Methods to adjust movement pattern for g29 probing



  • I can observe a slight tilt on my x carriage during g29 probing by that the probe consistently measures 0.07mm less when moving to the probe point from the right than when it moves to the probe point from the left.

    Now ideally this should be removed from the mechanics, but in reallity it will be hard to ensure that there is no such tilt at all and for printing it does not really matter as the nozzle unlike the probe is on the carriage centerline so the nozzle does not change height it only get a very very slight angle shift, so redesigning mechanics for this is a bit overkill.

    The actual problem is really only during g29 probing of the bed as the carriage approaches each probe point from alternating directions so automatic bed compensation thinks my bed is wavy with a period that matches 2x the probe pitch.

    For me this is only a problem on the x axis, but for a general soulution I guess it can also occur on the y axis.

    I would like to see some way to adjust how the bed is probed instead of the default zigzag pattern with x low to high, y, then x high to low. Possible additional patterns could be
    x low to high, y, then x low to high again (making sure to approach the first x point from the low side by overshooting the return then coming back)
    y low to high, x, then y high to low
    y low to high x then y low to high

    Is there a way to achieve this now? If not could this be interesting to add in the future?


  • administrators

    It's not possible to do that at present with G29 mesh bed compensation, although you could do it with the older 3, 4 or 5 point compensation that G32 and the bed.g file supports. Supporting it in G29 is not trivial because the firmware would not only have to check that the probe point is reachable, it would need to check that the overshoot position is reachable too, and probably allow the overshoot to be configured.



  • Understood.
    Now assuming that most printers will usually only be vulnerable to this on one axis just providing the option of y first or x first is likely good enough for almost all cases.


  • administrators

    Feel free to add this feature request to the wish list at https://www.duet3d.com/forum/thread.php?id=961. Many of the items on that list have now been implemented, so I will start a new list soon.


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