Dual drive gear for improved grip, and prevent grinding filament. Frequent retraction is more reliable
Belt driven motion don't generate any noise itself during retraction. The only noise left from extruder would come from the stepper motor vibrating the frame of printer
3:1 gear ratio to increase torque
Very durable. No wear on belt and pulley over time comparing to printed gears
Adjustable compression of a strong spring
Modular parts for different combination of drive gear, filament and bowden tube
The bowden connector can slide for 3.5mm. Any diameter of drive gear between 7-12mm is applicable
Quick changeable drive gears. Can use large gear with slower motor speed for silent operation, and small gears with more torque for super fast extrusion rate.
Drive force test with E3D Hobb-Goblin gears, max of 9-10kg (max spring compression. NEMA17 48mm long with 0.55N.m torque, rated current of 1.5A running at 1.25A) at: https://www.youtube.com/watch?v=QorkxMkFOio
UPDATE:
26/05/2017 - v2 update. Slightly reduced tension of the belt. Raised the parts that could interfere with set crews which sticks out from the drive gear.
23/08/2017 - New stronger base plate.
20/09/2017 - Fixed the Bowden connector for 2.85 being too tight. Adjustable tension for the v3 base plates.