Direct drive extruder for 1.75 or 3 mm filament

hi,
I'm sorry but my English is not riche.

I was inspired by : http://www.thingiverse.com/thing:275593

For the knob use the gcode and not stl file. When your reprap make a pause insert the 5 mm nut and press of the display's knob. for more informations look this : http://solidutopia.com/fr/fabrication-additive-avec-des-pieces-captives/