Experimental Research On The Improvement Of Micro Structure Duplication Using Electrothermic Variotherm Injection Molding Technology

Nowadays conventional injection molding technology has been matured. It is difficult to improve the molding precision further. But as the higher requirement of molding quality is proposed especially in micro structure molding, conventional injection molding technology can’t make it satisfied, so a brand new injection molding technology is needed.Micro fluidic chip is a typical plastic part with micro structure. It has two kinds of defects, such as weld line, flashing, sink mark, mold sticking, warpage in macro aspect and incomplete duplication in micro aspect. The molding precision of micro channel, which is the emphasis in research of micro fluidic chip molding, has been improved in some extent, but circular bead still exists. Conventional injection molding technology is tough to improve the molding precision of micro structure. So variotherm injection molding technology was imported to eliminate circular bead.Variotherm injection molding process was different from traditional injection process, so is the equipment in experiment. Chose heat pipe as heater after analysed several heating methods. Set up electrothermic variotherm injection molding system based on Siemens S7-200PLC. The whole system concluded injection machine, injection mould of micro-fluidic chip, electrothermic variotherm injection molding control system. The control system contained heating device, cooling&draining device, outer control equipment. The key to ensure the process of injection molding fluent was signal interlocking between outer control equipment and control system of injection machine.Designed and manufactured a set of injection mold of micro fluidic chip which was2cavities of substrate and cover in a mould with core pulling in solid plate. Through optimal design of distribution of heating&cooling pipes, improved the efficiency of heating cycle and uniformity of heat distribution to ensure the macro quality. After the whole system was set up, made experiment to optimize the process parameters.The influence of process parameter to molding qualify was clear by single factor experiment. In the meanwhile the range of every parameter for the best molding qualify was achieved. The basic principle was that guarantee the molding quality of micro structure and then get fine macro quality of micro fluidic chip. Univariate analysis revealed that mold temperature, melt temperature, injection speed and injection pressure are significant factor affecting molding accuracy. Then made orthogonal experiment of four factors at thre different levels. It came to a conclusion that mold temperature was the most important impac factor in micro structure molding. Through optimum technological condition combination, perfect micro fluidic chip was obtained.