In micro EDM drilling, particular attention should be made to characterize the hole not only from a macro and micro geometric point of view but also as regards the integrity of the internal surface of the hole. The analysis of the internal surface of micro EDM holes is the aim of this paper. Micro holes were executed on the interface line of two coupled titanium sheets in order to have free access to the internal surface after the drilling operation. The effects of the type of machining (roughness or finishing) and the effects of the washing pressure through the internal diameter of the electrode on the internal surface of the hole were investigated. The analysis was conducted by SEM images, observation of the craters size and the measurement of the surface roughness. Finally, EDS analyses on both the workpiece and the electrode tip confirmed the material migration in a bidirectional way from the electrodes.
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