1. The screw of the extruder rotates in the barrel, and the friction between the material and the two causes the working surface of the screw and barrel of the extruder to gradually wear out: the diameter of the screw of the extruder gradually decreases, and the diameter of the inner hole of the barrel gradually increases . In this way, the gap between the diameter of the extruder screw and the barrel increases gradually as the two gradually wear out.
However, since the resistance of the head and the splitter plate in front of the barrel has not changed, this increases the leakage flow rate of the extruded material when it advances, that is, the amount of material flowing from the diameter gap to the feed direction increases. As a result, the output of the extruder is reduced. This phenomenon increases the residence time of the material in the barrel, causing the material to decompose. In the case of polyethylene, the hydrogen chloride gas generated by decomposition strengthens the corrosion of the extruder screw and barrel.
2. If there are fillers such as calcium carbonate and glass fiber in the material, the wear of the extruder screw and barrel can be accelerated.
3. Because the material is not plasticized evenly, or there is metal foreign matter mixed into the material, the torque of the screw rotation of the extruder suddenly increases. This torque exceeds the strength limit of the screw of the extruder, causing the screw of the extruder to break. This is an unconventional accident damage.