[mwk24]

Good morning, WE are having issues with the x axis coupling randomly slipping and therefore losing its position randomly. This only happens sporadically, and is not under any cutting load at all at times when it has done it . A program may be running but no material is being removed. The coupling screws are all torqued to spec , and they are always tight when we check again after seeing that the "X" axis has lost its position. After now removing the entire coupling this morning it appears to be in excellent shape with no indication of excess wear to any of its componets or on the ballscrew or drive motor shafts. This is a very erious situation because we are machining large billlets of aluminum so when cutting the spindle has the potential to ram into the block , but tech thinks it is okay still . Whenever this movement happens it is never the same amount nor in the same direction nor does it throw any alarms. Does anyone have any experience with this ???? Or any insight on what may be causing the issue and what we need to do to prevent this !!! Thank you so much in advance.

[Jim Dawson]

You mention ''excess'' wear. There should be no wear at all. If the coupling is slipping on either end, there should be some galling or grooving in the mating parts. I assume you have witness marks on either end of the coupling to confirm slipping. The other possibility could be an encoder issue.

Are you losing your X zero then the slip occurs? I use similar couplings on my lathe, and the only time I had a slip was during a crash. The X machine zero moved about 0.003'', but hasn't moved since.

For a test, why not write a quick program that rapids the X a few inches in either direction and run maybe 50 repetitions, check zero before and after. Also check the witness marks on the coupling.

If slip is occuring, then new bushings or new coupling might be in order. If the shaft is damaged, then maybe some bearing mount LocTite might be useful. https://www.mcmaster.com/loctite-retaining-compounds If used, buy the primer also. Not the best solution, but might solve the problem and keep you running.