Henning Hanebuth

Influence of the heat input position on bending and torsion of SS304 and DC01 strips

Laser beam bending was invented more than one decade ago, but just a few applications have been found and were realized in manufacturing processes. With regard to the minimization of new products and increasing demands concerning tolerances there was a fall back on laser beam bending in recent time. However, several basic investigations for the understanding of the bending mechanism and to find the limits of the process have been carried out before. Still there is a lack of continuous and subsequent investigations which discover general knowledge to allow and simplify the step from experimental state into manufacturing line. In this context first questions are the influence of the geometry, the heat input position and the pre-treatment of the material. Smallest bending angles but largest torsion angles have been found for the laser beam treatment with scans across the whole width at the smallest specimen. When the bending angles increase with the width, the torsion angles decrease. Concerning the heat input position largest bending angles can be achieved with a laser beam manipulation (pulse or scan) in the middle of a metal strip. To obtain greatest bending angles several scans across the specimen should be performed one upon the other. Bending angles of more than 90 degree(s) can be produced by this method. A pre-treatment of the material like cold forming or annealing causes different bending angles. Best results concerning large bending angles can be demonstrated for cold formed and not annealed specimen due to the residual stress in the material supporting the bending process. Also a subsequent annealing process causes an additional bending of the specimen for single laser scans but can be avoided by performing a second scan.