DXU - Dual Extrusion Upgrade for UM2+

## FEATURE
- This project upgrades Ultimaker 2+ to a reliable dual extrusion printer.
- The approach is based on the great effort everyone put into Mark2 for Ultimaker 2 and Ultimaker 3. 
- The print head holds two hot ends, which are originally to be installed on standard UM2 head for 1.75 filament. The right nozzle move up and down nozzle swapping. 
- This compact dual print head can achieve single extrusion print area of 220x223x205, and dual extrusion print area of 202x223x200.

## VID