Bambu Studio ironing settings for PLA: values and print time
The top of a 3D print is made of lines laid side by side, with grooves between them that catch the light. Ironing is one extra pass that exists only to erase those grooves.
What ironing does
After the last top layer is printed, the nozzle travels over the same surface again at the same height, extruding very little plastic. The hot nozzle softens the top and that small amount of material flows into the grooves, as described on Bambu Lab's ironing wiki page (checked November 2026).
Because the nozzle only works facing down, this applies to top surfaces that are flat and horizontal. Side walls don't change, and on a curved or sloped top the layer steps stay there: the time goes up and the result barely changes.
The settings and where to start
| Setting (Bambu Studio) | What it does | Bambu profile (PLA, 0.4 mm nozzle) | When to change it |
|---|---|---|---|
| Ironing Type | Which surfaces get ironed | No ironing (off) | Use Topmost surface; Top surfaces when there are flat faces at different heights |
| Ironing Pattern | Shape of the pass | Lines (Rectilinear) | Concentric on a round top |
| Ironing flow | Extra plastic, as % of normal flow | 10% | Raise it a little if lines remain; lower it if you see excess |
| Ironing line spacing | Distance between passes | 0.15 mm | 0.10 mm smooths more, and the ironing pass takes 50% longer |
| Ironing speed | Speed of the pass | 30 mm/s | Slower smooths better and takes longer |
| Ironing inset | Margin from the edge | 0.21 mm | Raise it if plastic builds up at the edge |
Other slicers start elsewhere: PrusaSlicer uses 15% flow, 0.1 mm spacing and 15 mm/s; Cura uses 10% and 0.1 mm. They all follow the same rule: spacing must be smaller than the nozzle diameter, so every spot gets smoothed more than once.
To tune it, print a 30 × 30 × 3 mm square and change one value at a time: flow first, then spacing, then speed. Bambu Studio also has an ironing direction; the wiki points to 45° relative to the top lines, and that field only shows up with Develop mode turned on in Preferences.
How much time it adds
The extra time comes from a simple calculation:
time ≈ top area ÷ line spacing ÷ speed
On a 100 × 60 mm plate: 6,000 mm² ÷ 0.15 mm = 40,000 mm of travel; ÷ 30 mm/s = 1,333 s, or about 22 minutes. The slicer agrees:
| Ironing settings | Total time | Extra time |
|---|---|---|
| No ironing | 19 min | — |
| 0.20 mm at 40 mm/s | 31 min | +12 min |
| 0.15 mm at 30 mm/s (Bambu profile) | 41 min | +22 min |
| 0.10 mm at 30 mm/s | 52 min | +33 min |
| 0.10 mm at 20 mm/s | 68 min | +49 min |
| All solid layer, 0.15 mm at 30 mm/s | 2 h 40 min | +2 h 21 min |
Illustrative example: a 100 × 60 × 4 mm plate, Topmost surface type (except the last row), estimated by OrcaSlicer 2.4.2 with the Bambu Lab X1 Carbon 0.20mm Standard profile and PLA Basic. A slicer prediction, not a measurement.
Plastic barely changes: +0.15 g on the plate. The cost is time. With the calculator's default values, an hour of machine wear and electricity comes to about $0.17, so the 22 minutes cost roughly $0.06 per plate. What matters is the queue: on a batch of 10 plates, that is 3 h 40 min more printer time. The hourly math is in the guide to cost per hour.
When it is worth it and when it isn't
It is worth it on signs, name plates, badges, logos, box lids, coasters and flat faces that will be glued together: the surface feels smoother and reflects light evenly.
It isn't worth it on figures, curved parts, sloped tops and functional parts where nobody looks at the top. It also won't fix a bad top: if there are holes or gaps in the last layer, you are short on top layers (the 0.20mm Standard profile uses 5, or 1 mm). Thinner layers also smooth curved tops, which is covered in the guide to layer height.
Where it is in the slicer
- Bambu Studio: process settings, Quality tab, Ironing group. You can turn it on for just one object on the plate through the per-object settings.
- OrcaSlicer: Quality tab, Ironing group; the speed is under Speed > Other layers speed > Ironing speed.
- PrusaSlicer: Print Settings > Infill > Ironing (Advanced or Expert mode); the speed is under Print Settings > Speed.
- Cura: Top/Bottom section, Enable Ironing; the equivalent of Topmost surface is Iron Only Highest Layer.
Common defects and what to change
- Lines still visible: flow too low or spacing too wide. Raise flow a little or go to 0.10 mm.
- Ridges, burrs or blotchy shine: flow too high. Lower it.
- Plastic piling up at the edge: increase Ironing inset.
- Part coming loose from the bed: the nozzle drags on the top and pushes the part. Clean the plate and improve adhesion.
- Nozzle clogging: with low flow and low speed, heat travels up the filament (heat creep), a risk Bambu Lab flags for PLA, PETG and TPU. On an enclosed printer, open the door or lid for PLA.
Frequently asked questions
Does ironing make the part stronger?
Not in any way that matters. It is a finish: the extra plastic stays on the top surface. For strength, walls, top layers and infill are what count.
Does it work with PETG and other filaments?
It works with PLA, PETG and ABS, but the best flow and speed change with the material and even the color. Print the test square with the spool you will use before a large part.
Raised lettering on top: Topmost or Top surfaces?
Topmost surface only smooths the highest face, which is the top of the letters. Top surfaces also smooths the background around them, at the cost of more time. Small letters gain little; the wide background is where the difference shows.
Why does All solid layer take so long?
It irons every solid layer, including the internal ones. In the example, it added 2 h 21 min. PrusaSlicer treats its equivalent option as experimental, meant for transparent prints at 100% infill.
Can I smooth the bottom face that sat on supports?
Not with ironing, which only works on the top. The supported face improves with the support's top Z distance and interface layers, covered in the guide to tree vs normal supports.