Warping and curling — how to stop corners lifting
Warping is the corners of a print pulling upward off the build plate as the part cools. It's a physics problem — every plastic shrinks as it cools, and big flat bottoms create big shrinkage forces. The fix is to either keep the part warm uniformly (enclosure) or to anchor it down so hard the shrinkage can't lift it (brim, mouse ears).
For PLA/PETG: close the doors and windows (eliminate drafts) and add a 5 mm brim. For ABS/ASA/PC: enclose the printer (Bambu X-series, Prusa CORE One, or a DIY box), use a 95–110 °C bed, and add an 8–10 mm brim. If only the corners lift, add mouse-ear discs at each corner instead of a full brim.
Why warping happens
Every thermoplastic shrinks as it cools from melt to room temperature. The shrinkage rate varies wildly by material:
| Material | Approx. shrinkage | Warp tendency |
|---|---|---|
| PLA | ~0.3% | Low |
| PETG | ~0.4% | Low–medium |
| ASA | ~0.6% | High |
| ABS | ~0.8% | High |
| PC / PC-blends | ~0.6–0.8% | Very high |
| Nylon (PA6/PA12) | ~1.0–1.5% | Extreme |
| PA-CF (carbon-filled nylon) | ~0.3–0.5% | Medium (carbon resists) |
Shrinkage itself is uniform — the problem is differential cooling. The bottom of the part is held warm by the heated bed; the top is exposed to air. As the top cools faster, it shrinks first, and the resulting tension lifts the corners off the bed. Solve the temperature differential and you solve the warp.
Fix 1: Enclose the printer
The single most effective fix for ABS, ASA, PC, and nylon. An enclosure raises ambient temperature inside the print volume to 35–55 °C, dramatically reducing the temperature gradient.
- Commercial enclosed printers: Bambu X1C / P1S / H2D, Prusa CORE One, Qidi X-series.
- Aftermarket enclosures: Creality fabric tent, IKEA Lack hack, or a sealed plywood box.
- Vent properly: ABS and ASA off-gas styrene (unpleasant, possibly irritating). Vent enclosed printers to outdoors or run them in a garage.
- Don't enclose PLA prints — PLA actually prints worse hot. If your printer has a chamber heater, set it to off or low (25–28 °C) for PLA.
Fix 2: Bed temperature
The bed has to be hot enough to keep the first 1–2 mm of the print near the plastic's glass transition temperature (Tg). Below Tg the plastic stiffens and the shrinkage forces win.
| Material | Tg | Recommended bed |
|---|---|---|
| PLA | 60 °C | 55–65 °C |
| PETG | 80 °C | 70–80 °C |
| ASA | 105 °C | 100–110 °C |
| ABS | 105 °C | 95–110 °C |
| PC | 147 °C | 110–120 °C (bed limit) |
Fix 3: Brim or mouse-ears
More bed-contact area = more force needed to lift the part. A brim is a single-layer skirt attached to the print's perimeter.
- Default brim: 5 mm wide for PLA/PETG, 8–10 mm for ABS/ASA/PC.
- Mouse-ears: small 6 mm discs added only at the corners as a custom modifier. They give brim adhesion at the worst spots without adding a full brim everywhere.
- Brim separation gap of 0.1–0.15 mm lets the brim pop off cleanly after the print.
- Don't use a raft unless the bed is unrecoverable. Rafts waste filament, time, and finish.
Fix 4: Reorient the part
Long flat geometries warp more than tall narrow ones because there's more cooling differential across the width. Strategies:
- Stand long flat parts on edge if their function allows it.
- Round corners on the bottom (add 1 mm fillets) so there's nothing for shrinkage to lift — the corner pulls inward instead of upward.
- Split unavoidable big-flat designs into 2 pieces and bond them post-print.
Fix 5: Eliminate drafts
Even with no enclosure, drafts are the #1 PLA/PETG warping cause. Common offenders:
- Open windows or doors.
- HVAC vents blowing directly on the printer.
- Ceiling fans in the same room.
- The printer itself, when its part-cooling fan blasts at full speed (lower part-cooling to 30–50% for warpy materials).
If you can't enclose the printer, even a 3-sided cardboard wind-shield around it dramatically reduces warping on PLA and PETG.
Fix 6: Aggressive bed adhesion
For PC, nylon, and large ABS prints:
- Glue stick on a clean PEI sheet adds another 5–10 N of peel force.
- ABS slurry (acetone with dissolved ABS scraps) painted on glass works at Stratasys-level grip.
- Magigoo PC is the only adhesion aid that reliably holds polycarbonate.
- Garolite (G10) plates are the gold standard for nylon — nylon bonds to G10 chemically.
Fix 7: Reduce part cooling
Part-cooling fans speed up the top-of-part cooling that drives the temperature differential. For warpy materials, dial part cooling back:
- ABS / ASA: 0–25% part cooling (some enclosed printers run 0% on the first 10 layers and 25% after).
- PC: 0% for the first 20 layers, 15–25% after.
- PETG: 30–50%.
- PLA: 100% (PLA doesn't really warp at room temp, so cool it hard).
Related articles
Sources & further reading
- Prusa Knowledge Base — Warping
- Bambu Lab Wiki — 3D Prints Shrinkage: Causes and Solutions