Data Dependent Systems Approach to Stochastic Tool Life and Reliability

A Data Dependent Systems approach is outlined for obtaining tool life distribution and reliability models directly from shop floor and/or laboratory failure data. The approach does not require any a-priori knowledge of the distribution and can be used with a limited amount of data. Estimation of the first order model is illustrated by application to HSS tools in turning. The tool life signatures at three different speeds are exhibited in the form of plots of hazard rate, reliability and failure time probability density functions. Formulation of simple tool replacement strategies from these plots by the shop personnel is illustrated; the mathematical expressions given for these functions can be used to develop more elaborate optimal strategies in computerized adaptive control. It is shown that most of the commonly used tool life distributions are well approximated by special cases of the first order model and hence are included in the approach.