1. Fast wear rate Due to the influence of factors such as the processing, assembly and adjustment of new machine parts, the friction surface is rough, the contact area of the mating surface is small, and the surface pressure is uneven. During the operation of the machine, the uneven parts on the surface of the parts engage and rub against each other, and the metal scraps that fall off are used as abrasives to continue to participate in the friction and accelerate the wear of the mating surface of the parts. Therefore, during the running-in period, it is easy to cause wear of the parts (especially the mating surface), and the wear rate is fast. At this time, if overloading is performed, it may cause damage to parts and cause early failure.

2. Poor lubrication. Due to the small fit clearance of newly assembled parts, and due to assembly and other reasons, it is difficult to ensure the uniformity of the fit clearance. Lubricating oil (grease) is not easy to form a uniform oil film on the friction surface to prevent wear. Thereby reducing the lubrication efficiency, causing early abnormal wear of the machine parts. In severe cases, it will cause scratches or seizures on the friction surface of the precision fit, leading to failures.

3. The newly processed and assembled parts that are loosened have deviations in geometric shapes and matching dimensions. In the early stage of use, they are affected by alternating loads such as shock and vibration, as well as heat, deformation and other factors, plus excessive wear and other reasons. It is easy to loosen the originally fastened parts.

4. Leakage occurs due to the loosening of the machine parts, vibration and the influence of the machine’s heating, the sealing surface of the machine and the pipe joints, etc., there will be leakage; some defects such as casting and processing are difficult to find during assembly and debugging, but due to work In the process of vibration and impact, this kind of defect is exposed, which is manifested as oil (water) leakage (seepage). Therefore, leakage is prone to occur during the running-in period.