Homing procedure in firmware



  • See Klipper’s implementation of endstop phasing. It remembers microstep count at end stops during calibration. Subsequent endstop hits move to the nearest micro stop count same as set in calibration.

    I haven’t used this so I don’t personally know how it performs. Have heard anecdotal reports of it being accurate enough to make delta bed probing unnecessary.

    https://github.com/KevinOConnor/klipper/blob/master/docs/Endstop_Phase.md



  • could someone explain the difference of finding the exact home-point and missing it for 1 or 2 mm?



  • @spllg said in Homing procedure in firmware:

    could someone explain the difference of finding the exact home-point and missing it for 1 or 2 mm?

    With a printer, the object would be printed at a slightly different position on the build plate. So it only becomes an issue if you intend to print at the extreme limits of an axis travel. Although if it is inconsistent by that amount, and you re-home after a power outage, in order to resume, then that inconsistency would cause a problem. In reality, that is highly unlikely to occur.



  • @spllg it matters a lot for deltas.



  • Yeah, to repeat: Homing is absolutely critical for Delta/Kossel. It directly sets nozzle-to-bed at Z0. And it needs to set it accurately enough to get a good first layer. Most homing (switches) are not anywhere near accurate enough for this.

    In fact, in my opinion, this has been the #1 barrier to wider adoption of Deltas, that is, getting Z height set initially, and keeping it set to within 1/10 or so of a layer for print after print.

    The smart effector largely solves this, because you can probe before every print.



  • Is it really a (that much) bigger issue on Deltas? Having a slight headache trying to wrap my head around how, say 0.1mm error on the tower would translate to anything less than or equal 0.1mm error in Z. That said my Delta has been sat in parts in a box for way too long..



  • @bearer said in Homing procedure in firmware:

    Is it really a (that much) bigger issue on Deltas? Having a slight headache trying to wrap my head around how, say 0.1mm error on the tower would translate to anything less than or equal 0.1mm error in Z. That said my Delta has been sat in parts in a box for way too long..

    You've got it... they are equal.

    How precise do you need the first layer to be? IMHO, 1/10 of layer height, so quiet often, 0.02.



  • @Danal do be honest I've never given it much thought beyond adjusting with increasingly large sledgehammer until it works as if I was a mechanic or something..

    I was just thrown as I read it to be a bigger problem on Deltas than in general, which I couldn't make sense of. Odds are on average the error would be less on the delta due to cosine "error" between the travel on the tower and what the kinematics do, worst case scenario all errors are the same and in the same direction giving or some of the compounded error is shifted from Z to XY plane.

    But yes, homing is important, and I guess I've been lucky as my stuff has always been more repeatable than I could measure. (+/-0.02-ish)



  • @bearer said in Homing procedure in firmware:

    @Danal do be honest I've never given it much thought beyond adjusting with increasingly large sledgehammer until it works as if I was a mechanic or something..

    I was just thrown as I read it to be a bigger problem on Deltas than in general, which I couldn't make sense of. Odds are on average the error would be less on the delta due to cosine "error" between the travel on the tower and what the kinematics do, worst case scenario all errors are the same and in the same direction giving or some of the compounded error is shifted from Z to XY plane.

    But yes, homing is important, and I guess I've been lucky as my stuff has always been more repeatable than I could measure. (+/-0.02-ish)

    Yah, and it really doesn't matter much on X and Y. As others have said, so the print is in a slightly different spot on the plate... Thus things like the Prusa I3 Mk3 which has stall detect on XY and a PINDA (inductive) probe on Z.



  • Guess we're on the same page, pardon the pedantic antics:)


  • administrators

    @Danal said in Homing procedure in firmware:

    Yeah, to repeat: Homing is absolutely critical for Delta/Kossel. It directly sets nozzle-to-bed at Z0. And it needs to set it accurately enough to get a good first layer. Most homing (switches) are not anywhere near accurate enough for this.

    In fact, in my opinion, this has been the #1 barrier to wider adoption of Deltas, that is, getting Z height set initially, and keeping it set to within 1/10 or so of a layer for print after print.

    The smart effector largely solves this, because you can probe before every print.

    Even with perfect microswitches, you would still need to do a single probe to set the Z=0 height, to allow for the expansion of the frame with temperature.


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