Abstract
Construction of machining mechanism with laser beam is useful for deciding the algorithm in case of calculating the machined shapes. In the former paper, melting and removing processes were investigated through machinability of various metals with laser beam. In this paper, the mechanism was investigated through observations of various phenomena in laser machining. The results obtained are as follows. (1) The reflectivity of laser beam at the work surface decreased gradually with increasing the temperature of workpiece and rapidly with generation of a keyhole in the molten pool. (2) The diameter and the penetration speed of the keyhole were estimated by observations of laser light passing through the workpiece. (3) The speed decreased with an increase in the machined depth, and was influenced mainly by thermal diffusivity of the workpiece and melting point in case of low and high power density, respectively. (4) The plume produced with laser irradiation was observed by high speed photograph and the transmissivity of the plume was estimated by observations of laser light transmitting through the plume. (5) About 20% of laser beam energy was absorbed by the plume in pure aluminum and about 38% in stainless steel (SUS304) when the laser beam was irradiated with power density of12.0MW/cm2 and pulse duration of 4.5ms.
