Wire & Sinker EDM.
Dielectric flushing metrics, spark gap voltage models, and recast layer analysis.
Non-Contact Material Removal
EDM removes material through thousands of controlled electrical sparks per second. Because there is zero physical contact between the tool (wire or electrode) and the workpiece, EDM can cut delicate structures without imparting mechanical stress, regardless of the material's hardness (provided it is electrically conductive).
The Recast Layer (White Layer)
The heat of the spark melts and vaporizes the workpiece material. The dielectric fluid rapidly cools it. Some of the melted material is not flushed away and re-solidifies onto the part surface. This is the "recast layer." It is exceptionally hard, brittle, and often riddled with micro-cracks.
In aerospace components (e.g., turbine blades), this recast layer must be completely removed via chemical etching or abrasive flow machining to prevent catastrophic fatigue failure.
Wire EDM Flushing
The speed of a wire EDM cut is not limited by the generator's power, but by the ability to flush the microscopic eroded particles out of the kerf. If particles remain, they cause secondary arcing, leading to wire breakage. Proper nozzle proximity (often < 0.005" from the part) and high-pressure deionized water flushing are the primary variables in maximizing cut speed.