Cracking Analysis And Process Research Of Cup Transparent Injection Products With Eccentric Convex

Plastic material has excellent characteristics such as greater specific strength than metal and nice insulativity.These characteristics make plastic materials be used in increasingly wide domains. Injection molding is commonly used in manufacture plastic products of complex shapes. As one of the transparent plastic materials, Styrene-acrylonitrile copolymer has more defects than non-transparent materials during the forming process, in which the defects of injection cracking will directly end the product’s life.It is a serious defect in the production. Therefore, analysing the injection products seriously cracking phenomenon and researching on reasonable improvements have practical significance for the production. The research topic of this paper comes from the enterprises and institutions entrusted to technical development projecf"Hot runner injection mold development based on CAE"(Project Number: x2jqD8113120).In this paper, a kind of styrene acrylonitrile plastic injection molding food cup Lid is studied to observe the crack fractography,analyze the causes for Cracking,analyze plastic mold structure according to causes, suggest modifications and do some feasibility analysis, finally,the injection molding process is studied and the process parameters are optimized. The content and conclusions of this paper are as follows:(1) A brief description of the characteristics of the AS plastic is given, the fracture of the crack source portion and the crack development state were observed under an ultra-depth microscope,combining with the analysis of the plastic molding process,showing tensile stresses in crack before breaking. The break may be caused by the large injection stress and demolding stress. The coexist of the tensile and compressive stress in crack development may be caused by the deflection force of the plastic eccentric structure.(2) The molding parts which have great influences on molding inner stress are analyzed using Moldflow software. The impact of molding structure on the quality of the products are demonstrated, which shows that the molding parts, hot runner system, cooling system, as well as demolding system are conducive to plastic molding. Then the influence of the gate location and the round are analyzed which gives a conclusion that the optimal condition is the original gate location with3mm fillet radius. (3) Software such as UG CAD Doctor3.0and Moldflow are used synthetically for injection molding simulation.The the injection molding process are orthogonally tested while its four factors selected are the melt temperature, the mold temperature, the gate pressure and the cooling time.A rule of the influences on the residual stress of the product by the four factors is learned as follows:melt temperature> holding pressure> mold temperature> cooling time. Based on this rule, separate analysis are made form every aspect of the four factors and the overall optimized parameters are obtained.(4) The plastic parts residual stress under tests by using acetic acid solvent. Comparison of the conclusion of the crack test with the simulation shows the similarity of the two tests and illustrates the accuracy of the simulation. There is no failure cracks in the test results and the optimize process parameters can definitely improve the product quality.20sets of the actual production data are recorded that the cracking situation is associated with the use of the release agent.