ABSTRACT
This chapter describes optical diagnostics employed for in situ, on-line monitoring of metal additive manufacturing (AM) processes. Diagnostics are sought that can be incorporated into a feedback loop that optimizes build parameters to minimize defects in the construction of high-quality components. Optical diagnostics have been utilized for real-time process monitoring in a variety of industrial processes to include laser cladding, laser beam welding, machining processes, and metal emission control. AM of metals employing solid free-form fabrication by plasma-transferred arc processing may also be used in larger format 3D printing. An optical technique devised for surface roughness characterization during a standard machining process might be adapted to AM monitoring. A brief overview of some basic relationships between typical AM process parameters is presented below in the context of Air Force Institute of Technology's work with Ti-6Al-4V and cobalt chromium molybdenum alloys in a powder bed, selective laser melting system.
