| The emphasis of this research is the development of a methodology consisting of analytical models with which to make tool management decisions in a flexible manufacturing environment. The decisions included in the research are the order policy for each tool type, the maintenance and replacement policy for each tool type, and the number of tools active in the system simultaneously.;The EOQ inventory models with single and multiple replenishments are used to determine the appropriate scheduling period and order quantity for each tool type. The demand rate of a tool, required in the inventory models, depends upon the available machining time per tool. Two stochastic tool replacement models are developed to determine the available machining time per tool, which include the cost of inspecting and sharpening the tools. The first model, based on renewal theory, models each maintenance interval as a separate cycle. The objective is to minimize the expected cost per piece. The second model represents the entire life of a tool as one cycle which is subdivided into equal inspection/maintenance intervals. The objective of the model is to determine the length of the interval which minimizes the expected cost per unit time for a given number of maintenance operations. Both models are developed without reference to any particular tool life distribution.;The determination of the number of each tool type in the system is initiated using a part family--machine grouping clustering method to determine the minimum number of tools of each type needed in the system. A continuous-time Markov chain method is then used to determine the machine and tool utilization and part throughput statistics given the number of tools of a given type. The tool combination which balances the costs associated with the failure to meet production and the under-utilization of tools and machines is the one that must be chosen. Numerical examples are presented to validate the models and illustrate the methodology. |
