A top-surface defect where gaps and bumps appear because too few solid layers fail to bridge across the infill below.
Pillowing occurs when the top solid layers must bridge across infill gaps that are too wide. The solid layers sag into the voids, creating bumpy, porous, or holey top surfaces. It is most severe at low infill densities (below 20%) with too few top layers (below 4). Gyroid and honeycomb infill patterns reduce pillowing compared to linear grids because their nodes provide more support points for the first top layer. Insufficient cooling of the top layer also contributes by keeping filament liquid and prone to sagging.
Add top layers (4 minimum, 6-8 for low-infill prints). Increase infill density to at least 20%. Switch to gyroid infill pattern for better top-layer support distribution. Increase cooling fan to 100% for top layers. Enable ironing to smooth over minor pillowing artefacts. Reduce top layer print speed to 25-30 mm/s to give each line time to solidify.
Adding more top layers without fixing low infill only partially addresses pillowing: infill must provide adequate support density. Ironing hides pillowing visually but does not restore structural integrity of the top skin. Printing top layers too hot (high temperature + low cooling) worsens pillowing even with sufficient layer count.
Related terms: Infill, Top and Bottom Layers, Part Cooling
| Field | 3D printing |
|---|---|
| Also called | top layer pillowing, swiss cheese top |
| Source | EDi Brain: tech/fdm |
Engineer, author of The Big Book of 3D Printing and additive manufacturing expert