Han P. Bao

Issues in intelligent cell control for flexible manufacturing systems

Abstract The highly important issue of intelligent cell control is addressed. Two major hierarchical control structures (the Advanced Factory Management System AFMS and the Automated Manufacturing Research Facility AMRF) are described and a comparison is made between the two structures. The advantages and difficulties of both types of manufacturing cells are elucidated as well.

Integrated approach to design and manufacture of shoe lasts for orthopaedic use

Abstract For commercial shoes as well as custom-made shoes, the shoe last—a solid model of the inner volume of the shoe—is unquestionably the single most important component of the fabrication process. This paper introduces the elements of an integrated CAD/CAM system to digitize the foot, use a graphics sub-system to create the geometry of a last from the foot model, and generate the tool cutter paths for a numerical control machine to cut the last. Issues of integration of design data and manufacturing data, and problems related to the operation of the sytem are discussed in this paper.

Re-sequencing of Design Processes With Activity Stochastic Time and Cost: An Optimization-Simulation Approach

Background. By the mid-1990s, the importance of the early introduction of new products to both market share and profitability became fully understood. Thus, reducing product time-to-market became an essential requirement for continuous competition. Coupled with the fact that about 70% of the life cycle cost of a product is committed at early design phases, the motivation for developing and implementing more effective methodologies for managing the design process of new product development projects became very strong. Method of Approach. One tool that helps in understanding and analyzing such a project is the design structure matrix (DSM). This paper presents a framework that obtains an optimum sequence of project activities-presented by the DSM-that minimizes total time and cost given stochastic activity estimated time and cost. The framework interfaces a meta-heuristic optimization algorithm called simulated annealing with a commercial risk analysis software. Results. The proposed framework was applied to a design project and the results have shown a robust solution minimum was reached. Conclusions. Since much of the time and cost involved in the design process is attributable to its expensive iterative nature. The framework presented in this paper improves a design project via obtaining an optimum sequence of its activities that minimizes total time and cost.

Evaluation of product reusability based on a technical and economic model: a case study of televisions

In the field of sustainable manufacturing, reusing of old products or components is considered as the most environmentally friendly strategy among all other strategies. However, the decision of reusing old components of a used product confronts many uncertainties such as the quality level of the used components and the economic aspect of reusing them compared to producing a new component. This paper presents an integrated technical and economic model to evaluate the reusability of products or components. The model introduces some new parameters, such as product value and product gain, to assist the decision between reuse, remanufacture or disposal. In order to handle uncertainties, a Monte Carlo simulation using @Risk/sup /spl trade// is utilized. The results show that the model is capable to assess the potential reusability of used products, while the use of simulation significantly increases the function of the model in addressing uncertainties. A case study of televisions is used to demonstrate the applicability of the model using extensive time-to-failure data for the major parts of a television set. Furthermore, a direction of future work is outlined and briefly discussed.

Close-Loop Cost Equation for Objects Manufactured by Milling

One of the major drawbacks of present cost estimation models is their incapability of embracing effectively complete product development stage. Parametric estimation works well in early design stage, but when it comes to detail design stage, a more complete estimation is provided by process model based and detail estimation techniques. A major paradigm shift is proposed in this paper whereby Cost is to be considered as a design parameter from scientific perspective and it is to be treated as a design consequence rather than as an operational outcome. A comprehensive framework using System Analysis fundamentals is designed to study Process Cost aspects of a part or a design. The paper gives detailed implementation of this new approach for objects manufactured largely by milling operation. The paper also suggests a methodology to extend this approach to other manufacturing processes. The proposed Generic Cost Estimation Model shows good agreement with cost estimation by commercial estimation software when applied to the objects manufactured by milling process. It also promises integration of Cost with other disciplines in Multidisciplinary Optimization and Collaborative Engineering. The integration is achievable through new information technology interface tools.

Energy-Based Life Cycle Assessment of Industrial Products

Forty-seven industrial products with verifiable records of life cycle energy consumptions over their manufacturing phases and usage phases provide the basis for this study. The environmental impacts for determination include global warming potential, ozone depletion potential, photochemical oxidants, acidification potential, and eutrophication potential. Correlations between these environmental impacts and the life cycle energy consumptions are the primary outputs of this study. It was determined that the energy consumption was an excellent indicator for many if not most of the environmental loads indicated above.

