Pillowing
Bumpy, uneven top surface — small dimples or bumps where the top shell bridges over infill gaps below.
Low severity
Surface
What It Is
Bumpy, uneven top surface — small dimples or bumps where the top shell bridges over infill gaps below.
How It Forms
The top layers of a print bridge over the infill pattern. Where infill supports the top shell, the surface is flat. Where there’s a gap between infill lines, the top shell sags slightly before solidifying.
With too few top layers, the bridging never fully flattens — each layer sags into the same spots. With insufficient cooling, the bridging material stays soft and droops further.
The bumps follow the infill pattern exactly — they’re a direct imprint of the structure below.
Visual Signature
- Regular bumpy pattern on top surfaces matching infill below
- Dimples or raised spots in a grid/triangle/gyroid pattern
- Rough to the touch compared to side walls
- More visible with lower infill percentages
Root Causes
| Cause | Calibration Variable | Direction |
|---|---|---|
| Too few top layers | — (slicer) | — |
| Infill percentage too low | — (slicer) | — |
| Cooling too low | Cooling / Fan Speed | ↓ |
| Temperature too hot | Extrusion Temp | ↑ |
How the Auto-Tuner Detects It
- Camera: Top surface roughness analysis on test print
How the Auto-Tuner Fixes It
- Calibration: Optimize cooling for top layers. Primarily a slicer settings issue (more top layers, higher infill).