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.

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.