Study On Axial Static-dynamic Characteristics And Circumferential Motion Stability Of The New Type Hybrid Rotary Table

Large rotary table occupies an important position in machining and manufacturing.As a key part of some lathes and large gear machine tools,the performance of rotary table directly affects the performance of machine tools.The running accuracy and stability of the turntable have a direct influence on the surface roughness and size of the workpiece to be processed.For the existing large turntable in the start or low speed movement of the stability is poor,easy to appear crawling.When the turntable runs for a long time,the temperature of the lubricating oil film rises too high,resulting in the decrease of viscosity and affecting the bearing capacity of the turntable.In the traditional static pressure rotary table structure,adding the spiral groove form of dynamic pressure oil wedge,using the speed difference between the middle plate and the table,so that the rotary table produces enough dynamic pressure bearing capacity,can improve the overall bearing performance of the rotary table.The spiral dynamic pressure oil wedge can accelerate the outflow of lubricating oil and help to reduce the temperature rise of lubricating oil.When the turntable starts,start the middle plate first,so that the worktable starts on the flowing lubricating oil,which can effectively reduce crawling.This paper takes the new rotary table as the research object,establishes the calculation model of oil film force on the rotary table,analyzes the axial and static characteristics of the rotary table,and conducts data acquisition on the c:ircular grating on the table,and analyzes the circumferential stability of the rotary table.The specific work is as follows:Firstly,the structure and working principle of the new rotary table with static and dynamic pressure are briefly introduced,and the Reynolds equation for solving the oil film force in the dynamic pressure zone and the static pressure zone is derived.On the premise of considering the flow balance of the turntable,the oil film force of the turntable is solved by the difference method.Secondly,the experimental turntable set up by the research group was introduced,and the eddy current sensor and pressure sensor for measuring oil film thickness and oil film pressure were emphatically explained.The collected data are analyzed with MATLAB software and compared with the results calculated by the oil film force model established in this paper.The results show that the established oil film force model is reliable.Thirdly,the effects of rotating speed,oil supply pressure and load on the static characteristics of the turntable were analyzed.In addition,the calculation model of the oil film force on the rotary table in the presence of extrusion is derived,and the axial motion model of the workbench is established.The small perturbation method is used to deduce the axial dynamic characteristic coefficient of the turntable.Under the premise of considering the flow balance,the variation law of oil film thickness,bearing capacity,damping coefficient and stiffness coefficient with time when transient load and periodic load are applied to the axial direction of the turntable.Finally,the stability of the new rotary table in circumferential motion is analyzed by experimental study.Through the data acquisition of the grating fixed on the surface of the worktable and concentric with the worktable,the median filter was used to remove noise from the collected data.The actual velocity curve of the worktable was obtained according to the known raster spacing and time information,and the movement information of the worktable was obtained by comparing with the set speed of the worktable.By comparing the relationship between the maximum offset of the rotating speed and the set speed,the influence of the working table rotating speed and the middle plate rotating speed on the movement stability of the working table is analyzed.