Study on Technology of Picosecond Laser Making Micro-Hole with Helical Drilling

In order to explore the high-quality forming process of micro-holes, the picosecond laser combined with helical drilling technology was used to carry out the basic experiments of micro-hole forming. The shape (taper and size) of the micro-hole can be controlled by changing the deflection angle and translation of the wedge prism in the optical path of the rotating optical system. Taking 1-mm 304 stainless steel as an example, the influence of processing parameters such as laser pulse energy, defocusing amount, repetition frequency and laser helical drilling speed on the quality of micro-hole processing was studied. According to the experimental results, laser pulse energy is the key factor of micro-hole forming quality, defocusing amount can change the taper of the micro-hole to a certain extent, and the repetition frequency and rotation speed of the laser determine the thermal influence of the micro-hole and the thickness of the recasting layer. While laser pulse energy is 141 mu J, repetition frequency is 66.67 kHz, defocusing amount is +0.1 mm, and laser helical drilling speed is 8000 r/min, the high-quality micro-holes with pore diameters ranging from 100 to 300 mu m and controllable tapers can be obtained.