Enhanced geometric accuracy in directed energy deposition via closed-loop melt pool height control using real-time thermal imaging

Abstract

This study presents a closed-loop melt pool height control system based on real-time thermal imaging to enhance the geometric accuracy of directed energy deposition (DED). Geometric inaccuracies in DED-printed components arise from the inherent thermal and geometric variations during the printing process. To improve geometric conformity with a predefined digital model, the proposed system employs a long-wave infrared camera to capture real-time thermal images of the melt pool. The peak-to-boundary temperature difference (TD), defined as the difference between the peak and boundary temperatures of the melt pool, is extracted from these images. The correlation between TD, melt pool height, and laser power was analyzed under various DED conditions, and the results demonstrated a strong relationship between TD and both parameters. Using the TD as a feedback parameter, the laser power is dynamically adjusted to maintain a stable melt pool height throughout the printing process. The proposed system enables real-time estimation of the melt pool height, ensures height stability through closed-loop control, and provides detailed insights into the thermal and geometric variations that affect the accuracy of the final part. This approach reduces the geometric error relative to the predefined digital model to below 4 %, highlighting its effectiveness in enhancing the geometric accuracy in complex multi-bead, multi-layer structures.