Simulation And Experimental Research On Injection Molding Of Micro-structure Plastic Parts

With the maturity of the MEMS technology, micro-injection parts have been used widely especially micro-plastic parts and micro-structure plastic parts. Micro injection molding process is a new branch of the injection molding techniques, now it is stepping into a fast-growing period, but the theory of injection molding is needed further improvement and development.In this paper, a kind of typical micro-structure plastic - microfluidic chip is used for studying. It is found that the chip has the main following defects: surface ripple, flashing, overall crinkling, sink mark in mirco-structure and incomplete duplication. The two latter defects are more difficult to be solved, which is the focus of this research. Firstly, using Moldflow software, simulating the filling process. Based on the simulation results, the single-factor experimental method is selected to analyse each processing parameter affects on the degree of duplication. Finally, the best process parameters are determined with the orthogonal experiment method.The results of single factor experiment indicate that: with mold temperature, injection velocity, injection pressure and melt temperature raising, the opening width of micro-channel will be reduced, that is means the degree of duplication is becoming higher and higher; the influence of holding pressure on the incomplete duplication is complicated, with the increasing of holding pressure, the degree of duplication is decreasing after increasing; holding time has a negligible effect on the duplication, however, it is the main reason for the wrap deformation; the major factors that causes sink mark are mold temperature, melt temperature and holding pressure, sink mark will be occurred when mold temperature, melt temperature or holding pressure is on a too high level or holding pressure is too low level.The results of orthogonal experiment show that: mold temperature is the most important factor in the incomplete duplication, the higher the mold temperature is, the higher degree of duplication can be achieved; compared with mold temperature, injection velocity plays only a secondary role, injection pressure plays the least important role. Ultimately, the best process parameters are determined, which can forming the better chip. This research can be used for analyzing the causes of molding defects of micro-structure plastic parts, it is also helpful for establishing micro-injection product quality prediction model.