The Injection Molding Process Research On The Thick-walled Plastic Parts

With the rapid development of manufacturing industry, thick wall plastic partsare used more and more widely. It was gradually involved in military, homeappliances, home furnishing building materials industries. However, it is difficult tocontrol the volume shrinkage. So it has significant value for the research of injectionmolding process optimization.A thick wall cylinder plastic part was taken to do the experiment to determine thedegree of influence on volume shrinkage by changing process parameters such asmold temperature, melt temperature and pressure holding time. The results showedthat the main factor was holding pressure time. The materials such as PC, ABS weresuitable for molding thick wall plastic parts. They were found through simulationanalysis.The results of the simulation experiment were applied to the design andproduction of the TV bearing whose wall thickness was about80mm. The Moldflowsoftware was used to simulate the injection molding process of the thick-walledbearing and optimize the molding process. According to the analysis results, theinfluence of the wall thickness to volume shrinkage was much huger than theinfluence of the molding process parameters. It couldn’t meet the requirements just byoptimizing the process parameters. It needed to change the molding method. At thesame time, the mechanism of the shrinkage cavity was analyzed according to thesimulation results. The model with residual stress after injection molding wasimported to the Mechanical software to verify the structure strength in actual workingconditions. It implemented the joint simulation of injection molding analysis andstructure analysis.Because the conventional injection molding couldn’t eliminate the defects, themulti-component injection molding process was used to form the thick wall bearingby two times. The maximum wall thickness reduced to25mm. The orthogonalexperiment was done to determine the degree of influence of process parameters. The results showed that the main factor was holding pressure time. The volume shrinkageof the thick-walled bearing got small and uniform by the multi-component injectionmolding. It effectively eliminated the phenomenon of shrinkage cavity. Theexperimental verification and simulation were approximately consistent, so itprovided reference for similar products.