Study On Injection Molding Defect Analysis And Process Optimization Of Belt Cover

Plastic products are widely used in daily life and in all walks of life. During to the orientation of molecular arrangement and the molding shrinkage, there will be uneven shrinkage of plastic products after stripping, which results in warp defect in large-sized and thin-walled plastic parts and the defect can not be thoroughly eliminated. In addiction the defect is difficult to improve during molding process and is one of the main reasons for discarding products. Therefore, optimizing the technical parameters to reduce the wapege amount has important practical significance to plastic products.This paper researches the warpage controlling of a sewing machine belt by optimizing the technical parameters of it. As the product has a large thin-walled plane, it does not meet the accuracy requirements and is difficult to install. Therefore, the injection molding simulation experiment were executed by Moldflow software and after the orthogonal numerical simulation experiment on the warpage of the plastic parts, the optimal process parameters were got. Finally, the actual production of injection molding was done and the qualified products were got. The research provides a reliable theoretical basis for the actual production of the enterprise.Firstly, gate location analysis was done under the default parameters, and gating system and cooling system were created. Then, after cooling + packing + filling + warping analysis, filling time, flow front temperature, ejection volume shrinkage, warping analysis results were got. Orthogonal numerical simulation experiment was done by setting melt temperature, mold temperature, injection time, packing time and cooling time as variables, the total amount of warpage as the measurement and the experiment shows that melt temperature effects warpage most. Through the analysis of simulation results, a group of the optimal molding process parameters were obtained: the melt temperature is 200℃, the mold temperature is 30℃, the injection time is 2.4s, the holding time is 16 s and the cooling time is 20 s.Then, combining optimal molding process parameters and the recommended screw speed in Moldflow, three groups of tryout parameters were obtained. The simulation test on the computer shows that the warpage is 2.842 mm. The warpage defect comparing with the consequence of first simulated analysis reduces 48.8%.Finally, according to the simulation results and the production practice, the design and manufacture of the belt cover mould were carried out and the defect position and the amount of defects are in agreement with the simulated mode test. With the actual production of injection mold, products were got which were filling full, no trapped air and weld line defect. And, the amount of warp is 1.27 mm. Compared with the original production of plastic parts, it has been significantly improved and meets the actual installation requirements of parts.