Air knife assembly for additive manufacturing

Abstract

An additive manufacturing apparatus includes an environmentally sealed first chamber, a second chamber separated from the first chamber by a first valve, a platform positionable in the first chamber, a dispenser configured to deliver a plurality of successive layers of feed material onto the platform in the first chamber, at least one energy source to selectively fuse feed material in a layer on the platform in the first chamber, and an air knife assembly to direct a laminar flow of air across a layer of feed material on the platform in the first chamber. The air knife assembly includes an inlet module and an exhaust module that are movable through the first valve between the first chamber and the second chamber.

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;   an air knife unit comprising an inlet module and an exhaust module spaced apart from and facing the inlet module; and
 an air knife moving assembly rotatably coupled to the air knife unit to move the air knife unit along a surface of the platform, the air knife moving assembly including
 a retractable telescopic scissor assembly comprising a first pair of arms each having a first end rotatably coupled to a stationary portion of the additive manufacturing apparatus and a second pair of arms each having a second end rotatably coupled to the air knife unit, the retractable telescopic scissor assembly comprising a supply conduit that fluidically connects a gas inlet in the stationary portion to the inlet module and a return conduit that fluidically connects the exhaust module to a gas outlet in the stationary portion, each conduit extending continuously along arms of the retractable telescopic scissor assembly. 
 
   
     
     
         2 . The apparatus of  claim 1 , wherein the air knife moving assembly further includes a blower fluidically coupled to the supply conduit to supply gas to the supply conduit and fluidically coupled to the return conduit to receive gas from the return conduit. 
     
     
         3 . The apparatus of  claim 2 , wherein the blower is configured to flow gas along the supply conduit and the return conduit at substantially equal rates. 
     
     
         4 . The apparatus of  claim 1 , further comprising a guide rail configured to guide the air knife unit along the surface of the platform as the retractable telescopic scissor assembly retracts or extends to move the air knife unit. 
     
     
         5 . The apparatus of  claim 1 , wherein the retractable telescopic scissor assembly includes a first arm assembly and a second arm assembly, the first arm assembly comprising the supply conduit and return conduit, and the second arm assembly comprising a second supply conduit and a second return conduit, each of the second supply conduit and second return conduit similar to the supply conduit and return conduit of the first arm assembly. 
     
     
         6 . The apparatus of  claim 1 , wherein each arm of the first pair of arms is rotatably coupled to and movable by a respective actuator at the stationary portion, the pair of arms configured to rotate, upon being actuated by the respective actuator, inwardly or outwardly to extend or retract the retractable telescopic scissor assembly. 
     
     
         7 . The apparatus of  claim 1 , wherein the return conduit is a return chamber and the supply conduit is disposed inside the return chamber. 
     
     
         8 . The apparatus of  claim 1 , wherein the air knife unit further comprises a third supply conduit fluidically coupled to the supply conduit of the retractable telescopic scissor assembly to receive gas from the supply conduit, the third supply conduit fluidically coupled to the inlet module of the air knife unit to deliver gas to the inlet module. 
     
     
         9 . The apparatus of  claim 1 , wherein the telescopic scissor assembly is configured to move the air knife unit along a first axis between an extended position and a retracted position. 
     
     
         10 . The apparatus of  claim 9 , wherein the inlet module is configured to discharge the gas in a direction parallel to the first axis. 
     
     
         11 . The apparatus of  claim 9 , wherein the inlet module and outlet module are substantially rectangular and each have a longitudinal axis perpendicular to the first axis, and are wherein the inlet module and outlet module are spaced apart along the first axis. 
     
     
         12 . The apparatus of  claim 1 , comprising a pair of sidewalls connecting the inlet module to the exhaust module, wherein a cavity bounded by the inlet module, outlet module, and the pair of sidewalls has a bottom open to the feed material on the platform and a top open to receive a beam from the energy source. 
     
     
         13 . An additive manufacturing apparatus comprising:
 a platform;   a dispenser configured to deliver a plurality of successive layers of the feed material onto the platform;   an air knife unit comprising an inlet module and an exhaust module spaced apart from and facing the inlet module to form a gap therebetween that is open below to the feed material on the platform and open above, and wherein the inlet module and exhaust module are configured to flow a gas across a region of the feed material on the platform below the gap;   an actuator coupled to the air knife unit to move the air knife unit across the platform along a first axis, wherein a width of the region along the first axis is less than a width of the platform along the first axis;   a plurality of beam scanners, each beam scanner configured to generate a light beam that is scannable across a portion of the feed material on the build plate, wherein the plurality of beam scanners are laterally fixed relative to the platform and spaced apart along the first axis; and   a controller coupled to the actuator and configured to cause the actuator to move the air knife unit such that the gap covers a new region of the feed material on the platform, and wherein the controller is coupled plurality of beam scanners and configured to cause a respective beam scanner from the plurality of beam scanners to generate a beam that passes through the gap between the inlet module and the exhaust module when the air knife unit is below the respective beam scanner.   
     
     
         14 . The apparatus of  claim 13 , wherein actuator comprises a telescopic scissor assembly. 
     
     
         15 . The apparatus of  claim 13 , wherein the inlet module is configured to discharge the gas in a direction parallel to the first axis. 
     
     
         16 . The apparatus of  claim 15 , wherein the inlet module and outlet module are substantially rectangular and each have a longitudinal axis perpendicular to the first axis, and are wherein the inlet module and outlet module are spaced apart along the first axis. 
     
     
         17 . The apparatus of  claim 13 , comprising a pair of sidewalls connecting the inlet module to the exhaust module. 
     
     
         18 . The apparatus of  claim 13 , comprising a housing that forms a sealed vacuum chamber, wherein the platform is positioned within the chamber. 
     
     
         19 . The apparatus of  claim 18 , comprising a plurality of windows through a ceiling of the chamber, and wherein the plurality of beam scanners are positioned outside the chamber and each respective beam scanner is configured to direct a respective light beam through a respective window.