An Experimental Comparison on Dimensional Accuracy of Wax Patterns of Gas Turbine Blades Produced by Rapid Tooling

Abstract

The primary objective of this research is to determine the accuracy of a typical turbine blade wax pattern that includes common areas (such as root, platform and airfoil) in all turbine blades, which are produced by soft tooling room temperature vulcanization (RTV) mold methods, epoxy molds and silicone rubber molds and also to compare them. It is necessary to use the optimum parameters of injection within the molding in order to obtain sufficient dimensional accuracy of wax patterns. Considering the current study, it can be concluded that the epoxy mold can produce more accurate models than the silicone rubber mold. In addition, the range of dimensional variations in different directions of the wax patterns was achieved. Average shrinkage percentage is equal to 0.6 and 3.5 % in the direction along the length and width of the root in output patterns from silicone rubber mold, respectively. It is equal to 0.6 % approximately perpendicular to the platform in the direction of the airfoil. However, the average shrinkage percentage is 1.1 and 0.6 % in the direction along the length and width of the root in output patterns from epoxy mold respectively, and is almost 0.6 % perpendicular to the platform in the direction of the airfoil. These studies will help those who use both rapid tooling and investment casting in the production of turbine blades to estimate the changes required for initial CAD drawings to produce a final casting with minimum dimensional inaccuracy.