Date：2018-07-18

Cause of damage to the screw barrel

1 The friction among the material and the screw and barrel makes the working surface of the screw and the barrel to wear gradually: the diameter of the screw is gradually reduced, and the diameter of the inner hole of the barrel is gradually increased. Thus, the matching diameter gap between the screw and the barrel increases gradually. However, since the resistance of the front head and the splitter plate is not changed, this increases the leakage flow when the extruded material advances, that is to say, the amount of material flowing from the diameter gap to the feed direction increases. As a result, the extruder production is reduced. This phenomenon causes the residence time of the material in the barrel to increase, causing the material to decompose. In the case of polyethylene, the hydrogen chloride gas produced by the decomposition enhances the corrosion of the screw and the 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 the barrel.

3 Since the material is not plasticized evenly, or metal matter is mixed into the material, the torque of the screw is suddenly increased. This torque exceeds the strength limit of the screw, and the screw is broken. This is an accidental damage.

Screw repair

1 The broken screw should be made according to the actual inner diameter of the barrel, and the outer diameter deviation of the new screw.

2 After the surface of the wear screw is repaired, the wear-resistant alloy is sprayed at a high temperature (the wear-resistant alloy is composed of materials such as C, Cr, Vi, Co, W and B), and then the edge is trimmed. After polishing, it matches the barrel and the service life can reach 98% of the new or more.