Why do the corners of my print lift?

It's warping: the plastic shrinks as it cools and pulls the corners up. It mostly happens with ABS, ASA and PETG. The fix is reducing the temperature difference between part and air: hot bed, no drafts and, for technical materials, an enclosure.

How often should I clean the print bed?

Whenever adhesion gets worse. The #1 cause of sudden failures is finger grease: just touching the surface leaves an invisible film that blocks adhesion. Wash it with hot water and soap (not just alcohol) every few prints.

Do I need hairspray, glue or tape?

On modern PEI beds, usually not: a clean, well-leveled bed is enough. Adhesives are a useful patch for difficult materials or old beds, not the root fix.

What does z-offset have to do with it?

A lot. If the nozzle sits too high on the first layer, the plastic isn't squished against the bed and won't grip; too low and it drags. The right z-offset leaves the first layer slightly squished and even.

Troubleshooting

Why your print won't stick to the bed (and how to fix it)

The #1 failure in FDM 3D printing: the first layer won't grip, or the part lifts mid-print, curling the corners. It's almost always one of these five causes. We go from most common to least.

1. The bed is dirty (the #1 cause)

The most frequent reason for sudden adhesion failure — you were printing fine and suddenly aren't — is a contaminated surface. Finger grease, dust or residue from old prints leave an invisible film that stops plastic from bonding. Fix: wash the flexible PEI sheet with hot water and dish soap, not just alcohol — alcohol redistributes grease rather than fully removing it. Handle it by the edges afterwards.

2. Bed not leveled / wrong z-offset

If the bed isn't flat or the nozzle sits at the wrong height on the first layer, the plastic isn't squished against the surface and won't grip. Modern printers with auto bed leveling solve most of this, but fine z-offset still matters: the first layer should be slightly squished and even, neither rounded (nozzle too high) nor transparent and dragged (too low).

3. The bed is too cold

Each material needs its bed temperature to adhere: too cold and the plastic cools before sticking. Reference: PLA 50-60°C, PETG 70-90°C, ABS 90-110°C. Raise it within the material's range if the first layer won't grip.

4. First layer printed too fast

If the first layer goes too fast, the plastic doesn't have time to melt against the bed and adhere. Fix: drop first-layer speed to ~50% of normal. Almost every slicer lets you set the first layer separately. It's one of the highest-impact, lowest-effort adhesion fixes.

5. Warping: the part lifts from shrinkage

If the part starts fine but the corners lift midway, it's warping: the plastic shrinks as it cools and that force pulls the corners up, detaching them. Typical of ABS, ASA and, to a lesser extent, PETG. The key is reducing the temperature difference between part and air:

Eliminate drafts (windows, AC) near the printer.
Use an enclosure: it traps waste heat and stabilizes ambient temperature, drastically cutting the thermal stress that causes warping. For ABS it's nearly essential.
Add a brim in the slicer: it increases bed contact area and anchors the corners.

Find your cause from the symptom

The five causes above leave different fingerprints. What the failure looks like usually tells you which one you have, so you don't change five things at once and learn nothing:

What you see	Most likely cause	Check first
It printed fine yesterday, today nothing sticks	Contaminated bed	Wash with soap and hot water
Sticks in the middle, not at the edges	Warped or uneven bed	Re-run auto levelling; check the sheet is flat
First layer looks rounded, like loose spaghetti	Nozzle too high	Lower z-offset in 0.02 mm steps
First layer is see-through and ridged	Nozzle too low	Raise z-offset; it's starving the extrusion
Only tall, thin parts fall over	Too little contact area	Add a brim; increase first-layer width
Corners lift hours into the print	Warping	Drafts, enclosure, brim
Only fails on one spot of the bed	Damaged or worn coating	Print elsewhere on the plate to confirm

If your symptom isn't here, our print troubleshooting guide covers other failures — ghosting, layer shifts, stringing, elephant foot — with the same approach.

Not all beds behave the same

Most advice online assumes a smooth PEI sheet, and that's why it sometimes fails you. The surface changes both the temperature you need and whether adhesives help at all:

Textured PEI (powder-coated): the most forgiving and the current default. It grips by mechanical keying, so it tolerates a slightly high nozzle. Don't use glue stick with PLA — it can grip so hard it chips the coating.
Smooth PEI: more grip and a glossy bottom finish, but far less tolerant of grease and z-offset error. With PETG it's the opposite problem: it bonds so well it can tear the sheet. Use a thin glue-stick layer as a release agent, not an adhesive.
Glass: flat and cheap, but needs help — glue stick or hairspray — and it must cool before the part releases. Trying to prise a part off warm glass is how sheets crack.
Old or worn sheets: PEI loses grip over hundreds of prints as the surface polishes. If soap-and-water no longer restores it, a light scuff with 2000-grit or a new sheet is the real fix — no temperature will bring it back.

Material by material

Bed temperature is only half the story; each material fails in its own way:

PLA: if it won't stick at 60 °C, the problem is almost never temperature — it's grease or z-offset. Going hotter makes elephant foot worse, not adhesion better.
PETG: sticks too well, not too little. Keep the bed at the low end of its range (70–80 °C) and use a release agent on smooth sheets. If it lifts anyway, it's usually running too cool at the nozzle.
ABS / ASA: the entire fight is thermal. Without an enclosure, large parts will warp no matter how clean the bed is. Bed at 100–110 °C, no drafts, and a brim on anything with square corners.
TPU: adheres easily but drags if the nozzle is low. Print the first layer slowly, and don't over-squish — the flexible part will fuse to the plate.

Summary: 30-second checklist

Clean bed? Wash with water and soap.
Leveled and fine z-offset?
Correct bed temperature for the material?
First layer at 50% speed?
Shrinking materials (ABS)? No drafts + enclosure + brim.

If your printer lacks auto bed leveling and you're just starting, filter for it in the catalog: it saves you 90% of these headaches.

FAQ

Why do the corners of my print lift?: It's warping: the plastic shrinks as it cools and pulls the corners up. It mostly happens with ABS, ASA and PETG. The fix is reducing the temperature difference between part and air: hot bed, no drafts and, for technical materials, an enclosure.
How often should I clean the print bed?: Whenever adhesion gets worse. The #1 cause of sudden failures is finger grease: just touching the surface leaves an invisible film that blocks adhesion. Wash it with hot water and soap (not just alcohol) every few prints.
Do I need hairspray, glue or tape?: On modern PEI beds, usually not: a clean, well-leveled bed is enough. Adhesives are a useful patch for difficult materials or old beds, not the root fix.
What does z-offset have to do with it?: A lot. If the nozzle sits too high on the first layer, the plastic isn't squished against the bed and won't grip; too low and it drags. The right z-offset leaves the first layer slightly squished and even.