Focus on extrusion, granulation screw barrels design and manufacturing
How to reduce the wear of the screw barrel
2021.11.26
The screw of the injection molding machine works under high pressure, high temperature, high mechanical torque and high friction environment for a long time. The first few factors are required by the process conditions, but the loss caused by friction is inevitable. Generally, the screw has undergone surface nitriding treatment to increase the surface hardness, that is, to improve the wear resistance. However, if the causes of wear are ignored and the wear is not reduced as much as possible, the working life of the screw will inevitably be greatly reduced.
The following 2 points introduce the causes of screw wear and methods to reduce wear
1. Each plastic raw material has an ideal plasticizing processing temperature range, so the processing temperature of the barrel should be controlled to make it close to this temperature range. When granular plastic enters the barrel from the hopper, it will first reach 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 cause increased wear on the inner wall of the barrel and the surface of the screw; In the compression section and the homogenization section, if the molten state of the plastic is disordered and uneven, it will also cause increased wear.
2. The speed should be adjusted properly. Because some plastics are added with strengthening agents, such as glass fibers, minerals or other fillers. The friction of these substances on metal materials is often much greater than that of molten plastics. When injecting these plastics, if a high speed is used, while increasing the shearing force to the plastic, it will also cause the reinforcement to produce more shredded fibers. The shredded fibers contain sharp ends, which will cause wear. The strength is greatly increased. When inorganic minerals slide on the metal surface at high speed, their scraping effect is not small. Therefore, the speed should not be adjusted too high.
The following 2 points introduce the causes of screw wear and methods to reduce wear
1. Each plastic raw material has an ideal plasticizing processing temperature range, so the processing temperature of the barrel should be controlled to make it close to this temperature range. When granular plastic enters the barrel from the hopper, it will first reach 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 cause increased wear on the inner wall of the barrel and the surface of the screw; In the compression section and the homogenization section, if the molten state of the plastic is disordered and uneven, it will also cause increased wear.
2. The speed should be adjusted properly. Because some plastics are added with strengthening agents, such as glass fibers, minerals or other fillers. The friction of these substances on metal materials is often much greater than that of molten plastics. When injecting these plastics, if a high speed is used, while increasing the shearing force to the plastic, it will also cause the reinforcement to produce more shredded fibers. The shredded fibers contain sharp ends, which will cause wear. The strength is greatly increased. When inorganic minerals slide on the metal surface at high speed, their scraping effect is not small. Therefore, the speed should not be adjusted too high.
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