Mesh Levelling and negative homing probe offset question?



  • I have a 200mm x 200mm bed, y homing switch is at 0, but due to the design of the machine (Reach 3D cartesian), the x homing switch is offset, at -32.

    I set my axis minima as follows

    M208 X-32 Y0 Z0 S1 ; Set axis minima

    But when I try and go the mesh levelling with the following, it starts at X = -27 instead x = 5

    M557 X5:185 Y05:185 S17

    Should the mesh g code use co-ordinates relative to where 0,0 is, rather than co-ordinates that are relative to the x homing switch


  • administrators

    Yes it should use coordinates relative to 0,0. The coordinates probed will be those of the Z probe, not the nozzle. Do you have a Z probe X offset configured in your G31 command?



  • Yes My z probe offset as well, by around -8 on the Y axis, and +30 on the X axis (my printer isn't on at the moment but those are in the right ballpark)

    The layout is a bit like this (sorry about the ascii art)

    [Y Maximum Travel Y=210]

    [Bed Top Left Corner] –-------------------------[Bed Top Right Corner]
    [X=0,Y=190] [ X= 190, Y-190]
    | Bed |
    | | [X Maximum Travel X= 210]
    [X endstop] [ Nozzle ]–------------------------------------ [ Bed Bottom Right Corner] [Y endstop X=210, Y = 0]
    [X=-32,Y=0] [X=0,Y=0 ] [ Z probe] [ X=190, Y = 0]
    [X+30,Y-8]


  • administrators

    If your Z probe X offset is +30mm and you tell it to start probing at X=5mm, it has to place the nozzle at X=-25mm to position the probe there.



  • Ah I see, Must have been having a bain fart. thank you for your help.


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