1 5 A D V A N C E D M A T E R I A L S & P R O C E S S E S | J U L Y / A U G U S T 2 0 2 2 as titanium. Electron beam (EBW-DED) requires the part to be deposited within a vacuum chamber and is also used for reactive alloys. Regardless of the enclosed or open-air environment, an integral inert purge is typical through the center of the LP-DED nozzle or AW-DED and LW-DED deposition heads. The various DED processes allow additional degrees of freedom (5+) during deposition as compared to L-PBF, which is a 2+1 axis system. The deposition head can typically move in three axes with some systems allowing for tilt and rotate. Use of a kinematic robotic arm further increases the number Fig. 3 — Nozzle extensions fabricated using MAM DED illustrate the large-scale format: (a) LP-DED of NASA HR-1, 1.83 m tall x 1.5 mOD with 1 mm wall thickness and internal integral channels; and (b) AW-DED of aluminum tank for a launch vehicle. Courtesy of RPM Innovations Inc./NASA, and Relativity Space, respectively. Fig. 4 — Deposition heads can be mounted on either (a) robotic arms or (b) CNCmachines. Courtesy of NASA/DM3D Technology, and RPM Innovations Inc./NASA, respectively. aluminum, as well as refractory alloys[12-14]. DED also enables deposition of multiple materials within the same setup, providing unique design solutions to optimize component-specific requirements for thermal, electromagnetic, pressure, loading, and dynamic properties. Deposition rates for DED processes can approach 9 kg/hour depending on component geometry, greatly reducing manufacturing time compared to other methods. In addition, less material is wasted because parts can be built to near-net shape in contrast to the subtractivemachining required by forgings. LARGE-SCALE BUILDS The ability to print large-scale structures is enabled by integrating the MAM DED deposition head with either a robotic arm or CNC controller platform, as shown in Figs. 4a and b, respectively. Directly mounting the deposition head onto the appropriate platform allows operation in an open-air environment using only localized shielding gas to prevent oxidation. Several DED systems that use laser as an energy source are integrated with an enclosed structure to allow for a fully inert environment, necessary for reactive alloys such (b) (a) (b) (a)
RkJQdWJsaXNoZXIy MTYyMzk3NQ==