Wärtsilä (Netherlands)

Abstract This article describes the manufacturing of ship screw propellers. A fixed pitch propeller (FPP) and different parts of a controllable pitch propeller (CPP) are made by casting and subsequent machining. The most commonly used material is NiAl‐bronze, although also stainless steel is used. Based upon a casting design, a sand mold is made and the liquid metal is poured into the mold. After solidification, the part is taken out of the mold and a visual check is made before the rough casting is measured. An intermediate balancing and dye penetrant investigation is made after pre‐grinding of the casting. If any casting defects are present and permitted to repair, these are repaired before final grinding and polishing. Grinding and machining techniques, including NC simulation, are described for the different parts of the propeller. The final product must meet the specified dimensions within the allowed tolerances. Depending on the purpose of the vessel, a different (tighter) tolerance class than ISO 484 may apply.