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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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No description available.

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No description available.

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.

The objective of the cellular manufacturing is to simplify the management of the manufacturing industries. In regrouping the production of different parts into clusters, the management of the manufacturing is reduced to manage different small entities. One of the most important problems in the cellular manufacturing is the design of these entities called cells. These cells represent a cluster of machines that can be dedicated to the production of one or several parts. The ideal design of a cellular manufacturing is to make these cells totally independent from one another, i.e. that each part is dedicated to only one cell (i.e. if it can be achieved completely inside this cell). The reality is a little more complex. Once the cells are created, there exists still some traffic between them. This traffic corresponds to a transfer of a part between two machines belonging to different cells. The final objective is to reduce this traffic between the cells (called inter-cellular traffic). Different methods exist to produce these cells and dedicated them to parts. To create independent cells, the choice can be done between different ways to produce each part. Two interdependent problems must be solved: • the allocation of each operation on a machine: each part is defined by one or several sequences of operations and each of them can be achieved by a set of machines. A final sequence of machines must be chosen to produce each part. • the grouping of each machine in cells producing traffic inside and outside the cells. In function of the solution to the first problem, different clusters will be created to minimise the inter-cellular traffic. In this thesis, an original method based on the grouping genetic algorithm (Gga) is proposed to solve simultaneously these two interdependent problems. The efficiency of the method is highlighted compared to the methods based on two integrated algorithms or heuristics. Indeed, to form these cells of machines with the allocation of operations on the machines, the used methods permitting to solve large scale problems are generally composed by two nested algorithms. The main one calls the secondary one to complete the first part of the solution. The application domain goes beyond the manufacturing industry and can for example be applied to the design of the electronic systems as explained in the future research.