Another paste extruder

Remixed from https://www.thingiverse.com/thing:676336 designed by Oliver (which made a excellent job).

I've redesigned the following part to better fit my needs:

Main frame to allow the minimum gap needed for the big gear without extra play
Small gear with the hole to insert a nut
Big gear hole reworked to better fit the nut
A device to push the syringe piston but also allows the retract. 2 protrusion will prevent the rotation by resting on the main frame.

EDIT: For those who got pro