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Grbl servo motor not working


Oct 16, 2022
I am trying to make a arduino cnc pen plotter. I have the following things:
  1. Arduino Uno
  2. Cnc shield v3
  3. Grbl v1.1
I am using a sg90 servo motor to move the pen up and down. The signal pin of servo is connected to Z+ pin of the cnc shield. But the servo doesn't move. The X and Y axis stepper motors works perfectly fine.
I have tried all M3, M03, M5, M05 commands, nothing works. All the electronics are in working condition.

If anyone knows the answer, please help


Jul 6, 2006
Hillsboro, New Hampshire
You'll may find this thread locked soon, it may be considered too "Home Shop" for this forum. But the first thing I'd try is swapping axis motor connections (if possible and with movement commands limited to stay within mechanical constraints), and see what happens. If the new axis works then it's likely a motor or cable fault, if it doesn't it's probably the Z axis control path is faulty.