The screw of the plastic extruder works under high pressure, high temperature, high mechanical torque and high friction environment for a long time. Generally, the screw has undergone surface nitriding treatment to increase the surface hardness to improve the wear resistance.
However, if the causes of wear are ignored and the wear is not minimized, it will inevitably greatly reduce the working life of the extruder screw. The following 2 points introduce the reasons for the wear of the extruder screw and the methods to reduce the wear:
Each plastic raw material has an ideal plasticizing processing temperature range, so the processing temperature of the barrel should be controlled to make it close to this temperature range.
When granular plastic enters the barrel from the hopper, it will first reach the feeding section. Dry friction will inevitably occur in the feeding section. When these plastics are not heated enough and melted unevenly, it is easy to cause increased wear on the inner wall of the barrel and the surface of the plastic extruder screw. Similarly, in the compression section and homogenization section, if the molten state of the plastic is disordered and uneven, it will also cause increased wear.
Because some plastics are added with strengthening agents, such as glass fiber, minerals or other fillers. The friction of these substances on metal materials is often much greater than that of molten plastics.
When injecting these plastics, if a high speed is used, while increasing the shearing force on the plastic, it will also cause the reinforcement to produce more shredded fibers. The shredded fibers contain sharp ends, which makes the plastic abrasion force of the extruder screw is greatly increased. When inorganic minerals slide at high speed on the metal surface, their scraping effect is not small. Therefore, the speed should not be adjusted too high.