Thesis (M.S.)--Ohio University, March, 2006. / Title from PDF t.p. Includes bibliographical references (p. 87-89)

published_or_final_version / abstract / Industrial and Manufacturing Systems Engineering / Master / Master of Philosophy

Cellular Manufacturing Systems (CMS) have claimed many advantages over traditional job shop processes. Some of the advantages reported by several users of CMS are reduction in throughput time, reduction in WIP inventory, improvement in product quality, faster response time to customer orders, shorter move distances, increase in manufacturing flexibility, and greater job satisfaction. In its implementation, CMS organizes a production floor into manufacturing cells. Hence, the important issue that needs to be addressed first is the cell formation (CF) problem. CF deals with the identification of part families, machine groups, and allocation of part families and machine groups to cells or vice versa. In the past, most studies in CF have assumed that the location of a cell is known a priori and a unique route exists between two cells. However, in an actual manufacturing environment, alternative locations are available for locating each cell. Similarly, when the capacity of the material handler being used is limited, alternative routes may have to be used to move part loads between two cells. In this research, the issues dealing with alternative cell locations and alternative routes of material handling equipment are investigated. In addition, several other important factors common to CF are also considered. These include machine capacity limitations, batches of part demands, non-consecutive operations of parts, and maximum number of machines assigned to a cell. A mathematical model is first formulated to represent the research problem. The model is a binary and general integer non-linear programming model, and it belongs to the class of NP-hard problem. Therefore, a higher level heuristic algorithm, based on the concept known as tabu search, is developed to efficiently solve the problems with industry merit. Incorporating the features associated with the tabu search, resulted in developing six different versions of the heuristic solution algorithm. The six heuristics are tested on twenty small problems, and the quality of their solutions is evaluated by investing significant effort to find their optimal solutions. The evaluation shows that the heuristics are highly effective. The solutions obtained from the heuristics have average percentage deviation of less than 3% from the optimal solutions. The heuristics are also tested on their performances with medium and large problems. By using a statistical experiment that is based on randomized block design, the performance of the six heuristics is compared. Three different problem structures, ranging from 4 parts to 30 parts and from 3 locations to 9 locations are used in the experimentation. The experiment reveals that in general, the tabu search based-heuristic using fixed tabu list size and long-term memory based on minimal frequency strategy is preferred to other heuristics as the problem size increases. / Graduation date: 2000

Cellular Manufacturing Systems (CMS) have provided significant increase in manufacturing productivity over the last two decades. This has been achieved because CMS can overcome the problems due to frequent setups, high in-process inventories, long throughput times and complex planning and coordination commonly associated with a batch-type manufacturing operation. The underlying concept of CMS is the grouping of parts into part families and the machines that process these parts into machine cells in order to achieve manufacturing efficiencies. Creating machine cells which can perform all operations of a part without requiring the part to visit one or more cells other than its own is hard to achieve, if not impossible. Hence, in the design of CMS, one tries to minimize the material handling costs incurred due to the movements of parts to other cells. Duplication of "bottleneck" machines that process parts assigned to other cells into the appropriate cells and subcontracting of "bottleneck" parts that require one or more operation on machines assigned to another cell are two important methods utilized to form disaggregated manufacturing cells in order to minimize the material handling costs. A mathematical model and a solution algorithm is developed to simultaneously deal with the issues of duplicating bottleneck machines and subcontracting bottleneck parts. Because there is a cost associated with the process of duplication and subcontracting, the benefits attained are analyzed for different budgetary constraints encountered by a firm. The algorithm was tested on three different problem structures for a range of budgetary restrictions. The results obtained show that the algorithm could be used by the industry to solve problems encountered in the design of CMS. / Graduation date: 1994

Thesis (M.S.)--Rochester Institute of Technology, 2007. / Typescript. Includes bibliographical references (leaves 86-90).

Thesis (Ph. D.)--Lehigh University, 2000. / Includes vita. Includes bibliographical references (leaves 107-112).

Thesis (M. Phil.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.

Analysis of flexible manufacturing cells (FMCs) shows their requirement for flexible, correct, reliable, safe and distributed control. A comparison of the state of the art in software engineering for parallel systems, and an examination of safety related systems, reveal a need for formal and rigorous techniques at all stages in the software life cycle. However, parallel software, safety related software and formal techniques are complex. It is better to avoid faults rather than eliminate or tolerate them, and although less flexible, avoidance is often simpler to implement. There is a need for a tool which overcomes many of these complexities, and this thesis discusses and defines such a tool in the form of a methodology. The novelty of the work is in the combination of the core goals to manage these issues, and how the strategies guide the user to a solution which will not deadlock and which is comprehensible. Place-transition Petri nets are an ideal representation for designing and modelling the interaction of concurrent (and distributed) processes. Occam is a high level real time parallel language designed to execute on one or a network of transputers. Transputers are processing, memory and communication building blocks, and, together with occam, are shown to be suitable for controlling and communicating the control as the DCS in FMCs. The methodology developed in this thesis adopts the mathematically based tools of Petri nets, occam and transputers, and, by exploiting their structural similarities, incorporates them in a steps and tasks to improve the development of correct, reliable and hence safe occam code. The four steps: identify concurrent and sequential operations, produce Petri net graphs for all controllers, combine controller Petri net graphs and translate Petri net graphs into occam; are structured around three core goals: Petri net/occam equivalence, comprehensibility and pro-activity; which are manifest in four strategies: output-work-backwards, concurrent and sequential actions, structuralise and modularise, and deadlock avoidance. The methodology assists in all stages of the software development life cycle, and is applicable to small DCSs such as an FMC. The methodology begins by assisting in the creation of DCS requirements from the manufacturing requirements of the FMC, and guides the user to the production of dependable occam code. Petri nets allow the requirements to be specified as they are created, and the methodology's imposed restrictions enable the final Petri net design to be translated directly into occam. Thus the mathematics behind the formal tools is hidden from the user, which should be attractive to industry. The methodology is successfully applied to the example FMC, and occam code to simulate the FMC is produced. Due to the novelty of the research, many suggestions for further work are given.

Cell formation in cellular manufacturing deals with the identification of machines which can be grouped to create manufacturing cells as well as the identification of part families processed within each cell. Manufacturing flexibility is the property of the system components that are integrally designed and linked to each other in order to allow the adaptation to various tasks. This research focuses on classifying and quantifying several types of cellular manufacturing flexibility. These types are defined in order to respond to internal and external changes. Based on these definitions, we link components of the cellular manufacturing systems (part families and machine groups) to develop a CM flexibility hierarchy. Several cellular flexibility and structural measures are developed at each level of the CM flexibility hierarchy and for each component of the CM systems. These measures can be used in order to evaluate and/or design cellular manufacturing systems. A new cell formation method (Flexible Cell Formation method), which has several unique features, is developed. This method incorporates the flexibility measures in designing cellular systems and can generate several alternative designs with different levels of flexibility. The method developed also uses a new similarity measure which incorporates machine processing capability. The proposed method is compared to selected methods of cell formation. Finally, this research concludes with a comprehensive experimental analysis to investigate the impact of several input parameters. The results are used to show how each parameter should be set by the user of the method to incorporate specific types of flexibility.

Thesis (M.S)--Ohio University, March, 2005. / Includes bibliographical references (p. 131-136)