Advanced powder flow regulation in DED-LB/P and EHLA3D via a novel nozzle-integrated fluidic powder switching mechanism

In this work, a novel fluidic powder switch is developed, featuring an innovative design that enables near-instantaneous switching of a powder flow. Unlike conventional solutions, the fluid-based mechanism eliminates the need for mechanical switching elements in the powder conveying line, reducing system wear and enabling direct integration into a Laser Material Deposition (LMD or DED-LB/P) nozzle. The present work focuses on the evaluation and systematic assessment of the main functionality of toggling of a focused powder gas jet by analyzing switching times, delays caused by system inertia, and the stability and repeatability of the switching process. Measurements in a dedicated experimental setup show that a stable powder flow is consistently achieved within <200 ms, while powder deactivation occurs within <40 ms, highlighting the system's responsiveness and suitability for highly dynamic LMD and extreme high-speed laser material deposition processes. A high repeatability was demonstrated with rapid switching trials showing a standard deviation of as low as 1.74 and 24.1 ms between switching cycles for "time to powder on" and "time to stable powder flow," respectively. In direct comparison with a commercially available mechanical powder switching system, the fluidic solution presented in this work demonstrated an improvement in responsiveness of approximately 83% under identical test conditions.