Abstract
This research provides an electropolishing using low-cost electrode with high efficiency. It requires no expensive special-purpose equipment or high material removal as the conventional ECM does, it also dismisses the complex pre-polishing of workpiece in the soakage electropolishing. It offers fast improvement of the surface roughness of workpiece and is a new area in electropolishing.In order to elevate the efficiency of the electropolishing on die materials and parts, i.e. to reach the fast improvement of the surface roughness of the workpiece, so as to reduce the residual stress on the surface efficiently, the present study discusses the surface roughness of several common die materials after traditional machining, of which the internal and external cylindrical surface are electropolished by different types of electrode design. The research is expected to provide the best design of electrode, which will help widen the application in the future. For the electropolishing of internal holes, completely inserted and feeding electrodes are connected with both continuous and pulse direct current. The external electropolishing studies the design of turning tool electrode, arrow-head electrode, ring-form electrode, and disc-form electrode. The controlled factors include the diameter of the electrode, the chemical composition and the concentration of the electrolyte. The experimental parameters are electrical current density, current rating and pulse period, electrode design, die material, workpiece and electrode rotational speed, polishing time, and electrode feed rate. For the internal electropolishing, the electrode with helix discharge flute performs better than that without flute or with straight flute. The electrode of borer type performs better than that with a lip on the leading edge. Pulse direct current can improve the polishing, but the machining time and cost are increased. The electrobrightening after reaming needs quite short time to make the hole bright, while the electropolishing saves the need for reaming, making the total process time less than electrobrightening. For the external electropolishing, Smaller nose radius or end radius produces higher current density and provides faster feed rate and better polishing effect. The electrodes with large discharge flute and large flute rake angle, small taper angle, or smaller cross-section are associated with larger discharge space, thus polish better. The disc or ring electrode with pins attached on edge performs the best of external electropolishing. The fluted or pin-type electrode will be incorporated into the design for an equivalent effect of using pulse current. Ultrasonic aided electropolishing elevates the polishing effect and the machining time is not increased.