Page 34 - 3D Metal Printing Fall 2019

3D BACKTALK
By Louis A. Kren
Better Process Performance and Monitoring? Research Offers Hope
NASA has just released six emerging technologies in the space agency’s portfolio that it deems ripe for com- mercialization. The full list is available at www.tech- nology.nasa.gov, but two of these technologies relate directly to process control in metal additive manufacturing (AM): interim in situ AM inspection, and use of beam deflection to control electron-beam (EB) wire deposition. These R&D developments tackle issues in printing via powder and wire, and may help further mature these AM technologies
ing, and the need for such data to construct reliable models. No small task, it can be likened to weld monitoring, except instead of a single weld, monitoring in AM requires monitoring thousands of welds across layers with thicknesses measured in microns. Supplying parts in mission- and life-critical applica- tions means meeting FAA and FDA aerospace and medical acceptance. Sophisticated software and hardware are catching up to meet such process-monitoring challenges, so you can expect breakthroughs in this arena.
As for the use of beam deflection to control EB wire deposi- tion, NASA extolls the history of Langley Research Center in developing EB fabrication technology that uses an EB gun, dual wire feed and computer controls to create metallic struc- tures. For many years, Langley researchers report, no adequate means existed to maintain an even deposition height of the molten metal deposited by the system, thus leading to irre- versible material defects as layers are added. Technology devel- oped at Langley reportedly solves that problem, and provides solutions not only in industrial welding and fabrication appli- cations, but in small-component and large-structure aero- space applications, and may lead to rapid prototyping and as- needed manufacture of metal parts in space.
Here on earth, wire-fed EB metal AM can prove its worth in structural and part repair and manufacture of large parts. Use of wire provides numerous benefits, including availability of various materials, lower acquisition cost as compared to pow- der and high deposition rates relative to powder build, without some safety concerns inherent in powder storage and produc- tion. For some applications, wire-fed EB technology is the best bet.
Where these two specific research developments from NASA lead remains to be seen. Meanwhile, the promising nature of such research points out not only what is needed in metal AM, but also the possibility that solutions are in the offing.
Senior Editor lkren@3DMPmag.com
“Sophisticated software and hardware are catching up to meet such process- monitoring challenges, so you can expect breakthroughs in this arena.”
Regarding in situ inspection, NASA researchers at Mar- shall Space Flight Center observed few options avail- able for failure detection during the AM process, so they created their own. The system
designed at Marshall employs infrared and visual cameras to monitor the build process in real time.
“By monitoring the print, layer by layer, in real-time, users can pause the process and make corrections as needed, reduc- ing material, energy and time wasted in nonconforming parts,” according to a NASA release.
While the introduction of new systems for printing via metal continue to grab headlines—deservedly so as the technology progresses—methods for ensuring quality control must be a priority. The success of metal 3D printing as a production process depends on the ability to qualify materials, machines and procedures, and ensure repeatability in volume runs. Efforts on the metal powder end are summarized in Brad Kuvin’s editorial on page 4. Beyond powder quality, a trip to any industry event or conference reveals considerable effort across the AM landscape toward dependable in situ monitor-
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