Warpage Optimization Study For Injection Molding Surface

Injection molding is one of the main methods of plastic processing with some defects in the process, such as cavitation, short shots, warpage and so on. As an important index for evaluation of products quality, warpage which is closely related on process parameters has become a hot research within the area. In this paper, the upper shell of one mobile phone with serious warpage has been taken as an example for injection molding process parameters optimization. The approximate proxy model for finding the best parameters has been established and the smallest warpage has been gotten. the test results show that, the warping problem has been well solved. The main research contented:(1) First, a reliable finite element model for injection of the shell has been established and the warpage of CAE simulation has been carries on. Then the reliability of numerical simulation has been verified by comparing the design and the simulation value of clamping force and so on.(2) By using the method of multi factors orthogonal experiment, the influence of process parameters on the quality of products has been analyzed through thesensitivity factors, melt temperature and injection time were proved to be the main factors for warpage. According to the number of the main factors affecting the warpage, moving least square (MLS) response surface model is selected as warpage optimization model, and the accuracy of the surface construction of MLS method were verified.(3) Latin hypercube sampling has been used to get the sample data of melt temperature and injection time as the independent variable, and then the corresponding warping deformation has been obtained through the finite element simulation to be as response value.(4) The response surface reflected the variables and the response values was constructed based on MLS, the particle swarm optimization was used to find the minimum amount of warpage on the surface and the coordinate melt temperature and injection time.The results showed that the injection molded part was good, without warpage, shrinkage, cavitation and other defects. Also the contour lines of the shells are consistent, and the clearance was uniform after assembling, satisfied production requirements without flash and scraping hands.