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

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Abstract
In this study, melt pool radiation monitoring and signal denoising in laser powder bed fusion 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. Further, variational mode decomposition method is used to obtain radiation signal components related to the melt pool region or non-melt pool region. The radiation of the non-molten 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 ~110Hz. 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.
Funding Information
  • National Natural Science Foundation of China (81772428, U2001218)
  • Special Support Foundation of Guangdong Province (2019TQ05Z110)
  • Basic and Applied Basic Research Foundation of Guangdong Province (2020B1515120013, 2022B1515120066)

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