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Cannot Home or move in single axis

Yesterday I dropped the PCB so that I could check the max power setting. After reassembly, the Home function no longer works and movement commands (using UGCS) are always diagonal no matter if X or Y movement is requested.

Issuing the $H command initiates a diagonal move towards the origin when it should move to the X axis home and then to the Y axis home. Activating the X axis microswitch stops the diagonal movement. Activating the Y axis microswitch restarts the diagonal movement.

I have reset the GRBL settings to the defaults.

Help would be greatly appreciated. Nigel


  • Hi Nigel,

    The first thing to check is that the stepper drivers have not been dislodged.

    Please check they are plugged in correctly as per page 41 of the User Manual.

    Place the laser carriage in the centre of the machine and turn it on. Then enter a $x command (to unlock it) without homing. If you enter movement commands such as:
    g0 x20
    and g0 y20

    does it move correctly?

  • Issuing G0 X20 moves the head diagonally towards the home position. By this I mean that BOTH the X and Y positions are incremented simultaneously.

    G0 X-20 returns the head to the previous position, further from the home position in both the X and Y axes simultaneously.

    This means that multiple G0 X20 commands executed with the head originally positioned in the centre of the work area will move the head to the home position.

    Exactly the same movements are made if the commands G0 Y20 and G0 Y-20 are sent.
  • This would be the case if only one motor was working because of the coreXY belt setup.
  • OK. I have disconnected the belts. Only the motor closest to the PCB turns with any G0 command. That motor make the same move for X10 as Y10 and X-10 Y-10. The motor furtherest from the PCB does not rotate at all.
  • With the machine turned off, swap the stepper driver boards around and see whether the other motor turns.

    This will determine if the stepper driver is damaged.

    Let me know if you need more info on how to do this. Please make sure the orientation of the drivers is correct as per the user manual.
  • Thanks, I suspected that would be your response. However, I will not have access to the machine until later today to carry out this test.
  • The plot thickens. There is no change to the diagnostics after switching the stepper driver boards. In other words, the only stepper which turns is still the one nearest the PCB.

  • I have also swapped the motors. Again, it is only the motor on the stepper furtherest from the power supply/USB connectors which turns. For what it's worth, there are three small LEDs on the face of the board. One red LED closest to the centre of the board is red and on. The other 2 (one red & one green) are both flashing.
  • After disconnecting UGCS the dual LEDs stopped flashing. The single red LED stayed on.
  • This LED operation is normal. Red indicates power and the other are transmit and receive signals.

    The best thing is to return the board and we will replace it for you.

    I will contact you directly with the details.
  • Thanks, your support has been great.
  • I have sent PCB by Express Post and included an addressed Express Post sachet for you. Thanks again, Nigel
  • Good service warrants plaudits... the replacement arrived three days later - Thanks!
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