Why does the barrel screw of a single screw extruder wear out?

Update: 2020/12/14
Summary:

As a common extruder equipment, single screw barrel is […]

As a common extruder equipment, single screw barrel is used in plastic processing industry, such as film blowing, pressing plate, extruding pipe, drawing ribbon, etc. It can also be used for melt granulation. Many people will experience wear and tear of the barrel and screw during use. What is causing this?
  The matching diameter gap between the single screw extruder and the barrel increases little by little with the gradual wear of the two. However, because the resistance of the head and the manifold in front of the barrel has not changed, this increases the leakage flow when the extruded material advances, that is, the amount of material flowing from the diameter gap to the feeding direction increases. As a result, the output of plastic machinery decreased. This phenomenon increases the residence time of the material in the barrel and causes the material to decompose. To
   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 they are made with a high rotation speed, it will increase the shearing force to the plastic, and at the same time, the reinforcement will produce more shredded fibers. The shredded fibers contain sharp ends, causing wear Power is greatly increased. Granular plastic enters the barrel from the hopper and first reaches the feeding section. Dry friction will inevitably occur in the feeding section. When these plastics are not heated enough and melted unevenly, it is easy to increase the abrasion of 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 and uneven, it will also cause faster wear.

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