ASA filament, ranked by £/kg

ABS that survives outdoors

ASA was developed as a UV-stable alternative to ABS, and that is precisely what it is: the same broad toughness and heat resistance, but it does not yellow and go chalky after a summer in the sun. For anything that lives outside — garden fittings, sensor housings, bike and car parts, aerial mounts — it is the default choice.

It also warps slightly less than ABS and tends to smell less while printing, though neither difference removes the requirements below.

The same requirements as ABS

An enclosure is effectively mandatory for anything larger than a small part, and ventilation is still needed — ASA emits the same class of fumes and particles as ABS while printing. Treat the two identically on safety.

Settings to start from

Nozzle 240–260 °C, bed 90–110 °C, cooling off or minimal, enclosure closed and up to temperature before starting anything large. Draughts are the main cause of mid-print layer splitting, so keep it away from open doors and windows.

Use a brim on large footprints, and slow the first layer down. A standard brass nozzle is fine; unfilled ASA is not abrasive. What matters far more is the enclosure — see enclosed versus open-frame printers.

When ASA is the wrong choice

• Open-frame printer, no enclosure. Do not buy it. A small part may survive; anything with a footprint will lift or split. PETG is the outdoor-tolerant material you can actually print on an open machine.
• No ventilation. Same answer: PETG.
• Indoor parts only. ABS does the same job and is usually cheaper, and acetone smoothing works better on it.
• Fine detail or display work. Warping and the lack of cooling both count against ASA here; PLA is far better suited.
• Needs to flex. ASA is rigid. That is TPU territory.

Is it worth the extra over ABS?

ASA usually carries a small premium. If the part will ever see sunlight, that premium buys you the difference between a part that lasts years and one that becomes brittle and discoloured in a season — an easy decision. For an indoor part, ABS at a lower price is perfectly reasonable, though the price gap is often small enough that ASA is worth defaulting to. Compare the current figures here against ABS ranked by £/kg.

One practical note

ASA is worth keeping dry. It is not as thirsty as nylon, but damp ASA prints with a rough, bubbled surface that no amount of temperature tuning will fix.

How to read this table

The per-kilo column is the only number that compares listings honestly. A spool sold at 40% off can still be poor value, and a multi-spool bundle looks expensive until you divide by its total weight. We count bundles at their full weight, so a 4 × 1 kg pack and a single 1 kg spool sit on the same scale.

Where a listing does not state a usable weight we leave the per-kilo figure blank rather than guessing — a wrong ranking is worse than a missing one.