My most involved design to date, a steampunk-ish arm piece. I've included all the separate files, as well as the files with the greebles already attached. I printed them separately so that I could do them in gold filament and not have to paint them. This also gives you the freedom to greeble it up to your heart's content! The rack and pinion gear box uses ball joints to attach to the arm pieces, to allow for free movement. I used some velcro straps to attach them to my arm.
This was inspired by Thomas Willeford's mechanical arm, which he wore on Steampunk'd. His has a cool piston connecting the upper and lower arm, but I didn't think that FDM was a good way to make a smoothly functioning piston, so I figured out a way to do it with a rack and pinion setup. Most (but not all) of the greebles here are borrowed from other designers here on Thingiverse... sablebadger's Imperial Greeblie, bbprops' Fallout 4 Suit Back, Mysterion's Y-wing helmet greeblie, bh1138's Han Solo Suede Jacket Badge, Jadis' Star Wars First Order Greeblie, Lukeluca's C-3PO Antenna, AeroDyz's Inner and Outer Forearm Greeeblies, and Heydnkm's C-3PO Greeblies. Whew! Thanks to all the awesome designers for making their stuff available!