Sharp Gantry for Ultimaker 2 Aluminum Extrusion

This is an adjustment to the awesome Ultimaker 2 Aluminum Extrusion 3D printer by jasonatepaint.

These are the modifications I'm making:

1. Change all fillet edges to sharp edges, and add bracing to gantry. I'm not a big fan of fillet edge. There are too many round corners in the original built. The relative position of the rods are exactly the same as jasonatepaint's original design.
2. Change the bolts from M3 to M5, because I will replace some printed connectors for the frame with purchased metal connectors to make it more sturdy. The size of holes on metal parts is often M5/M6. So I changed all the holes of printed gantry to M5 as well.