Hong-Chao Zhang - US grants

The past two decades have witnessed the development of many Computer Aided Process Planning Systems, each of which has specific advantages and disadvantages. Among these systems there exists considerable data overlap; yet the data cannot be interfaced, exchanged, integrated, or communicated because the data structures are not standardized. Only limited investigation has taken place with respect to the problems, and some aspects have been ignored altogether. The object of this project is to develop a test bed of integrated process planning systems, which can be used for testing flexibility and data standardization of a variety of process planning functions. The projects will be conducted in collaboration with the National Institute of Standards and Technology's process planning test bed laboratory.

This grant provides funding for the development of a theoretical scheme for automated tolerance control of discrete mechanical part setup planning in numerically controlled (NC) machining. The proposed tolerance control scheme is based on graph theory. The features of a part are represented by means of vertices while the parametric and geometrical tolerances assigned among the features are represented by edges. The entire design specifications of a part is represented by a hyper graph or tolerance graph. Hence, an optimal setup planning problem is transformed into a graph search problem. An optimization algorithm will be developed based on analysis of the minimum setup errors according to the respective setup methods. Characteristics of NC machining are incorporated within the tolerance graph. Finally, the proposed research will be implemented into a computer program and will be integrated with a computer aided design system. If successful, this research will yield two major contributions: (1) It will establish a theoretically sound foundation and scientifically rigorous base for tolerance control in process planning, and (2) It will develop a tolerance graphing technique that will eventually replace the limited tolerance charting technique. With the help of a tolerance graph, planning related tolerance control problems can be solved effectively. As a result, precision parts could be produced at reduced cost. The proposed tolerance control algorithm would provide a practical approach for process design and analyzing currently existing process plans. Specifically, by using a tolerance graph, one can (1) select appropriate setups, locating datums, and operation sequences to minimize tolerance stackup, (2) calculate operational dimensions and tolerances for machining cuts, and (3) simultaneously deal with tolerances along all axes. As an additional benefit, this research adopts a science-based approach to solving tolerance control problems. Science-based approaches are much more easily computerized to facilitate the realization of computerized tolerancing.

The objectives of this Product Realization and Environmental Manufacturing Innovative Systems (PREMISE) Exploratory Research project are: (1) To conduct exploratory research into the feasibility of an alternative PCB recycling process based on cryogenic decomposition of the PCBs; (2) To establish an interdisciplinary research team that can develop a long-term collaboration that builds on the understanding developed in this project; (3) To evaluate the proposed recycling process against traditional PCB recycling processes in terms of recycle rate economics, energy consumption, and environmental performance; and (4) To examine the feasibility of reusing plastics in the proposed recycling process.

The proposed recycling process is cryogenic decomposition of the PCBs. The process takes advantage of the fact that at very low temperatures, polymeric materials become highly brittle. In addition, the residual stresses set-up in the PCB resins due to thermal expansion mismatch between the polymers and other materials on the PCB is expected to lead to a better separation than might otherwise be possible simply due to the embrittlement of the plastics. Actual laboratory experiments will be performed using a cryogenic test system.

Wide diffusion of electronic equipment and shortening of product lifecycles have caused a serious problem: how to deal with large quantities of end-of-life or obsolete electronic equipment. While there are various technical challenges for electronic product recovery and recycling, this research focuses on printed circuit boards (PCBs) or printed wiring boards (PWBs). PCBs are primary components in many electronic products built for both military and commercial applications. Due to their complex construction and the consequent complicated mixture of materials, PCB recycling presents a serious challenge to today's industry. The rich content of precious metals provides a strong economic justification for materials recovery and recycling. On the other hand, large amounts of toxic components and fiber-reinforced polymers create difficulties for recycling and adverse environmental impact.

