Jeffrey B. Dahmus

An Environmental Analysis of Machining

This paper presents a system-level environmental analysis of machining. The analysis presented here considers not only the environmental impact of the material removal process itself, but also the impact of associated processes such as material preparation and cutting fluid preparation. This larger system view results in a more complete assessment of machining. Energy analyses show that the energy requirements of actual material removal can be quite small when compared to the total energy associated with machine tool operation. Also, depending on the energy intensity of the materials being machined, the energy of material production can, in some cases, far exceed the energy required for machine tool operation.Copyright

Modular product architecture

Abstract This paper presents an approach to architecting a product family that shares inter-changeable modules. Rather than a fixed product platform upon which derivative products are created through substitution of add-on modules, the approach here permits the platform itself to be one of several possible options. We first develop function structures for each product. After comparing function structures for common and unique functions, rules are applied to determine possible modules. This process defines possible architectures. Each architecture is represented using a matrix of functions versus products, with shared/unique function levels indicated. This provides a systematic approach to generating architectures.

How Much Sorting is Enough Identifying Economic and Scrap‐Reuse Benefits of Sorting Technologies

One strategy for mitigating the effects of rapidly growing global materials consumption is intensified recycling. A key barrier to recycling is the ability to segment or sort constituents within end‐of‐life products. Various sorting technologies hold promise, but each must demonstrate added value to achieve wide‐scale deployment. Potential factors affecting such value include the mix of scrap supply, the nature and mix of finished goods demand, sorting technology performance, and costs. This article examines the use of optimization models to identify economically efficient sorting strategies and their impact on scrap usage. Using this method, this article attempts to identify the conditions that amplify and mute the value of sorting to facilitate recycling. When this method is applied to a case representative of European aluminum secondary production, it is clear that sorting methods can add value in a broad range of conditions. Although better sorting performance (in the form of segmentation efficiency, referred to as recovery rate) correlates positively with cost savings and scrap utilization, it does not always vary monotonically with optimal sorter utilization (i.e., the fraction of scrap sorted rather than unsorted). Furthermore, the case analysis indicates that the value of sorting is more strongly dependent on recovery rate for the more heterogeneous fraction, which, in the case of aluminum, is the cast‐like fraction. Ultimately, sorting increases production flexibility, making a recycler more economically resilient in the face of changing supply and production conditions.

Modeling the economic and environmental performance of recycling systems

A general model for evaluating the economic and environmental performance of electronics recycling systems is developed. This model comprehends the three main functions in a recycling system - collection, processing, and system management - and aims to enable quantification of the impact of context and system architecture on the performance of electronics recycling systems. Different modeling techniques are used, including process-based cost models, to evaluate economic performance, and life cycle assessment tools, to evaluate environmental performance. A case study, based loosely on Maine, is presented to show the utility of such a model in evaluating electronics recycling systems.

Material Recycling at Product End-of-Life

This work focuses on developing a compact representation of the material recycling potential for products at end-of-life. This representation is based on two measures: the value of the materials used in a product and the mixture of materials used in a product. These measures are similar to those used in constructing the Sherwood plot, which relates metal prices to the concentration of metals in a given ore grade. While the Sherwood plot provides insight into the relative attractiveness of mining different ores, the work here provides insight into the relative attractiveness of recycling different products. This information can in turn be used to help guide both product design and recycling policy

Modeling the impact of product portfolio on the economic and environmental performance of recycling systems

Through the development of a general model of electronics recycling systems, the effect of product portfolio choices on economic and environmental system performance is explored. The general model encompasses the three main functions of a recycling system - collection, processing, and system management - and allows for the effect of both contextual and architectural inputs - including product scope - to be explored. Overall model results indicate that collecting a broader portfolio of products can be economically favorable, even for cases in which lower-value products are added to a recycling system. In these cases, the higher total mass throughputs that are realized by the collection of additional product types can help to drive down the cost per unit mass collected. Expanding product scope can also yield improvements in environmental performance, as the energy per unit mass collected can also decrease with higher mass throughputs.