Abstract: A low pull force system for feeding a filament along a feed path from a source to a liquefier in a 3D printer includes a low compressive force loading drive for advancing filament from the source, a feed drive for advancing filament into the liquefier, and an in-line accumulator comprising a telescoping joint positioned in the feed path between the loading drive and the feed drive. When the telescoping joint is in a contracted position, the loading drive activates to feed filament into the feed path at a rate faster than a rate at which the feed drive advances filament into the liquefier, causing the telescoping joint to expand and accrue a slack of filament in the feed path. When the telescoping joint reaches an extended position, the loading drive deactivates while the feed drive continues to advance filament into the liquefier, and the slack of filament is consumed.

Abstract: A filament drive mechanism for use with an additive manufacturing system includes at least first and second drives. Each drive includes a first rotatable shaft and a second rotatable shaft engaged with the first rotatable shaft in a counter rotational configuration. Each drive includes a pair of filament engagement elements, one on each rotatable shaft, and positioned on opposing sides of the filament path with a gap therebetween so as to engage a filament provided in the filament path.