Summary of the causes of damage to screws and barrels in extrusion molds

The combined working quality of the screw and barrel in the extrusion mold has a significant impact on the plasticization of materials, the quality of products, and production efficiency. Their working quality is related to the manufacturing accuracy and assembly clearance of the two parts. When two parts are severely worn and the output of the extruder decreases, maintenance of the screw and barrel should be arranged.

1、 Reasons for damage to screws and barrels

1. The screw rotates inside the barrel, and the friction between the material and the two gradually wears down the working surface of the screw and barrel: the diameter of the screw gradually decreases, and the diameter of the inner hole of the barrel gradually increases. In this way, the clearance between the screw and the barrel gradually increases as they wear out. However, due to the unchanged resistance of the machine head and splitter plate in front of the barrel, this increases the leakage flow of the extruded material as it advances, that is, the flow of material from the diameter gap towards the feeding direction increases. As a result, the production volume of the extruder decreased. This phenomenon also increases the residence time of materials in the barrel, causing material decomposition. If it is polyethylene, the hydrogen chloride gas produced by decomposition enhances the corrosion of screws and barrels.

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. Due to uneven plasticization of the material or the presence of metal foreign objects mixed into the material, the torque force of the screw suddenly increases, exceeding the strength limit of the screw and causing it to break. This is an unconventional accident damage.