reprap cube - speed optimized, big built aerea, replicating

This in another reprap derivat printer. The main idea to built it was to get a printer which is fast and has lots of space to build things. The x and y axis work with an etch-a-sketch kind of mechanism with two belts. The z axis is driven by 3 thread rods. The main frame is a cube built of 20mm extruded aluminium profile. my frame is 400x400x400 but this can be scaled as you like.
The extruder i designed for the printer is that one: http://www.thingiverse.com/thing:14311 and the electronics i