Research On Embedded Measurement Method Of Spindle Rotation Error

Spindles are important components in the field of machining and measurement,and widely used in manufacture equipment,such as CNC and industrial robot.Due to the errors of design,manufacture and assembly,spindles have inherent geometric errors in six degrees of freedom.At present,the measurement methods of spindles errors mainly include methods of one-way and the two-way,and some methods for errors separation,such as multi-point method,multi-step method and inversion method.The methods of one-way and the two-way require standard balls in the measurement,and the installation and manufacturing errors of the standard ball can affect measurement accuracy.The methods for errors separation have some disadvantages,such as complicated operation or calculation.In addition,most of the existing measurement methods of spindle rotation error are off-line measurement,however,in practice,due to the influence of external force changes,the rotation error and off-line measurement error are not completely consistent.Therefore,it is necessary to propose a method that does not depend on the standard and can be embedded inside the spindle system to realize on-line measurement of the spindle rotation error.Based on the analysis of the existing measurement methods for spindle rotation errors,in this paper,an embedded measurement method for real-time measurement of two radial and three angular motion errors of a rotary stage is proposed,which makes use of a uniform four-scanning-head circular encoder to measure the rotation angle of the spindle and the two radial motion errors of the circular grating,and a miniature laser autocollimator to measure the two yaw angle errors of the plane mirror.By calibrating the assembly error of the circular grating and the plane mirror in advance,the radial motion error and the yaw angle error of the spindle in two directions can be separated from the measurement results.In order to verify the feasibility and accuracy of the method,a spindle with rotation error measurement function was built in this paper.The spindle rotation error measurement program was designed with modular programming ideas,which can realize spindle angular position judgment,data automatic acquisition,measurement result display,data storage and other functions.Finally,a comparison experiment of spindle rotation error measurement is carried out on the turntable by using one-way method and the method proposed in this paper.As the radial rotation error of the spindle is about ±20 ?m,the radial motion errors of the stage were measured and calibrated with LVDTs,and the residual error was less than ±2 ?m.When intermittent external forces were applied to the stage,the change of the stage's motion error can also be monitored accurately.In general,the embedded spindle rotation error method proposed in this paper can be conveniently installed inside the precision spindle and used to monitor the motion error of the rotary stage in real-time.In the future,according to the measured real-time data,the machining error and the precision measurement error caused by the spindle rotation error can be effectively compensated.