Trade-off Modeling for Product and Manufacturing Process Design for the Environment

This article presents a method for integrating pollution prevention and concurrent engineering (simultaneous design of products and the manufacturing processes used to produce them). The central issue is unavoidable trade-offs, such as those among pollution, manufacturing cost, and quality. The probabilistic nature of the manufacturing process is exploited as an opportunity for pollution prevention. A decision tool in the form of a mathematical model is presented, which can be used by engineers and others with whom these trade-offs must be negotiated. Specifically, the method integrates statistical manufacturing process control into a multiobjective design optimization formulation. First, the framework of a multiattribute utility function is developed to determine which objectives are both relevant and negotiable.Then, a statistical manufacturing process control experiment is conducted to formulate some of the constraints that prevent all objectives from being maximized. Simultaneously, information obtained from the experiment is also used to fine-tune the upper and lower bounds in the utility functions.The results of an industrial case study of a floor tile manufacturer are presented, from the manufacturer's viewpoint. The material choice and manufacturing process settings that result in the best combination of the conflicting objectives of product quality (measured in terms of scrap rate), air pollution, and manufacturing cost are determined. The analysis also reveals the irony that for this manufacturer; efforts to reduce solid waste through greater use of scrap materials increase air pollution levels.