GRAPHITE EDM ELECTRODE PERFORMANCE AS AFFECTED BY POWER SUPPLY VARIABL

Graphite has become the most popular EDM electrode material for rough and intermediate machining and is used extensively in finish machining. The lower cost, lower density graphites are used primarily for roughing while the higher cost, higher density, ultra-fine grain materials are used for finish machining. The wide range of available graphites and the large number of controllable variables associated with the modern solid state power supplies have led to some confusion resulting in the inefficient use of graphite. The results of an extensive testing program conducted to measure the interdependence of power supply parameters and electrode performance should remove some of this confusion. A solid state power supply having a 500 amp capability and a frequency range of 0.2 to 135 kilohertz was used during the testing program. Some of the parameters investigated include gap voltage, current, duty cycle, frequency, on-time, geometry, and dielectric oil contamination.