Influence of metal vapor jets from tool electrode on material removal of workpiece in EDM

This paper shows that the radial flow caused by the collision of the metal vapor jets generated from the surfaces of the tool electrode and workpiece serves as one of the material removal mechanisms in electrical discharge machining (EDM). Material removal per single discharge of a steel workpiece was larger using the tool electrode made of materials with lower boiling point. Observation of the discharge gap using a high-speed video camera showed that molten material on the workpiece was swept away more significantly and larger amounts of debris was removed using the tool electrode materials with lower boiling point. The molecular dynamics simulation showed that the radial velocities of the vapor atoms removed from the workpiece were higher using the tool electrode with lower boiling point because the jets from the tool electrode were more intensive. Furthermore, the discharge reaction force acting on the wire electrode in a single pulse discharge in air was measured from the wire vibration. The results showed a larger discharge reaction force using a zinc coated brass wire compared with a non-coated wire. Thus, it can be concluded that the shear force caused by the jets serves as one of the material removal mechanisms in EDM. Furthermore, one of the reasons for the higher material removal rate obtained using zinc coated wire electrode in wire EDM is the ease of boiling of the zinc coating layer on the wire surface.