On the manufacture of naval propellers by using self-hardening sand molds made by robotic arms

This work presented the versatility of the manufacture of naval propellers through machined self-hardening sand molds by an ABB®; robotic arm using computer-aided design programmed trajectories with a model that included an oversize of 4.5 mm in blade thickness. The results indicated a compressive strength for the sand hardener resin mix (3.5% resin and 8.5% hardener) of 9.94 ± 0.18 kN. The visual inspection did not reveal cracks, porosity, misruns, or other superficial defects that could affect the propeller’s integrity. The comparison between the three-dimensional model and measured blades was 12 to 16% (including shrinkage of 2 to 5%). Also, the as-cast propeller showed variations ranging from 6.66 to 8.30 mm in comparison to the desired thickness of the finished parts. The mechanical properties, microstructure, and chemical analysis results indicated that the molten alloy was Ni-Al bronze within C95800 specification.