Reliability assessment for multiple NC machine tools oriented to general repair

Abstract

An approach of assessing reliability for multiple NC machine tools with general repair based on log-linear proportional intensity model (LPIM) is proposed, and an LPIM function for failure times is built. Point and confidence bounds estimates of model parameters are given by maximum likelihood method and Fisher information matrix method. Point estimates of reliability metrics are also derived with their confidence bounds offered through Delta method. Likelihood ratio tests are adopted to check the time trend and repair effect. A real example analysis demonstrates that, LPIM approach outperforms Weibull distribution method and NHPP model considering the effects of repair activities, capable to capture quantitatively repair effects on machine tools reliability, hence the instantaneous and cumulative reliability properties obtained more practical. © 2013 Journal of Mechanical Engineering.