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PETg trouble on small print sections.

Discussion in 'Printing Filament' started by Justin Dembski, Mar 4, 2020.

  1. Justin Dembski

    Justin Dembski New Member

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    Hi, so I've been trying to work with petg for about a month now and have cleared many of the hurdles. I get good bed adhesion and minimal stringing. I'm finding that any longer print portions of my print turn out quite decently. Once I get to a layer with a small print distance is where I start to see problems.
    The surface turns to crap from these points on up. I watched the print when it gets to that point and noticed its like the filament doesn't get forcefully extruded right at the beginning of the print move, causing it to not sick at the beginning of the small print move and either curl up on the nozzle or stick on a later portion of the layer. It seems to not start actually extruding until around a couple mm into the move. This causes subsequent layer to have the nozzle just smush around material in the printing area. The best luck I've had is crank my speed way down like around 10mm/s with really low acceleration, like 300mm/s. But even this doesn't not produce ideal results. I've found less retraction helps a bit as well.

    I feel like I've tried almost every combination I can think of:

    • Nozzle between 220-250 (found 235 to be decent)
    • Layer height between 0.2 and 0.3mm
    • retraction between None, 2mm up to 7mm (On bowden setup so I heard longer better). Current speed at 25mm/s but previously 60 mm/s. Haven't messed with extra retraction prime amount much yet.
    • Speed between 5mm/s and 40 mm/s (have had best luck with 10mm/s so far, but feel with how slow that is it may be keeping the filament too melty where it's laying down.
    • Acceleration between 200-1000mm/s^2
    • Travel speed 120mm/s, Travel acceleration 4000mm/s^2
    • Fan at 100% after 3rd layer. Though with my newer hotend mount the fan duct doesn't point right at the tip anymore.
    • Keep bed at 95C like I said no issues with adhesion.
    • Small (3mm) holes seem to print just fine.

    My setup is a ROBO3d R1 with z axis upgrades, titan clone extruder, e3dv6 all metal hotend, Bowden setup about 1 foot and a half, eSun White petg, slicing with Cura.

    For reference here is the part I've been printing. Consistently having issues when it gets to the layer with the small section of the BL touch mount.
    https://www.thingiverse.com/thing:1904552

    I also confirmed the same results trying to print the classic retraction test spikes print. I will post pictures as well when I get home tonight.
     
  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Have you set a minimum time per layer? That allows the previous layer put down to cool before a new one is put down over it.
    Some filaments are OK with hot plastic going down on hot plastic, but PTE(g) is not. In general it is a good idea to just print slow enough for it to cool regardless.

    I don't use Cura, but the docs I found indicate this is where you set that: https://ultimaker.com/en/resources/52674-cooling
     
  3. Justin Dembski

    Justin Dembski New Member

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    Ah I had remembered that being a setting back when I had used MatterControl, but hadn't seen it in Cura. I'll give it another look when I get home from work in a few hours, thanks.
     
  4. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    I'd suggest a minimum layer time of at least 30 seconds, experiment to find what works best, but that will solve the smaller layers getting melted.
     
    Geof likes this.
  5. DGGT6

    DGGT6 New Member

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    Hello Justin, I hope you got your PETG printing working.
    I am looking to install a 3d touch on my Robo R1 and you seem to be about the only one on the forums to have done so.
    Would you mind sharing how you connected it to the ramps board and what you did about the original Robo Z switches.

    Many thanks,
    Doug
     
  6. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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