Warping and thick sections in 3D printing
Warping is a part pulling away from its intended shape as it cools. The cause is the same in every technology, uneven heat and shrinkage, and the geometry that triggers it can be measured.
| Technology | What triggers warping | Limit used here (working assumptions) |
|---|---|---|
| FDM | a large first layer on the plate | largest first-layer size: PLA 250 mm, PETG 200 mm, ASA 140 mm, ABS 120 mm, PA6-CF 160 mm |
| SLS | thick sections and large flat faces | thickest section about 30 mm; a flat face over 40 cm² is flagged |
| Metal LPBF | sudden changes of cross-section between layers, and bulky thick-and-thin parts | a change of more than 3 times between layers is flagged; compactness below 0.7 is flagged |
Cross-section jumps
The cross-section of a layer is the area of material at that height. When it changes suddenly from one layer to the next, the heat flow changes too. In an SLS build of 200 parts, arranging them for an even cross-section cut the spread of sintered area over the height from 53 % to 25 %: see the study.
Compactness
Compactness is the part volume divided by the volume of its convex hull, the smallest convex shape around it. A value below 0.7 means a branched part that needs more support and more powder handling. It is informational, not a fault.
How to reduce warping
- Hollow or rib thick sections instead of leaving them solid.
- Break up a large flat face with ribs or a slight curve.
- Add fillets where thick and thin meet, so the change is gradual.
- Rotate the part so the largest area is not in one layer, see orientation.
- Split a part that is larger than the first-layer limit of its material.
Find the warping risks of your part
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