Wanhao i3 Cube Frame

This is a front cube frame for the Wanhao Duplicator i3. I uses square cross section aluminium profiles.

It includes ideas from the otherwise excellent Z-Braces mod (http://www.thingiverse.com/thing:921948).

BOM:
- 8mm threaded rod
- 4 8mm nuts
- 20mm x 20mm Aluminium extrusion profile cut in (+- 1mm):
- 4 x 154mm bars (horizontal/bottom)
- 2 x 331mm bars (vertical)
- 1 x 365mm bar (horizontal/top)
- 22 M3 nuts (length > 10mm). The original ones are too short (length = 6mm or 8mm).

UPDATE 1: modified top_left and top_right plates, to allow more room for the 8mm nut. Added length of bars in summary.