Polishing process of titanium alloy blade edges using bonded-resin diamond tools

Objectives: Aero engine blades are important components in engines, and the machining accuracy of the blade edge directly affects the aerodynamic performance of the blade. Improving the surface roughness and the profile accuracy of the blade edge are crucial to improving the service life and the performance of the engine. However, the curvature radius of the blade edge surface varies greatly to even less than 0.05 mm, which puts higher requirements on processing equipment and technology. Therefore, the polishing process of blade edges is studied and a fixed resin diamond elastic polishing wheel adapting to the shape of the blade edge is developed to explore its feasibility on a 6R robot polishing platform when polishing blade edges. Methods: The fixed resin diamond elastic polishing wheel is developed based on the characteristics of small curvature radius and complex surface shape of the blade edge, and a robot polishing platform is built to study the polishing process of Ti alloy blade edges. Firstly, by combining UG secondary development with robot kinematics, the polishing path of the wheel based on the robot platform for polishing blade edges is planned. Secondly, the orthogonal experimental method is used to explore the influences of four main process parameters, namely spindle speed (A), feed rate (B), machining pressure (C), and abrasive particle size (D), on the surface roughness and contour of the blade edge. The optimal combination of process parameters is then obtained. Finally, the titanium alloy blade edge workpiece is polished using the optimal parameter combination, and the surface roughness and the contour of the workpiece after polishing are measured to determine whether the polishing quality of the workpiece meets the requirements for use. Results: The orthogonal experiments are conducted on titanium alloy blade edge polishing using the fixed resin diamond elastic polishing wheel on the 6R robot polishing platform. The experimental data show that: (1) Among the four process parameters A, B, C and D, B has the greatest impact on the blade edge profile with a range R₁ of 0.015. The second greatest influences are from A and C, and the least influence is from D. The optimal combination of process parameters is A₂B₁C₂D₃, that is, the spindle speed is 700 r/min, the feed speed is 6 mm/min, the processing pressure is 4 N, and the abrasive particle size is 10~14 μm. (2) B has the greatest effect on the surface roughness of the blade edge, with its range R₂ being 0.136, which is much higher than that of other parameters. The second greatest influences are from D and A, and the least influence is from C. The optimal combination of process parameters is A₃B₁C₂D₃, that is, the spindle speed is 800 r/min, the feed speed is 6 mm/min, the processing pressure is 4 N, and the abrasive particle size is 10~14 μm. Conclusions: A new type of resin diamond elastic polishing wheel is innovatively designed by combining fixed abrasive technology and elastic polishing technology, which is suitable for the characteristics of large curvature changes and complex surfaces of the blade edge. It is used for orthogonal experiments of blade edge polishing on the 6R robot polishing platform. The experimental results show that the designed and developed elastic polishing wheel is suitable for polishing the edges of titanium alloy blades, and the surface roughness and profile accuracy of the processed edges can meet the requirements for use. At the same time, the optimized process parameter combination for polishing the edge of titanium alloy blades is A₃B₁C₂D₃, which includes a spindle speed of 800 r/min, a feed rate of 6 mm/min, a processing pressure of 4 N, and an abrasive particle size of 10～14 μm. Under these parameters, the overall effect of blade edge polishing is the best, with the surface roughness R_a decreasing from the initial 1.165 μm to 0.213 μm, and the profile decreasing from the initial 0.048 mm to 0.016 mm.