Abstract: According to one example, there is provided apparatus for restraining objects during a powder and object separation process. The apparatus comprises a base plate comprising a set of spatially arranged apertures, a set of rods, each rod slidable within a corresponding aperture of the base plate. The base plate is to connect with a chamber to contain a volume of powder and objects to be separated and the apparatus is configured such that, when the apparatus is connected to a chamber containing a volume of powder and 3D objects the set of rods are positionable in, or are slideable into, a position extending vertically away from the chamber, and as powder is removed from under each rod, the rods are to slide through the apertures.

Abstract: A three-dimensional printer is described, wherein the three-dimensional printer comprises a build unit and a material removal unit. The build unit is configured to generate a three dimensional object. The material removal unit comprises a housing, a plurality of gas inlets and outlets, a plurality of valves and a control unit. The housing is sealed to the build unit and is configured to house a cake comprising the generated three dimensional object. The valves are configured to open and close the inlets and outlets, and the control unit is configured to control the valves, to allow gas to flow from different inlets to different outlets in different flow paths, in order remove powder from the object.