Does it make sense/is it possible to do bed leveling w/o center probin

  • I am currently on vacation with some time to think through methods to have simple bed leveling on a glass bed. Yes, I know, piezo's work well but it possible I would like to use what I already have.

    The idea is to have three permanent metallic towers on the edges of my delta to use for probing with either an inductive sensor or simple switches.

    Before a print the bed leveling could run based on those three points, obviously there will be no possibility to probe in the center before print.

    Could this work, do you guys have any experience? Can I configure Duet to work that way?

    For full delta calibration I'd use a 4th peace of metal that gets placed in the middle of the bed so that full calibration is possible.

    I have used this already as a proof of concept with some simple coins, worked pretty well, but this is not suitable for permanent use as I always needed to manually place the coin in thr middle and remove it for the actual print.

  • Hi can you explain a bit more what problem you are trying to solve. as best as I can make out, you have a glass bed, and inductive sensor?

    How thick is your glass bed? If its 3mm or less, then make sure you power your inductive sensor on 12v or 24v and place aluminium foil under the glass, then there is no need for metallic discs, you can probe anywhere, albeit with an x and y offset.

    If you have a microswitch (see Russ Gries post about sensor accuracy) it turns out they are very accurate. Make a mount to place one directly under the nozzle and just affix it for probing, measure the offset afterwards and you're there.

    Probing only 4 points is only going to resolve your delta autocalibration to 3 factors which is not great, for 8 factor autocalibration you need to probe at least 9 points. You mentioned piezo in your post, I won't spam it too much, just enough to say you can try to achieve a reliable, accurate probing system with inductive sensors all day long, and you won't get close to piezo contact sensors for accuracy, reliability and convenience.

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