Abstract: Precision and energy-saving are development tendencies of injection molding industry. In view of the high energy consumption and low response of the traditional hydraulic system for injection molding machine , a servo motor driven constant pump hydraulic system is designed for precision injection molding process, which uses servo motor, constant pump and pressure sensor instead of common motor, constant pump, pressure and flow proportion valve. This hydraulic system has the advantages of energy saving, quick response easy and accurate control. Then a pressure and speed control strategy based on fuzzy sliding mode control is proposed for accurate control of pressure and flow of hydraulic system in the injection molding process. Moreover, according to the characteristics of pressure/flow coupling in the injection molding process, a control strategy for pressure/speed switching is proposed. Test results show that this hydraulic system features quick response, high-accuracy control of pressure and speed, and good energy-saving effect.

Key words: Energy-saving, Hydraulic system, Precision injection, Servo drive, Slide mode control