Guides / 3D printing materials

PLA, PETG, ASA or resin: which one can take what your part will go through

The useful question is not which material is best, but what will happen to the part: whether it will sit in the sun or inside a car, whether it has to flex to snap into place, or whether it has to measure exactly. Here are the figures from the manufacturers' data sheets, read to answer that, and what three real jobs taught us.

Updated September 24, 2026

The short answer

Heat: the temperature at which each one softens

Every data sheet gives the Vicat softening temperature, the temperature at which a loaded needle sinks one millimeter into the plastic. It is not the temperature at which the part melts, but the one from which it stops holding its shape if something pushes on it, and it is the figure that decides whether a part survives the sun or a car.

In a study by Arizona State University and the University of California San Diego, the dashboards of cars parked in the sun on summer days reached 69 °C on average within an hour. There, a PLA part deforms, a PETG part sits right at its limit, and ASA still has more than 35 degrees of margin, which is why we make in ASA a car mount, anything that sits by a window or a dark part that spends the day in the sun.

The sun at altitude is stronger than it looks

The other effect of the sun is ultraviolet radiation, which over the months fades and weakens many plastics. In Bogotá it weighs more than you would think: the World Health Organization estimates that UV rises by about 10% for every 1,000 meters of altitude, and the city sits above 2,600. ASA was made for the outdoors; it withstands UV about ten times better than ABS, and it is the plastic of many exterior car parts.

The setting block we designed for a glass railing is a good example of where the real difficulty lay. It sits at the bottom of an aluminum profile, outdoors, holding 16 mm glass that weighs about 80 kg in a 2 × 1 m panel; spread over the block's bearing strips, that weight puts a pressure on the plastic about 400 times lower than what ASA can take. Strength was never the problem, the sun was, and that is why it is made in white ASA.

Layers: where a printed part breaks

A filament printer builds the part one layer on top of another, and the bond between one layer and the next is weaker than the plastic itself. The manufacturers' data sheets measure it by pulling test bars in both directions:

With impacts the difference is larger: the same Bambu Lab data sheets give PLA half the impact strength between layers that it has along them, and PETG less than a third. That is why, before printing, the part is oriented so the load runs along the layers and does not tend to pull them apart.

Sometimes no orientation works. The push-in cap from one of our jobs has 1 mm walls that flex as it snaps into place, and when we measured the first version of the model we found that 64% of its surface is in walls 1.2 mm thick or less, spread across all three directions: the best possible orientation left 60% of that thin material bending against the layers. In PLA it always broke when snapped in, so it moved to resin.

Resin: strong if treated right

In a resin printer the part comes out of a liquid that hardens with light, and the ABS-like resin we use for the cap stretches 35 to 40% before breaking, according to its data sheet, against 12% for PLA along the layers and 7.5% between them. That elasticity is what lets 1 mm walls flex without breaking.

But resin depends on the process more than any other material. One batch of caps came out with a brittle surface because of three things together: they were not washed submerged, they got the minimum cure, and they spent an hour in the sun. The manufacturer's data sheet asks for at least three minutes of washing and three of curing, and Formlabs, which makes resin printers, warns that sunlight makes parts more brittle and changes their color. Since then they are washed submerged in two baths, cured as the data sheet says, left to rest before testing the fit and kept out of the sun, and for the same reason resin is not for outdoor use.

The measurement we can promise

3D printing is precise, but not equally in every direction. For the railing setting block we promised ±0.2 mm on the cross-section, which is what fits in the profile, and ±0.5 mm on the length, because ASA shrinks a little as it cools and on a long part that adds up. The segments also leave a gap between them: in the sun the plastic expands several times more than the aluminum around it and, without that play, they would push against each other.

How we choose in the workshop

• ASA by default in what we sell printed, like the Pulgar and the Spiral Earrings, because it handles sun, heat and rain without you having to think about it.
• PLA only when the color you want exists in PLA and not in ASA.
• Resin for small parts with thin walls that have to flex, or with very fine detail, always indoors.
• 925 silver for jewelry: the model is printed in resin, cast and polished.
• If 3D printing is not the way to make your part, we tell you when we quote.

Each manufacturer measures in its own lab with its own test bars, so these figures are for comparing materials, not for calculating a part to the decimal.