Assessment of Electrode Wear Measurement in Micro EDM Milling

Abstract

In micro electrical discharge milling (micro EDM milling), the tool electrode kinematics is the same as in conventional milling, but the material removal is obtained by the heat and electrical forces in the gap between the tool electrode and the workpiece. The electrode wear in micro EDM milling is one of the main problems to be solved in order to improve machining accuracy. Most common, the electrode linear wear is measured on machine by touching the reference point with the electrode after machining a certain number of layers. The reduction of the electrode length due to the wear is used to modify the electrode trajectory. This paper presents an assessment of the electrode wear on micro EDM milling machine. The experiments were performed on state-of-the-art micro EDM equipment. The electrode wear was measured on the machine in a conventional manner as already described. Additionally, a Laser Scan Micrometer (LSM), implemented on machine as well, was used in two ways, namely to detect only the coordinates of the electrode tip before and after machining, and by acquiring the electrode profile. Experiments were performed by machining micro features in steel using several layer thicknesses and various process parameters. The results show that the accuracy of the electrode length measurement by touching the reference point is enough accurate for the estimation of the electrode linear wear. But to accurately measure the electrode volumetric wear, it needs to be calculated from electrode profiles acquired before and after machining.