3D printing materials 101: what to print in, and why

Material choice is the hidden half of every 3D printing project. The same CAD file can become a cheap visual prop or a load-bearing production part depending on what it's printed in. Here's the field guide we use.

Two numbers explain most material decisions:

• Heat deflection temperature — the temperature at which the part starts to soften under load. A car interior in direct sun regularly reaches 60–80 °C; an engine bay reaches far more.
• Impact strength — whether the part cracks or bends when something hits it. Stiff is not the same as strong.

Everything below is a trade between those two, plus UV stability, cost and printability.

PLA

The friendly default. Easy to print, made from renewable feedstock, widely available, and it looks good straight off the machine.

• Heat: poor. It softens around 55–60 °C. A PLA part left on a dashboard in July will droop, and we have the sad photos to prove it.
• Strength: stiff but brittle. It resists bending and then snaps rather than yielding.
• UV: poor to moderate.
• Use it for: display models, indoor enclosures, shop-window pieces, concept parts, fit checks before committing to a real material.

PETG

PLA's tougher cousin, and the workhorse of our FDM machines.

• Heat: moderate, roughly 70–80 °C.
• Strength: good impact resistance. It yields and bends before it breaks, which is exactly what you want in a clip or a bracket.
• UV: moderate. Fine for occasional outdoor use, not for a decade on a roof.
• Use it for: functional prototypes, brackets, mounting tabs, interior parts that get handled, replacement parts where the original was brittle.

ABS and ASA

Stronger, more heat-resistant and more chemically resistant than PLA or PETG. ASA is ABS's UV-stable sibling.

• Heat: good, roughly 95–100 °C.
• Strength: good impact resistance, and it can be vapour-smoothed or bead-blasted to a convincing factory texture.
• UV: ABS yellows and chalks outdoors. ASA does not — that's the whole point of it.
• Printing note: both need an enclosed printer and decent ventilation. They shrink as they cool, so large flat parts want careful orientation.
• Use it for: automotive interior trim, vent surrounds, mirror caps, outdoor housings, anything that lives in a hot cabin.

Most of the discontinued car trim we reproduce is printed in ASA for exactly this reason — see the ten discontinued car parts we print most often.

Nylon — PA12, glass-filled, carbon-filled

The production material. Tough, slightly flexible, wear-resistant, and the natural fit for SLS.

• Heat: good, 100 °C and beyond for filled grades.
• Strength: excellent, and unusually good at surviving repeated flexing — which is why every snap fit and living hinge we make ends up here.
• Fillers: glass raises stiffness and heat resistance; carbon raises stiffness at lower weight. Both reduce toughness slightly, so filled nylon is less forgiving of sharp impacts than plain PA12.
• Water note: nylon absorbs moisture from the air, which softens it slightly and can change dimensions on precision parts. Parts destined for tight tolerances get dried and measured after conditioning.
• Use it for: clips, latches, hinges, gears, load-bearing trim, marine hardware, short production runs.

Polycarbonate

The strongest common FDM material, and the least forgiving to print.

• Heat: excellent, roughly 110–130 °C.
• Strength: very high impact resistance — it deforms rather than shattering.
• UV: poor without additives; it yellows.
• Use it for: parts near heat sources, protective covers, tooling, anything where PETG and nylon have both already failed.

Photopolymer resins (SLA)

A family rather than a single material.

• Standard resin: sharp detail, brittle. Visual parts only.
• Tough / durable resin: approximates ABS behaviour. Better for functional prototypes.
• Flexible resin: bends and returns.
• Castable resin: burns out cleanly for lost-wax casting — the route to a metal part from a printed master.
• High-temp resin: survives well past 200 °C, used for moulds and fixtures rather than end-use parts.

All of them need washing, post-curing and support clean-up, and most of them need paint or clear-coat if the part will see sunlight.

TPU and flexible filaments

Rubber-like, measured by Shore hardness — 95A is a firm bumper, 85A is a soft gasket.

• Prints slowly and dislikes sharp retractions, but produces genuinely flexible, abrasion-resistant parts.
• Use it for: gaskets, seals, grips, dampers, protective feet, wearables.

Quick comparison

Three mistakes worth avoiding

1. Printing a car part in PLA. It's the most common request and almost always the wrong answer. Interior temperatures alone rule it out.
2. Choosing by tensile strength alone. Most plastic parts fail from impact or repeated flexing, not from being pulled apart. A part that flexes and returns beats a part that is stiff and cracks.
3. Ignoring the finish before choosing the material. If the part must be painted anyway, a cheaper base material may be fine. If it must match a factory grain out of the box, the material and process choice is already made for you.

Which do I pick?

The honest answer: send us the part and the use case. Material selection is half science and half experience — and we've made a lot of bad picks so you don't have to.

If you're still deciding on the process rather than the material, start with FDM vs SLA vs SLS. If you know the material and want a quote, our 3D printing service page has the specifics, and contact us reaches a human.

The Audi A6 C5 cup holder vent shown with this article is printed in PETG, the same default material this guide recommends for most exterior and cabin trim.

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