PLA warping: how to fix corners lifting off the bed

If only the corners lift and the middle of the part stays down, that is warping: the part is pulling itself up. If the whole part comes loose, or the first strand never sticks, it is a different problem, covered in the guide to a first layer that won't stick. The difference matters because with warping, the fix is to reduce shrinkage and give the corners more area to hold on with.

Why the corners lift

Plastic leaves the nozzle at around 200 °C or more and shrinks as it cools. Each new layer goes down hot on top of one that has already cooled, and as it shrinks it pulls the layer below inward. In the middle of the part that pull is spread out; at the corners it adds up from two directions and beats the adhesion. The corner rises, the base curves, and in bad cases the nozzle hits the raised corner and knocks the part off.

Three things make the pull stronger:

• Fast or uneven cooling: drafts from a window, a fan or air conditioning, and a strong part fan on the first layers. Bambu Lab notes that with the room below 20 °C, even PLA and PETG warp.
• Geometry: long, flat parts and sharp corners concentrate stress.
• High infill: Bambu Lab gives large parts at 60% infill as a typical case, and infill patterns made of straight lines shrink more than Gyroid.

PLA, PETG, ABS and ASA: which warps most

Bambu Lab classes PLA, PETG and TPU as not prone to warping, and ABS, ASA, PC and nylon as materials that need a hot bed and a warm chamber to avoid it. Among the easy ones, PETG warps more than PLA. Materials that set at a higher temperature have further to shrink on the way down to room temperature, which is why they need more heat around the part.

Ranges from Bambu Lab's filament table, checked November 2026. If you are still picking a material, the PLA vs PETG guide compares the two.

Is it really warping?

During the print, shine your phone's flashlight along the bed and watch where the gap starts. Then, with the finished part cold, set it on a flat surface and try to slide a sheet of paper under the corner: that measures how bent it ended up, but not when it started.

What each test costs

Use the part itself if it's small, or a 100 × 20 × 10 mm bar. A comparison only counts against a control version: same spool, same spot on the bed, one change at a time. Always measure the gap with the part cold. If the bar comes out flat with nothing changed, it's no use for comparing: test on the part that warped.

We sliced the bar in Bambu Studio with the A1's 0.20mm Standard profile and generic PLA:

These are slicer estimates. We did not print these bars: the table shows what each test costs, not how it turns out.

Cause by cause: how to confirm

Grease on the sheet

What it looks like: the corner lifts in the first layers, often in the same area of the bed.

Test that confirms it: wash the sheet with dish soap, dry it and print the same part in the same spot. If the gap shrinks, the cleaning helped. On a smooth sheet, water beading up is a good sign of grease; on a textured one it's only a weak clue.

Wrong plate in the slicer

What it looks like: it starts after you change the sheet or open someone else's project.

Test that confirms it, without printing: compare the sheet that's installed with the one in effect for that plate of the project, because the plate's own setting overrides the general one. When the print starts, check the bed's target temperature on the screen. The right temperature doesn't prove the right plate, because two types can use the same value.

Cold bed

What it looks like: the base starts out fine and the corners lift later.

Test that confirms it: check the profile's temperature. On the A1, generic PLA on the textured sheet already comes at 65 °C, the top of the range, so this test doesn't apply. On the X1C, PLA Basic comes at 55 °C: in that case, print the same part 10 °C hotter, changing only that. If the gap shrinks, bed heat was a factor.

Cold room

What it looks like: the same part comes out fine on warm days and warps on cold ones.

Test that confirms it: with a thermometer near the printer, compare the same part, with the bed on the same setting, at two measured temperatures, such as morning and afternoon. If it only warps in the cold, the room is a factor. Bambu Lab names 20 °C as the point below which even PLA and PETG warp.

Fan on too early

What it looks like: the corner lets go in the first layers, even on a clean sheet.

Test that confirms it, starting without printing: in the preview, choose Color Scheme Fan speed and look at the layers where the corner lets go. With PLA on the A1, only the first layer comes with the fan off: on the bar, the second was already at 72%. Change only No cooling for the first to 3 and check that the preview changed on those layers. If it didn't, you've just repeated the control, as happens with generic PETG, which already comes with 3. Print and compare. If the gap shrinks, the fan was a factor.

A draft, or something on one side of the printer

What it looks like: the same side always warps.

Test that confirms it: note which side lifted and print the part rotated 180° in the slicer, in the same spot on the bed. If the same side of the printer keeps lifting, look at the surroundings or the bed. If the problem changed sides along with the part, look into the geometry and the toolpath. To tell a draft from the bed, remove one direct airflow at a time, without shutting off the room's ventilation, and repeat. If it goes away, it was that airflow. If it stays, clean that area and check the leveling.

Sharp corners on a long, flat part

What it looks like: both ends lift equally, anywhere on the bed.

Test that confirms it: if you have the model, change only the corner radius and compare. If the gap shrinks, the sharp corner was a factor. Without the model, try a brim: if it holds, it's a good fix, but it doesn't prove the cause. If the brim lifts too, shrinkage is still beating adhesion, and it's worth going back to the sheet and the bed.

Fast first layer

What it looks like: the line drags or peels on curves and corners, before the part has grown.

Test that confirms it: set the first layer and its infill to 30 mm/s, check in Color Scheme Speed that the preview changed on that stretch, and compare with the control.

High infill

What it looks like: a thick, solid part with corners lifting late, when it's already tall.

Test that confirms it: repeat changing only the density, with the same pattern. If the gap shrinks with less infill, it was a factor. This is the most expensive test, so leave it for last.

Moisture in PETG

What it looks like: popping, bubbles or strings, along with the corner lifting.

