In-Situ Thermographic Inspection for Laser Powder Bed Fusion
Laser powder bed fusion is strongly influenced by the quality of the powder layer including the powder properties as well as the layer thickness. In particular, thermal stresses can produce sufficient part deformation to the point that a part interferes with the wiper. This paper investigates the use of long-wave infrared thermography to monitor the surface temperature of the build. When cold powder is spread by the wiper, heat diffuses from the underlying part through the powder. The surface temperature history is a strong function of the thermal transport properties of the powder as well as the thickness. This correlation is explored and measured experimentally. It is then used to estimate the powder layer thickness above overhanging parts. This approach is shown to capture the part distortion and predicts wiper state prior to catastrophic interaction with the part.