Life cycle assessment of metal products: A comparison between wire arc additive manufacturing and CNC milling

The industrial progress made throughout these years has led to great results in terms of producing fast and with good quality. However, the impacts related to that production, whether these are environmental, economic, or social have been, at times, neglected. The manufacturing sector, as one of the most polluting sector, felt the urge to adapt to this industrial progress and find ways to produce with improved sustainability goals without compromising the quality of the final product and the production time. Industry easily understood the benefits of this greener approach, and, with this, new sustainable technologies started to emerge. Additive Manufacturing (AM) is one of those technologies that provide alternative sustainable paths to traditional manufacturing. In order to generalize the benefits of AM production in terms of sustainability, when compared to traditional processes, further investigations must be conducted. In this sense, the proposed work has the intention of finding the environmental impacts associated with a particular AM technique for the fabrication of metal parts, Wire Arc Additive Manufacturing (WAAM). A practical work based on the production of three different complexity metal parts considering an additive (WAAM) and a subtractive (Computer Numerical Control (CNC) Milling) manufacturing process is developed. To quantify the environmental impacts of both processes, the author resorts to the Life Cycle Assessment (LCA) methodology. The assessment is conducted in the SimaPro 9.2 software, accordingly to ISO 14044:2006 standard. The results allow a comparison between both types of manufacturing and enable the suggestion of measures to decrease the environmental footprint of WAAM. It was found that WAAM approach leads to a material saving ranging between 40% and 70% and an environmental impact reduction in the range of 12%–47%, compared to the subtractive approach for fabricating the 3 geometries considered in this study. The conclusions obtained are specific to this particular application and, once more, it is acknowledged that in order to reach a global understanding relative to this technology's environmental implications, extra research still needs to be made.