As a core power component of an aero-engine, the processing accuracy of the aero-engine blade cooling system directly affects the thrust and service life of the engine.There are hundreds of cooling holes distributed on the surface of the blade.Due to the high-temperature and high-pressure environment they are in, these holes need to have extremely high dimensional accuracy and positional accuracy.
With its non-contact machining characteristics, the electric discharge machining (EDM) small hole drilling machine has achieved a number of technological breakthroughs in such precision hole machining and has become a key equipment in blade manufacturing.
Adaptive Innovation in Machining Processes
In view of the particularity of blade materials, the EDM small hole drilling machine has developed a gradient energy discharge process. Aero-engine blades mostly use nickel-based superalloys or single crystal alloys, and traditional drilling is prone to work hardening and cracks. By gradually transitioning the pulse energy from high-energy rapid erosion in the initial stage to low-energy finishing, it can not only improve the material removal efficiency but also reduce the depth of the heat-affected zone.
When machining the inclined small holes on the leading edge of the blade, adaptive feed control technology is adopted to adjust the electrode feed speed in real-time according to the discharge state, so as to avoid unstable discharge caused by the inclination of the blade surface, and control the axis deviation of the hole within 0.05mm/m.
To meet the requirements of complex hole shapes, innovative use of special-shaped electrodes and multi-axis linkage machining is adopted. In order to realize the diffused outlet of the cooling hole, a conical hollow electrode is designed to cooperate with the linkage of the Z-axis and C-axis. During the discharge process, through the composite movement of electrode rotation and axial feed, one-time machining and forming are achieved, avoiding the tool connection error in traditional step-by-step machining.
Targeted Upgrades of Equipment Functions
The innovation of the electrode guiding system has improved the stability of deep hole machining. The depth-to-diameter ratio of blade cooling holes often exceeds 20, and traditional single guides are prone to cause electrode vibration. The new EDM small hole drilling machine adopts a double guide structure, with guide devices set at the front and middle ends of the electrode respectively.
Cooperated with the forced chip removal of high-pressure working fluid (with a pressure up to 20MPa), the electrode can maintain straightness in deep hole machining. Aiming at the problem of insufficient rigidity of slender electrodes (with a diameter of 0.3mm and a length of 50mm), an automatic electrode straightening function has been developed. It detects the bending degree through laser and performs micro-correction, reducing the risk of breakage during machining.
The intelligent monitoring system realizes real-time control of machining quality. The infrared temperature measurement module integrated in the equipment can monitor the temperature changes of the electrode and the workpiece. When the local temperature is too high, it will automatically reduce the pulse energy to avoid micro-cracks in the blade material; online measurement of the machined hole is carried out through image recognition technology, which can feedback the aperture size deviation in real-time and automatically compensate the electrode feed. The application of these functions has improved the dimensional consistency of blade small holes by more than 40%.
Innovative Practices of Technology Integration
Combined with digital twin technology to optimize the machining scheme. Before machining, a digital twin is built through the 3D model of the blade to simulate the small hole forming process under different discharge parameters, predict possible machining defects and adjust the process parameters in advance. After an aviation manufacturing enterprise applied this technology, the trial production cycle of blade small holes was shortened by 30%, and the scrap rate was reduced to less than 1%.