Abstract: A three-dimensional printer for the additive manufacturing of a part is provided. The printer includes a build platen, a pre-extrusion system, and a print head located downstream of the pre-extrusion system and configured to receive and deposit a filament. The print head includes a receiving section configured to receive the filament, an outlet through which the filament is deposited onto the build platen or a previously added layer of a part, a feeding mechanism constructed and arranged to feed the filament into the outlet, and a path length adjustment system positioned on the print head disposed between the pre-extrusion system and the feeding mechanism. The path length adjustment system constructed and arranged to create slack in the filament being delivered from the pre-extrusion system. Path length adjustment devices incorporating sliding components and flexure components are also disclosed.