Measurement And Control For Oil Film Thickness Of Large Precise Overloading Rotary Table

Static pressure table is widely used in CNC machine tools for its high precision, high load, long life and other advantages, each work performance such as bearing capacity, stiffness and static pressure of table mainly depends on the oil film thickness of hydrostatic guideway. But, the oil film thickness of hydrostatic guideway can not keep stable in the process of work or under the action of external loading, and it affect the carrying capacity of the hydrostatic guideway and oil film stiffness.Therefore there is a very pressing needs for precision overloaded rotary processing field to adjusted stability of oil film thickness, guarantee high precision, high bearing, high stiffness and so on work performance for the workbench.The research for workbench hydraulic system, analyzes the structure characteristics of rotary table, comparative study the open and closed hydrostatic guideway structure hydrostatic guideway structure as well as the advantages and disadvantages, and determine the workbench uses the quantitative closed hydrostatic guideway, design a hydraulic system to adjust the oil film thickness by adjusting the pump flow, choosing the main hydraulic components, in order to realize adjusting for oil film thickness of the workbench.In the aspect of measuring for the oil film thickness, through comprehensive considerating working condition and detection precision, determine the oil film thickness testing instrument is the eddy current displacement sensor, at the same time considering the unbalance loading or the manufacturing error of workbench, puts forward a way of average smoothing filter is used to reduce the error, providing accurate data to adjusting oil film thickness subsequently.Oil film thickness control, due to the oil flow constant, when the table under external load, will cause the change of the oil cavity pressure and the oil film thickness inevitably, in order to ensure the oil film thickness constant and the oil film stiffness tends to infinity, proposed an oil film thickness control scheme in this paper composed of the eddy current displacement sensor, controller, frequency conversion motor, long pump, closed hydrostatic guideway, and establish mathematical model of each part. Under the environment of Matlab/Simulink to simulation. Results show that the the oil film thickness can be stable under the control model, oil film stability has been improved to a great extent. Finally, developed a set of oil film thickness control system in 840 DSL CNC of Siemens, the control model is verified in the test platform, the experimental results show that the oil film thickness can be stable in the design value.