Physically-Based Model of Thermoplastics Injection Molding for Control Applications

Abstract

Abstract A non-linear mathematical model of the thermoplastics injection molding cycle is presented. The model is formulated based on the conservation equations for the filling, packing, and cooling phases. The whole process is divided into subsystems including the hydraulic system, ram-screw, barrel, and polymer delivery system. It is found necessary to account for polymer melt elasticity as well as the non-Newtonian behavior of the polymer melt flow. The growing solid skin in the sprue, runner, and gate are considered. The governing equations are solved numerically. Model predictions are in good agreement with experimental data for the injection molding of high density polyethylene. The resulting model is a useful tool for the study and design of injection molding controllers, machine parameter selection, and equipment design.