Materialbearbeitung mit 100kW-Lasern - Applikation

Today high power lasers are used in processing of metals for cutting welding and surface treatment (hardening). For such applications mostly lasers with beam powers of 1 kW up to about 10 kW can be found. As laser sources usually CO2 lasers or Nd:YAG lasers are applied. Thereby the realization of lasers with output powers of 100 kW and more is not a technical problem, economically feasible applications, however, have been identified in only few cases up to now. It is therefore one of the aims of this project to find reasonable applications of such lasers and to investigate their performance properties. During the initial phase of the project very soon applications in metal forming technology have been identified as interesting processes for applying high power lasers. In these processes the laser serves as a means for locally heating the workpiece. This class of processes is based upon the fact that the forming properties of a metal improve at increased temperatures, leading to reduced forces and to higher maximum achievable deformations. Investigations were made on laser assisted deep drawing. Deep drawing is one of the most important forming processes for sheet metal, e.g. extensively used in automotive industries. In this process a round sheet first was heated by a laser beam at a certain contour. Afterwards it was quickly transferred to a deep drawing press with glass-covered tools where the forming process took place. The glass cover at the tool surface was developed in the course of this project and was required in order to reduce the heat transfer from the workpiece to the forming tools. It turned out that this kind of treatment is useful for extending the maximum possible deformation which is very interesting when forming materials with poor forming properties (e.g. highly alloyed steels, some Al- and Mg- alloys, titanium, Ni based alloys, etc.). Several requests from industry have shown that there is also commercial interest for this technique. As laser source in this case the CO2 laser is only of minor interest. More important seems to be the high power diode laser, the costs of which currently are strongly reducing. It can be expected that the diode laser soon will be much cheaper than the CO2 laser. In addition diode lasers are very small so that they could directly be integrated into the forming tools. During the project a laser manufacturer expressed already his interest to develop custom diode lasers for such applications Another forming process which has been investigated was laser assisted dieless wire drawing. Here only investigations on the principle of the process were possible. In this process a wire is wound up at a higher speed than wound off resulting in a reduction of the cross section. The reduction of the cross section happens in a region heated by the laser beam because of the improved forming properties in this region as described above. The preliminary experiments have shown in a discontinuously working set-up that this process is feasible. Further investigation will be performed in a subsequent project. Also for this process there were already requests from industry.