Line-scan, fiber-based confocal sensing for surface characterization and thermal distribution monitoring in selective laser melting systems

Laser additive manufacturing of metallic materials may be improved by in-situ process monitoring. For example, determination of surface characteristics of the building layers and measurements of the temperature of the melting pool may be utilized in powder-bed selective laser melting systems. In this paper, we experimentally investigate the possibility of determining surface characteristics, specifically surface roughness, using a prototype setup comprising a fiber-based line-scan confocal optical system with a laser probe beam that operates at a low numerical aperture over at least 200 mm distance between its optical elements and the sample surface. A similar setup for thermal radiation, without the probe beam, was used to determine 2D thermal distributions at the melt pool and to demonstrate melt pool temperature stabilization.