This Grant Opportunity for Academic Liaison with Industry award provides funding for a collaborative research that is targeted to modeling and optimizing the reverse logistics channel of end-of-life electronic products to improve its responsiveness to the market demands from both ends of the channel. The objectives of this research are three fold: i) establish a long term university-industry collaboration team in research of end-of-life management, ii) integrate market demand and customer return service requirement into logistics and reverse production scheduling to improve the responsiveness, and iii) investigate the integration and coordination issues in the whole reverse logistics channel among participants to optimize the performance at the system level. The following methodologies will be developed in this university-industry collaborative research to achieve the initial objectives: 1) Use random-sized batch arrival priority queuing system to model the logistics channel in regard to dynamic market demands and stochastic service requirements; and 2) Model the product return process and stochastic reverse inventory to optimize the reverse inventory policy.

The market of the reverse logistics is estimated at 55,000 millions in US in 2004. The results of this research in this regard will produce marked benefit to the industry through providing optimized decisions support with improved efficiency of business operations. While the findings of the research will bridge the gap between the current knowledge and the new requirements of the reverse manufacturing industry through integration of market demand into decision process and negotiation based coordination, the methodology developed can also be applied to other scenarios where responsiveness and coordination is required. The roadmap in this project will also guarantee the maximization of the potential benefit to education and the society.

0962533
Dai

This exploratory project proposes to establish the fundamental basis for developing a supercritical fluid (SCF) process for recycling printed circuit boards. First, the delamination/degradation mechanism of the bonding materials in printed circuit boards under supercritical fluid process conditions will be systematically investigated. The hypothesis is that these results will provide a basis for creating a supercritical fluid process to recycle printed circuit boards at low temperatures and pressures. If this hypothesis is proven out, there will be potential to transform the handling of discarded printed circuit boards, enabling the recycle of their make-up. The project offers a breakthrough opportunity for the recycling of printed circuit boards. The proposed SCF process potentially has important advantages compared to traditional metallurgical technologies and is anticipated to be environmentally benign as well as cost and energy saving. Additionally, classroom teaching will be enhanced by incorporating practical applications of SCF from the project. Collaborations with industrial partners are planned.

1133984 (Zhang). Widespread use of electronic equipment and shortening of product life cycles have created the challenging task of dealing with the ever-increasing quantity of obsolete electronic equipment. The huge amount of electronic waste (E-waste) generated each year and the lack of established methodologies capable of handling the increasing volumes of E-waste pose a severe environmental threat. Among the challenges to successful electronic equipment recycling, printed circuit board (PCB, primary components in every type of electronic product) recycling is recognized as one of the most difficult problems because of the complex construction and complicated materials composition of PCBs. The current PCB recycling industry uses traditional metallurgical technologies in which the fiber reinforced polymer matrix materials are incinerated. Although great effort has been made in the traditional metallurgical technologies for increasing the recycling efficiency for the end-of-life electronic products, the PCB recycling industry still faces the problems of poor environmental performance and limited economic returns. Recently, under an EAGER grant, the PIs of this award demonstrated proof-of-concept preliminary work for developing a novel supercritical fluid (SCF) CO2-based PCB recycling process at relatively low/medium temperatures and pressures. The exploratory experiments demonstrated that PCBs are delaminated with metals and glass fiber maintain their original form, making it possible to increase recovery rates not only for precious metals but also for non-metal materials. Such a process opens a new dimension for recycling of PCB and provides the possibility of satisfying economical and environmental demands. In the current project, the research team will systematically investigate the delamination mechanism of the bonding materials in PCBs under supercritical fluid processes and seek to understand structure/process relationships. Although literature documents the application of supercritical fluids in polymer synthesis and processing, there is limited existing work on revealing the performance of polymeric materials in supercritical fluids. In addition, the research team will optimize the SCF process by implementing process conditions based on the mechanism study and systematically evaluate process performance. Finally, the team will model and validate the recycling process for scale-up in terms of cost, energy, and environmental impact. The team will collaborate with industrial collaborators to promote transferring fundamental research to practical application. In addition, research and education will be integrated throughout the entire project duration.