G29 Grid Questions

  • Searching through, this seems to have been discussed before, but I'm not tracking on something.

    I've got the following definition for my bltouch, mounted to the right of my nozzle:

    M307 H3 A-1 C-1 D-1 ;Disable Heater 3. This is needed to free up the PWM channel for the BLTouch
    M558 P9 H5 F750 T3500 ;Define a new probe type
    G31 X36 Y-2 Z2.2 P25 ;Define the Location of the BLTouch relative to the nozzle
    M557 X2:295 Y15:231 S35 ; Define mesh grid

    My printable area is just under 300x230 and my BLTouch sits 36mm to the right of my nozzle.
    I've defined M557 of X2:295 as X1 still contacts my limit switch. However, when running G29, I see;

    Warning: Skipping grid point (2.0, 50.0) because Z probe cannot reach it
    Warning: Skipping grid point (2.0, 85.0) because Z probe cannot reach it

    Etc, on again for each time it attempts to probe X2. Now, the probe still actuates at those locations.

    I think I understand that G31 defines the probe offset, so my question is whether M557's X/Y coordinate limits are defined relative to the NOZZLE or the PROBE?

    Or if I've hosed something else up here, feel free to make me awares 🙂


  • administrators

    M557 defines the coordinates you want to probe. Your probe is offset by +36mm from the head reference point, which is the nozzle unless you are using a tool offset, so unless your M208 commands allow the nozzle to move to X= -34mm, then x=2mm is not reachable by the probe.

  • @adamx said in G29 Grid Questions:

    M557 X2:295

    Use M557 X36:295

  • So, in short, the dimension constraints passed in M557 are relative to the probe? Not sure where an M208 factors in here?

  • I think of it as m208 is where the nozzle can get to and m557 is where the probe can get to.


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