The extruder screw has the principle of single screw extruder: the solid conveying melt supercharging and pump mixing stripping and devolatilization, but not pure.

Extruder screw extrusion process of the research about points three links: 1, to clear up two or more of the polymer and material changes of state in the process of extrusion, mixed form, structure change process, and the relationship between the mixture and performance; 2, as the extruder screw, extrusion forming at the time of the reaction process, speed, performance and screw configuration, operating conditions between inner link, establish model, is used to guide the reaction extrusion molding; 3, polymer in the extrusion process of state change law of conveying principle of solid melt conveying exhaust truth and law, establish the mathematical physical model, used to direct the design of extruder screw and extrusion process optimization, repair the extruder screw surface hard chromium plating methods are available, and chromium is wear resistance and corrosion resistance of metal, but the hard chromium layer is easy to fall off.

The screw of extruder is rotated inside the barrel, and the friction between the material and the two is gradually worn on the working surface of the screw and the cylinder. The diameter of the screw is gradually reduced, and the diameter of the inner hole of the cylinder is gradually increased. In this way, the diameter gap between the extruder screw and the cylinder is increased with the gradual wear of the two. , however, because of the barrel in front of the nose and shunt plate resistance has not changed, which adds to the forward extrusion material leakage flow, the material feeding direction from diameter clearance flow increase, the result of extruder screw production decline. The extruder screw causes the material to stay in the barrel to increase, resulting in the decomposition of the material. If it is polyethylene, the decomposition of hydrogen chloride gas enhances the corrosion of the extruder screw and cylinder. Materials such as calcium carbonate and the filling material such as glass fiber, can speed up the screw and barrel wear, because the material does not have uniform plasticizing, metal object or a mixed in the material, to rotate the screw torque force suddenly increases, the torque beyond the ultimate strength of the screw, the screw twist off. This is an unconventional accident.

The extruder screw should be considered according to the actual inner diameter of the cylinder, and the outer diameter deviation of the new screw rod should be made according to the normal clearance of the cylinder. After the screw diameter of extruder screw diameter is processed, the thermal spraying wear-resistant alloy is then machined to the size. This method generally has professional spraying factory to repair, the cost is relatively low. Wear resistant alloy for thread part of the screw thread. Weld 1~2mm thick according to the degree of wear of extruder screw, and then grind the screw to the size. This kind of wear-resisting alloy is composed of C, Cr, Vi, Co, W and B, which increases the resistance of the screw and the corrosion resistance. Professional surfacing factory is very expensive for this kind of processing, except for the special requirement of screw, it is seldom used.