Improper assembly
The motor is not concentric with the driven equipment, which causes the motor to bear excessive radial load, and finally leads to metal fatigue. When the radial load on the extension end of the motor shaft is too large, the motor shaft will be bent and deformed in the radial direction. When the motor rotates, the shaft deforms due to torsion in all directions, which eventually causes the motor shaft to break, and the fracture position is generally close to the bearing. For the motor connected by pulley, but some customers match the pulley to the output shaft of the motor, because the pulley is too heavy or the belt is installed too tight, the output shaft of the motor will continue to be subject to variable stress during the operation of the motor. The maximum bending moment of this stress on the shaft is near the bearing fulcrum of the output shaft. Repeated impact will cause fatigue, and the shaft will gradually crack, and finally it is finished Total fracture.

Excessive vibration of equipment and motor in operation
If the motor is not fixed firmly, such as running on the rack, the whole foundation is unstable and shakes during the operation, resulting in unstable tension of the motor belt, and shaft damage when the tension is large.

After welding, the stress of the web axis is not released
This problem often occurs in the case of large-scale motor plate shaft. The location of the problem is mostly concentrated in the combination of the plate end and the main shaft. The fracture pattern of the shaft is irregular. Moreover, most of the motor faults in the early stage are bore sweeping, which can only be found in the later stage of inspection. For the plate shaft, the motor manufacturer should take the stress relief measures, some manufacturers adopt the ultrasonic method, some manufacturers adopt the annealing process, but the ultimate purpose is to eliminate the stress.

The load moment is too large; the small horse pulls the cart and the motor shaft is in the fatigue state for a long time; the external force collision can also cause the shaft breaking, which is a relatively complex problem. Both the motor manufacturer and the user must pay attention to this problem to avoid similar problems.