Research Of The Built-in Electric Spindle Dynamic And Thermal-structure Coupling Characteristics

High speed machining technology, as mechanical processing and manufacturing industry of advanced technology, has played an important role to improve the production efficiency of machining manufacturing and the quality of products. The increase of spindle speed makes the spindle bearing severe fever, which makes the main shaft deformation serious; what’s more, leading to a lower precision. As a result, the dynamic characteristics and thermal-structure coupling characteristics analyses of the spindle are of great significance.To begin with, this article designs the overall structure on electric spindle units, including the selection of motor and bearings, the determination of important parts parameters and related calculation, and then the motorized spindle is analyzed by finite element analysis method. For the dynamic characteristics research, this paper established 3D model of the electric spindle unit using Solidworks, and import to ANSYS software to process modal analysis by block method, then the harmonic analysis is done using modal superposition method. The thermal-structure characteristic is analyzed by indirect coupling analysis method. After confirming the boundary conditions, the steady state thermal analysis is done first, then to study the thermal stress and thermal displacement. Finally, the zero order approximation of function optimization method is used for further optimization of the spindle thermal deformation.Through the modal analysis, the natural frequency, mode shape and the critical speed are gained to verify the rationality of the design parameters; through the harmonic analysis, the relationship between motorized spindle end displacement and the excitation frequency of motorized spindle is obtained, and weak spot is found in the middle of the shaft. Put forward to improve front bearing preload and adjust electric spindle span and front overhang appropriately to improve the dynamic characteristic of the motorized spindle. The displacement deformations, thermal stress field distribution of motorized spindle are got through thermal analysis, and find that the motor rotor temperature rise, radial displacement, axial displacement of shell and stress change of the bearing are the largest biggest. Through the optimization, the mean thermal deformation of spindle front-end has been reduced, and the maximum deformation and axis beating are smaller. In this way, the precision of the spindle drive is improved.