Research On Optimization Process Parameters For Large Pieces Of Thin-wall Injection Molding

Injection molding is one of the most important methods of Manufacturing in today. However, injection molding especially large-sized thin-walled injection molding have their own shortcomings, it can easily cause some quality problems in the process of production. The major problems of the large-sized thin-walled parts is warping, how to reduce the warping of the thin-walled parts being a major problem that troubled the engineering. If we only rely on traditional technology experience and try again and again to approach it, it is not only a waste of money, and time, but also difficult to solve the problem effectively. It can forecast and analysis the factors that cause the warping and the size of the warping by applying the Moldflow analysis software. According to analysis results adjusting the structure and process parameters of the large-sized thin-walled parts, so we can get the best large-sized thin-walled injection molded parts.The paper introduce the foundation of injection molding technology. Including state-of-the-art of injection molding, main processing parameter, molding material, condition of molding and the common problem in the molding process. It introduce the research situation on the warping problems, there is two methods, one is experimental studies and the other is theoretical analysis method. The principal factors that effect the warping of Thin-walled parts are plastic materials, products shape, structure and die process conditions. According to the reasons that cause the warping of the thin-walled parts, we can reduce the warping of thin-walled parts by modifing the the geometry of the part, changing the structure of injection mold, changing the injection molding process parameters. The dissertation also describe the mould plastic and filling the course melting body rheology analysis of the mould. Point out plastic fusibility belongs to the fluid which is glotinous, no-newton and no-compressible. The fusibility has the flow course of free surface and non-isothermal instant state when it conduct the movement of filling-moulding. Depict simply the physical course of fusibility filling moulding. At the same time a thin-walled parts warping CAE mathematical model is also established.When choose the equipment that produce the automobile back cap inner trimming parts, it requires the injection device has sufficient injection pressure and the alamping device has sufficient clamping pressure. It also requires that the injection mold can endure high injection pressure and has quick injection velocity.In this dissertation a model that is a large pieces of thin-walled injection—the interior of car rear cover door is established by Pro/E software. Loading-in the established model to the Moldflow simulation software. Meshing the model and desion the gating system, cooling system. As the gating system has a large impact on the molding process and the warping for large pieces of thin-wall injection moldels, When the system has a different number of gate, this paper contrast the warping size of the interior of car rear cover door, and I choose three gates. Then through orthogonal test, I analythe the impact of various process parameters. According to table orthogonal test and analysis, it is shown that the molten material temperature have a more significantly impact on the warpage of the interior of car rear cover door, packing time and injection pressure have a significantly impact on the warpage of the interior of car rear cover door. Compared with the molten material temperature, injection speed and mold temperature have a little impact on the warpage of the interior of car rear cover door. Molten material temperature is the most important factor, the trend that the molten material temperature impacting the warping is that, with the increasing of molten material temperature, the warping first become small, and then gradually become larger.Finally, By setting a combination of different process paramete and repeatedly simulation analysis by Moldflow software, a group of process parameters under which the interior of the car rear cover door has the smallest warpag is got.The optimal process parameters is that: molten material temperature for 230°C , mold temperature for 35°C , injection rate for 58 cm 3/s , injection pressure for 170Mpa, 35s dwell time. In condition of combination of the optimal parameters, the minimum warping amount of automobile back cap inner trimming parts is 9.024mm.