Testing Surface Quality with 3D Printing Ironing in FDM

We recently ran a small experiment to better understand how 3d printing ironing works in practice. This setting is available in most standard slicing software and is designed to improve the finish of flat top surfaces in FDM prints. But how effective is it, really?

Our goal was to see if ironing could help us achieve smoother, more uniform surface quality. While the feature is often mentioned in tutorials or used for text on top layers, we were more interested in real-world use — specifically, whether it could improve the look of flat housing parts or enclosures.

Upside Parts - 3D printing ironing - PLA Box

We selected a model with fairly simple geometry - a flat-bodied case with a protruding rectangular frame on top. It had the kind of flat surfaces where ironing should theoretically have the most noticeable effect. While we didn’t expect a mirror-like finish, we hoped for a smoother, more matte surface with fewer visible layers.

Testing 3D Printing Ironing on Different Materials

Before diving into print settings, it’s important to know that 3d printing ironing only affects the topmost horizontal layers. It won’t help with sloped surfaces or sidewalls. That makes it most relevant for parts with flat top geometry — something that's not especially common in many 3D printed models.

For this test, we used three common FDM materials: PLA, PETG, and ABS. Each of them reacts differently to heat, cooling, and extrusion flow, which made them ideal for evaluating this feature from multiple angles.

We started with matte PLA, which turned out to be the most visually successful result. Ironing created a smoother top surface, reduced visible layer lines slightly, and preserved the matte look of the material. That said, under close inspection, the surface still showed some roughness and fine grain. The improvement was there, but the change was modest.

ETG didn’t perform well in this test. The ironing pass left the top layers inconsistent, with visible lines still present and an awkward combination of gloss and matte that didn’t look clean. This is likely due to PETG’s naturally glossy finish clashing with the matte effect that ironing produces. The material also doesn’t cool as quickly as PLA, which may have contributed to the rougher surface.

ABS had the most trouble. The print began as expected, but after the printer completed the first ironed layer, extrusion issues began to appear. As the next top layer was being ironed, ABS's sensitivity to temperature and airflow caused a failure in extrusion. The print ultimately stopped partway through, making it unusable.

Our Considerations on Ironing vs Post-Processing

In our case, ironing increased print time without delivering a significant benefit in surface quality — especially on PETG and ABS. PLA showed some improvement, but even then, the result didn’t match what could be done with light post-processing.

Some makers suggest that ironing performance can improve by carefully tuning flow rates, speed, and temperature. While that’s likely true, we found that time spent adjusting those parameters might be better used on post-processing methods that give more consistent and predictable results.

If you're working with materials like PLA and want to learn more about how it behaves in different printing scenarios, take a look at our earlier post on high speed PLA plastic for more insights.

When Does It Make Sense to Use Ironing?

Based on our experiment, ironing is most useful if your model has large flat top surfaces and you're printing with a filament like matte PLA. It won’t replace sanding or surface finishing, but it can help reduce the visibility of layer lines in a limited way.

For more general help with slicing settings or material selection, our 3d printing in Boston MA services offer expert support tailored to your specific project. Whether it’s prototypes, end-use parts, or material experimentation, we’re here to help you get the best results.