FEATURE
"Green" Manufacturing One Part at a Time HARVEY BLACK
New process analysis tools bring "design for the environment" to the plant floor.
esign for the environment is a growing movement within industry that encourages manufacturers to consider the environmental and health impacts of products on the drawing board. The ecological ramifications of everything from mining a metal needed in a product to the eventual disposal of that product in a landfill are considered during the design phase. Bringing that concept down to the level of day-to-day operations on the plant floor—to deciding, for example, the environmental impacts of machining an engine block—is the goal of process models being developed by Paul Sheng and colleagues at the Consortium on Green Design and Manufacturing at the University of California at Berkeley {1-3). The models show mechanical designers and manufacturing engineers in real time how their design choices affect the type and quantity of waste generated. The models can also assess potential health hazards to workers that result from particular design decisions. Ford Motor Company, in Detroit, and Hughes Missile Systems, in Tucson, Ariz., have sponsored demonstrations of the models at their facilities. "The difficulty with design for the environment is that it can get fuzzy because it involves so many steps," said Sheng—including high-level manufacturing decisions such as choosing specific materials for a job. "We're trying to bring it down a notch or two to what's happening on the factory floor combined with what's happening in design studios." "Our ability to track [environmental decisions] through from the initiation of the material process all the way through to disposal or recycling is virtually nonexistent," said Brad Allenby, director of Energy and Environmental systems at Lawrence Livermore National Laboratory in California, who is regarded as the leader in the industrial ecology movement.
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Drilling a single hole Sheng's models focus on metal part machining because of its importance in a number of industries. "At the single-feature or singlehole level, the difference [in a design] is seemingly relatively minor," Sheng said, but extrapolating a little problem to hundreds of features in a part and to the many parts manufactured can make a significant difference. The equations that drive his models show 9 0 A • VOL. 31, NO. 2, 1997 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS
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the relationship among a wide array of inputs such as operating parameters and production materials, and outputs such as energy, production rate, waste products, and health effects. The model is a compilation of modules that analyze the mechanics of the process, including heat generation, tool wear, cuttingfluid coating, and aerosol formation. Traditionally, process models in manufacturing have considered quality and total production of goods, energy use, and the geometry of the shapes to be formed. But they have not looked at secondary outcomes such as the degradation of the fluids used to reduce friction in metal cutting, the generation of metal waste, and the release of particulates into the work environment, said Sheng. Something as seemingly harmless as grinding a part to make it smooth can generate millions of tiny particles that threaten workers' lungs. Yet designers typically do not heed such issues when they ask for a part to have a specific smoothness. "They don't really think of the processes it takes. A lot of time these surfaces are specified due to habit," Sheng said. When designers and engineers are shown the impact of specifying a certain surface, said Sheng, they may start asking whether the specified finish really makes a difference in the way a component functions.
Real-time feedback In modern manufacturing, the geographic separation of the designer and the manufacturing plant means that feedback loops from the production line to the designer have to be better. Sheng envisions a scenario on a working production line in which the manufacturing process model would catch a manufacturing decision that would yield an unacceptable level of waste or a material hazardous to h u m a n health, for instance. The report of a violation of an environmental guideline would travel at once to the designer who could quickly make the necessary adjustments. "One part of design for the environment has to involve doing a feedback to the designer," said Sheng, who points out that decisions have to be made quickly when engine blocks or other big components are being produced at a rate of two per minute. Sheng has been working on this model since 1994 and has demonstrated it twice at Ford and once at Hughes. In 1996, the model was demonstrated at Ford along with green design tools developed by the Machine Tool Agile Manufacturing Research Institute. The institute, headed by the University of Illinois, has a project aimed at "environmentally conscious machining," which includes Sheng's effort. At this demonstration, Sheng displayed the model's health hazard scoring system, a multicriteria assessment of health risks that takes into account carcinogenicity, flammability oral and inhaled toxicity dermal and eye irritation and reactivity of the components and processes used in specific manufacturing scenarios Mia Costic, a research engineer at Ford Motor Company in Dearborn, says of Sheng's model: "It switches addressing environmental concerns from after the fact to up front in the design process." At the Hughes demonstration, the intent was to explain how the model works. "It was half a demonstration and half training to show [the engineers] what are the potential waste streams," Sheng says.
The environmental impact of machining individual metal parts can be reported in real time by designers and engineers using software being developed by the Consortium on Green Design and Manufacturing at the University of California, Berkeley. (Courtesy of CGDM.)
Sheng's work is "one of those things that has been lacking throughout industry," says William Ward, who's in charge of Hughes' design for the environment effort. Among the tasks ahead is to make the model user friendly. "If it's going to be something that engineers are going to use day in and day out, we have to make it seamlessly merge with existing computeraided design tools," Sheng believes. To make the models accessible and user friendly, the Berkeley researchers made them available via the Internet in 1996 (4). "We can run models remotely through the Internet. A company can send its calculations on waste data to Berkeley, and we can do the calculations using our models here and then tell the company in seconds how to change course." Sheng, who has been supported by the National Science Foundation, the U.S. Air Force Office of Scientific Research, and Ford and other companies, said that to make the model commercial, he will have to include more regulatory and cost data. Ideally, the model also would include more waste data so that it could be calibrated. An important feature of a tool like the one Sheng has created is that "it brings environment out of overhead and makes it strategic to the firm," said Allenby. "What you're doing is saying that environment no longer is in [only] the Environment & Safety shop. Environment goes into business planning and product design."
References (1) Srinivasan, M.; Wu, X; Sheng, E Transactions of the North American Manufacturing Research Institute 1995, 23, 115— 30. (2) Sheng, P.; Srinivasan, M. Annals of the International Congress on Production nesearch 1995, 44(1), 433-37. (3) Sheng, P.; Srinivasan, M. Annals of the International Congress on Production nesearch 1996, 45(1), 455-60. (4) Consortium on Green Design and Manufacturing, http: / /www.me.berkeley.edu/green. Harvey Black is a freelance writer based in Madison, Wisconsin. VOL. 31, NO. 2, 1997/ENVIRONMENTAL SCIENCE S TECHNOLOGY / NEWS " 9 1 A
