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
Miyano BNC-34C Spindle Repair
The Miyano BNC-34C is a CNC turning center. It comes equipped with a grease lubricated and belt driven spindle capable of running up to 5,000 rpm.
Our customer’s lathe spindle arrived covered in dried coolant residue. Coolant contamination had completely washed out the grease from the front pair of angular contact bearings and the rear roller bearing. At some point the rear bearing cage had disintegrated, spilling the rolling elements into the spindle housing and distributing a fine black powder throughout the spindle interior. Needless to say, the front pair fared no better. Now provided with freedom of radial & axial movement, the spindle shaft rubbed out on the front labyrinth. We also noted severe wear on the timing pulley, in the tooling pilot, and on the shaft face. Although there was light fretting on the shaft from the bearings once the lubrication had disappeared, there were no significant dimensional deviations found on the shaft journals or in the housing bores.
We first performed a kiss grind on the shaft face to alleviate the excess runout, and we machined out the rubout damage to the front labyrinth. We replaced the bearings, o-rings and assembly hardware. Our customer declined our recommendations to replace the timing pulley and to grind, chrome plate, and finish grind the shaft tooling pilot.
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 (within 3 days!!!!) with a 1-year warranty.
DETAILED CAUSE OF FAILURE
These are the angular contact bearings that carry the axial loads applied to the spindle. As you can see the ball cages have been compromised and the bearings have deteriorated. This resulted in axial movement of the spindle shaft.
These are the rolling elements of the rear roller bearing as they were found upon disassembly. This is the reason the spindle no longer rotated.
This is a good representation of a bearing fretting the spindle shaft. The darkened areas are where the bearings inner race was seated. What you see is the oxidation of the material that has been removed from the shaft.
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