Focus on extrusion, granulation screw barrels design and manufacturing
What can be done to minimize the wear of the bimetallic screw
2022.06.06
The Bimetallic screw barrel 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 improve the surface hardness, that is, to improve the wear resistance.
However, if the cause of wear is ignored and the wear is not minimized, the working life of the screw will be greatly reduced. Each plastic raw material has an ideal plasticizing temperature range, so the barrel processing temperature should be controlled to make it close to this temperature range. When the granular plastic enters the barrel from the hopper, it will first reach the feeding section, and dry friction will inevitably occur in the feeding section. When these plastics are insufficiently heated and melted unevenly, 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 the homogenization section, if the molten state of the plastic is disordered and uneven, it will also cause increased wear. The speed should be adjusted properly. Because some plastics are added with reinforcing agents, such as glass fibers, minerals or other fillers. These substances tend to be much more abrasive to metal than molten plastic.
When injection molding these plastics, if the high rotational speed is used, the shear force on the plastic will be increased, and at the same time, the reinforcement will also produce more shredded fibers. The shredded fibers contain sharp ends and cause wear and tear. Power is greatly increased. When inorganic minerals slide at high speed on the metal surface, their scraping effect is not small. Therefore, the speed should not be adjusted too high.
However, if the cause of wear is ignored and the wear is not minimized, the working life of the screw will be greatly reduced. Each plastic raw material has an ideal plasticizing temperature range, so the barrel processing temperature should be controlled to make it close to this temperature range. When the granular plastic enters the barrel from the hopper, it will first reach the feeding section, and dry friction will inevitably occur in the feeding section. When these plastics are insufficiently heated and melted unevenly, 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 the homogenization section, if the molten state of the plastic is disordered and uneven, it will also cause increased wear. The speed should be adjusted properly. Because some plastics are added with reinforcing agents, such as glass fibers, minerals or other fillers. These substances tend to be much more abrasive to metal than molten plastic.
When injection molding these plastics, if the high rotational speed is used, the shear force on the plastic will be increased, and at the same time, the reinforcement will also produce more shredded fibers. The shredded fibers contain sharp ends and cause wear and tear. Power is greatly increased. When inorganic minerals slide at high speed on the metal surface, their scraping effect is not small. Therefore, the speed should not be adjusted too high.
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