Study On The Relationships Between Preload Of CNC Machine Spindle And Its Dynamic Characteristics

With the development of the technology, the CNC machine is getting more high-speed and more precision. In order to work under the high-speed, high efficiency, and stable condition, the better structure dynamic characteristics for the CNC machine is needed. As one of the most significant element of the machine, the dynamic characteristic of the spindle has a great effect on the efficiency, the performance and the stability for the whole machine. Therefore, the research on the factor of the dynamic characteristics of spindle is of great significance.With the research on the TDNC320 CNC machine, the relationship between the preload of the spindle system and its dynamic characteristics is mainly discussed.First of all, the relationship between the former support-the conical bore biserial column roller bearing and the preloaded momental of the bearing is studied. the functional curve between the radial rigidity and the preloaded momental is got. the functional curve between the radial rigidity of the back support-the cone roller bearing and the preloaded momental is got either. The finite element analysis of the spindle is done. The first two step free frequency and whirling speed are got.Second, the spindle is regarded as isotropism support, with the transfer matrix method, the radial rigidity of both former support and back support are substituted into the matrix, the first step free frequency and whirling speed under the different preloaded momental are calculated. The functional curve between first step free frequency and the preloaded momental is got.Finally, the motivation experiment of the spindle and the spindle system by the hammering method is done, the first step free frequency of the spindle system with different preloaded momental is got. the comparison between the experimental value and the theoretical value by the transfer matrix method is proceed.The experimental value and the theoretical value are basically concordance, the relationship between the spindle system and the preloaded momental is proved.