## 2 Materials and Methods
### Build Layout
#### 2.3.3 Controlling Slice Distribution  
To minimize the risk of machine failure, it is generally recommended to achieve relatively smooth transitions between layers in terms of energy density, i.e., the amount of energy applied to one layer should not deviate too much from the amount of energy applied to the adjacent layers. In practice, this means that parts should preferably be evenly distributed along the build direction or optimally have a uniform intersection area. The cross-sectional area of slices at user-defined intervals can be exported from Magics as an Excel file, effectively yielding the sintered area of each layer. The slice distribution achieved from inserting the specimens of build 1 from Table A1 into the build space yields the graph in Figure 5(a), which exhibits large portions without any energy input. These portions without energy input originate from the safe distance between specimens in the z-direction and cannot be eliminated without the introduction of additional specimens. This is demonstrated in Figure 5(b), which shows the slice distribution for spheres of 90 mm diameter inserted at the positions of the specimens. While Figure 6 displays some minor gaps in the slice distribution, the actual layouts of the three builds would be significantly worse because the true geometry of the artifact is much more complex than a perfect sphere, leading to large portions in z-direction without any energy input at all. To counteract the risk associated with the energy fluctuations, one could either change the previously determined positions, or objects could be added to the low-energy volumes to even out the slice distribution. The second option enables additional information to be collected from the experiment by adding useful objects to the unused volumes marked in green in Figure 7.  
The object inserted in the additional space should be massive enough to significantly contribute to an even slice distribution but also provide additional information that contributes to the validity and reliability of the experiment. The recently developed standard for test artifacts in additive manufacturing ISO/ASTM 52902:2019 [38] provides several candidates in STEP format. The circular artifact CA_F (Figure 8) was selected due to its appropriate size, volume, and feature type. The model was loaded to SolidWorks, exported as a binary STL file, and later duplicated and reoriented in Magics. Figure 6: Slice distribution graphs showing the sintered area per layer. (**a**) Slice distribution for build 1 without additional specimens; (**b**) slice distribution for perfect spheres of 90 mm diameter in all positions. With reference to Figure 7, the green areas on the edges of the build volume fit one sample of CA_F each. Therefore, these volumes are used to investigate the effect of the laser angle (as opposed to the build direction), which is shown to be a decisive factor for surface roughness in LB-PBF/M [39]. On each side of the build space, one sample is fabricated with the cylinder orthogonal to the layers, and one sample is adjusted, so the axis of the cylinder points directly towards the laser origin (the last deflection point, i.e., the last mirror before the laser beam enters the build volume). For any point on the powder bed, the laser angle \(\xi\) can be expressed as:  
\[\xi=\cos^{-1}\left(\frac{\overset{\rightarrow}{\text{P}}\cdot\overset{ \rightarrow}{1}}{\overset{\rightarrow}{\text{P}}\|\cdot\|\overset{\rightarrow }{1}\|}\right) \tag{1}\]  
Figure 8: Cylindrical test artifact CA_F collected from ISO/ASTM 52902:2019(E). (**a**) 3D-model; (**b**) constellation of six samples in orthogonal orientations. Figure 7: Open volumes available to even out the slice distribution. (**a**) Top view of available spaces in the xy-plane; (**b**) front view of the available spaces along the z-axis.