| Generally speaking,high-speed spindle system refers to the motorized spindle system with cutting speed of 12000 r/min and cutting feed rate of more than 30m/min.its main components include motorized spindle unit,toolholder and props.High speed spindle system to a large extent to solve some of the traditional problems in high-speed machining process,such as vibration and noise,etc.,accuracy is also greatly improved,on the other hand,it can greatly improve production efficiency,widely used in high-speed machining occasions.In recent years,foreign countries have made breakthroughs in high-speed cutting related fields one by one.High-power spindle units and high-performance servo systems have come out one after another,which makes the United States,Japan,Germany and other industrial developed countries take the lead in this field,and have applied high-speed cutting technology to many high-precision industrial sectors.As the equipment manufacturing industry is the foundation of national economy,its importance is self-evident,resulting in high-speed cutting is also an important research content in China,but there is still a certain gap compared with some developed countries.The research on high-speed spindle system is a breakthrough to realize China’s leading position in the field of high-speed cutting technology.Although the high-speed spindle system has greatly improved the machining accuracy and efficiency compared with the traditional machine tool system,it still can not avoid the phenomenon of cutting chatter in the process of processing,which affects the machining accuracy and production efficiency of the spindle system.Serious damage has occurred to the entire spindle,and even to the safety of the operator The threat.Therefore,it is necessary to predict and analyze the dynamic characteristics and stability of the high-speed spindle system,so as to improve the machining quality and accuracy of the high-speed machining center and ensure the safety of life and property.The main contents of this paper are as follows:(1)First of all,through a large number of reading literature on the development of highspeed spindle system and research status have a full understanding,on this basis,do some of the following column analysis.In Chapter 2,the contact characteristics and stiffness analysis of angular contact ball bearing,which is commonly used in motorized spindle unit,are analyzed.Firstly,the quasi-static model and stiffness model of rolling bearing are established.The influence of centrifugal force and gyroscopic moment can’t be ignored easily under high-speed operation condition.The influence of cage is the neglected factor in the quasi-static model.Then,the model equations are solved by MATLAB program,and the contact angle and contact of bearing caused by rotating speed and radial load are analyzed The influence law of load and preload on bearing stiffness.(2)In the second part,the finite element model of the high-speed spindle system is established,and the analysis flow of the system’s inherent characteristics is proposed.The frequency response function of the system is obtained by using the inherent characteristic method,and then the frequency response function curve image of the system is obtained by using MATLAB self programming.The influence of bearing stiffness of spindle unit,geometric parameters of spindle unit and bearing arrangement of spindle unit on the inherent characteristics of the system is analyzed.The influence of bearings at different positions is also different.The bearings distributed at both ends of the spindle have a greater impact on the second-order natural frequency of the main system,and the bearing distributed in the middle of the spindle unit has a greater impact on the second-order and third-order natural frequencies of the spindle system;the length variation of the spindle has an impact on all the natural frequencies of the tool tip,and the higher the order of the natural frequency,the greater the impact In addition,with the increase of spindle length,the natural frequencies of each order tend to decrease,that is,the longer the spindle is,the less stable the system is.The higher-order natural frequency of the tool tip of the spindle system is more easily affected by the bearing arrangement than the low-order natural frequency of the spindle system.When the bearings are concentrated in the middle of the spindle,the firstorder natural frequency of the spindle end point increases significantly.(3)In the third part,the cutting stability of high-speed spindle system is analyzed.According to different influencing factors,different methods of solving system frequency response function are used to obtain the system frequency response function,and then the lobe diagram of cutting stability of the system is drawn to analyze the influence of bearing support stiffness,cutting force amplitude,damping coefficient,rotation speed,number of cutter teeth and cutting force coefficient on the system The influence law of cutting stability.When the bearing stiffness increases,the limit cutting depth increases,and the cutting stability of the system is enhanced.The influence of cutting force amplitude is opposite to that of stiffness.With the increase of cutting force amplitude,the machining stability of the system decreases.When the amplitude of cutting force changes in the initial stage,the influence of cutting force amplitude on the limit cutting depth changes greatly.When it increases to a certain extent,the change trend of the limit cutting depth becomes gentle;the influence of speed and damping coefficient on the system processing The higher the speed or the greater the damping coefficient,the greater the limit cutting depth and the better machining stability of the system;the number of teeth and cutting force coefficient have similar effects on the stability of the system,and the more teeth or the larger the cutting force coefficient,the weaker the machining stability of the system. |
