Catastrophic bearing failure was the main cause of this spindle malfunction Continue reading to learn how Northland Tool performed this repair and converted a Weiss GHK 176239 spindle from grease-injected to permanent grease lubrication……Read More
Cincinnati Sabre 1000 Spindle Repair
The Cincinnati Sabre 1000 is a CNC vertical machining center. It comes equipped with a grease lubricated and belt driven spindle capable of running up to 8,000 rpm.
Upon disassembling this Cincinnati Sabre 1000 we found that the front and rear bearings failed from contamination that caused lack of preload to the bearings. Because of the lack of preload the inner bearing spacer spun on the shaft causing damage. We then inspected the critical dimensions (bearing journals, bearings shoulders, housing, taper, etc.) and found a few unacceptable deviations. First the rear shaft journal had 8-10 microns of runout and has a rubout band caused by the inner spacer. Second the front shaft journal had rubout damage caused by the inner spacer as well. Lastly the shaft taper had 40-60 microns of runout, slightly bell mouthed, and the taper gauge sat below the gauge line. We also noted that where the bellevilles ride on the shaft tail, the drive dogs, and the drive pulley teeth were severely worn.
The following actions were performed on this Cincinnati Sabre 1000 spindle:
- Clean, inspect overall dimensions.
- Grind, chrome plate and finish grind (GPG) the front and rear shaft journals.
- GPG the CT 40 taper.
- GPG the shaft tail
- Manufacture a new inner bearing spacer.
- Replace bearings, gripper balls, bellevilles, lock washer, seals, orings, drive dog and drive pulley.
After reassembly of all components, adjusting bearing preload, and undergoing break-in and testing procedures, this spindle passed our final quality inspection before being returned to our customer with a 1-year warranty.
DETAILED CAUSE OF FAILURE
This is the inside of the front cover. Notice the contamination throughout the cover porting.
Picture of the contamination present in the angular contact bearings
Damage to the shaft from the inner spacers spinning on the shaft.
The new pulley being balance on our Schenck balancing equipment. This equipment lets us component balance the rotating parts of the spindle before the spindle is assembled. This step enables us to make very small adjustments during the final trim balance of the spindle. Other rebuilders often skip this step to save time which means they remove large amounts of material on the final test run. When that is done they sometimes are not removing the material exactly were it is needed as they can no longer access the area so they need to compensate with larger removal of material.
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