A General Optimization Model for Multi-Tool Manufacturing Systems

A machining center is a single numerically-controlled machine that incorporates several time-saving features and performs a multiplicity of operations. The life of cutting tools used in machining centers is modeled using probabilistic methods because of the stochastic nature and variability of tool-wear data. An approximate expression for the renewal function is used to establish an optimum scheduled tool replacement interval and an optimum set of cutting conditions to obtain a minimum production cost. A general optimization model for the multi-tool machining center is formulated considering practical machine constraints. Premature failure cost is not considered constant in this study. It is estimated using the tool cost, the expected cost of unplanned downtime, and the expended cost of product damage by premature tool failure. A user friendly computer program was developed to solicit information from a production engineer regarding cutting operations for the various tools used at the machining center. A sensitivity analysis on the results of the optimization process is presented.