ABS vs ASA for Printing: Settings, Strength and Fumes

The short answer on abs vs asa for printing: choose ASA for anything that will see sunlight, and treat it as your default whenever the printer is enclosed. It prints at almost the same settings (Prusa lists a 255 °C nozzle for ABS and 260 °C for ASA), matches ABS on heat resistance, holds up far better under UV and emits less styrene. ABS still earns a spool for indoor parts where impact toughness or price decides it.

The two are close relatives: a styrene-acrylonitrile matrix toughened with a rubber phase, differing only in which rubber. That one swap explains nearly everything below, and it is why moving from ABS to ASA is a profile tweak rather than a new workflow.

ABS vs ASA at a glance

Settings, warping and UV rows come from the Prusa ABS and Prusa ASA knowledge base pages. Thermal and mechanical rows compare the PolyLite ABS data sheet with the Polymaker ASA data sheet: same vendor and ISO test methods, different product lines, so read the gaps as indicative.

Why does ASA survive sunlight when ABS does not?

ASA survives sunlight because its rubber phase has no carbon-carbon double bonds for UV and oxygen to attack. ABS toughens its matrix with polybutadiene, which is unsaturated; ASA uses an acrylate rubber, which is not. Formerra’s ASA documentation states the acrylate backbone “does not react with UV radiation or oxygen through the photooxidation pathways that degrade ABS.”

The consequences are large. Formerra reports that under ASTM G155 xenon-arc weathering, standard ASA grades keep more than 80% of their initial impact strength after 2,000 hours, with colour shift typically under a Delta E of 2, while ABS keeps 20 to 30%. Those are injection-moulding resin figures, not printed parts, but they match what Prusa describes in plainer terms: ABS parts used outdoors “turn yellowish and more brittle over time.”

Printed-part data points the same way. In Sedlak et al., Materials, 2023, ABS and ASA from three manufacturers each were printed on Original Prusa i3 MK2S and MK3S machines (ABS at 240 °C, ASA at 250 °C, 110 °C bed) and left outdoors for 98 days. All three ABS brands lost tensile strength; Gembird ABS fell from 45.20 to 42.10 MPa. All three ASA brands held steady or rose slightly. The caveat: samples sat in a covered area through a Czech winter with an estimated 294 hours of sunshine. Given the chemistry, unshaded summer sun should widen the gap, not close it. For the ranking against PETG and PLA, see best filament for outdoor use.

Is ASA stronger than ABS?

ASA is stiffer and higher in tensile strength, but ABS is tougher, at least on the one vendor’s data sheets that test both the same way. Polymaker lists 43.8 MPa X-Y tensile strength for its ASA against 33.4 MPa for PolyLite ABS, yet gives the ABS 18.0 kJ/m² notched Charpy impact against 10.3 kJ/m², and 17.9% elongation at break against 6.7%.

That split should drive part selection. A snap-fit clip, or a part that takes knocks from tools, favours the material that stretches before it cracks, and in this pair that is ABS. A stiff mount carrying a steady load favours ASA.

Layer adhesion is the other number worth reading. The ASA sheet gives 32 MPa in Z, which is 73% of its X-Y figure. PolyLite ABS gives 29.7 MPa in Z, 89% of its X-Y figure. ASA is still slightly stronger across layers in absolute terms, but it loses more going from in-plane to cross-layer loading. Orient ASA parts so the main load runs along the layers.

Brand variation can outweigh the material choice. In the Sedlak study, baseline ABS tensile strength ran from 37.20 to 45.20 MPa across three brands, while Plasty Mladeč, the one maker that supplied both, measured 37.20 MPa in ABS and 46.20 MPa in ASA.

Do ABS and ASA print differently?

Barely. Both want a nozzle in the mid-250s, a bed near 100 °C, little or no part cooling, glue stick on PEI, and a warm enclosure. Prusa describes ABS as the predecessor of ASA, with more warping and more odour during printing. In practice ASA is the slightly more forgiving of two demanding materials, not an easy one.

A starting profile for Polymaker ASA on an enclosed printer with a 0.4 mm nozzle:

• Nozzle: 250 °C, inside Polymaker’s 230–260 °C window. Move toward Prusa’s 260 °C if layers split.
• Bed: 95 °C on textured PEI with glue stick. If corners lift, try Prusa’s 105 °C first layer and 110 °C after.
• Part cooling: 0% per Polymaker, with a little fan on bridges only if they sag.
• Speed: inside Polymaker’s 50–200 mm/s range; slow the outer wall first if you see ringing.
• Chamber: heat-soak the closed enclosure with the bed on for 10 to 15 minutes. Ambient temperature, not nozzle temperature, is what stops warping.
• No enclosure: Prusa suggests PrusaSlicer’s draft shield as a partial substitute. It helps small parts, not large flat ones.

