US Patent 7896209 Filament drive mechanism for use in extrusion-based digital manufacturing systems

A filament drive mechanism comprising a rotatable component comprising a central hole defined at least in part by an internally-threaded surface, and is configured to receive a filament strand through the central hole to engage the internally-threaded surface with the filament strand. The filament drive mechanism further comprises at least one rotation mechanism configured to rotate the rotatable component, thereby allowing the engaged internally-threaded surface to drive the filament strand through the central hole of the rotatable component.