M671 two independent Z motors / four test points

  • Our printer uses two z motors (one left and one right) with a unique belt configuration that lifts the gantry from both front and rear.

    Our design has been described before, but take a look here for a quick look at how it works: https://www.instagram.com/p/B-klDdcD_ld/

    What we'd like is to call M671 to set the belt position for all four corners. According to the documentation "The M671 command must come after the M584 command and must specify the same number of X and Y coordinates as the number of motors assigned to the Z axis in the M584 command".

    Can G30 be referenced for all four corners with two z-motors? Or is it limited to just two since only two motors are defined?

    Would this be possible? Even though the two belts are locked in place, there is the opportunity for minute variances that we believe this would solve for. Thanks

  • After thinking about this since I posted it, maybe this isn't necessary.. If there are variances front to rear on either side, they should be static and mesh bed compensation would resolve it. My current M671 is set as follows to check each motor directly in the middle of the z-belt loops..

    M671 X-82:424 Y-175:-175 S5

    I'd still appreciate feedback though. Thanks

  • After playing with this for awhile and understanding how it works, I see now what I asked is not possible as it physically adjusts each motor to compensate.

  • Moderator

    @oozeBot said in M671 two independent Z motors / four test points:

    M671 X-82:424 Y-175:-175 S5

    I'd guess that half way along the Y axis would be Y175:175, not -ve 175.


  • While reviewing the RRF 3.2 roadmap, I see the following item:

    Consider making 2-, 3- and 4-point probing available to correct an overall tilt while still using mesh bed compensation

    This is what I was trying to ask for, but wasn't very clear.

    Any idea if this will make the release? I'd love to see a 4 corner probe routine which then applied save mesh bed compensation.


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