# Analysis of Building Platform Inhomogeneities in PBF-LB/M Process on Alloy 718
## 3 Results and Discussion
### Melt Pool Analysis
As the Differential Pressure is reduced, the Melt Pool Width decreases (consequently resulting in the overlap between adjacent Melt Pools). A similar effect with respect to Melt Pool Depth analysis is observed while moving from the left to the right side of the building platform and reducing the Exposed Area resulting in an increase in the Melt Pool Width. These results agree with those discussed previously about the Track's stability assessment, Porosity analysis, and Melt Pool Depth. Also in this case, the production of spatter particles is increased significantly with the increase in the Exposed Area while lowering the Differential Pressure reduces the laser energy absorptivity of the powder bed that hinders the effective interlayer conductive heat transfer that occurs between adjacent Melt Pools. Due to these boundary conditions, either a shallow Melt Pool or even the absence of one in some cases (as shown in Figure 10A,B) can be observed during the printing phase. Figure 16 shows the Interaction plot between the Exposed Area, Position, and Differential Plot for the Melt Pool Width. From the analysis, it is evident the interactions within the different parameters are low and there is a zero level of interaction in some cases. As discussed in the Melt Pool Depth analysis, no interaction is observed between the Exposed Area and Differential Pressure, and between the Position and Differential Pressure. However, a low interaction level is observed between the Position and Exposed Area for certain combinations (i.e., Position 3 and 5 and Exposed Area of 14%, 26%, and 37%). In Figures 17 and 18, the contour plot for the Melt Pool Depth and Width as a function of the Exposed Area, Position, and Differential Pressure, respectively, is illustrated. Figure 8:0 Overview of main effects of exposed area, position and differential pressure on melt pool width. Figure 8:1 Interaction plots for melt pool width overview. Interaction plots overview: (**a**) Differential pressure vs. position; (**b**) Differential pressure vs. exposed area; (**c**) Position vs. exposed area. Figure 8:2 Contour plot of melt pool depth as function of exposed area, position and differential pressure: (**a**) Low level; (**b**) Nominal level; (**c**) High level. From Figure 17, the Melt Pool Depth is shown in a progressive manner. The light green zones indicate a shallow Melt Pool while the dark green areas indicate the contrary. It should be that the area of the shallow Melt Pool progressively decreases as the Differential Pressure increases. These studies confirm the validity of the previous analyses performed with respect to Track Stability and Porosity Analysis. Figure 18 represents the contour plot of the Melt Pool width as a function of the Exposed Area, Position, and Differential Pressure. The light green zones indicate a narrow Melt Pool while the dark green areas indicate the contrary. The same trend observed for the Melt Pool Depth is observed also for the Melt Pool Width in terms of increasing the Differential Pressure, i.e., the area of the narrow Melt Pool progressively decreases as the Differential Pressure increases.