Investigation of the micro-milling process of steel with THz bursts of ultrashort laser pulses

Burst mode (BM) processing with femtosecond laser pulses is emerging as a versatile tool for manufacturing micro-components on different materials, thanks to its ability to reduce the thermal load, which ensures highly precise and accurate miniaturization. However, a systematic investigation of the influence of the experimental parameters introduced by such irradiation mode, i.e., the number of pulses within the burst, their polarization and the intra-burst frequency, on the ablation process has not been reported, yet. In this work, we exploited a statistical approach based on the Design of Experiment (DoE) to study the micro-milling process of steel with bursts. Two prediction models were defined, describing the relationship between the working parameters, i.e., average power, number of overscans, laser repetition rate, scan speed and number of pulses within the bursts, and the response variables, i.e., ablated depth and surface roughness, revealing burst mode as a very promising solution to improve the surface finishing of ultrashort laser pulses micromilled components.