Parameter Optimization Design On Dynamic Injection Molding Technology And Service Quality-oriented Issue For Plastic Products

Injection-molded plastic parts hold the important proportion in modern life. Recently, there exist the increasingly high molding and service quality requirements of the plastic parts. On the basis of the injection molding simulation technology and the modern optimization method, engineers efficiently solve the injection molding design problems on process parameters and mould system, and improve the quality of the part and manufacturing efficiency.However, there are two critical issues in injection molding field. One is the current literatures on injection molding optimization and design are mainly based on the conventional injection molding technology (CIMT), which limits the further improvement on quality of the plastic part. The other is that researchers mainly focus on the molding quality of the part, neglect service quality of the parts which is one critical performance index to ensure the safety under complicated mechanical load conditions. According to the issues mentioned above, the main work of this dissertation have been finished as followed:Firstly, as an innovative technology, notably, many experimental investigations have indicated that dynamic injection molding technology (DIMT), which is a vibration-aided injection molding technology, can reduce energy consumption and improve the molding quality. However, there are less literatures that introduce the relevant work on the numerical computation method on DIMT. Therefore, a numerical method for DIMT is proposed firstly. By using the finite element method, dynamic filling and packing are realized in flow analysis of the injection molding. The pressure in the mold by this method is clarified to be a good agreement with the result of the experiment observation. Many numerical analysis are performed to study the effect of the parameters of DIMT. The results indicate that pressure response in cavity distinguish with the conventional case, the frequency of the fluctuating pressure is the same as the frequency of the molding process, fluctuating level are relevant to the amplitude of the molding process, and different phase can induce the change of the magnitude of the final injecting pressure. Moreovers, the dynamic form can be changed to be any available types of dynamic form to investigate the molding mechanism of DIMT. Therefore, this method is an important improvement for injection molding, and can be used as a numerical tool to investigate more behavior of DIMT.Secondary, molding quality can be improved by DIMT from experiment observation, but there are less process parameter optimization research to investigate the effect of DIMT. For the first time, the optimization model on dynamic injection molding parameter is proposed based on the numerical DIMT mentioned above, which is an important extension in injection molding optimization for reducing the warpage of the parts. In order to avoid the constraint between amplitude factor and frequency, a type of dynamic filling is employed. As a comparison, the dynamic optimization issue and the conventional optimization issue are both solved by using Kriging surrogate based optimization method. Results and discussions reveal that DIMT is more available for reducing the maximum warpage of some types of plastic parts than the CIMT. However, for the large, long and narrow parts, DIMT could fail due to the "local vibration effect". Therefore, DIMT has a limitation.Finally, the service quality is important for plastic part (especially for engineering plastic part) under the complicated service conditions, however, there is a lack of optimization and design method to take the influence of the molding defect during service into consideration. Therefore, an entire analysis from molding to service is suggested for the service quality-orientated issue. During the service analysis, the molding residual stress and warpage defects are regarded as the initial stress condition and assembly displacement condition, respectively. This method is effective and overall, and makes an extensive contribution for investigating the mechanical behavior of the plastic parts. Moreover, kriging surrogate-based optimization method is employed to solve molding paramter optimization issues. The results show that service stress of the injection molded part are well reduced, and the service capability of the part is improved by optimizing the molding conditions. It is worth to note that geometrical and size optimization of the part structure can be detailly designed by using this strategy. Therefore, this optimization and design method has a significantly meaning for engineering plastic parts in some strategy field.