How to measure back-lash and three-dimensional length error of spindle position of one CNC machine tool

摘要

The present invention relates to a method for measuring the back-lash and three-dimensional length error of the spindle position of a Computerize Numerical Control (MNC) machine tool using a ball link. It is an object of the present invention to provide a method for accurately measuring a three-dimensional position error of a spindle as well as a back-lash error that greatly affects a position error of a machine spindle.;The present invention comprises the steps of preparing a ball-link provided with two cups (Cup) in contact with the ball, an electric micrometer (LVDT) for measuring the length, and a connecting tube; Preparing a calibration die having two balls at a predetermined distance, and measuring a distance between the ball centers to obtain a calibration distance L; Inserting the ball-link between the ball and the ball of the calibration die to set a reference length of the ball-link; Installing ball bars on the table and the spindle of the machine tool for which the error is to be measured; Inserting a ball-link having a reference length set as described above into the ball of the ball bar; In the hemisphere centered on the ball on the cable, the space length L ₁ ′ for several points on the hemisphere is moved by a ball-link while moving the spindle such that the length between the centers of the two balls is equal to the calibration distance L. Measuring; Measuring the space length L ₂ ′ for each hemispherical point by ball-link while moving the spindle in a direction opposite to the movement direction; Obtaining a back-leash error (B) as shown in Equation (1) using the same measured space lengths (L ₁ ′) and (L ₂ ′);;B = L ₁ '-L ₂ ' (1);Obtaining an average space length (L ') of the measured space lengths (L ₁ ') and (L ₂ ') as described above; And calculating a three-dimensional length error (dL) by comparing the average space length (L ') and the calibration distance (L), and measuring the back-lash and three-dimensional length error of the spindle position of the CNC machine tool. That's the point.