Additive manufacturing build units with process gas inertization systems

A build unit for additively manufacturing three-dimensional objects, the build unit comprising:

• an energy beam system, the energy beam system comprising one or more irradiation devices respectively configured to direct one or more energy beams toward a build plane and onto a region of a powder bed;
• and
• an inertization system, the inertization system comprising an irradiation chamber defining an irradiation plenum and a return manifold configured to receive and/or evacuate a process gas from the irradiation plenum while irradiating the region of the powder bed with the build unit situated above the region of the powder bed, the process gas flowing through the irradiation plenum and into the return manifold while irradiating the region of the powder bed;
• wherein the return manifold comprises a plurality of return manifold bodies arranged along a width of the return manifold, each of the plurality of return manifold bodies defining a respective one of a plurality of return manifold outlets of the return manifold, the plurality of return manifold bodies respectively coupled to one another or defining a respective integrally formed portion of the return manifold, the return manifold comprising a return manifold inlet disposed at a bottom portion of the irradiation chamber and defined at least in part by each of the plurality of return manifold bodies, respective ones of the plurality of return manifold bodies comprising one or more return manifold pathways downstream of the return manifold inlet fluidly connecting the return manifold inlet to respective ones of the plurality of return manifold outlets and a process gas evacuation line, and the return manifold inlet fluidly communicating with the irradiation plenum defined by the irradiation chamber and the one or more return manifold pathways defined by the respective ones of the plurality of return manifold bodies;
• wherein the plurality of return manifold bodies comprises one or more recapture pathways disposed across at least a portion of the one or more return manifold pathways to recapture the process gas into the one or more return manifold pathways that escapes past and beneath the return manifold inlet.