A method for forming a three-dimensional article through successive fusion of parts of a powder bed, applying a first powder layer on a work table, directing a first energy beam from a first energy beam source over said work table causing said first powder layer to fuse in first selected locations according to a corresponding model to form a first cross section of said at least one three-dimensional article, where said first energy beam is fusing a first article with parallel scan lines in a first direction, fusing a second scan line in said first direction in said first layer in said first article within a predetermined time interval after fusing a first scan line in said first article, wherein at least one intermediate scan line is fused within said time interval at another predetermined position and where said first and second scan lines are adjacent to each other.