Kellenberger Kel-Vision URS 125 Spindle Failure
Our customer indicated that this OD grinding spindle would load up in operation and eventually lock up. When we disassembled and evaluated the spindle and the other components on the wheelhead, we saw that the spindle shaft had rubbed out on the bronze oil bearings. It was apparent that a number of factors contributed to the failure of the hydrodynamic film between these components. The oil pump was partially seized, some oil supply fittings & fixtures were compromised and the oil bearing main housing was missing the o-rings. Additionally, the coolant passages for the OD spindle, drive motor & casting were plugged with grinding swarf. The OD drive motor bearings were also worn and the motor shaft shoulders had excessive runout. The ID grinding spindle was not supplied with the wheelhead, so we did not address the ID drive motor and belt tension pulley which were also seized.
Our rebuild started with a grind, chrome plate & finish grind of the OD spindle shaft journals and a kiss grind of the bronze bearings to remove the rubout damage. We also kiss ground the wheel hub taper to clean it up while the spindle shaft was up on the grinder. The shoulders of the OD motor shaft were also kissed to improve the runout, and we repaired the oil pump. After a thorough cleaning of all components, we reassembled the OD spindle & motor using new radial bearings (for the motor), drive belts, seals, o-rings, and various oil supply, vent & assembly components. We pressure tested the front & rear housings, filled the reassembled spindle with fresh oil and test ran the spindle for several hours while performing additional pressure testing. When were satisfied that the spindle was functioning properly, we drained the spindle oil for shipping, crated it and now it is back in the machine, making money for our customer.