Research On Electrochemical Micro-machining System And Key Techniques

Electrochemical machining (ECM) is an anodic dissolution process of workpiece in a flowing electrolyte where the shape of the tool as cathode is copied into the workpiece as anode with the removal of the anode ion by ion. Due to the tiny size of metal ion, this micro-dissolution process brings ECM tremendous potential in the micro-manufacturing field. It will be great significance to thoroughly grasp micro ECM core techniques and develop micro ECM system to fabricate microstructures with the meso size(from a few microns to a few hundred microns)which exists widely in industry. A new micro ECM set-up is developed independently by the author. Double vertical column Π style-C style hybrid structure is chosen as the main mechanical structure, which has the advantage of excellent structure rigidity, compact framework dimension as well as good maneuverability and maintainability. Rotated Z-axis and feeding C-axis is designed to function synchronously, leading to a wider scope of machining objective, like as 3D spiral groove structure. To eliminate the radial pressure imposed on the rotated shaft by the carbon brush and realize good electrical Conductibility, the symmetrical double carbon brush is adopted in the system. Integrated bearing block unit is introduced to weaken the shaft strain from the outer force and henceful improve the rigidity of the machine structure. The author independently develops a half-closed loop control system based on the PCI-series bus motion controller. The control software is programmed by LabVIEW graphic language. Considering the characteristics of micro ECM, the feedback of machining current, variation rate of machining current and variation rate of voltage is used to control inter-electrode gap. The precise tool positioning in the electrolyte is realized by using low voltage. Different servo motion method, including feeding at constant speed, feeding with periodic tool positioning and feeding with periodic drawback, is developed. The whole control system fulfils the requirements of control in micro ECM. The research on how micro ECM process influences the machining accuracy and product quality is important. With the developed micro ECM system, the rotated micro spiral cathode is used in experiment and the result shows that the higher machining speed, better process stability and better roundness of the microhole are achieved. Besides, the impact of motion feeding method, electrolyte, electrical parameters and electrodes fixing mode on the machining accuracy and process stability is investigated. Results indicate that the combination of the additive, pulse current and feeding with periodic positioning could significantly attribute good machining quality in micro ECM. The slice cathode and wire cathode is advanced in microgroove ECM, and the comparison of their influence on the shaping accuracy and process stability in microgroove ECM is compared. Based on the above research results, the ECM of certain radiate mluti-microgrooves structure is studied as an application exaple, by the author independently. Special unitary cathodes, corresponding fixing clamps and the flow field distribution is designed and optimized. Combining with the optimal process parameters, the multi-microgrooves structure with groove width of 0.27±0.02mm is machined stably and efficiently. The good uniformity of the microgrooves is achieved.