First layer won't stick to the bed
Lines drag around behind the nozzle, curl up or peel off instead of staying flat on the bed.
Also described as not sticking, won't stick, bed adhesion, first layer peeling, filament not sticking to bed, lines dragging, nothing sticks
Try these in order
Most likely and quickest to check first. Change one thing at a time so you know what fixed it.
Nozzle too far from the bed
The first layer should be pressed slightly into the bed. Round lines with gaps between them mean the nozzle is too high.
- Re-level the bed, or redo the auto bed levelling mesh.
- Lower the Z offset in steps of 0.02 to 0.05 mm until the lines are slightly flattened and touch each other.
Dirty bed
Fingerprints and oil are the most common reason a bed that used to work stops working.
- Wash a PEI sheet with warm water and washing-up liquid, then dry it with a clean towel.
- Wipe with isopropyl alcohol between prints and avoid touching the print area.
Bed or nozzle temperature too low
- Check the bed is at the right temperature for the material, and let it heat for a few minutes so the whole plate is warm.
- Raise the first layer nozzle temperature by 5 °C.
First layer too fast
- Slow the first layer to 15 to 25 mm/s.
- Turn the part cooling fan off for the first layer or two.
Wrong surface for the material
- Use glue stick on glass, or for nylon and polycarbonate.
- Check the material reference for which bed surface suits your filament.