Haas UMC-750SS Spindle Repair

The Haas UMC-750SS is the Super Speed version of the UMC-750.  This spindle is grease lubricated, coupling driven, and capable of running up to 15,000 rpm vs the 10,000 rpm for the regular UMC-750.

CHALLENGE

This Haas UMC-750SS spindle passed all incoming checks after it arrived, so we test ran it. At around 8,000 rpm, the spindle became very hot and the bearings showed high acceleration which led to a full breakdown and evaluation.  After a closer inspection, we noted that there was some rubbing damage on the OD of the rear spacer. It appears to have made contact with the rear cover while in operation. There was a good amount of a dark sludge found on the inside of the rear cover and also in the rear bearing.  A yellowish oil was also found on the inside of the front cover mixed with grease from the front bearings.  It appears that the grease was washed out by coolant flooding and contaminated the interior of the spindle. Very little grease remained in the bearings and the same yellow oil was found on the inside of the housing as well as around the front bearings.  No dimensional deviations were noted for this repair.

SOLUTION

The following actions were performed on this Haas UMC-750SS spindle:

• Clean, inspect overall dimensions
• Replace bearings, o-rings, and assembly screws
• Replaced gripper balls and bellevilles

RESULT

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.