You finish printing a flat lid, and the top still shows thin lines where the nozzle laid down plastic. The part works, but you want a more uniform finish. Your slicer offers a setting called ironing. Should you turn it on?
Ironing can improve suitable top surfaces, but it adds another operation to the print. Whether that extra time is worthwhile depends on the model, the material, and how visible the surface will be.
This guide compares ironing on vs off for filament 3D printing using slicer documentation. It explains the tradeoffs without claiming hands-on test results or a guaranteed finish.
Quick Answer
Try ironing when a visible, flat horizontal top surface deserves extra attention. Leave it off when the normal finish is acceptable, the important surfaces are curved or vertical, or speed matters more than that cosmetic improvement.
Start with a properly printed top layer. Ironing is a finishing step, not a reliable way to repair holes, weak top shells, or inconsistent extrusion.
Ironing On vs Off at a Glance
| Comparison | Ironing on | Ironing off |
|---|---|---|
| Printing process | Adds a low-flow finishing pass over selected surfaces | Finishes with the normal top-surface toolpaths |
| Main purpose | Make suitable flat tops look and feel more uniform | Keep the standard printed surface without an extra finishing operation |
| Time | Adds time depending on the area and settings | Avoids the additional ironing pass |
| Curves and sidewalls | Not a general smoothing method for those surfaces | Their normal layer texture remains |
| Tuning | May need adjustment of flow, speed, spacing, and surface selection | No ironing-specific tuning |
| Good comparison case | A visible flat lid, label, or display base | An early prototype or a part whose normal finish already works |
What Is Ironing in 3D Printing?
Ironing is a slicer-generated finishing operation. After printing an eligible top surface, the nozzle passes over it again using closely spaced paths and a small amount of extrusion.
The hot nozzle helps smooth small ridges, while the low material flow helps fill minor spaces between existing lines. It works on the printed plastic rather than adding a separate coating.
The extra paths are usually slow relative to normal printing. Their effect depends on how the material behaves and how the pass is configured.
What Changes When Ironing Is Off?
With ironing disabled, the top surface is completed by the normal top-layer paths. Fine lines may remain visible, but that does not mean the print is defective.
If a practical part already looks acceptable and functions correctly, the extra operation may add little value. For a fit-check prototype, confirming the shape and dimensions can be more useful than refining the top finish.
Keep that ordinary result as your baseline before testing an ironing profile.
Which Models Benefit Most?
Start with a part that has an exposed flat area parallel to the build plate. A box lid, a flat nameplate, or the top of a display base gives you a clear surface to evaluate.
A rounded figurine is a different case. Ironing does not remove the layer stepping across its curved body or polish its vertical sides.
For those surfaces, our 0.12mm vs 0.2mm layer height comparison explains a different way to approach vertical detail. The two features address different aspects of appearance.
If only one small face matters, check whether your slicer can restrict ironing to that object or surface category instead of applying it throughout the job.
How Much Extra Time Does Ironing Add?
There is no fixed percentage. The selected area, path spacing, movement speed, and number of surfaces all affect the additional work.
Compare the same model with ironing enabled and disabled. Keep the rest of the setup unchanged and record both estimates.
For illustration, if your slicer estimates 2 hours without ironing and 2 hours 18 minutes with it, the difference is 18 minutes, or 15%. Those are example numbers, not a prediction for your printer.
Ask whether the visible improvement is worth that specific delay. A finishing choice that makes sense for one display piece may be less attractive for a batch of hidden internal parts.
Settings That Deserve Attention
OrcaSlicer's documentation separates the type of surface being ironed from controls such as flow, spacing, speed, and inset. Exact names and available options vary between slicers.
- Surface selection: Check whether the option includes exposed tops at several heights or only the highest surface.
- Flow: Controls the small amount of plastic added during the finishing pass. It is not the same as changing the overall extrusion calibration.
- Speed: Changes how quickly the nozzle moves across the selected area.
- Spacing: Changes the distance between adjacent ironing paths and therefore their coverage.
- Inset: Where available, changes how far the finishing paths stay away from the surface boundary.
Use a supported starting profile and change one setting at a time. Avoid copying a complete recipe from an unrelated material and assuming it will produce the same surface.
Fix the Normal Top Surface First
If the top contains holes or sags into the interior, inspect the solid top thickness and the infill supporting it. Simplify3D's troubleshooting guide identifies insufficient solid layers, inadequate support from infill, and extrusion issues as possible causes of top-layer gaps.
Our infill vs wall count guide explains why the solid top shell and the interior structure should be considered separately.
Layer count also needs context. Five layers at 0.2 mm produce a nominal 1.0 mm top thickness; five at 0.12 mm produce 0.6 mm. Keeping the same count after changing layer height does not preserve the same thickness.
Get the ordinary top surface closed and consistent before judging what ironing can improve. A low-flow finishing pass is not a substitute for missing structural layers.
Does Ironing Replace Sanding?
Sometimes it may give you a finish you are happy to use directly. But it does not provide access to every face or guarantee the appearance needed for painting or a particular coating.
Decide what the finished object actually requires. A decorative label viewed from above may be ready after printing, while a painted prop may still need additional preparation.
Keep any post-processing appropriate to the material. Do not treat ironing as a promise that every later finishing step becomes unnecessary.
A Simple On-vs-Off Test
- Choose a representative sample. Include a flat top similar to the important face on the real model.
- Print the baseline. Use your working profile with ironing disabled.
- Enable ironing. Keep the printer, material, model, orientation, and other settings comparable.
- Check the preview. Confirm which surfaces receive the added paths and note the time difference.
- Compare after cooling. Use the same lighting and viewing angle to judge texture, edges, and consistency.
- Record a useful result. Save a separate profile for the tested setup rather than replacing every general-purpose profile.
If a result is patchy, retain the sample and note which setting you changed. A short record is more useful than repeatedly adjusting flow, speed, and spacing together without knowing which change helped.
Frequently Asked Questions
Will ironing remove sidewall layer lines?
No. This comparison concerns finishing eligible horizontal top surfaces. It does not turn the nozzle into a polishing tool for the whole model.
Does ironing guarantee a glossy finish?
No. Material formulation, color, and printing conditions affect appearance. Evaluate uniformity and the finish you actually want rather than assuming smoother must mean glossy.
Should I turn it on for every print?
No. Use it when a relevant surface benefits enough to justify the extra work. A model without a useful flat top may gain little.
Should I recalibrate the whole printer to fix one ironing result?
First confirm that normal extrusion and top layers print correctly. If they do, investigate the ironing-specific settings using a small test before making unrelated changes.
Final Verdict
Ironing is worth testing for visible flat top surfaces when a more uniform finish matters. Leaving it off is sensible when the normal result is acceptable or the important geometry does not benefit.
Build a sound top surface first, compare one finishing change at a time, and judge the result alongside the actual time added to your print.
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