Electrical discharge machining (EDM)

Electrical discharge machining (colloquially) Is referred to as spark machining, spark eroding, burning, die sinking, wire burning or wire erosion, is a manufacturing process whereby a desired shape is obtained using electrical discharges (sparks). An electrical spark is created between an electrode and a workpiece. The spark is visible evidence of the flow of electricity. This electric spark produces intense heat with temperatures reaching 8000 to 12000 ^oC, melting almost anything (fig 1). The spark is very carefully controlled and localized so that it only affects the surface of the material.

The EDM process usually does not affect the heat treat below the surface. With wire EDM the spark always takes place in the dielectric of deionized water. The conductivity of the water is carefully controlled making an excellent environment for the EDM process. The water acts as a coolant and flushes away the eroded metal particles.

EDM spark erosion is the same as having an electrical short that burns a small hole in a piece of metal it contacts. With the EDM process both the workpiece material and the electrode material must be conductors of electricity.

Advantages of Electrical Discharge Machining are such as:

• Creates complex shapes that would otherwise be difficult to produce with conventional cutting tools.
• Cuts extremely hard, challenging and exotic materials to very close tolerances for high precision mechanical components.
• Suits very small work pieces, where conventional cutting tools may damage the part from excess cutting tool pressure.
• There is no direct contact between tool and work piece. Therefore, delicate sections and weak materials can be machined
• without any distortion.
• Little or no polishing is required after the process is complete.

Disadvantages of Electrical Discharge Machining are such as:

• The slow rate of material removal.
• -The additional time and cost used for creating electrodes for Ram/Sink EDM.
• Reproducing sharp corners on the work piece is difficult due to electrode wear.