Assessment of the tool post reliability of a high-stiffness turning machine

Reliability refers to the ability of a part, device or system to conduct an intended function in a given condition for a certain period of time. A mechanical system or structure such as a machine tool exercises the capacity of the entire system with regard to the various constituent parts that are connected to each other; as such, the reliability of the parts constituting the system determines the reliability of the entire system. A tool post is a device designed to efficiently provide the tools necessary for the processing of a turning machine: the parts used in a hard turning machine which requires higher stiffness must provide greater reliability. For the purposes of this study, the reliability of a tool post, which has the highest failure rate of a turning machine system, was assessed. In order to conduct a reliability assessment of a given tool post, reliability prediction using a failure rate database, weak point analysis, the manufacture of a reliability tester and the calculation of reliability testing and quantitative reliability criteria were also carried out. By so doing, the failure rate, the MTBF (Mean time between failures) and other factors could be calculated. Furthermore, the results can also be applied to other parts of the turning machine or to a reliability assessment of a subsystem by using the suggested assessment method.