Coloring filament for three-dimensionally printing colored objects

1. A filament for use with a printer head of a 3D printer, the filament comprising:

an exterior surface;

a cross-sectional profile defining a void having a pathway to the exterior surface; and

an interior surface having color selectively applied thereto through the pathway into the void, the color of the interior surface being visible through the exterior surface, wherein the color is applied only to the interior surface through the pathway into the void such that the color remains substantially isolated from components of the printer head when traveling therethrough.

2. The filament of claim 1 , further comprising a first filament portion coupled to a second filament portion, the first filament portion defining the interior surface and the second filament portion defining the exterior surface.

3. The filament of claim 1 , wherein the filament is split to expose the interior surface while having color selectively applied thereto.

4. The filament of claim 3 , further comprising a first filament portion defining the interior surface and a second filament portion defining the exterior surface, wherein the first filament portion and the second filament portion are connected when the filament is split.

5. The filament of claim 1 , wherein the filament includes only a single filament portion that comprises each of the exterior surface and the interior surface.

6. The filament of claim 1 , wherein the cross-sectional profile of the filament is substantially C-shaped.

7. An assembly that is configured to be coupled to and communicate with a 3D printer having a printer head, the assembly comprising:

a color-application unit configured to receive a filament and direct the filament to the printer head of the 3D printer, the filament including an exterior surface, an interior surface, and a cross-sectional profile defining a void having a pathway from the exterior surface to the interior surface; and

a color applicator coupled to the color-application unit, the color applicator operable to selectively apply color to the interior surface of the filament through the pathway into the void and not an exterior surface of the filament.

8. The assembly of claim 7 , wherein the filament includes a first filament portion and a second filament portion, the assembly further comprising a coupler positioned downstream of the color applicator configured to join the first filament portion to the second filament portion to form the filament directed to the printer head of the 3D printer.

9. The assembly of claim 8 , wherein the color-application unit and the coupler are integrated together as a single unit.

10. The assembly of claim 8 , wherein the coupler includes a body that has a first channel and a second channel, wherein the first channel receives the first filament portion and the second channel receives the second filament portion, and wherein the first channel and the second channel converge within the body to form a discharge channel that guides the filament through the body.

11. The assembly of claim 10 , wherein the body of the coupler includes a third channel that receives a third filament portion, wherein the third channel converges with the first channel and the second channel to form the discharge channel, and wherein the coupler joins the second and third filament portions to substantially enclose the first filament portion.

12. The assembly of claim 7 , further comprising a second color applicator coupled to the color-application unit, the second color applicator operable to selectively apply a different color to the interior surface of the filament.

13. The assembly of claim 7 , wherein the color-application unit includes a body, a conduit extending through the body, and a motor that engages the filament to move the filament through the conduit.

14. The assembly of claim 13 , wherein the color-application unit includes a through-hole that extends through the body and is communication with the conduit, and wherein the color applicator includes an elongate member containing the color and having a color applicator tip applies color to the filament through the through-hole, and wherein at least a portion of the elongate member is slidably received within the through-hole to selectively engage and apply color onto the filament.

15. The assembly of claim 7 , wherein the color applicator includes an inkjet cartridge.

16. A method for preparing a filament for use with a printer head of a 3D printer, the method comprising:

receiving the filament at a color-application unit, the filament including an exterior surface, an interior surface, and a cross-sectional profile defining a void having a pathway from the exterior surface to the interior surface;

applying color, by a color applicator coupled to the color-application unit, to the interior surface of the filament through the pathway into the void without applying color to an exterior surface of the filament; and

directing the filament from the color-application unit to the printer head of the 3D printer.

17. The method of claim 16 , wherein the filament includes a first filament portion and a second filament portion, and further comprising coupling the first filament portion to the second filament portion to form the filament that is directed to the printer head of the 3D printer.

18. The method of claim 17 , further comprising joining, by a coupler positioned downstream of the color applicator, the first filament portion and the second filament portion.

19. The method of claim 18 , further comprising:

receiving the first filament portion in a first channel of the coupler;

receiving the second filament portion in a second channel of the coupler; and

joining the first filament portion and the second filament portion together within a discharge channel of the coupler.