## 4 Discussion  
The simple CNC modification program designed by the authors covered a surface of 10 \(\times\) 10 mm with a tolerance of \(\pm\)1 mm depending on the accuracy of the sample positioning. The TRUMPF TruLaser Station 5004 used for the experiment did not have automatic sample positioning systems or automatic positioning of the laser head in relation to an object located in the working area of the device. Hence, minor inaccuracies in sample positioning relative to the point (0,0) of the coordinate system might have occurred. However, in the case of this experiment, this should not have a significant impact on the general results of the studies. The melting time was not precisely measured, but approximately ranged from several seconds to one minute. Samples prepared using an Nd: YAG laser were observed on two light microscopes. A ZEISS Stemi 2000-C model was used to obtain a 10\(\times\) magnification image, while the OLYMPUS VC50 BX51 model made it possible to obtain an image of the modifications made at 50\(\times\) and 100\(\times\) magnification, However, the 100\(\times\) magnification allowed a focus only on selected details at a given depth of remelting, and usually did not provide a clear image of the entire dimple. The first sample, presented in Figure 3, was melted in an irregular manner. The general shape of the modification corresponds with the movement commands, but the edges of the pattern are not consistent, and the size of a single dimple varies. Observations made using 50\(\times\) and 100\(\times\) magnifications show that individual dimples overlap, which is consistent with the experiment expectations. The single dimple diameter size is estimated to be 200 \(\upmu\)m. The direction of overlap alternates in rows in accordance with the direction of the movement of the laser beam. Individual rows of modification paths are spaced about 400 \(\upmu\)m apart. Many local burns were noticed, along with a strong sparkle formation during the process, which generates a risk of losing anti-corrosion properties. It also means that the procedure either contains a harmful combination of laser parameters or is lacking in base material protection. The path is also not repeatable, which means it cannot be taken into consideration for further tests and studies. The second sample, presented in Figure 4, was also melted in an irregular manner. The general shape of the modification corresponds with the movement commands, but the  
Figure 3: Microscopic observations of sample no. 1: (**a**) 10\(\times\) magnification by ZEISS; (**b**) 50\(\times\) magnification by Olympus; and (**c**) 100\(\times\) magnification by Olympus. edges of the pattern are not consistent, and the sizes of the single dimples vary. Observations made using 10\(\times\) magnification show that individual dimples strongly overlap. Moreover, 50\(\times\) and 100\(\times\) magnifications show that the ejected material almost completely covers the shape of the individual dimples. The direction of overlap alternates in rows in accordance with the direction of the movement of the laser beam. Individual rows of modification paths are not spaced apart. No local burns were noticed, although they might have been covered under the layer of ejected material. Some sparkles occurred during the process, but the damage was not as noticeable as it was on the first sample. This generates a risk of hidden spots with low mechanical and corrosion properties, which might result in a higher risk of cracking. It cannot yet be determined whether this procedure could be used for industrial purposes. Even though the individual meltings are not identical, the overall path seems to be repeatable. The most regular melting edges were formed on the third sample, presented in Figure 5. Compared to the other samples, the edges of the melting form an almost perfect circle, void of noticeable irregular edges. The combination of frequencies 3.8 Hz and 498 W power resulted in a regular honeycomb-like pattern.