Nonlinear modeling of an electrohydraulic injection molding machine

This paper examines the modeling of an industrial injection molding machine (IMM) for both mold filling and mold packing. The machine is a Boy 50 Ton system operated by hydraulics with electronically controlled valves. A nonlinear model of the system is determined for the filling and packing stages, then verified against experimental data. The model includes several key aspects of the actual machine dynamics including stick-slip friction, time delays, nonlinear valve flow characteristics, and dead-zones. The model is developed for the purpose of control; this is reflected in the level of detail associated in several of the subsystems. Simulation and experimental investigations indicate the benefits of the developed model for the control of electrohydraulic IMMs.