## 3 Results
### Variation between Positions in the Build Chamber  
The designed build layout facilitates the comparison of discrete positions in the build chamber in the z-direction as well as in the xy-plane. A slight trend towards tighter tolerances in the higher end of the build may be observed in Figure 22a, but the statistical significance of this trend is inconclusive from the current analysis. Except for one extreme outlier at the lowest level, the distributions among the different z-levels are quite similar, as seen in the kernel density estimation of Figure 22b. The statistical description of the data is tabulated in Table 10, where the columns correspond to the five levels of z-positions, the mean value for all z-levels of a specific position considered across all three builds, and the difference is calculated as the difference between the minimum and the maximum value from the same population. A more distinct variation may be found within each z-level as the position in the xy-plane appears to be of significant influence on the geometric accuracy and the observed variation. This discrepancy is apparent in all the preliminary analyses but exemplified here by diametrical error due to the clear results for this particular characteristic. When comparing the diametrical error of cylinders fabricated in the front-right corner to the ones fabricated at the rear center, it is clear that the position in the front-right is far more accurate than the rear positions, as shown in Figure 23. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **Build 1** & **Build 2** & **Build 3** & **Mean** & **Difference** \\ \hline n & 90 & 90 & 90 & – & – \\ \(\overline{\pi}\) & 0.100579 & 0.091916 & 0.091149 & 0.094548 & 0.040117 \\ \(\sigma\) & 0.049281 & 0.028711 & 0.025326 & 0.026291 & 0.040889 \\ Min & 0.058330 & 0.052950 & 0.054538 & 0.065753 & 0.002214 \\
25\% & 0.074281 & 0.072488 & 0.070237 & 0.075634 & 0.019272 \\
50\% & 0.084530 & 0.083260 & 0.085130 & 0.086795 & 0.027337 \\
75\% & 0.105167 & 0.103796 & 0.107094 & 0.103580 & 0.049757 \\ Max & 0.400476 & 0.193571 & 0.162345 & 0.211045 & 0.301388 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Statistical description of measured flatness error of planes 2 and 5 from HX2 and the difference between the three builds. Figure 21: Comparison of measured error between builds considering vertical planes. (**a**) A boxplot visualizing the measured flatness error; (**b**) kernel density estimation of the measured values. Figure 23: Boxplot for diametrical error for the anchor specimens across all three builds. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & **Level 1** & **Level 2** & **Level 3** & **Level 4** & **Level 5** & **Mean** & **Difference** \\ \hline n & 54 & 54 & 54 & 54 & 54 & – & – \\ \(\overline{\pi}\) & 0.104644 & 0.093710 & 0.096776 & 0.089911 & 0.087698 & 0.094548 & 0.054769 \\ \(\sigma\) & 0.055572 & 0.031782 & 0.033028 & 0.025317 & 0.024961 & 0.024226 & 0.050230 \\ Min & 0.052950 & 0.059441 & 0.058330 & 0.060803 & 0.054538 & 0.063893 & 0.011309 \\ 25\% & 0.071951 & 0.073234 & 0.076536 & 0.072325 & 0.068809 & 0.078640 & 0.025433 \\ 50\% & 0.088348 & 0.088711 & 0.084912 & 0.084803 & 0.078242 & 0.087961 & 0.041132 \\ 75\% & 0.116436 & 0.104522 & 0.104658 & 0.101218 & 0.102372 & 0.110861 & 0.063584 \\ Max & 0.400476 & 0.222995 & 0.199056 & 0.193571 & 0.167091 & 0.176043 & 0.328619 \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Statistical description of measured flatness error of planes 2 and 5 from HX2 and the difference between the five z-levels. Figure 22: Comparison of flatness error at different z-positions in the build chamber. (**a**) Boxplot of all five z-levels; (**b**) kernel density estimations for the levels of z-positions. comparison of all positions in the build space. The boxplot of Figure 24 shows the measured variations considering the specimens' position along the x- and y-axes.