Plastic screw extruder

The invention discloses a plastic screw extruder which comprises a feeding cylinder, a PLC, a vacuum pump, a machine barrel and a screw, wherein the feeding cylinder is arranged at the feed opening of the machine barrel; a material level sensor is arranged at the upper end of the inner wall of the feeding cylinder; a negative pressure fan is arranged above the feeding cylinder; the negative pressure fan and the material level sensor are connected with the PLC; the screw is arranged in the machine barrel and connected with a motor; the screw comprises a positive rotation screw, a centre rotating shaft and a reverse rotation screw; a plurality of wheel fins are arranged on the centre rotating shaft; an electrical heating jacket is arranged on the periphery of the machine barrel; a plurality of heat preservation housings are arranged outside the electrical heating jacket at intervals; rock wool is arranged in the heat preservation jacket; a temperature sensor is arranged in the machine barrel; and the vacuum pump is communicated with the machine barrel through a vacuum pipeline. The plastic screw extruder improves the product quality, realizes automatic heating control and automatic feeding, prevents material from overflowing from the feeding cylinder and greatly reduces the working strength of workers.