Radian laser tracker in five-axis machine tool Application of RTCP in high-precision test

In the five-axis machining center numerical control system, RTCP is considered to be the Rotated Tool Center Point, which is also known as the tool point following function. In five-axis machining, when pursuing the path of the tool point and the attitude between the tool and the workpiece, the additional motion of the tool point will be generated due to the rotary motion, resulting in the inconsistency between the control point of the NC system and the tool point. Therefore, the NC system should automatically correct the control point to ensure that the tool point moves according to the specified path of the command. This technology is also called TCPM, TCPC or RPCP. The detection of five-axis machine tool under RTCP status is to accurately and comprehensively analyze whether the control point is corrected in place and the accuracy of the movement path of the tool point.

Figure 1: RTCP processing of five-axis machine tool

Figure 2: Schematic diagram of the ball club tester (left) and rotation tester (right)

When using the ball and stick instrument for testing, fix the two ends of the ball and stick instrument on the machine tool spindle and workbench respectively, measure the circular track formed by the machine tool movement, and compare this track with the standard circular track, and analyze the error amplitude. However, in actual operation, because the ball and rod tester is a mechanical structure, the whole detection process also depends on the characteristics of its structure, so in the detection, especially in the detection of large five-axis machine tools, it is easy to be affected by the problem of insufficient measurement stroke. Even if the extension rod is used, it cannot fully meet the travel requirements for the detection of large five-axis machine tools, Moreover, the excessively long extension rod itself is easy to cause inconvenience.
The use of a rotation detector for detection is similar to the use of a ball and stick instrument. The detection equipment needs to be fixed on the machine tool spindle and workbench respectively. The difference is that the rotation detector uses non-contact sensors for three-dimensional displacement acquisition. However, even for non-contact data acquisition, it is still necessary to probe the ball head into the ball socket embedded with three sensors, and carry out the measurement operation at a distance. In actual measurement, it is still unable to meet the data acquisition requirements of large travel, and due to its own structure and working mode characteristics, the measurement angle range is limited.
API solution
In view of the characteristics, detection requirements and deficiencies of existing detection methods of medium and large five-axis machine tools, API has developed a set of solutions, using Radian Laser Tracker and high-precision target ball, which can be used for RTCP performance detection of various medium and large gantry, cantilever and other five-axis machine tools. On the basis of ensuring the detection accuracy and efficiency, it has successfully avoided the impact of the structure, stroke The limitations caused by the lack of angle and other aspects have truly realized the detection method of "free travel" and "free angle".

Figure 3: Radian laser tracker five-axis machine tool RTCP test operation

4. Evaluate the accuracy of the machine tool according to the measured data.

Figure 4: Analysis of dynamic tracking detection data of tool point motion path

Characteristics
-It is applicable to dynamic and static detection of various medium and large five-axis machine tools under RTCP status;
-The Radian laser tracker can provide a measuring radius of more than 80 meters, and the knife point can move in a large range and a large range within this range, completely avoiding the problem that the range of travel is limited when using the ball and club instrument and the rotary inspection device to carry out the detection operation, and truly realizing the "freedom of travel";
-Combined with the translational axis movement, the rotating axis can rotate in a large range. The Radian laser tracker can cooperate with the machine tool to achieve the angle measurement range of B angle 360 °, A angle+79 ° to - 59 ° (138 °), further realizing the "angle freedom" in the five-axis machine tool detection operation;
-Radian laser tracker uses laser interferometry (IFM) to measure the length to evaluate the sphericity of the tool tip, with an accuracy of 0.5 μ M/m, and traceable;
-Using the Radian laser tracker, you can implement dynamic tracking detection of the movement path of the tool point (see Figure 4), and also achieve static high-precision detection of the tool point position (see Figure 5).

conclusion
The use of API brand Radian laser tracker can realize the detection of medium and large five-axis machine tools under RTCP status, with high accuracy and speed, and completely avoid the problems caused by the deficiencies of the existing detection methods in structure, measuring stroke, angle range, etc., which is highly applicable to the tracking detection of medium and large five-axis machine tools in the movement path of the tool point or the static high-precision detection of the tool point position.