Systems for Printing Three-Dimensional Objects

1 . A sacrificial raft structure, comprising a pattern selected from the group consisting of: a series of strips and a grid; wherein the sacrificial raft comprises at least one metallic material; wherein at least a portion of a 3D object is configured to form on a first side of the sacrificial raft structure and a support is on a second side of the sacrificial raft structure.

2 . A method for controlling a porosity of a structure, comprising:

printing the structure by directing a feedstock in contact with a support; using a power supply to flow electrical current through the feedstock and the support while the feedstock is in contact with the support; subjecting the feedstock to Joule heating upon flow of electrical current through the feedstock and the support, wherein Joule heating is sufficient to melt at least a portion of the feedstock; and depositing the at least the portion of the feedstock adjacent to the support to form the structure;

controlling the porosity of the structure via at least one of: altering a spacing between at least two adjoining contact points between the feedstock and the support, and altering a magnitude of the electrical current between the feedstock and the support.

3 . A method for printing at least a portion of a three-dimensional (3D) object adjacent to a support, comprising:

forming a sacrificial raft structure on the support;

receiving in computer memory a computational representation of the 3D object;

directing at least one feedstock through a feeder and in contact with at least one of: the sacrificial raft structure and the support; and

depositing at least a portion of the at least one feedstock adjacent to at least one of: the sacrificial structure and the support, wherein a size of the at least the portion of the at least one feedstock is controllable relative to the feedstock during deposition, thereby printing the at least the portion of the 3D object in accordance with the computational representation of the 3D object; and

wherein the sacrificial raft structure is configured to anchor the at least the portion of the 3D object to the support and permit removal of the at least the portion of said 3D object from the support; and

wherein a thickness of at least one layer of the sacrificial raft structure is greater than a thickness of at least one layer of the 3D object.

4 . The method of claim 3 , further comprising, removing the sacrificial raft structure from the support, and separating the sacrificial raft structure from the at least the portion of the 3D object.

5 . The method of claim 3 , further comprising repeating the depositing step to print the 3D object.

6 . The method of claim 3 , further comprising directing an additional feedstock through the feeder and depositing at least a portion of the additional feedstock adjacent to the least one of: the sacrificial raft structure, the support, and the at least the portion of the 3D object.

7 . The method of claim 3 , wherein the depositing step takes place in a presence of a gas that is configured to at least one of: reduce or substantially prevent oxidation of the at least the portion of the at least one feedstock, and increase a cooling rate of the at least the portion of the at least one feedstock.

8 . The method of claim 3 , further comprising controlling a porosity of the at least the portion of the 3D object by at least one of: altering a spacing between adjoining contact points between the at least one feedstock and the support or the at least the portion of the 3D object, altering an amount of the at least one feedstock that is directed towards the sacrificial raft structure, and altering an amount of the at least one feedstock that is directed towards the support.

9 . The method of claim 3 , further comprising storing a computational representation of the 3D object, extracting sets of data corresponding to successive voxels or layers from the computational representation, and performing the directing and depositing steps in accordance with the data.

10 . The method of claim 3 , further comprising selecting a size of the at least the portion of the 3D object by controlling a speed of retraction of the at least one feedstock.

11 . A method for printing an article upon a sacrificial raft, the method comprising:

printing a first layer of a plurality of stripes of the sacrificial raft upon a base, wherein one of the plurality of stripes has a first width across the first layer, and wherein an adjacent pair of the plurality of stripes are separated by a gap having a second width across the first layer;

printing a second layer of the plurality of stripes of the sacrificial raft above the first layer of the plurality of stripes of the sacrificial raft; and

printing a first layer of the article above the second layer of the plurality of stripes of the sacrificial raft.

12 . The method of claim 11 , further comprising: separating the sacrificial raft from the base; and

separating the article from the sacrificial raft.

13 . The method of claim 12 , wherein the separating the sacrificial raft from the base is performed before the separating the article from the sacrificial raft.

14 . The method of claim 11 , wherein a height of the first layer of the plurality of stripes is different than a height of the second layer of the plurality of stripes.

15 . The method of claim 11 , wherein a porosity of the first layer of the plurality of stripes is different than a porosity of the second layer of the plurality of stripes.

16 . The method of claim 11 , wherein a height of the first layer of the plurality of stripes is different than a height of the first layer of the article.

17 . The method of claim 11 , wherein a porosity of the second layer of the plurality of stripes is different than a porosity of the first layer of the article.

18 . The method of claim 11 , wherein the first width is different than the second width.

19 . The method of claim 11 , wherein the adjacent pair of the plurality of stripes are separated by a gap having a third width across the second layer of the plurality of stripes different than the second width across the first layer of the plurality of stripes.

20 . The method of claim 11 , wherein all of the plurality of stripes have the same first width across the first layer of the plurality of stripes.