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Melting PLA print when outside in sun

Discussion in 'Off Topic' started by Eric Viglotti, Aug 13, 2017.

  1. Eric Viglotti

    Eric Viglotti Member

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    Hello,

    I have been printing now for awhile and I noticed that my PLA prints do great indoors, but when I prime them and get them ready to keep for projects outdoors, they start warping if the walls are not really thick, per attached. Is this something where PLA just naturally does this because it has such a low melt point? Would ABS do any better? Or alternatively, has anyone had any success with putting a 2 part epoxy "shell" on top like XTC-3D or a wood epoxy?

    Thanks!
     

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  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    The glass transition temperature for a filament is the point at which it starts to go "plastic" and deform.
    Approximate numbers are :

    PLA - 60 c
    PETG - 80 c
    Alloy 910 - 90c
    ABS - 100 c
    ASA - 105 c
    BluPrint - 110 c
    Polycarbonate - 150 c

    Choose your material appropriately :)

    Obviously to some extent the thickness of the model matters, but as far as basic material properties that will get you started in the right direction. For stuff outdoors I would normally go with (at least) Alloy 910 and for stuff in cars I would use BluPrint (only because it is so much easier to print than PolyCarb). ABS would work in a hot car too, but it is much more finicky than BluPrint.

    When in doubt look at the manufacturers specs for the filament in question. Some nylons are pretty high on the transition temperatures too.
     
    #2 mark tomlinson, Aug 13, 2017
    Last edited: Aug 14, 2017
  3. Kilrah

    Kilrah Well-Known Member

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    Perfectly normal for PLA indeed, especially darker colors that naturally absorb more heat.
     
  4. Eric Viglotti

    Eric Viglotti Member

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    Thanks so much. I tend to lean towards PETG since it's still a higher glass transition temp, is odorless and seems still relatively inexpensive. My thought is that since my primer is dark (per this picture), but my end color is a gloss white paint, I might not have as much heat absorption as this picture, but that is a great point as I was thinking much the same.

    Has anyone had any issues printing either PETG or Alloy 910 with a R1+ or R2? I have never tried either.

    Also, any preferences on brand/product, preferably something I can find on Amazon?

    Thanks!
     
  5. Kilrah

    Kilrah Well-Known Member

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    Lots of PETG parts on my R2, everything great.
     
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  6. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    On the R1 series, the Alloy 910 prints much like PLA with the addition of some nominal bed heat. A little practice will help nail down the specifics temps that work for you.
     
  7. daniel871

    daniel871 Well-Known Member

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    PETG is the go-to middle-ground for better behavior outdoors, but if you really want some environmental resistance you should look into ASA filament.
     
  8. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    ASA typically has a glass transition of 105 C so not a bad compromise. I added it to the list :)
     
  9. daniel871

    daniel871 Well-Known Member

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    ASA is also UV-stable, so there is that aspect of it, too.
     
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  10. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Good point. We usually paint (or at a minimum clear coat) everything so we make sure that handles the UV protection for outdoor stuff (most of what we print for outdoor use is Alloy 910)
     
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  11. OutsourcedGuru

    OutsourcedGuru Active Member

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    I would also add to this that if that's a planter for carrots, for example, then you might want a food-safe plastic like ASA.
     
  12. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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  13. OutsourcedGuru

    OutsourcedGuru Active Member

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    Interesting read (and related smooth-on.com website).

    I'll add to this that even innocent-looking materials like aluminum foil aren't 100% food safe. Cover a plate of spaghetti with sauce with aluminum foil so that it touches the surface and put it in the refrigerator for a few days. The acid in the tomato paste will literally eat through the foil and deposit it onto the food.

    The FDA estimates that adult Americans consume, on average, a cumulative 11 mg of BPA per day, probably from the epoxy resin—lined cans. A CDC study found that 75% of the people they surveyed had measurable levels of seven different phthalates in their urine, possibly from heating food in plastic inside microwave ovens.
     
  14. Printed Solid

    Printed Solid Volunteer Admin
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    I'll add on to your second question:
    I did an experiment with XTC-3D on a vase print and then set that and an identical print on my car dashboard on a warm, late-spring day. Neither fared particularly well. So, I'd advise against that.

    I have noticed that woodfill and other filled PLAs seem to hold their structure much better when above Tg than plain PLA does, so maybe you would have better luck with that.
     
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  15. jwmueller

    jwmueller Active Member

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    I have done some in trailer and in car testing for months (in the Texas sun). 150F+

    PLA, HTPLA all warped on me, and could be hand deformed after taking them out of ~46C temps. (range of name brands, heat treated per directions) Some failed during the heat treat - but I never did try a more solid infill to see what that would change.

    MakerGeeks and ColorFabb PETG have been fine up to ~65C and after 6+ months the dimensions are the same as the day I put them in the heat for testing. Still flat when I put them on a good sheet of glass.

    Parts in question were printed with a .4mm nozzle, 3 perimeter walls, 20% infill. 0.08mm resolution, with 15 solid layers.
     
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  16. daniel871

    daniel871 Well-Known Member

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    MakerGeeks Raptor PLA is supposedly ridiculously tough after heat treating your printed object it by boiling it in a covered pot for a while and allowing it to cool off naturally after boiling.
     
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  17. jwmueller

    jwmueller Active Member

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    I have not had luck with it. However, I had not heard of the boiling trick so I will drag mine out an certainly test it again. I did leave one in the dishwasher for months along with a PETG version. The Raptor sucked in around all the infill so it had reverse bubbles for lack of a better description that were hexagon shaped.
     
  18. daniel871

    daniel871 Well-Known Member

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    Yeah, the high temp/dishwasher safe aspect does not come into play without first doing the heat-treating in boiling water for some reason.
     
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  19. Geof

    Geof Volunteer Moderator
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    Playing with that stuff now in hopes it works for some production parts we are doing. It seems silly that you wouldn't heat treat the part...if you dont just use normal PLA :D. Trying oven first...will do water on the next tests.
     
  20. daniel871

    daniel871 Well-Known Member

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    I can confirm that using a large convection/toaster oven to heat treat blocky/square parts for about 30 minutes at temperature followed by allowing them to cool back to ambient temps without opening the oven (a couple hours) resulted in some pretty ridiculously strong parts with no warping whatsoever.

    Artistic/thin parts with delicate areas might not hold up though.
     
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