Dynamic reliability analysis of CNC lathe spindle-bearing system with thermal effect in radial runout

As one of the key components of computerized numerical control (CNC) lathes, the dynamic characteristics of spindle-bearing system has a vital influence on machining performance. Analyzing the kinematic error of spindle-bearing system is of great significance for investigating its radial runout and optimizing CNC lathe. The failure mode of CNC lathe spindle-bearing system with thermal effect is defined as the dynamic displacement of shaft end exceeds the allowable radial runout. Firstly, a dynamic model of system with thermal effect under random geometric parameters is presented to carry out the reliability analysis of radial runout. The stochastic perturbation method is applied to determine the first four moments of system dynamic displacement. Random variables and derivatives of system differential equations can be arranged into two-dimensional matrices used with Kronecker algebra. In addition, the reliability and its reliability sensitivity of system are obtained to study the influence of random parameters on the reliability of system. A CJK-6130 CNC lathe is used as a practical example of proposed model. Furthermore, the comparison between numerical calculation and Monte Carlo simulation is used to verify the proposed method. Eventually, the effects of mean values and variances of bearing random parameters on the radial runout are discussed.