Research On The Effects Of Variable Cross-section Fan Gate On Injection Molding Of Thin-walled Plastic Parts

The thin-wall injection molding technology is emerging technology which develops from the traditional injection molding technology and is used for forming all types of thin-walled plastic parts. The thin-wall injection molding technology has a lot of advantages of saving energy and protecting environment, reducing cost and shorting the experimental period. The thin-walled plastic parts are widely used in many fields including biomedical field, aerospace, automobiles,home appliances and instrumetation for its advantages such as small volume, light quality and low cast. The process time of thin-wall injection molding is very short and the process is complicated.As a result a lot of quality problems such as short shot, uneven shrinkage and warpage appear. The structure and the size of the gate were changed, which could control the behavior of melt flow, achieve balanced filling process and increase the forming quality of thin-walled plastic parts.Firstly, thin-walled injection mold with continuous variable cavity size was designed to complete follow-up injection molding experiments. During the design of the mould, the method of using movable slider to get continuous variable cavity size was put forward,which could replace the traditional method of using cavity inserts to change cavity size. The thin-walled injection mold with continuous variable cavity size can reduce the cost, shorten the experimental period and ensure the follow-up injection molding experiments.Secondly, the effects of variable cross-section fan gate on the melt flow behavior and the forming quality of thin-walled plastic parts with different aspect ratio were researched. The injection molding experiments and numerical simulation were completed by variable cross-section fan gate and traditional fan gate.And during the experiments and numerical simulation the injection molding parameters and materials were the same.After the experiments, the melt front distance difference, uneven shrinkage and warpage of variable cross-section fan gate were contrasted with those of traditional fan gate.The results showed that with the decreasing of the thin-walled plastic parts'length-width ratio, the effects of variable cross-section gate would decrease.Thirdly,the effects of bulge length and width on the melt flow behavior and the forming quality of thin-walled plastic parts with different aspect ratio were researched. The injection molding experiments and numerical simulation were completed by variable cross-section fan gate and traditional fan gate.And during the experiments and numerical simulation the injection molding parameters and materials were the same.After the experiments, the the melt front distance difference, uneven shrinkage and warpage of variable cross-section fan gate were contrasted with those of traditional fan gate.The results showed that the bulge width has little influence on the melt flow behavior and the forming quality of thin-walled plastic parts, Besides with the decreasing of bulge length, the effects of variable cross-section gate on the melt flow behavior and the forming quality of thin-walled plastic parts would decrease.Finally, according to different materials the the effects of variable cross-section fan gate on the melt flow behavior and the forming quality of thin-walled plastic parts were researched. PP, PMMA and PC were used in the injection molding experiments and numerical simulation.After the experiments, the the melt front distance difference, uneven shrinkage and warpage of variable cross-section fan gate were contrasted with those of traditional fan gate.The results showed that compared to PP, if PMMA and PC were used, the diversion effect of variable cross-section fan gate could be more effective, but the effect of reducing plastic shrinkage unevenness would decrease. Besides according to PMMA and PC the effects of variable cross-section fan gate on warpage were basically the same...