Material supplier DuPont is trying to help injection molders with a processing problem, long hold times when molding semi-crystalline material. In the case of large shot volumes or relatively short overall cycle times, the company has garnered time savings of up to 30% by allowing two sequential injection molding phases, application of hold pressure and dosing, to be done simultaneously, with these methods for applying hold pressure and the feeding of molten material integrated into the mold.
DuPont Performance Polymers says its new In-Mold Hold Pressure (IMHP) technology utilizes a hydraulically operated piston, which is integrated in the movable side of the mold. This is immersed in a specially provisioned and appropriately dosed melt cushion, with the equivalent melt volume available on the stationary side of the mold in the hot runner. The molten material is then pressed into the cavity using a needle-valve-like mechanism. These methods are currently being tested and refined by DuPont at its Technical Center in Meyrin, Switzerland, utilizing different semi-crystalline thermoplastic grades, with a current emphasis on minimizing the additional space required....