Why 3D printed PLA parts warp in a hot car (and what to print instead)
The short answer
PLA starts to soften at about 55 to 60 °C. A parked car in an Australian summer gets hotter than that, so a PLA part on the dashboard or parcel shelf slowly bends out of shape. Reprint it in ASA, or in ABS if the part stays out of direct sun.
Why it happens
Every plastic has a temperature where it stops being rigid. For PLA that point is low. Below it, PLA is stiff and holds sharp detail, which is why it is the first choice for models, gifts and organisers. Above it, the part goes soft. Anything pushing on it, even gravity or the weight of a phone, bends it into a new shape. When it cools down, it keeps that new shape.
Cars heat up fast. With the windows up on a sunny day, the air inside climbs well above the temperature outside. Dark surfaces in direct sun, like the dashboard, the parcel shelf and the top of the centre console, get hotter again. It does not take a record heatwave. A normal Australian summer day is enough.
Printed parts also give before the textbook softening point when they carry a load. A phone mount holding a phone, or a clip under tension, will droop sooner than a loose part sitting in a cup holder.
Signs your part has a heat problem
- Arms on a phone or GPS mount that sag or point down.
- Clips and hooks that held fine in winter and stopped holding in summer.
- Flat parts that have curled, bowed or twisted.
- Screw holes that have gone oval or pulled through.
- A part that has gone pale and chalky on the side facing the windscreen. That is UV damage, PLA's other weak spot.
None of this means the print was faulty. PLA was simply the wrong plastic for the job.
What to print instead
- ASA, the first choice. It holds its shape to around 90 to 95 °C and is UV stable, so it won't fade or go brittle behind the windscreen. It is tough, it sands and paints well and it costs a little more than PLA.
- ABS, for interior parts out of the sun. Same heat resistance as ASA without the UV protection, and a little cheaper. Good for under-dash clips, console parts and trim that the sun doesn't reach.
- ABS-GF or PC-GF, for parts near real heat. These glass-filled grades stay straight and stable in heat. Engine bay trim and covers are the typical use. Ask us before ordering anything that goes under the bonnet.
- TPU for rubber parts, with care. TPU 95A suits feet, grommets and pads, but it is not rated for a hot car on our chart. Keep it out of direct sun.
What to avoid: PLA and PETG. PETG is fine to about 70 to 75 °C, which is great in a hot shed but not enough for a dashboard in full sun.
The material comparison table shows every material we print against the same six tests, including Hot car.
Tips for car parts that last
- Give it more wall. For a part that carries load, choose Strong in the quote tool. Thicker walls and more solid infill resist bending in heat.
- Lighter colours run cooler. Black and dark grey soak up more sun than white or light grey. If the colour doesn't matter, go lighter.
- Avoid long thin arms. A rib or gusset along a mount arm stops it drooping far better than a thin straight arm.
- Tell us it's for a car. Put it in your notes. We check every order by hand, and if the material doesn't suit, we email you before anything is printed.
- Keep printed plastic out of safety-critical jobs. Brake, steering and seatbelt parts are not a job for a 3D print.
Getting it reprinted
If you still have the file, upload it to the quote tool, choose ASA and you will see the price in seconds. There is no minimum order, so a single replacement is fine. Each order has a $16.50 inc GST setup fee, standard orders are dispatched in 3 to 5 business days and we post anywhere in Australia.
If all you have is the warped part, our guide to getting a replacement printed from a broken original walks through turning it into a file. For other material questions, the help centre has straight answers.