FANUC ROBODRILL the motor killed this high-speed vertical machining center spindle



CHALLENGE

FANUC ROBODRILL, 24,000 RPM, grease lubrication, coupling driven

Our customer has a large complement of high-speed vertical machining centers which are used to produce job shop parts orders for their customers, as well as for mold making in support of their in-house injection molding facility. They contacted us while they were in the process of replacing a bad motor in one of their 24,000 rpm FANUC ROBODRILL machines. They felt that the spindle bearings were suspect as well, and asked us to evaluate the spindle in our facility. We found that the bearing grease was not particularly contaminated, and that the rear pair of hybrid ceramic bearings had significantly more wear than the front pair. This led us to the conclusion that vibration and shaft runout of the motor had caused the rear bearings in the direct-coupled spindle to repeatedly load and unload, causing premature deterioration.

SOLUTION

As we found no significant dimensional deviations of the tooling taper, shaft journals and shoulders, or in the housing bores, our solution was a “straight” repair of the spindle. We rebuilt the spindle with all new ceramic bearings, gripper force balls, o-rings and assembly screws. We completed this rebuild with our final test run, break-in, trim balance and final QC. With a new motor and a spindle that has received a high quality rebuild, our customer’s high-speed vertical machining center has rejoined the fleet and is operating like it was when they purchased it.

DETAILED CAUSE OF FAILURE

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