Gas-assisted Injection Molding Numerical Simulation And Process Optimization

Gas assisted injection molding (GAIM) is one of the most important, innovative molding processes for thermoplastics. GAIM process, which can be used to provide a hollow shape in the molding, is different from the conventional injection molding (CIM) process. Compared with CIM, there are many advantages of GAIM, such as reduction of material, sink mark, warpage, and lower injection pressure, and so on. In the GAIM process, gas is injected into a mould cavity filled partially with polymer melt. The gas penetrates the molten polymer and drives it further into the mould until the mould is completely filled.In the thesis, based on the research of GAIM, it is investigated that the application principle of CAE technology in GAIM. The molding process of the minisize-truck's front-bumper is simulated by using CAE software, and the GAIM processes of bumper also are optimized in the end.First of all, the GAIM process is analyzed in detail in this thesis. Especially, the investigation of key technology has been made. Based on the viscous hydrodynamics, rheology and calorifics, the filling principle of GAIM has been researched. Although GAIM has many advantages compared with conventional injection molding, it introduces new processing parameters and makes the application more critical. Computer simulation has become an important and required aid in part design, mould design, and process evaluation in recent years. Numerical simulation and experimental studies concerning melt flow and gas penetration of GAIM are conducted. Considering the influence of gas penetration on melt flow only as boundary conditions of melt filling region, a hybrid finite-element/finite-difference method similar to CIM simulation is used in the GAIM filling simulation. The implementation principle of GAIM numerical analysis is investigated, which is based on the analysis of polymer melt flow and gas penetration physical model.