Arc CPU Case

Arc is a computer (CPU) case for SE Manufacturing, with a faceted, angular body, a honeycomb grille across the front and the ARC name raised from the surface. We printed the case parts for them in nylon powder, and sprayed them silver in house. The photo at the top shows the case as it came off the printer, before spraying; the parts on the racks below are the sprayed silver finish.

Why nylon powder suited it

The front of the case is the hard part. Its grille is a field of thin hexagonal cells, and the raised lettering sits above the surface on the same panel. In nylon powder printing the loose powder around each part holds it up while it prints, so the grille and the lettering came out in one piece with no supports to cut away afterwards.

The case is also made of several shaped parts: front panels, top caps and rear panels, each with its own openings and a recessed pad of small holes on the back. Printing them in nylon gave a tough, even-textured surface, the kind of part that handles like a finished product rather than a prototype.

Design tips from this part

• Size the grille bars to be seen. Nylon powder holds detail down to 0.5 mm, but 1.0 mm if it has to be read. The thin walls between the hexagonal cells are the part of the grille that has to survive cleaning, so we design them to at least 1.0 mm.
• Make raised lettering big enough to read. For text in nylon we use strokes of 1.0 mm, raised 0.5 mm, with letters at least 5 mm tall. The ARC name sits well above that.
• Keep walls at 1.0 mm, or 2.0 mm if the part is handled. A case that gets picked up, opened and fitted should use the thicker wall. Because powder needs no supports, the honeycomb prints in one piece, with nothing to cut out of the grille afterwards.

If you are designing something similar, our guide to nylon SLS and MJF problems you can fix in the model covers wall thickness, openings and the other rules that keep a grille like this printing cleanly.