Product Design for Value Recovery in Support of Closing Material Loops

Liang Cong, Purdue University

Abstract

For decades, the notion of closing material loops via recycling and remanufacturing has been advocated as an approach to conserve precious material resources and achieve economic benefit. Visionaries such as Thomas E. Graedel and Braden Allenby are notable in this regard. Recently, policy makers have introduced the phrase “circular economy” as a more non-technical, publicly acceptable way of describing the philosophy of closing material loops within the product life cycle and avoiding life cycles that dispose product after use. Circular economy is being increasingly accepted as a promising and sustainable business model, supporting waste minimization through product life cycles as the best alternative to the traditional “take-make-dispose” linear production pattern. It requires the reuse of components and materials in multiple life cycles after products go through design, manufacture, and use. The product end-of use (EOU) stage is the key to circulating materials and components into a new life cycle rather than into direct disposal. The economic viability of recycling EOU products is greatly affected by designers’ decisions and largely determined during product design. The low economic return of EOU value recovery is a major barrier to overcome. Most literature focuses on technical support of the value recovery of EOU products, including designs for disassembly and EOU. These studies offer little assistance in terms of designing products for the circular business model. To address these problems, this thesis investigates the automatic generation of a product disassembly matrix and the determination of an optimal value recovery plan for independent recyclers, mitigating bottlenecks to value recovery from the design perspective and assisting design decisions for original equipment manufacturers to maximize product lifecycle profit. Currently, recovering the value of EOU products is carried out without rational planning, resulting in the loss of the recoverable value embedded in material and components. To address this problem, planning for dismantling and appropriate technologies should be employed to improve the economic performance of EOU products’ value recovery. First, a method for automatic generation of a transition matrix – a structure which incorporates all possible disassembly operations and associated subassemblies, is developed. A preservative disassembly transition matrix is a description of possible ways in which to disassemble a product into individual parts without any damage. Second, a guideline is created to include destructive and automated operations in order to expand preservative disassembly matrices into dismantling transition matrices because dismantling EOU products in such a way might produce more profit than using a purely preservative disassembly. Based on the dismantling transition matrix, binary integer programming is used to formulate EOU product value recovery while considering possible options for components/subassemblies as well as the transition cost between dismantling operations, tools costs, and recycling regulations or goals. The economic viability of recycling EOU products is greatly affected by designers’ decisions and largely determined during product design. A design method to facilitate EOU products’ value recovery is developed. The EOU scenario for products depicts what modules (groups of components) will be allocated for reuse, recycling, or disposal; the order of joint detachment (i.e., the joints for modular connections); and the EOU options for each module. Bottlenecks, improvement opportunities, and design suggestions can be identified and provided following the EOU scenario analysis. Pareto analysis is used for ranking joints, according to their detachment costs, and for indicating which joints are the most suitable for replacement. The analytic hierarchy process is also employed to choose the best joint candidate by using trade-offs among criteria from the perspective of disassembly. In addition, disposal and recycling modules are checked to eliminate hazardous material and increase material compatibility. A valued-based recycling indicator is developed to measure the recyclability of the modules and evaluate design suggestions for material selection. Lastly, based on heuristics, the most valuable and reusable modules will be selected for reconfiguration so that they can be accessed and disassembled easily. To help companies adopt a circular economy, this thesis develops a market-driven design approach with which to link design decisions with market responses for maximal economic returns. A mathematical model is developed, which considers both manufacturing/remanufacturing stages in life cycles and market demands for new and remanufactured products. It can guide designers in making optimal design decisions on features, including materials, fasteners, and configurations, in order to achieve maximal market profit. Optimization of these major features will overcome the difficulties in recyclability, reduce disassembly times, ensure the quality of recovered components, and can reduce the cost incurred during manufacture and assembly. The model also determines both manufacturing and remanufacturing strategies, such as pricing, quantities of new products and remanufactured products, and collection rates. The work is continuation of research on sustainable design to lay a foundation for computer aided design software to include product end-of-use phase, create dismantling guidelines for recyclers to optimize recovery plans and improve design features from material, joints and configuration for original equipment manufacturers in order to close material loops with maximal profits.

Degree

Ph.D.

Advisors

Zhao, Purdue University.

Subject Area

Mechanical engineering|Environmental engineering|Industrial engineering|Design|Sustainability|Materials science|Economics

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