Abstract
The load characteristics and control of water hydraulic system for water-assisted injection molding (WAIM) are investigated through modeling and simulation. WAIM is an innovative process to mold plastic parts with hollow sections, coming with big advantages: high production efficiency and quality at low cost. The load characteristic is complicated owing to physical properties of polymer, distribution of temperature, flow rate and water channel geometry etc. The load pressure and flow rate are investigated with CFD simulation. An accumulator and a supercharger are applied in the water hydraulic system which is modeled in MATLAB and developed in laboratory. A differential pressure control strategy is provided to regulate the water injection pressure by a proportional relief valve. PI control is used and the steady-state error of step response can be reduced close to zero with integral compensation in closed-loop control. Finally, slope control of injection pressure is studied based on the developed system in simulation. The aim of this study is to improve the control process of WAIM based on the new design and differential pressure control. In addition, this provides an application and practice of water hydraulic proportional control technology.
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