Melt Pool Width Measurement in a Multi-Track, Multi-Layer Laser Powder Bed Fusion Print Using Single-Camera Two-Wavelength Imaging Pyrometry

Abstract

Abstract In laser powder bed fusion (LPBF) additive manufacturing, melt pool characterization is one of the potential approaches toward rapid process qualification and efficient non-destructive evaluation of printed parts. Especially melt pool width measurement is crucial for understanding the print process regimes, estimating the solidified melt pool depth, and identifying any process anomalies, among other attributes of interest. While existing works focus on monitoring melt pools of single scan tracks or single layer prints, melt pool characterization for a multi-track multi-layer (MTML) LPBF print has not been extensively studied. In this work, we employ our lab-designed coaxial single-camera two-wavelength imaging pyrometry (STWIP) system to monitor in situ melt pool properties during a MTML LPBF process. The STWIP-measured melt pool widths are validated using a serial sectioning machine (Robo-Met, UES). The in-situ STWIP and ex-situ Robo-Met measurement data are in close agreement with each other, having a mean absolute error and root mean squared error of 9.83 µm and 16.53 µm, respectively. Further we demonstrate the successful mapping of melt pool location and melt pool size on the printed MTML part. In sum, this work demonstrates the capability and the applicability of STWIP for accurate large-scale melt pool monitoring during LPBF processing of practical parts, thereby facilitating the development of LPBF process models and control strategies.