Tailored droplet deposition strategies for direct printing of fully functional components via molten metal jetting

Molten Metal Jetting (MMJ) is an emerging metal additive manufacturing technique with significant potential across various industries such as electronics, healthcare, aerospace, and robotics. In this process, components are built by depositing molten droplets one by one to form a 3D structure. Ensuring void-free deposition is essential for achieving high density, structural integrity, and electrical conductivity in printed parts. Despite its promise, current research lacks effective methods to fully eliminate internal voids which undermine the performance and functionality of the printed parts. This paper introduces a novel approach that applies tailored droplet deposition techniques to directly produce functional parts via MMJ, without the need for post-processing. Using tin as the printing material, this study evaluates density, electrical conductivity, and surface roughness in samples produced with four distinct methods at substrate temperatures of 150 °C, 100 °C, and 50 °C. The results show that each substrate temperature requires a specific approach, and the identified methods achieve fully dense, highly conductive, and smooth-surfaced parts. Furthermore, a method for printing on a low-temperature (50 °C) substrate was developed, effectively mitigating the influence of residual stress and enabling the fabrication of temperature-sensitive components. This research bridges a critical gap in MMJ by enabling the direct production of fully functional parts, paving the way for broader industrial applications of this technology.