TL;DR
Spindle bearing noise or vibration causes surface finish degradation on aerospace parts. Monitor spindle vibration trend data and plan an inspection if vibration exceeds the alarm threshold.
What you might see
- audible whine or growl at specific spindle speeds
- surface finish Ra increasing on finished passes
- spindle vibration sensor reading above the alarm level
- spindle warm-up time increasing
Likely causes
Spindle bearing wear from accumulated running hours
Contamination of spindle bearing lubrication from coolant ingress
Thermal overload of spindle bearings from exceeding rated duty cycle
Spindle runout increasing from bearing wear affecting part quality
Required tools
- Dial indicator for runout check
- Vibration monitoring data from the DMG Mori control
Safety first
- Do not attempt spindle bearing replacement in the field. Spindle cartridge replacement requires OEM-trained service technicians and precision assembly equipment.
- Coolant ingress into the spindle bearing cavity is often caused by worn spindle seal. Address the seal before replacing bearings to prevent repeat failure.
Procedure
- 1
Access the spindle condition monitoring data on the DMG Mori control panel. Note the current vibration level and trend over the last 30 days.[1]
- 2
Run the spindle warm-up program and monitor vibration at incremental speeds. Note any speed range where vibration spikes.
- 3
Measure the spindle runout at the tool taper with a dial indicator. Record the reading.[1]
- 4
Check the spindle bearing lubrication system. Confirm the lubrication pump is cycling and the oil mist or grease is reaching the spindle bearings.
- 5
If vibration is trending upward but below the alarm threshold, increase the frequency of spindle condition checks and notify DMG Mori service to plan a spindle inspection.
- 6
If vibration has exceeded the alarm threshold or runout is above specification, stop production on that spindle and contact DMG Mori service for spindle removal and bearing replacement.
- 7
Do not continue aerospace production with a degraded spindle. Surface finish and dimensional accuracy requirements cannot be met with worn spindle bearings.
Sources
DMG Mori DMG Mori DMU / DMC 5-Axis CNC Machining Center general technical documentation, DMG Mori
DMG Mori DMU / DMC machining center maintenance documentation, spindle condition monitoring and bearing inspection procedures (general)
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