The print is finished and perfect and it is not coming off. Levering at it flexes the whole plate; when it finally releases, a disc of the build surface comes with it.
This is the one fault on this site where the wrong technique costs more than the failure did, because the part is already made — what is at risk now is the sheet under it, and occasionally your hand.
Why this material sticks to this plate
For most filaments a first layer holds mechanically: plastic pressed into microscopic texture, released when the plate contracts on cooling. Copolyesters behave differently on smooth polyetherimide. PETG and PCTG grip the surface hard enough that removal can tear the coating off its substrate, and the bond persists after cooling instead of releasing.
Whether that is genuine chemical bonding between two polymers or an unusually intimate mechanical key is argued about and not settled — the two are hard to tell apart at the scale it happens on. What is not in dispute is the practical consequence: on smooth PEI, PETG needs a deliberate release layer, and a textured plate is the easier answer.
Nylon does something related on some surfaces, and TPU is its own problem — a flexible part cannot be levered at all, because it stretches instead of transmitting force to the bond.
The safe removal sequence
- Wait until the plate is completely cold. Not warm, cold. Most of the release happens through differential contraction between plastic and plate, and it needs the full temperature swing. This alone frees a large share of stuck parts.
- Flex the sheet if it is a spring steel plate. Bend it in both directions, working from a corner. Do not fold it double: repeatedly overflexing a PEI sheet crazes the coating.
- Try dental floss or a length of fishing line worked under one edge for parts with a large flat base. It slides along the bond line without a blade.
- Only then use a scraper, held at a shallow angle, pushing away from your hand. A sharp scraper on a fixed plate is one of the more common ways to get injured at a printer.
If a part is truly welded, putting the whole plate in a freezer for twenty minutes exaggerates the contraction difference and usually ends it.
Glass plates deserve a specific warning
On a bare glass bed, a strongly bonded PETG part can remove a lens-shaped chip of glass rather than release. That failure is sudden, and it produces sharp fragments.
If you print copolyesters on glass, use a release layer every time, without exceptions, and never attempt removal while the glass is hot — thermal shock and a stuck part together are how plates crack.
Glue stick is a release agent here, not an adhesive
This inverts the usual advice and is the fix most people have not heard.
A thin film of PVA glue stick between PETG and smooth PEI is there to keep the two apart. The part bonds to the glue, and the glue is water-soluble, so the plate washes clean and the coating survives. Hairspray works the same way. Applying it feels wrong when the problem is too much adhesion, which is exactly why it is worth stating plainly.
Stopping it in the first place
- Use a textured plate for PETG. The reduced contact area is enough on its own, and it is the reason so many machines ship with one.
- Raise the Z offset slightly for this material. A first layer squashed hard into smooth PEI is what creates the extreme bond; a marginally lighter first layer still adheres perfectly well and releases.
- Drop the bed temperature toward the bottom of the material's range. For PETG that means nearer 70 °C than 85 °C.
- Chamfer or radius large flat bases so there is somewhere to start a release rather than a continuous sealed perimeter.
Things that damage the plate rather than free the part
Do not attack the plate with acetone or a blade to remove residue. Do not heat the bed to loosen a part that has already cooled — reheating expands the plate under a rigid part and can lift the coating with it. And do not treat a plate that has lost patches of PEI as still usable for anything precise: those craters print as raised marks on every subsequent first layer, and a scarred sheet is the cheapest thing in this whole failure to replace.