In this link:

[reprap.org]

I describe a project of a dual drive geared extruder. Is spite of using improper motors I got good results. Hope you enjoy.

To get a better grip, a simpler way is to have a bigger diam hobbgear with sharper teeth (hardened steel) and coupled with gear reduction (regular gear or worm). A smaller motor can even be used.
A light, compact extruder means also no Bowden and associated problems.

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"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)

Nice idea and thinking about how to speed up extrusion. I would be interested what the maximum mm³/s is with Volcano or even SuperVolcano.