Test that confirms it: note the popping, the strings and the gap separately. Print the same part from the same spool before and after drying it. Less popping and fewer strings show it was wet. To tie moisture to warping, the gap has to shrink again when you repeat.

ABS and ASA without heat around them

What it looks like: the part lifts even with everything else checked.

Test that confirms it: on a compatible printer, print from the same spool with the bed already stable, at two chamber temperatures measured with a thermometer. If the gap shrinks with the warmer chamber, the part was missing heat around it.

What order to test in, to spend little

1. Without printing: the installed sheet against the project's, the profile's temperature, fan and speed in the preview.
2. One print at a time, against the control: washed sheet, then fan, then first layer at 30 mm/s.
3. Side of the printer: rotate the part 180°.
4. Geometry: a corner radius, if you have the model; otherwise a brim, which is a fix.
5. Last: infill, room temperature and, for PETG, drying.

Fixes, from most to least effective

1. A clean sheet, and the right plate in the slicer. Grease costs you adhesion right at the corners. Wash with dish soap and warm water and check the plate type in the slicer: picking the wrong plate can leave the bed cooler and the nozzle higher than they should be.
2. Bed near the top of the material's range. In a room below 20 °C, Bambu Lab suggests 10 °C more, without going past the maker's range (too hot a bed causes elephant's foot and, with PLA and PETG, can clog the nozzle).
3. Part fan off for the first three layers (No cooling for the first in Bambu Studio, Disable fan for the first in PrusaSlicer). If your printer has a side auxiliary fan, Bambu Lab suggests lowering it to 40% to 50% when parts warp. In the PLA profiles we read (A1 and X1C), the fan only comes off for the first layer; in the A1's generic PETG, for three.
4. Brim. The one-layer flange adds area holding the base down. If the corners still lift, make it wider.
5. Mouse ears at the corners. These are thin discs only at the corners, holding where the pull is strongest and coming off more easily than a full brim. In Bambu Studio, set Brim type to Painted and use the Brim ears tool; OrcaSlicer has a Mouse ear brim type; in PrusaSlicer and Cura you can add cylinders a few layers tall at the corners, which is what Prusa suggests when a brim is not enough.
6. Protection from drafts, and heat around the part. For PLA and PETG, get the printer out of moving air; Prusa advises against printing those two in a hot enclosure, because they need cooling. For ABS and ASA, an enclosure is what works. Without one, a draft shield (a skirt wall as tall as the part, in PrusaSlicer, OrcaSlicer and Cura) holds in some heat.
7. Slower first layers. Prusa recommends slowing down so layers bond better; for the first three layers, about 75% of normal speed. In the A1, X1C and P1P 0.20mm Standard profile, the first layer comes at 50 mm/s and its infill at 105 mm/s.
8. Parts in the middle of the bed, and moderate infill. Prusa suggests turning the problem areas toward the center of the bed. For structural parts, Bambu Lab suggests 5 walls with about 25% infill rather than going above 50%.
9. Dry PETG. Bambu Lab lists moisture as a cause of poor adhesion and warping with PETG. See how to dry wet filament.

Bambu Lab and Prusa pages checked November 2026.

In the design: rounded corners

If you are the one designing the part, the design helps more than any setting:

• Round the corners as seen from above. A sharp 90° corner concentrates the pull from two sides; a radius of a few millimeters spreads the force along the curve.
• Careful with bottom chamfers. A small chamfer on the bottom edge hides elephant's foot, but a large one removes contact area right at the corner, where it is needed most.
• Split long, flat parts into smaller pieces when the use allows them to be joined or glued.

What a warped part costs

An example, with stated assumptions: a PLA box with a 100 × 60 mm base, 160 g and 8 hours of printing, using the calculator's reference values (PLA at $20/kg and a machine hour of $0.17, which adds up $0.02 of electricity at 120 W and $0.17/kWh, $0.10 of wear on a $600 printer with a 6,000-hour life, and $0.05 of maintenance).

The brim math: a 5 mm flange around 100 × 60 mm covers about 1,700 mm²; at 0.2 mm high that is 0.34 cm³, or 0.42 g of PLA. With a 0.42 mm line at 20 mm/s, it takes a little over 3 minutes. For the canceled part, we assume filament is used evenly over the print. On top of that comes your time to remove the part and restart and, if it was an order, a late delivery.

Frequently asked questions

Why does only one side of the part warp?

A typical cause is cold air hitting one side only: a window, a fan, air conditioning or the printer's own side auxiliary fan. Move the printer or turn the auxiliary fan down. If the same side warps on different parts, also check the leveling and cleanliness of that area.

Does a hotter bed always help?

Only up to the material's limit. Above the maker's range, the base spreads out (elephant's foot) and, with PLA and PETG, heat rising from the bed can soften the filament before the nozzle and cause a clog. Bambu Lab recommends opening the door of an enclosed printer when the bed is above 45 °C with PLA and above 70 °C with PETG.

Does a raft fix warping?

It helps on an uneven bed or one without PEI, because the part then sits on a thick, well-stuck base. On clean PEI, a brim and mouse ears are usually enough and use much less material. In exchange, a raft leaves a rough bottom.

The brim leaves a mark on the part. How do I avoid it?

Use mouse ears only at the corners instead of a full brim, or increase the Brim-object gap in Bambu Studio and OrcaSlicer so it comes off more easily. A hobby knife cleans up whatever is left on the edge.

My PETG warped even with the bed at 80 °C. What else could it be?

Check whether the filament is wet, whether the fan is off for the first layers and whether there is a draft. On enclosed printers with strong ventilation, Bambu Lab names cold air blowing straight onto the part as a cause of warping with PETG.