Ball Screw RCA: Flaking

 

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