Study On The Stability Of Ultra-high-speed Aerostatic Motorized Spindle

With the high-speed development of the consumer electronics industry, the demand of PCB circuit board is increasing gradually. In order to meet the processing requirement of high accuracy for PCB circuit board, the ultra high-speed aerostatic motorized spindle is widely used in PCB manufacturing industry. The hydrostatic bearing in which the lubricant is gas and without solid connection, has characteristics of high precision, high limiting speed, long life, small vibration and so on. It is suitable for the bearing components of ultra high-speed motorized spindle. However, Due to the special nature of the compressibility for gas, The ultra high-speed aerostatic motorized spindle not only has the disadvantages of low loading capacity, low stiffness, but also is more prone to instability when processing, which seriously affects the machine performance of ultra high-speed aerostatic motorized spindle and limits the application and development of the ultra high-speed aerostatic motorized spindle technology.It is desirable to master the methods of improving stability for electro-spindle system and the design method of ultra high-speed aerostatic motorized spindle by studying the static performance of aerostatic bearing, supporting form optimization of electro-spindle system, the mechanism, determinant and influencing factors of pneumatic hammer vibration and vortex instability. The main research of this article includes the following four aspects:1、Based on the establishment of gas-lubricated Reynolds equation and combined with the ANSYS finite element analysis software,it is important to make all parameters of three-dimensional fluid flow model and analyse for radial bearings and thrust bearings to devise the pressure distribution of gas film and capacity; On this basis, it is able to devise the influence of main structure parameters on the static performance of radial and thrust bearing, especially the influence on regular pattern of bearing capacity and stiffness, and then to optimize their structure parameters.2、The supporting configuration mode of ultra high-speed aerostatic motorized spindle is analyzed and optimized. According to mechanical knowledge, the stiffness of electric-spindle system with double support form and three support form is calculated, so the conclusion is drew that the stiffness of three support form in electric-spindle system is higher than the stiffness of double support form and the position of the third support form also affect the stiffness and it is better when the third support form become more near to the front of spindle; By using the method of fluid-structure interaction analysis, ANSYS software is used to analyze the stiffness of four different supporting forms of electro spindle, which is the deformation of spindle under the same radial load, thus optimizing the best supporting form.3、The stability of electric-spindle system are analyzed, that is the mechanism determinant and influencing factors of pneumatic hammer vibration and vortex instability. Taking thrust bearing for example, the discriminant of thrust bearings producing pneumatic hammer vibration is deduced, Matlab software is used to carry on the simulation analysis of the structure parameters, including gas film thickness, orifice diameter, gas pressure and gas cavity radius, to find out how the four structure parameters affect the pneumatic hammer vibration;Based on the simplified model of motorized spindle,the linear perturbation method are used to deduce the discriminant criterion of dynamic stability and critical velocity and limit velocity of electric-spindle system; From the perspective of numerical analysis, there is a research on the relationship between damping coefficient and eccentricity, spindle rotation speed and whirling speed; The measures to improve the stability of electro-spindle system is put forward. A new three-dimensional structure of ultra high-speed aerostatic motorized spindle is put forward, carrying the simulation analysis of radial bearing performance on it.4、By using the method of fluid-structure interaction analysis, modal analysis is carried out on electro-spindle system to obtain the inherent frequency and vibration mode, harmonic response analysis concludes the dynamic change of the displacement of the spindle front end under the external exciting force, which is reference basis for the practical operation and the processing of motorized spindle.