注射成型薄壁制品收缩与翘曲因素

Affecting factors of shrinkage and warpage of thin-wall injection molding process

介绍了薄壁注射成型的充填、保压、冷却和残余应力的数值模型, 并将集成的模拟程序对收缩翘曲问题进行定量地模拟分析. 采用Taguchi 实验优化设计理论, 用L27 (313) 正交表设计实验并进行了统计分析. 研究了因素如熔体温度、模具温度、保压时间、保压压力、浇口尺寸和注射速率对收缩与翘曲的影响的显著性. 得出优化工艺参数如熔体温度、模具温度、保压时间和压力能减少残余热应力; 保压压力和熔体温度是影响收缩与翘曲的最显著因素.

Communication and electronic products have been developing towards the design concept of being light, thin, short and small. To acquire the maximal internal space for parts to be packed closely into the product, one way is to reduce the wall thickness of the housing components. Therefore, the production technique of plastic injection molding of a part with a thin shell feature is becoming more important. Many factors lead to the defects of parts, such as warpage, shrinkage, residual stress, and so on. This research used the experimental design of the Taguchi method to determine the injection molding conditions, and the injection processes were simulated by using the integrated software packages MoldflowTW. Both molding conditions and affecting factors were discussed regarding the degree of warpage of the shell of a mobile phone. The results showed that the melt and mold temperature had the greatest influence on shrinkage in X direction, the packing time had the greatest influence on shrinkage in Y direction and the packing pressure had the greatest influence on warpage of Z direction. However, the shrinkage and warpage were only slightly influenced by the gate dimension and the injection rate in the case of mobile phone. In addition, applying the experimental design of the Taguchi method is a quite effective method to deduce the optimum set of affecting factors in injection molding to produce plastic parts with minimum shrinkage and warpage.