PETG Stringing regardless of slicer settings *SOLVED*

Discussion in 'E3D-v6 and Lite6' started by KramE, Dec 13, 2017.

  1. KramE

    KramE Member

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    Hello all,

    I recently purchased an E3D and I am having a specific oozing problem with printing PETG (I have not printed any other kind of PETG or filament with this hotend). During internal travel moves of an individual piece, I am getting oozing regardless of what settings I adjust in Cura. At baseline in version 3.0.X, retraction is not usually performed during these moves.

    [​IMG]20171211_141844 by Mark E, on Flickr

    [​IMG]2017-12-13_02-30-16 by Mark E, on Flickr

    [​IMG]20171211_163935 by Mark E, on Flickr

    As you can imagine, the stringing/nozzle build up/boogering causes varying degrees of trouble during the print.

    Anet A8
    e3D v6 1.75mm Bowden @ 19.5" long
    Skynet 2.3 Bug Fix
    Inland PETG Translucent Green
    Cura 3.0.X

    [​IMG]20171213_070843 by Mark E, on Flickr


    Here is what I have tried:

    I printed at 5 degree intervals 220-250 (max recommended). 225 is the minimum temperature I could use to achieve adhesion. Identical stringing/oozing between entire temperature range.

    With each temperature change I adjusted:
    *The Z offset over a 0.5mm range; from basically scraping the glass to air printing
    *Extrusion Percentage 100%-80%; Full bore to under extruding to the point that the shell and infill do not completely mesh.
    *Build Plate Temperature from unheated to 80 degrees
    *I tried both painters tape and glass plain, with purple glue stick and hair spray
    *Activated Retraction Extra Prime Amount which sounds like it's supposed to help with this very problem, but the info on this setting is scant. I tried from 0.04mm3 to 2.0mm3
    *Travel speed 100mm/s to 250mm/s
    *Print Speed 30mm/s to 60mm/s
    *Fan speed from 30% to 100%
    *Dissembled and reassembled the E3D - Yes, the nozzle was tightened under heat
    *Reran PID autotune
    *Measured filament diameter and found to be consistently at 1.70mm and adjusted in Cura

    I am confident that my Z axis and bed are level and have literally printed over a 100 variations over the last two weeks. Despite every change I made in Cura, there was literally no change in the oozing and stringing. The only variation is how it presented either as a nice neat string, a whisker, or blobs and boogers.

    What am I missing? What more information can I give? What else can I try? Is my bowden tube too short/long/oriented poorly? Should I relocate my extruder? Buy fairy dust and wish on a star?

    Thank you for reading this,

    Mark
     
  2. Old_Tafr

    Old_Tafr Well-Known Member

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    Not an answer to your problems I'm afraid, more a note that with a different setup and different filament I seem to be in the same boat.

    BigBox printer, Volcano nozzle 0.8 mm on V6 heat sink using Edge. Whatever settings I use I can't get it to stop printing an extra pass on the first layer, so I get a big ridge say every ten passes. I'm using Simplify3D having given up with slic3r.

    The problem is changing parameters and keeping a record of what you used last time and the time before.

    Saving settings in slic3r is a nightmare, it's easier in S3D by using the "Save Factory File"

    The difficulty is the comparison from one trial to the next, what is needed is maybe a way to feed the gcode (which in slic3r has a list of all the settings at the top) into a spreadsheet and an automated way to highlight what changed from one print attempt to the next.

    I suspect like me that the possibility is either...

    A. What is being attempted isn't possible due to limitations in the printer itself.

    B. The model being printed and the nozzle size are not compatible (e.g. a 1.2 mm wall with a 0.8 mm nozzle)

    C. There is one setting that we are not adjusting which is the fix all along, so changing lots of other things makes no difference at all.

    D. A lack of understanding of what each slicer setting does. Simplify3D is difficult in this respect as sometimes the opposite happens

    e.g. I reducing the 1st layer, layer height percentage, expecting this to stop excessive filament oozing everywhere. WRONG... as the volume of filament does not change (e.g. extraction multiplier is the same ) then the same amount of filament is being forced into a lower layer, so it both spreads out ( in a single pass like a single circle) or oozes everywhere on multiple passes. Answer INCREASE the 1st layer layer height.

    A table of each setting and it's effect on other settings (or not) would be handy here, a little like services in Windows and dependencies.
     
  3. dc42

    dc42 Well-Known Member

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    @KramE, have you tried adjusting the retraction settings and the pressure advance? I don't see those in your list. It looks like you have a long Bowden tube, so retraction and pressure advance will both be important to avoid oozing.
     
  4. KramE

    KramE Member

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    I have not played with retraction distance/speed too much because I have printed stringing tests with very little issue. In my case, retraction is not being performed when the oozing is happening. After printing the exterior wall the nozzle moves to print the wall of the screw hole and it is during those moves that the oozing fouls the print.

    I tried to activate retraction during those specific moves by turning on retraction extra prime amount. But after further review, that setting is the exact opposite of what I want.

    I have not heard of pressure advance. Is it a setting? Calibration? Side effect Hysteresis? A Concept to account for?

    Thank you,

    Mark

    Edit: Last night I reoriented the bowden tube downward with no change and shortened the tube by about an inch. No changes noticed at the time.

    This morning when I was trying again to find the lowest printable temperature, the filament would slip in the extruder once or more all the way up to 245. So I think I cut the tube too short. More has been ordered.

    Also of note, I have also tried z hop, but with no effect.
     
    #4 KramE, Dec 14, 2017
    Last edited: Dec 14, 2017
  5. dc42

    dc42 Well-Known Member

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    It sounds like you have a setting "only retract when crossing perimeters" or similar enabled in your slicer settings. I suggest you find that setting and disable it.

    Pressure advance is a feature that helps compensate for the elasticity of the filament in the Bowden tube. It has been in Sailfish firmware for more than 3 years, RepRapFirmware for 3 years, and Marlin for about a year. If your firmware doesn't support pressure advance, the slicer setting "coast to end" is a poor substitute for it, but better than nothing.
     
  6. KramE

    KramE Member

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    Thank. You. So. Much. For giving me a direction to chase.
     
  7. KramE

    KramE Member

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    So in case anyone stumbles across this thread, my particular problem revolved around known bug in Cura 3.1. It prevents retractions during internal moves. The solution is to turn off "combing" under the travel settings.

    Thank you everyone for your help!
     
    #7 KramE, Dec 20, 2017
    Last edited: Dec 20, 2017
    mbuc likes this.

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