RIM (Reaction Injection Molding) is great for low-volume production of big shell part with simple design. It is a new manufacturing process for product of rapid tooling whereby the fast polymerization and solidification of two pre-polymers quickly mixed and injected into the mold cavity to form the parts. Normally, the mold materials are ABS, Epoxy and Aluminum, and injection molding material PU (Polyurethane) with ABS-like property. Since the cheap cost and short time of tooling making, also the easy operation, it greatly reduces not only the production cost and also time for low-volume production parts.