Purpose: – The purpose of this study is to compare the environmental impacts of two additive manufacturing machines to a traditional computer numerical control (CNC) milling machine to determine which method is the most sustainable. Design/methodology/approach: – A life-cycle assessment (LCA) was performed, comparing a Haas VF0 CNC mill to two methods of additive manufacturing: a Dimension 1200BST FDM and an Objet Connex 350 “inkjet”/“polyjet”. The LCA’s functional unit was the manufacturing of two specific parts in acrylonitrile butadiene styrene (ABS) plastic or similar polymer, as required by the machines. The scope was cradle to grave, including embodied impacts, transportation, energy used during manufacturing, energy used while idling and in standby, material used in final parts, waste material generated, cutting fluid for CNC, and disposal. Several scenarios were considered, all scored using the ReCiPe Endpoint H and IMPACT 2002+ methodologies. Findings: – Results showed that the sustainability of additive manufacturing vs CNC machining depends primarily on the per cent utilization of each machine. Higher utilization both reduces idling energy use and amortizes the embodied impacts of each machine. For both three-dimensional (3D) printers, electricity use is always the dominant impact, but for CNC at maximum utilization, material waste became dominant, and cutting fluid was roughly on par with electricity use. At both high and low utilization, the fused deposition modeling (FDM) machine had the lowest ecological impacts per part. The inkjet machine sometimes performed better and sometimes worse than CNC, depending on idle time/energy and on process parameters. Research limitations/implications: – The study only compared additive manufacturing in plastic, and did not include other additive manufacturing technologies, such as selective laser sintering or stereolithography. It also does not include post-processing that might bring the surface finish of FDM parts up to the quality of inkjet or CNC parts. Practical implications: – Designers and engineers seeking to minimize the environmental impacts of their prototypes should share high-utilization machines, and are advised to use FDM machines over CNC mills or polyjet machines if they provide sufficient quality of surface finish. Originality/value: – This is the first paper quantitatively comparing the environmental impacts of additive manufacturing with traditional machining. It also provides a more comprehensive measurement of environmental impacts than most studies of either milling or additive manufacturing alone – it includes not merely CO₂ emissions or waste but also acidification, eutrophication, human toxicity, ecotoxicity and other impact categories. Designers, engineers and job shop managers may use the results to guide sourcing or purchasing decisions related to rapid prototyping.

Summary: This life cycle assessment measured environmental impacts of selective laser melting, to determine where most impacts arise: machine and supporting hardware; aluminum powder material used; or electricity used to print. Machine impacts and aluminum powder impacts were calculated by generating life cycle inventories of materials and processing; electricity use was measured by in‐line power meter; transport and disposal were also assessed. Impacts were calculated as energy use (megajoules; MJ), ReCiPe Europe Midpoint H, and ReCiPe Europe Endpoint H/A. Previous research has shown that the efficiency of additive manufacturing depends on machine operation patterns; thus, scenarios were demarcated through notation listing different configurations of machine utilization, system idling, and postbuild part removal. Results showed that electricity use during printing was the dominant impact per part for nearly all scenarios, both in MJ and ReCiPe Endpoint H/A. However, some low‐utilization scenarios caused printer embodied impacts to dominate these metrics, and some ReCiPe Midpoint H categories were always dominated by other sources. For printer operators, results indicate that maximizing capacity utilization can reduce impacts per part by a factor of 14 to 18, whereas avoiding electron discharge machining part removal can reduce impacts per part by 25% to 28%. For system designers, results indicate that reductions in energy consumption, both in the printer and auxiliary equipment, could significantly reduce the environmental burden of the process.

Sustainable design methods and tools abound, but their implementation in practice remains marginal. This article brings together results from previous literature reviews and analyses of sustainable design methods and tools, as well as input from design researchers and professional practitioners to identify the needs and gaps in the area. It results in a shared vision of how sustainable design methods and tools can be more tightly integrated into mainstream product design and development, as well as the current state of practice and research in relation to four central questions: What are the needs and values of industry regarding sustainable design? What improvements in sustainable design methods and tools would most drive industry forward? How should researchers move forward with developing more useful sustainable design methods and tools? How can sustainable design be more effectively integrated into industry? A roadmap for the international sustainable design research community is proposed with descriptions of short-, medium-, and long-term tasks for addressing each question. The purpose is to support collective progress and discussions on method and tool development and adoption, and to enable more tangible success in mainstreaming sustainable design practices in industry.

Metal additive manufacturing (AM) is revered for the design freedom it brings, but is it environmentally better or worse than conventional manufacturing? Since few direct comparisons are published, this study compared AM data from life-cycle assessment literature to conventional manufacturing data from the Granta EduPack database. The comparison included multiple printing technologies for steel, aluminum, and titanium. Results showed that metal AM had far higher CO2 footprints per kg of material processed than casting, extrusion, rolling, forging, and wire drawing, so it is usually a less sustainable choice than these. However, there were circumstances where it was a more sustainable choice, and there was significant overlap between these circumstances and aerospace industry use of metal AM. Notably, lightweight parts reducing embodied material impacts, and reducing use-phase impacts through fuel efficiency. Finally, one key finding was the irrelevance of comparing machining to AM per kg of material processed, since one is subtractive and the other is additive. Recommendations are given for future studies to use more relevant functional units to provide better comparisons.

The Circular Economy Action Plan adopted by the European Commission aims to keep value in products as long as possible through developing product-specific requirements for durability and repairability. In this context, various scoring systems have been developed for scoring product repairability. This study assessed the objectivity and completeness of six major repair scoring systems, to see what further development may be required to make them policy instruments for testing product repairability. Completeness of the scoring systems was assessed by comparing them to the latest literature on what design features and principles drive product repairability. Objectivity was determined by assessing whether the scoring levels in each criterion were clearly defined with a quantifiable and operator-independent testing method. Results showed that most of the criteria in the scoring systems were acceptably objective and complete. However, improvements are recommended: The health and safety criterion lacked objectivity and has not yet been fully addressed. Further research is required to expand the eDiM database, and to identify whether the additional accuracy provided by eDiM compared to disassembly step compensates for the increased difficulty in testing. Finally, assessment of reassembly and diagnosis should be expanded. Addressing these gaps will lead to the development of a scoring system that could be better used in policymaking, and for assessment by consumer organizations, market surveillance authorities, and other interested stakeholders, to promote the repairability of products.