Simulation of thermal behaviors of motorized spindle based on fractal theory and Monte Carlo method

The finite element analysis thermal-structure model of a spindle was proposed at the design stage to avoid the sudden failure in actual machining caused by the high temperature rise in the spindle components. The calculation method of bearing heat power, which regarded the contact angle as the iterative variable, was proposed to avoid the disadvantages of the traditional Newton-Raphson algorithm when the bearing quasi-static was analyzed, such as the poor convergence, slow convergence speed and low accuracy. The motor efficiency analysis method was applied to calculate the heat power of the built-in motor. To avoid the inaccuracy of the statistical methods and the poor generality of the experiment methods, the fractal theory and Monte Carlo method were utilized to calculate the thermal contact conductance between joint surfaces. Besides, the convective heat transfer coefficients of different components were calculated according to the Nusselt number. Furthermore, the spindle thermal deformation and temperature distribution were simulated by applying the above boundary conditions to the FEA model. The results show that the modeling approach of high-speed spindle thermal characteristics is correct and the FEA model can accurately predict the temperature distribution and thermal deformation.