Analysis of machine tool failures using advanced reliability models for complex repairable systems

The competitiveness of modern markets has induced machine tool producers to realize high reliability innovative products. Nowadays, machine tool is an integration of extremely advanced technological devices able to perform tasks with high accuracy and flexibility. The main goal must be to guaranlce specified performances, but, above all, to maintain them for all the life cycle time. Reliability and maintainability analysis (R&M) of a complex system deals with many opportunities both for the producers and the customers. The analysis permits to understand the behavior of the machine and to obtain useful information in order to base maintenance policies on analytical results. In this paper a structured R&M analysis for repairable systems is applied to a set of lathes. Failure data are collected by the company customer service for thirty months. The whole system is decomposed into main groups and components. Life data analysis is applied and the failure distribution of the repairable groups is described through a non-homogeneous Poisson process. When complex repairable systems are considered, the reliability must be modeled taking into account that it is strictly influenced by maintenance actions that restore/renew system components when they fail. Finally an R&M perspective for the entire machine is shown.