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In order to fabricate precise metal components by sequentially depositing molten metal droplets on substrate layer by layer, the perfect slice thickness of part model have to be obtained. In this paper, the influence of deposited layer thickness of droplets was investigated, and the deposited layer thickness was calculated by analyzing the relationship of the shape parameters of solidified droplet on the substrate. A simple and effective model was proposed to calculate and predict the slice thickness ( H s ). The calculation results show that the H s was only affected by droplet diameter ( D ) and solidification angle ( θ ). Based on this analysis, a thin-walled tube was fabricated with different slice thicknesses (263 μm, 306 μm, 320 μm,365 μm and 400 μm) on the condition of fixed droplet diameter (400 μm)and Solidification angle (121.5°), which indicate that the calculation method i is effective and feasible. On this basis, a complex micro honeycomb structure (4 mm in deposition direction), which was deposited by the 312 μm diameter droplets and the 87.5° solidification angle. The high dimensional accuracy (the relative error is 1.5–3.75%) has been obtained in deposition direction with the calculated slice thickness ( H s = 192 μm) according to calculated models. The work provides an effective method for optimizing slice thickness and improving the dimensional accuracy of the formed components by droplet-based freeform fabrication.

In aluminum alloy droplet deposition manufacture process, thermal warping, layering and hot cracking of formed 3D components are the most common defects, which have been found to be associated with the large temperature gradient and thermal stress concentration. To obtain insight into the common defects formation mechanism in metal micro-droplet deposition manufacture, a 3D transient finite element (FE) simulation model has been developed by the APDL(ANSYS) code and element birth-death technique. The distribution and variation of time-dependent temperature and thermal stress fields were predicted and the thermo-mechanical behaviors were analyzed in fabricating aluminum alloy 3D components. And then, a series of deposition experiments were conducted using 7075Al alloy droplets under the setting process parameters (same to the initial and boundary conditions). The results show that the experimental results basically agree with the simulation results of thermo-mechanical behaviors. The reliability and correctness of the simulation model were verified experimentally by the measured temperature field and the observation of thermal deformation and hot cracking of formed 3D component. The work provides a useful theoretical and experimental guide for optimizing metal droplets deposition manufacture.