Devising a methodology for prototyping convex-concave parts using reverse-engineering technology providing the predefined geometric accuracy of their manufacturing

The object of this paper is the geometric accuracy of the acquired portrait from the 3D printed full-scale sample in the reduced size of the convex-concave parts compared to the correspondingly reduced ideal one. The subject of research is reverse engineering and additive technology for manufacturing convex-concave parts for mechanical engineering (ME). A new prototyping methodology for convex-concave parts of mechanical engineering objects has proposed. Underlying the methodology is the use of the scaled (by reducing in size) ideal portrait of the 3D scanned original part. The decision to start the production is made by comparing the geometry of the portrait acquired from the 3D printed sample in reduced size with the ideal one, provided that the values are within the tolerance range. The following results were obtained. A design and technological analysis of the blade of the pumped hydroelectric power station was performed, after which a 3D scanner and a 3D printer were selected. A 3D scan of the blade with the formation of a portrait in the STL format file was implemented, as well as its refinement into an ideal one. From the geometric features and shapes of the blade, as well as the technical characteristics of the 3D printer, the percentage of reducing the sample for printing (by 75 % of the original dimensions) was calculated. According to the rated dimensions of the original part and the reduced sample, the tolerance field was set for the size: 0.6 mm and 0.25 mm, respectively, at 12 quality of the part’s manufacturing accuracy. Inspection of the printed sample and comparison with the correspondingly reduced ideal portrait revealed a deviation from –0.123 to +0.120 mm, which is within the defined tolerance field for the manufactured reduced sample. The results of experimental studies confirmed the adequacy of the proposed methodology for prototyping the mechanical engineering parts and verified the theoretical foundations of reverse engineering for convex-concave parts of any large size by using a proportional reduction in the size of finished portraits