This paper presents a risk assessment strategy for managing the design process. The proposed method intends to provide the foundation for an intelligent system that can assist design engineers and managers of the design process. The IDEF3 methodology is used to describe the concurrent design process. The logical semantics of IDEF3 provide a much more detailed description than traditional project management methods, such as CPM. The IDEF3 model is then used to identify alternative scenarios that result in the successful completion of a design project. Using estimates of the likelihood that a scenario will fail to produce a successful design and the consequences that result, alternative scenarios are evaluated. A working example is provided, and the architecture of an intelligent system for risk assessment is discussed.
The IDEF methodology has been developed as a comprehensive language for modeling and analysis of manufacturing systems. IDEF0 functional analysis and IDEF3 process description are frequently discussed in the literature. However, most published work presents the basic concepts, industrial applications, and critiques of the methodology. One drawback often cited is that, beyond preliminary ad hoc analysis, IDEF models are seldom used. Furthermore, the lack of quantitative information in IDEF models prevents more detailed and interesting analysis. This paper adapts traditional system reliability methods to IDEF3 modeling. The logical relationships between activities in IDEF3 are used to quantify the overall reliability of the system and identify high-risk paths of decisions in the process. The concepts of path sets and cut sets are then used to identify critical activities and decision points. The analysis is illustrated with an industrial case study.
The broad interest in concurrent engineering has inspired research in the area of decomposition in mechanical design. Much of the research reported in the literature falls into one of three categories: (1) product decomposition, (2) problem decomposition, or (3) process decomposition. This paper provides a detailed discussion of the typology of decomposition in mechanical design. Related work is described and examples are provided to illustrate the need for decomposition of products, problems, and processes in design. Representation techniques and methodologies for decomposition are outlined. Finally, future research issues in decomposition in mechanical design are identified.
This paper presents a model for allocating storage space to inventory in a way that minimizes the cost of material handling. The space allocation problem is modeled as a generalized transportation problem; however, transporting material within the facility is the focus. The basic formulation of the model considers material type, material flow transitions, and distance transported. The model is extended to determine production levels for multiple products such that additional material handling costs (i.e., load/unload times) are minimized. Applications of the JIT concept and material handling in the job shop environment are discussed. Finally, an industrial case study is presented.
The development of IDEF tools for modeling and analysis of processes has been motivated by the desire to increase productivity by improving communication and structure of manufacturing systems. Constructing an IDEF model is only one component of a comprehensive process modeling effort. Representing IDEF models as process graphs, performing observational model analysis, and analysis of IDEF model structure are issues addressed in this paper. The paper includes a review of current approaches to IDEF modeling in industry, as well as techniques for analysis of IDEF models. The fundamentals of IDEF0 and IDEF3 are discussed, however, the emphasis of the paper is on model analysis and reengineering design and manufacturing processes. An algorithm for process model analysis is presented.
This paper describes an approach to reengineering the supplier evaluation process at an industrial company. The proposed supplier evaluation system encompasses three perspectives, the technology life-cycle, the relationship life-cycle, and the supplier capabilities. A methodology is provided for identifying key characteristics of the supplier/customer relationship, analyzing characteristics based on functional importance and potential for evaluation, aggregating characteristics in a comprehensive model, performing supplier evaluation and source selection, and mapping the progress of the supplier/customer alliance.
This paper presents a procedure for warehouse layout. It employs the principles of class-based storage to increase floor space utilization and decrease material handling. Three phases of the procedure are outlined: (1) determination of aisle layout and storage zone dimensions, (2) assignment of material to a storage medium, and (3) allocation of floor space. An industrial case study illustrates the procedure for a warehouse required to store 739 different products totaling more than 10,000 pallets of material. An improved layout was developed and compared to the existing alternative. The proposed layout offered savings of more than 20,000 square feet of floor space and approximately a 45 percent reduction in material handling distance.
In this paper, an analytical approach for the availability evaluation of cellular manufacturing systems is presented, where a manufacturing system is considered operational as long as its production capacity requirements are satisfied. The advantage of the approach is that constructing a system level Markov chain (a complex task) is not required. A manufacturing system is decomposed into two subsystems, i.e., machining subsystem and material handling subsystem. The machining subsystem is in turn decomposed in machine cells. For each machine cell and material handling subsystem, a Markovian model is derived and solved to find the probability of a subset of working machines in each cell, and a subset of the operating material handling carriers that satisfies the manufacturing capacity requirements. The overall manufacturing system availability is obtained using a procedure presented in the paper. The novelty of the approach is that it incorporates imperfect coverage and imperfect repair factors in the Markovian models. The approach is used to evaluate transient and steady state performance of three alternative designs based on an industrial example. Detailed discussion of the results and the impact of imperfect coverage and imperfect repair on the availability of manufacturing system is presented. Possible extensions of the work and software tools available for model analysis are also discussed.
