## 4 Results
### The Second Cycle  
The first cycle ends with the preparation of information transferred from the LBM model to Unity. The second cycle begins in Unity with the introduction of the terrain into the modeling space. Because the second cycle is performed with the same material, the terrain completely reflects the result of laser treatment in the first cycle, i.e., without the removal of untreated powder. The terrain before powder deposition is presented in Figure 9a (it can be compared with Figure 7c). The modeling space is then filled with falling particles (Figure 9b). The final state after deposition is shown in Figure 9c. The level of the powder obtained with falling particles in Unity is somewhat higher than that used in the consequent LBM simulation. The re-coating operation is not shown here. The total thickness of the two powder layers is approximately 42 \(\upmu\)m, and the thickness of the powder layer above the product is approximately 30 \(\upmu\)m.  
Figure 8: The first cycle. Temperature distribution (**a**) with the temperature scale (**d**) and the state of the material at the beginning (**b**) and end (**c**) of the track.  
Figure 7: 3D snapshots of the simulation of the first cycle of the laser treatment: the beginning of the first laser track (**a**), the middle of the second track (**b**), and the end of the third track (**c**).  
After the deposition of the second level of the powder and flattening with the roller, data were transferred to the LBM model. The second cycle of laser beam treatment along the closed track is then simulated. The beginning, end, and product view after the second cycle are shown in Figure 10.  
Figure 11 presents a cross-section of the simulation of the second cycle. The laser begins to melt the highest particles of the new powder layer (Figure 11a). The elliptic shape of the bottom surface of the product obtained after deposition of the previous layer can be seen. The material melts, flows deep and wide, melts neighboring particles, and begins to solidify close to the end of the rightward movement of the laser beam (Figure 11b). When the laser beam is moved backward, the right part is incompletely solidified (Figure 11c).  
Figure 12 presents the temperature distribution during the second cycle at the same time as the last two images in Figure 11. The temperature scale is presented in Figure 8d. Light green shows the location of the laser beam. Pink represents a temperature slightly above the melting temperature and shows the liquid volume close to solidification.  
Figure 11: Cross-sections of the second cycle of laser treatment simulation: the beginning of the laser movement (**a**), the end of movement to the right (**b**), and the middle of the backward movement (**c**).  
Figure 10: Simulation of the second cycle of the laser treatment along the closed track: the beginning (**a**) and the end (**b**) of the laser treatment, and a view of the product after the cycle (**c**).  
Figure 9: Powder deposition before the second cycle of laser treatment: state of the modeling space with the terrain collider after the first cycle and before deposition (**a**), the process of filling with powder (**b**), and the final state after deposition and before the second stage of laser treatment (**c**).