Study On The Key Techniques Of Gas Channel Design In Gas-Assisted Injection Molding

A new molding technique, gas-assisted injection molding (GAIM) which is capable of producing parts having both thick and thin sections, with structured rigidity and not sacrificing surface quality, has received extensive attention in recent years. In this process, molten plastics are injected into a mold followed by an injection of pressurized nitrogen gas into the core of the melt to produce hollow parts. Despite some pitfalls in the practical application of GAIM process, it offers a number of advantages over conventional injection molding (CIM).â‘ GAIM can substantially reduce cycle time. The melt injection time and cool time are decreased, the pressure packing time is eliminated. It is propitious to reduce parts cost.â‘¡GAIM can reduce the clamp tonnage greatly. During the CIM, clamp tonnage must large enough to meet the needs of packing stage, especially to solve the problem of sink marks. However, the low gas pressure is needed for packing in GAIM, thus, the clamp tonnage is reduced.â‘¢GAIM can save material. The first stage of this process is shot short, so the material is saved.â‘£GAIM can eliminate the pitfalls of parts greatly. Part quality can be improved by reducing residual the stress, warpage, sink marks and shrinkage that are normally encountered in CIM.Focused on the key techniques of gas channel disign in GAIM, the main study results are summarized as follows:1. Study on the key techniques of gas channel design in Gas-Assisted Injection MoldingIn this paper,we have researched and analyzed the forming mechanism of gas bubble in the gas-assisted molding,and we also researched and analyzed the factors affecting the formation of gas bubble. We have analyzed the gas channel layout and the gas channel's section shape and the size dimension in the gas-assisted injection molding.The key question of gas channel design is how to unify the material and processing condition with the gas channel layout ,gas channel size dimension gas channel section shape and so on.2.Study the influence between different gas channel section shape and the formation of gas bubble in the GAIMIn this paper,we use the Moldflow to carry on the simulation of nine kind of different section form gas channel,and obtained:the gas channel setion shape plays the very vital role in the formation of gas bubble in GAIM.When the gas channel section closer circular, after gas penetration, forms being higher, the gas channel would be fine. The circular gas channel is the most ideal gas channel form.3. Study the mathematical quantification standard of gas channel design in GAIMIn this paper, we have simulated and analyzed two kind of basic gas channel type the semicircle and rectangular to obtain the mathematical quantification standard in gas channel design.Regarding semicircle gas channel, along with gas channel radius increase, after gas penetration, forms the air bubble quality gradually enhances. When gas channel radius being smaller than wall thickness 1.5 times, it is very difficult to form the good air bubble actually, the gas will easy penetrate in the thin area and form gas fingering. When the gas channel radius to product wall thickness's ratio is bigger than 2 may form the good air bubble, the gas channel radius to the wall thickness best ratio is 2.0 Regarding the rectangular gas channel, the gas channel quality along with the gas channel width to the product wall thickness's ratio, increases highly with the gas channel to the gas channel width's ratio increases. After gas penetration, If want form the good air bubble after gas penetration,the two ratios should be bigger than 2. The gas channel width to the product thickness's best ratio is 2.0, the gas channel to the gas channel width's best ratio is 2.0.4.The gas channel of handle design and optimize in GAIMDesigned the products of FM new truck roof handle in GAIM The pre-injection volume,melt/gas delay time,pressure of gas and temperature of injected melt affecting on the penetrating of gas in the gas channel and the flowing of melt was analyzed,and got the best process paremeters.Verified the results through physical simulation,the experimental results is good,the result is beneficial to actual production.