FEATURE: ADDITIVE MANUFACTURING
the approach produced dense structures. ‘The real challenge was to come up with a balance between optimum density, but also an efficient process,’ Carter explained. Initially their additive manufacturing
approach sacrificed a little density, which Stratasys Direct later increased using a hot isostatic pressing thermal process.
Printing pure copper While their efforts show that existing 3D printing technology can work with copper alloys, copper itself is a bigger challenge. Consequently, engineers are improving the available techniques to launch this material into the market, while at the same time further boosting copper alloy methods. Among them is Thomas Stoll, who works
in Joerg Franke’s team at the Institute for Factory Automation and Production Systems (FAPS) at the Friedrich-Alexander- University of Erlangen-Nuremberg,
“A widespread portfolio of different geometries and materials gives AI the chance to learn optimal process parameters”
Germany. He highlighted that because copper quickly conducts heat away and reflects incoming infrared laser light, it means high-energy densities must be input to melt it. He added that even laser powers up to 1kW cannot reach 97 per cent of the density of bulk copper when fusing powder. ‘Cross sections of those specimens show regular pores that hinder the usage of the material for industrial applications,’ he said,
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noting that the main issue is that the laser spot size is too big. This could be due to factors such as the laser heating up the focusing lens, too great a focal length on the focusing optics, or that the diameter of the beam before focusing is too narrow. The net result is ‘laser intensity too low to create a sufficient melt pool’, Stoll explained.
AI-assisted 3D printing Stoll and his colleagues worked on this issue, considering optical process control with pyrometric cameras to control laser beam melting. ‘The thermodynamics are not totally understood,’ Stoll admitted. He has found that process factors influence the dynamics of material-light-interactions in different material states, spanning melt, solid and powder. ‘Moreover,’ he continued. ‘Different geometries need different parameter settings due to different heat distributions and vector lengths. Here, AI in
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