Can you put PLA parts in your car (in the sun)? 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&nbsp;°C, sometimes even in only 20&nbsp;°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&nbsp;°C (80-85&nbsp;°F), and my car might get up to 60&nbsp;°C/150&nbsp;°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)?
No, PLA cannot be used in cars standing in the sun. Temperatures can locally get over 50&nbsp;&deg;C (122&nbsp;&deg;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&nbsp;&deg;C or about 85&nbsp;˚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&nbsp;&deg;C (122&nbsp;&deg;F).


similar for Nylon:


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


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


70&nbsp;&deg;C (158&nbsp;&deg;F) for basic Co-Polymers
85&nbsp;&deg;C (185&nbsp;&deg;F) for ABS
100&nbsp;&deg;C (212&nbsp;&deg;F) for enhanced Co-Polymers
105&nbsp;&deg;C (221&nbsp;&deg;F) for Polypropylene (PP)
110&nbsp;&deg;C (230&nbsp;&deg;F) for Polycarbonate (PC)