Matsuura H Plus-300 Spindle performs like new again



CHALLENGE

Contamination, bearing fatigue & component wear Matsuura H.Plus-300, 15,000 RPM, grease bearing lubrication, coupling driven This spindle came to us four years after we initially rebuilt it for our customer. Upon disassembly, we first noticed that the entire interior of the spindle was contaminated with coolant, even in the rear roller bearing. The #1 front angular contact bearing was thoroughly contaminated component. We observed heavy fretting on the outer races of both front bearings and in the front housing bore. The housing was egged & oversized by up to 30µ where the bearings are located (ISO is ±7.5µ). We also spotted wear on several other spindle components that ranged from slight to significant. The tooling taper had excessive runout, and the gripper (collet) fingers, gripper sleeve & drawbar t-bar pusher were worn on critical contact surfaces. The drawbar shaft also had significant wear from the action of the gripper fingers & the drawbar spring, which had left deep chatter marks. Our overall conclusion was that the spindle bearings & the other components were simply fatigued & worn from use.

SOLUTION

We performed a grind, chrome plate & finish grind of the front housing bore to bring that ID back to spec, which will help to extend the life of the new angular contact bearings. Because our customer does not use dual-contact Big-Plus tooling in this machine, we were able to correct the excessive taper runout with a simple one-step kiss grind.  We reassembled the spindle with all new bearings, o-rings & assembly screws, and installed a brand new drawbar, spring & gripper assembly which corrected all of the wear issues we had observed. We set the proper bearing preload & test ran the spindle for five hours to break in the new bearing grease while recording the thermal & vibration characteristics. Our final outgoing dimensional QC indicated (among other things) tooling taper runout of less than 2µ. Assuming similar operating conditions in our customer’s machine, we do not anticipate seeing this spindle again anytime soon.

DETAILED CAUSE OF FAILURE

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