Apparatus for the deposition of successive layers of a powder material onto a print bed to enable the production of components by additive manufacturing, such as laser-based additive manufacturing from CAD files, in which each layer is subjected in turn to selective heating, such as to above the melting temperature for the metal powder material, by focussed electromagnetic radiation providing selective melting, includes a housing defining a processing chamber in which a non-reactive or inert atmosphere is able to be maintained and, within the chamber, a system for the deposition of successive layers of powder material onto a print bed of the apparatus. The system has an elongate, powder material spreader member disposed in a first direction over and close to the print bed; a mounting member by which the spreader member is supported at an end for reversible lateral movement normal to the first direction between opposite sides of the print bed; and a powder material supply device above one side of the print bed and operable to discharge successive charges of the powder material and to spread a charge of the powder material over the upper surface in being moved from one to the other of the opposite sides.