Abstract: The invention relates to an FFF printing system (100), the FFF printing system comprising a print head (105), a feeder (91;126) arranged to feed a filament (4) into the print head (105), and a container (801) for storing the filament on one or more filament spools (88). The system also comprises a prefeeder (81) arranged to feed the filament from the spools to the feeder (91;126), and a first flexible tube (D01;102;121) for guiding the filament (4). A filament path length measuring device (1) is arranged to detect a misalignment between the feeder and the prefeeder. Measurement signals are sent to a processing system to correct any misalignment.

Abstract: A bidirectional magnetic clutch for an additive manufacturing system, comprising a concentric arrangement of an inner drive member (2) and an outer drive member (3) enclosing the inner drive member (2), the inner and outer drive members (2,3) being rotatable relative to each other. The inner drive member (2) comprises at least two outward facing recesses (5, 6) and the outer drive member (3) comprises at least two inward facing recesses (8,9). Each outward facing recess (5,6) comprises a radially moveable roller member (10,11) of ferromagnetic material. The inner drive member (2) further comprises a magnetic biasing system (12) configured to magnetically bias the roller members (10,11) into the outward facing recesses (5,6). The bidirectional magnetic clutch further comprises a magnet actuator (13) at least partially circumferentially arranged around the outer drive member (3) and configured to maintain an engaged state or disengaged state of the bidirectional magnetic clutch.

Abstract: A bidirectional magnetic clutch for an additive manufacturing system, comprising a concentric arrangement of an inner drive member (2) and an outer drive member (3) enclosing the inner drive member (2), the inner and outer drive members (2,3) being rotatable relative to each other. The inner drive member (2) comprises at least two outward facing recesses (5, 6) and the outer drive member (3) comprises at least two inward facing recesses (8,9). Each outward facing recess (5,6) comprises a radially moveable roller member (10,11) of ferromagnetic material. The inner drive member (2) further comprises a magnetic biasing system (12) configured to magnetically bias the roller members (10,11) into the outward facing recesses (5,6). The bidirectional magnetic clutch further comprises a magnet actuator (13) at least partially circumferentially arranged around the outer drive member (3) and configured to maintain an engaged state or disengaged state of the bidirectional magnetic clutch.