Why 3D prints warp, lift at the corners and delaminate

Where warping comes from

Plastic leaves the nozzle at 200-260 °C and cools to room temperature. As it cools, any 3D printing plastic contracts: ABS by roughly 0.6-0.8 %, PLA barely at all. Fractions of a percent sound trivial, but on a 20 cm part that is already millimetres, and all of that shrinkage turns into internal stress.

The bottom layers are stuck to the bed and cannot contract freely; the layers above shrink without restraint. The part behaves like a loaded spring: the stress pulls the corners upward, and the moment it beats the grip on the bed, a corner lifts. If the weak point is not bed adhesion but the weld between layers, the part cracks mid-height instead - that is delamination.

Which materials warp most

• PLA barely shrinks: it prints on a cold or slightly warm bed (20-60 °C) and needs no enclosure - trapped heat only stops the part cooling.
• PETG sits in the middle: bed at 70-90 °C; an enclosure is optional but helps large parts.
• ABS and ASA contract by the same 0.6-0.8 % and want a 100-110 °C bed and an enclosure.

The full settings live in the material guides: PETG, ABS, ASA.

What keeps the corners down

• A hot bed. Warm bottom layers contract less, so the stress at the bed line stays small. Take the bed temperature from the material guide rather than adding a bit extra just in case.
• An enclosure and a room without draughts. An open window, an air conditioner or a fan next to the printer cools one side of the part faster than the other, and the shrinkage becomes uneven. For PLA a still room is enough; for ABS and ASA only an enclosure keeps the air stable.
• A brim. A few extra perimeters around the first layer give each corner more area to hold onto. It peels off in seconds after the print and costs almost nothing.
• Cooling set per material. PLA prints with the part cooling fan at full power, PETG with moderate cooling at 30-50 %, ABS and ASA with minimal cooling or none at all. Blasting a shrink-prone plastic with air only feeds the stress.

Delamination: the same shrinkage, a different weak point

When the corners hold but the part splits along a layer line, the shrinkage found its way out through the weld between layers. The usual causes:

• Too much cooling. On PETG at full fan the layers bond poorly and the part delaminates; drop it to 30-50 %.
• A draught chilling each layer before the next one lands. On ABS the fix is an enclosure and no part cooling at all.
• Damp filament. Moisture boils in the nozzle, the extruded thread comes out with bubbles, and each weld ends up with less plastic in it. Drying: PETG for 6-8 hours at 60-65 °C, ABS and ASA for 4-6 hours at 65-70 °C.

Why a big ABS part needs a chamber

Shrinkage is a percentage: the bigger the part, the more millimetres it loses and the more stress it stores. Something under 5 cm will print on an open machine; a 20 cm housing without a chamber is almost certainly scrap. An enclosure keeps the air around the part warm and even, so the finished print cools as one piece instead of fighting itself layer by layer.

If you have no enclosure

Often the right move is not to fight ABS but to print the part in PETG: it is strong enough for most brackets and housings and warps far less. The short material helper narrows the choice for a specific part, the compare page puts the settings side by side, and the filament itself is in the catalog.