Phase congruency melt pool edge extraction for laser additive manufacturing

Melt pool geometry, as one of the most important built attributes that reflect the stability of an additive manufacturing process, has been widely used for process monitoring and process control. Currently, intensity-based gray-level image processing is generally used to extract the melt pool boundaries. However, selection of proper threshold is challenging due to the intensity-related noise and disturbance from blurred areas, flares and speckles. This paper presents a phase congruency melt pool edge extraction approach that performs well for phase-invariant but intensity-variant image boundary extraction. The results show that the phase congruency edge extraction approach can not only robustly handle disturbances from blurred areas, flares, black areas and incandescent droplets, but also obtain more accurate melt pool geometries. A real-time melt pool monitoring system is developed to monitor a geometrically dependent and time varying melt pool evolution during an additive manufacturing process.