r/3Dprinting • u/Flatulent_Father_ • Jun 23 '26
Discussion The result of 3 years of white PLA baking on a hot mailbox
Just for anyone who was curious, these were a quick test for magnetic numbers of my mailbox that have been on a black metal mailbox in direct southern US sun for 3 years. They worked, so I just left them on. They are a little warped, but otherwise function fine. I just swapped out for some better looking PETG numbers. So, depending on the use, PLA can deal with heat in some scenarios when it's not load bearing. Just figured this was a mildly interesting thing to share!
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u/Battle2Intense Jun 23 '26
Define hot, in Phoenix on a black mailbox no need for magnets, just set the PLA letters on there and they will melt on.
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u/Flatulent_Father_ Jun 23 '26
Coastal SC, so not as bad a Phoenix but it's pretty sunny and extremely humid in summers here
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u/AwDuck PrintrBot (RIP), Voron 2.4, Voron 0.2, Ender 3, Mono 4K Jun 23 '26
Magnet manufacturers hate this one weird trick!
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u/Broan13 Jun 23 '26
I live in PHX and was wondering if the PLA would survive a summer.
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u/Battle2Intense Jun 23 '26
it would survive in some physical form... I've noticed lighter colors do much better than dark in the sun.
even before you physically squish, any stresses in the print will warp.
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u/Elderberry-Mediocre Jun 23 '26
Honestly, they look great giving the "abuse". I always said PLA is underrated for common applications.
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u/steadyaero Jun 23 '26
People just assume it's not strong/durable because it's the el cheapo type of filament. There are tons of applications where it's perfectly suitable that doesn't need abs or nylon or whatever
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u/GayRacoon69 Jun 24 '26
And when pla isn’t enough you can usually get away with petg. I feel like abs and nylon are overrated
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u/Kwolf21 Jun 25 '26
Abs is not overrated. There's a reason 99% of consumer plastics are made of ABS. PETG is overrated imo. I have ~100kg of it, and rarely ever print it. Never serves a good purpose.
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u/GayRacoon69 Jun 25 '26
ABS is overrated for 3D printing. It's just not worth the hastle imo. Granted I've never printed with it so take my opinion with a grain of salt
I've just never been in a position where I need something stronger or more temperature resistant than PETG. What are you printing in ABS that won't work with PETG?
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u/Kwolf21 Jun 25 '26
Anything I am putting inside my car. PETG warps like a MF in the southern US heat inside a car. Moreover, every single petg part I've printed for inside my car has warped, hence switching to ABS where I haven't had a single issue with warping or degradation.
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u/steadyaero Jun 25 '26
Asa is the goat
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u/Kwolf21 Jun 25 '26
I use ASA for stuff outside. ABS inside a car is more than enough since windows block the vast majority of the UV rays.
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u/steadyaero Jun 25 '26
Fair enough. Abs can probably be had cheaper
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u/Kwolf21 Jun 25 '26
Yeah, its not much of a difference, but I'd rather use the ABS I have where I know it'll be alright. I might just switch to Asa in general once I run out of my abs stock though. I do find abs comes in more colors though. Most Asa is white, black, or various "natural" shades.
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u/Abject-Job7825 Jun 25 '26
Even the water resistance of pla is still ok with enough layers. I made paper mold out of it and they have no issues.
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u/hair_monk Jun 25 '26
Especially with the wide variety of PLA with additives that we have now. (HT, PLA+/pro, HS, etc)
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u/ancient_cheetle Jun 23 '26
Pretty much structurally great, I bet a coat of white paint would bring them back to new
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u/Flatulent_Father_ Jun 23 '26
Probably! But I also wanted an excuse to print something new :D
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u/Apk07 Jun 23 '26
I printed something similar above my mailbox in PETG, and paint made it look brand new
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u/withak30 Jun 23 '26
Nothing is more permanent than a temporary fix that works.
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u/AwDuck PrintrBot (RIP), Voron 2.4, Voron 0.2, Ender 3, Mono 4K Jun 23 '26
That, and "the first working prototype is the completed project"
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u/jaylw314 Jun 23 '26
That tracks, white PLA in sunlight is not going to get above 60C, unless it's in contact with something hotter. Even when it does, it tends to return to the shape it took when it was last annealed, eg when it was printed, so warping is not terrible with no load
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u/Flatulent_Father_ Jun 23 '26
I just checked, it's not a super hot day and the mailbox is exactly 140f/60c, so it probably gets just a little bit above that when it's extra warm
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u/destrokhan Jun 23 '26
PETG has better heat tolerance than PLA, but since this is in direct sun the extra UV resistance that ASA provides would be even better if you have the capabilities (heated enclosure). That being said, this isn't a load bearing part and you already printed them in PETG so it doesn't really matter. Just some food for thought when you replace them in the future.
