Filament heaters configured to facilitate thermal treatment of filaments for extruder heads in three-dimensional object printers
An additive manufacturing system includes a heater for converting a filament of extrusion material into thermoplastic material. The heater has a channel configured to change the cross-sectional shape of the filament to a cross-sectional shape that has a greater surface area than the surface area of the filament before the heater receives the filament. The channel of the heater can also be configured to drive the center portion of the filament toward the heated walls of the channel and to mix thermoplastic material in the channel while exposing the center portion of the filament to the heated wall of the channel.
1. A heater for converting extrusion material to thermoplastic material comprising:
a body having an inlet that is fluidly connected to an outlet by a channel within the body, the channel being configured with a first cross-sectional shape at a first position between the inlet and the outlet and with a second cross-sectional shape at a second position between the first position and the outlet, the second cross-sectional shape being configured differently than the first cross-sectional shape to increase a surface area of extrusion material in the channel as the extrusion material passes through the channel from the first position to the second position, the second cross-sectional shape having a height between a first wall of the channel and a second wall of the channel that are located on opposite sides of a geometric center of the channel that is less than a height of the first cross-sectional shape between the first wall of the channel and the second wall of the channel that are located on opposite sides of the geometric center of the channel, and the second cross-sectional shape having a width that is greater than a width of the first cross-sectional shape; and
at least one heating element positioned in the body to generate heat in the channel and melt the extrusion material to form thermoplastic material before the extrusion material reaches the outlet.
2. The heater of claim 1 wherein the first cross-sectional shape of the channel at the first position is circular and the second cross-sectional shape of the channel at the second position is a polygonal cross-sectional shape.
3. The heater of claim 1 wherein the first cross-sectional shape of the channel at the first position is circular and the second cross-sectional shape of the channel at the second position is a non-circular curved cross-sectional shape.
4. The heater of claim 1 wherein the first cross-sectional shape of the channel at the first position is circular and the second cross-sectional shape of the channel at the second position is a pair of non-circular curved cross-sectional shapes.
5. The heater of claim 4 wherein the pair of non-circular curved cross-sectional shapes are joined together at an intersection to spread the extrusion material into each non-circular curved cross-sectional shaped channel.
6. The heater of claim 5 wherein the intersection between the pair of non-circular curved cross-sectional shapes occurs at a middle of each non-circular curved cross-sectional shape.
7. The heater of claim 1 wherein a wall of the channel at the first position is further configured to slope at a predetermined angle away from a surface of the extrusion material.
8. The heater of claim 1 wherein the heater is an integral unit and the channel within the heater varies in curvature along at least of portion of a length of the channel from the first position to the second position.
9. The heater of claim 1 , the body of the heater further comprising:
a first longitudinal portion and a second longitudinal portion, the first and the second longitudinal portions being configured to mate with one another to form the channel; and
at least one fastener configured to secure the first longitudinal portion and the second longitudinal portion together to form the channel.
10. The heater of claim 9 wherein the at least one heating element is embedded within one of the first longitudinal portion and the second longitudinal portion.
11. The heater of claim 10 wherein the at least one heating element is a pair of heating elements with a first heating element being embedded within the first longitudinal portion and a second heating element being embedded in the second longitudinal portion.
12. The heater of claim 10 wherein the at least one heating element is an electrically resistive heating element.
13. The heater of claim 12 wherein the body of the heater consists essentially of stainless steel.
14. The heater of claim 1 , the channel having three or more cross-sectional shapes between the inlet and the outlet, each of the cross-sectional shapes being different from one another.
15. The heater of claim 1 , the outlet of the channel being further configured to be compatible with a port on an extruder head to direct thermoplastic material directly from the outlet into the port without an intervening fitting.