Milltronics TT-80 Spindle Repair

The Milltronics TT-80 is a CNC bridge mill made for machining very large parts.  It comes equipped with a grease lubricated and coupling driven spindle capable of running up to 10,000 rpm.

CHALLENGE

Our customer told us that this Taiwanese Cells spindle from a twin table vertical machining center that had been previously repaired, but that they had no confidence in the quality of the rebuild. We had to agree with their assessment upon receiving the spindle. The front bearings were quite noisy when rotated in assembly, and we recorded high velocity readings during our incoming test run and vibration analysis which often indicate improper bearing preload or perhaps a misalignment. Additionally, it was noted that the actuator was incorrectly adjusted to allow for proper drawbar operation. Upon disassembly, we found that the front bearing inner spacer had spun on the journal causing severe wear, and that the spacer was heavily damaged as well.

SOLUTION

We completed a green grind, chrome plate, and finish grind of the damaged bearing journal, and manufactured a new set of bearing spacers.  We rebuilt the spindle with all new ceramic bearings, Belleville springs, o-rings and assembly screws.

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.