15
$\begingroup$

I'm in the process of building my own head unit / stereo prototype for a car, which will have a 3D-printed enclosure.

My concern is that cars can get quite hot in the sun, and even more so if you live in hot climates. Some estimations put the interior of cars getting up to 50-60 °C, sometimes even in only 20 °C weather due to the 'greenhouse' effect created in the car. I live in a fairly temperate climate, but the summers can still get up to 20-29 °C (80-85 °F), and my car might get up to 60 °C/150 °F on a hot day.

The part won't be exposed directly to the sun, but will obviously be exposed to heat both from the interior of the car when in the sun, and potentially from the engine radiating heat through the firewall, though the latter factor will differ from car to car.

Should I be concerned using PLA for my part? If not, what material, if any, would be better suited for these possible temperatures (other than metal)?

$\endgroup$
16
$\begingroup$

No, PLA cannot be used in cars standing in the sun. Temperatures can locally get over 50 °C (122 °F).

I have printed sun visor hinge pins from PLA for a car (not exposed to direct sunlight either), but after one day in the sun (it usually doesn't get over 29 °C or about 85 ˚F here too) the pin deformed (only printed it for form fitting). The actual pin was eventually printed in PETG, and even with PETG the part deformed a little when it got really hot in the car.

Your part might not get that hot as it is lower in the car, but you could best print parts in Nylon (Polyamide, PA), ABS or any other high temperature resistant Co-Polymer (e.g. made from Amphora HT5300), there are lots to choose from nowadays.

If it is a non load bearing component that is not stressed (e.g. a cover or a bushing) it could be printed in PLA, but I would not take a change and would print it directly in a more temperature resistant material.


Downloading some of the technical data sheets from various filaments will give you for PLA:

Not suitable for long term outdoor usage or applications where the printed part is exposed to temperatures higher than 50 °C (122 °F).

similar for Nylon:

Not suitable for applications where the printed part is exposed to temperatures higher than 80 °C (176 °F).

To complete the overview, generally, materials should not be exposed prolonged periods of time above (give or take):

  • 70 °C (158 °F) for basic Co-Polymers
  • 85 °C (185 °F) for ABS
  • 100 °C (212 °F) for enhanced Co-Polymers
  • 105 °C (221 °F) for Polypropylene (PP)
  • 110 °C (230 °F) for Polycarbonate (PC)
$\endgroup$
  • 4
    $\begingroup$ As an anecdote, I've printed parts for my car that go under the hood (not touching the engine) in nylon--no issues and it's been at least a year at this point. $\endgroup$ – user60561 Jun 8 '18 at 3:11
  • $\begingroup$ A material that is used in automotive indurstry is ASA which can be printed at 240-265 °C (90-110 °C bed, enclosure recommended), and could withstand prolonged exposure to about 100 °C for a prolonged time. It has a tendency to warp for a price starting around 23€/kg. On the top end of the materials are iglidur-filaments, which are available with a sustainable temperature range of up to 180 °C at a price of 100€/kg upwards. Ceramic filaments like LayCeramic could get (after tempering in a kiln) sustain MUCH more, but cost upwards of 200€/kg $\endgroup$ – Trish Jun 30 at 15:54
  • $\begingroup$ I have a PLA washer fluid coupling piece under-hood with no major problem. $\endgroup$ – R.. Jul 1 at 23:21
  • $\begingroup$ @R.. Yes that is possible, hence: If it is a non load bearing component that is not stressed (e.g. a cover or a bushing) it could be printed in PLA. $\endgroup$ – 0scar Jul 2 at 6:35
  • $\begingroup$ @0scar: Yep, just providing another data point on that. $\endgroup$ – R.. Jul 2 at 19:43
9
$\begingroup$

If you put PLA parts in a sealed plastic bag (or two to keep it dry) and simmer in water (212 °F or 100 °C), the part "anneals". The time taken varies with the part shape, but for small parts should be about 15-30 minutes. You can simmer longer if unsure, but it provides no additional benefit once the part is annealed. When you remove and cool the annealed part, it will feel harder and more compact. You may also notice a slight hazing or color change.

Annealed parts become a bit more resistant to heat warp. The annealing process shrinks and hardens your part (I've annealed gears) so you need to account for the shrinkage by making the unannealed part slightly larger. I do this for stepper mounts or gears as needed. Putting your part in the passenger compartment of a car can work depending on your climate. My daughter-in-law has a camera mount on her dashboard showing significant warp, but she still uses it.

