Optical Coherence Tomography (OCT) for Real-time Layer Thickness Monitoring in High-speed Laser Metal Deposition Process = Optische Kohärenztomographie (OCT) zur Echtzeit-Überwachung der Schichtdicke beim Hochgeschwindigkeits-Laser-Metallabscheidungsverfahren

In the field of Laser-based Directed Energy Deposition (DED-LB) processes, real-time process monitoring is a critical aspect that ensures the quality and integrity of the final product. While established methods exist for monitoring other process signatures such as melt pool size and temperature, the monitoring of the layer thickness presents a unique challenge, especially for processes which require layer thicknesses down to 50 µm and speeds higher than 20 m/min. This contribution delves into the complexities of real-time layer thickness monitoring in the High-speed DED-LB process, like the Ponticon’s 3D Dynamic Material Deposition (3DMD) process. The 3DMD process, characterized by its high speeds of up to 200 m/min and the need for a precise standoff distance maintenance, necessitates a fast responding and robust method for layer thickness monitoring. Existing solutions, such as post-layer completion laser scanning and the use of lateral and coaxial triangulation systems, have been explored. However, these methods often come with limitations. Layer thickness is also difficult to predict from other monitoring variables, such as temperature and melt pool size. ... mehrHence, the research of an alternative and more robust method is of great industrial interest. This research introduces the use of an Optical Coherence Tomography (OCT) system integrated into the Ponticon pE3D machine, comparing it to other layer height measurement techniques like line laser scanner. The OCT system has demonstrated its capability to accurately monitor the layer thickness in real time and to detect process shifts or drifts due to variations in process parameters or geometric characteristics of the manufactured part as soon as they occur. This demonstrates the feasibility of effectively using the OCT system for monitoring the layer thickness in the High-speed DED-LB process, opening the way also for the active control of the layer thickness in the 3DMD processes. This contribution aims to demonstrate the potential of the OCT system in overcoming the challenges of layer thickness monitoring in the High-speed DED-LB process, paving the way for significant advancements in Metal Additive Manufacturing.