Research Of Single Screw WPC Extruder Control System Based On PLC

In recent years, as the global forest resource is declining and social’s heightened awareness of environmental conservation, the application of wood also put forward higher request. In this context, a new type of green eco-friendly materials-wood-plastics composites (WPC), which is composited by wood and plastics turns up. Along with the manufacturing technology of WPC gradually mature, a variety of WPC products has come into packaging, landscape, building, military and other fields at home and abroad. Single screw extruder is the main molding equipment in the ma-nufacturing of the WPC products, the extrusion temperature control precision and the speed control of the extrusion motor play a decisive role in extrusion products’perfo-rmance and quality. This article designed a WPC extruder special controller system for the some WPC enterprise in Guangzhou, which is based on the PLC technology process control system and the visualization software, made the real-time monitoring of the running station of the equipment and the control of important parameters come true.Firstly, by analyzing the WPC extrusion equipment and the principle of WPC extrusion, the key factors affected WPC extrusion molding process are presented. Aimed at these key factors, by analyzing the technological process, this paper putted forward the total scheme of the control system and temperature control scheme. The screw running speed is controlled by using the frequency converter drive to run the main motor. The temperature is measured by temperature sensors. It is controlled by the solid-state relay’s connection or disconnection through the output control of the PLC to drive each heater or cooling fan to make the temperature to achieve its setting temperature. This paper analyzed the principle of temperature control and PID control in temperature control scheme.Secondly, the control system is respectively carried out from the hardware to the software. In terms of the hardware, the equipment selection and overall configuration are mainly designed, and in terms of the software, the control system program structure was introduced, and the realized process of main program and each subrou-tine were analyzed in detail.The system’s temperature control is adopted the parameters self-tuning fuzzy PID control, after briefly introduced the theory of PID control, this paper analyzed the implementation of PID algorithm in this program, including PID controller configuration and PID self-tuning. The results of self-tuning met control request by the experiments. PLC ladder program of the algorithm is prepared by using the programming software TIA Portal V11, and part of the actual adjusting curve and algorithm routine was given. The effect of temperature control by experiment is good—heating time was short, at the same time the temperature overshoot was not more than1℃.Finally, according to the design principle and user requirements, this paper designed the touch screen interface of the extruder control system, and realized com-munication with PLC. The interface realized the real-time monitoring and operation of the setting temperature, real temperature and the speed of motor. It also can display and query alarm information. It can show the specific content of the alarm, and can browse alarm messages what happens through the alarm directory.