The Caeanalysis Of HDPE Thick-Walled Workpleces In The Injction Molding And Cooling Process

As the plastic parts are light and not susceptible to corrosion, it isgradually replacing the traditional steel in many application areas. However,plastic have much lower strength and modulus than metals, people had toenhance the products in many engineering applications through thethickness and plastic compound or other methods. However, there was alarge shrinkage and residual stress in injection molding thick-walled product,it's difficult to control the plastic parts molding quality.This issue made use of MOLDFLOW and ANSYS to analysis thetemperature changing history at different thick layers of 20,30and 40mmthick cubes in the cooling process of injection molding. It also analyzed theinfluence of the temperature changing on the crystallinity at different thicklayers, process parameters on the shrinkage and residual stress distributionof different thickness. This paper had made experiments on the formationand the size of parts'shrink hole and depression.The results showed that:1). As the mold temperature increasing, the crystallinity at both surface and core layer of thick-walled plastic parts increased, and the surface had asignificant degree than the core layer, that leaded to the differences insurface crystalline from core layer decreases. When the mold temperaturewas the same, the greater the parts thickness, the higher degree ofcrystallinity at the thick layer.2). Mold temperature and holding pressure time had a greater impact onbody shrinkage. As the mold temperature rising, surface body shrinkage rateincreased more rapidly than the core layer, the difference of surface bodyshrinkage from core reduced. As the holding pressure time longer, the corelayer body shrinkage rate decrease more than the surface layer, thedifferences of surface body shrinkage from the core decreased. The greaterthickness of plastics parts, the larger differences of surface body shrinkagefrom the core. The difference of surface body shrinkage form the core is themain reason for the defect to thick products.3). The surface residual stress was greater than the core layers, theresidual stress would decrease as the mold temperature increasing. Thegreater thickness of plastic parts, the greater the surface residual stress.According from the CAE simulation results, at the condition of highermold temperature, it can get the thick plastic products that structure compactand the shrinkage hole doesn't exist. This issue also carried outexperimental verification. The results show that, at the conditions of 200℃melt temperature, the shrink hole of 30mm thick part will become small as the 90℃mold temperature, and the shrink hole will disappear as the 120℃mold temperate.