Emission inventory assessment for a container vessel

This paper presents estimates of exhaust emissions from a container vessel during its voyages by using current best-practice inventory methodology. Emission estimates are performed for both criteria air pollutants and greenhouse gases. Two approaches, power-based and fuel-based, are applied for emission calculations, where the former involves multiplying power-based emission factors by engine power consumptions and the latter utilizes fuel based emission factors with fuel usage data. With the use of latest emission factors and real data on vessel activity profiles, our emission estimates provide better representation of the actual vessel emission performance. Moreover, good consistency between power-based estimates and fuel-based estimates proves reliability in emission inventory results.

On the machining of cylindrical objects with complex curvature

Abstract This paper describes an integrated approach to the design and manufacture of cylindrical type objects with complex curvature. The modules in this system include the scanning of the object, its surface description and subsequent modification, the tool path generation, and the NC machining of the object. The operation of each module is illustrated in a case study involving the design and manufacture of a shoe last for orthopedic footwear.

Development of Sustainable Indicators for Products and Processes

Sustainable development is only a lofty goal as long as there is a lack of standard metrics and benchmark values to measure the performance of sustainable development. Measurement of sustainability has been articulated by researchers in several ways, but most definitions are based on the so-called Triple Bottom Line (TBL) approach i.e., with Economic (Profit), Environment (Planet) and Social welfare (People) objectives. Individual measures were proposed by many researchers for these dimensions of sustainability using various indicators. The focus of this paper is on manufacturing processes and products, as opposed to services and organizational entities, it is meant to test the hypothesis that there is a concise subset to the wide range of indicators so far identified in the literature which could be applied to manufacturing processes and products. We wanted to address three issues: 1- What kinds of indicators can be used; 2- How often have they been used or, in other words, how relevant are they? and 3- Are there other indicators which may have been missing? Our primary approach was to look for real case studies in which the authors clearly intended their products to be officially declared as sustainable. All together we found 106 case studies which fit the purpose of our study in the Environmental Product Declaration (E.P.D., http://www.environdec.com). EPD is an organization which provides relevant, verified and comparable information to meet various customers and market needs. The categories of products in EPD range from food and beverage products to textile, wood, chemical, non-metallic mineral, basic metals, fabricated metal, machinery and equipment, and office machinery and computers. Each case study in EPD was carefully assessed with regards to the three issues indicated above, and the final result was the formation of a new set of indicators which will be more suitable for manufacturing processes and products. This new set of indicators, perhaps better described as a filtered set of indicators, was used in a case study to compare the sustainability of a Cathode Ray Tube (C.R.T.) and a Liquid Crystal Display (L.C.D.) desktop computer. Both of these products have been extensively documented by Sony Corporation and the EPA. They provided substantial quantitative data which enhance the validity of our own study. One other tangible result of our study was the determination of a “Sustainable Threshold“ for various products based on the 106 case studies indicated above. We wanted to submit the proposition that an aggregated score determined as indicated in our work can serve as a reliable measure for sustainability.Copyright

Vessel Power Prediction and Its Impact on Emission Inventory

Current practice of emission estimate for ocean-going vessels largely relies on the conventional propeller law for determining power consumption. This practice tends to underestimate the actual emission when sea states and winds are ignored. This paper presents an evaluation of two approaches on the prediction of power of a container vessel. The first approach estimates vessel power as a function of the vessel speed according to the propeller law. While the propeller law approach is cost-effective and time-saving in computing vessel propulsion power, it generally under-estimates vessel propulsion power due to the omission of many other influencing factors including vessel course, engine model, ocean states and weather conditions. The second approach derives vessel propulsion power as a function of the vessel speed and resistance forces. The propulsion power required for a particular vessel behavior is determined based on vessel towing resistance, added resistance from waves and winds, and a variety of propeller and hull dependent efficiencies. Because of the incorporation of external factors, this approach should be more accurate than the propeller law in reflecting the actual vessel power requirement. Comparative analysis is conducted among the two estimate results and real measurement data on engine power output. The results clearly show that power estimated from the propeller law underestimate the vessel propulsion power and the gap increases much faster for higher vessel speeds. Power estimate from the second approach provides more accurate results as they greatly match the measured power values. The ups and downs of the prediction results precisely reflect real power variation along with speed changes. Improved power prediction leads to more reliable emission inventory calculation. However, the improvement of accuracy should be balanced with the increased requirement on data sources and computing efforts.Copyright