Ironing problems: ridges, rough patches, nozzle drag

This guide is for anyone who has turned ironing on and got a worse or patchy top: grooves that didn't smooth out, a raised ridge round the edge, a rough or over-extruded surface, or plastic collecting on the nozzle. It covers the ironing settings in Bambu Studio, PrusaSlicer, OrcaSlicer and UltiMaker Cura, with defaults tied to the version we checked, and the warnings the makers give. If you haven't turned ironing on and the top is scratched or has holes, see our top surface scarring or gaps in top layers guides instead.

What does ironing do?

Ironing is a second pass over a top surface at the same height, with very little flow. Bambu Lab says the nozzle's heat "will soften the top lines," and the small amount of extruded material "can easily fill and smooth the top layer." Prusa says the spacing between ironing passes "is usually a fraction of the nozzle diameter," so the nozzle goes over the same spot several times.

Prusa says to "experiment with the ironing flow, speed, and spacing to achieve the best results," so expect to tune all three.

Match the symptom to the setting

The settings in each slicer

Printer and filament profiles can set their own values, so check what yours uses before changing anything.

Step 1: Calibrate normal flow first

Prusa says ironing is "very sensitive to accurate extruder calibration," and that tuning it "is a matter of trial and error." OrcaSlicer describes ironing flow as "a percentage of the normal flow rate." Calibrate the filament's flow first. Our over-extrusion guide walks through flow calibration in each slicer.

Then print a small flat test part for each change. Polymaker suggests testing ironing "on flat benchmarks."

Step 2: Adjust ironing flow

Each maker describes both ends of the range:

• Prusa: "Too little and shiny groves will be visible at the top layer, which will not be ironed. Too much and the excess plastic will be dragged by the nozzle to the edges of the top surface."
• Bambu Lab: "Too high a value will result in over-extrusion on the surface. Too small a value can also cause the ironing surface to not be smooth enough."
• OrcaSlicer: "A lower value will result in a smoother finish but may not cover the surface completely. A higher value may cover the surface better but can lead to over extrusion or rougher finish."
• Cura: "Keeping the nozzle filled helps filling some of the crevices of the top surface, but too much results in overextrusion and blips on the side of the surface."

Flow is relative to your normal layer height in PrusaSlicer and Bambu Studio, according to their tooltips. OrcaSlicer adds that "a lower layer height may require higher flow due to less volumetric extrusion per distance." So if you change layer height, check ironing again.

Change flow in small steps, and change nothing else in the same test.

Step 3: Check line spacing

The makers recommend spacing at or below the nozzle diameter:

• Prusa: spacing "should be smaller than your nozzle diameter," so "the nozzle will pass over the same spot several times."
• Bambu Lab: spacing is "usually recommended to be smaller than the nozzle diameter so that the same area can be repeatedly ironed multiple times." Its wiki compares 0.15 mm and 0.5 mm spacing. In the v02.08.02.61 source, a spacing below 0.05 mm triggers a "Too small ironing spacing" warning and resets it to 0.1 mm.
• OrcaSlicer: "It's recommended to set this value to be equal to or less than the nozzle diameter for optimal coverage and surface finish."

PrusaSlicer, Bambu Studio and Cura all default to 0.1 mm. Prusa ties ironing's extra print time to the "very small spacing between ironing lines."

Step 4: Slow down if it isn't smoothing

The makers agree slower is better for ironing:

• Prusa: "Feel free to experiment with this value, but generally, slower speeds work the best." In PrusaSlicer, the speed isn't with the other ironing settings. It's under Print Settings, Speed, Ironing.
• Bambu Lab: "usually a slower speed can obtain a better ironing effect."
• OrcaSlicer: ironing speed is "typically slower than the top surface speed to ensure a smooth finish."
• Polymaker: for incomplete smoothing, its advice is "Increase ironing passes or slow movement speed." For over-melting, it suggests lowering the ironing temperature or reducing the flow rate.

Step 5: Use inset for edge build-up

If plastic piles up round the edge of the ironed area, keep the ironing away from the edge:

• Bambu Studio: Ironing inset was added in version 1.10. Bambu says "there may be material accumulation in the edge area," and inset sets "the distance between the ironing area and the edge." 0 disables it, which is the default in v02.08.02.61.
• OrcaSlicer: Inset "can help prevent over-extrusion at the edges of the surface being ironed." At 0, the ironing "will start directly at the perimeter edges."
• Cura: Ironing Inset keeps a distance from the edges, because "ironing all the way to the edge of the mesh may result in a jagged edge on your print."
• PrusaSlicer 2.9.6 has no inset setting. Prusa says the ironing toolpath is planned for a small extrusion, "but the nozzle is physically still the same size, so some plastic will bleed over the edge."

If the edge ridge doesn't go away with inset, lower ironing flow (Step 2).

