Research Of Design And Optimization For Rapid Heating Cycle Injection Mold

With the rapid development of the plastics industry, plastic products are widely used in all walks of life and penetrate into all aspects of people's lives and production. At present, injection molding has covered 80% of the engineering plastics manufacturing. In recent years, the growing demand of injection molding products for the areas of automotive, construction, household appliances, food, medicine and public health, significantly promoted rapid development and improvement of the technical level of plastic injection molding. Gas-assisted injection molding, water-assisted molding, multi-color injection molding and Hot Runner and other new technologies in the injection molding process have been widely used. In the injection molding process of plastic products, there will always appear all kinds of questions in the inherent and appearance quality, because of molding material, mold, injection machines, auxiliary equipment, forming environment and other factors. However, the development of home appliances, communications, consumer electronics, automotive interior trim, photovoltaic and other industries, has made more demands for plastic products, such as thinner wall thickness, more complex structure, more beautiful surface and higher strength. How to get high-quality plastic parts becomes an urgent problem that should be resolved in engineering.Rapid thermal cycle injection molding (Rapid Heating Cycle Molding, RHCM) technology achieves rapid heating and cooling of injection mold using heating and cooling medium, and implement of injection molding of melt in high mold temperature. It is also called as a non-weldline plastic molding technology. The RHCM technology can get plastic products with superior surface, such as no weld marks, no flow marks, no silver line, with high-gloss. The use of the technology can abolish the spraying process, save the expensive cost of secondary processing. The technology can significantly reduce production costs, at the same time, save energy and materials, eliminate pollution, achieve multi-effects to improve the quality of plastic parts, lower production costs, protect the environment, implement short pieces of plastic flow of the green. It is a promising green injection process.This paper researches the process characteristics and requirements of RHCM. It should be ensured that the temperature uniformity of the cavity surface and high heating efficiency during mold design. The main set form and design principles of heating and cooling pipes are put forward. At the same time, considering the heat water vapor brought to the die, the basic calculation methods of RHCM mold design are established, including the heat transfer coefficient of mold and cooling water and water vapor, diameter of cooling pipe, as well as heat balance analysis in injection cycle.The RHCM mold should realize rapid heating and cooling to the scheduled temperature in the injection molding cycle. The temperature and its distribution of the mold cavity surface directly affects the efficiency and quality of RHCM plastic parts. This paper establishes a finite element analysis model of the RHCM mold heat transfer process of 46-inch LCD flat panel TV, researches the influence of the heating/cooling piping layout on the temperature distribution of mold cavity surface and finds the temperature distribution of mold cavity surface is not uniform, the temperature in the middle of the cavity is higher than that on both sides. Through orthogonal experiment analysis, pipe diameter and distance of pipe center have significant impact on heating efficiency, and the effect of pipe spacing to the temperature uniformity is particularly prominent. Through the integration of the finite element analyse software MSC.Marc and automatic integration optimize software iSIGHT, the temperature uniformity of the cavity surface is regarded as an objective function, the optimization design for the layout parameters of heating/cooling channels is realized. The optimum result improves the temperature uniformity of the cavity surface surface significantly, and obtaines high quality plastic parts in the practice production. Which provides important theoretical basis for mold heating and optimization design of heating and cooling systems for the actual production.Compared to conventional injection mold, main working parts have much larger thermal stress due to temperature gradient and temperature changes, more easily lead to excessive deformation and fatigue failure, affect the geometry and dimensional accuracy of plastic parts and die life. Therefore, the model of mold heat transfer and stress analysis is eatablished to research and analysis stress distribution, deformation and thermal fatigue life distribution of RHCM die. On the basis of the analysis, the best of the die structure design, piping layout, as well as the fixed mode of mold core, is studied. A RHCM mold structure with "part cold gap" is put forward, the cold gap can greatly reduce the thermal stress of mold core, achieve effective control of hot deformation, thereby improve the die life.