Electropolishing of cylindrical workpiece of tool materials using disc-form electrodes

This research presents a new application of electropolishing using a low-cost disc-form electrode offering fast improvement of the surface roughness of SKD61. It requires no expensive special-purpose equipment or heavy material removal as conventional electrochemical machining does, and it also avoids the complex pre-polishing of the workpiece before the electropolishing. Round bars or round tubes produced by traditional turning, drawing, form rolling, or extrusion, can be successively electropolished using the designed disc-form electrodes. Five electrode designs are discussed. The experimental parameters include rotational speed of workpiece, electrical current rating and pulse period, electrode geometry, and electrode feed rate. Thinner disc and larger disc taper angle are associated with larger discharge space for the electrode, thus the polishing is more effective. A smaller end radius of the disc electrode produces higher current density and provides faster feed rate and a better polishing effect. A disc with discharge flute performs better, and larger flute back rake angle, side rake angle, wider flute, and deeper flute depth are also advantageous. Although the use of pulsed current slightly outperforms the fluted electrode using continuous current, it sacrifices both machining time and cost. The best electrode design is identified. A guideline for the design of electrodes is provided based on the experimental results.