Abstract
Effects of Laval nozzle on assist gas flow and the machined results in precision cutting of thin plate by pulsed YAG laser were experimentally investigated. Assist gas flow from Laval nozzle does not have Mach Shock Disk, and goes more straight than a traditional convergent nozzle. Therefore, the pressure on workpiece increases, since assist gas flow from Laval nozzle can utilize energy more efficiently. However, caution is necessary in setting of cylinder gas pressure, since Laval nozzle has many unstable regions in which the pressure on workpiece changes periodically. Using Laval nozzle makes it possible to reduce the height of dross even under low cylinder gas pressure condition. Thus the consumption of assist gas flow quantity can be reduced. Moreover, it was pointed out that the convexed inner wall of nozzle leads of reduction of dross generation.
