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Sustainability is becoming a central pillar of manufacturing and Additive Manufacturing (AM) processes, thanks to their potentialities, seem to open a new path to reduce the environmental footprint. However, the surface finishing of AM parts is hardly ever adequate for high performances applications so post-process treatments are required. Thus, the assessment of sustainability should inevitably consider both steps. In this study, a Ti6Al4V cylindrical sample was firstly manufactured by Electron Beam Melting (EBM) and then machined by turning as post-treatment process. Surface roughness was measured either before and after the machining process both along the direction parallel and that perpendicular to the axis of the cylindrical sample and a Ra reduction of 84.14% and 95.74% were obtained, respectively. To evaluate the goodness of the machining process from the sustainability perspective, the Specific Energy Consumption (SEC) was calculated to evaluate the unit energy consumption for removal the mass unit. Moreover, power trends during the two turning passes have proved to be useful in understanding the different stages of the machining process, the cutting forces involved, and the amount of material removed.

Current scenarios show the need of making manufacturing more sustainable as it plays a crucial role in global sustainability. For this reason, sustainability should be included among the objectives driving the selection of process parameters. As-built parts manufactured by additive manufacturing techniques always require post-processing to meet industrial quality requirements, and machining is one of the solutions often adopted to improve their surface finishing. However, inevitably an additional manufacturing process requires some supplementary both energy and resource consumption by also impact unavoidably on the environment. This experimental study includes both additive manufacturing and post-process machining to evaluate the global specific energy consumption required to manufacture and then finish Inconel 718 parts. This paper aims at understanding how to obtain Inconel 718 parts manufactured by selective laser melting (SLM) and machined by turning by saving energy without sacrificing roughness and density. The printing process parameters of SLM process have been varied in a wide range: 27 different samples have been produced to evaluate the specific energy consumption (SEC) and to highlight the influence of the process parameters on the energy consumption. Density and roughness measurements have been chosen as measured outputs to prove the effectiveness of the process and to attempt a correlation among process parameters, properties of the printed parts and energy consumption. All the as-built samples were post-treated by turning process under the same conditions to achieve a surface finishing with a Ra value close to 4 μm; the energy consumption of this process has been also recorded and analyzed. Finally, the energy consumption of the whole processing path, including both printing and turning, has been discussed and a correlation between processing parameters and energy consumption has been attempted. Results showed that a proper choice of the process parameters leads up to a 54% reduction in specific energy consumption to obtain SLMelted Inconel 718 parts having low surface roughness and high density.

ABSTRACTThis paper provides a reliable state of the art of laser polishing process (LP), used to reduce surface roughness and to improve surface properties of additively manufactured metal parts. The motivation of this review and the introduction to the research topic are discussed in detail in the first part of the paper, then the fundamentals and the working principles of LP are exposed. A quantitative literature survey is also included, the main research streams are discussed, the most used laser sources and the most investigated materials are highlighted. The manuscript core is divided into five subchapters depending on the material to be polished: aluminium alloys, titanium alloys, steels, CoCr alloys and nickel alloys. Each of these discusses the laser adopted, the results obtained, the role of the process parameters and the physical phenomena ruling the process. The final section includes applications, advantages, direction of future work and main conclusions drawn.

This paper provides a reliable state of the art of laser polishing process (LP), used to reduce surface roughness and to improve surface properties of additively manufactured metal parts. The motivation of this review and the introduction to the research topic are discussed in detail in the first part of the paper, then the fundamentals and the working principles of LP are exposed. A quantitative literature survey is also included, the main research streams are discussed, the most used laser sources and the most investigated materials are highlighted. The manuscript core is divided into five subchapters depending on the material to be polished: aluminium alloys, titanium alloys, steels, CoCr alloys and nickel alloys. Each of these discusses the laser adopted, the results obtained, the role of the process parameters and the physical phenomena ruling the process. The final section includes applications, advantages, direction of future work and main conclusions drawn.