The Analysis Of Complex Flowing Behavior Of Injection Molding Parts With Micro-features

As the development of MEMS and Micro/Nano technology, the micro forming technology had a rapid development, and the micro injection molding technology has becoming the hot spot of all the countries. Due to products with the micro injection molding have tiny size or highly accuracy level, the traditional injection molding theory and technology shall not be used for micro injection molding. At present the micro injection molding theory is not perfect, and the micro injection molding process methods still need further exploration.Products of Micro injection molding can be classified into two categories, one kind is the drawing of the size is microscopic scale; The other kind is the macro scale parts with microscopic features.In this paper we simulated the filling process of injection molding with micro-features, mainly discussed the complex flow behavior in the micro characteristics of entrance areas. The main work includes:1. The flow in entrance areas of micro channel is similar to variable pressure drive square lumen flow. Through the coupling simulation of the microscopic and microscopic parts, we found that the entrance areas cannot be completely filled whenU/η≥100, there will have a vortex.2. Based on multi-scale method we simulate the filling length of micro-channel, not considering the influence of melt shear force in macro-channel. Through the filling simulation of the macro area, we get the history of pressure at the entrance micro channel and melt temperature, then taking the variable pressure function and melt temperature as boundary conditions, we simulate the filling process of the micro-channel used ANSYS CFX. We detailed analyze the influence of mould temperature, injection velocity, pressure at inlet region of micro-channel and width of micro-channel to the filling length.3. We simulate the filling process of micro-channel based on macro and micro decoupling method, considering the influence of melt shear force in macro-channel, and analyze quasi-static square cavity flow. The results show that under the influence of X and Y melt flow directions at the micro-channel inlet region, melt rotate when filling the micro-channel, and then the vortex center appears. If the speed of melt in main channel is bigger, the vortex mingled with air; if the speed is less, vortex is completely full of polymeric melt.