3D surface characterisation of electropolished EDMed surface and quantitative assessment of process variables using Taguchi Methodology

The electro discharge machining (EDM) process produces surfaces that require some form of finishing operation. This is done in order to improve the surface texture and appearance of the component's surface. However, it is also desirable to remove the white uppermost recast layer (produced by the EDM process) so as to improve the functional performance of the surface. Electropolishing or electrochemical polishing (ECP) is one technique that is used mainly to improve the appearance of steels as well as for passivation of stainless steels. However, this process is very complex in nature, and it is not well understood how the different process parameters influence the surface integrity of the component in salt solutions. The aim of this paper is to present the results of a preliminary design of experiment of an EDM+ECP process sequence using Taguchi methodology. 3D characterisation of the surfaces has been done and ANOVA technique has been used to assess the quantitative influence of the different process factors of ECP. The results have shown that the direct current is the most dominant factor in modifying the surface texture, especially the S_q and S_m 3D parameters. The interaction effect between current and distance between electrodes is relatively important as compared to the individual effect of the latter variable.