Pressure Advance + Slic3r PE retractions et al ... Funky results



  • Trying to get my print quality fixed up. In general now I get pretty decent prints, but Im just getting going with PetG. Ive run a temp tower and determined 240 or 235 are the material in question's best temps.

    I was having pretty significant issue with print quality with PetG but once I scaled waay back on the retraction and added De-Retraction - things improved with this material significantly. I ran some tests using CUBES - small ones as per one of the advanced users here in Duet forums alluded to. I got the stls off Matterhackers site/thingieverse. Those came out pretty nice. My cubes corner bulge on the z seam / layer change, was greatly dimished - very few - like 4 random strings no blobs and over- all pretty good looking output at 40 and 80 mms.

    I then went for the Cones of String Death and am getting funky results. Im at a loss as to what to mod ... I think I need faster retraction, slower De-Retracton - and perhaps a HAIR more "Pressure Advance"

    Print Speed for this test was 20mms as per thingi creator notes
    Press Adv - .065
    Retraction- 1.0mm / 45 mms
    De-retraction - 20 mms
    Extrusion Multiplier - 1.00 / 100%
    Nozzle Temps 240*C / Bed 70C - Buildtak
    Extruder e-steps tweeked and retuned today as well. Pretty spot on

    What is happening from me spying on the entire print thru a magnifying glass as it went - is - on the thicker areas [ lower] of the pillars/cones - the nozzle is stringing on the way out or off the part as it moves to the next.

    As the cones get taller and pointier - the nozzle is depositing material early - hence those branch looking Blobs. My thoughts are faster retract speed - not more distance, and use more Pressure Advance adjustment, and then slow down the re pressure [ de retraction ] to like 15mms

    These branch blobs are new to me - as is most of this - not sure what direction and steps to take to resolve. Your insights and guidance MUCH Appreciated

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  • I concur with your thoughts on faster retraction and slower unretraction, as that would echo my findings with PETG. I tend to use very fast retractions in general. Pretty much as fast as it will go. I also find pressure advance helps with stringing with PETG.

    Another thing I noticed was that if the first layer was too close to the bed the plastic would stick to the nozzle and would cause stringing with the rest of the print no matter what. I think this is particularly bad for me since I use a hardened steel nozzle that PETG really likes to stick to. 0.4 layer height for the first layer at 25mm/s gave perfect first layers and the rest of the print could proceed at 100mm/s no problem with very low part cooling fan speed.



  • @phaedrux said in Pressure Advance + Slic3r PE retractions et al ... Funky results:

    I concur with your thoughts on faster retraction and slower unretraction, as that would echo my findings with PETG. I tend to use very fast retractions in general. Pretty much as fast as it will go. I also find pressure advance helps with stringing with PETG.

    Another thing I noticed was that if the first layer was too close to the bed the plastic would stick to the nozzle and would cause stringing with the rest of the print no matter what. I think this is particularly bad for me since I use a hardened steel nozzle that PETG really likes to stick to. 0.4 layer height for the first layer at 25mm/s gave perfect first layers and the rest of the print could proceed at 100mm/s no problem with very low part cooling fan speed.

    Great feedback ... I also concur with your first layer sentiments. i first tried glue stick on Buildtak ... but I couldnt make small circles with a .5 nozz reliably at most any layer height - I was a baby steppin mofo ... But a switch to just windex on Buildtak has been dreamy. Im running Petg about .08 higher than normal.

    Im putting acetone on a qtip and sprucing up the Nozz between prints. Dude over at sublime layers - talks about polishing the nozzles and getting edges and burs off to aid in lubricity [ my term for it not his ] and lessening hairy petg etc from catching hold - I may do that on nozz replacement - Im gong back to a .4 soon I think.

    I'll up the retract speed 10 mms and decrease re-retract 5 mms and add some more Pressure Advance - not sure how much Press Adv to add in - I'l try .08 from current .065 and see how she goes. I may also try a run at 235 ... or when it gets to the tips kick it down 5C.

    Appreciate your insights... if you think I should increase my numbers even more - help save a couple hrs of print tests LOL ... Also I was running this last test aweful slow - 20mms - should I be running these tests at typical desired sprint speeds ?



  • I've been keeping my eye out for an old leather key chain I'm sure is kicking around here somewhere so I can try giving the nozzle a buff. Not sure if it would make much of a difference for the hardened steel. It still looks brand new. I just use needle nose pliers to grab any ooze before the print starts and I do a short prime line before the print starts to remove anything in case I forget.

    I'm using a Titan Aero so my specific values might not be relevant to you but here's my firmware retraction settings for PETG

    M207 S0.8 R-0.005 F8000 T1200 Z0.0

    Jerk and acceleration values for the extruder are just very high values. It sounds very snappy.

    For pressure advance I use 0.8 printing at around 80-100mm/s

    I also use PID values tuned for 250.

