(Robo3D) E3D hotend direct drive (geared/non geared) extruder

Direct drive upgrade for the Robo3D or any printer, using a E3D hotend and a MK8 drivegear using a Nema17 stepper motor with or without planetary gearbox. The extruder could be mounted on the standard Robo3D X-carriage, this was the main reason why I created another direct drive extruder. A change in the firmware is required to adapt the new steps per mm value.

Two variants are possible, usage of the standard Nema17 motor or a geared Nema17 with gear ratio ~ 5:1 (http://www.omc-stepperon