Physics-Based Inversion of a Millimeter-Wave Diagnostic for Liquid Metal Additive Manufacturing

This letter presents a physics-based inversion technique for reliable characterization of droplets deposited by a liquid metal jetting additive manufacturing system, using an in-situ millimeter-wave (mm-wave) diagnostic. The overall approach is demonstrated in a custom droplet-on-demand liquid metal jetting system with effective droplet diameters ranging from 0.8 to 1.7 mm. The inversion results demonstrate that this approach can provide information about the droplet size and lift-off distance between the droplet and the diagnostic by monitoring the amplitude and phase of the reflection coefficient at the input port.