PETG advice bad top layers



  • petg.jpg

    This is my first attempt at petg, as picture shows not going to good, i don't seem to have any warping or adhesion problems, seem like the top layers are not meshing together and the holes are also not closed on edges, the part is strong i can't break it..

    I have tried temps from 230 to 260, retracts for 1 to 7, and this print i set the speed to 30 mm/s temp 250
    tried cooling fan off and on..

    I have found any prints below 240 start getting brittle and break easy..

    Any suggestions

    Gary



  • Have you set your esteps correctly? This is a big deal, and often people seem to want to do it via the "extrusion multiplier" in their slicer. If you are not feeding the right amount of plastic, you will get a sub par result. EM is for fine tuning after that.

    Try an extrusion test of 100mm @ 5mm/sec in the extrusion section (I'm assuming you're using duet) through a clean nozzle at the intended print temp. That is the foundation of a good print, and you can tweak it from there in the slicer.

    250 seems a bit hot....I print PETG very nicely at 240/230, but it does change a lot between brands.

    Is your setup a direct drive or bowden? Please tell us what you are using there.

    PETG is tricky. I've really struggled with a load of rolls I got cheap recently, but have cracked it now and it's printing beautifully. Keep trying, you'll get it.



  • I did set the esteps for 100mm extrusion but i did it cold and not with the filament in the hotend i will try it hot and see how it go's.
    its a bowden style with around 400 to 500 mm tube
    here's a pic about half way thought the print i don't think it looks to bad?

    petg1.jpg

    Gary



  • @gorf26 said in PETG advice bad top layers:

    its a bowden style with around 400 to 500 mm tube

    That is your problem right there! You need correct pressure advance set up for your filament, nozzle and nozzle temperature in order to correct for the long bowden tube.
    I agree on 240 for nozzle temperature. As mentioned, estep needs to be set with the filament going through a hot nozzle. In theory, it should be adjusted for temperature, material and nozzle size but I find that I do not change things between different nozzles/temperature/materials.
    You will need to adjust retraction once you set up pressure advance.



  • Thanks will work on that i did end up last night getting a decent print made a lot of slice changes in S3D, then ran into a problem with the roll of petg it snapped while printing, and from what i can tell sections of the roll are fused together and snap easy brittle, so i took a pic and emailed to where i purchased it to see what they will do, only roll of petg i have so testing will be on hold till i get it replaced, don't want to waste anymore time with this roll its snapped twice half way though a print..

    but as far as the print went top layer looked solid, also the holes were good, only thing i still could see was slight stringing was going to drop the temp a little and try it again but will have to wait..

    Thanks for you help, may continue this after i get a new roll of petg

    Gary



  • PETG also likes to absorb water from the air, which makes it stringy/brittle. I keep mine in a sealed box with silica dessicant and only take it out when I'm going to print it. Depending on conditions, I start to notice a difference in performance after it's been out for about a week. Putting it back in the drybox for a few days usually perks it up again.



  • Also, PETG is normally stringy anyway (compared to PLA anyway)



  • Thanks

    I got it from 3d universe, and i do have to say they seem real good, i sent a picture of the roll stuck together and they already sent me a refund.. do you have a commendations as to a good brand of petg ?.

    Gary



  • @gorf26 Im in the US, and my top two favorite PETG brands are Atomic and Prusament. I’ve also had good luck with SnoLabs.


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