What is the cause of screw wear? (2)


1. The speed should be adjusted properly. Because some […]

1. The speed should be adjusted properly. Because some plastics are added with reinforcing agents, such as fiberglass, minerals or other fillers. The friction of these substances on metal materials is often much greater than that of molten plastics. In the injection of these plastics, if the high speed is used, the shear force on the plastic will be increased, and the reinforcement will produce correspondingly more shredded fibers. The shredded fibers contain sharp ends, which cause wear The force is greatly increased. When inorganic minerals glide on the metal surface at high speed, its scraping effect is not small. Therefore, the speed should not be adjusted too high.
2. 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 out: 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 a little 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 production volume of plastic machinery declined. 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.