An AM installation utilising SLM or SLS a chamber of a housing with a protective atmosphere, a support structure in the chamber defines an upper horizontal surface on which a laser source is operable for focusing onto predetermined regions of a build area of the plane of the horizontal surface. The laser beam source is operable so areas of each of successive layers of powder material are sintered or fully molten throughout its layer thickness. A dosing device raises successive quantities of powder to the level of the upper surface to enable a re-coater to form the layers. A separable build device unit defines build chamber opening at the upper surface, and includes a lift table and an electric drive by which the lift table is stepwise vertically adjustable so a progressively built component is lowerable into the build chamber.