Research On Electrochemical Deburring Of Miniature Holes

Miniature holes with diameters less than lmm are increasingly wide utilized in such fields as automotive, biomedical, nuclear industry, aeronautics and astronautics, etc. Mechanical drilling can fabricate miniature holes with great depth-diameter aspect ratio, excellent roundness, high dimensional accuracy and surface quality at low cost. However, burrs will generate along the edge of the drilled holes, which severely affect the part accuracy, quality and performance. Recently, removal of burrs of the miniature holes is still technically immature. Electrochemical deburring (ECD) has been found as a potential solution to remove burrs of miniature holes due to its advantages, such as no physical contact between tool and workpiece and the tool is apt to be miniaturized. So, controllable removal of burrs of miniature holes on precision parts, especially for complex shell or tube parts, which burrs exist on the inner surface, by electrochemical method, was researched in this thesis.In order to well control the electrochemical deburring of miniature hole (M-ECD) operation, mathematical model for M-ECD was developed to evaluate the effect of various parameters, e.g. machining time, diameter of miniature hole, initial burr height and current on the deburring quality. M-ECD tests were carried out at different currents to remove burrs of different diameters miniature holes drilled on aluminum and stainless steel plates respectively. The experimental results were in good agreement with the predictions based on the developed mathematical model, which shows that the developed mathematical model enabled the deburring result to be more accurately predicted. M-ECD operation with processing parameters calculated by the developed mathematical model was performed, which successfully removed the burrs of the miniature holes drilled on aluminum plate.For removing burrs by M-ECD will result in severe stray corrosion, Pulse electrochemical deburring of miniature holes (M-PECD) was put forward. A high frequency pulse power for M-PECD was developed, which can achieve very stable output impulse current with frequency5KHz to5MHz, duty cycle20%to60%, voltage Ov to60v, current0A to1A. Pulse electrochemical corrosion tests on aluminum and stainless steel plates by using the developed pulse power were performed and M-PECD tests to remove burrs of different diameters miniature holes drilled on aluminum and stainless steel plate were conducted. The results show that M-PECD can evidently reduce stray corrosion which decreases with the decrease in duty cycle and the increase in frequency. Different frequencies correspond to different optimum duty cycle range, and the higher the frequency is the larger the optimum duty cycle is. For M-ECD processing time can’t be calculated by the developed mathematical model if the geometric parameters of the burr are unknown, which will make the M-ECD operation beyond control. Tests were conducted to investigate the changes of the fountain phenomenon and the interelectrode current and voltage during M-PECD processing. The results show that the interelectrode current decrease gradually when process with constant voltage, and the interelectrode voltage increase gradually when process with constant current. For the miniature holes with the same diameters, the interelectrode current or voltage differ greatly at the beginning of M-PECD, but tend to certain particular range with the processing. The fountains heights increase with the M-PECD processing, but keep constant when the burrs were completely removed. Taking the variation laws mentioned above as the judgment basis of M-PECD processing state, the burrs of the miniature holes on tube parts with geometric parameters unknown were effectively removed.