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

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