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I have designed a cupholder for my center console in my truck with PETG. I was hoping it wouldn't deform and it didn't for a while but we got some high temperatures the past few days (around 32-38 °C or 90-100 °F).

Kind of figured it wouldn't hold up mid-summer but I was wondering if ABS would be my next best choice or if there is something better for this. It does see some sunlight but not a lot.

I do want to start producing some to sell and don't want it deforming in high-temperature areas. Also, I have an Ender 3 Pro so I can't do super crazy filaments.

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  • $\begingroup$ A previous question ("Can you put PLA parts in your car (in the sun)?") is similar to this one. This answer lists a few materials that can be used instead. $\endgroup$
    – 0scar
    Jul 28 at 12:30
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    $\begingroup$ If PETG is deforming in a hot car, you should reconsider where you're buying it from: proper PETG should be good up to at least 70°C (160°F), and more commonly 90°C (195°F). $\endgroup$
    – Mark
    Jul 28 at 20:49
  • $\begingroup$ @Mark not really: it holds shape up to 90 °C, but it loses strength much earlier. 70 °C is about the max for maintaining physical strength. Check polymaker.com/Download_File/TDS/… $\endgroup$
    – FarO
    Jul 30 at 8:52
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ABS, or preferably ASA which is "a better ABS", is probably your main option. ASA holds up better under UV/sunlight and is easier to print (less warping). Like ABS it should be printed with ventilation, and benefits some from an enclosure but can be done without it or with a primitive one (cardboard box).

Another great option would be TPU. It's not subject to a glass transition temperature above room temperature (my understanding is that technically its $T_g$ is very very cold, but that may be a misunderstanding) and does not really warp/deform permanently until you reach temperatures near what you could print it at. I've used it as a mold for melting crayons in an oven at 175 ˚F (80 ˚C) with no problem. Depending on your perspective it could be easier or harder than ABS to print. If your extruder is bad at handling flex materials you might have to go really slow, or you might have trouble with jamming on retraction, but unlike ABS it has no heat/warping issues while printing and can be done even on a cold bed, and does not particularly need ventilation (although as always, be careful if you have pet birds around).

Note that while TPU is considered a "flex" material, it can be fairly rigid at high infill with rigid infill patterns like triangles or cubic, or printed 100% solid, especially if you go with harder variants. 95A is typically the highest you see but sometimes you can find 98A.

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  • $\begingroup$ ABS+ is also a very good option: cheaper than ASA, little to no warping, good temperature resistance. Do UV really affect anything but the most superficial layers? do they penetrate? sometimes I feel it's an overblown issue $\endgroup$
    – FarO
    Jul 30 at 8:53
  • $\begingroup$ @FarO: It doesn't necessarily penetrate, but once the outer layers start to deteriorate they may wear away, exposing the lower ones. UV damage may also make the part turn ugly colors. Personally I don't recommend "plus" materials since you need to also recommend a particular brand, as there's no standard for what they mean. I'd rather recommend things that are reproducible and studyable without relying on a particular secret sauce. $\endgroup$ Jul 30 at 13:10
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If you don't need it to be super precise, nothing beats annealed HTPLA. If you keep it on the bed while annealing you can minimize warping and you'll get a part that can take up to 180 °C. Fusion filaments makes a great HTPLA+ that's reasonably cheap, and you can get it without a spool. Their reusable spool is on Thingiverse. Just don't keep it on the bed if you have a magnetic bed. HTPLA needs over 80 °C which will ruin a magnetic bed.

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    $\begingroup$ I regularly print ABS in a fully enclosed X-Max with a bed temp of 100 °C on a magnetic sheet. I've not seen reference for any printer about limiting temps to 80 °C or below. $\endgroup$
    – fred_dot_u
    Jul 28 at 8:43
  • $\begingroup$ I can't imagine you wouldn't get part deformation worse than what OP encountered in their car when heating the part to 80°C, unless you print at 100% infill and support it fully while baking. $\endgroup$ Jul 28 at 12:13
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Plastic bottles made out of PET hold up well in a hot car. Thus, I would expect PETG printed objects to hold up well in a hot car.

Is the deformation with PETG stress relief, i.e. warping like the print would have done if not sicking well to the bed? Try printing PETG with the bed at 100 °C. That's typical of ABS. Maybe that will relieve the stress during the print.

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    $\begingroup$ Plastic bottles contain water as a super heatsink. $\endgroup$
    – Trish
    Aug 2 at 12:48
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    $\begingroup$ It would help if we could see the distortion and how the cup holder was oriented during print. Then, we could see if the distortion was due to internal stress relief or the softness of the material in the hot car. $\endgroup$
    – Perry Webb
    Aug 2 at 12:54
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Personally, I'd get the design just right and then I'd use the "Get an Instant Quote" option on the "Solutions" menu at shapeways.com . It'll be expensive, but you could have it printed in sintered powdered stainless steel or aluminum. You'll want to design as many voids into it as you can, because they charge by the gram. There are cheaper vendors and you may have one locally, especially if you tell them "totally not a rush job" and they can run it with other parts.

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    $\begingroup$ While your answer does give an option, the OP is looking to produce the cupholder themself so as to sell online. The option you present adds additional costs that the OP will lose as part of their profits. $\endgroup$
    – agarza
    Jul 28 at 17:18
  • $\begingroup$ I missed the "sell" part. Yep. Nevermind. Injection Molding FTW. $\endgroup$ Jul 29 at 19:52
  • $\begingroup$ Kinda my bad, I probably shoulda mentioned its an older truck and theres not much for alternatives so this would just be a cheap alternative. and the petg only warped to the wait of itself hanging there on a 100° so it could definitely get pretty hot if the sun was shining in the truck too. Its still hanging there lol, didnt warp it too bad and still functional but definitely noticeable when you look at it $\endgroup$
    – WyattE
    Jul 30 at 7:12

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