1.Hollow shaft is a relatively important part of the ball mill, so it has high requirements for manufacturing quality. However, because the shape of the structure is special, it is still in the R zone, so when the finishing process is performed, the casting defects must not occur. such as segregation and  shrinkage cavity, slag inclusion , and small cracks and so on, which are the cause of the breakage of the hollow shaft.

2.The hollow shaft is a relatively large steel casting, and some even reach a weight of more than ten tons. The inner part of the casting needs stress concentration. When processing the hollow shaft, the workblank is treated by aging. Some manufacturers will not care about the quality requirements in order to reduce the occupation of liquidity. They will be processed according to aging, resulting in the existence of stress concentration inside the hollow shaft .Under the action of alternating stress, it will also generate stress concentrated explosion during use, which is also the cause of cracks in castings.

3.When the manufacturer is in production, it will be subject to casting conditions or technical constraints. The hollow shaft workblank cannot be integrally cast, and it needs to be processed in stages, and then welded. If the quality of the weld or the quality of the heat treatment is not high, it will also cause the casting to break.

4.The hollow shaft will be used in the cement plant. When some manufacturers replace the ball mill end cover, the operator will use the bolt head of the gas cutting guard to save time or save trouble, and then vigorously hit the screw, which will also cause the hollow shaft is locally heated, so that the temperature is increased, which will cause the surface of the situation to sag and cause vibration, which will also cause internal stress concentration explosion, which leads to the fracture of the hollow shaft.