Simulation Research On Injection-Compression Molding For Transparent Plastic Panel

With the rapid development of polymer engineering, large transparent polymer parts are widely used in automobile and aerospace industries, for example, the fabrication of car glasses and large transparent aeroplane coverings. Due to their unique applications, they should have good mechanical and optical qualities. However, how to design fit procedure to produce such high-quality products is a great concern. Earlier research turned out that when traditional injection molding is used to make such large transparent polymer parts, non-uniform distribution of pressure, temperature and fiber flow line on the product may give rise to residual stress during the molding process and bring about unequal shrinkage on different points of the product, especially edge and angle areas, after molding is done, as a result bring defects like warp and birefringence which will make negative impacts on the mechanical and optical quality of the product. To solve the problem, an improved Injection-Compression Molding (ICM) is been noticed, especially on the aspects of molding process analysis and parameter optimization.Compared with injection molding, ICM allows mold to move, adding a compression stage at the end of the inject process. This extra work helps to control the variation of polymer temperature and pressure, and eliminate the problem of residual stress and uneven shrinkage on root. As the late start on ICM in China, little information has been obtained on ICM in areas like parameter variation, utility of ICM and noticing, which are of great value to be used to design procedure for specific parts making.Using computer-based numerical simulation technique, base on nonlinear numerical algorithm, this paper uses multi-physics calculation method to simulate ICM on plates with different geometric structures thoroughly, and compared its results with ones done by traditional injection molding. Following conclusions are obtained:There is a consistent pressure distribution in the mold when ICM is done. Besides, the velocity of compression, the starting gap between the two molds and the switch time between injection and compression period affect the pressure curve on the correspondent aspects of amplitude, variation intensity and phase.Compared with injection molding, ICM can greatly reduce the shrinkage of the final product. In addition, length of the fiber flow line and temperature can affect the shrinkage of the product. Shorter fiber flow line, more even temperature distribution can lead to lower and more even shrinkage distribution.ICM is not fit to produce products with random geometries. For parts with irregular geometric structures, the pile up effect caused by the unsteady flow of polymer at corner and non-uniform cross section of the cavity can bring unequal stretch of fiber flow line, making negative affect to the product quality. So it is more preferable to use ICM to fabricate product with symmetric geometric structure.