In Situ Monitoring of Melt Pool and Signal Modification in Laser Powder Bed Fusion

In this study, melt pool radiation monitoring and signal denoising in laser powder bed fusion (LPBF) is carried out. Photodiodes and semiconductor cameras are used to capture coaxial radiation signals and images of melt pools. The temperature of the melt pool rises as laser input energy increases, and the fluctuation of radiation signals caused by spatter intensifies. Furthermore, variational mode decomposition (VMD) method is used to obtain radiation signal components related to the melt pool region or nonmelt pool region. The radiation of the nonmolten pool region (i.e., noise) contains fundamental frequencies and related harmonics that can be decomposed into a low-frequency mode with a center frequency of
$\sim $
110 Hz. By comparing the correlation and the center frequency, the noise component is confirmed, and the original signal is modified accordingly. In this way, melt pool temperature accuracy is improved, enhancing melt pool behavior features.