Reducing the geometrical machining errors incurred during die repair and maintenance through electric discharge machining (EDM)

The importance of geometrical accuracy can never be overruled in dies and molds which governs the dimensional precision of the parts being manufactured. The continuous use of such tooling requires repair and maintenance. Among the different processes used to upkeep the dimensional consistency of the tooling, machining is essentially required in most cases. The intricacy of the dies and molds' cavities requires the use of electric discharge machining (EDM). However, in EDM it is challenging to develop control over the machined dimensions owing to the inherent issues of overcut/undercut. This aspect was not comprehensively investigated so far which is the core focus of this research. Three electrode materials, namely, copper, graphite, and tungsten carbide, which belong to the category of metals, nonmetals, and ceramics, respectively, have been compared for the said perspective on the comprehensive list of parametric variables. The results revealed that the average value of the axial errors is 2.5 times lesser in comparison to lateral dimensional errors. In the case of lateral dimensional errors, the electrode of graphite has proved to be a promising choice in comparison to the other two types of electrode materials, namely, copper and tungsten carbide. The copper electrode is noticed to be the most appealing option for reducing axial error (A.E). The mean A.E obtained with Cu electrode is 80.9% and 47.6% lower than that achieved in case graphite and tungsten carbide, respectively. Furthermore, the optimal parametric combination based on 7 variables has also been proposed using desirability analyses whose validity is proved during confirmation trials.