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Green Lasers: The Best Kept Secret in Additive Manufacturing

Jan 11, 2024

Parts printed in 3D are now on another planet, deployed to Mars on the Perseverance Rover. This shows the growth in how additive manufacturing (AM), the other term for 3D printing, is being used to produce space exploration components, including propulsion devices and structural components. For propulsion of launch vehicles, specifically rocket engines, the advantage of using laser AM is great.

The benefits of AM include reducing the overall number of engine parts, simplifying designs, printing cooling channels with unique overhanging angles, and improved thrust. Another plus is that dealing with tens of parts, in contrast to hundreds of parts, reduces the risk of manufacturing flaws. As a result of using better materials designed specifically for AM, improved heat capacity and strength can be obtained, enabling greater engine efficiency. Improved engine efficiency can translate into achieving higher orbit or transporting larger payloads.

Additive manufacturing opens up more flight windows, and with them greater access to space.

One particular innovation in laser AM—and probably the best kept secret in additive manufacturing—is the deployment of green lasers. Using a wavelength in the visible spectrum of 515 nm (as opposed to near-infrared or NIR at 1063 nm), enables laser additive manufacturing of highly reflective materials such as copper, aluminum, gold, silver, platinum and iridium to be more effective and efficient. In combination with these reflective materials, NIR lasers have a hard time coupling the beam to the metal and can result in reflective losses, an unstable melt pool, spatter and resultant porosity in the printed part. Developed on the traditional laser cutting and welding side, green laser technology, when applied to 3D printing, makes more sense for processing such materials. Green laser technology achieves results with better density, lower porosity, better surface finish, less spatter and improved productivity. Depending on the part and parameters used, it can be up to ten times faster than an IR laser source with pure copper powder.

The interest in copper and copper alloys has been led by NASA's Rapid and Analysis Manufacturing Propulsion Technology (RAMPT) program, which uses IR lasers to print thrust chambers using laser powder bed fusion (also called LMF—laser metal fusion). The improvement in thermal conductivity of copper compared to nickel alloys is a compelling reason to explore using it for this application. Other private launch companies such as Launcher and Virgin Orbit have also produced large copper alloy-based components by both powder bed processing and laser DED (directed energy deposition—also called LMD for laser metal deposition). Implementing a green wavelength laser on a highly reflective material like copper, is clear—it improves print quality and speed.

For the copper alloys currently being investigated (C18150, GR Cop 42, GR Cop 84 and more), it would follow that better productivity offering a faster print speed with fewer defects would be another contributor to better access to space. TRUMPF has also been working to develop copper parameters using green laser additive processes, using both powder bed fusion and laser DED or LMD.

Closing the manufacturing loop for space exploration, reducing lead time by using additive technologies in these processes results in a greater number of flight windows for the final vehicle. The increased availability of flight windows, higher orbits, and larger payloads opens up more opportunities to go into space, whether it be for space tourism or to deliver communication devices, probes, telescopes and more. It is an exciting time to be involved in space exploration and now the secret is out. Green laser technology is the key to unlocking space.

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Eliana Fu