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Common faults and solutions of extruder screw and barrel

Update:31-08-2020
Summary:

The combined working quality of the two parts of the ex […]

The combined working quality of the two parts of the extruder screw and barrel has an important impact on the plasticization of materials, the quality of products and the production efficiency. Their work quality is related to the manufacturing accuracy and assembly clearance of the two parts. When the two parts are severely worn and the output of the extruder decreases, the screw and barrel of the extruder should be repaired.
1. Reasons for damage to the extruder screw and barrel 1. The extruder screw rotates in the barrel, and the friction between the material and the two causes the working surface of the extruder screw and barrel to gradually wear out: extruder screw diameter Gradually shrink, the diameter of the inner hole of the barrel gradually increases. In this way, the matching diameter gap between the screw and barrel of the extruder increases a little as the two gradually wear. However, because the resistance of the head and the manifold in front of the barrel has not changed, this increases the leakage flow of the extruded material when it advances, that is, the amount of material flowing from the diameter gap to the feeding direction increases. As a result, the output of the extruder is reduced. This phenomenon increases the residence time of the material in the barrel and causes the material to decompose. In the case of polyethylene, the hydrogen chloride gas produced by decomposition strengthens the corrosion of the screw and barrel of the extruder. 2. If there are fillers such as calcium carbonate and glass fiber in the material, it can accelerate the abrasion of the extruder screw and barrel. 3. Because the material is not plasticized uniformly or metal foreign matter is mixed into the material, the torque of the screw of the extruder increases suddenly. This torque exceeds the strength limit of the screw of the extruder, causing the screw of the extruder to twist and break. This is an unconventional accident damage.


2. Repair of extruder screw 1. The twisted extruder screw should be considered according to the actual inner diameter of the barrel, and the outer diameter deviation of the new extruder screw should be given according to the normal gap with the barrel. 2. After the surface of the thread with the reduced diameter of the worn extruder is treated, it is thermally sprayed with a wear-resistant alloy, and then ground to size. This method is generally processed and repaired by a professional spraying factory, and the cost is relatively low. 3. Overlay welding of wear-resistant alloy on the threaded part of the screw of the worn extruder. According to the degree of wear of the extruder screw, surfacing welding 1"2mm thick, and then grinding the extruder screw to size. This wear-resistant alloy is composed of C, Cr, Vi, Co, W and B and other materials to increase extrusion The anti-wear and corrosion resistance of the screw of the machine. The cost of this kind of processing by professional surfacing factories is very high. Except for the special requirements of the extruder screw, it is generally rarely used. 4. Repairing the extruder screw can also be coated with hard surface In the chromium method, chromium is also a wear-resistant and corrosion-resistant metal, but the hard chromium layer is easier to fall off.

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