Remote cutting of steel plates by a pulsed laser without assistant gas.
G. Pilot, J.P Grandjean, J.P Alfille, P. Muys, EURADWASTE'99, 15-18 novembre 1999, Luxembourg.
In most industrial laser cutting applications, the tip of the focusing head is located near the
workpiece. The standoff between the workpiece and the assistant gas nozzle is about 1 to 3 mm.
This type of cutting process which was investigated during former studies presents several
drawbacks: using multiple-joints robots difficulties may arise when programming paths around metallic structures, limited accessible volume, risk of collision between the cutting head and a complex work environment.
This consideration led to the idea of adopting a remote cutting procedure in order to avoid the above dificulties.
The used laser is a 1.2 kW pulsed Nd-YAG laser and the laser beam is guided by a high-refiaction silica optical fiber 50 m long with a 1 mm core diameter, protected by a 10 mm diameter flexible metallic sheath.
The experiments were made with a 500 mm standoff and a 1000 mm standoff for which two options were considered, one using aspherical lenses (as for 500 mm standoff) and a second using thick spherical lenses.
In order to measure the secondary wastes, several experiments with a 50 m optical fiber and 1 m standoff were carried in a 32 m3 cutting cell equipped with an exhaust ventilation of 300 m3.h-'. 2, 5 and 10 mm thickness mild steel and stainless steel plates were cut inside this cell in a vertical position with cutting speed of respectively 0.15 dmin, 0.05 dmin and 0.01 dmin.
The balance of solid secondary emissions (sedimented dross, aerosols in the exhaust duct and deposits on the walls of the cell) has been established as the characterization of the aerosols which are proportionally important (10%) in the case of stainless steel.