Metal Powder Manipulation using Air-Coupled Ultrasound

In this work, we investigate the feasibility of using air-coupled ultrasound to manipulate piles of metal powders. It was shown that contact-based ultrasound can enhance the printing process of Powder Bed Fusion - Laser Beam/Metal (PBF-LB/M) [1]. While prior work has demonstrated ultrasonic manipulation of lightweight [2] or airborne particles [3], [4], it remains unclear whether static, dense metal powders, as used in PBF-LB/M, can be moved using air-coupled ultrasound. We present an experimental setup-based on a 40 kHz air-coupled ultrasonic phased array that emits 20 short bursts with a sound pressure level of 146 dB over a time frame of 2 s onto a predefined powder pile of aluminum, 316L steel, or copper. Surface profilometry before and after excitation measures the displacement difference in all cases. Aluminum with the lowest density shows the largest volume moved (112 mm³). Steel and copper powder have a higher density and are moved less by the ultrasonic beam with 22.60 mm³ and 33.16 mm³, respectively. These results show that air-coupled ultrasound can manipulate static metal powders and indicate potential for integrating air-coupled ultrasonic preconditioning into PBF-LB/M processes to enhance the printing process.