Mazak H630 Well-used, vintage workhorse machine gets a new lease on life



CHALLENGE

Mazak H630, 4500 RPM, grease lubrication, gear driven

The interior of this horizontal machining center spindle was thoroughly contaminated with coolant which had washed out all of the permanent grease in the bearings. The front cover drain was clogged with a sticky coolant/grease residue, and four of six front coolant nozzles were missing (the other two were crimped shut.) We observed significant damage and wear to the drive dogs and gripper fingers, and several Belleville springs were broken. The CAT #50 tooling taper was damaged at the mouth, with wear in the taper leading to poor tool contact and inconsistent, high runout up to 10µ. We measured high runout (6-12µ) on the tapered front roller journal, and the 85mm rear roller journal was worn undersized -5/-7µ (spec is +3/+13µ). The 150mm front housing bore was found to be egged (out of round) by 12µ.

SOLUTION

The first step in the rebuild was to grind, chrome plate and finish grind the tooling taper and rear roller journal, and kiss grind the front roller journal. We GPG’d the front housing bore as well. While the shaft and housing grinding was in process, we fabricated replacement drive dogs and coolant nozzles. After a thorough cleaning of all spindle components, we reassembled the spindle with all new bearings, Bellevilles, rear cover gasket, locking washer, o-rings and assembly screws as well as the new parts we previously manufactured. We trim balanced the spindle during the 6 hour test run-up and confirmed that the vibration & temperature readings and tool retention force were within specification. Final runout measured in the taper was 2µ and 10µ at the end of a 12” test bar.

DETAILED CAUSE OF FAILURE

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