A novel pneumatic drop-on-demand generator for producing micro aluminum alloy droplet

摘要

Pneumatic drop-on-demand (DOD) spray technology has great potential in directly fabricating complex metal parts and structural parts because of its capability in spraying high-melting-point metal.In our experiment,the primitive pneumatic droplet generator had defect of producing droplets stably because that the pulse pressure applied on molten metal varied as the liquid volume changed in the crucible.This disadvantage inhibited the widespread use of the technology.A novel structure for aluminum alloy droplet spraying was designed to overcome the above defect.In this structure,the driving gas which flowed into the crucible was divided into two channels.One was applied on the molten metal to force the liquid to fill the gap between the nozzle and the bottom of gas inflow tube.The other was directly applied on the thin liquid film between the tube bottom and the nozzle.Then the liquid was extruded from the nozzle to form droplet.The experiments of spraying droplets were conducted by using the novel and primitive generators.The statistical result of the droplet diameters showed that the droplets produced by the novel generator were 0.75times as small as the ones generated by the primitive generator with the nozzles of the same size.The standard deviation of droplets diameters was 27.672μm,indicating the stability of metal droplets generation by using the novel generator.A metal part with good surface finish and high density was fabricated by using the novel generator.The capability of the novel generator in directly fabricating parts was demonstrated.