THE WARPAGE SIMULATION WITH IN-MOLD CONSTRAINT EFFECT IN INJECTION MOLDING

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THE WARPAGE SIMULATION WITH IN-MOLD CONSTRAINT EFFECT IN INJECTION MOLDING
注塑成型模內干涉翹曲模擬分析

Yi-Hui Peng*, David C.Hsu and Venny Yang
CoreTech System Co.,Ltd., HsinChu, Taiwan 300, ROC
Rong-Yeu Chang
National Tsing-Hua University, HsinChu, Taiwan 30043, ROC

Abstract

This paper develops a new numerical approach to simulating the mold constraint phenomenon of warpage at the in-mold stage in injection-molded part of complex
geometry and improves the accuracy of warpage analysis. Warpage in injection molding is the result of unequal volumetric shrinkage of material throughout the geometry of the piece as it cools from a melt to a solid state. Before the part is ejected, the deformation of warpage has been developed inside the mold. The influence of in-mold constraint for warpage is different according to the time of in-mold period. This in-mold constraint effect of warpage analysis technique is proved to improve the accuracy of warpage analysis for 3D/2.5D model. Several industrial cases with complex geometry are also studied to illustrate the capability of the proposed methodology.

Introduction

Warpage in injection molding is the result of unequal volumetric shrinkage of material throughout the geometry of the piece as it cools from a melt to a solid state. Before the part is ejected, the deformation of warpage has been developed inside the mold. The
influence of in-mold constraint for warpage is different according to the time of in-mold period. In general the warpage will be smaller when the in-mold period is
longer. The conventional warpage analysis doesn’t consider the in-mold constraint effect. The part is free deformation after the melt fill the part. When the cooling period become longer, the conventional warpage analysis will lose more real phenomena. The warpage with in-mold constraint effect is complicated phenomena. The contact behavior will be induced between rigid mold and plastic part. The part can’t shrink and warp freely at in-mold stage due to the rigid mold. Besides, this contact behavior also induces the stress of part. This paper develops a numerical approach to simulating the in-mold constraint effect for warpage analysis in injection-molded part of complex geometry.

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