Viscosity pump for extrusion-based deposition systems

A pump system for extruding thermoplastic material supplied as a filament, the pump system comprising:

• a pair of drive rollers that are configured to feed successive portions of the filament;
• a housing that at least partially defines a barrel having a first end and a vent aperture;
• a liquefier housing secured to the housing and defining a liquefier cavity that extends circumferentially around the barrel at a location between the first end of the barrel and the vent aperture of the barrel, wherein the liquefier comprises a spiral baffle;
• a feed channel extending through the liquefier housing, and configured to direct the successive portions of the filament fed from the pair of drive rollers to the liquefier cavity;
• an extrusion tip secured to the housing at the first end of the barrel;
• and
• an impeller extending through the barrel and comprising a plurality of grooves that vary in depth along a longitudinal axis of the impeller at least between the liquefier cavity and the first end of the barrel.

An extrusion apparatus for building three-dimensional objects, the extrusion apparatus comprising:

• a pump system comprising:
• a first drive motor;
• a filament delivery assembly operably engaged with the first drive motor and configured to feed a filament of a thermoplastic material under operational power of the first drive motor;
• and
• a screw pump comprising:
• a housing that at least partially defines a barrel of the screw pump;
• an extrusion tip secured to the housing at a first end of the barrel;
• a liquefier secured to the housing and intersecting with the barrel, the liquefier comprising a feed channel configured to receive the filament fed from the filament delivery assembly;
• and
• an impeller extending at least partially through the barrel;
• a gantry assembly configured to move the pump system in at least one direction;
• a second drive motor disposed at a remote location from the pump system and the gantry assembly;
• and
• a belt pulley assembly configured to engage the second drive motor to the impeller of the pump system, thereby allowing the impeller to rotate under operational power of the second drive motor, wherein the belt pulley assembly comprises:
• a first pulley portion comprising:
• a first pulley;
• and
• a first drive belt engaged with the first pulley and the second drive motor, thereby allowing the first pulley to rotate under operational power of the second drive motor;
• a second pulley portion comprising:
• a second pulley axially connected to the first pulley, thereby allowing the rotation of the first pulley to rotate the second pulley;
• and
• a second drive belt engaged with second pulley and the impeller, thereby allowing the rotation of the second pulley to rotate the impeller.