperatures nearly high enough to melt the entire metal part outright (up to 1450 degrees Celsius), at which the metal particle surfaces bind together to result in a final, 96-99% solid density. The end-product MIM metal has comparable mechanical and physical properties with parts made using classic metalworking methods, and MIM materials are compatible with the same subsequent metal conditioning treatments such as plating ,passivating, annealing, carburizing, nitriding, and precipitation hardening.