Devices and methods for additive manufacturing using flexible filaments

1. A method of depositing flexible filament onto a substrate to form objects, the method comprising:

threading a flexible filament through a passageway in a heating element and through a passageway in a nozzle, wherein the flexible filament is unconstrained between a metering device and the heating element, the heating element being disposed between the nozzle and the metering device such that the flexible filament is threaded through the passageway in the heating element before being threaded through the passageway in the nozzle;

extending a first portion of the flexible filament from the nozzle through an opening in a compaction foot disposed between the nozzle and the substrate, wherein the compaction foot is configured to move vertically independent of the nozzle and the opening in the compaction foot is a conical hole having its larger diameter opening at a side of the compaction foot facing the nozzle and its smaller diameter opening at a side of the compaction foot facing the substrate;

with the heating element, heating the nozzle to a temperature that permits the flexible filament to be bonded to the substrate;

with one or more actuators, creating relative vertical motion between the nozzle and the compaction foot to bring the first portion of the flexible filament into contact with the substrate;

retaining the first portion of the flexible filament in contact with the substrate until the first portion of the flexible filament adheres to the substrate; and

moving the nozzle relative to the substrate with the flexible filament in tension.

2. The method of claim 1 , wherein:

the flexible filament is incapable of carrying an axial compressive load without buckling.

3. The method of claim 2 , wherein:

the flexible filament comprises a thermoplastic polymer material; and including:

partially or fully melting the thermoplastic polymer material to form a part having a shape; and;

cooling the thermoplastic polymer material such that the part maintains the shape.

4. The method of claim 2 , wherein:

the flexible filament initially comprises a partially cured thermoset polymer material; and including:

depositing the thermoset polymer material to form a part having a shape; and:

curing the thermoset polymer material to maintain the shape of the part.

5. The method of claim 1 , wherein:

the flexible filament comprises a continuous carbon nanotube yarn or fiber.

6. The method of claim 1 , wherein:

the flexible filament comprises a polymeric material, a continuous carbon nanotube yarn or fiber, and a doping material that modifies at least one of the thermal, electrical, and/or structural properties of the polymeric material.

7. The method of claim 6 , wherein:

the doping material is selected from the group consisting of chopped fibers, nanotubes, nanosheets and metal powders.

8. The method of claim 1 , wherein:

the flexible filament comprises continuous yarn or fiber infused with a thermoplastic polymer material or a partially cured thermoset polymer material.

9. The method of claim 1 , including:

utilizing the metering device to control tension in the flexible filament.

10. The method of claim 9 , including:

moving the compaction foot relative to the nozzle and the substrate to apply a compaction force on the flexible filament, wherein the conical hole is beveled at an edge at the side of the compaction foot facing the substrate.

11. The method of claim 1 , wherein:

tension in the flexible filament is greater than or equal to zero.

12. The method of claim 1 , wherein:

the flexible filament and substrate bond is enhanced in at least one selected area by adhering the flexible filament to the substrate at more closely-spaced locations in the at least one selected area than in an at least one other area that is outside the at least one selected area.

13. The method of claim 1 , wherein:

the flexible filament is heated to a higher temperature in at least a first selected area relative to a second area outside the first selected area to provide increased bond strength in the first selected area relative to the second area.

14. The method of claim 13 , including:

configuring a processor to execute an algorithm to determine areas where additional bond reinforcement is required utilizing data that is supplied by a user.

15. The method of claim 1 , wherein:

the bond between the flexible filament and substrate is enhanced over the entire printed length of the flexible filament by adhering the flexible filament to the substrate at closely-spaced locations over the entire length of the flexible filament.

16. The method of claim 1 , including:

utilizing the compaction foot to clamp the first portion of the flexible filament to the substrate,

wherein:

the compaction foot comprises a flat plate extending radially from the conical hole perpendicular to the substrate and farther than a diameter of the nozzle; and

the compaction foot is configured such that the flat plate allows for clamping compaction of the flexible filament regardless of a direction of movement of the nozzle.

17. The method of claim 1 , including:

determining locations on a part to be printed that require additional bond reinforcement prior to depositing the flexible filament on the substrate.

18. The method of claim 1 , including:

utilizing three dimensional computer aided design data concerning a part to produce a tool path comprising a plurality of anchor points at which the flexible filament is bonded to the substrate.

19. The method of claim 1 , including:

causing the nozzle to travel along a tool path that includes a plurality of segments in which the nozzle moves towards the substrate, and a plurality of segments in which the nozzle moves away from the substrate.