Layout optimization method for core holders in wax pattern mold of hollow turbine blade

Abstract

The wall thickness is one of the major factors affecting the aerodynamic performance of a hollow turbine blade. Its precision is mainly inherited from the wall thickness of the corresponding wax pattern. However, because of the complexity of the wax injection, it is always difficult to design a holder layout that can localize and immobilize the ceramic core in wax pattern mold, which results in the wall-thickness deviation of the wax pattern. To solve this issue, an optimization method for the layout of the core holders in the wax pattern mold is proposed in this paper. Firstly, based on a locating error transfer model and some equilibrium equations, an optimization method for the layout of locating pins is established. By utilizing it, a locating layout with high localization accuracy and stability can be obtained. Secondly, by taking the form-closure criterion and the normal contact forces between the ceramic core and core holders as constraints, an optimization method for the layout of clamping pins is developed. In addition to fixing the ceramic core with a minimum number of clamping pins, the method can prevent the ceramic core from being crushed by core holders. Then, considering the force exerted on ceramic core by the melted wax is a crucial input in the clamping layout optimization, a force prediction method is also proposed based on numerical simulation. Finally, a case study is presented to illustrate the effectiveness of the proposed method.