Why do ABS and ASA prints crack between layers?

Prusa's layer-separation guide says ABS cracks when cold air hits the print, and it says to turn the part fan off. Prusa's ABS guide lists a nozzle of 255 °C (491 °F) and a bed of 100 °C (212 °F), with the bed allowed from 80 to 110 °C (176–230 °F) as the part gets larger, inside an enclosure so the air stays warm. A draft does the damage. The fan and an open room are the usual drafts.

What splits the layers

Prusa's layer-separation article, read 28 October 2026, says the layers crack when they cool at different rates and the pull is stronger than the bond. A clean break with a slight upward bend is how it says to tell a crack from a missing layer. For ABS it says any cold air on the print, including the part fan, is enough, and it says to turn the fans off. It says ABS is best in an enclosed chamber. PETG is the substitute it names when the part is large, because PETG is less likely to crack. ASA still wants stable air, on that page.

The same article says PLA can split when the nozzle is too cool, and it gives a brand-dependent band of 195–220 °C (383–428 °F) with 5 °C (41 °F) steps upward. That band is Prusa's troubleshooting range. It is not the PolyLite PLA sheet.

The ABS guide lists a nozzle of 255 °C (491 °F) and a bed of 100 °C (212 °F), and it says the bed can sit from 80 to 110 °C (176–230 °F) as the object gets larger. It says to keep the room free of a draft while still ventilating fumes, to keep the ambient temperature high, and to put the printer in an enclosure. Without an enclosure it says to turn on a draft shield in PrusaSlicer. An enclosure is that box. ABS fumes is the ventilation page.

The fan article says ABS and ASA profiles leave the fan off for the first four layers and then run it near 15 to 20 percent, a bit higher on bridges. When the part is cracking, the layer-separation article is the one that says off.

Filament sheets

PolyLite ABS stores 230–260 °C (446–500 °F) and a bed of 90–110 °C (194–230 °F). Prusa's 255 °C (491 °F) and 100 °C (212 °F) point sits inside that band. Heat deflection is 100 °C (212 °F) at 0.45 MPa and 98 °C (208 °F) at 1.8 MPa, and glass transition is 101 °C (214 °F), checked 21 October 2026. Glass transition is where the plastic softens. Drying is 70 °C (158 °F) for 6 h.

PolyLite ASA stores 230–260 °C (446–500 °F) and a bed of 75–95 °C (167–203 °F). Heat deflection is 103 °C (217 °F) at 0.45 MPa and 100 °C (212 °F) at 1.8 MPa, and glass transition is 98 °C (208 °F). A 100 °C (212 °F) bed matches Prusa's ABS line and passes this datasheet bed. Do not treat 100 °C (212 °F) as the ASA sheet.

Bambu ABS stores 230–260 °C (446–500 °F) and a bed of 90–110 °C (194–230 °F), and drying at 80 °C (176 °F) for 8 h.

How to print ABS, how to print ASA, layer adhesion, and warping are the neighboring pages. Cooling is the fan in general.

What the community says

A comment in a Reddit thread in r/ElegooNeptune4 says cooling an ASA print too fast after it finished created enough stress to break the part.

A comment in a Reddit thread in r/ElegooNeptune4 says ASA warps unless the air around it stays warm, and that a draft barrier can be enough for a small part that is not flat.

A comment in a Reddit thread in r/ElegooNeptune4 says brittle ASA came from moisture in the filament, and that dry ASA was tough.

Questions