Melt behavior and its effect on process speed in precision cutting of thin metal sheets using Q-switched Nd:YAG green laser

Abstract

Improving processing rates matches the demand for less cycle time for industrial applications. While high precision laser cutting calls for narrow kerf width and reduced heat-affected-zone (HAZ), test cutting of thin stainless steel and copper sheets using high beam quality Nd: YAG lasers indicates that, as the laser beam is focused down to a certain size, kerf formation and material removal becomes more difficult as beam size decreases. It is found that even when laser power is sufficiently high to penetrate the sheet sample, the melt pool re-solidifies backward and heals the kerf immediately after the laser beam passes, leading to low cutting efficiency. The melt behavior is analyzed in terms of energy utilization and material removal mechanisms. The results suggest that melt removal is the rate determination factor in Q-switched laser cutting of metal sheets.Improving processing rates matches the demand for less cycle time for industrial applications. While high precision laser cutting calls for narrow kerf width and reduced heat-affected-zone (HAZ), test cutting of thin stainless steel and copper sheets using high beam quality Nd: YAG lasers indicates that, as the laser beam is focused down to a certain size, kerf formation and material removal becomes more difficult as beam size decreases. It is found that even when laser power is sufficiently high to penetrate the sheet sample, the melt pool re-solidifies backward and heals the kerf immediately after the laser beam passes, leading to low cutting efficiency. The melt behavior is analyzed in terms of energy utilization and material removal mechanisms. The results suggest that melt removal is the rate determination factor in Q-switched laser cutting of metal sheets.