Problem- VF1 x motor z fault

[Fopec]

Picked up a vintage 1990 VF1 that has x axis issues. On initial zero return if the Y axis zeros before the x the machine errors out with 139. After tweaking the settings to move without zero return and jogging y back far enough to let x zero first, there is no error and the machine runs fine (as long as y is not near the front of the machine when you try to move x).

History-discovered after figuring out the workaround to run the machine that the x servo bearings were shot. Pulled the x servo motor (out of the coolant it had been soaking in) and replaced the bearings and brushes. Works good (and quiet) now but still get 139 error when y gets close to home.
Is the wiring harness shorting out?
Thanks in advance for any constructive commentary.

[haastec]

The 139 alarm generally indicates a problem with the encoder, but it does sound as though you have a problem with the X-Axis cable assembly. You should be able to see the only moving portion of the x-axis cable assembly under the front y-axis covers for inspection purposes. If the motor was in coolant/oil most likely the cable has been also which causes the cable insulation to become brittle and crack. This situation can still occur even if the cable appears to be fine.

Good luck!

[Fopec]

Thanks for the reply. I wanted to throw it out there before pulling the covers to probe around.

[JaredR1]

i would check the nitrogen levels, i had the same problems on our VF-4 not to long ago, it seems as it is a very common problem with older model HAAS machines it has happened on our VF-7 as well.

[Fopec]

Nitrogen level? Not sure what you mean. Counter balance cylinder maybe? If not, let me know. The z counter balance on this machine is a big shiny rock with 2 chains hooked to it. I pulled the covers and have been trying to wiggle the cables and get the machine to alarm out. Not working out so well. The new error is x motor overheat and the 139 z fault has gone away. This comes on when the y gets within 2 inches or so of the front limit switch as was happening before. As soon as you back Y off the error will clear and everything works fine. Still thinking it's a bad wire but I'm having trouble finding the bad spot. Any ideas?

[haastec]

Time for a new X-Axis cable. The problem will progress and either create an open circuit in the cable or it may short out and that could take the motor, the servo drive or both.

Good luck.

[Fopec]

I replaced the x axis cable as suggested. Not knowing how the wires were originally run I was actually staring at the problem and didn't realize that-
1. The cable housing is not supposed to be rock hard and split into 3-4 pieces (seemed like a funny design). Haastec made a good point about the coolant/oil destroying the wiring.
2. The insulation on the wires was not supposed to be split (I assumed some sort of stress relief strategy)
Lo and behold under closer inspection each of the “stress relief” spots in the encoder wire had its own broken wire right there before my eyes. Can’t believe I didn’t realize this the first time I had the covers off.
Something I learned that may be useful was an old bike inner tube works great to spin the screws and move the table around. The project took me most of the weekend but everything works great now. Thanks for the suggestions.