Warping: why a part lifts and curls during printing

Why plastic contracts

Hot plastic shrinks as it cools, which is ordinary thermal expansion. The bottom layers have already cooled, while the upper ones are still warm and pull them towards themselves. The stress is greatest in the corners, which is why they lift first.

The bigger the area, the bigger the force. An area of 200 × 200 mm is far more sensitive than a small holder. Sensitivity depends on the material as well: PLA shrinks little, PETG a bit more, and ABS or ASA a great deal, which is why they are printed in an enclosed chamber.

With PLA the shrinkage is small, so you do not need to worry about it on ordinary parts up to the size of a palm. With large flat boards, frames or long thin parts the risk is higher and worth tackling in the design.

What helps in the print

• A heated bed and good adhesion of the first layer, see adhesion.
• An enclosure, which prevents draughts and sudden cooling.
• A border around the part, a brim, which increases the contact area.
• Less fan on materials that tolerate it.

Our Elegoo Centauri Carbon 2 printers are enclosed, which greatly reduces this problem with PLA and PETG. It can never be ruled out completely, though.

What you can do in the model

• Round off sharp corners on large flat parts, as a fillet reduces concentrated stress.
• Split a large flat board into smaller pieces, see splitting a model.
• Avoid long thin walls without ribs.
• Let the part lie on its largest face, as model orientation decides a lot.

For your order

We prepare the model for printing on our server, and supports are automatically included in the price. We photograph the batch before dispatch. With a large thin board, where the risk is greatest, it is better to adjust the model before uploading it, or write to us about what the part needs.