Warping in 3D printing — 6 causes of print corners lifting

Symptom: the print starts correctly, but after a dozen or several dozen layers the corners peel off the bed and curl upwards. The base of the model stops being flat, the side walls go out of square, and in the worst case the nozzle catches the lifted edge and knocks the whole print off.

Warping is the result of thermal shrinkage. Every freshly laid layer cools and contracts, pulling on the layers below it. As long as that stress stays lower than the adhesion force to the bed, nothing happens. Once the accumulating stress exceeds it — and it happens first in the corners, where the material shrinks in two directions at once — the edge simply lets go. That is why warping is always a temperature difference problem, not a calibration problem. PLA barely does it. ABS, ASA and PC/ABS will always do it if you let them.

The most common causes and fixes

1. The bed temperature is too low

A warm bed keeps the bottom of the print above the temperature at which the plastic stiffens. The material stays soft and dissipates stress instead of storing it. A bed that is 10–15 °C too cold is enough to make ABS curl its corners by the tenth layer.

How to check: don’t trust the reading on the screen. The thermistor sits under the bed, and the real surface temperature can be more than ten degrees lower, especially on glass and at the edges of the plate. Measure the surface with an IR thermometer or a thermocouple.

What to do: set the temperature in the upper half of the range for the material and give it longer to heat up before the start. With ASA and PC/ABS go straight to the top values — don’t experiment with the bottom ones.

2. No enclosure for ABS, ASA and PC/ABS

A heated bed on its own only heats the base. The tenth layer is already out of its reach and cools to room temperature while the first layer sits at 100 °C. That difference is the entire cause of warping. An enclosure removes it, because it holds the whole chamber at an even temperature.

What to do: for ABS, ASA and PC/ABS the manufacturer states it plainly: a closed frame at 50 °C. You don’t need active heating for that — a closed box around the printer warms up on its own from the bed and the hotend heater. What matters is giving the chamber 10–15 minutes to even out before the start.

Note: an enclosure raises the temperature of the electronics and the motors. Move the controller outside or give it its own cooling. Remember too that ABS and ASA have a strong smell — an enclosure makes it easier to extract the fumes, but it does not remove them.

Porima material	Bed temperature	Enclosure	Fan
PLA and PLA variants	0–60 °C	open	100%
PLA/CF	50–70 °C	open	60–100%
PETG	60–80 °C	open	100%
HT PETG	100–120 °C	closed or open, adhesive recommended	0–10%
ABS	80–110 °C	closed, 50 °C	0–40%
ASA	90–120 °C	closed, 50 °C	0–30%
PC/ABS	100–120 °C	closed, 50 °C	0–30%
PA (nylon)	90–120 °C	closed, heated	30–100%, first 5 layers off
HIPS	80–110 °C	open	100%, can be reduced
TPU Flex 98A	40–60 °C	open	40–70%

Source: the manufacturer’s official Porima FDM technical data table. Full listing: printing temperature chart.

3. A draught over the printer

An open window, air conditioning, a fan standing in the room or a printer placed next to a door — any stream of cold air cools one side of the print faster than the other. The effect is unmistakable: only the side of the model facing the draught lifts.

What to do: close the window and move the printer out of the traffic route. If you have no enclosure, a temporary cardboard screen or a plastic tent is enough. It is the cheapest fix on this list and often the only one needed with PETG.

4. Model geometry: a large flat base and sharp corners

Shrinkage stress accumulates along the length of a wall. A model with a 200 mm base will warp incomparably more easily than the same shape with a 40 mm base, and a sharp 90° corner concentrates all of that force at a single point. Thin, tall walls without ribs are the second classic case.

What to do: round the corners of the base or add chamfers to them — a radius of a few millimetres is enough to spread the stress. If you can’t change the model, rotate it so the longest dimension is not lying on the bed, or split the print into parts and glue them afterwards. "Mouse ears" — flat discs added at the corners of the base — help too.

5. The part cooling fan runs too hard at the start of the print

Cooling improves detail quality, but on the first layers it acts exactly like a draught — only from a few millimetres away. Many stock profiles switch the fan to full power from the second layer, which with technical plastics is a straightforward recipe for lifted corners.

What to do: stick to the ranges in the table above. For ABS and ASA the upper limit is 40% and 30% respectively, not 100%. For nylon the manufacturer recommends cooling switched off completely for the first five layers. With PLA and PETG you don’t need to limit anything beyond the first layer itself.

6. Too small or unsuitable an adhesion area

The larger the contact area with the bed, the more stress is needed to break it. A model standing on four narrow feet stands no chance in ABS, even inside an enclosure.

What to do: turn on a brim 5–10 mm wide; on difficult models increase the number of brim lines rather than its width. Look after the surface itself as well: a clean PEI sheet, or glass with a thin layer of glue stick, holds far better than a plate somebody has run their fingers over. With HT PETG the manufacturer explicitly recommends using adhesive as an intermediate layer.

Which materials are most at risk

The manufacturer classifies the tendency to warp as high for the whole ABS family — that covers ABS, Eco ABS, ABS/CF and PC/ABS. These plastics do not forgive printing in an open printer, whatever your slicer settings. ASA also requires a closed frame at 50 °C, although the manufacturer classifies its tendency to warp as medium rather than high.

PLA and its variants sit at the other end of the scale — the shrinkage is small enough that a cold or barely warm bed will do. PETG is in the middle: it rarely warps noticeably, but on large flat parts and in a draught it can catch you out. HT PETG is a case of its own — it runs at bed temperatures of 100–120 °C with the fan almost off, and its manufacturer-declared temperature resistance reaches 125 °C. Nylon needs a heated chamber and mandatory drying before printing, because absorbed water adds its own set of problems on top of warping.

Related problems

• The first layer won’t stick — if the material comes away immediately rather than after a dozen layers, start here.
• Delamination — the same shrinkage stress, only released inside the wall.
• Dimensional accuracy and shrinkage — why ABS parts come out smaller than the model.
• Elephant’s foot — a splayed base caused by too hot a bed.
• Smell and fumes — the practical consequence of printing ABS and ASA in a closed chamber.
• Wet filament — worsens layer cohesion and indirectly makes warping worse.