Study On The Dynamic And Static Performance Of Micro-hole Array Aerostatic Motorized Spindle

With requirements and development trend of miniaturization, lightweight, more functional of consumer electronics, the requirement for the new generation of electronic systems for Printed Circuit Board (PCB, Printed Circuit Board) is high density, high integration and miniaturization. In order to improve the production efficiency, reduce processing costs, ensure the quality of processing, the PCB micro-hole generally uses the processing method of high-speed drilling. The high-speed aerostatic motorized spindle is the core components to realize the high speed and effective drilling of PCB micro-hole, it uses the aerostatic bearing as the support element. The printed circuit board is made up of resin and high purity metals, the cutting force are obvious different when drilling different materials, this requires ultra-high-speed motorized spindle has high rigidity, high bearing capacity and good stability, so as to ensure the accuracy of drilling.This article takes high-speed motorized spindle which is used for PCB NC drilling machine as the research object, by studying the air bearing stability and dynamic and static performance to achieve the optimal design of a new type of micro-hole array aerostatic bearings, then applied to the high-speed motorized spindle and analyze the dynamic and static characteristics. The main research contents of this article includes the following aspects:The general form of the Reynolds equation is established on the basis of the analysis of the static pressure gas lubrication theory, the distribution of pressure field and velocity field of aerostatic bearing gas film and cyclone intensity of flow field are researched in the Workbench environment by FLUENT software, Calculating the pressure drop and cyclone intensity of the flow field to analyze the influence of different structure parameters of micro-hole array restrictors on the stability of the aerostatic bearings.The three-dimensional model of micro-hole array aerostatic bearings with different structures are established. The effects on the static characteristics of aerostatic bearings are studied when the number or diameter of the micro-hole, or the average radius clearance, or the axial location of restrictor is changed. The results of the analysis canserve to guide the optimal design of micro-hole array aerostatic bearings.The dynamic characteristics of micro-hole array aerostatic bearing under different working conditions by finite element method. For aerostatic bearing which is in the condition of rotation, the influence of the eccentricity, bearing rotating speed on the bearing capacity, stiffness and pressure distribution of the bearing were studied.The motorized spindle has carried on a detailed 3D design. Establishing the parametric 3D model of the motorized spindle, the static characteristics of the spindle is analyzed by fluid-structure interaction method, then the displacement and rigidity characteristics of the spindle system are obtained with the change of external load.Modal analysis of motorized spindle is carried out to obtain the natural frequency and vibration mode of the spindle system, then calculating the vortex instability critical speed of the spindle; the dynamic response of the spindle system is analyzed under the external incentive, so as to get the front displacement change of the spindle under the external incentive.The results show that the stability of micro-hole array aerostatic bearings are better than orifice compensated aerostatic bearings under the same conditions. It can improve the stability of the bearing when reducing the diameter or increasing the number of micro-holes within a certain range. The optimal designed micro-hole array aerostatic bearings has the characteristics of high bearing capacity and stiffness, the aerostatic motorized spindle which is designed with the micro-hole array aerostatic bearings has a high axial stiffness, the front displacement of the spindle is small under the external incentive. The spindle has a good static and dynamic performance, which is suitable for the requirement of high speed and high precision processing of printed circuit board.