Random axis motion

Hi, I recently updated the Repetier firmware on my Arduino Mega for my cnc machine, and it works great, except when I jog one of the axises, sometimes another axis will briefly move as well upon initially moving the axis I'm trying to move.  I've tried to figure out what changed, but am not having any luck.  Any ideas?


  • So it does not happen the full move only a bit at every short move? Did you change cable arrangement with the update so that you get some crosstalk e.g. to step pin of that motor?
  • I think it's related to using backlash compensation.  I also noticed that a backlash compensation axis will move strangely.  There is the expected lurch when the stepper changes direction, but then midway through the move, there will be a sudden start and stop of motion, very quick and abrupt.  Quite mysterious!  Would linking to a video of it help diagnose this problem?
    Thanks again,
  • I meant to say midway through the move, there is always a sudden stop then restart motion, using backlash compensation. 
  • I'm sorry, I don't have internet at my house, and I'm thinking through this as I type.  I now realize the momentary pause in motion in one axis, is likely to wait for the backlash to be made up for in the other axis.  Seems to make sense to me now.  I need to do more testing. 
    Thanks again for the great software!
  • Ok, backlash is something you really should prevent. What it does is when an axis changes direction it adds a small move f size backlash in new direction. But it does this for the same axis and should not move an other axis. But as a test set all backlash distances to 0 to see if it comes from backlash. Or do you mean machine has backlash and you see oppsite axis move just because it has backlash without the motor being moved?
  • I finally got back on the internet.  Unfortunately my cnc machine uses old acme leadscrews, and although I put antibacklash nuts on them, they still have a little backlash, but your backlash compensation setting is working great so far.  I think the random axis motion was just a fluke, haven't had time to dig deeper into it.  But thanks for the great support you provide!
  • Ok, for z it is not that much of a problem also it might change z somewhere on it's own through gravity.
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