Hardinge Bridgeport VMC 1250 Front bearings killed by coolant



CHALLENGE

Hardinge Bridgeport VMC 1250, 6,000 RPM, grease lubrication, belt driven

Front bearings killed by coolant, tooling taper wear, missing parts

Our customer indicated that this spindle had been noisy when operated at higher speeds, and eventually had seized up. They also let us know that the drive dogs, sensor orientation ring and drawbar assembly had been removed for installation on the replacement spindle which went right back into the machine. The cause of failure was readily apparent when the spindle arrived for disassembly, evaluation and quoting. As is so often the case, the grease in all four bearings of the front quad set had been completely washed out, causing the #1 front bearing to fail. When the rolling element cage disintegrated, the debris knocked out the other three bearings. We also noted during our dimensional inspection that the tooling taper ID was worn below gauge line.  

SOLUTION

We performed a precision grind, chrome plate & finish grind of the tooling taper ID to restore proper functionality. When all components had been thoroughly cleaned, we reassembled the spindle with new bearings, setting the proper preload, and replaced the o-rings and assembly screws. Our final QC process included run up of the spindle with vibration & thermal analysis during the three hour test run. Unfortunately, we could not check tool retention force or trim balance the spindle because our customer had retained the previously mentioned drawbar assembly and rotating parts.

DETAILED CAUSE OF FAILURE

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