Plastic extruder screw damage causes and repair methods

The screw of the plastic extruder has an important influence on the plasticization of the material, the quality of the product and the production efficiency. When the screw wear is severe and the output of the plastic extruder is reduced, the maintenance of the screw should be arranged. Below, I will introduce the causes and repair methods of the screw damage of the plastic extruder.
First, the reason for the damage of the screw of the plastic extruder
1. The screw rotates in the barrel, and the friction between the material and the two causes 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 little with the gradual wear of the two. However, since the resistance of the front head and the splitter plate of the barrel is not changed, this increases the leakage flow when the extruded material advances, that is, the flow of material from the diameter gap to the feed direction increases, and the result is a plastic extruder. Production is declining. This phenomenon causes the residence time of the material in the barrel to increase, causing the material to decompose. If it is polyethylene, the hydrogen chloride gas generated by the decomposition enhances the corrosion of the screw and barrel of the plastic extruder.
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 of the plastic extruder screw.
3. Since the material is not plasticized evenly, or metal foreign matter is mixed into the material, the torque of the screw of the plastic extruder suddenly increases, and the torque exceeds the strength limit of the screw so that the screw is broken. This is unconventional accident damage.
Second, the repair method of the extruder screw
1. The broken screw should be considered according to the actual inner diameter of the barrel, and the outer diameter deviation of the new screw is given according to the normal gap of the barrel.
2. After the surface of the thread with the reduced diameter of the worn screw is treated, the wear-resistant alloy is thermally sprayed and then ground to a size. This method is generally processed and repaired by a professional spray factory, and the cost is still relatively low.
3. Surfacing the wear-resistant alloy on the threaded portion of the worn screw. Depending on the degree of wear of the screw, weld 1 to 2 mm thick and then grind the screw to size. The wear-resistant alloy is composed of materials such as C, Cr, Vi, Co, W, etc., which increases the anti-wear and corrosion resistance of the screw. Professional surfacing plants have a high cost for such processing and are rarely used except for special requirements.
4, repair plastic extruder screw can also be surface hard chrome plating method, chromium is also wear-resistant and corrosion-resistant metal, but the hard chrome layer is easier to fall off.