Product Code: ICAL05_205

Study of Metal Drilling Characteristics with Q-Switched CO2 Laser
Authors:
Atsushi Sugihashi, Nippon Steel Corporation; Futtsu Chiba Japan
Koji Hirano, Nippon Steel Corporation; Futtsu Chiba Japan
Motoi Kido, Nippon Steel Corporation; Futtsu Chiba Japan
Naoya Hamada, Nippon Steel Corporation; Futtsu, Chiba Japan
Presented at ICALEO 2005

We studied metal drilling characteristics using Q-switched CO2 laser with the average output power of 1kW. A rotating chopper inserted in the cavity realized the Q-switch operation. The pulse repetition rate of the laser is as high as tens of kHz. The temporal waveform of the pulse is comprised of high-peak spike at the very beginning of the pulse succeeded by the tail part whose power is comparable to CW operation. The initial spike has peak power of tens of kW to hundreds of kW and pulse width of about one microsecond. This part is useful to enhance the relatively low absorption characteristics of the CO2 laser beam and to initiate metal drilling. The tail part has nearly constant power of several kW. By changing the width of the slit and rotation speed of the chopper and pump power of the CO2 laser, the power and width of the tail part can be controlled quite independently.
Taking advantage of initial spike effect and of controllability of temporal pulse shape of the tail part, we studied the influence of the temporal pulse shape on metal drilling property. We revealed that (1) diameter of drilled holes is mainly determined by the power level of the tail part, and that (2) depth is predominantly defined by the width of the tail part duration. Little correlation was observed between these two parameters. We thus conclude that wide range of the hole diameter and depth can be realized by the Q-switched CO2 laser at high processing speed due to its high average power.