Abstract: The invention relates to a liquefier assembly (1) for an additive manufacturing system. The assembly (1) includes a heat sink (2), a nozzle (3) releasably connected to the heat sink (2) and a heater (4) connected to the heat sink (2) by a coil spring (5). The nozzle (3) has a 5 nozzle tip (31) at one end and the heater (3) is between the nozzle tip (31) and the heat sink (2) when the nozzle (3) is connected to the heat sink (2) and is biased away from the heat sink (2), toward the nozzle tip (31) and into thermal contact with a surface of the nozzle (3).

Abstract: A liquefier tube (5) of an extrusion head (4) for use in an extrusion-based additive manufacturing system (1). The liquefier tube (5) describes a passageway (P) having an inlet portion (57) and an outlet (55) downstream of the inlet portion (57). The inlet portion (57) has a substantially circular cross-section for receipt of a filament of material. The passageway (P) transitions from the inlet portion (57) to a non-circular portion (53) downstream of the inlet portion (57) and having a non-circular cross-section.