Post-processing FDM parts: from print to visible part
Sanding, priming, painting, inserts: which post-processing makes printed parts visually and functionally usable, and what it costs.
The layer structure is the signature of FDM. Inside a machine nobody minds it, on a trade fair stand or in the visible area of a product it matters. Post-processing bridges the gap, and it often decides whether a printed part is perceived as provisional or finished.
What works without extra effort
A cleanly printed part in a matte material already looks good for technical use. Matte materials and darker colors hide layers much better than glossy black. If you only want to soften the surface, choose an orientation that prints visible faces at fine layer heights.
Sanding and filling
The classic route for visible parts is wet sanding in rising grits, followed by filler primer. The primer closes the layer grooves, a second sanding levels the surface, and then the paint goes on. ABS additionally allows solvent vapor smoothing, which chemically seals the surface. It is fast, but it changes dimensions and is not suitable for mating faces.
- Wet sanding from 240 to 600 grit for paint-ready surfaces.
- Filler primer in two thin coats instead of one thick one.
- Mask mating faces and bores before sanding or ream them afterwards.
- For small series a sanding jig keeps all parts consistent.
Painting and coating
2K paints adhere well to prepared plastic surfaces and turn a printed part into a housing that is hard to tell from an injection molded one. For technical parts without visual demands, powder coating makes no sense, but a simple primer against UV and moisture does, for example for ABS outdoors.
Functional post-processing
Beyond appearance there is the work that makes a part functional in the first place: pressed threaded inserts for repeated assembly, reamed bores for shafts, glued-in magnets or fitted bearing bushings. This work is part of our quoting and should be planned into the design early, because it needs clearances and access.
Post-processing is manual work and is billed by effort. A sanded and painted visible part can cost twice the pure print price, but stays far below a painted prototype from the milling machine. Tell us in the quote which faces are visible, and we only put effort where it shows.