Study On The Technology Of Hot Heavy Forging Dimension Measurement

Heavy forging is the critical component of important equipment and the significant basis for the country development and the national economic construction. To update the overall level and capacity of China's heavy forging manufacturing technology has important social meaning and commercial values. The exterior size and inner quality of heavy forging can be guaranteed by online measurement. With the support of National Key Basic Research and Development Scheme, a comprehensive and exploratory research on the key technology of heavy forging dimension measurement is carried out to improve the forging quality. The paper's work touches upon several points as follows:1. The laser range acquisition method is adopted to measure the dimension of heavy forging. The laser range sensor which is driven by a two-DOF parallel mechanism completes quick and stable scan and acquires distance and motor rotation angles information of the points on the forging. These points are converted to the fixed coordinates system, then, imported to the reverse engineering software Geomagic Studio to obtain 3D shape and to execute dimension measurement.2. A CCD camera is mounted on the measuring mechanism to display the scanning position in-time. The relationship between the point on the video image, the angles of the driving motors and the measuring point on the heavy forging was deduced. Then the measuring point is labeled on the video by programming. At the same time in order to select the measuring point randomly, we compare the angles of current point and expected point's position, work out the difference, thus promoting the motors to drive the ranging sensor to the specified point.3. Edge detection arithmetic is used to distinguish the verge of heavy forging. The acquired point clouds are imported to the reverse engineering software to obtain 3D shape, which can be used to measure the dimension and to correct distortion caused during forging and pressing.4. The theoretical model of measuring shaft forging is analyzed. We project the ellipses which are on the oblique sections to the axial cross sections and adopt the least squares technique to fit the axial cross section of the shaft forgings, and then the parameters of the axial section, which include the center coordinates and the radius can be worked out by the model. As for the dimension measurement of other shape forging, we can refer the method introduced in the first part.5. We analyze the cause and influence of measurement error. And the corresponding methods are applied in the measuring process to reduce the measurement error. Experiments are conducted in the laboratory to test the validity and precision of the methods. And the results verified its correctness.The research work of this dissertation laid the foundation of laser range acquisition method used in the production field.