7 Micro-hole Arrays and Net-like Structure Fabrication …
221
Fig. 7.8 The sample processed at a scanning speed of a 107 μm/s, b 39 μm/s, and c 8.3 μm/s,
respectively, and the corresponding diffraction pattern illustrated is the experimental schematic and
the power at each stage [22]
and processed deep hole with better morphology on stainless steel as shown in
Fig. 7.9. The experimental results show that the micro-holes outlet diameter increases
with increasing repetition frequency when micromachining in the air. Because the
melted debris cannot be completely ejected out with increasing repetition frequency
which can decrease air ionization threshold will decrease. The plasma and debris
remained in the holes act on the wall of the holes again and the divergence and perturbation of the laser, resulting in an increased outlet diameter as shown in Fig. 7.9a. The
diameter of micro-holes processed in the vacuum does not change significantly with
the repetition frequency as shown in Fig. 7.9b, and the inlet diameter of the microholes in the air is ultimately the same as in the vacuum. Because the material and
the air are rapidly heated, the gas density is reduced which creates a quasi-vacuum
221
Fig. 7.8 The sample processed at a scanning speed of a 107 μm/s, b 39 μm/s, and c 8.3 μm/s,
respectively, and the corresponding diffraction pattern illustrated is the experimental schematic and
the power at each stage [22]
and processed deep hole with better morphology on stainless steel as shown in
Fig. 7.9. The experimental results show that the micro-holes outlet diameter increases
with increasing repetition frequency when micromachining in the air. Because the
melted debris cannot be completely ejected out with increasing repetition frequency
which can decrease air ionization threshold will decrease. The plasma and debris
remained in the holes act on the wall of the holes again and the divergence and perturbation of the laser, resulting in an increased outlet diameter as shown in Fig. 7.9a. The
diameter of micro-holes processed in the vacuum does not change significantly with
the repetition frequency as shown in Fig. 7.9b, and the inlet diameter of the microholes in the air is ultimately the same as in the vacuum. Because the material and
the air are rapidly heated, the gas density is reduced which creates a quasi-vacuum