Pressure Advance - not extruding at (moderately) high speeds



  • I'm trying to print this model for DDA Tuning: https://forum.duet3d.com/topic/13129/dynamic-acceleration-tuning-model

    I determined a PA Value for 0.3 to be the best according to that Test Cube.

    Machine is a Delta with Flying Extruder, about 25cm Capricorn TL (not XS) Bowden Tube from Flying Extruder to an E3D All Metal V6.

    It prints the Purge line fine and also the first layer (15mm/s).

    Then on the second layer the filament doesn't extrude anymore. The extruder tries to extrude on the straights and retrcact at the corners resulting in about 0 flow from the nozzle. Trying to print this thing on 100mm/s in vase mode..

    My Settings:

    config.g:

    M203 X18000 Y18000 Z18000 E12000								; Set maximum speeds (mm/min)
    M201 X9000 Y9000 Z3000 E6000									; Set accelerations (mm/s^2)
    M566 X3000 Y3000 Z3000 E3000									; Set maximum instantaneous speed changes (mm/min)
    M906 X1920 Y1920 Z1920 E1000 I20								; Set motor currents (mA) and motor idle factor in per cent
    M84 S180														; Set idle timeout
    

    Filament config.g

    M207 S1.5 F3500 R0 T1000 Z0.5										; Firmware retraction 
    M572 D0 S0.3														; Pressure Advance
    

    Not sure why this is happening with just 1.5mm Retraction and an PA value of 0.3.... trying to print the model with 100mm/s

    PS: it's also impossible to find a PA value where my corners are still reasonably sharp and I don't have a bulge at the retraction cube. By the time the bulge is gone my corners are completely round.

    Didn't have any of those problems on Marlin Linear Advance. I'm now trying to tweak PA for almost 2 weeks without any reasonable results.. what am I doing wrong..? 😕


  • Moderator



  • @Phaedrux yep. That's what I used to get to the value of 0m3 for PA.

    However: if the prints are smaller I get no extrusion at higher speeds.

    I have the same problem if I scale the PA cube down..



  • Do those parts have a lot of single extrusions? I found this exasperated this issue. Slowing down the print, re-slicing to reduce/remove the single extrusions helped, but obviously not a total solution.



  • @bberger What happens if you try printing the same objects at 100mm/sec with PA disabled (or set to zero)?



  • The PA cube (2 perimeters, Z-seam at the back) has massive blobs on the Z-seam and the DA "flower" in vase mode prints mostly fine with a slight overextrusion on the edges.

    I get rid of the blob at the Z-seam on the cube with about 0.3 PA (nice sharp corners too to about 0.35, becoming bulged at 0.4), but the DA model won't extrude anything at all after the first layer (constant back and forth of extruding and retracting) and has massive underextrusion at 0.15 PA with more round than sharp corners..

    Genuine V6 + 0.4 Nozzle, flying genuine BMG extruder with about 20cm capricorn TL bowden tube (nit the XS).
    Printing Anycubic PLA at around 210°C. 1.5mm retraction@60mms, 0 extra restart, priming tired both at my usual 10mms and also 60mms (which is more than the V6 can handle). 0.2mm layer height, 0.4 track width, 97% flow (calibrated on 2 perimeters to almost perfect 0.8mm width).



  • @bberger What microstepping do you use on your extruder? If you run M122 when you get the problem, does it show a high hiccup count?


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