Bed mesh probing not using the full bed size



  • My IR probe is on the line with nozzle in Y direction but it's mounted +40mm in the X direction. Printbed is XY zero at front left of bed. When I try to probe now it starts approx 50mm into the bed in the X direction and I can't make it home at X 5 or so that I would like. Is this because the axis would have to move below X zero?

    M208 X243 Y140 Z150 ; set axis maxima and high homing switch positions (adjust to suit your machine)
    M558 P1 X0 Y0 Z1 H3 F200 T5000 R0 ; Z probe is an IR probe and is not used for homing any axes
    G31 X40 Y0 Z0.960 P500 ;897 ; Set the zprobe height and threshold (put your own values here)
    M557 X0:240 Y12:150 S35 ;setting mesh probe

    Edit: additional info, the Bed zero is front left but homing switches is in oposite direction. I have set XY max so that it goes at edge of bed in oposite direction of homing switches when it's zero.


  • administrators

    Yes. If the nozzle can go to negative X, use M208 with the S1 parameter to specify how negative X can go.



  • Thank you, will give this a go. I also noticed that I got some weird height drop on the middle of my bed when probing (glass on black bed) and I noticed that there was a shiny screw on the center of the bed. Painted this black and then it suddenly was a lot more flat. Did not know that this could affect the bed probing. I also have some weird results close to the edges and I wonder if this is related to light shining in on the glass and throwing the sensor off.

    Would you recommend probing only 2-3 cm into the bed to be on the safe side? When I print on 3mm boro glass that s hould be pretty flat I assume that the surface is pretty flat so any compensation on the edges will just be linear more and this is handled by the bed mesh software I assume or does it just set a flat Z outside the probe area ?


  • administrators

    I suggest you measure the trigger height neat the edges of the bed, to see how close you can get before the trigger height is affected. See https://duet3d.com/wiki/Using_mesh_bed_compensation#Checking_the_trigger_height. The extrapolation of bed compensation outside the probed area was improved in firmware 1.18beta3.


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