Deep penetration welding performance of a high average power, multi-kilowatt peak power carbon dioxide laser

Abstract

A 30 kW, continuous wave (CW), Photo-initiated, Impulse-enhanced, Electrically-excited (PIE) CO2 laser is presented. This high power laser system is unique in that it is also capable of modulated optical output over a wide range of frequencies featuring multi-kilowatt peak power with high average power. The primary focus of this paper is documentation of the enhanced performance achievable from this laser when operated under a burst mode excitation technique. Excitation of the system, using a burst mode process, results in a dramatic change in the output characteristics of the laser. Control of burst frequency and duty cycle provides a convenient means to alter the time-varying nature of the output beam. Low burst frequencies result in clearly defined pulse profiles, falling to zero in between pulses. Increasing burst frequency results in a significant offset or quasi-CW time-varying output. At low burst durations, optical output has a triangular profile. Increasing burst duty cycles produce square optical pulse shape profiles. High frequency, large duty cycle operation produces an optical output approaching that observed in CW. The significance of these results are manifest in a major enhancement in deep penetration welding at reduced average laser powers. Welding performance, featuring a 400% increase in penetration as compared to CW welding, has been demonstrated at the same average power level. Reductions in average laser power and plasma suppression gas requirements could translate into major savings in high power laser welding applications utilizing this unique excitation process. Another attractive aspect of burst mode welding is its potential for deep penetration alloying of inexpensive base materials through incorporation of a computer controlled wire-feed/MIG system.A 30 kW, continuous wave (CW), Photo-initiated, Impulse-enhanced, Electrically-excited (PIE) CO2 laser is presented. This high power laser system is unique in that it is also capable of modulated optical output over a wide range of frequencies featuring multi-kilowatt peak power with high average power. The primary focus of this paper is documentation of the enhanced performance achievable from this laser when operated under a burst mode excitation technique. Excitation of the system, using a burst mode process, results in a dramatic change in the output characteristics of the laser. Control of burst frequency and duty cycle provides a convenient means to alter the time-varying nature of the output beam. Low burst frequencies result in clearly defined pulse profiles, falling to zero in between pulses. Increasing burst frequency results in a significant offset or quasi-CW time-varying output. At low burst durations, optical output has a triangular profile. Increasing burst duty cycles produce square optica...