Measuring 3D shape of steel shafts during forging
IMEGO (Gøteborg), Mefos (Luleå) and SINTEF in 2005 collaborated in a feasibility study for 3 Swedish steel companies on how the 3D shape of steel shafts can be measured by means of computer vision. The cross section shape and the longitudinal curvature were to be measured during the forging process in order to be able to better control the forging.
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The cross section shape measured at a specific point of the shaft. |
A blue laser was used to project a laser plane onto the shaft. By fitting a video camera with a matching narrow band filter, a good contrast image was obtained even when the steel was glowing at 1200 ºC. The video camera viewed the projected laser stripe from an angle, and by proper calibration and triangulation techniques around two-third of the cross section shape could be obtained from each image. By taking several overlapping images, as the shaft was rotated, a full cross section profile could be obtained.
The longitudinal curvature was measured by merging several overlapping images of the shaft seen from two sides. Finally the two sets of information were joined to create a full 3D model from where the deviations from the desired target shape could be computed at any point.
The project was sponsored by Scana Steel Björneborg AB, Uddeholm Tooling AB, Sandvik Materials Technology AB, VINNOVA (Swedish Governmental Agency for Innovation Systems) and the Nordic Innovation Centre.
If you are interested in more information please contact
Tom Kavli
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Forging of a steel shaft at Scana Steel Björneborg AB. |
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The final measured 3D geometry with deviations from the desired shape encoded with colors. |
