ASA ASA (acrylonitrile styrene acrylate)

ASA is a close relative of ABS that was developed for outdoor products. The key difference is the rubber phase: ABS uses butadiene rubber, which sunlight breaks down, while ASA uses an acrylate rubber that is far more resistant to UV. In everyday terms, you get ABS-like toughness and heat tolerance in a material that holds its color and strength outside. You will find molded ASA on car mirror housings, exterior trim, garden equipment and building products.

For printing, ASA behaves much like ABS. It shrinks as it cools, so it needs a closed chamber to avoid warping and layer splitting, and QIDI marks ASA as requiring a closed chamber in its filament guide. Prusa's materials guide notes that, compared with ABS, ASA is more UV resistant, warps less and does not smell as much, which matches our experience on QIDI printers with an active chamber at up to 65 °C.

ASA costs about the same as ABS. It is our default for any part that will live outdoors: mounts, enclosures, garden and marine fittings, signs, and vehicle exterior accessories. If you need more stiffness and heat resistance on top of weather resistance, ASA-CF is the step up.

ASA is a tough, moderately stiff plastic. QIDI lists a bending strength of 64.49 MPa along the layers for its ASA, and Polymaker's ASA datasheet gives a tensile strength of 43.8 MPa along the layers and a notched Charpy impact strength of 10.3 kJ/m². It is not a high-strength engineering material like nylon or PC, but it is more than strong enough for brackets, housings and clips that are sized sensibly.

Between layers it is weaker, as every FDM material is. QIDI gives 27.87 MPa tensile strength in the Z direction, and Polymaker gives 32 MPa in Z against 43.8 MPa in XY. That gap is why orientation matters: we lay a part out so its main load runs along the layers. Anisotropy, the technical name for properties that change with direction, is normal in FDM parts and something we plan around.

ASA resists creep better than PLA and PETG at warm temperatures, which is important for outdoor parts that sit in the sun all afternoon while clamping or holding something. Like ABS, it is notch-sensitive, so sharp internal corners and thin necks are the usual failure points. Fillets and thicker sections do more for reliability than anything else.

Heat deflection temperature (HDT) is the temperature at which a standard test bar bends a set amount under a set load. QIDI lists 93 °C at 0.45 MPa for its ASA, as printed. Polymaker lists 103 °C at 0.45 MPa and 100 °C at 1.80 MPa, and Prusa's guide describes ASA as resisting temperatures up to 93 °C without stating the load. That puts ASA slightly above ABS in heat resistance and well above PLA and PETG.

QIDI does not generally recommend annealing ASA, and we do not anneal it. For a loaded part, design with a clear margin below these values, because sustained stress causes creep at lower temperatures than the short-term test. Very dark colors in strong sun run noticeably hotter than light ones, which is worth considering for outdoor parts.

ASA's acrylate rubber phase is far more resistant to ultraviolet light than the butadiene rubber in ABS, which is why ASA keeps its toughness and color outdoors. Prusa's guide states ASA is more UV resistant than ABS, Prusament markets its ASA as UV stable and great for outside use, and Polymaker describes improved weather resistance over ABS. QIDI also sells its ASA as a UV-resistant outdoor filament.

None of these manufacturers publishes a lifetime in years, and real results depend on color, thickness, climate and sun exposure. Pigmented and darker colors usually hold up better than natural or white. For a critical outdoor part, a pilot part left in place for a season is the most reliable test, and a clear UV-resistant coating can extend the cosmetic life further.

Prusa's guide notes that ASA dissolves in acetone, so keep acetone-based cleaners and nail polish remover away from it. Gasoline, many chlorinated solvents and strong acids generally attack it too. Polymaker rates its ASA as good against weak acids, weak alkalis and oils and greases, fair against strong alkalis and poor against strong acids.

Common outdoor exposures such as rain, garden water, mild detergents and road grime are generally fine. Sunscreen, insect repellent and some brake fluids can mark or stress-crack styrenic plastics. If your part will meet a specific chemical, tell us and we will suggest a test piece.

ASA absorbs very little water. QIDI lists a saturated water absorption of 0.3% and marks drying as optional, though it gives 70–80 °C for 4–6 hours for spools that have picked up moisture, and Prusa notes ASA is slightly hygroscopic. We dry it before demanding jobs for the cleanest surface.

Printed ASA parts are dimensionally stable in rain and humidity, which is part of why it works so well outdoors. They will not swell like nylon. Water trapped inside a hollow part can freeze and crack it, so let us know if a part needs drainage or should be printed fully solid.

As printed, ASA has a smooth, satin-to-matte surface with visible layer lines, very similar to ABS. Colors are typically rich and even, and QIDI notes its black ASA uses a controlled pigment level to keep its performance balance.

ASA sands easily wet or dry, according to Prusa, and takes primer and paint. For outdoor parts, many buyers leave ASA unpainted because the color is already UV-stable, which avoids paint peeling later.

Sanding and painting: ASA sands cleanly and takes plastic primers and outdoor paints well. A primed and sanded finish hides layer lines on visible faces; ask for it on your quote.

Bonding: like ABS, ASA can be solvent-welded with acetone, which lets us join large parts printed in sections. For mixed-material joints, a structural adhesive suited to styrenic plastics is the better option.

Smoothing: ASA can technically be vapor smoothed, but it isn't a finish we offer for ASA. If you need a glossy surface on an outdoor part, ask us about sanding and a clear coat instead.

Threads and inserts: brass heat-set inserts work very well in ASA and are our recommendation for any thread used more than a few times. For outdoor use, stainless or brass hardware avoids rust stains on light colors.

ASA shrinks as it cools, a little less than ABS according to Prusa's guide, so large parts can come out slightly smaller than the model and long flat faces may bow slightly. The heated chamber keeps this under control, but very large thin plates are still the most difficult shape.

Holes and slots tend to print slightly undersized. For bearings, pins and press-fits, either design a little clearance or let us drill or ream holes to size after printing. If a few dimensions are critical, mark them on your drawing so we can orient the part to protect them.