IR probe offset fluctuates

  • Ive got a kossel mini with a duet running firmware: 1.10+4 (2016-03-30) and a DC42 IR probe.
    Recently Ive had a few problems calibrating, the issue is that the Z probe height offset seems to vary.
    So far i've:
    Heated the bed and extruder to PLA temperatures.
    Homed the printer
    Brought the nozzle down to the print bed using a piece of paper to determine where Z=0.08mm and set Z to that height
    Lifted the nozzle 5mm
    Run G30 s-1
    Read off the head position as Z=1.09 and updated the relevant section in the configuration file.
    Run G32

    Then when I bring the nozzle back down to the bed, I can take it all the way to Z=0 and there still be a slight gap between the nozzle and the bed.

    Interestingly I noticed when bringing the nozzle down to the bed the IR probe is triggering at Z=1.30
    If I repeat the above process again running G30 s-1 now gives me a Z height of 1.27mm.

    Has anyone had any experience of this or is there something i'm overlooking?

    The level of ambient light isn't changing and the z probe board is firmly attached to the Effector assembly.


  • Are you sure your mount for the z-probe is thight enough to reproduce the height exactly ?

    When I used a printed mount for my z-probe with a clamp in fixing, my height also was changing.
    After using a metal mount system with having the z-probe screwed to it, the height is realy reproducable .
    You already mention you have variances in about only some 1/100 mm.
    The remaining factors are heat elongoation and the bad results when I hit the bed with the nozzle for some reason.

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