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 The extrapolation of bed compensation outside the probed area was improved in firmware 1.18beta3.

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