THE EFFECTS OF MOLDING CONDITIONS ON THE RESIDUAL STRESSES IN INJECTION MOLDED POLYSTYRENE FLAT PARTS

The plastic injection molding is a process which polymer melt is injected into a mould cavity, and solidifies to form a plastic part. the properties of the molded parts are related design of the products and the molds, the plastic materials and the molding conditions. the residual stresses can cause usability, dimensional stability, mechanical properties, and resistance of chemical etc. of product. in this study, the effects of molding conditions on the residual stresses in molded polystyrene (ps) flat parts were experimentally investigated. six factors were examined and taguchi experimental setup l27 orthogonal array was used. these factors were the injection pressure, the melt temperature, the mold temperature, the packing pressure, the packing time and the cooling time. the results showed that the injection pressure, the mold temperature and the packing time had greatest influence on the residual stresses in molded polystyrene parts. as a result, the residual stresses were increased by increasing the injection pressure, decreasing the mold temperature and increasing the packing time.