Air knife inlet and exhaust for additive manufacturing

Abstract

An additive manufacturing apparatus includes a platform, a dispenser configured to deliver a plurality of successive layers of feed material onto the platform, at least one energy source to selectively fuse feed material in a layer on the platform, and an air knife assembly.The air knife assembly includes an inlet unit to deliver gas over the platform and an exhaust unit to receive gas from over the platform. The exhaust unit includes a plenum having a port connected to a gas return conduit, and a gas collector that is open at a front end to receive gas from over the platform and has a concave plate at a back end of the gas collector. An aperture is formed at a back of the concave plate between the gas collector and the plenum to provide a constricted flow path for gas from the collector to the plenum.

What is claimed is:  
     
         1 . An additive manufacturing apparatus comprising:
 a platform;   a dispenser configured to deliver a plurality of successive layers of feed material onto the platform;   at least one energy source to selectively fuse feed material in a layer on the platform; and   an air knife assembly including
 an inlet unit to deliver gas over the platform, and 
 an exhaust unit including
 a plenum having a port connected to a gas return conduit, and 
 a gas collector that is open at a front end to receive gas from over the platform and has a concave plate at a back end of the gas collector, and wherein an aperture formed at a back of the concave plate between the gas collector and the plenum provides a constricted flow path for gas from the collector to the plenum. 
 
   
     
     
         2 . The apparatus of  claim 1 , wherein the aperture formed at the back of the concave plate comprises a longitudinally horizontal slot. 
     
     
         3 . The apparatus of  claim 2 , wherein the longitudinally horizontal slot comprises a height of between 9 millimeters and 11 millimeters. 
     
     
         4 . The apparatus of  claim 2 , wherein the longitudinally horizontal slot extends across a width of the gas collector. 
     
     
         5 . The apparatus of  claim 1 , wherein the concave plate is arranged to deflect the gas from over the platform toward the aperture. 
     
     
         6 . The apparatus of  claim 1 , wherein the gas collector comprises a ramp plate at a front end of the gas collector, the ramp plate comprising a low end adjacent a top surface of the platform such that the ramp plate deflects the gas from over the platform upwardly with respect to the platform, to form a residual collection pit at a base of the plenum. 
     
     
         7 . The apparatus of  claim 6 , wherein a height of the ramp plate is less than a height of the aperture. 
     
     
         8 . The apparatus of  claim 6 , wherein the base of the plenum comprises a planar floor. 
     
     
         9 . The apparatus of  claim 1 , wherein the port of the exhaust unit is disposed at a first lateral side of the plenum and a second port is disposed on a second lateral side of the plenum, opposite the first lateral side. 
     
     
         10 . The apparatus of  claim 9 , comprising return conduits extending vertically from the port and second port. 
     
     
         11 . The apparatus of  claim 1 , wherein the gas collector comprises a portion extending horizontally toward the inlet unit from an inner edge of the concave plate. 
     
     
         12 . The apparatus of  claim 1 , wherein the exhaust unit comprises a heat shield plate disposed underneath the gas collector and the plenum, the heat shield plate configured to shield the exhaust unit from heat generated at the platform. 
     
     
         13 . A method of removing burnt waste from a platform of an additive manufacturing apparatus, the additive manufacturing apparatus comprising a platform, a dispenser configured to deliver a plurality of successive layers of feed material onto the platform, at least one energy source to selectively fuse feed material in a layer on the platform, and an air knife assembly including an inlet unit to deliver gas over the platform and an exhaust unit to receive gas from over the platform, the inlet unit comprising a multi- chamber plenum, the multi-chamber plenum comprising a plurality of vertically stacked chambers fluidically connected with a first chamber of the plurality of vertically stacked chambers positioned at a higher elevation than a collection chamber of the plurality of vertically stacked chambers, and a gas distribution module fluidically coupled to the collection chamber, the method comprising:
 dispensing, by the dispenser, a layer of feed material over the platform;   fusing, by the energy source, the feed material, the fusing producing burnt waste over the platform;   receiving, by the inlet unit and from a gas supply conduit of the additive manufacturing apparatus, a gas;   flowing, by the inlet unit, the gas along the vertically stacked chambers from the first chamber to the collection chamber, and from the collection chamber to the gas distribution module;   flowing, by the inlet unit, a laminar flow of the gas parallel to a top surface of the platform to substantially remove the burnt waste from over the platform; and   receiving, by the exhaust unit, the laminar flow from over the platform.   
     
     
         14 . The method of  claim 13 , wherein the exhaust unit of the air knife assembly includes a plenum having a port connected to a gas return conduit, and a gas collector that is open at a front end to receive the gas from over the platform and has a concave plate at a back end of the gas collector, an aperture formed at a back of the concave plate between the gas collector and the plenum configured to provide a constricted flow path for gas from the collector to the plenum, and wherein receiving the laminar flow comprising deflecting, by the concave plate, the gas to the aperture to be received by the plenum.