Molds surface finishing with new EDM process in air with thermoplastic composite electrodes

This paper presents a variant of the standard die sinking EDM process, where a thermoplastic composite electrode, instead of solid graphite, is used to perform fine EDM finishing using air as dielectric medium. A detailed description of this distinctive EDM method is provided, where the complementary surface roughness of a compression molded polymer composite electrode is used in order to reduce iteratively the corresponding surface roughness on the workpiece. The use of a thermoplastic composite electrode with air instead of water or oil as dielectric medium is rationalized and a proof of concept is presented, where the peak-valley surface finish of a rough machined P20 tool steel part is iteratively flattened by 30 μm over three thermoplastic composite electrode forming, and EDM process cycle.