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Increasing productivity in splitting up of metal sheets by means of mechanical cutting processes is today limited by long change-over times as well as nonproductive times and insufficient quality caused by tool wear. In the case of high-quality materials even a slight quality reduction concerning development of dross attachment and induced stress leads to a lot of rejects. In order to increase the cutting speeds within a range economical for industrial use, i.e. about 100 m/min, a completely new type of laser cutting process had to be developed. As opposed to conventional laser cutting, during which a semicylindric cutting front is formed, a closed keyhole with subsequent melt film ejection is produced during the completely new laser cutting process. The incoupling of energy no longer only results from pure surface absorption but in addition from plasma formation and multiple reflection. With the help of the wear resisting tool `laser' the cutting quality is constantly good and can even be significantly improved in comparison with the conventional cutting method with circular knifes. In the case of a sheet thickness of 0.2 mm grain oriented electrical steel can be cut e.g. with a cutting speed of 130 m/min, aluminum with 270 m/min, copper with 95 m/min and zinc with 280 m/min; the necessary laser power is 1300 W. Based on the results of basic research the prototype of a laser slitting line was constructed and went into operation in autumn 1991. Up to now various materials for different customers have been cut on this slitting line and used in industry. Especially when cutting grain oriented electrical steel, which is a material with very high requirements on the cutting process, it becomes evident that the laser cutting process compared with the conventional technique has considerable advantages concerning cutting quality and quality assurance.
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