Since machine tool rotation errors may cause geometric errors of the spindle drive system, drive shaft eccentricity, inertial force deformation, thermal deformation, etc., as well as many random errors, the detection of the rotation accuracy of all machine tool spindles has become one of the evaluation methods for the dynamic performance of the machine tool. Important indicators. Through the radial runout and axial runout test experiments, the requirements for the measurement of rotation accuracy can be effectively met.
There are several methods to detect the rotation accuracy of the machine tool spindle, such as meter measurement, one-way measurement, and two-way measurement.
Theories and Methods of Measuring Machine Tool Spindle Rotation Accuracy
The rotation accuracy of the machine tool spindle is an important index to measure the performance of the mechanical system, and it is the main factor that affects the working accuracy of the machine tool. The measurement technology of machine tool spindle rotation error plays an important role in the development of precision machinery and equipment. The rotation error of the machine tool spindle includes radial error and axial error. The measurement of the axial rotation error is relatively simple, just install a micro-displacement sensor on the end face of the machine tool spindle to measure the one-dimensional displacement. Therefore, the research focus of machine tool spindle rotation error measurement technology has been focused on the accurate measurement of radial error.
1) Measuring method with a meter
When the rotation accuracy of the machine tool spindle was not high in the early days, the common method to measure the error of the machine tool spindle was to insert a precision mandrel into the taper hole of the machine tool spindle, and measure by placing a dial indicator on the surface and end of the mandrel. This measurement method is simple and easy to implement, but it will introduce the eccentricity error of the taper hole, which cannot distinguish the errors of different nature, and it cannot reflect the rotation error of the spindle at the working speed, and it cannot be used for high-speed and high-precision spindle rotation. Accuracy measurement. In addition, measurement test pieces are also used to evaluate the rotation error of the spindle.
2) One-way measurement method
One-way measurement method is also called single sensor measurement method. The error signal of the "sensitive direction" picked up by the sensor, after being amplified and processed by the micrometer, is sent to the recorder for further data processing. Then take the rotation angle of the main shaft as an independent variable, and expand and superimpose the collected displacement on the base circle according to the rotation angle of the main shaft to form a circle image. The sensitive direction of the error motion is through the instantaneous contact point of the processing or test and is parallel to the normal direction of the ideally processed surface of the workpiece, and the non-sensitive direction is on a straight line perpendicular to the third direction. The spindle rotation error motion measured by the one-way measurement method is essentially just the component of the one-dimensional spindle rotation error motion in the sensitive direction. Therefore, the one-way measurement method is only suitable for the measurement of the rotation accuracy of the spindle with sensitive directions, such as the workpiece turning machine tool. Lathe is a typical representative of workpiece turning machine tool. This measurement method is also inevitably mixed with the shape error of the spindle or the standard ball. When the rotation accuracy of the machine tool spindle is not too high and the mixed shape error can be ignored, the outside of the circle image of the rotation accuracy of the lathe spindle obtained by the one-way measurement method The edge profile is very similar to the outer edge of the workpiece, so the circle image obtained in this way can be used to evaluate the machining accuracy and machining quality of the lathe spindle.
3) Two-way measurement method
The rotation error motion of the spindle is a two-dimensional plane motion. It requires at least two sensors to collect data at the same time on the two vertical sides of the machine spindle cross section, and then combine the two sets of displacement data to reproduce the actual rotation error trajectory of the spindle. So it is called the two-way measurement method, also called the dual sensor measurement method. The traditional two-way measurement method ignores the shape error of the machine tool spindle or the standard ball, and also mixes the eccentric error, which affects the accuracy of the measurement result.
Post time: Nov-23-2021