Gas-assisted Injection Molding Numerical Simulation Of The Gas Filling Process

Gas-assisted injection molding(GAIM) is an innovative process invented recently. It is used to produce plastic parts with hollow sections. GAIM is becoming an important process in industry, due to its flexibility in design and manufacture of plastic parts.GAIM has much more virtues compared with the conventional injection molding, but it is more complex because of some new processing parameters. Under providing reasonably assumptions, the main contents of this theis are summarized as follows:(1) Based on the summarization of the present literatures, the thesis presents the current study and development of numerical simulation on GAIM. The mathematical models, which can describe the process of filling flow along circular channel and rectangular channel, are set up respectively.(2) The thesis presents an overview of numerical methods, including Finite Difference Method(FDM), Finite Element Method(FEM), Boundary Element Method(BEM) and Finite Volume Method(FVM), which can be used to simulate the gas penetration in GAIM. And following the thesis introduces knowledge about meshfree techniques systematically, including the approximation of meshless methods, the selection of weight function, the methods of numerical integral and treatments of essential boundary conditions.(3) A theoretical study has been carried out on the hollow plastic in GAIM process, in which the polymer is non-Newtonian fluid. The mathematic model, which can describe skin-melt thickness formation, is presented. On the base of the model, theoretical analysis has been made to describe the displacement and velocity of gas front and melt front of hollow plastic in GAIM process. The results indicate that the velocity of the gas front accelerates, while the velocity of melt front remains constant during the whole process except the blow-out time. When the blow-out happens, the velocity and displacement of gas front and melt front increase dramatically.(4) Based on the Hele-Shaw flow, the pressure is constant everywhere in the gas region, including the interface between the gas and the melt. Numerical simulations are implemented to calculate the pressure and the length of gas...