Why does the barrel screw of single screw extruder wear out?Why does the barrel screw of single screw extruder wear out?
As a common extruder equipment, single screw extruder is used in plastic processing industry, such as blown film, platen, extruded tube, ribbon pulling, etc. It can also be used for melt granulation. Many people will encounter the wear of the barrel screw during use. What causes this?
The diameter gap between the single screw extruder and the barrel increases slightly 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.
Because some plastics are added with reinforcing agents, such as glass fiber, minerals or other fillers. The friction of these substances on metal materials is often much greater than that of molten plastics. When injection molding 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. The granular plastic enters the feeding barrel from the hopper, and will first reach the feeding section. Dry friction will inevitably occur in the feeding section. When these plastics are insufficiently heated and unevenly melted, it is easy to cause increased wear on the inner wall of the barrel and the surface of the screw. Similarly, in the compression section and homogenization section, if the molten state of the plastic is disordered, it will also cause faster wear.