A comparative LCA method for environmentally friendly manufacturing: Additive manufacturing versus Machining case

Abstract

Additive Manufacturing (AM) technologies revolutionized the common understanding of manufacturing with their layer-by-layer building principle. However, the literature has documented their high energy requirements, which is not in-line with the current policies of energy and emission reduction. This ambivalence of AM opens the question for the research community about the wise choice of the manufacturing process to be adopted. This paper proposes a comparative LCA method to select the best manufacturing technology between Conventional Manufacturing (CM) and EBM plus Finish Machining (EBM+FM). The Life Cycle Assessment (LCA) is conducted under cradle-to-gate boundaries. Three metrics, namely the Cumulative Energy Demand (CED), cost and CO2 emissions are considered. Characterization of unit processes is done by using the recent findings in the literature which are included in the model for both process technologies. The Specific Energy Consumption (SEC) is connected to the Material Removal Rate (MRR) and to the average Deposition Rate (DRa), respectively for machining and EBM. The main finding of this research is the description of breakeven surfaces, which separate the regions of validity between machining and EBM, as function of the Solid-to-Cavity Ratio (SCR) and the DRa. Moreover, the presented methodology gives the possibility to compare the goodness of the different sets of design rules that can be chosen for EBM, thanks to the proper evaluation of the SEC parameter. Finally, a sensitivity analysis is conducted to assess the effect of the remaining key variables.