Ball mill is an important grinding equipment in cement, metallurgy, mining, power plants and other industries. The gear transmission is an important part of it. Its weight, volume and cost account for a large proportion of the whole machine. Its working efficiency has an important impact on the normal operation of the ball mill. However, during the working process of the mill, gear transmission failure is a common fault. This article mainly analyzes the reasons for gear transmission failure.
The failure modes of gears are as follows: excessive wear, abrasive wear, pitting corrosion and gear tooth breakage. The causes of gear transmission failure are as follows:
1) Working environment and lubrication conditions
Due to limited working conditions, the working environment of the ball mill gear pair transmission is relatively poor, with more dust particles in the air and poor sealing conditions. In terms of lubrication, manual regular refueling is used, so the gear pair is prone to the following problems: insufficient oil injection, poor sealing condition of the gear pair, and the metal surface is susceptible to excessive wear caused by dry friction.
2) coincidence degree
In transmission, the time for a single tooth of the gear pair to bear the load is greatly extended, which is an important reason for rapid gear wear. The reduction in coincidence will inevitably cause the gear backlash to increase, making it easier for some impurities, floating objects and dust in the air to enter between the meshing surfaces of the gear pair, causing abrasive wear.
3) Tooth surface contact fatigue strength
Stress concentrations exist in the gear. When a tooth tip enters mesh, excessive equivalent contact shear stress forms initial cracks in the surface layer. During gear operation, high-pressure oil waves generated by contact pressure enter these cracks at extremely high speed, exerting a powerful hydraulic impact on the crack walls. At the same time, the mating gear surface can seal the crack opening, further increasing oil pressure inside the crack and forcing it to propagate both deeper into the material and toward the tooth surface. Material then detaches from the tooth surface, forming pits.
4) Tooth root bending fatigue strength
After the gear has been running for a period of time, the axis of the pinion and the axis of the ball mill drum may become non-parallel. At this time, the gear mesh becomes a local contact, and the gear is unevenly stressed across the entire tooth width. The gear shaft is prone to bending and torsional deformation, which causes the load to be unevenly distributed along the tooth width. On the other hand, due to the uneven material structure, there are slag inclusions, pores and hard particles, etc., the local shear stress of the surface or subsurface layer is too large, resulting in tooth breakage.
(Source: Internet)