PHYSICALLY-BASED MODEL OF THERMOPLASTICS INJECTION-MOLDING FOR CONTROL APPLICATIONS

A non-linear mathematical model of the thermoplastics injection moldin g cycle is presented. The model is formulated based on the conservatio n equations for the filling, packing, and cooling phases. The whole pr ocess is divided into subsystems including the hydraulic system, ram-s crew, barrel, and polymer delivery system. It is found necessary to ac count for polymer melt elasticity as well as the non-Newtonian behavio r of the polymer melt flow. The growing solid skin in the sprue, runne r, and gate are considered. The governing equations are solved numeric ally. Model predictions are in good agreement with experimental data f or the injection molding of high density polyethylene. The resulting m odel is a useful tool for the study and design of injection molding co ntrollers, machine parameter selection, and equipment design.