## 4 Conclusions  
This work aims at proposing and demonstrating a reverse engineering-based approach in order to reproduce the impeller of a submersible electric pump by using the selective laser melting 3D printing process.  
First, a traditional manual measurement (i.e., through caliper and micrometer) for the evaluation of the actual dimensions of the impeller was adopted.  
Then, after reconstructing the 3D model by modifying the thicknesses of the flared parts of the impeller and of the hanging between the blades and the flared parts, a finite element analysis was been carried out. The goal was to verify the suitability of both the proposed material (i.e., AISI 316L stainless steel instead of the AISI 304 stainless steel of the original impeller) and technology (i.e., SLM against sheet lamination and welding, for the final application). To this end, a pressure load of 3 MPa, which represent the highest prevalence of the pump during operation, was considered.  
Before printing the functional component by SLM, a concept model was produced through the fused deposition modelling technique by using PET material in order to verify the applicability on the pump axis and in the diffuser seat.  
The service ZARE S.r.l. has been used to produce the functional component by using the SLM technique. The biggest issue here was the use of a massive amount of support structures that need expensive post-production processes to be removed. Moreover, surface roughness is still a limit of the technology, with measured values of around 8.5 \(\upmu\)m, requiring other post-processing operations and further increasing the final cost of the product.  
Conversely, the SLM printing process allows the fabrication of highly-accurate geometries by ensuring the compliance with the imposed constraints of \(\pm\)0.1 mm on the blade tolerances with respect to both the original and the CAD models. In fact, the absolute error evaluated for the various thicknesses is 1% for the blades and the upper flared part, while it is around 3% for the lower flared part.  
The topographic optimization involved the reduction of the blades' thickness from 1.60 mm to 1.30 mm, the full densification of the upper flared part and the increase in the thickness of the lower one from 1.82 mm to 1.90 mm in order to guarantee a greater resistance of these sections and therefore the success of the SLM printing process. As a result, the 3D printed pump impeller has a more robust design, allowing one to operate at higher speed while maintaining the same stress and therefore generating increased head. Moreover, an increased volume available for the fluid flow is obtained, thus ensuring a higher flow rate, which can lead to an increased pump efficiency.  
Therefore, the SLM additive manufacturing technique allows for obtaining components with improved mechanical performances (i.e., hardness and tensile strength), if compared with the traditional laminated sheets, and the complete freedom to create complex objects in a single production process, capable of creating a pump perfectly suitedto the customer's needs with an undisputed positive impact on efficiency and energy consumption of the product.  
The next step will be the use of the produced impeller under operating conditions in order to verify its actual suitability for the applications for which the submersible electric pumps are intended.  
Conceptualization, G.S.P., O.G., and S.G.; methodology, G.S.P.; software, M.H.; validation, G.S.P., F.T., and S.G.; formal analysis, G.S.P. and M.H.; investigation, G.S.P. and M.H.; resources, M.H.; data curation, G.S.P., F.T., and S.V.; writing--original draft preparation, G.S.P., F.T., and S.V.; writing--review and editing, G.S.P., F.T., S.V., M.H., O.G., and S.G.; supervision, O.G. and S.G. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The authors gratefully acknowledge [PERSON] for the technical support.  
The authors declare no conflict of interest.