Purpose -The purpose of this paper is to evaluate the energy consumed to fabricate nylon parts using selective laser sintering (SLS) and to compare it with the energy consumed for injection molding (IM) the same parts. Design/methodology/approach -Estimates of energy consumption include the energy consumed for nylon material refinement, adjusted for SLS and IM process yields. Estimates also include the energy consumed by the SLS and IM equipment for part fabrication and the energy consumed to machine the injection mold and refine the metal feedstock required to fabricate it. A representative part is used to size the injection mold and to quantify throughput for the SLS machine per build. Findings -Although SLS uses significantly more energy than IM during part fabrication, this energy consumption is partially offset by the energy consumption associated with production of the injection mold. As a result, the energy consumed per part for IM decreases with the number of parts fabricated while the energy consumed per part for SLS remains relatively constant as long as builds are packed efficiently. The crossover production volume, at which IM and SLS consume equivalent amounts of energy per part, ranges from 50 to 300 representative parts, depending on the choice of mold plate material.Research limitations/implications -The research is limited to material refinement and part fabrication and does not consider other aspects of the life cycle, such as waste disposal, distributed 2 manufacturing, transportation, recycling or use. Also, the crossover volumes are specific to the representative part and are expected to vary with part geometry. Originality/value -The results of this comparative study of SLS and IM energy consumption indicate that manufacturers can save energy using SLS for parts with small production volumes. The comparatively large amounts of nylon material waste and energy consumption during fabrication make it inefficient, from an energy perspective, to use SLS for higher production volumes. The crossover production volume depends on the geometry of the part and the choice of material for the mold.
Public policy is becoming increasingly stringent with respect to the environmental impacts of modern products. To respond to this tightened scrutiny, product designers must innovate to lower the environmental footprints of their concepts. Design for Environment (DfE) is a field of product design methodology that includes tools, methods and principles to help designers reduce environmental impact. The most powerful and well-known tool within DfE is Life-Cycle Analysis (LCA); however, LCA requires a fully specified design and thus is a retrospective design tool, only applicable as the end of the design process. Because the decisions with the greatest environmental impact are made during earlier design stages, it is important to develop concurrent design tools that can implement DfE principles at conceptual and embodiment design stages, thereby achieving more substantial environmental improvements. The goal of this work is to compile a set of DfE principles that are useful during the design process; explain select principles through examples; and provide an example of applying DfE principles concurrently during the design process.
Policymakers, consumers, and industry leaders are increasingly concerned about the environmental impacts of modern products. In response, product designers seek simple and effective methods for lowering the environmental footprints of their concepts. Design for environment (DfE) is a field of product design methodology that includes tools, methods, and principles to help designers reduce environmental impact. The most powerful and well-known tool for DfE is life cycle assessment (LCA). LCA requires a fully specified design, however, which makes it applicable primarily at the end of the design process. Because the decisions with the greatest environmental impact are made during early design stages when data for a comprehensive LCA are not yet available, it is important to develop DfE tools that can be implemented in the early conceptual and embodiment design stages. Based on a broad critical review of DfE literature and best practices, a set of 76 DfE guidelines are compiled and reconciled for use in early stage design of products with minimal environmental impact. Select guidelines are illustrated through examples, and several strategies for using the guidelines are introduced.
The reduced environmental footprint of bicycle sharing systems (BSS) is one of the reasons for their rapid growth in popularity. BSS have evolved technologically, transitioning from smart dock systems to smart bicycle systems, and it is not clear if the increased use of electronics in BSS results in a net environmental benefit. This article provides an evaluation of the impact of incorporating additional technology into BSS and uses that analysis as guidance for future BSS development. By comparing the impacts of a private bicycle, a smart dock BSS, and smart bike BSS using a life cycle assessment (LCA), this work reveals breakeven points and tradeoffs between the technologies. This study is also the first published empirical LCA of a smart bike known to the authors. In the production phase, smart bikes generate approximately three times the amount of greenhouse gas (GHG) emissions compared to the smart dock bikes per kilometer ridden over the lifetime, and when considering the endpoint categories of human health, ecosystem, and resources, smart bikes have approximately 2.7 times the environmental impact. The results suggest that shifting from smart dock to smart bike requires an increase in ridership by a factor of 1.8 to overcome the increased environmental impact based on the GHG emissions. We find that smart docks become preferable at a population density between 1,030 residents/km2 (in a bike friendly city) and 3,100 residents/km2 (in a city that is less likely to bike).
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