If you want to ensure the positioning accuracy of the NC machine tool, you need to detect it in the following ways.
1. Linear motion positioning accuracy detection
The positioning accuracy of linear motion is generally carried out under the no-load condition of machine tools and worktables. According to the national standards and the provisions of the international organization for Standardization (ISO standard), the detection of CNC machine tools should be based on laser measurement. In the absence of a laser interferometer, for ordinary users, you can also use a standard scale with an optical reading microscope for comparative measurement. However, the accuracy of the measuring instrument must be 1~2 levels higher than the measured accuracy.
In order to reflect all the errors in multiple positioning, the ISO standard stipulates that each positioning point calculates the average value and the dispersion band consisting of the dispersion-3 dispersion band according to the five measured data.
2. Linear motion repeated positioning accuracy detection
The instruments used for testing are the same as those used for testing the positioning accuracy. The general detection method is to measure at any three positions near the midpoint and both ends of each coordinate stroke. Each position is positioned by rapid movement, and the positioning is repeated for 7 times under the same conditions. The stop position value is measured and the maximum difference of readings is calculated. One half of the largest difference among the three positions is attached with positive and negative symbols as the repeated positioning accuracy of the coordinate, which is the most basic index to reflect the stability of axis motion accuracy.
3. Origin return accuracy detection of linear motion
The accuracy of origin return is essentially the repeated positioning accuracy of a special point on the coordinate axis, so its detection method is completely the same as the repeated positioning accuracy.
4. Reverse error detection of linear motion
The reverse error of linear motion, also known as momentum loss, includes the reverse dead zone of the driving parts on the feed transmission chain of the coordinate axis (such as servo motor, servo hydraulic motor, stepping motor, etc.), and the comprehensive reflection of the errors such as the reverse clearance and elastic deformation of each mechanical motion transmission pair. The larger the error, the lower the positioning accuracy and repeated positioning accuracy.
The detection method of reverse error is to move a distance in the forward or reverse direction in advance within the stroke of the measured coordinate axis and take this stop position as the benchmark, then give a certain movement command value in the same direction to move it for a certain distance, and then move the same distance in the opposite direction to measure the difference between the stop position and the reference position. Carry out multiple measurements (generally 7 times) at the three positions near the midpoint and both ends of the stroke, calculate the average value at each position, and take the maximum value of the average value as the reverse error value.