Left and right Y axis not moving in sync

Just finished building and mounting my longmill. After mounting I noticed when I jog from back to front the left Y axis stops before the right Y axis (hits the stop first). I adjusted the nuts on the lead screws again, and I cant feel any play on the X gantry. I dont know what to look for now.

@JimBabcock24 Welcome, Jim.

When you say that the left side stops before the right, do you mean that the left side hits the front stop before the right side does?
If so, run it back and forth a couple of times, letting both sides hit the stops. It will make a gawdawful noise, but will not hurt anything. When you’ve done that, check to see if the X gantry is square to both Y gantrys. If it is not, you will need to shift one of the Y gantrys to make it square.


This is what I’d do:

  1. run Y back until both Y gantries hit the end to make sure they are in proper alignment and not binding.
  2. check they Y stepper motor cables. Are they plugged in securely at both ends? Are the screws tight and wires secure in the connectors on the controller end?
  3. Check the dip switches on the driver boards in the controller. There are instructions regarding this on the Sienci website.

Also measure the distance between the front and back feet. Mine has 1/16" difference, going against the stop does realign the X axis so you’ll need to verify which provides square alignment.