A novel selection method of scanning step for fabricating metal components based on micro-droplet deposition manufacture

Metal micro-droplet deposition manufacture technology has attracted wide interest for potential application in micro-structure fabrication. In order to fabricate functional metal components by sequentially depositing molten metal droplets on substrate layer by layer, the perfect overlapping and bonding strength among droplets have to be obtained. In this paper, the influence of scanning step on overlapping of droplets was investigated, and the critical overlapping condition of droplets was calculated by analyzing the relationship of the shape parameters of solidified droplet on the substrate. Four kinds overlapping states of adjacent droplets were predicted according to the change of scanning steps: no overlapping, partial overlapping, ideal overlapping and excessive overlapping. On this basis, two simple and effective models were proposed to calculate and predict the optimal scanning steps (W _XP and W _YL). The calculation results show that the W _XP and W _YL were only affected by droplet diameter (D) and solidification angle (θ). Based on this analysis, a pneumatic droplet generator was used to produce uniform molten Sn60Pb40 alloy droplets with specific diameters (256 μm, 400 μm and 700 μm), and a series of deposition experiments were carried out with different scanning steps on the condition of fixed droplet temperature (270 °C) and substrate temperature (90 °C). The experimental results show that good overlapping and bonding strength of adjacent droplets could be obtained in deposited lines and layers, and low porosity and high density three-dimensional metal component was fabricated with optimized experimental parameters (W _XP and W _YL) according to theoretical models. The work can provide useful theoretical and experimental guide for metal micro-droplet deposition manufacture.