Single crater dimensions and wire diameter influence on Wire-EDM

Abstract

In Wire Electrical Discharge Machining (WEDM) the erosion process is based on the superposition of craters. The plasma channel and the craters’ shape have an impact on the process and on the characteristics of the machined surface. This impact goes from the cutting speed to the surface roughness passing through workpiece temperature gradient during the spark. Several models simulate the crater formation through thermal analysis, yielding symmetrical shapes. Commonly non-homogeneous and random aspects in the dielectric and the electrode geometry are neglected. Such features introduce an asymmetric aspect to the crater shape. To investigate the influence of the tool electrode geometry on the craters’ shape, single craters on steel are produced at different pulse energy levels and with three different wire diameters 0.20mm, 0.25mm and 0.30mm. An optical microscope is used to map the single craters’ topography and subsequently extract their dimensions. The single craters’ lengths and aspect ratio are analyzed. In the lower energy range the random aspects dominate the crater shape, the craters are smaller and rounder. Higher energy pulses create consistently bigger and elongated craters. The aspect ratio depends on the wire geometry, thinner wires produce more elongated craters. This behavior reinforces the idea that from a certain energy level on the tool geometry effects overcome the random aspect of the process, generating elongated craters.