What Is ASA Filament? Outdoor-Ready Plastic Explained

ASA filament is a 3D printing plastic made from acrylonitrile styrene acrylate. It is a close relative of ABS with much better UV and weather resistance, so it suits parts that live outdoors. It still warps, needs a hot bed and releases fumes. This research-based explainer covers what ASA is and when to use it.

What is ASA filament made of?

ASA stands for acrylonitrile styrene acrylate. Wikipedia describes it as an acrylate rubber-modified styrene acrylonitrile copolymer: rubber particles, usually n-butyl acrylate, grafted with styrene-acrylonitrile chains and embedded in a styrene-acrylonitrile matrix.

It is structurally very similar to ABS. The difference is the rubber. Wikipedia says the acrylate rubber lacks the double bonds of the butadiene rubber in ABS, which is what makes ASA far more resistant to sunlight and weather. Prusa's knowledge base calls ASA a technical material and the successor to ABS.

ASA filament properties at a glance

The figures below come from Prusa's ASA and ABS knowledge base articles and Wikipedia. Other makers publish different numbers, so use the range printed on your own spool.

Is ASA filament good for outdoor use?

Yes. Outdoor use is the reason ASA exists. Wikipedia says its acrylate rubber gives about ten times the weathering and ultraviolet resistance of ABS, and that ASA keeps its gloss, color and mechanical properties outdoors. Prusa lists high UV resistance first among ASA's advantages and recommends it for outdoor parts.

Typical uses are garden and balcony brackets, sensor housings, mounts, signage, fan shrouds and other parts that sit in sun or rain. Wikipedia notes the same material is used commercially for siding, exterior vehicle parts and outdoor furniture. These are material-level facts; a given spool and part design will still behave differently.

What are the downsides of ASA filament?

The main downsides of ASA are significant warping, the need for an enclosure on large parts, fumes, high print temperatures and some moisture absorption. Prusa lists all of these as cons.

• Warping. Prusa says it is caused by temperature differences between the model and its surroundings. ASA warps less than ABS but still lifts corners on large parts.
• Enclosure. Prusa calls an enclosure necessary for large parts. Our guide to enclosed vs open-frame 3D printers explains what that means for your printer choice.
• Fumes. Prusa warns of potentially dangerous styrene fumes and advises good ventilation without a draft across the print.
• High temperatures. About 260 °C on the nozzle and 105 to 110 °C on the bed rules out some entry-level hardware. Check your printer's rated limits and see hotends and nozzle materials.
• Moisture. Wikipedia says ASA is mildly hygroscopic, so drying may be needed. Our guide on how to dry filament covers the method; follow your filament maker's drying temperature.

Is ASA better than ABS?

ASA is better than ABS for anything exposed to sunlight, and the two are otherwise similar. Prusa describes ABS as basically a predecessor of ASA, with slightly worse UV resistance and more significant warping and odor during printing. Wikipedia adds that ASA resists environmental stress cracking better, especially against alcohols and many cleaning agents.

For a bracket that stays indoors, ABS is usually adequate and is often cheaper. For a part in sunlight, choose ASA. The full comparison is in ASA vs ABS.

Do you need an enclosure to print ASA?

An enclosure is needed for large parts and advisable for most ASA printing. Prusa says that without one you should enable the draft shield in PrusaSlicer, under Skirt and Brim, to keep the model warmer. Small flat parts may print on an open-frame machine, but large parts are likely to warp.

Prusa also warns that printing large amounts of ASA in an unventilated enclosure can deform plastic printer parts such as the fan shroud and extruder. Ventilate the room and follow your printer maker's guidance.

What settings does ASA filament use?

Prusa recommends a nozzle at 260 °C and a bed at 105 °C for the first layer and 110 °C afterwards, on a smooth or powder-coated PEI sheet with a glue stick. Glass may need a thin layer of acetone with dissolved ASA or ABS, but Prusa says never to apply acetone or ABS/ASA juice to a powder-coated sheet. Treat these as a starting point and follow the label on your spool; our ABS print settings guide covers the closely related enclosure and cooling questions.

Is ASA filament toxic?

Prusa says ASA releases potentially dangerous fumes, naming styrene, and advises printing in a well-ventilated area without a draft over the print. This site does not give health advice. Follow the printer and filament maker's guidance, read the safety data sheet for your spool, and see our 3D printer safety basics.

How is ASA post-processed?

ASA is easy to finish. Prusa says it can be sanded wet or dry, glued or welded with acetone, and smoothed with acetone vapor for a glossy finish, though smoothing tends to reduce fine detail and sharp edges. If you are budgeting a project, the print cost calculator helps estimate material cost per part.