Design of rib plate of electrode in electrochemical smoothing and electrobrightening of large hole

Abstract

This study discusses the improvement of surface finish of medium or large holes beyond traditional drilling, boring, rough turning, or extruding by electrochemical smoothing using inserted rib-plate electrodes. High electrical current is not required when the rib plate is used to reduce the engaged area for large hole. Traditionally, the hole polishing requires a sequence of complicated premachining or scarce manual skill. In the current experiment, six types of electrode are completely inserted and connected to both continuous and pulsed direct currents. The controlled factors include the chemical composition and the concentration of the electrolyte, and the diameter of the electrode. The experimental parameters are the current density, on/off period of pulsed current, rotational speed of electrode, and the electrode geometry. For the inserted electrodes, a thin rib plate with small wedge angle towards the root of the plate provides more sufficient discharge space, which is advantageous for polishing. The electrode of single plate performs better than the double-plate electrode. The electrode of a single plate with slant discharge flute performs the best polishing effect. Pulsed direct current can slightly improve the polishing effect at the expense of increased machining time and cost. It was also found that electrobrightening after reaming or precise turning uses quite a short time to make the hole bright, and the electrochemical smoothing saves the need for reaming or precise turning, making the total process time less than the electrobrightening.