Most of the wear of the conical twin barrel screw occurs in the high pressure region, especially in the transition section and the last few turns of the metering section. These areas are prone to wear because the high pressure can cause the conical twin barrel screw to bend, causing the outer diameter of the flight to come into contact with the metal on the inner barrel wall, causing wear. The force that causes the conical twin barrel screw to bend is a pressure difference, not the usual high pressure. However, the contact of the outer diameter of the flight with the inner wall of the barrel does occur, but this is caused by mechanical conditions and portends potentially more serious problems: such as misalignment problems, gearbox damage, screw bending, machine Tube bending and insufficient foundation, etc. According to wear tests in many industries, the increase in pressure and temperature can lead to increased friction of the conical twin barrel screw.
Conical twin-barrel screw wear is usually a slow process and less noticeable until there is a noticeable decrease in performance. Minor wear has little effect on overall performance as productivity can be maintained by adjusting machine parameters. Leakage is inevitable when the radial clearance between the flight of the conical twin-barrel screw and the barrel wall increases. Operators typically observe reduced output and increased melt temperature, while also having to increase the conical twin-barrel screw speed to maintain the desired output, often accompanied by more energy. consumption. As the radial clearance increases, the conical twin barrel screw cannot generate the necessary pumping pressure to maintain the desired output.
During the repair process, the conical twin-barrel screw is ground to a uniform undercut diameter, and then the flight is re-welded to apply a higher hardness hardfacing alloy to its surface, which provides better wear resistance. After surfacing, the outer diameter of the conical twin barrel screw must also be ground to the original tolerance. The remaining overhang welds must be profile ground to ensure the smallest possible loss of flight width. During this process, some poor operations will reduce the effective flight width, which may have a potential impact on the performance of the twin-barrel screw and complicate the possibility of future repair of the twin-barrel screw. To help alleviate these complications, some screw manufacturers choose to reduce the width of the weld. However, with this practice, when these twin-barrel screws are ground to original tolerances, the hardfacing material does not cover the entire flight width, which can negatively impact the wear resistance of twin-barrel screws, Because there will be a softer substrate exposed.