Cleaning up FDM prints

Cleanup tools for PLA filament
One way in which FDM prints fall down compared with resin prints or traditionally moulded and cast models is in the visible layer lines that show up, even when running the printer right at the limits of its capabilities.

Printed at a layer height of 0.06mm
Most of the time, the layer lines aren't actually that much of a problem, especially for my purposes, which are primarily tabletop gaming. A decent paint job will disguise most of the problem, and during a game, the right silhouette is much more important than the miniscule details on a model.

However, from time to time, I do like to smooth out layer lines or other printing artifacts.

The fact is, there's no instant, automated way of doing that with PLA filament. ABS can be smoothed out (though with the loss of sharp detail) by melting the surface with an acetone fume bath, but that does absolutely nothing to PLA. To smooth out PLA, we have to resort to manual labour.

The tools I use are simple: a couple of fine needle files, and a couple of scrapers I made from stainless steel laboratory spatulas.

The process is also simple: I just file and scrape at the surfaces of the model until they're acceptably smooth enough to be painted. Quite often, that doesn't have to be completely smooth; just knocking off the corners of the layers of plastic is enough to give me a markedly better appearance once painted. It's a tedious process, but not difficult.

I use files in preference to grinding with sandpaper or diamond pads, because the teeth of files actually cuts away the surface of the plastic cleanly, whereas sandpaper, even in very fine grits, just abrades it roughly. You can get a very good surface with sandpaper, but you need to go down through a series of progressively finer and finer grits until the surface abrasion becomes effectively invisible. Files are a lot faster.

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