To learn how to fix pillowing, look below the bumpy top skin. A thin roof printed over wide gaps in sparse infill can sag or rise unevenly. Add enough solid top thickness, shorten unsupported spans if needed, then check cooling and print temperature with a small test piece.
How to fix pillowing at the source
Pillowing looks like rounded bumps or an uneven, sometimes partly collapsed top surface. The first top layer must perform bridging between supports inside the part; if it droops, later layers inherit that uneven base.
Check slicer preview at the height just below the top. Look for long gaps between infill lines, thin ceilings or a roof above an internal cavity. A ceiling that spans a broad hollow area may need a design change or internal support, not just a new temperature.
In short: Treat the unsupported roof before smoothing its visible skin.
Should you add layers or infill?
Increase top layer thickness first if the roof is simply too thin. Check thickness in millimetres as well as the number of top solid layers, because layer height changes the physical roof produced by a given count.
If the first solid line spans too far, raise infill density modestly or change its pattern to offer closer support. You can use a local modifier on a large model if your slicer permits. Printing an entire lamp base solid just to improve a small top face can use unnecessary material.
| Roof condition | Sensible first test |
|---|---|
| Thin top above otherwise supported infill | Add top thickness |
| Wide openings directly below the top | Shorten the span with infill or local support |
| Closed roof is lumpy despite adequate support | Check cooling and temperature |
What do cooling and temperature change?
The cooling fan helps deposited material keep its shape while spanning a gap, though the right setting depends on filament. A nozzle temperature above the material's workable range can make bridging droop; too low a setting can harm flow and layer bonding. Use the filament maker's range and test one adjustment at a time.
Enclosed machines and temperature-sensitive materials may need different fan behaviour from PLA. Keep the manufacturer's material profile as your baseline.
In short: Cooling is a material-specific check after the roof has enough support.
Are open holes the same as pillowing?
Not exactly. Pillowing describes a raised or irregular closed surface finish; visible holes between top lines are gaps. Both can appear on one print and may share inadequate top support. If the individual lines are narrow throughout, investigate extrusion rather than adding only roof layers.
When is a design change more useful?
A large flat top over a hollow vase or planter insert asks the printer to span a wide area. A slightly domed internal ceiling, a rib or a removable insert may reduce that span. Keep water containment and drainage requirements separate from the cosmetic finish.
Frequently asked questions
What causes pillowing on a 3D print?
Common causes are a roof that is too thin, long spans over infill and unsuitable cooling or temperature.
Will more top layers fix pillowing?
Often they help, but extremely wide unsupported spans may still need support or redesign.
Can low infill cause pillowing?
Yes. It can leave long gaps for the first top layer to cross.
Is pillowing the same as top-layer gaps?
No. Pillowing is an uneven roof; gaps are visible openings between lines or over cavities.
Should I always lower temperature?
No. Stay within the filament's guidance and check support and cooling first.
Make the roof work before polishing it
The most reliable approach to how to fix pillowing is to give the top layers a printable span, then tune their finish. For related troubleshooting, see How to Fix Gaps in Top Layers of 3D Prints, How to Fix Over-Extrusion in 3D Prints, and How to Fix Under-Extrusion in 3D Prints. For a display base, planter insert or other custom part, discuss your model with CraftLayer India for custom 3D printing in India.