Study On The Filling Behaviors Of Ipp Microarray Structural By Micro Injection Molding

With the development of MEMS and MST, Micro-injection molding (MIM) is obtaining more attention as an important micro forming process, which is becoming more and more mature. Micro injection molding products are widely used in the field of aerospace, medical, automation, automotive industry, optics as well as daily life. Micro-injection molding has many good features, such as, low production cost, widely adaptability of materials, applicability for complex geometry and size, continuously and automatly production and so on. Now, researchers are fouce on the aspects of the micro injection molding equipment, the micro-mold manufacturing and processing, the micro molding material selection, micro-molding process control, the micro-molding forming theory and numerical simulation analysis, the micro products quality characterization of the micro-injection molding technology.In this work, The influence of processing parameters on the filling behaviors of iPP microarray structural was investigated by numerical analysis and injection molding experiments. The main contents and conclusions are as follows:(1) Product Modle, The three-dimensional model of the product is drawed by the Pro/E3D graphics software, which size is16mm×12mm×3mm, the cylinder diameter is500μm, and there is2mm distance between columns. Before we use the Moldflow software to simulate the melted polymer filling process, we should first mesh the modle. In order to obtain the accuracy analysis and uniformity mesh, we use the Hypermesh software to mesh the product model, and the cavity and the micro-structure is meshed by different meshing strategies, the global edge length of the base and the cylindrical is0.5mm and0.1mm. Then the model is imported into Moldflow software to create the runners and then starting the simulation analysis. From the filling analysis result we know that the gating system is reasonable and the product is filled fully. The plastic melt flow front is similar to traditional injection molding which likes fountain. The injection speed has a great importance on the micro cylinder filling height, the filling height is increasing follow the injection speed increasing. The cavitations generate in the filling process distributing on the top of micro-cylindrical or the edge of the substrate. The shape of the melt flow in the micro-cylindrical is gradually becoming spherical crown, and is affected lessly by the injection rate, because the mesh node distribution limited the position and the shape of the melt flow front.(2) The mold for MIM is designed and manufactured, which contains main structure and micro cavities insert. It’s convenient to replace the micro cavities and improve the overall service life of the mold. Considering the effects of the residual gas on the products filling, we added the exhaust settings in the micro cavities inser which let it easy to rule out the residual gas from the cavity, it is helpful to avoiding the burning orthe and bubbles, we don’t need to make the mold vacuum advanced before the injection. Demould way is the traditional ejection, templates and ejection mechanism can be manufactured by the traditional method of metal processing, mould frame and insert are made by the machining and EDM processing. The design of mould structure is reasonable and simple.(3) The iPP microarray structural was made by micro-injection molding machine, cut by the bio-slicing mechanism. The morphology of the micro-cylinder was observed and the height of the micro-cylinder was measured by POM. In the injection filling process, it mainly fill the base in the earlier stage, the variation of micro-column height is relatively stable. After the completion of the base filling, the cavity pressure increases resulted in the micro cylindrical quickly filled; With the increasing of injection speed, the height of the cylinder in the early filling is increase, at the same time, micro cylindrical filling height is rising at the same filling stage. The first row micro cylindrical height change is not only associated with the injection speed, but also the distance of the melt flow and micro cylindrical. Because of the impact of the mold wall, inertia and melt velocity, turbulence was appeared when the melt front went through the micro cylindrical, the shape of the flow front is acentric ellipsoid crown, the higher is injection speed, the more serious of the acentric ellipsoid crown. The shape gradually developed into spherical accompanied with the filling was going on.