New Mexico’s Optomec has reached what it is calling a “major milestone” for its Laser Engineered Net Shaping (LENS) direct energy deposition (DED) process. Catering to the popular heat exchanger market and other high-conductivity applications, the company has developed process parameters for the production of pure copper parts. Incredibly challenging for laser-based processes due to the inherent reflectivity of copper, this advance is the latest of many initiatives undertaken by metal additive manufacturing stakeholders to introduce the material to the market.
Tom Cobbs, product manager for Optomec LENS systems, comments, “We see this as a major milestone for LENS and DED additive manufacturing — because working with copper is essential for many of our customers.
“Copper is so critical because it enables the addition of high thermally-conductive features like cooling fins, the addition of soft metal sealing surfaces and high electrically-conductive surfaces for power transmission.”
Additive manufacturing in copper
A malleable and ductile material with high thermal and electrical conductivity, copper is used widely in circuitry, electric wiring, and architecture. Certain alloy formulations of copper are also applied to the production of next-generation rocket components, including the combustion chamber for Launcher’s E-2 rocket engine – reportedly the largest liquid rocket engine combustion chamber 3D printed in a single part.
Additive manufacturing in copper gives manufacturers all the usual benefits, i.e. more geometric freedom, less wastage, lower cost for short-run parts, but processing the material has proved challenging to many metal methods. “The infrared wavelengths on most standard, laser-based AM systems are not readily absorbed by copper, making it difficult to establish a melt pool as the laser energy is reflected back into the source, causing all kinds of havoc,” explains Cobbs.
In response, initiatives including “SLM in green” from the Fraunhofer Institute of Laser Technology ILT, and the TruPrint 5000 3D printer from TRUMPF, have opted to use a green laser instead. Conversely, Chinese OEM Farsoon Technologies has adopted its own pure copper 3D printing technology without the use of a green laser the “secret” it says, is in an open platform ethos.
Optomec’s LENS technology is ready-made to surpass the challenges faced by 3D printing in pure copper. “Our laser-based solution is virtually immune to any back reflection, so the laser can operate at full power on reflective surfaces without any difficulty,” comments Cobbs. Now, he adds, “Optomec engineers have developed process parameters to account for thermal conductivity differences, as well as big changes in absorption.”
The team has successfully applied this development to the production of 3D printed pure copper parts which were displayed at Formnext 2019. In the future, the process may also be used to 3D printed other copper alloys such as bronze, brass, and cupronickel.
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Featured image shows Optomec DED based LENS technology 3D printing onto a premade metal surface. Photo via Optomec