Study On The Filling Ability And Residual Stress For Thin-Wall Plastic Injection

With the development of plastic products to being light, thin, short and small, the forming difficulty, the forming quality and the influence factors have become important issues in injection molding industry. Because plastics turn to thinner and the plastic melt cool fast in the cavity, it results in the more difficulty of moulding. Simultaneously, as'the plastics cool fast during the moulding process, it leads to residual stress in the plastics and the shrinkage and warpage.The paper synthesized the domestic and international development of TWIM (Thin-Wall Injection Molding) technology. Study on the filling ability and residual stress for thin-wall injection is put forward. Because in domestic the research of TWIM is just on the beginning, and the theory system is still not, it is beneficial that the paper can reinforce research in TWIM.An injection mold which has one cavity and use submarine gate for sliding phone shell is designed and manufactured for experiments. The thickness of wall is 0.5mm, and plastic is ABS. The study of filling ability, in numerical simulation based on the Moldflow software, is used by the Taguchi method to study the influence of the process parameters (melt temperature, mold temperature, injection pressure, injection rate, holding pressure, holding time) and their interactions, then by using the single factor method, range analysis and ANOVA analysis to process the experiment data. The study of residual stress, in numerical simulation based on the Moldflow software, is used by the photo-elastic experiment to measure residual stress distribution with different process parameters.The results show:(1) Filling ability. The results of Range analysis and ANOVA analysis are basically the same. For the filling ability, melt temperature is the most important process parameter, whose contribution rate is 42.72%. The second is injection pressure, whose rate is 35.89%. The last is mold temperature, whose rate is 14.92%. Injection rate, holding pressure and holding time have little impact on the contribution of filling rate.(2) Residual stress. By using photo-elastic experiment to measure residual stress distribution to compare the regional distribution in the different parameters, it is shown that the process parameters of influencing residual stress are ranged as melt temperature, injection rate, mold temperature, cooling time, packing pressure and packing time. Increasing the melt temperature is the appropriate way to improve products interior residual stress.