The Design Of Rotation Axis Error Measurement System For R-test Of Five-axis CNC Machine Tool

With the technological progress,the demand for mechanical components with complex geometric shapes and high accuracy in the modern manufacturing industry is increasing,and the application of five-axis CNC machine tools has also become even more popular.However,the advantages of five-axis CNC machine tools determine that their machine structure and control systems will be more complex.Therefore it will be difficult to improve the machining accuracy of those machine tools.The measurement and compensation technique for the linear axis error of the five-axis CNC machine tool has been very mature,but the rotation axis is difficult to measure due to the complex structure,and the rotary axis geometric error affects the machining more than the linear axis due to the angular positioning error amplification.Therefore,by using the R-test measuring instrument this paper studies the error measurement method of rotating axis which has great influence on the accuracy of five-axis CNC machine tools.According to the technical status of R-test measuring instrument,that R-test measuring instrument has matured abroad while domestic R-test measuring instrument develops slowly,the measuring method of non-contact R-test measuring instrument basing on eddy current displacement sensor is going to be proposed.See the introduction as follows:(1)To analyze the structure of the contact and non-contact R-test measuring instrument and the advantages and disadvantages of these two measuring instruments basing on the sensors used in these two measuring instruments.At the same time,the structural parameters of the R-test measuring instrument with a specific structure of the sensor will be analyzed and optimized.The method takes the maximum measuring space of the measuring instrument and the maximum measurement sensitivity into account.Through those indexes,the optimal angle of sensor installation elevation could be optimized.(2)A calculation method of spherical center coordinates by non-contact R-test measuring with eddy current displacement sensor will be proposed,and on the basis of the influence of the measuring device's machining error on the calculation accuracy,an improved method will also be proposed.To guarantee the accuracy of the calculation results,genetic algorithm will be used.At the same time,according to the problem that the measurement instrument's own measurement coordinate system and the machine tool coordinate system may not be parallel during the actual measurement,the coordinate conversion algorithm between those two coordinate systems will be proposed.Combine those algorithm and method to calculate,we could obtain the accurate spatial position error of the spindle tip when the RTCP function of machine is open.(3)To analyze the selection method of the sensor when the eddy current sensor measures the spherical surface,which is related to the effect from the displacement perpendicular to the sensor's sensitive direction on the measurement result.At the same time,the calibrating method of the measuring characteristic when the eddy current sensor measures the sphere will be proposed.This method acquires certain density data sets of the sensor measuring process through the actual measurement of the working condition of the sensor.By the data fitting method,we could get the measuring characteristic equation of the actual measurement of the working condition.(4)Aiming at the problems that the processing and assembly errors of the R-test measuring instrument base and structure parts will influence the measuring accuracy of the measuring instrument,this paper proposes a calibrating method with R-test measuring instrument for measuring the end face of the sensor.Through the calibration of the measuring plane and the calculation method of the spherical coordinate of the measuring instrument under the calibration of the measuring instrument,the measurement accuracy of the measuring instrument can be ensured while the manufacturing and assembly requirements of the measuring instrument can be reduced.To ensure the accuracy of the calculation process,the calibration method uses genetic algorithm to calculate as same as the spherical center coordinate calculation method.(5)Basing on the research content of this paper,we will choose the appropriate sensor,develop a non-contact R-test measuring instrument software and hardware system,and verify the feasibility of the theory of this paper through experiments.