Immediate development of processing windows for selective electron beam melting using layerwise monitoring via backscattered electron detection

Electron-Optical In Situ Imaging for the Assessment of Accuracy in Electron Beam Powder Bed Fusion

“…Besides process optimization, ELO imaging is a very promising approach for general monitoring of the PBF-EB process, especially in an industrial environment. This has already been shown for the prediction of internal defects [ 48 , 49 ] and the dimensional accuracy [ 35 ]. The current investigation reveals that ELO imaging may also contribute to monitoring of surface roughness.…”

In-situ layerwise monitoring of electron beam powder bed fusion using near-infrared imaging

“…Thus, samples produced with a line energy lower than 0.14 J/mm were porous (P) and those produced with a line energy above 1.08 J/mm were uneven (U). Thus, as already suggested by Pobel et al [9] with in-situ electronic images, NIR-images could be helpful to determine the processing window for a new material in a more efficient way. In addition, as it is possible to modify beam parameters during the build, healing of defects during processing the next layers can be studied.…”

“…Such detectors can be positioned near the bottom of the electron gun as reported by Arnold et al [7], or implemented on heat shields (metallic panels 3 designed to limit radiation heat losses) as suggested by Wong et al [8]. The ability of in-situ electronic imaging to provide information about part geometry, surface topology, and typical defects such as pores or uneven surfaces was demonstrated, see in particular Pobel et al [9] and Wong et al [8]. However, up to now, it turns out to be difficult to infer thermal information of the layer to be processed from electronic images.…”

In Operando Monitoring by Analysis of Backscattered Electrons during Electron Beam Melting

“…[13,14] By recording the topography of the molten surfaces, it was demonstrated that image features and defects inside the final sample may be correlated [13] and that this finding may be used to deduce processing windows in a fast and reliable manner. [15] The installed BSE detector was robust against elevated temperatures, metallization, and X-ray radiation and delivered high-contrast images. Despite all benefits of this in situ ELO approach, it requires an additional process step for image acquisition and is only capable of imaging the final molten surface.…”

“…It was shown that electron optical (ELO) images may be obtained using the electron beam in a way comparable with scanning electron microscopy . By recording the topography of the molten surfaces, it was demonstrated that image features and defects inside the final sample may be correlated and that this finding may be used to deduce processing windows in a fast and reliable manner . The installed BSE detector was robust against elevated temperatures, metallization, and X‐ray radiation and delivered high‐contrast images.…”