The IDEF methodology has been extensively used for modeling processes. Qualitative and quantitative reliability analysis and risk assessment of IDEF models is of interest to industry for several reasons. It identifies critical activities in a process, improves the process performance, and decreases downtime and operating cost of the process. To evaluate the reliability and risk associated with an IDEF3 model formal tools and techniques are required. This paper extends the system reliability evaluation techniques, i.e., the system reduction approach and minimum path and cut sets method for reliability evaluation of IDEF3 models. Representation of IDEF3 models as reliability graphs, generation of minimal path and cut sets of IDEF3 models with a path tree algorithm, and reliability analysis of IDEF3 models are the issues discussed in this paper. An algorithm for computing reliability of an IDEF3 model from a path set - activity incidence matrix is also presented. In addition, the fault tree analysis technique and minimum cut and path sets generation algorithms are applied for reliability evaluation and risk assessment of the parent activities in an IDEF3 model. A structural and reliability importance measure for parent activities in an IDEF3 model as well as for the elementary activities in a decomposed model are presented.
The selection of multi-functional teams is a key issue in concurrent engineering (CE). In order to select efficient CE teams, a model which considers all aspects of concurrent engineering is needed. To deal with the underlying complexities of the team selection process, a conceptual framework is required. In this paper, the Analytical Hierarchy Process (AHP) method is integrated with the Quality Function Deployment approach to establish a framework for selecting multi-functional teams. An example demonstrates how the importance measure for each team member is determined using the Analytical Hierarchy Process. A mathematical programming model is developed to form CE teams.
In this paper, a methodology for automatic generation of hierarchical Petri nets for control of manufacturing systems is developed. The methodology includes building a structural representation of a manufacturing process with the Integrated Definition 3 (IDEF3) methodology, decomposing the manufacturing process based on the similarity of resources, transforming the IDEF3 model into a Petri net control model, aggregating sub Petri net models, and scheduling the Petri nets. Specifically, a sequential cluster identification algorithm is developed to decompose a manufacturing system represented as an IDEF3 model. A scheduling approach is presented to generate an aggregated schedule from sub Petri net models. The computational experience shows that the methodology developed in this paper reduces the computational time complexity of the scheduling problem without significantly affecting the solution quality. The advantages of the methodology developed in this paper include the combined benefits of simplicity of the IDEF3 representation of manufacturing processes and analytical and control properties of Petri net models. The IDEF3 representation of a manufacturing process enhances the man-machine interface.
A virtual corporation is formed by different companies with their own technology and capacity. One problem encountered in forming a virtual corporation is to assign tasks to each partner company based on their strengths and scheduling the production. In this paper, two models are developed for production planning and scheduling in a virtual corporation. This virtual corporation is formed by a number of manufacturing companies (manufacturing centers) and assembly companies (assembly centers). The first model allocates products to the assembly centers so that the total average setup and inventory cost is minimized. The model is solved with an efficient heuristic algorithm. The second model deals with scheduling the manufacturing centers. The solution approaches developed in this paper are useful in design of products by suggesting appropriate product structures.
Reconfigurability is an important characteristic of modern manufacturing systems. Designing a reconfigurable manufacturing system requires understanding of the relationship between the structure of products and the corresponding manufacturing system. In this paper, the reconfigurability of assembly systems designed for modular products is studied. Product modularity allows to produce different products by combining standard components. One of the characteristics of modular products is that they share the same assembly structure for many assembly operations. An approach for design of reconfigurable assembly systems for modular products is proposed. The assembly system is decomposed into two subsystems based on the structure of modular products. The reconfiguration problem of the assembly system is formulated and solved by a tabu search based heuristic algorithm.
The design of parts and manufacturing systems can be viewed from different perspectives. This paper discusses the design of parts and manufacturing systems from reliability and maintainability perspectives. A convenient method of considering reliability and maintainability is through the use of design rules which are based on empirical and theoretical knowledge. Four design rules for improvement of reliability and maintainability of systems are presented. The design rules are proven and substantiated with numerical results. The relationship between the design for reliability and maintainability rules and design for manufacturing process rules is discussed.
A manufacturing system should be able to produce a variety of components at a low cost and in a short time. In this paper, the relationship between the design of components and reconfiguability of a manufacturing system is discussed. The components with similar routes are selected in order to minimize the number of machines to be relocated. Two formulations of the reconfiguration problem are presented. Machines are relocated based on several design rules. Selection of components and manufacturing resources for system reconfiguration is discussed. An algorithm which selects components and manufacturing resources is developed for the improvement of similarity of manufacturing processes.
Modularity refers to the use of common units to create product variants. As companies strive to rationalize engineering design, manufacturing, and support processes and to produce a large variety of products at lower cost, modularity is becoming a focus. However, modularity has been treated in the literature in an abstract form and it has not been satisfactory explored in industry. This paper aims at the development of models and solution approaches to the modularity problem for mechanical, electrical and mixed process products (e.g., electro-mechanical products). To interpret various types of modularity, e.g., component-swapping, component-sharing, and bus modularity, a matrix representation of the modularity problem is presented. The decomposition approach is used to determine modules for different products. The representation and solution approaches presented are illustrated with numerous examples.
Intelligent Systems Laboratory