Control Principle And Performance Research On The Electro-hydraulic System Of High-Precision Two-Plate Injection Molding Machine

As one development trend of high-precision injection molding machine, two-plate plastic injection molding machine has been paid more and more attention to by manufacturers. The design of its hydraulic control system, which has excellent dynamic characteristics of fast response speed, high precision and low overshoot, is one of the most sophisticated problems needed to be solved and a successfully developed hydraulic system with high performance will make big economic profits. Research presented in the paper plays an important role in the accomplishment of the national supporting project named 'Research on Precision Injection Molding Machine with High Efficiency and Low Energy Consumption'.On summarizing researches related to hydraulic system at home and abroad, the design principles of electro-hydraulic system is presented by taking the two-plate injection molding machine 'HT1600' of Ningbo Haitian Co., Ltd as a research object. After analyzing the systems, mathematical models are built for the machine's typical working processes of which dynamic characteristics are simulated on the platform of MATLAB/SIMLINK6.0. Then an optimal control method adopting the idea of GA(Genetic Algorithms) is introduced to overcome shortages of the system's dynamic properties shown in the above simulation results. The main research contents go as follows:1. According to the operating principles of two-plate injection molding machine, the design process of the hydraulic control system is presented which includes the plate open-close module, plate locking module, injecting module and pushing-out module.2. An equivalent mathematical model of the electro-hydraulic valve which controls the process of open-close plate and injection as well as the tee proportional valve which controls the pushing-out action is established respectively, meanwhile, the influencing factors of each pipeline flowed through by fluid stream are analyzed.3. On the basis of the modeling, operation processes of open-close plate, push-out action and injection are simulated on the platform of MATLAB/SIMLINK6.0 and their dynamic property curves are shown and analyzed.4. To cope with the deficiencies of the system response, a double feedback closed-loop control is adopted, which meets the requirements of speed, pressure and position during machine's operating process. In the process of pressure maintaining, pressure and flow control switchover method combined with GA was adopted and thus, a satisfying response curve with fast speed, high degree of accuracy and low overshoot is got.