Here's more information and I'm sure you can find more...

$\endgroup$
  • 2
    $\begingroup$ Answer updated to reflect temp and time expectation $\endgroup$ – OyaMist Jun 8 '18 at 5:39
5
$\begingroup$

The sun will rot most, if not all plastics, with PLA, ABS and PETG rotting to varying degrees and at differing rates. So, if even part of your enclosure, such as the edges, are visible, they will invariably be exposed to the sun at some point (although maybe not sufficiently enough) which will make them brittle.

However, as you say, your main concern here is not direct sunlight, but heat. As this informative article, Using PLA for Long-Term Outdoor Applications, suggests:

PLA is great as the warping is less than with ABS.

Interestingly, it also notes (again related to sunlight, not a concern in your case):

As a side note, PLA is referenced as considerably UV resistant.


Similar Questions

Whilst your question is not a duplicate, as such, there are already a number of questions (and answers) on this topic, that I remember having seen and being relevant.

Whilst I have quoted some of the relevant parts below, it might also be worth taking a look at the other posts on these links:

Keep in mind that PLA has a much lower temperature point, where is starts getting flexible. I once had PLA-printed parts in my car in the summer for 3 hours and when I came back, they where bent.

I don't know about the weather conditions in your local environment, but if you experience hot temperatures and your sign is hanging in direct sunlight, I would suggest to make sure you secure the letters against bending (e.g. cover them with a coat of epoxy or something like this).

The property you're looking for in the thermoplastic (which will determine the continuous operating temperature) is glass transition temperature. This is the point at which the plastic begins to flow, and becomes deformable as EvilTeach described. PLA reaches this state at around 60 °C, whereas ABS is around 105°C, just suiting your specifications. To go a bit further, polycarbonate offers a glass transition temperature of around 150 °C, and Ultem at 217 °C.

50 °C is hot for you. PLA's glass transition temperature is 65 °C. A car in the mid-day sun can get very hot indeed.

... if the part is designed to be strong enough for its use in PLA, it will be no better in "stronger" ABS. If the PLA part will be "more precise" and "less warped" - that may well make it better for its use. Other than a widespread community dedication to self-replication, (or mostly self-replicating with some metal parts) there's plenty of arguments for making most printer parts out of machined metal, for that matter - much stronger than ABS or PLA.

PLA also will slowly melt in direct sunlight. I have seen this one firsthand, having left a print on my windowsill and watching it slowly morph with the weight of objects on top of it.

Also related, temperature wise, although not strictly in-car related (although that is where you would most likely find a travel mug), is the most informative answer by Ryan Carlyle, which makes mention of annealing as suggested by OyaMist Aeroponics's answer:

It is possible to anneal PLA to survive higher temperatures, as this increases the crystallinity of the polymer and thus makes it more heat-stable. However, that is highly experimental and results will vary considerably with filament provider, color/pigment, and annealing process used.

PLA would be a non-starter for outdoor use as it's biodegradable and can breakdown in sunlight. Albeit slowly, but won't be useful for long term project.

$\endgroup$
  • 1
    $\begingroup$ "Not an answer" flags on diamond-mod-answers are usually denied for natural reasons, but I really must point out that these types of answers are not a good fit for Stack Exchange. This should be a comment on the actual question. Your links will show up in the "linked" section on the post anyway. If you feel that those answers will also answer this question, you can copy the relevant portions to make this a freestanding answer. $\endgroup$ – pipe Jun 8 '18 at 7:16
  • 1
    $\begingroup$ @pipe - You are quite right, obviously. I apologise for setting a poor example and my rushed, link-only answer. I remember having seen similar questions to the OPs in the past, but did not wish to flag it as a duplicate, and so I started to make a comment, but then it did not fit within the character limit. It was very late and I didn't have time to complete the answer to a satisfactory standard (poor excuse I know). I will expand the post, quoting the relevant parts on the linked to questions now. :-) $\endgroup$ – Greenonline Jun 8 '18 at 9:45
  • 1
    $\begingroup$ @pipe - Updated somewhat. BTW, I really like your homepage's pet peeve about SI units. It also annoys the hell out of me, and I am forever editing and adding &nbsp between the amount and the units - much to some people's chagrin. $\endgroup$ – Greenonline Jun 8 '18 at 10:54

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.