Herman R. Leep

Forming part families by using genetic algorithm and designing machine cells under demand changes

This study develops a methodology which can be used to form manufacturing cells using both a new similarity coefficient based on the number of alternative routes during machine failure and demand changes for multiple periods. The methodology is divided into two phases. A new similarity coefficient, which considers the number of available alternative routes when available during machine failure, is suggested in Phase I. The primary objective of Phase I is to identify part families based on the new similarity coefficient by using a genetic algorithm. One of the major factors contributing to the success of cell implementation is flexibility for demand changes. It is difficult to reorganize the cells according to changes in demand, available machine capacity, and due date. Most of the suggested approaches in the literature tend to use a fixed demand for cellular manufacturing systems. Due to demand changes, cell design should include more than the one period that most researchers of cellular manufacturing systems consider. A new methodology for cell formation, which considers the scheduling and operational aspects in cell design under demand changes, is introduced in Phase II. Machines are assigned to part families by using an optimization technique. This optimization technique employs sequential and simultaneous mixed integer programming models for a given period to minimize the total costs which are related to the scheduling and operational aspects.

A cellular manufacturing system based on new similarity coefficient which considers alternative routes during machine failure

A two-phase procedure for configuring a cellular manufacturing system is proposed. In Phase I, a new similarity coefficient which considers the number of alternative routes when available during machine failure is proposed. The objective of Phase I is to identify part families based on the proposed new similarity coefficient. In Phase II, a new methodology which simultaneously considers scheduling and operational aspects in the cell design during machine failure for a manufacturing environment is proposed. Phase II shows how the scheduling and operational aspects influence the resource utilization during machine failure. The objective of the proposed methodology is to minimize the total sum of inventory holding cost, early/late finish penalty cost for each part in a given period, operating cost and machine investment cost by grouping machines into cells.

A vehicle routing problem solved by using a hybrid genetic algorithm

The main purpose of this study is to find out the best solution of the vehicle routing problem simultaneously considering heterogeneous vehicles, double trips, and multiple depots by using a hybrid genetic algorithm. This study suggested a mathematical programming model with a new numerical formula which presents the amount of delivery and sub-tour elimination. This model gives an optimal solution by using OPL-STUDIO(ILOG CPLEX). This study also suggests a hybrid genetic algorithm (HGA) which considers the improvement of generation for an initial solution, three different heuristic processes, and a float mutation rate for escaping from the local solution in order to find the best solution. The suggested HGA is also compared with the results of a general genetic algorithm and existing problems suggested by Eilon and Fisher. We found better solutions rather than the existing genetic algorithms.

A novel approach for measuring agility in manufacturing firms

Manufacturing firms have great interest in developing their manufacturing systems to be more competitive in terms of flexibility and agility. Agile Manufacturing Systems (AMS) will be considered as the next industrial revolution. They are manufacturing and/or management philosophies that integrate the available technology, people, manufacturing strategies, and management systems. Although agility is the set of capabilities and competences that the manufacturing firms need to thrive and prosper in a continuously changing and unpredictable business environment, measuring the level of agility in these firms is still unexplored according to the capabilities and competences. As there are many important components (issues) to be included in embracing AMS, there are also many important questions to be asked concerning the existing firms agility level and how to assist in achieving enhancing agility more effectively. In this paper, a novel model will be proposed to measure the agility level of the manufacturing firms based on existing technologies, level of qualifying people, manufacturing strategies, and management systems and the business process. A complete case study will be presented.

Part family formation based on alternative routes during machine failure

Abstract A number of research papers have used different types of similarity/dissimilarity coefficients for determining part families. In cellular manufacturing systems, most machines are capable of performing more than one operation, which makes parts rerouting feasible. When a part is rerouted, it affects the cell performance. Most of the suggested approaches in the literature develop a new similarity coefficient based on mathematical analysis, however, these methods tend to disregard alternative routes during machine failure. The main objective of this paper is to identify part families based on a new similarity coefficient which considers the number of alternative routes available during machine failure. Based on the new similarity coefficient, the part families were identified by using p-median model.

Introducing new parts into existing cellular manufacturing systems based on a novel similarity coefficient

Over the last three decades, designing cellular manufacturing systems (CMS) still centres on assigning machines to machine cells and parts to part families. This task ends after assigning these part families to the appropriate machine cells. In the past, testing CMS was evaluated according to the efficiency of clustering, but actual testing of CMS after installation is still unexplored. Introducing one or more new parts (products) into CMS without any changes in the installation of the cells during processing of the current parts is a new concept to be considered and evaluated. Transferring these systems from traditional ideologues to advanced ideologues (agile systems) is highly desired. This concept can be considered as part (product) flexibility in CMS. To address this concept, a new similarity coefficient between the new part and the existing manufacturing cell will be created. New productivity and flexibility measurements in CMS will also be suggested. A new strategy for accepting a new part into CMS will be proposed based on machine utilization and flexibility in the cells, cell utilization and flexibility in the system, product flexibility (system flexibility), and similarity of this part with existing manufacturing cells. A complete analytical example will be presented.

Manufacturing process planning in a concurrent design and manufacturing environment

Concurrent design and manufacturing attempts to consider all aspects of the product during the early stage of design to avoid the costly and time consuming downstream traditional design and manufacturing processes. Process planning links design and manufacturing. This paper discusses the roles of manufacturing process planning in a concurrent engineering environment and the research on the development of prototype feature-based automated process planning (FBAPP) system for concurrent design and manufacturing.

A product data exchange integration structure using PDES/STEP for automated manufacturing applications

Abstract This article describes an integration structure of product data exchange with PDES/STEP using an object-oriented approach for automated manufacturing applications. A data carrier is provided for the data operational process in the integration structure. In the data carrier, these data are derived from previous operations and the CAD data are translated into a neutral file that is based on the EXPRESS language representation and PDES/STEP data definition. As an international standard of product data exchange, PDES/STEP is intended to provide information for all engineering applications without considering hardware, software, or processes. This application of the integrated structure with a neutral file is explained by an example on an HP/UNIX X Window system using object-oriented programming, CLIPS inference software, and I-DEAS software.

Simulation-based methodology for machine cell design

This paper presents a simulation-based methodology which uses both design and manufacturing attributes to form manufacturing cells. The methodology is implemented in three phases. In phase I, parts are grouped into part families based on their design and manufacturing dissimilarities. In phase II, machines are grouped into manufacturing cells based on relevant operational costs and various cells are assigned part families using an optimization technique. Phases I and II are based on integer and mixed-integer mathematical models. Finally, in phase III, a simulation model of the proposed system is built and verified, and the model is run so that data on the proposed system may be gathered and evaluated. The mathematical and simulation models are used to solve a sample production problem. The results from these models are compared, and can be used to justify the final design. By the use of these modeling tools, cellular manufacturing systems can be designed, analyzed, optimized, and finally justified.

Part family formation based on a new similarity coefficient which considers alternative routes during machine failure

A number of research papers have used different types of similarity and dissimilarity coefficients for determining part families. In cellular manufacturing systems, most machines are capable of performing more than one operation, which makes parts rerouting feasible. When a part is rerouted, it affects the cell performance. Most of the suggested approaches in the literature develop a new similarity coefficient based on mathematical analysis, however, these methods tend to disregard alternative routes during machine failure. The main objective of this paper is to identify part families based on a new similarity coefficient which considers the number of alternative routes available during machine failure. Based on the new similarity coefficient, the part families were identified by using a p-median model.