Damage Condition
The raceways of the screw shaft and ball nut and/or the surface of the ball peel off like scales because of fatigue.
Possible Causes
- Natural life of the ball screw
- Improper assembly (misalignment)
- Insufficient lubrication or inadequate lubricant
- Developed from indentations or corrosion pits
- Intrusion of contamination and/or water
Countermeasures
- If the rolling fatigue life is shorter than expected, review the size of the ball screw
- Improve assembly accuracy
- Improve the way of lubrication
- Select an adequate lubricant
- Avoid impact load to the ball screw
- Improve sealing capability of the ball screw
Flaking 1
Part: Screw shaft
Symptom: The surface of the ball peels off like scales
Cause: Excessive offset load to a ball nut initiated by misaligned ball screw shaft
Flaking 2
Part: Ball nut
Symptom: The surface of the ball peels off like scales
Cause: Excessive offset load to a ball nut initiated by misaligned ball screw shaft
Source: NSK