This is my version of the Iron Man II Arc Reactor.
4 printed pieces, (28) 5mm white LED's, (28) 0805ish 820 ohm resistors. Lots of soldering. Superglue. 12V power of some sort.
Print out all 4 Pieces. Low layer height is necessary on the coils and core to minimise the 'stairs' effect.
Also, the parts are designed for .4mm extrusion width. Anything other than that is untested.
Everything can be black/grey ABS except the diffuser, which should be made from transparent blue PLA at lowest infill.
4 LED's need to be cut/sanded down to fit in the center 4 holes.
The resistors are a bit awkward since I used 0805 surface mount versions. I did this all in 1 day with what I had on hand, so no apologies. Don't try this if you don't have good soldering skills. You have been warned.
I've uploaded some of my pictures of the wiring, but because there can be so many variations I will let you decide on your own details.
EDIT: July 13 2013 - Added Core and Coils with wider slits to aid in slicing with some software.