Reduction of impact force and stress during high-speed operation based on hybrid control of positioning and force for injection molding machine

Injection molding machines are one of the industrial machines producing plastic products. They have been required to improve repeatability for quality stability and speed up for mass production. Injection molding machines consist of a mold clamping device and an injection device. In particular, it is required that the mold clamping devices have operation with not only repeatability but also methods to avoid collisions between the molds. The devices perform positioning control for opening and closing operations and force control for clamping with specified force. If optimal switching is not possible, the molds will collide and cause damage. Therefore, it is essential to design a controller that switches the control systems appropriately. In addition, speeding up cause strains of the machine’s frame. Positioning control is required to suppress strain of frame while maintaining high speed operation. In this paper, positioning and force control is smoothly switched by hybrid control. It was demonstrated that using optimized hybrid signal which was one of the switching signals improved force response. Furthermore, strain of frame was suppressed using modified Bang-Bang control which was one of the minimum time controls. Finally, it was confirmed that the similar effects can be obtained in the control system that combining hybrid control and modified Bang-Bang control.