SOLVED G30 - Retracting after Z probe triggers

  • I hope everyone is doing well. I am building a small form factor 3D printer for teaching purposes. I am using a John FSR for my Z probe, which is wired to the Z probe connection on the Duet 2 wifi. When I call G30 the print head lowers until it triggers the Z probe. However, after triggering the Z probe the Z axis immediately retracts away from the bed until it reaches its maxima.

    Looking at the documentation, this appears to be abnormal behavior. I would expect (and prefer) the Z axis to remain at the probing height after homing.

    The bed is very small, so I am only probing the center once. Also, the FSR sits ontop of a 10mm thick aluminum disk, which I move onto the before homing the z axis.

    Firmware 2.02

    Relevant Code:


    ; General preferences
    M208 X-8 Y-7 Z0 S1 ; Set axis minima
    M208 X127 Y166 Z80 S0 ; Set axis maxima

    ; Endstops
    M574 Z0 S0 ; Define active low and unused microswitches
    M574 X1 Y1 S1 ; Define active high microswitches
    M558 P5 X0 Y0 Z1 H80 F120 T12000 ;
    G31 X0 Y0 Z10.26 ;

  • Moderator

    @drdflo said in G30 - Retracting after Z probe triggers:

    M558 H80

    The dive height is set to 80mm. Try maybe 20?

  • Thanks for the reply Phaedrux, but I don't understand why I should adjust the dive height. Correct me if I am wrong, but isn't the dive height how far the Z-axis should travel before erroring out? If the Z-axis is at its maxima (80mm) and the dive height was 20mm it wouldn't reach the FSR.

    Just to reiterate the problem: the z axis returns to the maxima after touching the probe, which wastes time because the print head then has to return back to the bed height before starting the print.

  • Moderator

    G30 will travel until it gets a trigger. The dive height is how high it will return to after it has triggered in preparation for the next probe, for instance when doing a G29 mesh.

  • [Solved]

    Thank you for your response! All sorted out.

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