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PETG Black Spots

Discussion in 'General Questions' started by Carter Goff, Dec 23, 2015.

  1. Carter Goff

    Carter Goff New Member

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    So, I've been doing about 95% of my 3D printing with PETG filament lately. It's been working great, except for one problem. Occasionally I'll get black spots on printed objects. Sometimes they're flat and sometimes they poke out. I'm thinking maybe it's a temperature problem, but I don't know what temperature would fix it. Has anybody found something that will fix this?
     

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    #1 Carter Goff, Dec 23, 2015
  2. KTMDirtFace

    KTMDirtFace Well-Known Member

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    I get that sometimes too, its usually filament that builds up on the nozzle then burns/turns black and eventually comes off in the print somewhere. I'm not sure how to fix it it seems to be from the PETG Oozing more than other filaments. WhereWaldo on here said i should try adjusting the extrusion multiple but i have not tried that yet. I upped my retraction a bit and it helped some but it still happens.
     
    #2 KTMDirtFace, Dec 23, 2015
  3. WheresWaldo

    WheresWaldo Volunteer ( ͠° ͟ʖ ͡°)
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    Oozing is all about backpressure, and you simply can't retract enough or fast enough to prevent it entirely, especially with the way all our nozzles are designed. This is less of a factor with the much longer nozzle of the E3D Volcano. If you squirt out too much filament PETG has a tendency to curl up and attach itself to the outside of the nozzle, this is what burns and then drops off somewhere in your print. If you are using S3D you can play a bit with the COAST feature which looks ahead at your moves and shuts off the extruder before you reach the end of whatever section you are currently printing. It was specifically designed to eliminate oozing. I do not know of any other slicer that currently has this type of setting.
     
    #3 WheresWaldo, Dec 23, 2015
  4. Mike Kelly

    Mike Kelly Volunteer

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    Yup I got that black burnt part as well. Increasing infill so you have less overhangs tends to help. PETg wants to stick to the nozzle
     
    #4 Mike Kelly, Jan 4, 2016

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