There are many factors that could lead to premature failure of a ball screw or ball nut. Several of the most common are listed below:
- Lack of lubrication. Proper lubrication will help dissipate heat and reduce metal-to-metal wear of components. Insufficient lubrication is one of the primary reasons for premature ball screw or ball nut failure.
- Dirt or debris in the ball nut or ball paths preventing free circulation of the ball bearings. The ball bearings may get flats on them due to skidding and spalling, which may in turn damage the ball paths in the screw or the ball nut.
- Misalignment of the ball nut to screw which results in side loading or eccentric loading. It is very important that the ball nut only experiences axial loading. Side loading or eccentric loading may cause the ball bearings to wear flat in places. The bearings may even break out of the return tubes.
- Excessive speed. Exceeding the ball nut critical speed can lead to pickup fingers breaking, which will allow to the ball bearings to come out of the nut. Exceeding the screw critical speed will cause the screw to whip or vibrate and cause misalignment. Shaft speeds resulting in screw surface speeds above 8,000 inches per minute will reduce rated life.
