Browsing by Subject "Additive Manufacturing"

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    Modeling and Mapping of Microstructure of Powder Bed Laser Fusion Additive Manufacturing Hybrid Milling of Maraging Steel
    (2024-05) Knight, Erin
    Additive manufacturing, (AM), has revolutionized traditional manufacturing methods by allowing for more intricate and customized part manufacturing. Industries including aerospace and advanced tooling utilize metal AM to design and manufacture complex components with high quality and performance. This study focuses on powder bed laser fusion (PBLF) hybrid milling (PBLFM), which is an additive hybrid subtractive manufacturing approach (AHSM). This relatively new AM manufacturing approach has gaps in understanding the influence of the process parameters on the manufactured parts’ mechanical and physical properties. Hence, in this study, the Taguchi L9 Orthogonal array was used to design an experiment to evaluate the influence of the PBLFM major process parameters, (laser power, print speed hatch space, and layer thickness) on the resulting microstructure, energy density, and mechanical properties of Maraging steel. It was found that print speed and layer thickness are the top contributors to mechanical properties and microstructure variance. The resulting process map from this project can be used to guide engineers to design the optimal PBLFM parameters for any given application.
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    The Optimization and Development of Additive Manufacturing Strategies for High Performance Printed Electronics and Metal Interconnects
    (2021-11) Jochem, Krystopher
    Additive manufacturing strategies, including printing, provide tremendous potential to manufacture low-cost, high-performance electronic devices. While printed electronics have been prepared by a variety of traditional printing strategies including gravure and inkjet printing, these techniques face limitations including low lateral resolution and aspect ratio (feature height/feature width) and difficulty aligning multiple layers of functional materials to build complex electronic devices including diodes and transistors. Previous research in the Francis and Frisbie research groups at the University of Minnesota led to the development of the SCALE (Self-aligned Capillarity-Assisted Lithography for Electronics) process to address these limitations. This process combines high resolution UV micro imprinting of capillary channels and connected ink receiving reservoirs with inkjet printing of electrically functional inks into the reservoirs and spontaneous capillary flow which fills the connected capillary channels with the inks. By creating networks of carefully positioned capillary channels, the complex structures of electronic devices are deposited with higher resolution and layer-to-layer positioning accuracy than achieved with conventional printing methods. These strategies are fully compatible with roll-to-roll production, but this capability hadn’t been demonstrated prior to this work. In this dissertation, a process for roll-to-roll production of the plastic substrates patterned with SCALE capillary channels and reservoirs was developed using low-cost, roll-based imprinting stamps and common sources of air entrapment defects were identified and addressed. Low resistance, high precision metal interconnects were developed and optimized using these patterned plastic substrates. Variables affecting the conductor uniformity, flexibility, and reproducibility were identified and optimized to maximize the useful length and electrical performance of the conductors. This resulted in a fully roll-to-roll compatible manufacturing process for low resistance, flexible metal interconnects. A new, two level capillary channel geometry was developed for conductor fabrication to allow the production of solid metal conductors with flat tops, aspect ratios near 2, and precise feature edges, embedded in the plastic substrates. Finally, a roll-to-roll inkjet printing process was developed for full continuous manufacturing of SCALE devices, and silver SCALE conductors were prepared using this continuous process. This work develops strategies for full roll-to-roll production of SCALE devices and high-performance metal interconnects on patterned plastic substrates.
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    Performance Measures of Direct Metal Laser Sintering Hybrid Milling: Mechanical Properties and Environmental Performance Indicators
    (2019-07) Ahmad, Nabeel
    Applications of metal additive manufacturing (AM) has increased substantially because it allows cost and resources efficient small-scale production required in industries such as aerospace and mold and die manufacturing. Geometric and dimensional accuracy of parts produced by AM is still subpar compared to conventional subtractive approaches. Recently, hybrid additive-subtractive called direct metal laser sintering hybrid milling (DMLS-HM) technology has been introduced which combines strengths and robustness of both additive and subtractive units. This thesis explores the adoption consequences and impacts of DMLS-HM through relative performance measures of mechanical and metallurgical properties as well as environmental impact assessment. This was achieved by first characterizing mechanical properties of Maraging steel powder and comparing it with conventional DMLS to understand the degree of variability. It was found out that DMLS-HM has superior mechanical properties for impact toughness and surface finish; however, tensile strength and hardness values were similar with DMLS. Environmental performance assessment was achieved by first identifying and finding the energy requirements in subsystems (additive and subtractive) of DMLS-HM and then converting into equivalent carbon emission. Carbon emission results for DMLS-HM printed geometry were compared with two other manufacturing approaches namely electron beam melting and conventional milling which fabricated the same geometry. The DMLS-HM process showed higher energy consumption during the part production stage with an average 84% more than EBM and CM processes. However, the CM was dominant in energy consumption during the procurement stage with an around 70% more energy than DMLS-HM and EBM processes. The outcome of this research project will contribute to the understanding of basic physics of energy consumption in AM and can be used in suitable process selection and setting sustainable manufacturing goals.