The term âadditive manufacturingâ? encompasses many technologies; 3D Printing, Rapid Prototyping, Direct Digital Manufacturing, layered manufacturing and additive fabrication. All of these technologies are utilized to create an object by adding material layer-upon-layer, whether plastic, metal, concrete, or other materials.
Gabbioneta was looking for a suitable way to manufacture impellers properly designed and validated through Computational Fluid Dynamics but which were not practically feasible with traditional methods. After experimenting with plastic prototypes components, Gabbioneta discovered that additive manufacturing is not the cure of all ills. Despite theory, not all the CAD models can be simply converted into an object; there are geometrical constrains and limited materials available.
Gabbioneta selected F3184, one of the poorest materials currently available, formally equal to 316 stainless steel. To prove and reinforce the equivalence between the two materials, many comparisons were necessary, both in terms of tensile and fatigue proprieties and the results were very good.
Despite the additive material not being isotropic, the mechanical properties proved better when compared to casted material. Also, yield strength was up to 40% better with a comparable ultimate tensile strength, and fatigue resistance was significantly improved regardless of the application direction of the loads.
The additive manufacturing impellers have geometries identical to the theoretical one with a high level of repeatability. The nature of the layer-upon-layer process leaves a stepped surface that needs to be polished to insure the best pump efficiency. So the complete process of additive manufacturing, machining, and polishing insure a high quality stainless steel impeller within the dimensional range currently feasible.
Based on the impellers produced through additive manufacturing, the process has been validated and can be used for impellers with very narrow channels, which generate significant design advantages. The process can also be used to replicate parts whose patterns are not available, and because of the reduced lead time, parts can be produced quickly with substantial cost savings.
