Abstract: The principal factors affecting the warpage of long-armed product during plastic injection process were discussed. With a practical case ,an approach to decrease the warapge degree of the product by means of using multi-gates is introduced. Taken one vehicle used long armed PBT lamp holder as an sample, the rule of warpage caused by uneven cooling and shrinkage with two or three gates injection was studied respectively with numerical simulation method. The result shows that three gates injection molding is more reasonable to decrease warpage for this type of product. It is an significant way to use simulation method during design stage to improve mold design quality and optimize injection process.

Key words: plastic injection molding, mold design, warpage