## 4 Discussion
For a 30% infill density, the FDM printer needed 41 min for one part, while for 90% the time extended to 46 min. This was due to the larger volume of deposited material, 6 g for 30% and 8 g for 90%, respectively. Another parameter that can be adjusted during FDM forming is the number of contour layers. There is a significant increase in strength with a higher number of perimeter layers, unrelated to the infill density. Results of the tensile stress test are presented in Table 4. The most significant increase is noted when comparing 3 and 11 perimeter layers: they have 50% to 93% of the mechanical strength of injection molded parts, respectively. This observation suggests that the fibers deposited parallel to the \(Y\)-axis of the worktable are the main structural component affecting the mechanical strength. The deposition of the fibers in the perimeter layers of \"flat\" and \"horizontal\" samples is parallel to the extension forces affecting the samples during the mechanical tests. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **(FDM)** & **(FDM)** & **(FDM)** & **Injection** \\  & **Vertical** & **Flat** & **Horizontal** & **Molded** \\ \hline Tensile strength [MPa] & 13.39 & 24.36 & 26.73 & 40.82 \\ In relation to injection molding & 33\% & 60\% & 65\% & - \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Results of the tensile tests for the samples printed with different orientation and injection molded reference samples. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & **30\%** & **50\%** & **70\%** & **90\%** & **100\%** & **Injection** \\  & & & & & & **Molded** \\ \hline Tensile strength [MPa] & 19.01 & 24.26 & 24.76 & 25.41 & 28.35 & 40.82 \\ In relation to injection molding & 47\% & 59\% & 61\% & 62\% & 69\% & - \\ In relation to 100\% infill density & 67\% & 86\% & 87\% & 90\% & - & - \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Tensile stress results depending on the infill density of printed samples. The obtained results indicate that the number of perimeter layers has a significant impact on the tensile strength of the samples, resulting in an increase of up to 100% in the value for the 30% infill. At the same time, the infill density impact was less significant, with a maximum 33% increase of the tensile strength value for the three perimeter layer samples. Experiments showed that the volume of the filament material used to make the sample increased slightly with more perimeter layers. In addition, a significant increase in the time needed to form the sample was observed. For samples with 50% infill density with three contour layers, it took 48 min and 7 g of material, while for 11 contour layers, 53 min and 9 g, respectively. The differences were also related to the samples' shape, which translates to the geometry of the final components. This was visible if, instead of sample type 1A (40 mm2), we used 5A samples (8 mm\({}^{2}\)). In such a case, three perimeter layers for type 1A constituted 47% of the sample cross section, and for 5A type, the perimeter wall covered 84% of the sample cross section. In such a case, the infill density had little impact on the mechanical properties of the samples, while the perimeters occupied a larger part of the sample cross section. We also assumed that the sample type (1A, 5A) had a little effect on the mechanical properties of the samples, with similar geometry parameters, here analyzed for the samples with 80% perimeters covering the cross section. However, it turned out that sample type 1A with 9 contour layers had 86% of the value of injection molded samples' strength, while sample 1A with 11 contour layers had almost the same value as the injection molded part (97%), while at the same time for type 5A it was even up to 110% (Figures 9 and 10) for the samples printed with layer thickness below 0.25 mm. Such a difference in the results was due to the geometry of the samples and the fibrous nature of the 3D printed parts in the FDM technique.