Application of radian laser tracker in 3D dynamic detection of large machine tools

It is suitable for large multi axis machining center

In the process of production and processing, large 5-axis and 6-axis machine tools may produce errors due to various factors, so that the processed products can not meet the expected accuracy requirements. In the process of adjusting the machine tool, finding out and eliminating these errors, the evaluation of dynamic 3D spatial error is very important; Compared with the traditional 21 item static error detection, 3D spatial error needs to be measured with high precision under dynamic conditions, so it is difficult to implement using traditional detection methods.

Detection of dynamic 3D accuracy & API solution

The traditional 21 item error measurement method of machine tool is to measure each axis (x, y and z) of machine tool with Laser Interferometer, so as to obtain the linear error, angle error and rotation angle error with machine tool turntable (measured with interferometer and polyhedral prism), but the evaluation of these measurements is a single error obtained under static conditions, It can not reflect the 3D spatial position error of the tool position of the 5-axis machine tool in the linkage process.

If the Laser Tracker is combined with the ordinary SMR reflection target ball to measure the spatial position of the 5-axis machine tool, although the 3D spatial position data is obtained, due to the limited angle of the light receiving port of the ordinary SMR target ball, it can only obtain the static 3D spatial position data, so it is only limited to the static measurement.

In order to break through the problem of dynamic 3D spatial position accuracy measurement of large 5-axis and 6-axis machine tools, API company has developed the 3D point dynamic measurement target - activetarget active target (as shown in the figure above, hereinafter referred to as at active target). The working principle of the at moving target is similar to that of the traditional SMR target ball. The Tracker Laser is reflected back to the tracker through the mirror body to complete the spatial position measurement. Its special feature is that the at target has a driving motor in the transverse and longitudinal directions, and has the ability to automatically locate the reflection target, which is equivalent to a motorized SMR.

The advantage of at active target is that no matter where the laser beam is in the space and whether it moves or not, the at active target will always lock the laser beam. Even in rapid and arbitrary movement measurement, it will not lead to "light interruption" with the laser tracker; Therefore, when using the at moving target to detect the moving or rotating target, the continuous measurement of the whole process can be realized automatically without human intervention, and the 3D position coordinates can be collected efficiently under dynamic conditions.

With the advent of at moving target, the dynamic 3D spatial position accuracy measurement of large 5-axis and 6-axis machine tools can be realized.

Requirements and key points of 3D dynamic measurement of 5-axis machine tool

The cutter head of 5-axis machine tool runs dynamically under the planned path, measures the position coordinates of the points under the dynamic running track, and realizes:

1) Compare the measured dynamic point coordinates with the digital analog track of the theoretical operation of the machine tool, and check its spatial error value;

2) After projecting the dynamic trajectory points, the tool space swing angle value at the corresponding point is obtained, and compared with the theoretical value, the dynamic swing angle error is obtained;

3) Project the dynamic track points in the three-phase limit plane to view the dynamic matching performance between axes during operation.
API scheme implementation steps

The implementation steps of measuring dynamic 3D accuracy of multi axis machine tool with radian laser tracker and at moving target are as follows:

① Select a stable and appropriate position, put the tracker in place and start it up;

② Clamp the at movable target column handle to the tool head of the machine tool, start it, and connect it with the tracker laser;

③ The at moving target held at the cutter head moves according to the planned path of the machine tool, and the tracker continuously and real-time collects the points of the moving at target position, so as to obtain the dynamically measured 3D spatial point cloud;

④ Through the projection calculation of the obtained 3D points by software, the required data are obtained to achieve the purpose of detection.

conclusion

To sum up the whole detection process, the whole set of instruments and equipment is easy to arrange and operate. The measurement can be started as long as several simple steps are installed for the radian tracker and at moving target; The whole measurement process is automatic, smooth and without human intervention, which greatly reduces the probability of additional errors; Data analysis is efficient, fast and automatic, which saves time and labor cost and improves production efficiency.