Towards criteria for sustainable process selection: On the modelling of pure subtractive versus additive/subtractive integrated manufacturing approaches

Additive Manufacturing (AM) processes can be counted among the disruptive technologies that are capable of transforming conventional manufacturing routes. The ability to create complex geometries, the reduction in material scraps during manufacturing, and the light-weighting due to the think-additive redesign of the components represent the main points of strength of AM. However, for some applications (such as the production of metal components for the automotive and aerospace industries), the surface finishing and dimensional/geometrical part tolerancing that can be achieved via AM processes might not be adequate to satisfy the imposed product specifications, and finish machining operations are often required. A machining approach and an integrated production route, based on an additive manufacturing process plus finish machining, have been compared in this paper. The primary energy demand and the CO2 emissions have been modelled for all the life cycle stages within a sustainable development context. The main result of the research work is a criterion for the selection of the most environmentally friendly manufacturing approach, while varying the productive scenario (i.e., the masses of the process scraps, the machined chips, and the support structures). The application of such a tool to the production of metal components made of either Ti-6Al-4V or stainless steel is discussed.