Optimization of the EDM Drilling Process to Increase the Productivity and Geometrical Accuracy

This paper deals with the production of a geometrically specified borehole diameter using EDM drilling. To produce a specified borehole different electrode diameters can be used. For each electrode diameter the discharge energy has to be adjusted. This influences the amount of removed material of a single discharge and therefore the productivity of the EDM drilling process and the geometrical accuracy of the borehole are affected. For the industrial use of EDM drilling there are no recommendations concerning the electrode diameter and machining settings for the discharge energy to be used to achieve a specific diameter. To study the influence of the electrode diameter and discharge energy on the productivity and geometrical accuracy a specified borehole diameter of 2.0 mm was produced using four different electrode diameters. The electrode diameter ranged from 1.6 mm to 1.9 mm. By varying the discharge current and discharge time different machining settings were developed to achieve the desired borehole diameter. The influence of the parameter settings on the feed rate, the electrode wear ratio and the geometrical accuracy of the borehole were studied. Furthermore, the influence of the servo of the feed axis on the formation of a bulging at the borehole entry was investigated. The experiments show an opposing trend in maximizing the productivity and the accuracy of the produced borehole respectively. The results presented in this paper help to access the potential of EDM drilling to produce a specified borehole diameter and to provide basic technological information for industrial users.