Damage Condition

Shaft end (mainly bearing journal) broke completely.

Possible Causes Rotational bending fatigue caused by misalignment of screw shaft (the bearing journal was forced to bend because of eccentricity between the ball screw thread and the bearing journal) Countermeasures Improve assembly accuracy of the ball screw Breakage of Shaft End

Part: Screw shaft
Symptom: Shaft end broke completely
Cause: Broken bearing journal due to rotating bending fatigue

Source: NSK