Problem tuning pressure advance

Discussion in 'Getting Started' started by John Meacham, Jan 30, 2020.

  1. John Meacham

    John Meacham Well-Known Member

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    My toolchanger has both bowden and hermera print heads. I tuned pressure advance using the technique specified here https://forum.duet3d.com/topic/6698/pressure-advance-calibration/2
    (attached is my modified advance_cal.py that is tool agnostic) I am running between 5 and 70mm/s When I run it from 0.0-0.1 and the hermera, I get what is expected, the slow parts are thick at the bottom and the fast parts are thin, as it progresses the slow parts get thinner and the fast parts thicker until they equalize at around S0.043. However, when using the bowden I see no change from even over ten times the range, 0.0-1.0, the fast parts are always thinner than the slow parts by what looks like the same amount, when I change the range even further and test from S1.0-S3.0 I see just the middle part of the fast move start to thicken while the begining and end of the fast moves thin even further. The pressure advance retractions are getting far enough to yank the filament dangerously far and fast to the point i am worrying about jamming also so I am pretty sure more pressure advance isn't the answer.

    Attached is my hermera from 0.0-0.1 in blue and bowden from 1.0-3.0 in white. you can see the middles of the fast sections start to thicken at the top of the white.

    Any idea what is going on?
    out.jpg
     

    Attached Files:

    Nibbels likes this.
  2. John Meacham

    John Meacham Well-Known Member

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    So I have not figured out this issue yet, but in what is probably one of my most silly side-quests due to not having a ruler to measure my filament handy. I got distracted from debugging to design a magnetic filament measuring sensor compatible with e3ds based on what I had in my junk drawer. I'll post the final design to thingiverse, it only uses ~$15 worth of parts some of which you are likely to have sitting around.

    out.jpg
     

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