There has been a lot of discussion over the years about what makes a good EDM graphite. EDMers have learned that is not an easy question to answer. A lot depends on the job to be done. For one, it may be speed, for another, surface finish and for a third, wear resistance. Is it a simple electrode or does it have fine detail or fragile features? Only the EDMer can know that for sure, but when all is said and done EDMers agree, there are five essential performance factors that emerge as universally important. Only the weight of importance given to each will vary from job to job.
The ease with which an electrode can be fabricated will go a long way toward making an EDMer happy, or very unhappy. Not all electrodes have fine detail, but all electrodes can be ruined by a chip or a hidden flaw in the material. The most important physical properties of the graphite effecting machinability are the strength of the material, its hardness, and its density. MICRON’s unique double bonded microstructure gives an additional strength component to the graphite, combining conventional particle-to-particle bonding with our unique bundle-to-bundle bonds. The result is a material capable of holding fine detail, complex geometries and thin ribs with ease. All this is done without the increased hardness typical of many conventional graphites.
Often overlooked when considering the machinability of EDM graphites is the density of the material. Some graphite manufacturers have even abandoned publishing a density specification in their physical property data! It is easy to see why the density of the material is an important factor when considering an EDM graphite. More particles in a given mass means more material to hold a detailed feature in the electrode, and more material to machine away. The density of the material should always be considered when setting speeds and feeds for electrode fabricating equipment.
THE key physical property affecting the speed of a graphite is the average particle size of the material. The larger the particle size, the greater the rate at which metal will be removed from the workpiece. The MICRON “E” grades run the range of modern EDM materials. The Ultra-Premium E-970 at <4 microns particle size, and Premium E-950C and E-940 at <7 microns, combine better than expected metal removal with all the other performance features expected from EDM graphites in these classifications. At the top of the Superfine classification is the E-900, at <8 microns, combining excellent metal removal with all around solid performance for machinability, wear resistance and surface finish. For maximum metal removal, our speed burner E-888, with a particle size of 14 microns, rounds out the Superfine classification.
Electrode wear is the enemy of the EDMer. Wear resistance from your EDM graphite means fewer electrodes, less time and cost in fabrication, and more time in the EDM doing its job! Three physical properties of the graphite impact the wear resistance of the material. These are the micro-structure, the particle size and the density of the graphite. Particle size and density stand to reason. The smaller the electrode particle dislodged, the smaller the impact on the size of the electrode. Similarly, the more particles of graphite in a given area (density) the less the impact when one of those particles is dislodged.
But there’s more to the story! Now the unique double bonded microstructure of the MICRON EDM electrode materials again comes into play. Since the EDM process is a non-contact machining method, we know that electrode wear comes from the EDM process itself, not from the abrasion of tool on workmetal. Wear in the electrode comes from the bonds in the graphite microstructure breaking down. MICRON EDM graphites combine conventional particle-to-particle bonding with their unique bundle-to-bundle bonds, meaning there are two bonds which must be broken before electrode wear occurs. When the single particle-to-particle bonds of conventional graphites break down, that’s it, they’re done! Two bonds really are better than one!
The surface finish which can be achieved by a given EDM graphite is directly related to three important physical properties, the effective particle size, the microstructure and the density. As any EDMer would expect, the smaller the particle size of the graphite, the smoother the expected surface finish on the workmetal. However, with the MICRON EDM electrode materials, that’s not the whole story.
The unique microstructure of the MICRON materials helps provide superior surface finish. The high-density, discreet bundles into which the particles have been engineered helps give the EDMer a finer surface finish than would be expected from the particle size alone. This “effective particle size” from the MICRON materials is usually typical of materials having particles one to two microns smaller than the actual MICRON particles. Since we know particle size effects metal removal rate as well, EDMers can have a faster material with superior surface finish using the MICRON EDM electrode materials.
Many graphite companies will tell you that the cost of the electrode material is insignificant when compared to the overall cost of the job. Who are they trying to fool! In today’s competitive environment every penny counts. If you can get the same or better quality from a product that costs less, you’re throwing money away by not giving it a try. MICRON EDM graphites offer superior performance on all the factors important to EDMers, and at a very competitive price. Better performance, better price? Try it for yourself and you be the judge. Click Contact Us to set up an evaluation in your shop and prove it to yourself where it counts, in YOUR machine.