Laser Bending of Stainless Steel Sheet Metals

Laser forming is an innovative technology that uses a laser beam to form sheet metal by thermal stresses and is well suited for short production runs, eliminating the need for expensive dies and reducing the cycle time. High power diode lasers have entered the industrial manufacturing area, because of their unique features (small size and low weight), high efficiency and reliability; nowadays, diode lasers have gained high interests as new sources for material processing. Many industrial applications are possible, from brazing to cladding and hardening. As a consequence of the rather poor beam quality, applications as cutting and high speed deep penetration welding are not yet possible, but laser forming can be effectively performed. Due to its low specific power, diode laser bending can be performed under focalization conditions, contrary to the other laser sources (such as CO2 laser). In this study, a high power diode laser was used to form AISI 304 sheet metals. This laser had a rectangular spot that was focused on the specimen to bend; the short side of the spot was aligned with the laser scan direction. The laser power ranged from 100 to 300 W (with an increment of 50 W); two scan rates were used, 4 and 8 mm/s, and the number of passes was 2, 4 or 6. At lower values of laser power the bending angle tends to be negligible; at higher values material melting occurs, and, as a consequence, process effectiveness falls down. In the experimentation, the values of bending angle, microstructure and residual stresses of the stainless steel sheet metal laser bent were analyzed with regard to the input variables.