Numerical Simulation, Optimization And Control Of Filling Process In Injection Molding

Injection molding is the mostly used processing technology for all thermoplastic materials and part of thermoset materials. The process of the injection molding is quite complicated because of the character of the material itself and the complexity of processing conditions. For a long time, the control of the injection molding process and the design of the mold mainly depended on the experience of the designers, and the reasonability of the design can only be verified by trial and error. The cycle was quite long and the cost was huge.By establishing the physical and mathematical model of injection molding process and adopting effective numerical algorithm, the process can be simulated numerically so that the structure and the property of the part can be predicted and the possible problems can be found at the design stage. The embarrassment of finding problems in the stage of mold trial after the manufacture of the mold can be avoided.However, the numerical simulation of the injection molding just behaves as numerical experiments. The designer's experience is still required and the determination of the design is mainly based on the input provided by the user and his correct judgement and explanation on the output. Combining the design optimization technology and the numerical algorithm, computer can determine the molding parameters and the gate locations automatically. These can remarkably reduce the requirements to the design personnel of the injection molding and improve the design quality.Although the improved molding process can be obtained by simulating and optimizing the injection molding process, usually, the process still cannot be proceeded as what we expect because of the mechanical erosion, friction and the variation of the environment factors in the real process. The on-line control on the injection molding to make the manufacture variables vary according to what we expected is very valuable practically.This dissertation studies on the simulation, optimization and control of the filling stage in plastic injection molding. The research work is composed of three parts: 1. Implicit algorithm is utilized to track the movement of the melt front in the filling stage. 2. According to the mostly occurred injection molded part defects and the analyses on the factors that cause those defects, optimization model has been established and mold configuration and processing conditions are optimized subsequently. 3. Theory of automatic control has been involved intoinjection molding to make the molding process proceed according to the optimized processing conditions. The disturbance from the environment is eliminated or reduced and parts quality is guaranteed. The contents of each chapter are as follows:In Chapter 1, based on literature reviews, the history and current status of the simulation, optimization and control technology of injection molding is illustrated. The popular software on analysis and design of injection molding are introduced and comparison has been made among them. The development tendency of the injection molding software is concluded. In addition, some elementary knowledge on injection molding is introduced.In Chapter 2, implicit algorithm is employed to track the moving melt front to achieve the numerical simulation of injection molding. According to the mass conservation of each control volume, governing equation of which the variables are nodal pressure and fill factor is established. By solving the equation iteratively, the pressure field and fill factor field are obtained. The position of the melt front is therefore determined by fill the factor field. The filling situation in the cavity in each time instant can be obtained as well. The employed implicit algorithm can describe the transient process in filling stage more reasonable and avoid the limit of Courant condition. The calculation efficiency is improved.Chapter 3, 4 and 5 are focused on the optimization of mold configuration and processing conditions of filling stage.In Chapter 3, the optimizing design o...