    I add all those specifics to the filament gcode section in slicEr.

    One other detail I forgot to mention was that I set the line width in the advance section to be equal to nozzle width for petg. That seemed to help with stringing as well.

    For bed adhesion I use glue stick on PEI. First layer 80/250 and 70/245 after that. 20-25mm/s and 200 acceleration and even the smallest circles and details stick fine. After the print cools I use a flexible box cutter blade to slip under the print and it pops off. Then a good spray of 99% isopropyl to refresh the glue stick and it's good to go.

    If you start the print at 20mm/s you can use the speed multiplier to increase it by 10% every few mm of height until it start to look dicey. Then you can go back to the slicer profiles and add however many percent to the speeds.



  • Great tips - all around - the nozz width - line width is a great one to try - makes perfect sense too. Thank you very much ... Its like an Indy Car - sum of a a lot of little adjustments all over.

    .5 nozz and Im at .55 width. I'll bring it down to .5 too.

    Just ran that 4 cone spire torture test again ... [ wish Slic3r let ya alter temps at layer heights ] and this time ...

    1 mm retraction / 55 mms
    10 mms re-retraction
    .08 Pressure advance [ direct drive ] Bondtech Prusa MK3
    1.0 extrusion multiplier
    1.75 filament

    240c for the majority of the print but when the strings started to show - dropped it to 235 - and then again at the tips at 230C.

    I still got strings - bit not nearly as bad and they started much farther up the spires. Also did get some branch like blobs at the very tip tops - waaay better tho than the last one - pictured above .

    Im pretty pleased atm with it. I think I might consider upping the retract another 5 mms and making sure my Jerk/Accel for E are up high enough to use it ... Thin it makes any sense to put re-retract down to 5 mms ?



  • Curious what brand PETG you are using. I have used both hatchbox and ESUN, PETG wise, the Hatchbox (gold, white and orange) prints much cleaner for me. I have also switches from a brass nozzle to the copper tinned nozzle and had noticeable improvments.



  • The branch like features are caused by an initial small blob of filament at the edge of the print. Then the next time the print head passes over this initial blob, if there is a blob of filament on the end of the nozzle, it gets "wiped off" and deposited on top of the first one. So the branch continues to grow with each pas of the nozzle. In my experience, a bit more retraction usually fixes it.

    As someone else pointed out, there s PET-G and there is PET-G. Some brands are more prone to stringy behaviour than others.



  • I should have mentioned that I use E3D SpoolWorks EDGE PETG mostly. It's a little on the pricey side, but the results have always been terrific.



  • When my PETG quality made a major leap it was when I realized that my first layer being to close to the bed was causing the blobs I was seeing in my 50th layer. Once I gave it a little more room I notices my nozzle was not rolling boogers in the wide open spaces at higher altitudes.



  • @jackatom74 said in Pressure Advance + Slic3r PE retractions et al ... Funky results:

    When my PETG quality made a major leap it was when I realized that my first layer being to close to the bed was causing the blobs I was seeing in my 50th layer. Once I gave it a little more room I notices my nozzle was not rolling boogers in the wide open spaces at higher altitudes.

    Good info ... i feel like my 1st layers are high off the bed if anything atm ... i seem to have to run a wide [ 8 loops ] skirt to get Z dialed in w/ babystepping - and I too found petg on buildtak especially - likes to start out a bit higher than i'd ever run PLA.



  • I'd like to add an oddity happened last night on test print ... I altered the Slic3r PE profile settings to the numbers discussed above [ except for de-retraction was run at 15 mms vs. 10mms ] - but I had forgotten to mod the Press Adv in config.g prior to running the print start. But ... NP - sent a nifty command via the gcode console in DWS to change the Press Adv to .08 .... All cool ... except ...

    The oddity was - my Y axis motor on non printing rapids, and faster printing moves - started whining - well making a noise Ive never heard before - ever. I tried increasing the speeds to see if that went away - nope. I tried slowing things down too - and that did change it and it went away. However; when you use the DWC interface for speed modifications, I suspect that also alters - ALL stepper moves, so I put speed back to 100% and left it till the top of the tips



  • @jackatom74

    Im using Matterhackers [ they are just down the street from me ] 1.75 Aqua PetG Pro



  • @deckingman said in Pressure Advance + Slic3r PE retractions et al ... Funky results:

    The branch like features are caused by an initial small blob of filament at the edge of the print. Then the next time the print head passes over this initial blob, if there is a blob of filament on the end of the nozzle, it gets "wiped off" and deposited on top of the first one. So the branch continues to grow with each pas of the nozzle. In my experience, a bit more retraction usually fixes it.

    As someone else pointed out, there s PET-G and there is PET-G. Some brands are more prone to stringy behaviour than others.

