Laser cutting stainless steel with dual focus lenses

In this article the performance of a new type of lens is compared with trad itional meniscus lenses for CO2 laser cutting of medium (>5 mm) section sta inless steel. Dual Focus(TM) lenses produce two focus spots, one above the other. This type of optic was found to be capable of higher cutting speeds and better quality cuts. A phenomenological model is presented which explai ns the superior performance of Dual Focus lenses. The model concentrates up on the fact that during high speed cutting of medium section metals, the la ser does not irradiate the lower portion of the cut zone. This lower part o f the cut is heated by the melt flowing over it, which has been previously heated by the laser, This melt preheating involves narrower kerfs and highe r cut speeds if a dual focus lens is used. (C) 2000 Laser Institute of Amer ica. [S1042-346X(00)00506-4].