A method for forming at least one three-dimensional article through successive fusion of parts of a powder bed, the method comprising the steps of: providing a model of the at least one three dimensional article; applying a first powder layer on at least one build platform; directing an electron beam from an inclined electron beam source over the at least one build platform where a central electron beam emanating from the source is building an angle α with respect to a normal to the build platform≠0°, the directing of the first energy beam causing the first powder layer to fuse in a first selected locations according to the model; rotating or tilting the electron beam source a predetermined angle, directing the electron beam from the tilted or rotated electron beam source causing a first powder layer to fuse in a second selected locations according to the model.