Previous Research Projects

Design and Planning in Machining

With the expansion of pollution preventive initiatives in the government sector, development of certification mechanisms in the international marketplace, and increased consumer demand for "green" products, industry is under increasing pressure to minimize the environmental impact of products over their life cycles. Within a product's life cycle, one phase which has significant environmental impact is the production phase. The complexity and distributed nature of the knowledge and information necessary for product design and production decision-making necessitates a modular approach. The modules within this system are process models that predict key environmental impact
parameters - waste stream mass and phase, energy consumption, yield and process time - from product specification and process parameter inputs. The waste stream mass and phase then directly drive the health hazard impact of the manufacturing process. 

In an NSF-funded project , machining process models which have been developed or are under development as modules for such a framework include drilling, milling, and grinding. The outputs from these models, applied to the feature-by-feature manufacture of a component, can then be integrated to enable environmental design tradeoffs for the product as a whole. This concept is being implemented through a green machining incremental planner, which is being developed as an add-on to Pro/Engineer, a feature-based CAD tool. 

The process energy is derived directly from cutting force which is a function of the workpiece material, feedrates and cutting speeds, tool or abrasive geometry, and type of cutting fluid. The three main machining mass waste streams are used tools; workpiece material scrap - in the form of chips and rejected parts; and cutting fluid, which is coated on parts and chips and also emitted into the manufacturing facility's air as vapor or aerosol. To supplement the modeling effort, a hardware testbed is being constructed to study cutting fluid aerosol formation and cutting fluid degradation in grinding. 

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Exergy as an Environmental Indicator

One of the most challenging problems encountered when invoking Design for the Environment (DFE) strategies involves the selection of an environmentally optimal process configuration from among competing process designs.  This selection effort is made difficult by the complex relationship between the technology selected and the characteristics of the residual produced.  Process selections affect the flow rate, composition, and phase of all resulting effluent streams.  Evaluating alternative processes therefore often requires one to compare the relative environmental merits of distinctly different residual streams.  Existing systems for performing such analyses have focused primarily upon subjective scoring techniques.  There is nonetheless considerable agreement among researchers that a less-subjective metric capable of providing greater insight exists in the form of the thermodynamic concept of exergy (also often referred to as availability, available energy, or essergy).

Exergy is a thermodynamic concept that fuses energy and material quality information in a measure that is both descriptive and physically significant.  It is flexible enough to be used across the breadth of industrial application.  However, owing to its origins within the thermodynamic community, to date few researchers have investigated its potential within the framework of DFE.  Current CGDM efforts are focusing upon the practical application and adaptation of exergy analysis to the specific problems embodied by the material and energy flows through industry.  The emphasis of research has been upon developing a generalizable technique to efficiently calculate exergy in an industrial setting, exploring the significance of environmental ground states and how they might be utilized to leverage results, and establishing the requisite databases for performing a wide range of highly diverse analyses.

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Manufacturing Systems Modeling/Environmentally Conscious Manufacturing

In Environmentally Conscious Manufacturing (ECM) much of the recent
work has focused on product design considering environmental factors.
From a larger product stewardship view, improvements can be made to facility design, production planning and control, and organizational development activities. Graedel and Allenby refer to these activities as generic Design for Environment (generic DFE).  This is motivated by the emergence of the ISO 14001 environmental managment standard, which specifies that an environmental improvement and control process should be in place within an organization.  With the work in this area, we show how environmental factors can be included within manufacturing systems decision making to compliment the DFE activities associated with product design.

At the level of a manufacturing system or facility, decisions are normally made considering only the primary  mass flows: the final product and perhaps its subassemblies.  In ECM, we also consider secondary mass flows: catalysts, waste streams, energy usage, worn tools, and so forth.  To include environmental factors in facility assessement and decision support tools, these secondary flows must be considered along with traditional metrics such as manufacturing cost, throughput, efficiency, and quality.  Our work in this area looks at developing facility wide waste flow and hazard assessements based on process models, and the use of the information from these assessements to improve production planning and manufacturing system decision making. 

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Multi-Dimensional Hazard Scoring

In bringing the fields of design and manufacturing together with public health and toxicology, we are developing tools to mitigate the adverse health effects that often result from manufacturing a product. With focus on the product design and manufacturing process planning stages, as opposed to more historical end-of-pipe control measures, more innovative and efficient improvements can be made. A Multi-Criteria Hazard (MCH) evaluation technique has been developed as an important and effective tool. The MCH evaluation predicts a manufactured product or manufacturing processí hazard impact. The methodology compares different chemicals under several impact categories (currently: Carcinogenicity/Genotoxicity/Mutagenicity, Reproductive/Developmental Toxicity, Systemic Toxicity, Acute Toxicity, Physical Hazards, Standards/Regulations) and presents information about which manufacturing compounds or processes are less harmful and how they are less harmful.

Implementation of the MCH technique has been demonstrated through several applications: electronics material selection, machining process parameters, and systems-level applications. A fate and transport box model for a manufacturing facility has also been developed and integrated with the hazard evaluation to provide hazard information at a facility scale.

The MCH evaluation is an improvement over the previous health hazard scoring (HHS) system developed at UC Berkeley in that it calculates the impacts on a logarithmic scale, analyzes the hazards over several impact categories, and uses a more robust scale of data and dose ranges. Most of the current scoring systems used in industries and governments are structured to rank chemicals for prioritizing regulation or reduction efforts, and many of the DfE based tools use only one endpoint (i.e. mass, exergy, land area, reference dose for cancer) for analysis. However, the MCH evaluation has the ability to compare mixtures of chemicals along varying mass proportions, quantities, and endpoints.

Development of these types of tools enables planners and designers of different backgrounds to examine the impact of their decisions over the span of the problem space, from functional design to manufacturing process health impact. Whether the greatest impact can be reduced at the product feature, material selection, process planning, worker protection, or mitigation level can be better realized.

Related Papers

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