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In wire electrical discharge machining (WEDM), the erosion is made through a series of overlapped craters. The shape of these craters has a relevant impact on the characteristics of the machined surface, from surface roughness to heat effects during the spark. Current models on EDM process do not represent specific WEDM characteristics, such as radial asymmetry of the crater or geometrical effects on the crater shape. In order to characterize the crater’s dimensions in WEDM, single discharge experiments are performed on polished steel for pulses with different energy levels. A 3D optical microscope is used to map the single craters’ topographies (experimental work). To capture the craters’ dimensions, an ellipsoidal equation is applied with a Levenberg–Marquardt algorithm. The ellipsoidal equation is capable of identifying the dimensions along the wire length, perpendicular to the wire and the depth of the crater. The ratio between the dimension along the wire and the dimension perpendicular to the wire is used to define a crater’s aspect ratio and characterizes its elongation. The aspect ratio of the single craters is found to be dependent on the pulse energy. Low-energy pulses create rounder craters, while high-energy pulses form elongated craters that are longer along the wire length. Such behavior suggests that the crater formation is constricted by the wire geometry, having a preferential direction of growth, along the wire length.

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Wire electrical discharge machining (WEDM) is a non-conventional machining method capable of cutting complex shapes on hard electrically conductive materials. The die manufacturing and aerospace sectors, main applications of WEDM, require high workpiece precision. In WEDM the kerf (cutting width) might not be constant along the wire which may cause deviations on the workpiece. The kerf value is affected by tool erosion and inhomogeneous cutting conditions like flushing, concentration of debris, wire vibration, cutting parameters, etc. When comparing the top and bottom of the workpiece, a deviation labeled conicity may appear and can compromise accuracy. Nevertheless, the causes of this difference are yet unidentified. Given the importance of workpiece precision in this specific process, it is essential to explore which variables influence this geometrical deviation. Therefore, this study aims to investigate the influence of individual process variables on the conicity produced by WEDM trim cuts. Using brass CuZn37 (DIN CW508L) wire as the tool and AISI D2 steel as workpiece material, a design of experiments (DOE) is elaborated varying: flushing conditions, unwinding speed, pulse energy, piece height and pulse-off time while tracking the cutting duration, total number of discharges and short circuits. The conicity of the produced pieces is measured with a micrometer caliper. A variable to represent the physical aspect of the wire wear is created using the calculated pulse frequency, piece height, unwinding speed and pulse energy. The results are interpreted with an analysis of variance (ANOVA) and a graphical comparison. The flushing conditions, cutting duration, and pulse-off time were shown not to be statistically relevant. The most relevant parameters were the unwinding speed, pulse energy and wire wear variable. This result suggests that the conicity phenomenon is caused rather by the tool erosion than by cutting conditions.