Granite components are widely used in the field of precision manufacturing, flatness as a key index, directly affect its performance and product quality. The following is a detailed introduction to the method, equipment and process of detecting the flatness of granite components.
I. Detection methods
1. Flat crystal interference method: suitable for high-precision granite component flatness detection, such as optical instrument base, ultra-precision measurement platform, etc. The flat crystal (optical glass element with very high flatness) is closely attached to the granite component to be inspected on the plane, using the principle of light wave interference, when the light passes through the flat crystal and the surface of the granite component to form interference stripes. If the plane of the member is perfectly flat, the interference fringes are parallel straight lines with equal spacing; If the plane is concave and convex, the fringe will bend and deform. According to the bending degree and spacing of the fringes, the flatness error is calculated by the formula. The accuracy can be up to nanometers, and the small plane deviation can be accurately detected.
2. Electronic level measuring method: often used in large granite components, such as machine tool bed, large gantry processing platform, etc. The electronic level is placed on the surface of the granite component to select the measuring point and move along the specific measuring path. The electronic level measures the change of the Angle between itself and the gravity direction in real time through the internal sensor and converts it into the levelness deviation data. When measuring, it is necessary to construct a measuring grid, select measuring points at a certain distance in the X and Y directions, and record the data of each point. Through the analysis of data processing software, the surface flatness of granite components can be fitted, and the measurement accuracy can reach micron level, which can meet the needs of large-scale component flatness detection in most industrial scenes.
3. CMM detection method: comprehensive flatness detection can be carried out on complex shape granite components, such as granite substrate for special-shaped molds. The CMM moves in the three-dimensional space through the probe and touches the surface of the granite component to obtain the coordinates of the measuring points. The measuring points are evenly distributed on the component plane, and the measuring lattice is constructed. The device automatically collects coordinate data of each point. The use of professional measurement software, according to coordinate data to calculate the flatness error, not only can detect the flatness, but also can obtain component size, shape and position tolerance and other multi-dimensional information, measurement accuracy according to the equipment accuracy is different, generally between a few microns to tens of microns, high flexibility, suitable for a variety of types of granite component detection.
II. Preparation of testing equipment
1. High-precision flat crystal: Select the corresponding precision flat crystal according to the detection accuracy requirements of granite components, such as the detection of nanoscale flatness needs to choose a super-precision flat crystal with a flatness error within a few nanometers, and the flat crystal diameter should be slightly larger than the minimum size of the granite component to be inspected, to ensure complete coverage of the detection area.
2. Electronic level: Select an electronic level whose measurement accuracy meets the detection needs, such as an electronic level with a measurement accuracy of 0.001mm/m, which is suitable for high-precision detection. At the same time, a matching magnetic table base is prepared to facilitate the electronic level firmly adsorb on the surface of the granite component, as well as data acquisition cables and computer data acquisition software, to achieve real-time recording and processing of measurement data.
3. Coordinate measuring instrument: According to the size of granite components, shape complexity to choose the appropriate size of the coordinate measuring instrument. Large components require large stroke gauges, while complex shapes require equipment with high-precision probes and powerful measurement software. Before detection, the CMM is calibrated to ensure the probe accuracy and coordinate positioning accuracy.
III. Testing process
1. Flat crystal interferometry process:
◦ Clean the surface of granite components to be inspected and the flat crystal surface, wipe with anhydrous ethanol to remove dust, oil and other impurities, to ensure that the two fit tightly without gap.
Place the flat crystal slowly on the surface of the granite member, and press lightly to make the two fully contact to avoid bubbles or tilting.
◦ In a darkroom environment, a monochromatic light source (such as a sodium lamp) is used to illuminate the flat crystal vertically, observe the interference fringes from above, and record the shape, direction and degree of curvature of the fringes.
◦ Based on the interference fringe data, calculate the flatness error using the relevant formula, and compare it with the flatness tolerance requirements of the component to determine whether it is qualified.
2. Electronic level measurement process:
◦ A measuring grid is drawn on the surface of the granite component to determine the location of the measuring point, and the spacing of the adjacent measuring points is set reasonably according to the size and accuracy requirements of the component, generally 50-200mm.
◦ Install an electronic level on a magnetic table base and attach it to the start point of the measuring grid. Start the electronic level and record the initial levelness after the data becomes stable.
◦ Move the electronic level point by point along the measuring path and record the levelness data at each measuring point until all measuring points are measured.
◦ Import the measured data into the data processing software, use the least square method and other algorithms to fit the flatness, generate the flatness error report, and evaluate whether the flatness of the component is up to standard.
3. Detection process of CMM:
◦ Place the granite component on the CMM work table and use the fixture to firmly fix it to ensure that the component does not displace during the measurement.
◦ According to the shape and size of the component, the measurement path is planned in the measurement software to determine the distribution of measurement points, ensuring full coverage of the plane to be inspected and uniform distribution of measurement points.
◦ Start the CMM, move the probe according to the planned path, contact the granite component surface measurement points, and automatically collect the coordinate data of each point.
◦ After the measurement is completed, the measurement software analyzes and processes the collected coordinate data, calculates the flatness error, generates a test report, and determines whether the flatness of the component meets the standard.
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Post time: Mar-28-2025