Femtosecond laser dot-matrix marking on nickel-based alloy using a simple diaphragm-based spatial shaped modulation: Size and position control of marking units with high recognition rate

In this study, a method for dot-matrix marking with femtosecond laser on nickel-based alloy using diaphragm modulation was proposed. The simulation results showed that the edge quality and recognition uniformity of the crater were improved because of the diffraction effect of the diaphragm. Moreover, the confinement of the diaphragm could ensure the position accuracy. First, the reasonable size of diaphragm turned out to be from 8 to 10 mm. With the addition of the diaphragms, the regular variation of the diameters of the craters under different parameters was beneficial to control the size of the marking units. Thanks to the edge diffraction effect, the melt phenomenon on the edge of the craters almost disappeared, so the boundary of the crater was clear. In addition, the roundness of the crater increased by a maximum of 6%. Because the difference of gray value of different areas within the crater decreased by 60%, the recognition uniformity and the recognition rate of the marking were improved. Moreover, it was found that the contaminated area did not affect the identification of the marking. Therefore, with spatial shaping of laser beam with diaphragm, the femtosecond laser marking technology can have the advantage of high position precision, dimensional accuracy, processing quality and recognition rate.