Additive manufacturing of complex structures and flow channels using wire-arc thermal spray

The development of a cost-effective additive manufacturing method for millimeter-scale metal structures is essential for the fabrication of novel, high-efficiency heat exchangers and heat sinks. The millimeter-scale fluid channels produced by these structures provide a large surface area to promote heat transfer while minimizing system volume and mass. Traditional additive manufacturing methods are limited by their high cost, high energy consumption, and long processing times. This study presents an efficient additive manufacturing method by using wire-arc thermal spray through a polymer mask. Aluminum and copper structures with arbitrary shapes and a height of 1.3 mm were deposited on a plate 74 mm × 51 mm in size in 30 min and 15 min, respectively. Masks were fabricated by 3D-printing with a high-temperature photopolymer resin. All fabricated structures exhibited a dense center region, a porous side wall region, and a porous satellite particle region between deposited structures. The development of the deposited structures throughout the process is investigated for aluminum (having a low density, surface tension, and melting temperature) and copper (having a high density, surface tension, and melting temperature). The influence of the distance between the mask and the substrate on structure geometry and porosity is studied. The fabrication steps of a liquid-cooled mini-channel heat sink containing an enclosed flow channel are demonstrated using the proposed additive manufacturing method. The results suggest that using wire-arc thermal spray through a polymer mask can be used as a cost-efficient method to additively manufacture metal structures on the millimeter scale.