Inert gas cutting of thick-section stainless steel and medium-section aluminum using a high power fiber laser

Inert gas assisted laser cutting of 10 mm stainless steel plate and 4 mm aluminum sheet was performed with a 5 kW fiber laser. The effects of laser power, cutting speed, focal point position, and assist gas pressure on the cutting performance and cut quality were investigated. Clean cut surfaces without or with minimal dross were achieved with some combinations of process parameters and attempts were made to define parameter windows in terms of cutting speed and laser power for good quality cutting. The maximum cutting speeds for acceptable cut quality were determined at different power levels. The range at which complete through cutting could be achieved (so-called parameter window) was limited upwards by insufficient power intensity to obtain through cutting at high cutting speeds and downwards by heat conduction at slow cutting speeds. The effects of focal point position and assist gas pressure on the striation pattern (cut surface roughness) were also examined. Low surface roughness was achieved with the focal point position inside the workpiece showing the need for a wider kerf for better melt ejection in thick-section metal cutting. There was also a reduction in surface roughness with increase in assist gas pressure, but there was no significant reduction in surface roughness above the gas pressure of 16 bar, which could be due to the gas flow dynamics inside the narrow cut kerf at high assist-gas pressures.