Scale effect on filling stage in micro-injection molding for thin slit cavities

Micro-injection molding is the main method molding complex micro plastic parts accurately at one process. It is more complex than traditional injection molding because of the micro-scale effect. The polymeric flow in micro channels differs from those in macro ones significantly, and the molding theories of traditional injection molding can not be used in micro-injection molding. In this study, the effects of micro-scale, such as micro-viscosity and wall slip, were considered based on the flow characteristics of micro-injection molding, and the mathematical model and the numerical model were built. The simulation of filling stage in micro-injection molding was implemented by hybrid finite element/finite difference/control volume method accordingly. The influence of micro-viscosity and wall slip on filling stage was investigated by numerical analysis. The results indicated that the micro-scale effects have important influence on the filling stage of micro-injection molding, and the micro-scale effects become more and more significant as the gap thickness drops.