Multi-screw extruder for large format 3D printers
A multi-screw extruder includes a drive mechanism operable to output a torque through a drive shaft, a plurality of extruder screws each operably coupled to the drive shaft to rotate in response to the torque, each of the extruder screws and including a shaft and a thread, an elongated barrel body defining a plurality of isolated screw compartments extending therethrough and each receiving one of the plurality of extruder screws therein, each screw compartment isolated from each of the other screw compartments along a length of the barrel body, a heater substantially circumscribing each of the screw compartments and operable to provide a heat flux into each of the screw compartments, a common collection chamber in fluid communication with each screw compartment, and a nozzle in fluid communication with the common collection chamber including a material outlet through which a molten printing material may be discharged from the extruder.
1 . A multi-screw extruder comprising:
a drive mechanism operable to output torque through a drive shaft;
a plurality of extruder screws each operably coupled to the drive shaft to rotate in response to the torque, each of the extruder screws including a shaft and a thread extending about the shaft;
an elongated barrel body defining a plurality of isolated screw compartments extending therethrough and each isolated screw compartment receiving a corresponding one of the plurality of extruder screws, each isolated screw compartment being an independent elongate cavity defined through a length of the barrel body;
at least one heater substantially circumscribing each isolated screw compartment and operable to provide a heat flux into each isolated screw compartment;
a common collection chamber in fluid communication with each isolated screw compartment; and
a nozzle in fluid communication with the common collection chamber and defining a material outlet through which a molten printing material may be discharged from the extruder.
2 . The multi-screw extruder of claim 1 , further comprising a thermistor coupled to each heater and operable to sense at least one of a temperature, a heat flux, or a combination thereof of the at least one heater.
3 . The multi-screw extruder of claim 1 , further comprising a material hub arranged at an upper end of the barrel body and including one or more material feeders providing flowpaths for the printing material to enter the material hub.
4 . The multi-screw extruder of claim 3 , further comprising a material sensor operable to detect a level of printing material present within the material hub.
5 . The multi-screw extruder of claim 3 , further comprising a gearbox and a bearing housing, wherein the bearing housing interposes the gearbox and the material hub and includes a plurality of bearings engageable with the extruder screws.
6 . The multi-screw extruder of claim 5 , wherein the plurality of bearings includes radial bearings and thrust bearings.
7 . The multi-screw extruder of claim 1 , further comprising a gearbox including a drive gear engageable with a screw gear forming part of each extruder screw.
8 . The multi-screw extruder of claim 7 , wherein the gearbox is a central-drive gearbox and the drive gear is centrally located and interposes the screw gears of each extruder gear.
9 . The multi-screw extruder of claim 7 , wherein the gearbox is a planetary gearbox including a planetary gear surrounding the screw gears and engageable with the drive gear on an outer surface of the planetary gear.
10 . A method of extruding molten printing material,
the method comprising:
introducing a solid printing material to a plurality of isolated screw compartments within a multi-screw extruder;
driving a gearbox of the multi-screw extruder and thereby rotating a plurality of extruder screws, wherein a corresponding one of the plurality of extruder screws is located in each isolated screw compartment, each isolated screw compartment being an independently-defined elongate cavity;
activating a plurality of heaters substantially circumscribing each isolated screw compartment and thereby providing a heat flux into each isolated screw compartment;
melting the solid printing material into the molten printing material within the plurality of isolated screw compartments;
collecting the molten printing material in a common collection chamber from each isolated screw compartment; and
extruding the molten printing material from a nozzle in fluid communication with the common collection chamber.
11 . The method of claim 10 , further comprising increasing a pressure within the common collection chamber to drive the extruding of the molten printing material from the nozzle.
12 . The method of claim 10 , further comprising sensing at least one of a temperature, a heat flux, and a combination thereof from the plurality of heaters via a plurality of thermistors.
13 . The method of claim 10 , further comprising:
introducing the solid printing material into one or more material feeders; and
flowing the solid printing material from the material feeders into a material hub arranged above each isolated screw compartment.
14 . The method of claim 13 , further comprising sensing, via a material sensor within the material hub, a quantity of solid printing material introduced by the material feeders.
15 . The method of claim 14 , further comprising controlling an amount of solid printing material introduced via the material feeders based on a quantity of solid printing material sensed via the material sensor.
16 . The method of claim 10 , further comprising stabilizing the plurality of extruder screws within the extruder via a plurality of thrust and radial bearings housed within a bearing housing.
17 . An extruder barrel assembly comprising:
an elongate barrel body;
a plurality of isolated screw compartments distributed throughout an interior of the body, each isolated screw compartment being an independent elongate cavity defined through a length of the elongate barrel body;
one or more of heaters substantially circumscribing each screw compartment and operable to provide a heat flux into each isolated screw compartment;
a common collection chamber provided at a bottom end of the elongate barrel body and in fluid communication with each isolated screw compartment; and
a nozzle in fluid communication with the common collection chamber and providing a material outlet in fluid communication with a working area.
18 . The extruder barrel assembly of claim 17 , wherein the elongate barrel body is in the shape of a rounded rectangle and the plurality of isolated screw compartments comprise two isolated screw compartments equally spaced within the body.
19 . The extruder barrel assembly of claim 17 , wherein the elongate barrel body is in the shape of a rounded triangle and the plurality of isolated screw compartments comprise three isolated screw compartments equally spaced radially about a central axis of the body.
20 . The extruder barrel assembly of claim 17 , further comprising a thermistor coupled to each heater and operable to sense at least one of a temperature, a heat flux, and a combination thereof of each heater.