Role of strong focusability on the welding process

Thin disk lasers as well as fiber lasers are distinguished by their strong focus ability and high efficiency. With the availability of such lasers sources in a h igh power region, keyhole welding with very small focus diameters down to 50 µm became possible. Typical focus diameter regimes of such laser sources can now be compared with regard to their effect on welding depth and process efficiency. B ased on result of thin disk laser experiments it has been shown in earlier publi cations that the influence of the divergence angle on the achievable welding dep th increase dramatically for lower spot diameters. This effect stands in contras t to the behavior at higher spot diameters, but was now confirmed by additional experiments with a fiber laser which made available smaller divergence values. N o influence of focus diameter and divergence angle on the reachable cross sectio nal area for both laser systems has been observed, on the other hand. That means that in the investigated parameter range the process efficiency of keyhole weld ing is in fact independent of the focusability of the laser source.