A Study on the Correlation between Optical Emission Image Characteristics and Mechanical Properties in Metal 3D Printing Processes

In this study, optical emission image analysis was performed to investigate the correlation between process characteristics and mechanical properties in powder bed fusion (PBF) additive manufacturing. Optical emission images generated during the laser-material interaction process were acquired through an in-situ monitoring system integrated within the PBF equipment. Quantitative image analysis was conducted using grayscale-based intensity and bright pixel ratio measurements to evaluate optical emission behavior according to process conditions. The experiments were carried out under various laser powers, scan speeds, and build orientations using INCONEL 718 specimens fabricated by the PBF process. Mechanical properties including yield strength, tensile strength, elongation, and density were comparatively analyzed with the optical emission characteristics. The results showed that optical emission intensity and bright pixel ratio generally increased with increasing laser power. However, the mechanical properties did not exhibit a proportional relationship with the optical emission signals, and optimal mechanical performance was observed within specific process conditions. In particular, excessive optical emission behavior at high energy input conditions was considered to be associated with melt-pool instability and localized over-melting phenomena. The findings of this study suggest that optical emission image analysis can be effectively utilized as an in-situ process monitoring approach for evaluating process behavior and identifying optimal process windows in PBF additive manufacturing.