Improving Geometric Accuracy in Multi-Axis Machining of Thin-Walled Turbine Blades: Practical Methods for Minimizing Error and Online Compensation

This study aims to achieve the required geometric tolerance in the machining of the contact face surfaces on thin-walled rotary steam turbine blades to meet strict assembly requirements. The focus was on recognizing and reducing random errors contributing to dimensional deviation. Two methods were considered: (1) creating a U-notch at the end of the blade to relieve residual stress and bending forces due to fixture, tailstock system, and raw block misalignment, and (2) an online measurement and compensation method to estimate and correct elastic deformation during machining. Experimental tests on two five-axis CNC machining centers and finite element simulations were used to evaluate the impact of these methods. The results show that the U-notch method reduces the standard deviation and deviation range by approximately 37% and 42%, respectively, but the deviation range still exceeded the acceptable tolerance (0.09 mm > 0.06 mm). However, the online measurement and compensation method reached remarkable improvements, reducing the standard deviation by 71% and 78%, and improving the mean deviation by 76% and 97%, bringing the blade tip deviation within the acceptable tolerance range (0.028 mm, 0.045 mm < 0.06 mm). This technical study reveals the effectiveness of online compensation techniques as a highly efficient solution for reducing post-machining deformation and ensuring dimensional accuracy in turbine blades without extra operations such as grinding or fixture redesign. This practical method can be easily implemented in workshops, simplifying production processes and reducing costs.