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In this thesis, we develop integer programming models which find the optimal part-machine family solutions, that disaggregate a factory process at the lowest cost. The groupings created using the methods presented in this thesis can then act as the basis for the application of Group Technology, which include machine placement, job scheduling, and part routing. Four exact 0−1 Linear Programming techniques are developed and presented. The first 0 − 1 Linear Programming technique only focuses on part subcontracting as a means to disaggregate, and the second only focuses on machine duplication to disaggregate. The final two methods both yield part-machine family disaggregation through simultaneous part subcontracting and machine duplication. Once these methods are applied to example problems, the results provide the exact solutions, which have not been found in previous work. / NSERC Discovery Grant

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Shorter product life-cycles, unpredictable demand, and customized products have forced manufacturing firms to operate more efficiently and effectively in order to adapt to changing requirements. Traditional manufacturing systems, such as job shops and flow lines, cannot handle such environments. Cellular manufacturing, which incorporates the flexibility of job shops and the high production rate of flow lines, has been seen as a promising alternative for such cases. Although cellular manufacturing provides great benefits, the design of cellular manufacturing systems is complex for real-life problems. Existing design methods employ simplifying assumptions which often deteriorate the validity of the models used for obtaining solutions. Two simplifying assumptions used in existing design methods are as follows. First, product mix and demand do not change over the planning horizon. Second, each operation can be performed by only one machine type, i.e., routing flexibility of parts is not considered. This research aimed to develop a model and a solution approach for designing cellular manufacturing systems that addresses these shortcomings by assuming dynamic and stochastic production requirements and employing routing flexibility. A mathematical model and an optimal solution procedure were developed for the design of cellular manufacturing under dynamic and stochastic production environment employing routing flexibility. Optimization techniques for solving such problems usually require a substantial amount of time and memory space, therefore, a simulated annealing based heuristic was developed to obtain good solutions within reasonable amounts of time. The heuristic was evaluated in two ways. First, different cellular manufacturing design problems were generated and solved using the heuristic. Then, solutions obtained from the heuristic were compared with lower bounds of solutions obtained from the optimal solution procedure. The lower bounds were used instead of optimal solutions because of the computational time required to obtain optimal solutions. The results show that the heuristic performs well under various circumstances, but routing flexibility has a major impact on the performance of the heuristic. The heuristic appears to perform well regardless of problem size. Second, known solutions of two CM design problems from literature were used to compare with those from the heuristic. The heuristic slightly outperforms one design approach, but substantially outperforms the other design approach. / Ph. D.

The group scheduling problem commonly arises in cellular manufacturing systems, where parts are grouped into part families. It is characterized by a sequencing task on two levels: on the one hand, a sequence of jobs within each part family has to be identified while, on the other hand, a family sequence has to be determined. In order to solve this NP-hard problem usually heuristic solution approaches are used. In this thesis different aspects of group scheduling are discussed and problem specific heuristics are developed to solve group scheduling problems efficiently. Thereby, particularly characteristic properties of flowshop group scheduling problems, such as the structure of a group schedule or missing operations, are identified and exploited. In a simulation study for job shop manufacturing cells several novel dispatching rules are analyzed. Furthermore, a comprehensive review of the existing group scheduling literature is presented, identifying fruitful directions for future research.

This research examined the relationship between manufacturing input parameters and factory performance in a cellular manufacturing environment.

O conceito de manufatura enxuta está sendo considerado mais e mais um novo paradigma para um número grande de empresas no mundo. Original da indústria automobilística, o conceito produção enxuta tem sido espalhado para todos os tipos de indústrias. Este trabalho apresenta uma implementação do sistema de produção enxuta em uma indústria calçadista. Tem como objetivo maior apresentar a aplicação dos conceitos de um sistema de formação de células no setor de costura. A criação destas células é vital porque a maioria das atividades são operações intensivamente manuais e células promovem a oportunidade para uma melhor utilização do operário no balanceamento e padronização das operações. As células também permitem uma melhor utilização do espaço e menor estoque intermediário. Um grande desafio para esta atividade é a alta variedade de produtos com alta variedade de seqüências nas operações de costura. Logo, este trabalho apresenta um levantamento bibliográfico, fazendo uma caracterização sobre evoluções dos sistemas de administração da produção salientando a importância do sistema de produção enxuta, bem como conceitos básicos de layout e manufatura celular, apresentando neste contexto sua relevância e medidas utilizadas nas empresas para tomada de decisões e ações. Apresenta também um método para a formação de células em empresas deste setor, desenvolvido através de pesquisa-ação. Além disso, é apresentado um caso real de implantação deste método em uma empresa de calçados esportivos e são discutidos os resultados obtidos. / The concept of lean manufacturing is being considered more and more a new paradigma for a number of companies worldwide. Originally from the automotive industry, the concept of lean production has been spread to all types of industry. This work presents an implementation of the lean production system in a shoe industry. Its main purpose is to present the application of the concepts of this system to the cell formation in the sewing sector. The creation of these cells is vital because most of the operations are intensely manual and cells provide the opportunity for a better use of the worker in the balancing and standardization of the operations. Cells also allow a better use of the space and less work in process. A great challenge for this activity is the high variety of products with high variety of sequences in the operations of sewing. Therefore, the study presents a research on the evolution of the production administration system showing the importance of the lean production system, as well as basic concepts of layout and cellular manufacturing, presenting in this context its relevance and the performance measurements used in industries for the decision making and actions. It also presents a method to the cell formation in shoe industries, developed from an action-research. It is presented a real case of implementation of this method in a sportive shoe industry and discussed its results.