The five materials at a glance
- PLA: stiff and dimensionally stable, for indoor use. Heat resistance (HDT) 57 °C, the lowest of the five.
- PETG: tough and suitable for outdoor use. HDT 69 °C. Slightly weaker between layers.
- ABS: handles heat and impact, for technical parts. HDT 87 °C. Less suitable outdoors: can discolour and turn brittle in the sun.
- ASA: for long-term outdoor use and sun. HDT 100 °C, the highest of the five.
- TPU: flexible and shock-absorbing. Stretches > 650% before breaking, according to the datasheet. Not for stiff parts.
All values side by side, including tensile strength and impact strength, are in the materials table.
What does heat resistance (HDT) tell you?
HDT stands for heat deflection temperature: the temperature at which a test bar under a fixed load (0.45 MPa, per ISO 75) bends by a set amount. It is a number for comparison, not a guarantee. A part under stress, or one that stays warm for a long time, can start to deform below that temperature. So leave a margin between the HDT and the temperature the part has to work in.
The values on this site are typical values from the technical datasheets of the filament used, measured on test pieces with 100% infill. A printed part with less infill or thinner walls behaves differently from such a test piece.
Outdoors and in the sun: ASA or PETG
Sunlight (UV) and changing temperatures are hard on plastic. PLA is meant for indoor use: in the sun it quickly gets too warm. ABS is less suitable: it can discolour and turn brittle in the sun.
ASA is made for outdoor use. It is UV-resistant and, at 100 °C, has the highest heat resistance of the five. Think of parts for a car, the garden or signs. PETG is also suitable for outdoor use and is tough, but handles less heat (HDT 69 °C).
Heat: in a car or near an appliance
In a car parked in the summer sun, it gets much hotter inside than outside, especially on the dashboard and behind the windows. Choose ASA (100 °C) or ABS (87 °C) there. PLA (57 °C) is not suitable for that spot.
Near appliances that get warm, such as a lamp or a housing around a motor, ASA and ABS are also the obvious choice. Places that get really hot, such as right next to a hob, oven or exhaust, are not for these filaments.
Flexible: TPU
Does a part need to bend, spring back or absorb knocks? Then TPU is the choice. It is a rubber-like filament that stretches a long way and then returns to shape. Suitable for caps, dampers, feet, cases and grips.
For a part that has to be stiff, such as a bracket or an axle, TPU is too soft. In that case, combine a stiff material with a separate flexible part.
Strong and impact-resistant
For a part that has to take a knock, impact strength counts. Of the stiff materials, ASA and ABS score highest, followed by PETG and PLA. PLA is stiff and strong under a steady load, but breaks sooner on impact.
With printed parts, the print direction also determines strength: a part is always weaker between its layers than along them. A well-chosen direction sometimes makes more difference than another material.
Quick choice
- Indoors, decorative or a model: PLA.
- A strong everyday item, outdoors too: PETG.
- Long-term outdoors, in the sun or in a car: ASA.
- A technical part that gets warm, indoors: ABS.
- Flexible or shock-absorbing: TPU.
Not sure? Choose "Not sure yet" in the quote form and describe where the part will be used. You will get advice. More about 3D printing your file.