Abstract: In order to solve the worldwide difficult problem of how to machine closed integral structure made of difficult-to-cut material, a new process of combined electrical machining is put forward and studied, that is an organic combination of numerically controlled electrochemical machining (NC-ECM) and numerically controlled electrical discharge machining (NC-EDM). As an example of trial processing of several typical closed integral structures, its overall technological scheme and main key technologies are discussed, including the design of auxiliary apparatus, electrode and its moving tracks based on digital technology, the computer simulation of combined electrical machining, the working areas partition of integral structure and the arrangement of technological parameters and machining allowance among the processing procedures. Combined with tackling key manufacturing technology of closed integral structure, the machining scheme is verified and improved through technological experiments, and qualified closed integral structures are machined finally. Then, the machinability problem of typical closed integral structure is solved, and the machining efficiency can be improved by above 40% compared to the use of NC-EDM alone, at the same time, the electrode wear can be reduced effectively. With the increase of production lot and the deepening of technological experiments of NC-ECM, there is ample room for improving overall machining efficiency. The above research achievements have been successfully used in the development of new aero-engines, airspace engines and turbo-machines, thus promoting the development of manufacturing technology of closed integral structure.

Key words: Closed integral structure, Combined electrical machining, Electrical discharge machining, Electrochemical machining, Numerical control