Effect of secondary processing on EDM surfaces

A traditional practice in the die and mould making industry is to hand polish finally the part as a finishing operation irrespective of the type of primary machining process used in its manufacture (e.g. milling, electrodischarge machining, etc.). However, a possible alternative when die sinking using electrodischarge machining (EDM) is to electrochemically polish the surface. Hence, the surface resulting after the EDM process will be a combination of two processes (the former and the latter), and as a consequence the surface will reflect the way in which these processes interact with each other. The aims of this paper are to examine how the two processes in sequence affect the surface topography of the finished component, and to study the effects of the current density employed in the electro-chemical polishing process. The primary set of three-dimensional surface parameters recently revised at the University of Huddersfield was used as a basis to characterise the surface produced by the combined processes. The paper also illustrates which three-dimensional parameters are more sensitive to the machining processes variables, and which can therefore be used to characterise the results of the dual process.