Papers by Author: De Qun Li

Abstract: The plastic sheet forming technique is simple and easy to realize, that is why, it is widely used for packaging commodities. Similarly, in In-Mold-Decoration (IMD) molding technology, due to the complex geometry of the membrane and the high requirement of the dimensional accuracy, geometric design and molding technique for the product should be focused on controlling the thickness distribution of shell or membrance plastic products in order to achieve high precision manufacturing. This paper started with analyzing the performance data of the plastic sheet molding material, using nonlinear finite element method and multi-physics coupling method to simulate the plastic sheet forming process, and the result gives the required parameters for product design and quality control. For the thickness deviation, the experimental testing shows that the maximum discrepancy between the simulation and actual result is less than15%. The research proved that computer simulation can contribute to control the inhomogeneity of the shell or membrane so as to improve the design and the quality of manufacturing.

Abstract: Injection molding which is adopted to fabricate transparent plastic panel has merits such as high efficiency and low cost, and is being used widely. However, at the end of injection molding process, product may be affected by uneven shrinkage and as a result, bring defects such as warp to the final part. This can greatly damage its mechanical and optical quality. Injection-compression molding(ICM) can significantly minimize these defects. In the present paper, 3D model and coupled calculation method of flow, temperature and pressure are used to simulate the process of ICM for an irregular geometric transparent plastic panel. This method can not only reconstruct 3D flow front, temperature and pressure field of ICM process in a much more realistic way, but also more fully demonstrate the length of 3D fiber flow line(FFL) and the variation of shrinkage rate and its homogenize process. Due to such improved algorithm, great improvement has been made to accurately calculate the shrinkage rate in depth of the panel and predict its warp data, in comparison to the traditional temperature-volume contraction index method, which has important practical value to guide and design the technological process of ICM.

Abstract: In injection mold, design of gate location is among the most critical factors in achieving dimensionally accurate parts and high productivity of the molding process, since it influences the manner in which the plastic flows into the mold cavity. To automatically predict the optimal gate location of injection molds based on injection-molding simulation, a new and practical method: empirical search method according to the analysis of common optimization methods has been presented in this article. In this method, the gate location scope is initiated by the practical experience of mold designer so that the core for the gate location optimization is construction of empirical library. In order to build the empirical library, in terms of shape and function characteristic of injection-molding part, all the parts are classified six kinds: shell, container, plate, structural part, ornamental part and transparent part, and the corresponding design rules are kept in the empirical library. In addition, this article combines the empirical search method and numerical simulation technique, builds the mathematics model for the gate location optimization of plate part in empirical library and obtains the gate location optimization scheme for this kind of part through one concrete numerical example. The analysis and verification by adopting the software Moldflow testify the optimization mathematics model is effective.