2024 Annual International Solid Freeform Fabrication Symposium (SFF Symp 2024): Special Session: Metal Jetting and Droplet Deposition Processes I
Program Organizers: Joseph Beaman, University of Texas at Austin

Monday 1:30 PM
August 12, 2024
Room: Salon B
Location: Hilton Austin

Session Chair: Denis Cormier, Rochester Institute of Technology

1:30 PM
Towards Sustainable Fabrication of Electronics via Molten Metal Jetting: Negar Gilani¹; Nesma Aboulkhair¹; Marco Simonelli¹; Mark East¹; Richard Hague¹; ¹University of Nottingham
    Drop-on-demand Molten Metal Jetting (DoD-MMJ) is gaining growing attention for its flexibility and versatility in additively fabricating sustainable microelectronic components. However, the use of this method with high-melting-point copper has been scarce due to processing challenges. In this study, an in-house DoD-MMJ platform, MetalJet, was used to explore the generation and deposition behaviour of Cu microdroplets onto ceramic and metallic substrates. Concurrently, droplet dynamics, solidification kinetics, microstructural evolution, and interface formation were investigated using a combined computational and experimental approach. Our findings underscore the critical role of controlling oxygen content to mitigate nozzle-level reactions during droplet formation. Despite the inherent poor wettability, Cu droplets exhibit adhesion to alumina surfaces facilitated by an interlocking mechanism. Notably, MetalJet-printed pillars demonstrated electrical resistivity as low as 6.75 ×10^(-8) Ωm. These outcomes mark a substantial advancement in the direct printing of functional components, signalling promising avenues for future research and industrial applications.

1:50 PM
Numerical and Experimental Advances In Piston-Actuated Molten Metal Droplet Jetting: Kareem Tawil¹; Irtaza Razvi¹; Chris Chungbin¹; Daniel Cormier¹; David Trauernicht¹; Zipeng Guo¹; Denis Cormier¹; ¹Rochester Institute of Technology
    Additive manufacturing via drop-on-demand (DOD) Molten Metal Jetting (MMJ) has seen significant technological advancement in recent years. Successful DOD-MMJ systems have utilized magnetohydrodynamic, pneumatic, and piezoelectric actuation to produce controllable and repeatable molten metal droplets. We propose a novel direct-drive piezo actuated piston mechanism capable of high-frequency DOD jetting of high-temperature molten metals. Droplet generation as a function of the dynamic system response is analyzed through a combined experimental and numerical study. Results show that tunable molten metal droplets can be repeatably produced with small displacement and high acceleration of the piezo-piston system without the need for mechanical amplification or supplemental pneumatic pressure. The potential benefits of this technology, including high-frequency jetting and droplet property optimization, are discussed.

2:10 PM
Rapid Screening of Liquid Metal Wetting for a Materials Compatibility Library: Shahryar Mooraj¹; Viktor Sukhotskiy¹; Alexander Baker¹; Connor Rietema¹; Jesse Ahlquist¹; Hunter Henderson¹; Andrew¹; ¹Lawrence Livermore National Lab
     Droplet-on-Demand additive manufacturing (DODAM) techniques have the ability to produce high resolution near-net-shaped parts which require minimal post-processing. A key requirement to ensure efficient and consistent ejection of droplets through the nozzle of a DODAM nozzle is to tune wetting behavior of the liquid metal with the body and orifices. Wetting of liquid metals is highly dependent on the compatibility with nozzle materials, influenced by various operational conditions such as the nozzle temperature, atmospheric composition, reactivity of liquid metal and nozzle etc. This work presents a screening approach to build a materials compatibility library that enables the DODAM community to understand the wetting conditions of various material combinations under precisely controlled operating conditions to support material selection for nozzle materials to maximize the jetting efficacy of materials. Results of compatibility studies for tin, aluminum, and copper will be presented, and their implications discussed.Prepared by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-863442

2:30 PM
Overcoming the Resolution-Deposition Limit of Additive Manufacturing with Droplet-on-Demand Molten Metal Jetting: Viktor Sukhotskiy¹; Andrew Pascall¹; Jason Jeffries¹; ¹Lawrence Livermore National Laboratory
     Like most additive manufacturing (AM) methods, droplet-based molten metal jetting (MMJ) techniques suffer from a fundamental trade-off between resolution and speed. This trade-off naturally manifests limits to the fabrication of parts. We will present some of these limits and propose a novel method to circumvent them: multi-resolution metal AM via magnetohydrodynamic (MHD) droplet-on-demand MMJ. Multi-resolution MMJ enables high resolution and high deposition by selectively ejecting metal droplets of varying size from a single nozzle with two orifices. Smaller orifices enable fine resolution features at the expense of deposition rate. Conversely, larger orifices allow rapid printing of coarser features. By tailoring MHD pulses to the characteristic fluid dynamics of each orifice, we can select the ejecting orifice at will. We establish the concept using 3D fluid dynamics simulations of a nozzle with 200 and 500µm diameter orifices and validate experimentally using an aluminum alloy.Prepared by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-863319

2:50 PM
Molten Metal Jetting (MMJ) A356 and 6061 Heat Treatment, Tensile Properties, and Fracture: Dinesh Krishna Kumar Jayabal¹; Mariusz Mika¹; Paul McConville¹; Priya Guggilapu¹; Brendan McNamara¹; Chu-Heng Liu¹; Srirarm Manoharan¹; Dinesh Jayabal¹; ¹ADDiTEC
    Molten Metal Jetting (MMJ) is an economical method of producing parts that consist of different materials. In order to maximize the benefit of such alloys a heat treatment process is proposed and characterized.

