A Diode-Laser-System for Laser-Assisted Bending of Brittle Materials

We developed a small and compact system of diode lasers, which can be inserted into the lower tools of a bending press. The parts of the system allow easy plug and play operation and can be installed for any bending length. The diode laser, which is based on 200？W laser bars on microchannel cooler, allows the heating of sheet metals in the forming zone shortly before and during the bending process. There is no unnecessary heating of other parts of the bending equipment, no wear of the tool, and, if properly done, no damage of the surface of the metal. The power per bending length is 16？kW/m. 1. Introduction The production of complex structures out of sheet metals with bending technology is widespread in industry. Alas, this is currently mainly restricted to materials that allow a certain degree of cold forming. Brittle materials, as Mg-, Ti-, or some Al- and steel-alloys are generally avoided or, in some rare cases, heated up as a whole, before the bending operations are performed. Due to fast cooling the initial temperatures must exceed the necessary forming temperatures, such that the whole process becomes very cumbersome. The goal of laser assisted bending, not to be confused with laser-bending [1], is to make bending of brittle materials nearly as simple as cold bending by selective heating of the work piece with a laser source shortly before and during the bending process. Previous work [2] uses a CO2 Laser to heat up bending lengths up to 1？m with a scanner system. Another approach was the use of a diode laser, again with a scanner system [3]. In order to obtain a system for industrial use, we developed a diode laser system based on diode laser bars on microchannel coolers. The system can be installed inside a special tool, which replaces the lower tool of a bending press. The challenge here was that on smallest possible space, a dust-tight solution with optics, power and cooling water supply was to be integrated. Furthermore, the solution should allow any required bending length to be installed. 2. The Laser Source Diode laser bars [4] with an optical power of 200？W and a wavelength of 940？nm are used. The current consumption of one bar is 220？A and the voltage drop is ~2？V. The bars are soldered on microchannel coolers, eight of which fit into a lower tool for 100？mm bending length, which yields an optical power of 16？kW/m. The diode laser rests on the bottom of the lower tool, which consist of two parts. The screws, that fix them, are located above the diode lasers. Figure 1 shows two solutions for guiding the laser radiation around these