Study On Mechanism And Technology Of Precision And Microcellular Injection Molding

With the rapid development of industries such as electron, communication, automobile, and medical plastics, increasing requirements for the plastics products with high precision and high performance have expanded a wide application field for precision injection molding since 1990's. In the recent years, along with fast increasing consumption of computers, mobiles, various optical disk and micro-electron communication products, precision injection molding begins to stride forward in the direction of high speed ultra-precision and micromation.Optical disk is one of the representative products of precision injection molding technology. The precise reproduction of minute pit structure requests the plastics substrate not only of very high planeness, but also very uniform mass and low residual stress as well as low birefringence as being inspected. Generally speaking, it represents the highest level of the present precision injection molding technology. So, extremely high demand has been put forward for the injection molding technique and processing equipment. Aiming at the precision injection molding and microcellular foam molding technologies, the mechanism investigation has been deeply developed in this paper; all sorts of factors affecting precision injection molding are analyzed in the aspects of raw material, processing technique, machine and equipment. On the basis of systematical discussion of precision injection molding technology and different effect factors, the mechanism and technology of optical disk injection molding are emphatically investigated, especially the influence of filling, compression and packing stage on the quality of optical disk products.According to the characteristic of injection molding process of optical disk, Leonov constitutive equation is chosen based on analysis of flow-induced and thermally-induced residual stress and mass unevenness, and the mathematical model of injection compression molding of optical disk is developed. In consideration of the boundary condition of melt front, cavity surfaces, and melt inlet, FEM/Control Volume method is applied in numerical simulation, PVT equation and stress-optical relationship are also employed to investigate effects of different injection speed (switch time), compression speed, compression stroke on the shrinkage and mass unevenness of optical disk. Thereby, the appropriate processing parameters for injection compression molding of optical disk have been obtained.Comparison of volumetric shrinkage is made between conventional injection molding (CIM) part and injection compression molding (ICM) part. The...