Quote Originally Posted by JAZZCNC View Post
If you haven't been homing each motor then Yes, it's exactly the same. I can't see how the motors won't have jumped in opposite directions at some point and if you haven't got reference marks to check against then it could be very hard to see. It would be a random occurrence and you could have just been lucky that it's not twisted up enough to show up.? Still, it wouldn't be my first choice if I'm honest.!
Surely the mechanism will relax mechanically every time the machine is switched off and turn the motors back to the same starting positions. There may be a small twist at switch-on but it won't accumulate over multiple on/off cycles.

routercnc,
Thanks for the reminder pictures.
Sounds like you're talking yourself into a redesign to have a single motor and belt for Z as you have for X (or s it Y?). Was there a good reason for not using the same technique?

Kit