Daewoo L200A Spindle Repair

Daewoo L200A Spindle Rebuild

Our customer sent in this Daewoo Lynx 200A 5000 RPM lathe spindle which had seized up. They indicated that the spindle had become very noisy, but then proceeded to run it for another two days. Our free evaluation showed that the grease lubricated bearings failed due to extreme coolant contamination, which likely occurred because a front cover drain had become completely blocked. We also discovered that the pulley ID and the pulley journal OD were both severely fretted. This damage was corrected by grinding, chrome plating & finish grinding the pulley journal and replacing the pulley. We replaced the pulley because you cannot G/P/G two mating surfaces.

This customer made two critical errors which lead to having to us rebuilding the spindle with new ABEC 7 class precision bearings. The first was not following a preventative maintenance schedule to include checking that front cover drain remained clear. Coolant will eventually get into your spindle, and it needs a way to get out. The second error was to ignore the signs of impending bearing failure, in this case the extremely loud noise during operation. Not heeding this increased the cost and lead time of the rebuild process. The customer could have also taken steps to check the operating temperature of the spindle, or even could have used vibration analysis to determine bearing condition.

Possible cause of failure:

  • Spindle was seized incoming, bearings contaminated with coolant sludge, front cover drain was clogged.
  • Pulley journal is fretted & has two undersized bands -37/-45µ, pulley ID is fretted & has two oversized bands +60/+70µ.
  • Pulley nut has pre-existing punch marks from attempts at removal.
  • OD lathe taper and face are very pitted, pre-existing tick mark on taper.

Recommended action:

  • Clean, inspect overall dimensions.
  • Replace bearings, drive pulley, pulley nut and o-rings.
  • Grind / chrome plate / finish grind pulley journal.
  • Kiss grind OD lathe taper and face – some pitting may remain.
  • Adjust preload, balance, assemble and break in. Final quality control inspection.


DETAILED CAUSE OF FAILURE

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