Causes and repair methods of screw barrel damage
Causes and repair methods of screw barrel damageThe cause of damage to the screw barrel
1. The screw rotates in the barrel, and the friction between the material and the two causes the working surface of the screw and barrel to gradually wear: the diameter of the screw gradually decreases, and the diameter of the inner hole of the barrel gradually increases. In this way, the diameter gap between the screw and the barrel increases slightly 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 produced by decomposition strengthens the corrosion of the screw and barrel.
2. If there are fillers such as calcium carbonate and glass fiber in the material, it can accelerate the wear of the screw and barrel.
3. Because the material is not plasticized evenly, or there is metal foreign matter mixed into the material, the torque of the screw rotation increases suddenly. This torque exceeds the strength limit of the screw, causing the screw to twist. This is a very accidental damage.
Screw repair
1. The twisted screw should be considered according to the actual inner diameter of the barrel, and manufactured according to the deviation of the outer diameter of the new screw given by the normal clearance with the barrel.
2. After the thread surface of the abrasion screw diameter is reduced, the wear-resistant alloy is sprayed at high temperature, after grinding the edging, trimming, polishing the tooth bottom and matching the barrel, the service life can reach more than 98%.
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