# Investigations on Factors Affecting 3D-Printed Holes Dimensional Accuracy and Repeatability
## 3 Results and Discussion
### Results of the Experiment 1
The current correlation trend between the layer height and the dimensional accuracy was also in agreement with the results of [PERSON] et al. (2018) for the 8 mm vertical axis hole, and [PERSON] et al. (2018) for the 10 mm hole with vertical axis. In the current research, the influence trends were confirmed for three different holes diameters and three process parameters. Moreover, the most influential factors were determined, with the printing speed being the least important. This is considered relevant information as the printing speed is directly related to the printing time and cost. Using the best combination of parameters from the dimensional accuracy standpoint, three more prints were built in the manufacturing sites 2-5. Figure 6 presents a comparison between the mean diameter values obtained in the second stage of the experiment 1 (see also the Supplementary Material). The calculated \(p\)-value of 0.98 (one-way ANOVA) for the data on diameters (see Supplementary Material) showed that there are no statistically significant differences between the hole accuracies in the test parts manufactured across materials, equipment, and slicers, and that the holes diameter dimensional repeatability is assured in each case/manufacturing site. This is beneficial for the 3 DP delocalized mass production and for 3 DP-POCs. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Source** & **DF** & **SS** & **MS** & **F-Value** & \(p\)**-Value** \\ \hline \multicolumn{6}{c}{**Analysis of Variance for 10 mm diameter**} \\ Shells & 1 & 0.006769 & 0.006769 & 39.1 & 0 \\ Layer thickness & 1 & 0.02332 & 0.02332 & 134.7 & 0 \\ Speed & 2 & 0.0004 & 0.0002 & 1.16 & 0.368 \\ Error & 7 & 0.001212 & 0.000173 & & \\ Total & 11 & 0.031701 & & & \\ R\({}^{2}\): 96.18\% & \multicolumn{6}{c}{Adjusted R\({}^{2}\): 93.99\%} \\ \hline \multicolumn{6}{c}{**Analysis of Variance for 8 mm diameter**} \\ Shells & 1 & 0.010092 & 0.010092 & 143.83 & 0 \\ Layer thickness & 1 & 0.04296 & 0.04296 & 612.26 & 0 \\ Speed & 2 & 0.001597 & 0.000799 & 11.38 & 0.006 \\ Error & 7 & 0.000491 & 0.00007 & & \\ Total & 11 & 0.055141 & & & \\ R\({}^{2}\): 99.11\% & \multicolumn{6}{c}{Adjusted R\({}^{2}\): 98.60\%} \\ \hline \multicolumn{6}{c}{**Analysis of Variance for 6 mm diameter**} \\ Shells & 1 & 0.013736 & 0.013736 & 180.29 & 0 \\ Layer thickness & 1 & 0.05096 & 0.05096 & 668.85 & 0 \\ Speed & 2 & 0.006189 & 0.003094 & 40.61 & 0 \\ Error & 7 & 0.000533 & 0.000076 & & \\ Total & 11 & 0.071419 & & & \\ R\({}^{2}\): 99.25\% & \multicolumn{6}{c}{Adjusted R\({}^{2}\): 98.63\%} \\ \hline \hline \multicolumn{6}{c}{(DF: degrees of freedom; SS: sum of squares; MS: mean square error).} \\ \end{tabular}
\end{table} 
Table 5: ANOVA results for holes\({}^{\prime}\) mean diameters response. Figure 4: Main effect plots for the holes dimensional accuracy: (**a**) 10 mm holes; (**b**) 6 mm holes; (**c**) 8 mm holes. Figure 5: Interaction plots for the holes dimensional accuracy (**a**) 10 mm holes; (**b**) 8 mm holes; (**c**) 6 mm holes. Figure 6: Mean diameter values for tests parts built using different 3D printers, materials and slicing software.