Z Probe Home XY Strange behaviour

Hi, I have been trying to setup software correction autolevel on a i3 clone using v1.0.1 firmware for some time and its driving me mad.
I have install an inductive probe 56mm behind my x carriage and am setting up the Z home first and when I set the probes offset to 56 and the zhome_y_pos to zero I get the fatal error saying -56 is invalid.
That seems correct (as the bed can't move -56 to position the probe at zero) but when I set the home to 56 (essentially 0) it moves the bed 56 so the probe is at 112 while it takes the reading then moves back to zero??
Am I confused or is something strange happening??


  • "I set the home to 56 (essentially 0)"

    What does that mean in settings?

    y home should still be 0, you just need to tell homing to probe at y=56 so it can make the move (or probe at 80). Select homing order with preheat so you can set where to probe z, set preheat temperature to 0 as you do not need that.
  • it's wierd, I set the probes offset to -56 and zhome_y_pos to 0 and thats fine except the bed still moves to 56 while probing and the back to 0 for the home, not a big deal. I didn't realise the probe points needed to be negative.
    You can delete this post.
  • Normally extruder 0 is teh reference (offset 0). Then probe position is relative to this. positive y means behind the extruder negative before extruder. You measure where the current active extruder is and that is the move while probing that you see. So if probe is behind extruder you need to mease at 56 so it can move 56 to the front when activating the probe.
  • Well I have the offset on 56 now with the zhome_y_pos also set to 56.
    When homing, it probes (extruder @ 0 & probe @ 56) but then moves the bed (extruder @ 56 & probe @ 112) for the second probing which i guess is the "Reduction factor 2nd test".
    It moves back to the correct position after though.
    Autolevel is also working.
  • You will see one of these moves as offset is activated and deactivated, so I assume it is correct now.
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