关键词: 按需喷射, 均匀微滴, 快速成形, 微滴沉积, 界面失稳, 近壁微液膜, 气液两相流, 液滴夹带

Abstract: Generating uniform droplet on demand and assuring the accuracy of the droplet location are two key factors for forming high quality metal parts in the drop-on-demand droplet-based manufacturing process. The experimental methods are adopted to analyze the impact of particles lodging in the ejection nozzle on jet erratic and study the influence of process parameters on the uniformity of the droplets. Moreover, the size distribution of tin-lead alloy (Sn60%Pb40%) droplets obtained by using drop-on-demand spraying technique is discussed. The variation of the deposition accuracy with change of deposition distance is investigated. Furthermore, the accuracy of droplet location is discussed by depositing a 6×6 dots array on the substrate at appropriate deposition distance. The results show that the mean diameter and the corresponding standard deviation of the obtained droplets are 321 μm and 2.897 μm respectively. The diameters of about 99% of droplets is in the narrow range about ±2.8% of mean diameter, showing that the droplets with the narrow size distribution and good uniformity can be obtained. The offset distance also increases as the deposition distance increases. The accuracy of droplet deposited in dot array meets the requirement of metal droplet-based manufacturing. These works are useful for further study on the fabrication of minimized metal part.

Key words: Droplet deposition, Drop-on-demand, Rapid prototyping, Uniform droplet, entrainment, instability, micro-layer, two-phase flow