A three-dimensional print engine for fabricating a 3D article comprising: a plurality of walls laterally defining a build chamber; a build box including a build plate coupled to a vertical positioning apparatus, the build plate defining a lateral area; a powder dispenser (32, 34); a beam system configured to generate a plurality of energy beams that scan over a build plane within the lateral area of the build plate and that is generally at a fixed height for powder fusion; a peripheral plate disposed between the build plate and the plurality of walls, the peripheral plate having an upper surface; a gas inlet that ejects a gas flow stream at an inlet end of the build chamber and passes over the build plane and at least part of the upper surface of the peripheral plate; a gas outlet at an outlet end of the build chamber and receives the gas flow stream from the gas inlet; a plurality of projecting structures mounted to and extending above the upper surface of the peripheral plate, the plurality of projecting structures shape a flow field of the gas flow stream to provide a more uniform velocity of gas flow velocities above the build plane; a gas handling system coupled to the gas inlet and gas outlet; and a controller configured to: 1) operate the vertical positioning system to position the build plate for receiving a new layer of powder; 2) operate the powder dispenser (32, 34) to dispense the new layer of powder over the build plate or a previously dispensed layer of powder, the new layer of powder having an upper surface proximate to the build plane; 3) operate the gas handling system to provide the gas flow stream; 4) operate the beam system to selectively fuse the new layer of powder; and 5) repeat steps 1-4 to complete fabrication of the 3D article. a plurality of walls laterally defining a build chamber; a build box including a build plate coupled to a vertical positioning apparatus, the build plate defining a lateral area; a powder dispenser (32, 34); a beam system configured to generate a plurality of energy beams that scan over a build plane within the lateral area of the build plate and that is generally at a fixed height for powder fusion; a peripheral plate disposed between the build plate and the plurality of walls, the peripheral plate having an upper surface; a gas inlet that ejects a gas flow stream at an inlet end of the build chamber and passes over the build plane and at least part of the upper surface of the peripheral plate; a gas outlet at an outlet end of the build chamber and receives the gas flow stream from the gas inlet; a plurality of projecting structures mounted to and extending above the upper surface of the peripheral plate, the plurality of projecting structures shape a flow field of the gas flow stream to provide a more uniform velocity of gas flow velocities above the build plane; a gas handling system coupled to the gas inlet and gas outlet; and a controller configured to: 1) operate the vertical positioning system to position the build plate for receiving a new layer of powder; 2) operate the powder dispenser (32, 34) to dispense the new layer of powder over the build plate or a previously dispensed layer of powder, the new layer of powder having an upper surface proximate to the build plane; 3) operate the gas handling system to provide the gas flow stream; 4) operate the beam system to selectively fuse the new layer of powder; and 5) repeat steps 1-4 to complete fabrication of the 3D article. 1) operate the vertical positioning system to position the build plate for receiving a new layer of powder; 2) operate the powder dispenser (32, 34) to dispense the new layer of powder over the build plate or a previously dispensed layer of powder, the new layer of powder having an upper surface proximate to the build plane; 3) operate the gas handling system to provide the gas flow stream; 4) operate the beam system to selectively fuse the new layer of powder; and 5) repeat steps 1-4 to complete fabrication of the 3D article.