Electron-optical in-situ metrology for electron beam powder bed fusion: calibration and validation

A major advantage of metal additive manufacturing is the possibility for tool-free production of complex shaped parts. Currently, the geometrical and dimensional accuracy of these parts can only be reliably controlled by time and cost intensive post-process inspection, e.g. using x-ray computed tomography (XCT). The current investigation demonstrates the first in-situ metrology technique for electron beam powder bed fusion (PBF-EB) using electron-optical imaging (ELO). After a calibration experiment, the approach was validated for a PBF-EB build job by comparing in-situ ELO imaging data to XCT data of an as-built part. The quantitative comparison showed a remarkable high agreement between both imaging techniques. It is demonstrated that ELO imaging is capable of making accurate predictions on the geometrical and dimensional accuracy of the as-build part. This result is the basis of new possibilities for in-situ process and quality control in PBF-EB.