Quick diagnosis
PETG sticks to a bed more aggressively than PLA and warps less readily than ABS, so when it does warp, it often looks different from the classic corner-peel: a part that seemed firmly bonded early on can still release a corner or lift late in a long print, and the strong bond can mask the problem until it suddenly lets go. For the shared fundamentals (first-layer contact, drafts, bed temperature testing, brim, orientation), start with the general warping checklist; this guide covers what is specific to PETG. If you’re chasing ABS-specific warping instead, see the ABS warping guide.
1. Confirm it is warping, not something that looks like it
Because PETG bonds so strongly, a plate that gets damaged or a base that is over-squished can produce symptoms that resemble warping without being caused by the same shrinkage. A torn PEI coating or a section of first layer squashed flat and wide (elephant’s foot) both call for a different fix than a warping guide. Check the underside of a failed print and the bed surface itself before assuming shrinkage is the cause.
2. Manage drafts rather than adding heat
PETG does not need the heated, sealed chamber that ABS benefits from, but it is still sensitive to an uneven temperature gradient between the top and bottom of a tall or wide part. A simple draft shield, an enclosure panel, or moving the printer away from a door, window or air-conditioning vent reduces that gradient without pushing chamber temperatures high enough to cause other problems. Treat “draft-free” as the goal for PETG rather than “heated,” since the two materials fail for different reasons.
3. Do not over-correct adhesion
Because PETG already grips well, adding a stronger adhesive, unnecessary glue, or unusually high bed temperature on top of a working PEI or glass surface is more likely to create a new problem than to fix a mild lift. Overly strong adhesion can pull up the bed’s coating when the part is removed, or the excess heat can soften the base enough to distort it in a different way. Test the plain, recommended bed temperature and surface first, and only add an adhesion aid if a clean surface at the right temperature genuinely is not holding.
4. Recalibrate first-layer squish
Too little squish leaves a weak initial bond that lets shrinkage win later in the print, especially at the corners of a large flat part. Too much squish spreads the first layer wider than the model calls for, which can look like a lifted edge when it is really excess material at the base. Recheck the Z-offset or first-layer height with a standard leveling or squish test and confirm the result is consistent across the full bed, not just the center.
5. Watch large, flat geometry specifically
PETG’s aggressive bond makes it a common choice for large flat parts, but those same parts build up the most shrinkage stress across their footprint as layers stack. Where possible, split very large flat prints or add designed adhesion tabs at the corners most likely to lift, rather than relying only on bed settings to counter the geometry. A brim helps here in the same way it does for other materials, but treat it as a last step after the plate, temperature and squish checks above.
PETG warping checklist
- Confirmed the issue is warping, not a torn plate coating or elephant’s foot.
- Drafts are managed with a shield or enclosure, without adding unneeded heat.
- Adhesion aids were not added before testing the plain bed at the recommended temperature.
- First-layer squish is recalibrated and consistent across the bed.
- Large flat parts have adhesion tabs or a brim if geometry demands it.