Determining process stability of Laser Powder Bed Fusion using pyrometry

Abstract

This study investigates the significance of melt pool temperature data obtained through pyrometry in a metal Laser Powder Bed Fusion (L-PBF, SLM) process. In an open-loop process like SLM, process monitoring is key in both determining the process quality and preparing towards closed-loop process control. A two-color pyrometer is integrated into the laser beam path of an SLM machine, such that it collects emitted radiation from the melt pool and its vicinity. By this, and with proper calibration, the maximum melt pool surface temperature can be obtained in-situ and as an absolute value. Cuboidal specimens from 1.4404/316L have been manufactured with different processing conditions to provoke different process behavior. During the build, the pyrometer data was recorded. The study shows, that on-axis pyrometry is an appropriate instrument for melt pool and process monitoring in particular, it discusses potential sources of disturbance and highlights potential application in in-situ process monitoring.