Research on mechanism of generating aluminum droplets smaller than the nozzle diameter by pneumatic drop-on-demand technology
Droplet-based manufacturing (DBM) process has great potential in directly fabricating metal parts. In order to enhance the practicability of DBM, decreasing droplet size becomes the research focus in this field. In the present work, a novel pneumatic-driven droplet generator structure was proposed and the mechanism of generating aluminum droplets smaller than the nozzle diameter was studied. By conducting simulation experiments, the effects of structure parameters on droplet formation process and droplet size were investigated. The results indicated that the aspect ratio of the nozzle hole (i) and the distance between inlet hole and nozzle hole (H 1) had significant effects on droplet size while the diameter of the inlet hole had little effect. Droplets smaller than the nozzle diameter could be produced only when i and H 1 were 1 and 1 mm, respectively. Based on the optimized structure parameters, a generator was developed and droplet-ejecting experiments were carried out. By using a nozzle with the diameter of 500 μm, aluminum droplets with the mean diameter of 359.9 μm were produced stably and then a rectangular tube was fabricated by depositing droplets sequentially. The results demonstrated the capability of the novel generator to produce small droplets and to fabricate parts directly.
KeywordsDroplet-based manufacturing Pneumatic driven Droplet generator Aluminum droplet Droplet formation
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