Explainer

What is Ironing in 3D Printing?

By Jeff Butts

Published April 9, 2024

If you want your 3D printing projects to look their best, consider turning on ironing. Let’s dive deep into what this feature is and when to use it.

One struggle with 3D printing is making your prints look as great as possible. When you’re using a filament deposition model (FDM) 3D printer, smooth surfaces are problematic. It’s only natural since your printer is melting the filament into place one layer at a time, you end up with a stair-step effect and other layer lines. To help reduce how much post-processing you have to do to smooth your build, 3D printing developers have developed an innovative feature called ironing. Let’s dive into what ironing is and how you can benefit from it with amazing-looking 3D prints.

Smoothing Your Top Surfaces for a More Beautiful Appearance

If you want your piece to be visually attractive, you likely don’t want to see jagged surfaces, distinct layer lines, or cross-hatched surfaces. Whether you’re printing signs with text, cosplay pieces, or your latest 3D art, you want surfaces as smooth as possible.

There are various methods to smooth your print during post-processing, but anything you can do to reduce how much work you need to put into sanding or nitpicking over fine details is a net win. Not only that, but taking measures to help your paint adhere to your 3D-printed surface is another boon.

The folks who develop the slicer software used to translate your 3D model into G-code instructions for your 3D printer are constantly coming up with ways to help with the aesthetics of your final product. One of those innovations takes a page from how we keep our clothes looking their best, wrinkle-free: ironing.

The Way Ironing Works in 3D Printing Is Ingenious

If your slicer supports ironing, it can be very helpful in giving you those super smooth top layers you’re looking for. It’s considered relatively new and experimental, but the feature first appeared in 2016. It’s been included in UtiliMaker’s Cura software since version 2.7 (we’re on version 5.6 at the time of this writing.)

Ironing first appeared in Simplify3D, though, under the name Neosanding. It’s a lot like ironing clothes, hence the newer name. It involves brushing the heated nozzle over the top layer to smooth out the top surfaces of your build, melting any material sticking up, and forcing it back into the top of the print.

In the process, ironing also extrudes a tiny amount of filament. This helps fill in gaps left behind during the printing process. Since over-extrusion would leave unsightly blobs and blemishes, ironing only uses a small fraction of the extrusion quantity the printer would otherwise lay down.

Is Ironing on a 3D Printer Worth It?

Ironing your 3D print build can help your printer give you the most beautiful output it can. It can also be a tremendous time-saver since it reduces how much sanding or other post-processing you have to do later. As noted earlier, ironing your 3D printing builds can also help the paint stick better to the surface.

When properly used, ironing helps to dramatically smooth the top surface of your build. In the examples above, you can see how much smoother the top surfaces of 3DBenchy are with ironing turned on. For your reference, both models were printed with a 0.12mm layer height; if you’re using such high-quality settings already and nothing precludes you from turning on ironing, you probably should use the feature.

When Is the Feature a Bad Idea?

That being said, ironing isn’t appropriate for every project. There are a few scenarios where the feature should be avoided.

• You haven’t calibrated your printer: Ironing a 3D printing job requires precision, or it’s just going to make a mess. You should first make sure you’ve properly calibrated your printer according to the manufacturer’s guidelines.
• You need the print to finish quickly: Since ironing requires the nozzle to make another pass or two over your printed surface, ironing will add to the amount of time it takes the build to complete.
• Your model has a curved top surface: Ironing only works on flat surfaces, so if the top of the model you’re printing is at all curved, ironing simply isn’t going to make it look any better.

You should also keep in mind what filament you’re using to print, as different materials respond differently to ironing. PLA, since it is susceptible to heat creep, can come out looking worse after ironing than before. That being said, if you have your temperature settings optimized for your PLA, you’ll see some benefits.

ABS and ASA work great with ironing since they are pretty resistant to heat creep. PETG filaments, on the other hand, won’t really work at all with the feature. Flexible or composite filaments, like TPU or PLA wood, are best used without ironing. These materials can end up clogging your nozzle if ironing is turned on.

How Do I Use Ironing in my 3D Printing?

Most modern slicer software supports ironing, but you’ll find it in different places. I’ve looked at several popular options to let you know where to look.

When you enable ironing, there will be a few new settings you can tweak. You can specify whether the 3D printer should iron all top surfaces or only the uppermost top layer. This would mean, for example, that the printer would only iron the surface of the top step in a set of stairs.

Most software also allows you to specify the ironing pattern to use, zig-zag or concentric. Additionally, you can set the ironing line spacing to control the distance between each nozzle pass.

Finally, ironing flow defines how much filament the printer uses when ironing. I typically leave this set to 10%, but your mileage may vary according to your specific climate conditions and the filament type used. Set this too high, and you’ll get blobs from over-extrusion or possibly scarring. If you set it too low, on the other hand, the process may not fill in gaps as fully as it could.

Making Your 3D Printing as Beautiful as Possible

Ironing is just one more tool in your toolbox to get the most out of your 3D printing experience. It may not leave you with a build that’s as smooth as butter, but it’ll get you one step closer to the results you want. At a minimum, ironing your 3D printing models can reduce the time you’d spend afterward on sanding or other smoothing methods.