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IMHP technology from DuPont technology can decrease injection molding cycle time
A new In-Mold Hold Pressure (IMHP) technology from DuPont Performance Polymers (DuPont) enables significant productivity increases during the injection molding of semi-crystalline thermoplastics. In the case of large shot volumes or relatively short overall cycle times, the time savings can be up to 30 percent.
In-Mold Hold Pressure technology allows two sequential injection molding phases — applying hold pressure and dosing — to be done simultaneously.
The IMHP process from DuPont offers two different methods — each integrated within the mold — for applying hold pressure and the successive feeding of molten material.
As part of the first method, a hydraulically operated piston, which is integrated in the movable side of the mold, is immersed in a specially provisioned and appropriately dosed melt cushion.
Alternatively, the equivalent melt volume is available on the stationary side of the mold in the hot runner. In this case, the molten material is pressed into the cavity using a needle-valve-like mechanism. Both methods are currently being tested and refined by DuPont, with a current emphasis on minimizing the additional space required.
"We have conducted numerous injection molding trials with different semi-crystalline thermoplastic grades at our Technical Center in Meyrin, Switzerland, and were able to demonstrate, on the basis of producing standard bars used for tensile testing, the potential efficiency improvements," said Ernst A. Poppe, European manager for application and processing technology at DuPont Performance Polymers. "IMHP technology is particularly beneficial when molding DuPont™ Delrin® acetal resin, for which the hold pressure time constitutes a large proportion of its overall cycle time. Additionally we were able to demonstrate that there were no significant changes in terms of dimensional stability and mechanical properties between standard injection-molded samples produced with IMHP technology."