Numerical Simulation And Optimization Of Rapid Heating Cooling Molding

In recent years, with the rapid development of the plastic industry, plastic productsare widely applied to various industries. Injection molding is one of the most commonlyused plastic molding techniques. With the rapid development of electronics,communications, automotive industry, optoelectronics and other industries, thetraditional injection molding can not meet the demand, Rapid Heat CycleMolding(RHCM) injection emerged. RHCM injection use dynamic mode to controltemperature, and the mold is heated to a high temperature to improve the fluidity andfilling ability of the melt; cryogenic cooling medium is used in cooling phase, so themelt is rapidly cooled to a low temperature, Thus RHCM is a plastic moldingtechnology with non-weld lines and high-quality surface. The technology is a greeninjection process while it can remove a secondary spray, reduce production costs,improve the quality of products and protect the environment.This paper studied the characteristics of RHCM process by combining the theoricalmethod, numberical simulation and experimental validation, and did comparision withconventional injection molding to verify the superiority of RHCM technology. Detailsare as follows: firstly, according to the RHCM technology’s features such as hightemperature and short cycling time, this paper proposed a reasonable simplification andassumption of treating melt filling and packing process as a unified compressible fillingprocedure and derived continuty equations, momentum equations and energy equationsfrom basic laws of fluid mechanics. Then the conventional injection mathematicalequations are listed to compare with the above equations.Choosing a particular brand TV shell as research object, this paper establishedthree-dimensional model consistent with real melt flow behavior, simulated the filling,packing, cooling and warping process, then obtained the results of temperature, pressure,weld line and warpage. Comparisons with the conventional injection moldingtechnology showed that RHCM can obtain lower melt viscosity, reduce the generationof weld lines and warpage during heating phase, benefiting high temperature.Meanwhile, RHCM ameliorated melt flow behavior, obtained a uniform srtucture andimproved the crystallinity and surface hardness of plastic parts because of its smallershear rate due to smaller injection pressure.Six main parameters of RHCM are identified: melt temperature, mold temperature,injection pressure, injection time, packing time and packing pressure. This paper simulated the impact of various process parameters on the warpage and the level ofimportance are as follows: packing pressure> packing time> cooling time> injectionpressure> melt temperature> mold temperature. Meanwhile, the optimum parameterscombination is got, and the experiment proves the feasibility of the program.The finite element analysis model of RHCM mold was constructed. The thermalresponse during heating and cooling stage was simulated respectively throughconstructing the thermal response analysis model. Compared with conventionalinjection molding, the heating, cooling efficiency and temperature uniformity of RHCMis better. The study has also shown that heating, cooling efficiency and the temperatureuniformity could be improved by channels with small diameters and tight arrangements.