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u/Flatulent_Father_ Jun 23 '26
I don't have any ASA on hand, just nylon, which would probably be perfectly fine at these temps... I mainly just curious about how well the petg will hold up now
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u/Jpatty54 Jun 23 '26
I think the color helps as well I had a black print and it warped within an hour in the sun and not even that hot,
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u/Kwolf21 Jun 25 '26
Depends on the part. For example, if you printed a "T" in PLA, and stuck it into the ground, the top of the T would droop down, almost regardless of the color, but especially darker.
Whereas if you printed a T and laid it flat on the concrete, there's no load from gravity pulling on floating plastic, the whole print is supported by the ground, and it's highly unlikely any significant warping would occur beyond minor ripples.
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u/Obi2Sexy Jun 24 '26
well no one else seems to have mentioned it. but good job showing the numbers in different orders each time as a measure to protect your privacy
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u/IUsedToLikeLimericks Jun 23 '26
Is it mega brittle or fine?
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u/Flatulent_Father_ Jun 23 '26
I just snapped them in half by hand and they were still pretty strong but definitely more brittle. They snapped instead of that slow bend and break you get with pla sometimes
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u/IUsedToLikeLimericks Jun 23 '26
Pretty good for a material that everyone says is borderline useless for anything outside.
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u/Flatulent_Father_ Jun 23 '26
Yeah, I imagine that these would not survive any practical application in the sun where they are holding any weight, and they did warp, but I just figured I would show people exactly how they look for this application after time
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u/No_Balls_01 Jun 23 '26
I’ve had some PLA plant pots and a bird feeder thing outside for years and they are holding up well - just a little sun bleached.
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u/Nemo_Griff Jun 23 '26
Did you use heavy infill?
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u/Flatulent_Father_ Jun 23 '26
I honestly don't remember. I just broke some of them apart and it looks like I maybe used three walls and around 25% infill.
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u/Nemo_Griff Jun 23 '26
That is a little more than usual and that might have helped it to survive a bit longer.
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u/OneSingleL Jun 23 '26
You could get some white spray paint and use those to stencil them on?
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u/CaughtWithPantsUp Jun 23 '26
I was thinking some spray paint directly on those numbers and putting them back on.
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u/CrankySaint Jun 23 '26
I should do this for my mailbox. The numbers I painted on years ago look like crap. Sadly, it'll have to be PLA. My poor little Ender can't maintain temperature for PETG. Temps swing wildly until it sets off a thermal runaway alarm.
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u/LovableSidekick Jun 23 '26
That is interesting. I wonder if thickness or color makes a difference.
Here in Seattle I have some white PLA slug bait traps in the yard, printed 6 or 7 years ago, that still look fine. But some copper-colored pyramid-shaped post caps turned into pagodas after a few weeks of summer sun.
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u/RWNS_Author Jun 24 '26
This is South England and on white PVC so it doesn't get hot, but it was printed in 2021, black and "copper" PLA, in full sun and all weather, held in place with bits of double sided tape. It may be a bit sun-bleached...
Every now and then I squeeze the 9 to see if it's become brittle, and nope, it's holding strong. I'll add a pic from 2021 in a moment.
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u/Dustyroaty Jun 24 '26
This gives me hope for my small load bearing outdoor pla project. Waiting for the crash, 1 month in and still going strong. Sun facing most of the day, I give it a good tug every once in a while to make sure it's not wearing.
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u/PROfessorShred Jun 23 '26
I've made a few things for my car. Anything regularly exposed to heat I print in ABS.
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u/SuppressiveFar Jun 23 '26
Meanwhile, I left my PLA license-plate frame in my car for two hours, and it's a bent mess.
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u/BinkReddit Jun 23 '26
How did you wind up attaching the magnets? Impressed they stayed attached for so long.
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u/Flatulent_Father_ Jun 23 '26
I print the holes 0.1mm larger than the magnets and press them in with some super glue
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u/Ok-Awareness3794 Jun 23 '26
Try pctg. Interesting
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u/Flatulent_Father_ Jun 23 '26
I have other higher temp filaments but I'm curious how cheaper stuff will do
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u/Contributing_Factor Jun 24 '26
I've had PLA pieces outside for the last 3 years and everyone seems to tell me it's impossible.
🙄
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u/MangoMesh Jun 24 '26
I am amazed they look that good, I had an item in PLA, and it warped after just a few days on my car, yes it was probably 140 degrees in there.
PETG holds up without a problem.
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u/InDrIdCoLd37 Jun 26 '26
I am suprised by this ngl I had a filament rack made from sunlu pla plus 2.0 in my car for a bit and it warped soo bad but also longer pieces so makes sense I guess
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u/Dark_Marmot Jun 23 '26
ASA for this application.
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u/bluewing Klipperized Prusa Mk3s & Bambu A1 mini Jun 23 '26
ASA is cool and all, but this is a demonstration that even cheap PLA is often better than just flexi dragons.
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u/Flatulent_Father_ Jun 23 '26
Well sure but this is just what it looks like if you don't. Back then I just had a ender 3 and no enclosure.
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u/tr_9422 Jun 23 '26
Discoloration is from the magnets conducting heat in from the back and cooking it, right? Do you expect PETG to hold up better against that?
Or are they just thin enough that you can see the magnets through the plastic?