Bed adhesion: what actually works

A print that comes loose mid-job is the most common single failure in FDM printing, and the internet’s answer is usually to buy something. In most cases the actual cause is free to fix.

Start here: it is probably your first layer

Before buying adhesive of any kind, check that the nozzle is at the right height. The overwhelming majority of adhesion problems are a first layer printed slightly too high — the plastic is laid near the bed rather than pressed into it. A correct first layer looks like slightly squashed lines with no gaps between them, and it sticks without help.

The other free fix: clean the bed. Fingerprints are grease, and grease is the enemy. Warm water with a little washing-up liquid, then dry it. Isopropyl alcohol works on PEI but does not remove oils as well as detergent does.

Both of these are covered properly in first layer calibration. Do them before anything below.

Temperature, which is also free

A bed that is too cool will not hold PLA well; too hot and you get elephant’s foot. Rough starting points: PLA 55–60 °C, PETG 70–80 °C, ABS/ASA 90–110 °C with an enclosure. Raising the first-layer bed temperature by 5 °C fixes a surprising number of marginal cases.

Then: brims and rafts

A brim adds a skirt of material attached to the part’s first layer, vastly increasing contact area. It costs a little plastic and a trim afterwards, and it is the correct answer for tall thin objects and small footprints. Use it freely.

A raft prints the part on a disposable slab. It wastes more material and leaves a rougher bottom, and it is rarely needed on a modern machine with a decent surface. Reach for a brim first.

Only then: adhesives

• Glue stick (PVA). Cheap, works, and doubles as a release agent — on glass and on PEI printing PETG, a thin layer stops the part bonding too well and tearing the surface. Genuinely useful.
• Hairspray. Works on glass. Messy, and it coats everything nearby. Largely superseded.
• Purpose-made adhesives. Effective, and priced accordingly. Rarely necessary for PLA and PETG.
• Blue painter’s tape. The old standby for PLA on a cold bed. Still works; mostly obsolete now that heated beds and PEI are universal.

PETG needs the opposite advice

PETG sticks to smooth PEI too well and can pull chunks out of the sheet. Here a glue stick is a release layer, not an adhesive. Use one, or print PETG on a textured plate where the mechanical grip is easier to break.

When the surface really is the problem

Old PEI loses its grip and gouged plates never recover. If the bed is scarred, or a fresh sheet fixes it, that is the answer — see build surfaces compared. But replace the surface as a considered decision, not as the first thing you try.

Questions people ask

Why are my 3D prints not sticking to the bed?

Prints usually fail to stick because the first layer is printed slightly too high, so the plastic is laid near the bed instead of being pressed into it. The second most common cause is a greasy bed from fingerprints. Lower the nozzle slightly and wash the bed with warm water and washing-up liquid before buying any adhesive.

Should I use a glue stick on my print bed?

A glue stick is useful, but mainly as a release agent rather than an adhesive. When printing PETG on smooth PEI or glass, a thin layer stops the part bonding too strongly and tearing the surface. For PLA on a clean, correctly levelled PEI bed, glue is rarely needed.

What bed temperature should I use for PLA and PETG?

Use a bed temperature of 55 to 60 degrees Celsius for PLA and 70 to 80 degrees for PETG. ABS and ASA need 90 to 110 degrees with an enclosure. Raising the bed temperature for the first layer by 5 degrees fixes many marginal adhesion problems.

What is the difference between a brim and a raft?

A brim is a flat ring of extra material attached to the first layer of the part, which increases contact area and is trimmed off afterwards. A raft is a disposable slab printed underneath the whole part. A brim wastes less plastic and leaves a cleaner bottom, so try a brim first; rafts are rarely needed on modern printers.

How do I clean a PEI print bed?

Clean a PEI print bed with warm water and a little washing-up liquid, then dry it thoroughly. Detergent removes finger grease better than isopropyl alcohol does. Isopropyl alcohol is fine for a quick wipe between prints, but a proper wash is what restores grip.

Why does PETG stick too well to my bed?

PETG bonds very strongly to smooth PEI and can pull chunks out of the sheet when the part is removed. Apply a thin layer of glue stick as a release layer, or print PETG on a textured plate, where the grip is mechanical and the part releases easily as the plate cools.

Do I need hairspray or special bed adhesive?

Hairspray and purpose-made bed adhesives are rarely necessary for PLA and PETG on a modern heated PEI bed. Hairspray works on glass but is messy, and commercial adhesives work but are expensive. A correct first layer height, a clean bed and the right temperature solve most adhesion problems for free.