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Thread: PETG or PLA

  1. #1
    Student
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    PETG or PLA

    I have been printing everything in PLA but the objects are mainly used inside or if outdoors they do not stay there. I need to print a part for my garden tractor trailer which sits outdoors 24/7 so it's always exposed to the elements. Strength is also an issue, which can be taken care of with infill I will assume. Never printed with PETG so I realize there will be a tuning curve to go through.

    Which filament will be better for this purpose? No enclosure or exhaust fan so I would like to stay away from ABS too.

    Thanks

  2. #2
    My unopened spool of eSun PETG is sitting next to me.. I have the same needs as you but have not gotten the time to try it out.. There is a good article on the eSun sight which I plan to follow.. https://www.xyzfabs.com/forums/topic...lack-filament/
    I believe this was originally posted on the the MakerGear forum a few year ago.. I had recommendations from 2 guys on the MakerGear forum when I asked about PETG .. one for the eSun and one for MakerGeekes.. I had already bought the eSun but will try the other next time..
    Good luck and please post back here with what you buy and now it works for you.

  3. #3
    Student Modelworks's Avatar
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    PETG is my go to filament now. PETG doesn't crack and tends to bend instead of breaking.
    I can take pliers and twist parts I make without breaking them, they deform of course but do not break.
    It is not as hard as PLA but pretty close. I use it outdoors, on my CNC for clamps and parts, printer, etc.

    I tried printing at higher temps 230C + and found it to be brittle then started using 216C with a 50-70C bed temp and good cooling for bridges and it works great.
    I chose the temp based on starting at the point where it just starts to flow out the nozzle easily and then increasing it a few degrees until the layers were strong enough to not de-laminate.
    Too hot it was a stringy mess and brittle and too cold it jams the nozzle. Cooling it quickly made a difference in strength as well.

    I did some research on why PETG temps may be more critical than other filaments.
    PET is the plastic used in soda bottles. It is resistant to water, alcohol and most solvents. The problem with using it for printing is it has a high melting temp so to lower the temp they add glycol. The process of adding the glycol happens at about 250C , not much higher than extruding temp which may be the issue some have with breaking of filament.
    The original product is from the 1960's and was known as KODAR created by eastman kodak.
    From some patent docs:

    KODAR PETG 6763 material can be injection-molded at temperatures above 390° F.. However, at temperatures of 420° F. and above, the material degrades, making it brittle. This results in a difficult injection-molding process, since the molding range is quite narrow. Also, at the low end of the molding range or below, the plastic becomes brittle because of molded-in stress.


    Apparently over the years different formulations have been made to make the temperature window wider , so you need to test temperatures with your brand of filament. The window is narrow for what is good or bad but once you find the right temp PETG is a great filament. If it cracks you are too hot and if layers separate you are too cold.

  4. #4
    Great info!! Thanks so much for posting that!
    What do you use on the bed? I use polyimide tape on my build plate.. just wondering if the PETG will release. Freezing PLA with can air propellant works great but with PETG I would guess it will not due to it temperature stability? Does glue stick work with PETG? I like the idea of just running the plate under water removing the glue and part..
    Last edited by airscapes; 06-03-2018 at 08:09 AM.

  5. #5
    Student Modelworks's Avatar
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    I use aquanet hair spray on cheap picture frame glass. It releases about like PLA.
    I tried other things but the glass is $1 and I just spray it, let it dry , clamp the glass to bed and print. You can release it with cold or water.
    It doesn't seem to shrink or have problems warping like ABS.

  6. #6
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    Thanks guys for the info. Ordered some Soultech PETG, will be here tomorrow. I think the Temp range for it is listed as 190-220, this could have been a misprint on Amazon. I'll know better when it gets here.

    I print PLA on a glass bed with a bed temp of 60c normally I don't use anything on the glass, I wipe it good with rubbing alcohol to clean the glass between prints. About every 3 prints I take it and wash it with soap. If I have something that doesn't want to stick I use some glue stick on the glass. Been trying to stay away from the hair spray because of the overspray.

    When my PETG gets here tomorrow I will print a temp tower and see how it comes out.

  7. #7
    Super Moderator curious aardvark's Avatar
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    Yep, if you can pet-g to behave, it's really impressive stuff.

    Pla is absolutely fine for outdoor stuff. So if you struggle with the pet-g, don't sweat it, just use pla :-)

  8. #8
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    From Solutech web site:
    We understand that each desktop 3D printer has its own unique characteristics, which is why you might need to adjust your temperature settings a bit to get the best results. To obtain optimal results for your prints you need to take certain factors into account like your 3D printer’s nozzle diameter, your printing speed settings, and layer height. Every printer is different, hence for each material/printer you should ensure to take notes of what works and what doesn’t work for it.
    Your print bed MUST BE LEVEL & CLEAN. You can simply make use of acetone and a towel (lint free) to clean your surface and make sure it is free from oils and dirt before printing.
    If your printer is equipped with a heated print bed, make sure it is turned-on, especially for ABS.


    PETG 200°C - 220°C
    Set your print bed temperature to approximately 85°C - 100°C.
    Sticks well to Polyimide/Kapton tape, PET tape, Blue tape.

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