In this paper the modeling of a typical injection cycle for an injection molding machine (IMM) is examined. Both the mold filling and mold packing phases of the cycle are examined along with a critical fill-to-pack transition. The novelty in this modeling work is that the non-linear model considers both the machine hydraulic actuator and polymer flow characteristics in extensive detail. The resulting model will provide simulation capabilities to facilitate machine controller design; however the actual controller is not the focus of the current work. The modeling is based on (a) the characteristics of digitally controlled electrohydraulic valves, (b) the dynamics of the hydraulic actuator ram system, and (c) the gross polymer melt behavior determined from simple polymer engineering models. The simulation model is validated against experimental data and demonstrates the availability of a relatively accurate system model for full cycle control of this electrohydraulic system.