Research On The Crank-slide Ejection System Of All-electric Injection Molding Machine

All-electric injection molding machine plays an important role in injection molding industry, compared with hydraulic injection molding machine, which has a high accuracy, good stability, environmental protection and energy saving. Injection system is a very important part of all-electric injection molding machines, the injection system determines the quality of the injection molding process and the performance of the molded articles. The injection system's dynamic part of domestic all-electric injection molding machine is usually consist of servo motor and ball screw, the structure has a high positioning accuracy, repeatability and good features, but the disadvantage is the higher cost and the ball screw is easy to wear. In this paper, a new kind of injection system is proposed to replace the ball screw injection system, which is consist of servo motor and crank slider.The kinematics and dynamics of crank slide characteristics is obtained by simulation and modeling, and the comparison is made with ball screw to research the different properties. Then the experiment is made to find out the different molding performance in injection and packing section of the crank slide and ball screw injection systems, through which the advantages and disadvantages of the crank slide injection system are found out. The advantage is that the crank slide system can provide higher injection speed and quicker response time, the high-speed performance can be better for high-speed injection molding machine. Its shortcoming is the nonlinear structure of the crank slide, which makes the speed of the screw hard to maintain consistent, so that the screw injection speed is more difficult to maintain consistency, screw speed fluctuations will affect the injection molding process, and ultimately influence the product performance.For the nonlinear characteristics of crank slide structure, the paper proposed Smith predictor algorithm to optimize the screw speed control. By the optimized algorithm, the system delay is offset to ensure the consistency of screw speed, reduce the volatility of speed and improve process performance.Meanwhile, for the shortcomings of the injection hold pressure switching mode. The paper proposed an optimized mode based on the screw position switching, in which the screw speed would deceleration before the normal switching position. Thereby reducing the packing pressure fluctuations when switching, so that the melt can be molded stablely. This approach has a good reference for other forms of injection system.