Abstract
This paper uses ultrasonic energy transmitted to electrolyte to assist the dregs discharge in electropolishing of inner holes by different types of inserted and feeding electrodes recommended in the previous publication by authors. Six types of completely inserted electrode and the other six types of feeding electrode are connected with both continuous and pulsed direct current in the experiment of ultrasonic-aided electropolishing. The controlled factors include the chemical composition and concentration of the electrolyte, the electrolyte temperature, the flow rate of electrolyte, initial gap width, rotational speed of workpiece. The experimental parameters are the frequency and power level of ultrasonics rotational speed of electrode, current density and current rating, on/off period of pulsed Current, the electrode feed rate, and the electrode geometry. Both the use of pulsed current and ultrasonics can further improve the electropolishing. The average effect of the ultrasonics is more significant than the pulsed current while the machining time needs not to be prolonged by the off-time. The effect of using pulsed current in addition to the ultrasonic-aided electropolishing is limited. As in the previous study of simple electropolishing better polishing comes also from the electrodes with large discharge space. The geometry of electrode contributes the most to the improvement of surface finish, while the use of ultrasonics possesses the second place. Using the adequate electrode geometry as well as the ultrasonic aid, an effective and low-cost electropolishing of holes is presented.