When to use this guide
Use this page when the symptoms below match what you see on the printer. Work through the checks in order and avoid changing several variables at once.
- Top surface has holes or gaps
- Infill pattern shows through the top
- Top layer looks pillowed or bubbled
- Flat surfaces are rough or uneven
- Increasing flow helps but causes blobs elsewhere
Most likely causes
These are the most common root causes. The correct fix depends on when the failure happens, which material is loaded, and whether the profile used to work before.
- Too few top layers for the layer height and infill density
- Infill is too sparse to support the top skin
- Cooling is inadequate for bridging over infill gaps
- Flow or extrusion consistency is low
- Temperature is too high and top skin sags
Safe fix order
This order is designed to prevent random tuning. Start with physical checks and material condition, then move into slicer changes.
- Increase top layer count before overcorrecting flow.
- Raise infill density if the top skin spans large gaps.
- Use a pattern that supports top surfaces more evenly.
- Improve part cooling for PLA top surfaces.
- Check for under-extrusion or partial clogs if gaps appear everywhere.
- Confirm layer height and top thickness are reasonable for the nozzle size.
Settings and decision notes
Top layersUse enough top thickness, not just a single cosmetic layer.
Infill densityVery low infill can cause top skin to bridge too far.
CoolingPLA usually needs good cooling for clean top surfaces.
FlowTune after confirming top layer count and infill support.
Bench checklist
Use this short checklist beside the printer before reprinting the full model.
- Check top layer count.
- Check infill density.
- Inspect extrusion consistency.
- Improve cooling where appropriate.
- Run a small flat test.
- Confirm with real model.
What to do after it works
Print a small confirmation part before returning to a long print. Save the working material, temperature, cooling, speed, and support notes in Profile Vault so the same problem does not become a repeat mystery.