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 similar to 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.

Automated summary

In this study, monitoring and denoising of melt pool radiation in laser powder bed fusion (LPBF) is conducted. By using photodiodes and semiconductor cameras, coaxial radiation signals and images of melt pools are captured. The temperature of the melt pool increases with laser input energy and the fluctuations of radiation signals caused by spatter intensify. To improve the accuracy of melt pool temperature and enhance the behavior features, the variational mode decomposition (VMD) method is employed to obtain radiation signal components associated with the melt pool region or non-melt pool region.