Mori Seiki SL-0H Spindle The effects of age, contamination & a minor mishap



CHALLENGE

Mori Seiki SL-0H, 6,000 RPM, permanent grease bearing lubrication, belt driven The effects of age, contamination & a minor mishap Prior to the arrival of this 1980’s-era CNC turning spindle, our customer indicated to us that the spindle had been crashed recently, resulting in repeatable axial endplay. We were able to confirm that the bearings had lost preload which allowed the excessive axial motion of the shaft. What our customer did not realize was that over time, ingress of coolant had severely degraded the grease in all of the bearings. In fact, the rear roller bearing had completely failed & the rolling elements were corroded. Despite the condition of the bearings & the crash of the spindle, our full dimensional evaluation did not uncover any significant deviations of the bearing journals & shoulders, housing bores, or lathe taper.  

SOLUTION

This rebuild was what we often refer to as a “straight” repair, that is, little or no dimensional rework was required during the spindle rebuild. We reassembled the spindle with all new bearings, o-rings & assembly screws. We set the proper bearing preload & test ran the spindle for six hours to break in the new bearing grease (especially critical with the rear roller bearing) while recording the thermal & vibration characteristics. Our customer is very pleased that the spindle produces a surface finish like it did when it was new, and we expect that it will perform that way for years to come.

DETAILED CAUSE OF FAILURE

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