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moldmakingtechnology.com 29 can successfully resist erosion at its most vulnerable points, then overall wear will be minimized and maximum elec- trode life achieved. Electrode erosion cannot be prevented, but it can be minimized by choosing the proper electrode material/work metal combination and machining at the optimum settings. The ability of any electrode to produce and maintain detail is directly related to its resistance to wear and its machinabil- ity. Minimizing corner wear requires choosing an electrode material that combines high strength with high tem- perature resistance. Surface finish. Fine surface finish is obtained with a combination of the proper electrode material, good flush- ing conditions and the appropriate power supply settings. High frequency, low power and orbiting produce the best finish, as these conditions produce smaller, less defined craters in the work metal. The final surface finish will be a mirror image of the electrode's surface. This means, for example, that graph- ite grades with a particle size of less than 1 micron and very high tensile strength, isotropy and uniform struc- ture, or those with a particle size from 1- to 5-micron isotropy, uniform struc- ture and high strength would be opti- mal choices for finishing electrodes. Material cost. Generally, electrode material cost represents only a small part of the total EDM job cost, which is why it is often overlooked. Fabrication time, cutting time, labor and electrode wear are all factors that depend on the electrode material more than on any other factor. So, it is critical that you know the properties and performance characteristics of the available elec- trode materials so you can fully under- stand how they can affect the work metals being machined. This data is essential when doing a cost/performance analysis to determine the true cost of an EDM job. Regardless of the machine you are using, each of these per- formance factors will be impacted by the electrode material. Whether the job calls for a specific surface finish, electrode wear or MRR, a consistent effective electrode material is critical to achieving the desired result. FOR MORE INFORMATION Poco Graphite 877-762-6336 poco.com CONTRIBUTOR Robert Fothergill is an EDM applications specialist for Poco Graphite. .com " "