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.

This experimental study investigates the effects of process parameters for 3D printing polylactic acid (PLA) samples on both the mechanical properties obtained and the energy consumption in the fused deposition modelling (FDM) process. The explained experimental activities provide an in-depth evaluation of all the strategies adopted in different temperatures and scan speed strategies. The results, extracted in tensile strength, ultrasonic inspection (UT), and specific energy consumption (SEC), highlight the printing parameters that mainly affect the mechanical characteristics of the final workpieces and the energy consumption to find an appropriate energy-saving energy strategy for the PLA additive manufacturing process. The results indicate a more excellent uniformity of the molded material, reducing the printing time and total energy consumption at high speeds (V = 110 mm/s) and one level of temperature (T = 215 °C). A new efficiency index has been introduced to release guidelines to pursue the best setup compromise.

The assessment of energy consumed in manufacturing operations and the enhancement of their sustainability plays a fundamental role in the present research contest. Electron beam melting (EBM) is an additive manufacturing technique that allows the fabrication of titanium parts with high productivity and a low buy-to-fly ratio; on the other hand, the roughness of the parts is not adequate for high-performance applications, so a finishing step is always required. Aiming to reduce the energy used to produce a part, all the required manufacturing steps should by carefully treated in an integrated framework. The aim of this paper is to study the energy required to produce a Ti6Al4V part printed through EBM and the machined to achieve the desired surface finishing. Cylindrical specimens have been printed through an Arcam machine by using the processing conditions suggested by the manufacturer; then, the specimens have been turned under different processing conditions. The energy required in all the phases has been recorded and then carefully analyzed to point out the processing conditions which allows a more efficient use of resources. The results showed that the printing phase is by far the most energy demanding so should be carefully treated to reduce the printing time even if a greater roughness is achieved; the analysis of the machining stage suggested that both depth of cut and spindle speed must be kept the higher as possible to reduce the energy consumption of this stage.

Currently, sustainability plays a central role in the response to global challenges, strongly influencing decisions in various sectors. From this perspective, global efforts to explore inventive and eco-friendly solutions to address the demands of industrialization and large-scale production are being made. Bio-based composites needed for lightweight applications benefit from the integration of natural fibers, due to their lower specific weight compared to synthetic fibers, contributing to the overall reduction in the weight of such structures without compromising the mechanical performance. Nevertheless, challenges arise when using natural fibers in composite laminates and hybridization seems to be a solution. However, there is still a lack of knowledge in the literature regarding the strategies and possibilities for reducing laminate thickness, without sacrificing the mechanical performance. This work aims to fill this knowledge gap by investigating the possibility of reducing the laminate thickness in hybrid flax/basalt composites made of plies, organized in the same stacking sequence, through only varying their number. Tensile, Charpy, flexural, and drop-weight tests were carried out for the mechanical characterization of the composites. The results obtained confirm the feasibility of achieving thinner hybrid composites, thus contributing to sustainability, while still having acceptable mechanical properties for structural applications.

The use of lightweight components in automobiles started a new chapter in the automotive sector due to the renewable energy and sustainability increasing the overall efficiency of vehicles. As vehicle weight is directly linked to energy consumption, reducing mass through advanced materials can significantly decrease energy usage and emissions over the vehicle’s lifetime. This present study aims to conduct a preliminary life cycle assessment (LCA) of a prototype battery pack manufactured using pultruded composite materials with a volume fraction of 50% glass fibers and a volume fraction of 50% nylon 6 (PA6) matrix by quantifying the CO₂ emissions and cumulative energy demand (CED) associated with each stage of the battery pack’s life cycle, encompassing production, usage, and end-of-life recycling. The results of the EuCia Eco Impact Calculator and from the literature reveal that the raw materials extraction and use phases are the most energy-intensive and contribute mainly to the environmental footprint of the battery pack. For a single battery pack for EV, the CED is 13,629.9 MJ, and the CO₂ eq emissions during production are 1323.9 kg. These results highlight the need for innovations in material sourcing and design strategies to mitigate these impacts. Moreover, the variations in recycling methods were assessed using a sensitivity analysis to understand how they affect the overall environmental impact of the system. Specifically, shifting from mechanical recycling to pyrolysis results in an increase of 4% to 19% of the total CO₂ emissions (kg CO₂). Future goals include building a laboratory-scale model based on the prototype described in this paper to compare the environmental impacts considering equal mechanical properties with alternatives currently used in the automotive industry, such as aluminum and steel alloys.

Additive manufacturing (AM) is claimed to be a green technology because of its potential in improving material use efficiency. Electron beam melting (EBM) is among the most popular AM techniques adopted to manufacture titanium parts for medical and aerospace applications, as the technology offers an effective way of producing lightweight and complex parts. Nevertheless, additively manufactured parts hardly ever meet industrial quality standards, so post-treatments are always required resulting in additional resources and energy consumption. Moreover, still few works exist on joint analysis of energy consumption and roughness in milling EBMed parts by means of a non-typical tool, and this study aims to fill this gap of knowledge. Three EBM Ti6Al4V cylindrical samples were manufactured into a single job of the ARCAM A2X machine in the same process conditions. Three lengths, 120° apart from each other, were defined along the direction parallel to the axis of each cylinder to perform the milling by varying spindle speed, depth of cut, and machining speed. A high-performance complex-shaped insert has been used to perform the milling process to improve the surface finishing of the Ti6Al4V EBMed samples. Total energy consumption has been calculated as the sum of the machining time and the non-machining time. A joint investigation of both the surface roughness and the energy consumption in machining led to understanding which the best cut strategies are to perform milling with a complex cutting tool from a sustainability perspective. Results showed that it is not sustainable to choose the minimum depth of cut to obtain a fixed total depth of material removed as non-machining time showed to play a crucial role in the total energy consumption of the milling process.