Precision Testing And Analysis On Precise Bearings Of Machine Tool

With the development of machinery manufacturing technology,the requirements for bearing accuracy are getting higher and higher.The manufacturing error of the bearing in the production process is inevitably present.Reasonable bearing testing and evaluation methods are the focus of research on bearing accuracy.The outer ring of the bearing studied in this paper is fixed and the inner ring rotates.For the inner ring in the bearing,the ideal motion is a single-degree-of-freedom rotary motion.However,the real motion is a complex spatial six-degrees-of-freedom motion that is dominated by radial rotation.This paper studies the test and evaluation of six-degree-of-freedom motion of bearing.It provides a theoretical basis for accurate analysis of bearing rotation accuracy and optimization of bearing testing methods.It has practical value.The main research content is as follows:(1)In this paper,the inner ring of the bearing is regarded as a rigid body.Through the homogeneous transformation of the coordinates,the space motion of the actual bearing is converted into the space motion of the rigid body.Then the contact between the bearing motion data of the six degrees of freedom and the error motion test data of the bearing are obtained.Based on the relational equations,the seven-point method of spatial error measurement is proposed to achieve six-degree-of-freedom motion of bearing.(2)The invariants of discrete motion geometry movements.The dispersed kinematic geometrical model for evaluating bearing is set up.The relationship between the bearing motion and the linear motion trajectory on the bearing inner ring is discussed and the linear discrete trajectory is descripted by spherical image curve and striction curve.According to the discrete kinematic geometry,the bearing accuracy is evaluated by using by spherical image curve and striction curve.Four invariants are used as evaluation indicators: spherical image curve error,striction curve error,minimal spherical image curve error and minimal striction curve error.(3)Based on the seven-point method of spatial error measurement,a test bench of measuring bearing accuracy is designed and an experimental scheme was formulated.The seven-point method obtains the radial error motion trajectory of the measured section,bearing angular error,and axial error motion trajectory of the bearing through the separation of the surface shape error and eccentricity of the measured rotary axis.Finally,the six-degree-of-freedom error motion of the bearing is obtained.(4)According to the experimental data,the spherical image curve and the striction curve of the discrete trajectory of a specific reference line are obtained.Then the spherical image curve error and the striction curve error of all the linear discrete trajectories on the inner ring of the bearing are obtioned.The pherical image curve error surface and the striction curve error surface are obtioned.According to the extreme characteristics of the error surface,the approximate rotation axis of the bearing rotation is found,and the precision of bearing is evaluated.by using discrete kinemactic invariants.Comparing the invariant evaluation with the bearing runout.It is proved that the bearing runout has certain randomness,and the evaluation result is affected by factors such as the position and direction of the sensor measurement,which makes it difficult to objectively evaluate bearing.The invariant evaluation results are irrelevant with the sensor arrangement,so it is very necessary toevaluate bearing by useing invariants.