A novel air-driven injection machine for small parts (10 g or less) relies on barrel heating rather than mechanical shear heating for resin melting.

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A novel air-driven injection machine for small parts (10 g or less) relies on barrel heating rather than mechanical shear heating for resin melting. It comes from Koalesce of Berthoud, Colo. President Rick Fitzpatrick sought to separate melting from the conveying and injection functions of the screw to gain greater control of each segment of the process. A screw auger advances pellets to a heated zone of the barrel, and then melt is transferred to the injection zone in front of the inline plunger. (Some applications may require heated plungers, and larger presses in the future will have heated screws.) A Koalesce machine with a 40-g shot size reportedly uses only 10% to 15% of the power of conventional presses. Powered by 90-psi compressed air, the 5- to 10-ton toggle press reportedly uses less than 3 kwh/hr to mold a 40-g shot and generates pressures of 20,000 to 40,000 kpsi. (Power consumption for compressed-air usage adds at most 10% to the total, Fitzpatrick says.) The press has run PE, PP, PC, PET, PBT, and nylons. Shearing of the resin is greatly reduced, Fitzpatrick says, and high temperatures and pressures are applied only in limited areas of the machine, which permits a compact design and fast (15-min) start-ups. Low purchase and operating cost are said to make it cost-competitive to run this press with one to four cavities versus eight to 32 on a standard press. The press is available in horizontal, vertical, and two-shot configurations and can be delivered in around five weeks for a price of $20,000 to $40,000. Three machines have been sold in the past year. Fitzpatrick was v.p. of engineering at custom molder DTM Products in Niwot, Colo., and held other mold-design and managerial positions before he started Koalesce in 2004. (970) 214-6440 • www.koalesce.com