Teach you how to reduce weartearimprove the use of screw cartridge.
2018-09-12 10:04:20
The injection screw works under high temperature, high pressure, high mechanical torque and high friction environment for a long time. The first few factors are required by technological conditions, and the attrition caused by friction is inevitable. The general screw has been treated by surface nitriding to improve the surface hardness, that is to say, improve the wear resistance. But if the cause of wear is neglected and the wear is not reduced as far as possible, the working life of the screw will be greatly reduced.
First, cause the wear of screw barrel.
1. Every kind of plastic has an ideal plastic processing temperature range, should control the barrel processing temperature, make it close to this temperature range. Granular plastics from the hopper into the barrel, the first will reach the feeding section, in the feeding section will inevitably arise dry friction, when these plastics are not heated enough, uneven melting, it is easy to cause the inner wall of the barrel and screw surface wear and increase. Similarly, in the compression section and homogenization section, if the melting state of plastics is not uniform, it will also cause wear increase.
2, the speed should be adjusted properly. Some plastics are reinforced with fortifier, such as glass fiber, mineral or other filler. The friction force of these materials on metal materials is often much larger than that of molten plastics. In the injection molding of these plastics, if the high-speed conversion, while increasing the shear force on the plastics, will also make the strengthening correspondingly produce more torn fibers, the torn fibers contain sharp ends, so that wear force greatly increased. When inorganic minerals move on metal surface at high speed, their scraping effect is not small. So the speed should not be adjusted too high.
3. The screw rotates in the barrel, and the friction between the material and the barrel causes the working surface of the screw and the barrel to wear out gradually: the diameter of the screw is gradually reduced, and the diameter of the inner hole of the barrel is gradually enlarged. In this way, the diameter gap between the screw and the barrel will be increased with the gradual wear and tear of the two. However, as the resistance of the head in front of the barrel and the distributor has not changed, this increases the leakage flow of the extruded material forward, that is, the flow of the material from the diameter gap to the feed direction increases. As a result, the production of plastic machinery decreased. This phenomenon also increases the residence time of materials in the cylinder, resulting in the decomposition of materials. If it is polyethylene, decomposition of hydrogen chloride gas to strengthen the screw and barrel corrosion.
4, materials such as calcium carbonate and glass fiber filler can speed up the wear of screw and barrel.
5. Because the material is not plasticized uniformly, or there are metal foreign bodies mixed into the material, so that the screw rotating torque suddenly increases, this torque exceeds the strength limit of the screw, so that the screw is broken. This is a kind of unconventional accident damage.
Two, reduce wear method - pay attention to the daily maintenance of screw barrel.
1, do not start the machine when the screw is not up to the preset temperature.
2. Prevent metal fragments and sundries from falling into the hopper. If recycled materials are processed, magnetic hopper should be added to prevent iron fragments from entering the hopper.
3. Make sure that the plastic in the barrel is completely melted when using saliva prevention, so as to avoid damaging the transmission system parts when the screw retreats.
4, when using new plastic, the remaining material of the barrel should be cleaned.
5. When the temperature of melted plastic is normal but the melted plastic is found black spots or discoloration, the screw should be checked.
6. In the process, try to make the material plasticized evenly, do not let metal foreign bodies into the material, reduce the screw rotation torque.
