Among the appearance defects of injection molded products, sink mark near the gate accounts for a large proportion, especially for the precision products that require a high appearance quality. The traditional method to relieve gate sink mark is to increase packing pressure and packing time. Even so, the problem cannot be completely solved. In current study, a three-dimensional numerical simulation method was employed to analyze the formation mechanism of gate sink mark. The analyses point out that high shear in the filling stage, melt refilling in packing stage and high mold temperature lead to the imbalance of shear heat generation and cooling between the gate and other regions, and finally result in the relatively high temperature and the sink mark defect in the gate region. Based on these results, a novel and simple method for improving gate sink mark by adding beryllium copper insert in the runner was proposed and implemented. Further simulation shows that the method is effective in eliminating the gate “hot spot” and improving the temperature uniformity of the entire product. The experiment results also prove that the heat sink mark in the gate area can be effectively avoided by using the mold with insert for both amorphous ABS and semi-crystalline PP products. The proposed method can not only solve the sink mark problem effectively, but also has the advantage of being simple and easy to achieve because the slide type side gate design is adopted.

在注塑产品的外观缺陷中，浇口附近的凹痕占很大比例，尤其是对外观质量要求较高的精密产品。消除浇口缩痕的传统方法是增加保压压力和保压时间。即便如此，问题也不能完全解决。在目前的研究中，采用三维数值模拟的方法来分析浇口缩痕的形成机制。分析指出，充型阶段的高剪切、保压阶段的熔体再填充和较高的模具温度导致浇口与其他区域的剪切生热和冷却不平衡，最终导致较高的温度和缩痕。栅区缺陷。基于这些结果，提出并实施了一种通过在流道中添加​​铍铜嵌件来改善浇口缩痕的新颖而简单的方法。进一步仿真表明，该方法可有效消除浇口“热点”，提高整个产品的温度均匀性。实验结果还证明，对于非晶ABS和半晶PP制品，使用带嵌件的模具都可以有效避免浇口区域的散热痕迹。所提出的方法不仅可以有效解决缩痕问题，而且由于采用了滑动式侧浇口设计，具有简单易行的优点。进一步仿真表明，该方法可有效消除浇口“热点”，提高整个产品的温度均匀性。实验结果还证明，对于非晶ABS和半晶PP制品，使用带嵌件的模具都可以有效避免浇口区域的散热痕迹。所提出的方法不仅可以有效解决缩痕问题，而且由于采用了滑动式侧浇口设计，具有简单易行的优点。进一步仿真表明，该方法可有效消除浇口“热点”，提高整个产品的温度均匀性。实验结果还证明，对于非晶ABS和半晶PP制品，使用带嵌件的模具都可以有效避免浇口区域的散热痕迹。所提出的方法不仅可以有效解决缩痕问题，而且由于采用了滑动式侧浇口设计，具有简单易行的优点。