ＵＶレーザによる高アスペクト比小径穴あけ加工（第４報）―熱の蓄積の影響― : —熱の蓄積の影響—

概要

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It has been reported that heat accumulation enables the ablation threshold of the material lower and ablation rate higher in laser drilling. In this paper, the influence of the heat accumulation on high-aspect-ratio hole drilling with the fourth harmonic wave of Nd : YVO4 laser was investigated. Repetition rate caused the much difference of the depth, for example, the depths of the holes were changed from 1200 μm to 3000 μm, by changing the repetition rate from 1 kHz to 10 kHz, when the laser energy was set at 100 μJ/pulse. The repetition rates which the deepest holes were obtained at were dependent on the pulse energies. Temperature rise with 10 kHz pulses was calculated to be 20 times higher than that with 1 kHz pulses, when the successive pulse illuminated. The reasons that the repetition rate caused the different of the depths, were the diameters at the entrance of the holes, the heat accumulation effect and shielding effect by ablated particles.