Structure Design Of Machine Tool And Study On Tool Electrode Wear For EDM & ECM Hybrid Machining Of Micro Hole

As key parts of aero engine, turbine blades always use film cooling holes to improve cooling efficiency, and increase the inlet temperature of turbine, leading to the improvement of the engine's thrust weight ratio. There are numerous small cooling holes on the turbine, and the holes should be machined with high efficiency and good surface quality such as no recast layer, no micro cracks, so it is difficult for the traditional machining methods to meet the processing requirements. EDM & ECM hybrid machining is a kind of machining method which is utilizes the advantages of high machining efficiency of EDM, and combined with the advantages of no recast layer of ECM.In this paper, the mechanism and process of the EDM & ECM hybr id machining of cooling hole was studied. Firstly, the machine tool's main structure was designed, which contains 7 axes. Secondly, the main moving parts were checked, the composition of working fluid circulation system and control system were considered. The main technical standards of the machine tool were given. After that, the EDM & ECM hybrid machining processing technology and the influence of different machining parameters on tool electrode wear w ere studied. The experiment indicates that the EDM & ECM hybrid machining can significantly reduce tool electrode wear. This paper main research contents are as follows:(1) Machine tool of EDM & ECM hybrid machining was designed. The machine tool has 7 moving axes, containing X, Y, Z, S linear motion axes, B, C and R rotation axes. The main design work of machine tool inc ludes two parts. Firstly, the machine tool's main structure, mode of transmission and working liquid cycle system were designed. Secondly, the theoretical calculations and verifications of machine tool drive system including linear guide, ball screw and servo motor were given.(2) Single factor experiments were carried out to explore the inf luences on the tool electrode wear and material removal rate of electrical parameters(pulse width, pulse interval, peak current) and non-electrical parameters(diameter of the electrode, working fluid pressure). The tool electrode wear were studied under different process conditions and the process parameters were optimized to reduce the tool electrode. The influence of dissolution concentration on electrode wear was also studied, and the reason of low tool electrode wear with EDM & ECM hybrid machining was analyzed. In the end the tool electrode relative wear under different dissolution concentrations was calculated and the rule of the tool electrode wear was obtained.(3) Experiments of EDM & ECM hybrid machining for micro holes under different working fluid concentration were carried out in the paper. The influence of fluid concentration on the hole's inlet and outlet quality, hole taper, thickness of recast layer, material removal rate etc. Using optimized experiment parameters, small hole machining exper iments were carried out, the holes with good morphology, better processing efficiency and almost no recast layer were obtained.