Analysis of special-shaped machining of large titanium turbine blades

The length and size of the Silica Sol Precision Casting fan blades of a large bypass ratio turbofan engine basically reach more than 500MM. This large-scale structural feature makes the centrifugal force and vibration stress become very large during work, so it has also become a very important part of large turbofan engines. At present, many turbofan engines still use more mature titanium alloy damping fan blades. The narrow and long structure of the blade profile makes the rigidity of the thin-walled structure in the direction of the rear of the pot weaker. The rigidity of the structure is poor, the surface area of ​​the profile is large, and the nature of the material is difficult to process, which has an adverse effect on the traditional processing technology.

This is difficult to guarantee in terms of the outline dimension accuracy and position accuracy of the profile. The efficiency of manual polishing is low and the labor intensity is large. The leaf shape is easy to burn and ablate. For the machining of the outline of large titanium alloy fan blades, considering all the aspects involved in the traditional process, its adverse effects include the following aspects: The titanium alloy has a small elastic modulus, which is easy to cause clamping deformation of the blade processing; the side during machining The wear is easy to increase the cutting force. Low thermal conductivity, dry grinding by hand is easy to cause stress deformation, burns and ablation.

The overall processing area of ​​the profile is large, and the accuracy caused by wear is greatly affected during the entire tool process. Due to inconvenience in operation, manual polishing requires a lot of labor, and it is difficult to ensure the processing accuracy. Due to the influence of materials and specifications, it is difficult to obtain an ideal margin distribution, which will cause cutting force fluctuations due to uneven removal of the contour margin and stress deformation. The curved structure of the blade profile, the cutting direction of the tool, the actual cutting angle and the cutting parameters are different, resulting in changes in cutting force.

Poor heat dissipation conditions, insufficient heat dissipation and no heat dissipation will cause thermal stress deformation. In view of the difficult factors of surface machining of large titanium alloy fan blades, based on the comprehensive machining advantages of multi-axis linkage  machining technology, the main machining path determined is the blade tenon and the auxiliary positioning data. The machining blade contour CNC rough milling machining stress relief annealing positioning benchmark repair  blade milling contour finishing.The overall process idea established by the above process route is that the surface  rough machining removes most of the margin, and the precision milling process has an ideal margin distribution. The blade contour  precision milling process can ensure the geometry of the contour and the position accuracy is basically satisfied The final accuracy requirements of the blade; the finishing of the blade profile ensures that the quality of the profile surface layer meets the requirements.