| Precision Droplet Manufacturing (PDM) is a process that grows complex 3D parts one nano-liter molten metal droplet at a time from a CAD file without the need for tooling. This dissertation explores four varied but important PDM issues.; First, to address the challenges of jetting and generating droplets from molten aluminum, an improved metal droplet generator is designed, analyzed, built, and tested. The introduction of a remote, conical resonator improves molten metal droplet generation by increasing disturbance amplitude and stability. Vibration analysis guided and refined the design. Second, novel calibration and build schemes are detailed that improve process setup and efficiency.; Third, component integrity is explored by simulating the droplet splat solidification process. The 1D finite difference simulation uses an analytic start and allows for re-melting of previously deposited material. Transformations are used to transform the moving boundary problem to a fixed boundary problem. Re-melt depth as a function of process parameters is thoroughly investigated, and an analysis of realistic parameters for building with aluminum indicates successful inter-droplet splat bonding is feasible. Also, solidification rates verify PDM's classification as a rapid solidification process. In addition, multi-droplet simulations demonstrate that droplet splat stacking is sustainable, that is, it is possible for droplet splats to always solidify fully before the next droplet arrives.; Lastly, an in-flight convective droplet heater was designed and tested using helium and nitrogen as the convective agent and heating rates up to 11,000°C/s were attained. The effect of droplet spacing on heat transfer coefficient was experimentally detailed and an unexpected nascent-turbulent effect was observed. In addition, comparisons with previous multi-droplet numerical simulations were favorable. |
