中文摘要：

针对厚壁中密度聚乙烯燃气管道阀门内部缩孔问题，设计并制造了相应的模具，从模具结构、注塑工艺、制件脱模后热处理等方面提出了解决制件内部缩孔问题的方案。通过对各种工艺参数的优化研究，得出了各因素对内部缩孔问题的影响程度及最佳工艺参数。结果表明，合理的工艺条件及模具结构能够解决厚壁制件内部缩孔问题。

英文摘要：

A mold was designed and manufactured in order to solve the internal shrinkage of medium density polyethylene （ PE-MD ） thick gas pipe valves, the solutions of internal shrinkage was proposed from the structure of mold, injection process, heat treatment after demolding of plastic part and so on. The effect of each parameter on internal shrinkage and the optimal technological parameters were obtained by optimizing and researching different processing parameters.The experimental results showed that the problem of internal shrinkage of PE-MD could be solved through a reasonable process and mold structure.