3:10 PM Break

3:40 PM
GMP300 - Influence of Process Parameters on Material Properties: Johannes Glasschroeder¹; Maximilian Dropmann¹; ¹GROB-Werke GmbH& Co. KG
    Molten Metal Printing technology offers the possibility of economically producing near-net-shape aluminum components. In particular, the high system flexibility and the short process chain compared to conventional metal processes enable the rapid production of individual parts or small batches. With its GMP300 production system, GROB-Werke offers an industrial system for processing various aluminum alloys. Droplets are generated with the aid of a piezoelectric element in combination with a plunger. The droplets are deposited on a heated build plate under a defined inert gas atmosphere. The presentation focuses on the influence of different process parameters on the material properties. The alloy EN-AW 4047 was used as basic material. Parameters for droplet generation and droplet deposition were varied and their effects analyzed using micrographs and tensile tests.

4:00 PM
Processing Aluminum Alloys with Piezoelectric Driven Liquid Metal Printing: Julia Forster¹; Ismail Uensal¹; Christian Scheidter¹; Georg Schlick¹; ¹Fraunhofer IGCV
    Liquid Metal Printing (LMP) belongs to the group of metal-based additive manufacturing processes, where components are built up layer by layer through repetitive material deposition. In contrast to most fusion-based methods, LMP does not require a beam source for material melting or powders, as the material is supplied as wire, melted in a crucible, and deposited drop by drop. Utilizing a piezoelectrically driven actuator, near-net-shape manufacturing with droplet diameters ranging between 500 µm and 750 µm are achievable. Overall, the advantages of LMP enable efficient, cost-effective, and high-quality component manufacturing. This paper focuses on establishing and qualifying, industry-relevant aluminum alloys to leverage LMP´s potential for industrial production and applications in lightweight construction. Using the example of AlSi12, potentials and challenges regarding manufacturing parameters and mechanical properties are delineated. Based on this, requirements are derived to process higher magnesium-containing alloys such as AlSi10Mg and EN AW-7075 in the future.

4:20 PM
Molten Metal Jetting for Repairing Aluminum Components: Eric Elton¹; Benedikt Kirchebner²; Kellen Traxel¹; Alexander Wilson-Heid¹; Andrew Pascall¹; Jason Jeffries¹; ¹Lawrence Livermore National Laboratory; ²Technical University of Munich
    Molten metal jetting (MMJ) deposits droplets of liquid metal to additively manufacture parts droplet by droplet. As material is only deposited where required, MMJ may lend itself to repairing damaged parts. Here we use MMJ to fill in machined grooves on cast aluminum plate to understand how cast parts can be repaired. We find the groove shape has a significant role in “repairability” with round grooves being easier to fill in than other groove shapes. Finally, we compare the tensile strength of repaired and as cast tensile bars. Repaired tensile bars have reduced tensile strength likely caused by the inherent heating during the MMJ process. When post-print heat treatments are performed, tensile strength is regained in repaired parts. Prepared by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-1095114.

4:40 PM
PowderJet: An Agile System for High Quality Metal Powder Production: Viktor Sukhotskiy¹; Alexander Baker¹; Jesse Ahlquist¹; Eric Elton¹; Alexandre Reikher¹; Hunter Henderson¹; Shahryar Mooraj¹; Andrew Pascall¹; ¹Lawrence Livermore National Laboratory
     Leading metal additive manufacturing (AM) techniques require specially prepared spherical metal powders to produce high quality functional parts. The performance of these parts depends on the quality and composition of powder, but powder production technologies have shortcomings including asphericity or porosity. Here we present a new powder-production platform, PowderJet, which produces metal powders in a controlled environment by ejecting arrays of liquid metal droplets through a multi-orifice nozzle using electromagnetic pulses. This approach fundamentally differs from traditional stochastic powder-production methods, since powder size, distribution and purity are tightly controlled. We discuss system operation, performance, and key tunable parameters through a joint experimental and computational fluid dynamics framework. We also discuss initial results with Al, Cu, and Ce powder production. PowderJet will accelerate discovery and optimization of alloys for AM through bespoke powder production.Prepared by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-863309

5:00 PM
Developing a Comprehensive Printability Window for Reliable Molten Metal Droplet-on-Demand Manufacturing: Nicholas Watkins¹; Viktor Sukhotskiy¹; Phillip Paul¹; Jason Jeffries¹; Andrew Pascall¹; ¹Lawrence Livermore National Laboratory
     Molten metal droplet-on-demand additive manufacturing is a promising alternative to laser-based methods as it is compatible with a large range of powder-free feedstock materials and provides a faster turn-around with minimal waste. However, this relatively new technique needs further investigation to fully understand jetting dynamics in the Weber jet and Ohnesorge parameter space that is well beyond that of traditional ink jetting (Oh > 10^-1). We have previously used molten metals to discover that satellite-free droplets can be formed at previously unexpected Oh (10^-3 to 10^-4). We now focus on the unexplored intermediate region (Oh from 10^-2 to 10^-3), where experiments and simulations reveal that additional jetting parameters such as printer actuation and fluid pinch-off timescales may be needed to describe the printability space more fully. These additional parameters may provide a more comprehensive tool to inform any droplet-on-demand process with any material. Prepared by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-862829.