Reliability Analysis of Machine Tool Structures

A method of estimating the reliability of machine tool structures is developed. The reliability analysis of horizontal milling machines in various failure modes, like static deflection, fundamental natural frequency and chatter stability, is considered for illustration. The table height, distance of the cutter center from the arbor support, damping factor, Young’s modulus of the material and the load acting on the cutter and the table are considered as random variables. The finite-element displacement method is used to idealize the structure. The reliability analysis is based on the linearization of a function of several random variables about the mean values of the random variables. The overall reliability of the machine tool structure is found by treating it as a weakest-link system having several failure modes. A sensitivity analysis is also conducted to find the variaion of reliability with a change in the coefficients of variation of different random parameters.