Micro Cutting of Thin Copper Plate by Fiber Laser with Laval Nozzle

Fiber laser has many advantages such as compact size, high conversion efficiency, good beam mode, air cooling and maintenance free. Therefore, it has high possibility as an industrial light source in the near future. The beam from fiber laser can be focused in a micro spot because of its excellent beam quality. However, the narrow kerf leads to the difficulty of outflow of melted material. Therefore, micro cutting by a single-mode fiber laser is considerably difficult, then the high performance nozzles are strongly required. In the previous work, authors developed a high performance nozzle, which can increase the velocity of assist gas flow and makes it possible to reduce the dross in the micro kerf. Therefore, high performance cutting by a single-mode fiber laser can be expected by using our newly designed nozzle. In this study, the effect of nozzle shape on the machining results in precision cutting of thin copper plate by a Q-switched single-mode fiber laser was experimentally investigated. It was found that the high speed cutting at 30mm/s could be carried out by the high performance nozzle under low pulse frequency condition. Besides, the reduction of the dross and good kerf shape could be attained in the case of nitrogen assist gas.