Screw wear reasons and maintenance precautions

Release Time:2023-12-15 13:50


Causes of wear:

Each plastic has an ideal plasticizing temperature range, and the processing temperature of the barrel should be controlled to make it close to this temperature range. Granular plastic from the hopper into the barrel, will first reach the feeding section, in the feeding section will inevitably appear in the friction, when the plastic heating is insufficient, uneven melting, it is easy to cause the barrel inner wall and screw surface wear increases. Similarly, in the compression section and the homogenization section, if the melting state of the plastic is uneven, it will also cause faster wear.

2, the speed should be adjusted properly. As part of the plastic with a reinforcing agent, such as glass fiber, minerals or its. He fills. The friction force of these substances on metal materials is often much greater than that of molten plastic. In the injection molding of these plastics, if the use of high speed into, while increasing the shear force on the plastic, will also make the reinforcement correspondingly produce more shredded fibers, shredded fibers contain sharp ends, so that the wear force is greatly increased. When inorganic minerals slide at high speed on the metal surface, its scraping effect is not small. Therefore, the speed should not be adjusted too high.

3. The screw rotates in the barrel, and the friction between the material and the two makes the working surface of the screw and the barrel gradually. Wear: the diameter of the screw is gradually reduced, and the diameter of the inner hole of the barrel is gradually increased. In this way, the screw and barrel fit. The diameter gap increases a little as the two gradually wear. However, since the resistance of the front head and the splitter plate of the barrel has not changed, this increases the leakage flow when the extruded material advances, that is, the flow of material from the diameter gap to the feed direction increases. As a result, the production of plastic machinery decreased. This phenomenon in turn makes the material in the machine. The residence time in the barrel increases, causing material decomposition. In the case of polyvinyl chloride, the hydrogen chloride gas produced by the decomposition strengthens the corrosion of the screw and the barrel..

4. If there are calcium carbonate and glass fiber fillers in the material, it can accelerate the wear of the screw and barrel.

5, because the material is not plasticized evenly, or metal foreign matter mixed into the material, so that the screw rotation torque force suddenly increased, this torque exceeds the strength limit of the screw, so that the screw twist off. This is an unconventional accident damage.

 Maintenance Notes:

1. Do not start the machine when the screw does not reach the pre-adjusted temperature.

2. Prevent metal fragments and sundries from falling into the hopper. If the recycled materials are processed, a magnetic hopper shall be added to prevent iron filings from entering the barrel.

3. When using anti-salivation, make sure that the plastic in the material is completely melted to avoid damaging the transmission system parts when the screw retreats.

When using new plastic, the remaining material of the screw should be cleaned.

5. When the temperature of the molten plastic is normal but the molten plastic is constantly found to have black spots or discoloration, the glue screw should be checked.

6. When processing, try to make the material plasticized evenly, do not let metal foreign matter mixed into the material, reduce the screw. Turning torque force.