You designed the part, it printed clean, it fit perfectly on the bench. Then it spent an afternoon in a parked car in July and came out sagging, bowed, or curled. Nothing was wrong with the print. It was the wrong material for where the part had to live.
In Tucson, heat is the most common reason a 3D-printed part fails in the field, and it's almost entirely avoidable. The fix is choosing the right plastic before you order. Here's how to make that call.
The one number that explains it: glass transition
Every printable plastic has a glass transition temperature — the point where it stops being rigid and starts to soften and slowly deform under its own weight or any load. It sits well below the temperature where the plastic melts, which is why a part can warp without ever looking melted.
For PLA, that softening starts at around 60 °C (140 °F). That sounds high until you measure the inside of a car in an Arizona parking lot.
How hot it actually gets here
On an ordinary Tucson summer day, the air inside a closed, parked car climbs past 70 °C (160 °F), and surfaces in direct sun — a dashboard, a rear deck — get hotter still. That's not the extreme; that's a normal afternoon.
It isn't only cars. Uninsulated garages, sheds, attics, and closed storage bins all run past PLA's softening point through the summer. A part that lives in any of those places has to be judged against those temperatures, not against the temperature of your shop.
So a PLA part sitting on a dashboard is sitting above its softening point for hours. It will creep and deform. That's physics, not a print defect.
The three materials, and when to pick each
PLA is the most rigid and prints the finest detail, but it's the least heat-tolerant and the most brittle over time. It's the right pick for indoor display pieces, prototypes, and fit checks — anything that stays cool. It's the wrong pick for heat, sun, or the outdoors.
PETG softens much higher — around 80–85 °C (175–185 °F) — and is tougher and more impact-resistant than PLA. It's our recommended default for functional parts, and the right choice for most things that see heat, sun, or outdoor use. The trade-off: it prints a little less crisply than PLA, so very fine detail is slightly softer.
ASA is the most heat- and UV-resistant of the three, and it holds up to prolonged sun without going brittle the way PLA and PETG eventually do. It's the material for parts that live outdoors permanently or in the harshest heat. Its trade-offs are real, though: it's harder to print reliably, it can emit an odor while printing, and it typically costs more than PLA or PETG. You choose ASA when the conditions genuinely demand it — not by default.
You can see how we describe each material — and which one we recommend by default — in the materials overview on our homepage.
| PLA | PETG | ASA | |
|---|---|---|---|
| Softens around | 60 °C (140 °F) | 80–85 °C (175–185 °F) | Highest of the three |
| Toughness | Most brittle | Tough, impact-resistant | Tough, UV-stable |
| Detail | Finest | Slightly softer | Slightly softer |
| Best for | Indoor display, prototypes, fit checks | Most functional parts; heat, sun, outdoors | Permanent outdoor use; harshest heat and UV |
| Watch out for | Softens in heat; brittle over time | Slightly less fine detail | Harder to print; odor while printing; costs more |
The short version: PLA for cool indoor parts, PETG for most functional work, ASA when the sun and heat are relentless.
What this means for the parts people actually order
- A console organizer or small enclosure that rides in your car → PETG at minimum; ASA if it sits in direct sun.
- A desk organizer, a display model, a prototype you're checking for fit → PLA is perfect and prints beautifully.
- A planter, a hose guide, a patio or yard part that stays out year-round → ASA for the sustained sun; PETG for seasonal use.
- An enclosure for electronics in a hot garage or shed → PETG, or ASA if it's near real heat.
- A part that lives indoors and never gets warm → PLA, and don't overthink it.
Not sure? Ask before you order
Choosing between PLA, PETG, and ASA is exactly the kind of call we're glad to make with you — we'd rather get the material right up front than see a part warp in service — that's the wrong material for the job, not a defect.
When you're ready, upload your STL and you'll see a real price in seconds, calculated from your actual part. (STEP files are quoted by hand.) If you're not sure which material fits, email support@qfablabs.com first and we'll help you decide.
FAQ
Does PLA melt in a hot car?
PLA doesn't fully melt at car temperatures, but it doesn't need to. It begins to soften and deform at around 60 °C (140 °F), and a parked car in Arizona easily exceeds that. A PLA part left in a hot car can sag, bow, or curl without ever looking melted.
Is PETG or ASA better for outdoor use?
Both handle heat and sun far better than PLA. PETG is the right choice for most outdoor and functional parts. ASA goes further — it's the most heat- and UV-resistant of the three and holds up to prolonged sun without going brittle, which makes it the pick for parts that live outdoors permanently.
What temperature can PETG handle?
PETG stays rigid up to roughly 80–85 °C (175–185 °F) before it begins to soften. That covers most real-world heat exposure, including hot cars and garages. For sustained extreme heat or years of direct UV, ASA is the better choice.
Which material should I use for a part that sits in the sun?
For occasional or seasonal sun, PETG. For a part that lives in direct sun year-round, ASA — it resists UV and heat better than either PLA or PETG and stays tougher over time.
Do you offer a high-temperature, UV-resistant material?
Yes. ASA is the most heat- and UV-resistant material we print, made for parts that live outdoors or in high heat. It's harder to print and costs more than PLA or PETG, so it's the right choice when the conditions call for it rather than a default.
Will a 3D-printed part fade or degrade in the sun over time?
Prolonged direct UV is hard on PLA and PETG, and colors can fade with long outdoor exposure. ASA is the most UV-stable of the three and holds up best for permanent outdoor use.