Development of Rapid Tooling for Investment Casting of Turbine Blade and Its Quality Inspection

Abstract

Rapid prototyping (RP) technologies have played a vital role in different stages of product development process. One other aspect of RP is Rapid Tooling (RT). RT is the technique through which tool is developed in less time for limited quantity of production through RP technologies. Generally there are two approaches for RT, direct tooling and indirect tooling. In the case of direct tooling, the shapes are developed directly using a RP system, however in the in-direct tooling, a pattern is required to start the development process. In both these methods, application of rapid prototyping has central role. Rapid tools give advantages of getting the production tool ready in less time for small batch production. Time to market concept is very much supported by RT. From two methods of RT, the in-direct tooling method was selected for this research work. The part selected for this case study was a turbine blade. The reason for selection of this shape was that a turbine blade has different types of features i.e profile with variable thickness, flate faces and profiled feature with uniform thickness. As the master pattern is required for in-direct process, SLA and FDM techniques were utilize for making of this master pattern. Both the patterns were quality inspected and surface finish was measured. With good accuracy and high surface finish, SLA pattern was selected for the process. After selection and making of pattern, three different rapid tools were developed in different materials, i.e. Room Temperature Vulcanized (RTV) Silicone, PolyUrethanes (PU), and Plaster. Wax patterns were produced from these three developed rapid tools and quality inspection was conducted. Silicone tool produced better results because the casting was done under vacuum and packing of mold was better than other two. Polyurethane mold gave larger quantity of shots for wax pattern as compared to Silicone mold but accuracy was lower than the Silicone mold. The Silicone mold showed an overall better result on basis of quality inspection.