An Investigation Into The Precision Micro-hole Enlargement By Using Electrochemical Grinding

Micro-holes are widely used in the high-tech products as a key structure, such as the instrument components of the inertial gyro, the aeroengine nozzle, and the film cooling holes of the blade. At present, micro-holes are mainly acquired by mechanical machining, non-traditional machining and hybrid machining. Electrochemical grinding(ECG), which is an interesting research, is one of the hybrid machining, and can produce the high quality micro-holes.The technology of machining the precision micro-hole by the electrochemical grinding was employed. The effect of the parameters by ECG on the accuracy and surface quality of the machined holes was discussed in detail. Research works were listed as follows:1. The ECG machining system was built, including the electrolyte circulation unit, electrolyte temperature control unit, and current acquisition unit.2. These parameters of electroplating composite coatings were analyzed. The wear resistance performance was tested by the UMT. The best optimized parameters(T=45℃; pH=4; sand: 90min, i=0.4A/dm~2; thicker: 180min, i=0.8A/dm~2) were obtained from the experiment. The high-quality composite coatings with these parameters were produced.3. Using the spherical grinding electrode with the high-speed rotation, the holes were machined in the 0.3mm thick stainless steel(1Cr9Ni18Ti) by the ECG experiment. The influence of the machining parameters on the machining quality was analyzed. By applying the optimized parameters, the high quality micro-holes with the average diameter of 0.611mm and the size repeatability precision of 18μm had been obtained. The holes with no burr, no fillet, and the surface roughness of 0.21μm were machined.4. Using the cylindrical grinding electrode with the high-speed rotation, the holes were machined in the 2mm thick stainless steel(1Cr9Ni18Ti) by the ECG experiment. A steady process with the machining speed of 30μm/s was obtained. The holes with good surface and steep sidewall were machined. The hole enlargement was 0.19mm, which was much greater than the general recast layer thickness.