Clarification of the Mechanism of Pulse Laser Grinding of Nanosecond Lasers Using High-Speed Camera Imaging

Abstract

Pulse laser grinding (PLG), as a cutting tool processing method, can not only achieve edge sharpening with high precision, but it can also produce surface modification. For example, polycrystalline cubic boron nitride (PCBN) tools processed by PLG can show increased hardness due to the reduction in defects. However, the mechanism of edge formation under PLG processing remains unclear. In this study, by observing the plasma generated during processing using a high-speed camera, the elementary process for each laser pulse of the PLG process was visualized. The plasma luminescence moved successively through four stages: multipoint luminescence, uniform luminescence, the downward movement of the luminous center, and faint luminescence. By comparing the results of three different laser pulse pitches (0.2, 2, and 20 μm), it was found that the pulse pitch had a significant influence on the PLG processing mode. When the pulse pitch was too small, the sidewall effect was likely to lead to local excess machining. The large pulse pitch resulted in processed surfaces that could not be fully covered by laser irradiation, and it was preferred to remove the decrease threshold subsequently. Thus, the moderate pulse pitch condition showed a superior processed surface compared to the others.