The control method of the extrusion of the net sleeve machine

Usually, the extrusion process of the net sleeve machine adopts a simple open-loop control, that is, it is controlled according to the preset value. During preparation, parameter values, such as clamping force, cycle time, temperature, etc., are pre-set; they are maintained by the machine during production. For example, the mold temperature can be maintained by controlling the temperature of the heating fluid, and the plasticizing temperature can be maintained by controlling the power of the external heating device. This control method is simple in structure, but has poor anti-interference ability and relatively low control temperature. At present, more extruders use closed-loop control, that is, control according to the deviation of the online measurement value and the set value. The closed-loop control system adopts negative feedback loop, which has strong anti-interference ability. When the injection speed, injection pressure, cavity temperature, cavity pressure, melt temperature and oil pressure are deviated due to disturbances in the production process.

The extruder is mainly controlled by temperature, and the temperature zone of the barrel part varies from 3-10 temperature zones according to the length of the screw. The barrel temperature control has two functions of heating and cooling, and the cooling can be air-cooled, water-cooled or oil-cooled. Different production lines use different dies, so the number of temperature zones of the dies is also different. Due to the different factors such as the size of the die head and the barrel, the lag of the system is different, which brings some difficulties to the control, especially in the case of feeding materials, it can ensure good dynamic performance. In some production lines, there will be multiple extruders, and there will be more temperature zones at this time.

The control of the screw is mainly DC drive to control the speed. When the system has a metering pump, it is necessary to control the barrel pressure, and the pressure is stable to ensure the stability of the extrusion volume, but this pressure belongs to high pressure and is easy to cause fluctuations. The system must have a complete protection function. When the temperature is abnormal or other faults, it should be able to stop in time or do other corresponding treatments to prevent damage to the screw.