Major perils linked with EDM

Electric discharge machining (EDM) is capable of machining complex shapes in hard materials. The process includes an electrode and a workpiece, both submerged in dielectric fluid. Current flows between the workpiece and electrode, repeatedly creating tiny plasma zones with temperatures around 10,000 degrees C. The high temperatures produce localized, instantaneous melting of the material. Though the process may seem violent, it occurs on such a tiny scale that the resulting metal removal can be precisely controlled. EDM is considered to have a low incidence of operator injuries combined with a minimal impact on the environment. Safety should be the foremost concern in every job. The fact that EDM is not a dangerous process should not lull us into complacency about EDM safety. EDM hazards Most EDM manufacturers recommend driving a copper clad ground rod through the cement into the earth adjacent to the machine, and bonding the machine to the rod with a heavy gage copper wire. If this is not possible, a heavy gage copper wire should be routed to the nearest reliable earth ground in the plant. Do not rely on metal conduit or the jacket of BX cable to give a reliable ground. Also, if utilizing a water pipe as a ground, be sure to bond the ground wire to the pipe where it enters the building, before the water meter or any water filter, as plastic components in those elements may break the electrical path to ground. Explosions were once a common hazard when sinker EDMs utilized kerosene as a dielectric. Kerosene vapors can be quite explosive. The hazard of concern with both wire and sinker EDMs is that of trapped explosive gases that are a by-product of the EDM process being ignited in blind cavities or fixtures. EDMing with either water or hydrocarbon dielectric will produce hydrogen gas. Normally, this gas is vented harmlessly to the atmosphere. However, in certain applications there can be areas in the workpiece or the mounting fixture where the gas can accumulate. If there is also trapped air in the same area that has not been displaced by the dielectric, an EDM discharge can ignite the mixture with violent results. Fire is normally associated with sinker EDM. Even though modern dielectric fluids have a flash point in excess of 240, once that flash point is reached, a filled dielectric work tank will fuel a raging fire. Numerous shops have burned due to sinker EDM fires, especially sinker EDMs that were left burning overnight unattended. In a wire EDM, the primary chemical hazard is from the cleaning solutions some operators use to clean the machine and remove scale from the tooling or the work tank. Many of these solutions contain phosphoric or muriatic acid. Even though many of these chemicals may be available in local hardware stores, their use in an industrial environment is very dangerous and possibly illegal. In a sinker EDM, the primary hazard is that the dielectric fluid may cause skin problems. This is primarily because petroleum based products act as a solvent and remove the fat from the operator's skin. This will often result in dry and cracked skin, which will be the entry point for dermatitis. The other dilemma is that the thinner oils that flush so well also get into the pores of the skin. The water in the dielectric tank in a wire EDM is susceptible to the growth of bacteria. Slime on the walls of the dielectric tank or the sight glasses are an indication of this problem. Operator contact with bacteria laden water is not a good thing. This problem, while not common, is readily addressed by the addition of an ozone generator to the machine. This option should also be seriously considered if the machine is cutting medical parts. Bacteria can also grow in dielectric oil. It is a well-known fact that bacteria thrives on moisture laden diesel fuel. If the oil in your tank smells, change it! The possibility of lead poisoning in coated wire wasMen's Sneaker Hub Online