EXTERNAL GAS MOLDING OPENS NEW DESIGN OPTIONS FOR PRODUCT DESIGNERS

摘要

External Gas Molding (EGM) has developed a further way gas assist is applied to the injection molding process. The concept is to apply gas pressure to one surface of the plastic in the mold to force the shrinkage and sink marks away from the visual surfaces. While reduced cycle time and lower weights are also benefits, it is the elimination of sink marks that makes EGM so interesting to designers. This paper explores the new rib design and boss design rules in terms of rib aspect ratio. The findings suggest that plastic piece part designers may need to change the order of the design sequence. The rib pattern replaces wall thickness as the design platform. The basics of the EGM process are also discussed along with several product examples.