    Thanks for that ... Matterhackers PetG Pro - Aqua 1.75

    Do you feel as if that blob branch issue would be best solved by MORE retraction or higher Press Adv ?

    Going by what fellow Duet user DHackney of sublime layers advises 1.0mm retraction [ should be plenty ]. Obviously not a hard fast rule but ... too hot perhaps / temps ?



  • Another question I had about these print tests ... Should I have the expectation to get this 100% blob free - strings arent - to me the end of the world - surely Id prefer to never see one, but - is it reasonable expectation with a Duet wifi / E3d v6 - good bed and accurate frame/machine to hit this VERY near perfect ?



  • It would help to know a bit more about your extruder and printer, but I don't see why string free prints couldn't be attainable, unless of course it's just the nature of the filament.

    Try increasing the retraction by 0.05 mm during a print every few mm of height until the strings stop or you get an uncomfortablly long retraction, which for a Titan V6 all metal combo could be up to 2mm.

    You can live adjust the temperature during the print as well. 5c at a time through the range of whatever the manufacturer recommends. Some like it hot, others not.

    For pressure advance I look to see how much of a blob the end of a solid infill line looks like and increase it slowly until the end of the line seems to match the width of the line.

    It would also help to do a test with pressure advance to see if it's actually helping or hindering.

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    I dunno if it's perfect but it's pretty decent. Any strings are tiny wisps.



  • @phaedrux said in Pressure Advance + Slic3r PE retractions et al ... Funky results:

    It would help to know a bit more about your extruder and printer, but I don't see why string free prints couldn't be attainable, unless of course it's just the nature of the filament.

    Try increasing the retraction by 0.05 mm during a print every few mm of height until the strings stop or you get an uncomfortablly long retraction, which for a Titan V6 all metal combo could be up to 2mm.

    You can live adjust the temperature during the print as well. 5c at a time through the range of whatever the manufacturer recommends. Some like it hot, others not.

    For pressure advance I look to see how much of a blob the end of a solid infill line looks like and increase it slowly until the end of the line seems to match the width of the line.

    It would also help to do a test with pressure advance to see if it's actually helping or hindering.

    I dunno if it's perfect but it's pretty decent. Any strings are tiny wisps.

    Thats a sexy benchy sir ... still yet to print one of those - only because everybody does. Maybe its time ...

    Im not using firmware retraction - im slicing all those settings into the gcode, except Press Adv. Can I still send gcodes from the DWC for retraction settings that will override the sliced values ? Im not sure I understand how that works ...

    On your solid infill line end test ... so Im clear [ and many thanks for all your help here btw ] - youre talking about like a single layer or more of 100% infil like rectilinear - where it melts over the interior perimeter line ?

    P.S. - you remember your print speeds for that benchy ? 😉



  • To use firmware retraction with Slic3r PE it's as easy as checking the box in printer settings.
    It's a little trickier in Cura. There is a plugin that will let you toggle it. https://community.ultimaker.com/topic/22743-printer-settings-plugin/

    Once you have it enabled you can then use the G-code console to modify the values on the fly. Once you find the values you like you can put them in config.g as defaults or add them to the start code areas in Slic3r for a specific filament.

    I think that Benchy was 100mm/s, 0.2 layers. 400 accel, 60 jerk.



  • Before I get excoriated on this - I set these - knowing mostly nothing about what they should be... Duet was my first ever used printer/board. I suspect Im a good bit OFF on these settings too.

    ;---------------------------
    ; Drives
    ;---------------------------
    M569 P0 S0 ; Drive 0 goes reverse [ X Axis ] [ S0 = Rev / S1 = FWD ]
    M569 P1 S0 ; Drive 1 goes reverse [ Y Axis ]
    M569 P2 S0 ; Drive 2 goes reverse [ Z Axis ]
    M569 P3 S1 ; Drive 3 goes forward [ E0 ]
    M350 X16 Y16 Z16 E16 I1 ; Configure microstepping with interpolation
    M92 X100.30 Y100.250 Z1600 E140.64 ; Set steps per mm
    M566 X900 Y900 Z25 E250 ; [ Jerk Settings ] Set maximum instantaneous speed changes (mm/min)
    M201 X500 Y500 Z280 E250 ; Set accelerations (mm/s^2)
    M572 D0 S0.080 ; Set Pressure Advance [ need to check Jerk and Accel Settings to properly coincide here ]
    M203 X6000 Y6000 Z280 E1200 ; Set maximum speeds (mm/min)
    M906 X1600 Y1600 Z1600 E1600 I30 ; Set motor currents (mA) and motor idle "power saving" decrease factor as percentage [ I30=30% ]
    M84 S10 ; Set idle timeout

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  • Those look like pretty good starting points to me.

    Do you notice stringing printing other things? Those towers are designed to be a worst case scenario afterall.



  • The other thing about using firmware retraction is that you can change it on the fly during the print.


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