Causes and solutions for broken teeth of ball mill pinion

1. Causes of fatigue fracture of ball mill pinion
（1）The main reasons for fatigue fracture of ball mill pinion are:
（2）The dynamic load of the transmission system is too large;
（3）The radius of the tooth root fillet is too small;
（4）The surface roughness value of the tooth root is too large;
（5）The tooth root is pulled during rolling;
（6）The material is defective, and heat treatment produces tiny cracks and other harmful residual stresses.
When the alternating stress at the root of the pinion of the ball mill exceeds the fatigue upper limit of the material, fatigue cracks will occur at the root fillet. The cracks will continue to expand after long-term operation, and eventually, the gear will bend and fatigue and break.

2. Overload fracture of ball mill pinion
The fracture of ball mill pinion due to overload is mainly due to the impact load of the ball mill being severely overloaded in a short period of time, which causes the gear to bear stress exceeding the upper limit stress.
When the load of the ball mill is severely concentrated, the dynamic load is too large, or a larger and harder foreign body enters the gear meshing, it will cause overload phenomenon and cause the pinion to break.
The fatigue fracture of the pinion of the ball mill is gradually caused by the long-term action of alternating stress. Since the pinion has a small number of teeth and a relatively large number of stress cycles, fatigue fracture is also possible.

However, the dynamic load of the ball mill transmission system is generally not very large. Moreover, before each replacement, the involute parameters, gear accuracy, and surface quality of the new gear are measured and inspected. The test results are in line with the technical requirements of the drawings. Judging from the time it took for the pinion of the modified wet ball mill to break after several replacements, it should be the combined effect of fatigue and overload.

 

3. Troubleshooting of broken pinion gears of ball mills

For the above-mentioned pinion gears of ball mills, corresponding adjustments can be made according to the technical requirements for the assembly of the main transmission gears of MQG wet ball mills:

1. Adjust the axial distance of the two gears according to the deviation range of the center distance of the gear pair to ensure the tooth top clearance and tooth side clearance between the two wheels. The tooth side clearance is measured by the lead pressing method;

2. Adjust the parallelism of the axes of the two gears so that the contact spot mark after the color inspection in the tooth width direction is centered;

3. Grind the tooth surface of the large gear damaged by broken teeth;

4. Change the splash lubrication of the tooth part to spray lubrication.