Views: 0 Author: Site Editor Publish Time: 2022-08-08 Origin: Site
The three-coordinate measuring machine is a new type of high-efficiency precision measuring instrument developed in the past 50 years. Its emergence, on the one hand, is due to the high-efficiency processing of automatic machine tools and CNC machine tools, and the processing of more and more complex-shaped parts requires fast and reliable measuring equipment. On the other hand, due to electronic technology, computer technology, digital control technology and the development of precision machining technology provides the technical basis for the generation of CMM.
Because of its strong versatility, large measurement range, high precision, high efficiency and good performance, it can be connected with flexible manufacturing systems, and has become a large-scale precision instrument, so it is called "measurement center".
The geometric measurement is based on the coordinate position of the point, and it is divided into one-dimensional, two-dimensional and three-dimensional measurement. The basic principle of the coordinate measuring machine is to put the measured part into its allowable measurement space, and accurately measure the value of the measured part at the three coordinate positions of X, Y, and Z, and process the computer data according to the values of these points. Fitting to form measurement elements, such as circles, spheres, cylinders, cones, curved surfaces, etc., through mathematical calculations to obtain shape, position tolerance and other geometric data.
At present, using the CONTURA G2 RDS three-coordinate measuring machine, the geometric measurement of flatness is carried out on the surface of the workpiece with multiple slits shown in the figure below.
The preparation of the measurement program utilizes the powerful open offline programming function of the Calypso measurement software. The first advantage of this programming method is that as long as the CAD drawing file designed by the designer is directly input into the measurement software, it can be programmed. It is not necessary to wait for the workpiece to be processed before program measurement can be performed, which can greatly improve work efficiency. The second is that after the programming is completed, you can directly call the program in the CAD environment to perform simulated measurement, verify the program, find out the wrong measurement path and sampling points during the running process, and at the same time correct the program to make the actual measurement The possible problems are minimized, and the safety in the measurement process is guaranteed to the greatest extent.
When programming offline, the measurement software should be set to work in offline mode. First, the model established in advance in the CAD environment is directly imported into the measurement software. The measurement software adopts a graphical visual interface, which is concise and easy to use. It includes basic CAD functions, such as zoom in, zoom out, translation, rotation, coloring (shading) and other functions. The direct CAD interface of the software is suitable for all important CAD functions. CAD format without tolerance issues and loss of accuracy.
The second step is to establish the workpiece coordinate system and start the measurement. The establishment of the coordinate system adopts the common surface line point (3-2-1) method, and then select the plane (Plane) measurement element, double-click the plane element, and set the measurement strategy. Due to the special plane to be tested, there are multiple slits juxtaposed on it, and it is precisely because of this that it is possible that the flatness is out of tolerance. In order to obtain comprehensive, accurate and credible measurement results, the measurement path is selected as a polyline according to the principle of equal division of breadth, so that the collected points cover the entire plane as much as possible. Use the mouse to click the position of the point to be picked on the workpiece model, and the workpiece model will display the location of the point and its vector direction. According to the needs of the measured geometric elements, multiple points can be collected. When the required number of points is collected, then confirm the point in the point collection window, the system will drive the virtual probe to collect points, and fit the geometric elements and graphics to be measured.
The next step is to make detailed settings for the measurement path polyline, including setting the probe speed and the number of points collected according to the actual situation, and then modify the evaluation method of plane elements, set it to the least square method and Select Remove gross errors and click OK.
After the element measurement is completed, the measurement geometric flatness shall be evaluated. In the menu, select Flatness in Shape and Position Tolerance, then double-click the flatness icon, select the measured plane element, and enter the design tolerance value to confirm completion.
Finally, save the completed measurement program, and get the result report of flatness measurement through online actual measurement. The relevant measurement elements and coordinate values and all measurement data can be obtained intuitively from the report. The user can give detailed information such as actual size, tolerance value, deviation from theoretical value, out-of-tolerance situation, etc., and define the report header by himself, which can be recalled at any time after saving.
Through the use of the CMM in the measurement application of the workpiece, a large amount of accurate and detailed measurement data has been collected efficiently, and the functions that cannot be achieved with other workpiece plane measuring tools (such as knife edge ruler, etc.) before are completed. The machine has high precision, high flexibility and excellent digital capabilities. The use of precise CMM in the manufacture of high-quality products can reduce measurement errors, ensure the accuracy and quality of products, meet the needs of design and manufacturing, deepen understanding and better grasp its working principle and performance, and complete and expand equipment. The quality inspection of precision parts in development will definitely play an important role.
