## 3 Results and Discussion  
### Finite Element Analysis  
The study of the stresses and deformations of the materials chosen for the printing processes (i.e., PET/FDM for the concept model and AISI 316L/SLM for the functional one) and for the AISI 304 of the original product was carried out through the finite element analysis (FEA) Autodesk Nastran-In-CAD software, within the Autodesk Inventor 2019 environment. To do so, a pressure load of 3 MPa distributed on the outer surface of an impeller blade was set (see Figure 6), corresponding to the highest prevalence of the pump during operation. The chosen mesh, as described in Section 2.2, is characterized by a total of 2767 nodes and 5325 elements. The FEA has shown that the concentration of stresses is localized in a vertex of the blade, as reported in Figure 9 as a representative case. Obviously, as expected, the concept model produced with the FDM technique in PET, with a yield strength of 54.4 MPa, is far from being able to have mechanical characteristics suitable for the stresses to which the component is subjected in service (i.e., around 547 MPa (see Table 7)). On the other hand, the model in AISI 316L stainless steel to be produced by using the SLM technology has shown resistance characteristics similar to the original product made of AISI 304 stainless steel sheet: the total displacement is 0.0335 mm for AISI 316L against 0.0833 mm for AISI 304 and 6.017 mm for PET, as reported in Table 6. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value/Type** \\ \hline Laser power [W] & 175 \\ Laser thickness [mm] & 0.05 \\ Scanning speed [mm/s] & 550 \\ Hatch distance [mm] & 0.1 \\ Argon Flow [L/min] 1 & 2.5 \\ Oxygen content [\%] & \textless{}0.1 \\ Scanning strategy & 67\({}^{\circ}\) rotating Meander Hatching Pattern \\ \hline \hline \end{tabular} \({}^{1}\) After filling the chamber and ensuring an oxygen content lower than 0.1%.  
\end{table} 
Table 6: Printing parameters adopted for the realization of the functional model made of AISI 316L stainless steel with the 3D SLM-based printer SLM500—SLM Solutions Group AG by ZARE S.r.l. 3D printing service. Figure 8: Support structure for the realization of the impeller by using the SLM technique. As shown in Figure 9a, it is evident that the stress is mainly concentrated on the top and bottom side of the blade, corresponding to the joint with the upper and lower flared parts, respectively (as expected). Moreover, according to Table 6, it is worth noting that for both AISI 304 stainless steel and PET, the Von Mises stress is greater than the corresponding yield strength (see Table 3), therefore suggesting a possible rupture of the part. However, even if this can be considered plausible for PET due to its very low yield strength, it should be reconsidered for the AISI 304 stainless steel, due to the real application of such a configuration in commercially available submersible electric pumps. In fact, this high stress can be due to many reasons (e.g., that the mesh and/or the model are not accurate) \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Material** & **Minimum Stress** & **Maximum Stress** & **Von Mises Stress** & **Total Displacement** \\  & **[MPa]** & **[MPa]** & **[MPa]** & **[mm]** \\ \hline AISI 304 & \(-626.4\) & 602.5 & 574.1 & 0.0833 \\ PET & \(-602.4\) & 574.2 & 546.7 & 6.0176 \\ AISI 316L & \(-306.7\) & 305.9 & 295.2 & 0.0335 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Main FEA results for the three materials adopted (i.e., AISI 304 from the original impeller, PET for the concept model to be printed with the FDM technique, and AISI 316L for the functional model to be printed with the SLM technique). Figure 9: FEA output for a single blade of the proposed impeller made of AISI 316L stainless steel sheet to be printed through SLM: (**a**) stress distribution (the maximum stress is on the bottom left corner); (**b**) total displacement. and should be reinterpreted.