If you want to smooth out the top surface of your FDM 3D prints, you can try ironing. Many slicers allow you to set this option, which drags the hot printhead through the top surface with a tiny bit of plastic to smooth out the extrusion lines. However, a recent paper explains how non-planar ironing can provide a better result.

Usually, non-planar printing requires rotating the print bed in addition to the normal linear motion. However, you can also manipulate the layer height in real time to create bulges in the 3D print. This is the approach taken by Curvislicer, which shares authors with this paper. Another approach is to build a part conventionally but add non-planar printing to the last few layers.

The non-planar ironing is a variation of the latter technique. After slicing, the top layer of g-code passes through a Python script. The results on a test object look very impressive. We’d be interested to see how some more complex shapes look, though.

Of course, it looks like all you need is an ordinary printer, a modified copy of Slic3r, and the script, so if you try it yourself, let us know what you think. It would be great to smooth prints without extra chemicals and post-processing. While you can get good results, it is a lot of work.