Kitamura HX400iF, 13,000 RPM, gear driven, air/oil lubrication, 40 taper
Our customer indicated that this horizontal machining center spindle was humming and producing a poor finish. When we broke the spindle down for evaluation, we noticed heavy coolant contamination in the front bearing quad set. We also observed that the tooling taper was bell mouthed, and the drive dogs (keys) & gripper (collet) fingers were heavily worn. In addition, our dimensional inspection showed that the drawbar had >200µ of runout in assembly. When disassembled, the drawbar springs were found to be broken and the drawbar shaft was bent with bare shaft runout of >150µ.
Our overhaul of the spindle included grind, chrome plate and finish grind of the tooling taper. These grinding operations, which are performed in-house on one of our Kellenberger grinders, typically lengthen our normal turn times. Our customer could not afford the downtime on this critical machine, so they opted to pay a premium for us to accelerate the timetable for all rebuild operations. In addition to grinding the taper, we replaced the front quad set of ceramic bearings, rear tapered roller bearing, drawbar assembly including springs, gripper fingers, drive dogs, o-rings & assembly screws.
During our test run & final quality control, we monitored vibration and thermal measurements. Our customer reports that the spindle is running like a champ!