Building three-dimensional objects by deposition of molten metal droplets

摘要

Purpose - The purpose of this paper is to determine conditions under which good metallurgical bonding was achieved in 3D objects formed by depositing tin droplets layer by layer. Design/methodology/approach - Molten tin droplets (0.18-0.75 mm diameter) were deposited using a pneumatic droplet generator on an aluminum substrate. The primary parameters varied in experiments were those found to most affect bonding between droplets on different layers: droplet temperature (varied from 250 to 325℃) and substrate temperature (varied from 100 to 190℃). Droplet generation frequency was kept low enough (1-10 Hz) that each layer of droplets solidified and cooled down before another molten droplet impinged on it. Findings - In this paper, a one dimensional heat transfer model was used to predict the minimum droplet and substrate temperatures required to remelt a thin layer of the substrate and ensure good bonding of impinging droplets. Cross-sections through samples confirmed that increasing either the droplet temperature or the substrate temperature to the predicted remelting region produces good bonding between deposition layers. Originality/value - This paper used a practical model to provide reasonable prediction of conditions for droplet fusion which is essential to droplet-based manufacturing. The feasibility of fabricating 3D metal objects by deposition of molten metal droplets has been well demonstrated.