One note from Prusa’s ASA page: never put acetone on a powder-coated sheet, even though acetone is how you smooth and bond ASA parts.

Which one is worse for fumes?

ABS is worse, by a clear margin in the one direct comparison, but ASA is not a low-emission material. Wojnowski et al., Molecules, 2022 measured VOCs in real time inside a printer enclosure with both materials at 240 °C. Styrene dominated for both, and the ASA’s styrene emission rate “was less than a quarter the emission of styrene from ABS.”

That comparison used one brand of each, Nebula Filaments ABS and Print-Me ASA, so treat the ratio as a single data point. The authors note styrene is classified by IARC as “probably carcinogenic to humans” (Group 2A) and suggest nylon and PETG where ventilation cannot be assured. Prusa flags potentially dangerous styrene fumes as a drawback of both materials. Switching to ASA reduces exposure; it does not remove the need for an enclosure with filtration or a vent to outside.

When is ABS still the better pick?

ABS is the better pick for indoor parts that need impact toughness and elongation, for high-volume runs where filament cost adds up, and when a colour or grade you need is only sold in ABS. On price, Formerra puts ASA resin at a 15 to 30% premium over comparable ABS grades. Filament pricing varies by brand, so compare the actual spools you would buy.

Two common reasons to pick ABS do not hold up:

• Acetone smoothing. Prusa documents acetone vapour smoothing for both. ASA also accepts acetone welding and polishes to an injection-moulded gloss.
• Heat resistance. Polymaker’s heat deflection temperatures are 98 °C for PolyLite ABS and 100 °C for its ASA, and Prusa rates ASA to 93 °C. Either one comfortably clears PLA, which Prusa says “gets soft and deforms at temperatures over 60 °C.”

If the printer is open-frame and sits in a living space, the honest answer may be neither. PLA vs PETG vs ABS covers when PETG does the job without the enclosure and fume overhead.

How to verify the choice on your printer

Three short prints separate material problems from setup problems before you blame a spool.

1. Warp bar. Print a flat bar about 150 × 20 × 5 mm in each material, 4 walls, 20% gyroid, no brim, same heat-soak. Success: both ends still flat after the part cools on the bed. If both lift, the problem is chamber temperature, not material.
2. Temperature tower. Span the exact spool’s data-sheet range in 5 °C steps. Pick the lowest step where bridges stay clean and the tower resists snapping across layers.
3. Layer-adhesion snap. Print a single-object vertical wall, 2 perimeters wide and 60 mm tall, and break it by hand. Success: a jagged fracture. A clean break along one layer line means the nozzle is too cold, the fan too high or the chamber too cool.

If a spool that printed cleanly last month now pops or strings, check for moisture before touching settings: the wet filament symptoms guide covers diagnosis and the drying chart by material covers the fix.

FAQ

is asa harder to print than abs

No, ASA is usually slightly easier. Prusa describes ABS as the predecessor of ASA with more significant warping and more odour during printing. Both still warp enough that an enclosure matters, and ASA runs a few degrees hotter, with Prusa’s profile at a 260 °C nozzle and a 105 to 110 °C bed.

can you print asa without an enclosure

Small ASA parts can print on an open-frame machine, but large ones generally cannot. Prusa calls an enclosure necessary for large parts and suggests PrusaSlicer’s draft shield as a fallback, while Polymaker lists a closed chamber as needed. Without one, expect corner lift and layer splitting, and you still need ventilation for the styrene.

can i use my abs profile for asa

Yes, an ABS profile is a sound starting point for ASA. Prusa’s profiles differ by only 5 °C at the nozzle (255 against 260 °C) and 5 to 10 °C on the bed. Start there, then run a temperature tower, because Polymaker’s ASA range of 230 to 260 °C sits below its 245 to 265 °C ABS range.

does asa need to be dried before printing

Yes, dry ASA if the spool has been open, since Prusa lists it as partially hygroscopic. Prusa recommends 80 °C for 4 hours; Polymaker specifies 70 °C for 7 hours for its ASA and 70 °C for 6 hours for PolyLite ABS. Wet spools pop, string and print weak layers that look like a material fault.