Apparatus for fusing of multiple layers in additive manufacturing

An additive manufacturing apparatus for forming an object, comprising:

• a support;
• a dispenser to deliver feed material on the support or an underlying layer;
• an energy source to fuse the feed material, the energy source comprising a single laser;
• a controller coupled to the dispenser and the energy source and configured to cause the apparatus to successively form a plurality of layers on a support, wherein the plurality of layers includes multiple groups of layers, and wherein the controller is configured to form a group of layers from the multiple groups by causing the apparatus to
• for each layer in the group of layers, dispense a feed material on a support or an underlying layer to provide the layer;
• for each layer in the group of layers, after dispensing the feed material to provide the layer and before dispensing a subsequent layer, fuse a selected portion of the layer corresponding to the object by applying a first laser beam from the single laser to the selected portion of the layer;
• and
• after all layers in the group of layers are dispensed, fuse a volume of the group of layers that extends through all the layers in the group of layers by applying a second laser beam from the single laser to the volume of the group of layer at greater power than the first laser beam.