UC Irvine

This thesis includes two case studies on sustainable manufacturing: (1) Production of Metals for Additive Manufacturing; and (2) Brass Jewelry Manufacturing. Additive manufacturing (AM) produces components with complex geometries more efficiently and with higher material yields as compared to traditional material forming technologies. However, AM processes generally require fine powder with a narrow size distribution, which is expensive to produce, is energy intensive and its production results in a negative environmental impact. To address this challenge, we report on a study of the cost feasibility and environmental impact focusing on global warming potential and cumulative energy demand associated with the production of different powder feedstocks that are suitable for Laser Engineered Net-Shaping (LENS®), a directed energydeposition AM technique. LENS® is a widely used AM technique that requires metal powders as the starting feedstock. In our study, the associated costs, and environmental impacts from two commonly used AM materials, 316L stainless steel and AlSi10Mg, are analyzed. Moreover, we determined the economic costs of the various processing steps and the various factors affecting production, using techno-economic analysis (TEA). To evaluate the environmental impact associated with the different approaches used for powder feedstock production, we used life cycle impact assessment (LCIA). The results of the TEA and LCIA analyses demonstrate that amongst the various feedstock studied – gas atomized powder, recycled machine chip powder, and recycled gas atomized powder - recycled gas atomized powder provided the greatest economic benefit and lowest environmental impact. Our results provide a framework that can be used to assess how recycling can be implemented to reduce the costs and environmental impact of feedstock materials, and thereby enable the sustainable development of AM technologies. Brass alloys are frequently used in fashion jewelry due to their physical properties, such as color, shininess, toughness, corrosion-resistance, and ability to be crafted at low temperatures. However, brass jewelry commonly includes toxic metals, such as lead and cadmium. In the brass jewelry project, I explored the sustainable development of brass jewelry materials, specifically focusing on the associated casting, processing, and supply chain issues. Another goal is to identify the causes of negative impacts on human health or environmental quality, while exploring the potential to apply the principles of the circular economy. Evaluating the historical costs of materials to determine the cost of creating an alloy is crucial to the keeping the cost of brass jewelry down; however, when designing the alloy this perspective must be weighed against the sustainability of the materials involved, including the inputs and outputs of producing the material and potential toxicity of the material. If a material is cheap, but toxic it cannot be used. Likewise, if a material is environmentally sustainable, but expensive, it is not likely to be used. In the first case study regarding the production of metal feedstock powders for additive manufacturing, it is observed that machine chips powder and reused gas atomized powder both reduce the economic costs and environmental impacts of the powders used to construct AM products. This study shows the importance of being informed of how feedstock powders are produced and their affects. In the second case study regarding brass jewelry, brass alloy design is instructed by the sustainability of the materials involved. While not all metals are suitable for replacing current compositions in brass alloys, sustainable material selection is informed by selecting for the material properties, future and current availability, and environmental impacts of elements for brass jewelry compositions.