Z height strangeness



  • Hi all,

    Fairly new to 3d printing and certainly new to the Duet Wifi.

    Have got a problem where I (manually) level my bed as I have no IR probe and when I got to print always starts about 0.2mm below the freshly levelled z0.

    I don't understand why I can home everything, level the bed on multiple positions and then when it comes to printing the print starts at a completely different z height.

    How can it go lower than z0 as set by my Z end stop (two wire close/open switch)?
    And why is it doing it??

    EDIT:
    I have no z offset in the GCode of my slicer (Simplify 3D)

    My end stop set up is as follows:

    [[language]]
    ; Endstops
    M574 X1 Y1 Z1 S0                                                               ; Set active low endstops
    M558 P0 H5 F120 T6000                                                          ; Set Z probe type to switch and the dive height + speeds
    G31 P500 X0 Y0 Z0                                                              ; Set Z probe trigger value, offset and trigger height
    M557 X25:175 Y25:175 S20                                                       ; Define mesh grid
    
    

    Note: G31 was set as

    G31 P500 X0 Y0 Z2.5

    so I changed it to 0 with no difference.

    Should I have increased it instead?


  • administrators

    Please post the contents of your homez.g and homeall.g files.



  • Here's homez.g

    [[language]]
    ; homez.g
    ; called to home the Z axis
    ;
    ; generated by RepRapFirmware Configuration Tool on Mon Mar 05 2018 14:15:11 GMT+0000 (GMT)
    G91               ; relative positioning
    G1 Z5 F6000       ; lift Z relative to current position
    G1 S1 Z-185 F1800 ; move Z down until the switch triggers
    G92 Z2.5           ; set Z position to trigger height
    
    ; Uncomment the following lines to lift Z after probing
    ;G91              ; relative positioning
    ;G1 Z5 F100       ; lift Z relative to current position
    ;G90              ; absolute positioning
    
    

    And here's homeall.g

    [[language]]
    ; homeall.g
    ; called to home all axes
    ;
    ; generated by RepRapFirmware Configuration Tool on Mon Mar 05 2018 14:15:11 GMT+0000 (GMT)
    G91                     ; relative positioning
    G1 Z5 F6000             ; lift Z relative to current position
    G1 S1 X-205 Y-205 F4800 ; move quickly to X and Y axis endstops and stop there (first pass)
    G1 X5 Y5 F6000          ; go back a few mm
    G1 S1 X-205 Y-205 F360  ; move slowly to X and Y axis endstops once more (second pass)
    G1 S1 Z-185 F1800 S1    ; move Z down stopping at the endstop
    G90                     ; absolute positioning
    G92 Z2.5                ; set new Z position
    ;G1 Z5 F100             ; uncomment this line to lift the nozzle after homing
    
    

    I'm guessing the problem is those G92 commands?
    Should they be set to 0 then?

    If so, I'm curious why the riprap configure tool sets this as default. Especially when it clearly seemed to understand that I had a z end stop switch only and no probe.

    Surely it would have been better for it to default to 0 and not wreck peoples beds 😞



  • OK, so I've altered the home files' G92 commands to Z0 and it has worked well. Phew!

    @dc42: thanks for pointing me in the right direction. (great board btw)


 

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