Abstract: Experimental study on the influence of the cross section of cavity on water penetration during overflow water-assisted injection molding (OWAIM) process was conducted based on a lab-developed water-assisted injection molding system. The lab-developed water-assisted injection molding system consisted of a water injection unit, an injection machine, a mold with changeable inserts and control unit. Seven cross sections were used as characteristic sections. Circle ratio was introduced to characterize the shape of cross section. Area of cross-section (A_CS), the maximum distance between inscribed circle center and wall (Max_D), radius of inscribed circle (R_IC) of cross-section, and circle ratio were calculated as import geometry information of cross-sections. Hollow ratio was used to describe the relative void volume of water penetration. The influences of the shape and area size of cavity cross section on the shape of water penetration section and hollow ratio and residual wall thickness (RWT) were studied. In the OWAIM process, the shape of water penetration tended to approach the shape of mold cavity cross section. If the mold cavities had the same or similar cross section area, the mold cavity with a larger circle ratio would have a larger hollow ratio. If the mold cavities had the same or similar circle ratio, the area size of cavity cross section had little effect on hollow ratio. The size of water penetration section was relatively constant in a cavity with constant cross section. The residual wall thickness of a cavity with circular section was uniform. The larger the cross section, the thicker the RWT. For the cross sections with the same radius of inscribed circle (R_IC), the maximum RWT increased proportionally as Max_D increased, while the minimum RWT decreased proportionally as Max_D increased. And the RWT inhomogeneity increased significantly as Max_D increased. For these cross sections with close Max_D, the higher the R_IC, the thicker the maximum RWT and the minimum RWT.

Key words: polymer processing, molding, product design, water-assisted injection molding, cross-section of cavity, water penetration

摘要： 为考察型腔截面对溢流法水辅助注塑中水穿透的影响，基于装备有自行研发的水辅助注射系统的注塑机对几种具有代表性的型腔截面进行溢流法水辅助注塑实验，探究了型腔截面形状、大小对水穿透截面形状、中空率及残留壁厚等方面的影响规律，并分析了影响机理。实验发现：在溢流法水辅助注塑中，水的穿透截面形状会趋向型腔截面形状；在型腔截面积相近时，水穿透的中空率随截面圆率增大而增大；在型腔截面圆率一定时，水穿透的中空率受截面大小影响不大；型腔截面恒定，水的穿透截面也较恒定，残留壁厚均匀；圆截面型腔的残留壁厚最均匀，且残留壁厚随截面的增大而变厚；型腔截面的最大残留壁厚和最小残留壁厚与壁面到截面内切圆中心的距离有关。这些发现为水辅助注塑制品的截面设计提供了参考。

关键词: 聚合物加工, 模塑, 产品设计, 水辅助注塑, 型腔截面, 水穿透