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PET G Globs?

Discussion in 'Printing Filament' started by Ben R, Feb 7, 2015.

  1. Ben R

    Ben R Active Member

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    I have been printing with ESUN PET G. It works great, but I occasionally get globs. They can ruin a print.
    It looks like the PET likes to stick to the nozzle a bit, then eventually that glob sticks to the print and peels off and hardens.
    I seem to have the proper layer thickness, it lays down really nice, but still.

    It oozes like mad. It may well be the ooze is getting pushed back onto the nozzle when it starts a print after a move. Any ideas on best ways to prevent PETG ooze/globs?
     
    #1 Ben R, Feb 7, 2015
    Last edited by a moderator: Feb 7, 2015
  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    PET is one of the most finicky, problematic filaments I have used... (and I still have most of two spools).
    When it works it is awesome, but getting the temperatures right is difficult.
    I've had it lay beautiful layers for a dozen layers and then go straight to crap :)

    You need to do it with actual test prints (small ones) since my standard approach of just testing the extruded filament does not work with this stuff. Also, it goes through a 'band' of temperature where it gets 'globby' then it smooths out so don't just assume it is too hot. It might actually need more heat.
     
    #2 mark tomlinson, Feb 7, 2015
  3. Ben R

    Ben R Active Member

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    Yea.. I reduced my extrusion a few percent and it stopped globbing all together.. Then... the dreaded non adhered layer due to underextrusion.
    I find the big problem is the bottom fill.. in particular the first layer. Top fill is less problematic, but if you're not perfect it can get globby.
    Wouldn't be such a big deal if it didn't turn brown/black after cooking a while.

    any particular test prints you'd suggest to target its issues?
     
    #3 Ben R, Feb 7, 2015
  4. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Something small (I attached one) that actually has some complexity.
    This one is a great test print that only takes 30 minutes or less to do and is complex enough to find issues.
     

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    #4 mark tomlinson, Feb 7, 2015
  5. Ben R

    Ben R Active Member

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    Rather than follow good advise... I started a new print.

    Following your suggestion, rather than turning it down to avoid globs.. I cranked it. Package say 230-250.. I'm doing 249. So far no problems. I also reduced the first layer extrusion a tiny bit... made it glass smooth and I can read the print on the platten :cool:through the bottom of the print.
    We'll see.. printing the 20mm extruder fan .. clear enough and maybe big enough where I can put my extruder light inside it.

    But I will print some tests
    I think that first layer (and several subsequent layers depending) are pretty key to globbing.
     
    #5 Ben R, Feb 7, 2015
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  6. Ben R

    Ben R Active Member

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    Several prints in, reducing the extrusion amount a couple percent vs my ABS settings seems to do a lot. I am getting some tiny brown dots in a print I'm doing currently that has many retractions in it, but an all night print on something smooth went without a single inclusion.
    Its gotta be the strings.
    so far.. hot + low end of good extrusion seems to work best.
    Probably a matter of fine tuning. I'm wondering if some speed adjustments would work to help.

    Slow speed, I get a blob on the nozzle, high speed I get strings. A blob looks horrible, but they flake off. the strings are light enough to stick to the nozzle/get wrapped on it.
    I hate to go slow... but, my overnight prints (usually slow, since I don't need to hurry a 4 hour print when I'll be away for 8 hours), do well; in my limited data set.
     
    #6 Ben R, Feb 8, 2015

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