Various embodiments of the present invention relate to a method for welding a workpiece (660) comprising the steps of: making a first weld at a first position on said workpiece with a high energy beam (605), deflecting the high energy beam with at least one deflection lens (640) for making a second weld at a second position on said workpiece, focusing the high energy beam on said workpiece with at least one focusing lens (630), shaping the high energy beam on said workpiece with at least one astigmatism lens (620) so that the shape of the high energy beam on said workpiece is longer in a direction parallel to a deflection direction of said high energy beam than in a direction perpendicular to said deflection direction of said high energy beam. The invention is also related to the use of an astigmatism lens and to a method for forming a three dimensional article.