This paper reviews the development of high-efficiency and low-cost electrode for electro-chemical drilling and electropolishing of holes. Holes are major feature in die and mold. The design logic chart of the electrodes to address the major technical issues is presented, along with the electrode shapes and the representative experimental results. For the electrochemical drilling, it is concluded that a slow relative rotary motion between the electrodes helps to produce the machined profile of better quality. During electrochemical drilling, the use of bit type of tools produces more accurate holes as compared to bare type of tools. Comparing the anode corner profiles computed by cosine method and feed rate interpolation with the experimentally obtained anode corner profiles, one realizes the design of the cathode shape to achieve a required anode shape is a primary concern in electrochemical drilling. For the electropolishing of holes, the completely inserted, feeding, and rib plate electrodes are connected with continuous direct current. The controlled factors include the diameter of the electrode, the chemical composition and the concentration of the electrolyte. The experimental parameters include electrical current density, current rating, electrode design, die material, rotational speed of electrode, polishing time, and electrode feed rate. The completely inserted electrode with helix discharge flute performs better than that without flute or with straight flute. The feeding electrode of borer type performs better than that with a lip on the leading edge. The rib plate electrode of single rib plate on one side with slant discharge flute has more space for dregs discharge and also reduces the secondary machining, thus performs the best polishing.
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