The rear wall on John Deere's Harvester is one of the largest reactioninjection-molded (RIM) parts ever in-mold coated by GI Plastek, Newburyport, Mass. The part weighs in at 56 lb and is roughly 6-ft square. Its 30-sq-ft surface area carries a Class A finish straight from the mold thanks to GI Plastek's proprietary in-mold coating system called ProTek.
Initially, John Deere was codeveloping a rear wall made from a sheet-molding compound (SMC) to cover the combine engine platform. During development, however, the specifications for platform size continued togrow. To keep pace, the original rear-wall part had to grow deeper and deeper untilSMC tooling costs became prohibitive. A RIM in-mold composite system ultimately turned out to be a better option.
Molded using a foamed material system, the rear wall is 28 lb lighter than its SMC counterpart and needs no secondary structural support. The nickel shell tooling used to mold the RIM part cost $150,000 less than SMC tooling and was built in only five months. The ProTek in-mold coating process is said to have cost 50% less than competitive postpainting methods.
Information for this article was provided by GI Plastek, Newburyport, Mass., (978) 462-9006, www.giplastek.com