Analysis And Compensation Of The Positioning Error Of CNC Milling Machine

Components processed by CNC milling machines have high-precision structure and high-quality surface,but one of the key point to determine the processing accuracy of products is the positional accuracy.Decreasing the position error of CNC milling machine mainly include two parts,error detection and error compensation,however,error detection,as a premise of error compensation,determines the result of final error compensation through its measurement reliability.In consideration of multi-factor affecting the detection precision of position error,this thesis conducts error compensation on a basis of detecting the position error of MVC850 B CNC milling machine by using Laser XL-30 interferometer.Its main idea is as follows:(1)The detection principle and measurement steps of positioning error are introduced.Each type's main factors are found through further analysis of reverse gap,displacement error and repeated positioning accuracy,especially the compartment analysis of displacement error,which studies the wear conditions over the two periods within X and Y axial distance,and finally tests the validity of quantitative analysis of error by comparing the error of CNC milling machine now and its error in one year before.(2)the value calculated by Edlen empirical formula and the actual measured value are compared,and then the affect of environmental parameter(including temperature,air pressure and humidity)on measuring error is analyzed.Later,feed speed,measured spacing,processing time are seen as independent variable factor,and reverse gap,position error are seen as the corresponding result.The degree of different factors affecting measurement result are found through range analysis.The reliability of error detection and the retentivity of CNC milling machine kinematic accuracy are found by analyzing the measuring results and the probability distribution curve of position error.(3)The position error of CNC milling machine is compensated by using comprehensive error compensation which is based on coordinate deviation function.Numerical control programs are produced in line with the fixed point and rectilinear motion of CNC milling machine,and amendments in them are based on previous error measure data.(4)Two blocks of 200×200×20mm aluminum blocks are processed by CNC milling machine through uncompensated and compensated NC programs,and then the effect of positioning error compensation are verified by comparing the fixed point and rectilinear error of the two processed blocks.Test results show that the positioning accuracy of the CNC milling machine has been significantly improved after compensation.To sum up,this paper mainly conducts quantitative analysis on position error of CNC milling machine and reliability analysis on error measurement,and finally verifies compensation effect through processing tests and error compensation based on metrical data of position error.