Hatch reversal with keyhole transfer

A computer-based method of providing control data for an additive manufacturing apparatus for manufacturing a three-dimensional object from a metal-based building material, wherein the three-dimensional object is manufactured by the additive manufacturing apparatus by applying the metal-based building material layer upon layer and by sintering or melting the metal-based building material in a building plane by supplying radiation energy to positions in each layer assigned to a cross-section of the three-dimensional object in that the positions are scanned with at least one beam along a plurality of trajectories in accordance with a set of energy input parameter values, wherein the method of providing control data comprises:

• accessing computer-based model data of at least one portion of the three-dimensional object;
• generating at least one data model of a region of a layer of the metal-based building material to be selectively solidified, wherein the data model specifies a scanning of positions of the region to be selectively solidified by moving the at least one beam along a first trajectory and along a second trajectory substantially parallel to the first trajectory, wherein movement vectors of the at least one beam in the building plane have directional components opposed to each other during the scanning along the first trajectory and the second trajectory,
• wherein an initial point of the second trajectory has a distance from a terminal point of the first trajectory that is smaller than half of a beam width of the at least one beam at the terminal point of the first trajectory and
• wherein a radiant flux incident on the initial point and/or a radiant flux incident on the terminal point are set such that keyhole welding occurs when the radiation energy acts on the building material so that a recess is formed in the layer of the building material by the impingement of the at least one beam on the initial point or on the terminal point;
• and
• providing control data according to the at least one data model generated in the generating step for a generation of a control data set for the additive manufacturing apparatus.