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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. [ABSTRACT FROM AUTHOR]

Dimensional deviation is a prerequisite for improving the manufacturing process of parts with free-form surfaces, for example, the reverse adjustment of the die cavity of turbine blade. Influenced by random noise of the manufacturing process, dimensional variation is inevitable for batch parts. Therefore, it may cause unacceptable error to estimate batch parts dimensional deviation by a single sample. Meanwhile, the optimum sample size for estimating dimensional deviation is difficult to determine. To overcome this problem, a practical method for estimating of dimensional deviation of parts with free-form surface is proposed. Firstly, displacements of the discrete points on part surface are employed to represent dimensional error of the part. Estimating dimensional deviation of parts is actually to estimate the simultaneous confidence intervals of the discrete point displacements. Secondly, Bonferroni simultaneous confidence intervals are adopted to estimate the confidence intervals of the part dimensional deviation. Moreover, the accuracy of the estimation will be continuously improved by increasing samples. Consequently, a practical dimensional deviation estimation method is presented. Finally, a compressor blade is adopted to illustrate the proposed method. The percentage of estimation error of the blade dimensional deviation that is less than 0.05mm, which is the estimation error limit, of all the 100 times sampling experiments is 99%, exceeding the given confidence level of 95%, while the percentage of the existing method is below the confidence level, only 87%. [ABSTRACT FROM AUTHOR]