Screw molding machine for a long time in high temperature, high pressure, high mechanical torque and high friction environment to work, the first few factors are required for process conditions, while the friction caused by the loss is inevitable.
General screw surface nitriding treatment to improve the surface hardness, that is, to improve the anti-wear capacity.But if you ignore the cause of wear and tear, try not to minimize wear and tear, will inevitably greatly reduce the working life of the screw.
The following will focus on the cause of the screw wear and reduce wear and tear methods:
Each plastic has an ideal plasticizing process temperature range, and the barrel temperature should be controlled to approximate this temperature range. Pellets enter the barrel from the hopper, first reaching the loading section, and inevitably dry in the loading section Friction, when these plastics lack of heating, uneven melting, it is easy to cause the cylinder wall and the screw surface increased wear and tear.
Similarly, in the compression section and the homogenization section, if the molten state of the plastic is not uniform, the abrasion may also be increased.
Speed should be properly adjusted due to some of the plastics with toughening agents, such as fiberglass, minerals or other fillers These materials tend to be more abrasive metal materials than the melting of plastics in the plastic injection of these plastics, if the use of High speed into, then increase the shear on the plastic at the same time, will also make fortification accordingly produce more torn fibers, torn fibers contain sharp ends, so that greatly increased wear resistance.
Inorganic mineral skidding on the metal surface, the scraping effect is not small, so the speed should not be adjusted too high.
In general, the original purchase of fresh plastic and no debris, but after transport, weighing, drying, mixed colors, especially the addition of recycled back to the expected, there may be mixed with debris .
Small, such as the end of the metal shavings, as large as the heating ring nut paper clip, or even a string of warehouse keys, have been mixed into the barrel have occurred, which is self-destructive screw damage (and of course the barrel will also damage ), It must be installed magnet holder, rigorous feeding management and monitoring.
The moisture contained in the plastic, the wear and tear of the screw surface has a certain impact.If the plastic in the injection did not exclude all the water before the residual moisture into the screw compression section, they formed before the melt mixed with molten plastic with high temperature pressure ' Steam particles'. With the progress of the injection screw, the 'steam particles' from the homogenization section up to the head of the screw decompress and expand in the course of the shot, like fine particles of fine impurities, which are generated on the wall surface Rubbing damage.
In addition, some types of plastic, under high temperature and pressure, the water may become a catalyst to promote the cracking of plastics, can produce harmful impurities that can erode the metal surface.Therefore, the plastic drying work before injection, not only the quality of the workpiece Direct relationship, but also affect the working life of the screw.