Improve top layer quality: gaps, pillowing and rough skin
Build a supported, fully closed top surface before experimenting with ironing or cosmetic changes.
Inspect what is underneath
Pillowing and holes can start where the first solid layer bridges sparse infill. Preview those layers. A top skin needs enough thickness and support underneath; increasing the displayed layer count changes thickness differently at different layer heights.
Calibrate before adding material
Gaps between top lines can indicate under-extrusion; raised ridges can indicate excess flow. Compare a flow-calibration sample before changing top-surface flow alone. If the surface deteriorates only at speed, reduce its speed or the filament flow ceiling for a comparison.
Use ironing as a finishing pass
Ironing can improve flat upper faces once the underlying surface is already sound. It adds time and needs its own flow and spacing calibration. It cannot repair missing support beneath the top skin or make sloped faces flat.
Sources & further reading
This is our troubleshooting sequence, informed by the sources below. Community outcomes belong to their authors and have not been independently reproduced.