US Patent 8185229 Apparatus and methods for handling materials in a 3-D printer

A method of controlling the flow of unbound powder in a build chamber. A build surface for receiving the powder is provided, with the build surface including a first plate defining holes 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 is disposed below and spaced from the first plate. A vacuum source is provided below the build surface.