Step 6: Try a different pattern or angle

• Bambu Studio: the v02.08.02.61 source offers Rectilinear (default) and Concentric. Bambu's wiki describes a third, Archimedean Chords, so your version may differ. Bambu says Concentric suits tops that are "circular, elliptical, polygonal, or have rounded corners." The ironing direction is the angle between the ironing lines and the top surface lines, and Bambu says "usually 45° Angle can obtain a better ironing effect." Changing it needs Develop mode in Preferences.
• PrusaSlicer: ironing "is angled at a fixed 45 degrees compared to the first phase of normal top infill," which Prusa says "produces better results."
• OrcaSlicer: offers Rectilinear and Concentric, and an Angle Offset relative to the top infill. It says "commonly used ironing angle offsets are 0°, 45°, and 90°." Its Fixed Angle option uses one absolute angle so the finish "does not have alternating line directions," which "may result in a more uniform surface finish and reduced tiger striping effect when reflecting light." With the default 45° solid infill direction, OrcaSlicer suggests fixed angles of 0° or 90°.
• Cura: Zig Zag or Concentric. Monotonic Ironing Order "takes slightly more time to print, but makes flat surfaces look more consistent." It's off by default in 5.13.0.

Step 7: Iron only where you need it

Ironing more surfaces than you need costs time and adds heat creep risk.

• Topmost only. Every slicer can iron only the highest surface: Topmost surface in Bambu Studio and OrcaSlicer, Topmost surface only in PrusaSlicer, Iron Only Highest Layer in Cura. Prusa explains that with embossed text, only the top of the letters gets ironed, "but not the space between the letters." Cura says the option "saves time if the lower layers don't need a smooth surface finish."
• Not all solid layers. Bambu says All Solid Layer "is rarely used because it may not produce good printing results and requires a significant amount of additional printing time." Prusa calls its All solid surfaces option "an experimental feature meant to be used with 100% infill to create clearer transparent objects."
• Part of a model. In PrusaSlicer's Expert mode, you can turn ironing on for one object, or use a height range modifier or modifier mesh to iron only part of a model. Prusa says that with several instances of an object, you need to "Set as a separate object" first, or every instance gets ironed.

Materials

Prusa says the ironing settings "don't differentiate between various materials," but results do:

• PLA "irons very nicely, however, it is most prone to heat creep."
• PETG "irons well, but there's an increased risk of extra filament sticking to the nozzle." Prusa says it can build up, darken and attach to the print.
• Flexible filament has the same problem, "but much more pronounced."
• ASA "irons incredibly well, producing super smooth top surfaces."
• Wood-filled filaments: Prusa says "we didn't achieve good results," though "your experience may vary."

Bambu Lab names PLA, PETG and TPU as materials "with low softening temperatures" at higher heat creep risk during ironing. For multi-material prints, OrcaSlicer suggests using Material Setting Overrides "to customize ironing settings for each material."

Warnings before you iron

Bambu Studio also has an Ironing fan speed setting in the filament's Cooling settings. Its v02.08.02.61 tooltip says a lower than regular fan speed while ironing "reduces possible nozzle clogging due to the low volumetric flow rate." It defaults to -1, which disables it.

The other warnings:

• Flat tops only. Bambu says ironing "is only effective when the top surface is flat," and on curved tops it may only "increase printing time." Prusa says it's "not useful for round objects, figures, and organic shapes," or for flat areas that aren't parallel to the bed.
• Time. Prusa calls increased print time "the main downside," and says the preview shows how much time goes to ironing. Bambu says a large top area "may add quite a bit of printing time."
• Bed adhesion. Bambu says the nozzle "will rub over the top layer," so the model takes "greater force from the nozzle compared to normal printing," and may come off the plate if it isn't firmly bonded.
• Consider printing upside down. Prusa says the bottom layer printed on the build plate "will typically be even smoother than an ironed top layer."

What won't ironing fix?

Ironing is a finishing pass. If you see holes, sagging lines or drag marks, fix those first, then add ironing:

• Gaps or see-through lines in the top: our gaps in top layers guide.
• Holes or bumps from the top sagging into the infill: our pillowing guide.
• Lines dragged across the top by travel moves: our top surface scarring guide.

A sensible order

1. Make sure the top is flat, closed and free of drag marks before ironing.
2. Reset to your maker's profile and calibrate normal flow for this filament.
3. Print a small flat test with ironing on the topmost surface only.
4. Adjust ironing flow in small steps until grooves fill without edge build-up.
5. Keep spacing below the nozzle diameter, and slow down if the surface still isn't smooth.
6. Add inset if plastic still builds up at the edges.
7. Try another pattern or angle if you see uneven reflections.
8. Watch for heat creep on long ironing passes, especially with PLA, PETG and TPU.

Checklist

• Top surface flat and parallel to the bed.
• Normal flow calibrated for this spool.
• Ironing limited to the surfaces you need.
• Ironing flow tuned in small steps.
• Line spacing smaller than the nozzle diameter.
• Ironing speed slow.
• Inset set if the edges build up.
• Pattern and angle tried if reflections look uneven.
• Part well stuck to the bed.
• Printer watched during long ironing passes.

How this guide was checked

This is a research-based guide. We haven't printed test models for it. Every setting name, default and quote comes from the Prusa Research, Bambu Lab, OrcaSlicer, UltiMaker Cura and Polymaker pages and source files listed above, retrieved on 2026-10-13. Defaults are from the Bambu Studio v02.08.02.61 and PrusaSlicer 2.9.6 source and the Cura 5.13.0 base definition. The OrcaSlicer wiki doesn't list defaults, so we haven't given any. Read more in our editorial standards.

Print problems: what to check before you buy ↗