Ballscrew inspection, problems and warning signs associated with ball screw failure?
Excessive backlash in the ball screw ballnut- Some screws must be stretched before checking for backlash.
Fatigue or surface distress
Visually inspect for pitting or spalling which typically is from contaminants.
Heat discoloration on lead or balls of ball screw. This is often cause by poor lubrication or
Inspect wipers or seals to see if they are loose or missing and wiping the screw properly
Vibration when moving caused by bent ball screws, misalignment of bearing housings or possibly just an unlevel machine.
Loud clicking sound coming form ball nut tubes can also be a problem if there was excessive build up under way covers with chips and such causing tubes to be damaged, dented or bent.
Excessive servo load increase due to improper circulation of ballscrew nut balls.
For preloaded ball screw nuts- remove the nut from the table or turret and turn by hand. You should feel some resistance to turn approximately 6 pounds of rotation force. If not then screw may have lost its preload causing some backlash.
If machines have scales many times when the axis is jogged or in rapid you can feel a pulsing coming from the axis which may settle in after a foot or two. This is usually backlash either in the screw or bearings.
Look for brinelling-typically caused by a crash on the screw threads.
Look for ball bearing skid marks-typical this is caused by poor lubrication.
Excessive ball nut preload-can be cause by crashing nut into bearing housings or endstops.
Check all lube lines, fittings, connections for damage
Inspect lubrication tank for contaminants on bottom and inspect pump filters have been clean.
*Note: Use a magnifying glass for a much better view of whats going on with your ball screw
