Return to zero issues, possible UGS issue?

I need some help. I’ve been using the machine for a couple of weeks now and thought I had all the bugs worked out. Now suddenly when I hit the return to zero button in UGS and it tries to drive the machine Z up ~600mm before returning to zero. My work flow is as follows:

  1. With machine off move spindle to desired zero position
  2. turn on machine and connect UGS
  3. hit reset zero button in UGS
  4. use machine controls button to randomly move spindle thru all X,Y,Z axis to check all are moving ok
  5. hit return to zero button
  6. open gcode file and send to machine

Up until Friday night this has been working wonderfully. Now suddenly when I hit return to zero it tries to drive the Z-axis hundreds of mm up before returning to zero. As of Friday night it was consistently trying to drive up 300mm and now suddenly today it drives somewhere north of 600mm before returning. I know this because I’ve quickly hit the power switch, to prevent binding, and then watched the position in UGS continue to climb as it still tries to send the command to the machine.

In step 3 above, does work position and machine position match? Sounds like it is going to machine zero.


The “Return to Zero” button in UGCS uses the G28 command. Check your G28 setting using the grbl $# command.

If you don’t know about G28, search G28 on this forum.

I’m not sure exactly how my machine zero got set to some odd place suddenly (something dumb I did obviously) but resetting machine zero using the G28.1 command appears to have fixed my issue. Thanks.