1. Reliable operation, little influence by temperature and humidity, can maintain accuracy for a long time; Strong anti-interference ability, can resist all kinds of electromagnetic interference.
2. Satisfy the requirements of machine tool accuracy and speed. Under the limit conditions of machine tool performance parts moving range and displacement speed, the testing equipment should achieve certain detection accuracy and small cumulative errors.
3. Convenient for equipment and protection, accustomed to machine working environment. Measurement system equipment requirements have a certain equipment accuracy, equipment accuracy should be reasonable, because by the use of the environment, the entire measurement system requires a better dust, oil mist, chip and other methods.
4. Low cost, long life.
CNC servo system has a azimuth detection system, which is mainly to detect the displacement, and the detected response signal and the CNC equipment announced the command signal compared, if there is an error, the control performance parts to eliminate the direction of the error, and then constitute the closed-loop or semi-closed-loop control of the servo system.
In the system of special machine for servo gate valve, there will also be such a device, but different special machine for servo gate valves have different roles, but they have some common similarities.
for special machine for servo gate valvespecial machine for servo gate valve's requirements for position detection equipment, in addition to the above knowledge or other knowledge is also very important, and it is also the focus of our grasp!
The movement of the moving parts of the machine tool is completed under the control of the numerical control device, and the accuracy of the moving parts under the control of the program instructions directly reflects the accuracy of the machined parts, so the positioning accuracy is a very important detection content.
1, linear motion positioning accuracy detection
The positioning accuracy of linear motion is generally carried out under no-load conditions of machine tools and worktables. According to national standards and the provisions of the International Organization for Standardization (ISO standard), the detection of CNC machine tools should be subject to laser measurement. In the absence of a laser interferometer, a standard scale can also be used for comparison measurements with an optical reading microscope for the average user. However, the accuracy of the measuring instrument must be 1 to 2 grades higher than the accuracy being measured.
In order to reflect all the errors in multiple positioning, the ISO standard stipulates that each anchor point is calculated according to the average value of five measurement data and the dispersion band, which is composed of the dispersion band.
2, linear motion repeated positioning accuracy detection
The instruments used for testing are the same as those used for testing positioning accuracy. The general detection method is to measure any three positions near the midpoint and both ends of each coordinate stroke, each position is positioned with rapid movement, and the positioning is repeated 7 times under the same conditions to measure the stop position value and find the maximum difference in reading. One half of the maximum difference of the three positions is attached with positive and negative symbols as the repeated positioning accuracy of the coordinate, which is the most basic index reflecting the stability of the shaft motion accuracy.
3, linear motion of the origin return accuracy detection
The accuracy of the origin return is essentially the repeated positioning accuracy of a special point on the axis, so its detection method is exactly the same as the repeated positioning accuracy.
4. Reverse error detection of linear motion
The reverse error of linear motion is also called loss of momentum, which includes the reverse dead zone of the drive part (such as servo motor, hydraulic motor and stepping motor, etc.) on the feed transmission chain of the coordinate axis, and the comprehensive reflection of 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 forward or reverse in advance and take the stop position as the basis within the stroke of the measured axis, and then give a certain move instruction value in the same direction to move a distance, and then move the same distance in the opposite direction to measure the difference between the stop position and the reference position. The three positions near the midpoint and both ends of the stroke are measured several times (generally 7 times), and the average value of each position is obtained, and the maximum value of the average value is the reverse error value.
5, rotary table positioning accuracy detection
Measuring tools include standard turntable, Angle polyhedron, circular grating and parallel optical tube (collimator), which can be selected according to the specific situation. The measurement method is to make the workbench forward (or reverse) to turn an Angle and stop, lock, positioning, this position as the benchmark, and then quickly rotate the workbench in the same direction, every 30 locked positioning, measurement. The maximum difference between the actual rotation Angle and the theoretical value (instruction value) of each positioning position is the indexing error. If it is a CNC rotary table, it should take every 30 as a target position, for each target position from the positive and reverse directions for rapid positioning 7 times, the actual difference between the position and the target position is the position deviation, and then calculate the average position deviation and standard deviation according to the GB10931-89 "digital control machine position accuracy evaluation method". The difference between the maximum value of all the average position deviation and the standard deviation and the minimum value of all the average position deviation and the standard deviation is the positioning accuracy error of the CNC rotary table.
Considering the requirements of dry transformers to actual use, it is generally important to measure several right Angle equinpoints such as 0, 90, 180, 270, and so on, and the accuracy of these points is required to improve a level compared with other Angle positions.
6, rotary table repeated indexing accuracy detection
The measurement method is to select three positions within a week of the rotary table and repeat the positioning 3 times, respectively under the direction of positive and reverse rotation for detection. The maximum indexing accuracy of the difference between all reading values and the theoretical value of the corresponding position. If it is a CNC rotary table, it is necessary to take a measurement point every 30 as the target position, respectively, the target position from the positive and reverse directions for 5 times rapid positioning, measured the actual location and the difference between the target position, that is, the position deviation, and then according to the GB10931-89 method to calculate the standard deviation, the maximum standard deviation of each measurement point is 6 times. It is the repeated indexing accuracy of CNC rotary table.
7, the origin of the rotary table return accuracy detection
The measurement method is to perform an origin reversion from 7 arbitrary positions, determine the stop position, and take the maximum difference read out as the origin reversion precision.
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