Research On The Compensation Technology Of The Space Error Of The Precision CNC Machine Tool

High precision CNC machine tool is an essential tool for advanced industrial manufacture,and it is an important symbol of a country's manufacturing level and overall national strength.There are many factors that affect the accuracy of precision CNC machine tools,of which the proportion of thermal error is 40~70%,so it is very important to reduce the influence of thermal error on machining precision of high precision CNC machine tools.After discovery of the research status at home and abroad,it found that most researches are in accordance with the international standard "test code for machine tools--Part third: Determination of thermal effects"(ISO 230-3:2007),the thermal characteristics of CNC machine tools are characterized by the thermal deformation of the machine tool spindle and the worktable specific single position,and the model and compensation are established according to the temperature value measured by temperature sensor placed on CNC machine tools and the thermal error of the fixed position of the work table.To solve the influence of the space thermal error on the machining accuracy of CNC machine,caused by flatness error of worktable and uneven temperature rising of machine parts,this paper puts forward a method of thermal error compensation for the whole space machine,Through the experimental study on the Leaderway V-450 numerical control machine tool,the machining accuracy was greatly improved greatly improving the compensation effect.The main contents of this paper are as follows:1)A measurement system based on line detection is designed,which can accomplish the collection of the temperature information and the thermal error of the whole space of CNC machine worktable during the CNC machine idle experiment,the measured data is analyzed and verified the defect of the thermal error modeling and compensation scheme for fixed table single point.2)the modeling and compensation scheme of the thermal error of the whole worktable space is put forward: combine fuzzy clustering with gray correlation to select temperature sensitive point in the process of modeling,and establish the multivariate linear regression model of the 15 measure points,then establish the least square surface thermal error model for each temperature time according to the compensation of the temperature value.3)the traditional thermal error compensation scheme is improved: first embed the modeling method and procedure of thermal error compensation model of the whole worktable space into the compensator,then calculate the compensation value of the position combined with the temperature of temperature sensitive points and the realtime coordinates of machine tools(x,y),the online compensation of Z axial direction error of the whole work space can be realized through the origin offset function of numerical control system.4)Through the verification experiment,the compensation effect of the thermal error modeling method of the whole workable space is compared with that of the traditional one.The result shows that the prediction effect of the spatial compensation model for machine working table is better than that of the single-point thermal error compensation model: the standard deviation is reduced by 45%,and the compensation accuracy of single maximum residual error is improved by up to 50%.