Prusa i3 Dual Direct Extruder E3D hotend

Dual direct extruder for Prusa i3 with E3D V5 hotend.

## Key features:
+ Bi-delta wing shaped X carriage structure resulted in a lightweight design with high X rigidity.
+ Symmetric design with minimum bending momentum load on X axis.shaft.
+ Relaxed YZ constrain to decouple X axis motion with YZ plane.
+ Robust cooling mount with E3D fan shroud and blower cooling nozzle.
+ locking lever on extruder arm for easy filament handling
+ easily accessible filament path
+ belt clamp w