Apparatus and methods for handling materials in a 3-D printer

1. A build chamber for use in a three-dimensional printer and adapted for receiving powder for producing three-dimensional objects, the chamber comprising:

a build surface for receiving the powder, the build surface comprising:

a first plate defining a plurality of spaced apart holes having a pitch; and

a second plate defining a plurality of openings spaced apart and offset from the plurality of holes in the first plate, the second plate disposed below and spaced from the first plate,

wherein the pitch corresponds to the space between proximate edges of adjacent holes.

2. The build chamber of claim 1 further comprising:

at least one wall at least partially circumscribing the build surface and at least partially defining the chamber;

a piston disposed below the build surface and adapted to the build chamber to move the build surface vertically relative to the at least one wall; and

an outlet coupled to the build chamber and disposed below the build chamber for removing unbound powder from the build chamber when a vacuum is applied.

3. The build chamber of claim 2 , wherein the outlet is located in a plenum disposed below the build surface and is adapted to be coupled to a vacuum source to draw unbound powder out of the build chamber through the build surface.

4. The build chamber of claim 2 further comprising a cover disposable above the at least one wall to at least partially isolate the chamber from its environment.

5. The build chamber of claim 1 , wherein the first plate and the second plate of the build surface are interchangeable with plates adapted for differing angles of repose.

6. The build chamber of claim 1 , wherein the build surface further comprises at least one spacer disposed between the first plate and the second plate to maintain a fixed spacing between the plates.

7. The build chamber of claim 1 further comprising a vacuum source coupled to the outlet for fluidizing the powder.

8. The build chamber of claim 1 , wherein the first plate and the second plate of the build surface are movable relative to one another.

9. The build chamber of claim 1 further comprising a mechanism for vibrating at least a portion of the build chamber.

10. The build chamber of claim 1 , wherein the plurality of openings of the second plate are offset from the plurality of holes in the first plate by approximately 50% of the pitch.

11. The build chamber of claim 1 , wherein the pitch is at least equal to 2(space between the plates)(cotangent of an angle of repose of the powder)+(diameter of holes).

12. The build chamber of claim 1 , wherein the pitch is approximately equal to 2(space between the plates)(cotangent of an angle of repose of the powder)+(diameter of holes).