How can wear be reduced and the service life of the screw and barrel extended?

Injection molding screws operate under conditions of high temperature, high pressure, high mechanical torque, and intense friction. While the first few factors are dictated by processing requirements, wear caused by friction is inevitable. Screws typically undergo surface nitriding to increase surface hardness and, consequently, wear resistance. However, if the causes of wear are ignored and no measures are taken to minimize it, the screw's service life will inevitably be significantly reduced.

The following outlines the causes of screw wear and methods to minimize it:
1. Each type of plastic has an ideal processing temperature range for plasticization; the barrel temperature should be controlled to align with this range. When granular plastic enters the barrel from the hopper, it first reaches the feed section, where dry friction inevitably occurs. If the plastic is insufficiently heated or melts unevenly, it can easily lead to increased wear on the inner barrel wall and the screw surface. Similarly, in the compression and metering sections, inconsistent or uneven melting states can also accelerate wear.

2. Rotational speed must be properly adjusted. Some plastics contain reinforcing agents-such as glass fibers, minerals, or other fillers-that exert significantly higher friction on metal surfaces than the molten plastic itself. When molding these plastics at high speeds, the increased shear force not only processes the material but also causes more reinforcing fibers to fracture. These fractured fibers often have sharp ends, which drastically increase abrasive wear. Furthermore, inorganic minerals sliding at high speeds against metal surfaces exert a significant scraping effect. Therefore, the rotational speed should not be set too high.