What is the content of linear motion positioning accuracy detection for CNC lathes?
What is the content of linear motion positioning accuracy detection for CNC lathes?
The positioning accuracy of the CNC lathe refers to the positional accuracy that can be achieved by the movement of each coordinate axis of the machine tool under the control of the numerical control device. The positioning accuracy of the CNC lathe can be understood as the motion accuracy of the machine tool. The following mainly introduces the linear motion positioning accuracy of the CNC lathe:
1. Linear motion positioning accuracy detection
Linear motion positioning accuracy is generally performed under no-load conditions on machine tools and benches. According to the national standards and the provisions of the International Organization for Standardization (ISO standards), the detection of CNC machine tools should be based on laser measurements. In the absence of a laser interferometer, it is also possible for a general user to use a standard scale with an optical reading microscope for comparative measurements. However, the accuracy of the measuring instrument must be one to two levels higher than the accuracy of the measurement.
In order to reflect all the errors in the multiple positioning, the ISO standard stipulates that each positioning point is calculated by five measurement data and the dispersion difference band of the dispersion--3 dispersion band is used.
2, linear motion repeat positioning accuracy detection
The instrument used for the test is the same as that used to detect the positioning accuracy. The general detection method is to measure at any three positions near the midpoint and the two ends of each coordinate stroke. Each position is quickly moved, and the positioning is repeated 7 times under the same conditions. The stop position value is measured and the maximum reading difference is obtained. . Taking one-half of the largest difference among the three positions, the positive and negative signs are attached as the repeated positioning accuracy of the coordinates, which is the most basic index reflecting the stability of the axis motion accuracy.
3, linear motion return accuracy detection
The origin return accuracy is essentially the repeatability of a particular point on the coordinate axis, so its detection method is exactly the same as the repeat positioning accuracy.
4. Reverse error detection of linear motion
The reverse error of the linear motion, also called the loss amount, includes the reverse dead zone of the drive position (such as servo motor, servo motor and stepping motor) on the coordinate axis feed chain, and each mechanical motion transmission pair A comprehensive reflection of errors such as backlash and elastic deformation. The larger the error, the lower the positioning accuracy and the repeat positioning accuracy.
The detection method of the reverse error is to move a distance forward or backward in the stroke of the measured coordinate axis and use the stop position as a reference, and then give a certain movement command value in the same direction to make it move a distance. Then move the same distance in the opposite direction and measure the difference between the stop position and the reference position. The measurement is performed a plurality of times (generally 7 times) at three points near the midpoint and both ends of the stroke, and the average value at each position is obtained, and the maximum value among the obtained average values is the reverse error value.
