Development Of Control System For Precision Micro Injection Molding Machine Based On PLC

With the upgrading of injection molding technology, plastic products have been applied to each field of national economy. In recent years, micro plastic product’s demand is increasing, while, molding accuracy requirements are increasing. Traditional injection molding machine can not satisfy the demand of micro injection molding. Therefore, equipments and process around micro products become the focus of attention. However, the research work on micro injection molding in China falls behind that of foreign countries. In this paper, micro injection molding machines as the research object, the micro injection molding equipment and control systems were studied. The main research contents and results are as follows:1. According to recent research results on micro injection molding, a design of screw-piston micro injection molding machine driven by electric and hydraulic is proposed. The accuracy control of the injection volume is realized by adjusting the speed and angels of the stepper motor. The schematic of the hydraulic control system is designed and the hydraulic system is manufactured by selecting the hydraulic standard components. Otherwise, the structures of the injection unit are newly designed. The debugging result suggests that this hydraulic system can meet the basic requirements of the micro injection molding process well.2. In this paper, micro injection molding machines as the research object, the control system of the micro injection molding machine is developed by using GX Developer and Levi Studio. Firstly, the hardware criuits are designed and manufactured according to the micro injection molding process. Secondly, the PLC control programs are developed based on PLC, including stepper motor driving, analog value control, manual mode, semi-automatic mode, automatic mode, temperature control, alarming, etc. Lastly, the programs of HMI are designed to communicate with PLC. So, the control system is equipped by some basic function, such as fuzzy control, mold temperature control, HMI communication, testing data saving and displaying, generating the testing curve, etc.3. The cylinder temperature control system is established by using the fuzzy PID technology. We develop the program by combining the fuzzy technology and PID control system. Finally, fuzzy control system realized by searching the table online and it is used in the cylinder temperature control. The experimental results prove that the cylinder temperature control system is stable and accurate enough to meet the requirements of micro injection molding.