Electrical discharge machining

Electrical discharge machining removes material from an electrically conductive workpiece through repeated, controlled electrical sparks across a small gap. It can form hard materials without direct cutting-tool contact.

Spark erosion: Material removal by repeated electrical discharges that locally heat and eject material. EDM is a controlled machining application of this broader erosion process.
Die-sinking EDM: An EDM method that uses a shaped electrode to form a cavity in a workpiece. It makes dies, molds, and other cavities by copying the electrode's shape.
Electrical conductivity: A material property describing how readily electric charge flows through a substance. EDM generally requires a conductive workpiece to sustain discharges.
CNC milling: A computer-controlled process that removes material with rotating cutting tools. Milling cuts by tool contact, while EDM erodes material with electrical discharges.
Recast layer: A resolidified layer of material formed when molten material remains on a surface after thermal processing. Each discharge can melt material that resolidifies on the machined surface.
Dielectric fluid: An electrically insulating liquid or gas that separates electrodes and influences electrical discharge behavior. It insulates the gap between discharges and helps flush away eroded particles.
Wire electrical discharge machining: An EDM method that cuts a workpiece with a continuously fed thin wire electrode. Wire EDM is suited to precise through-cuts and intricate profiles.
Electrical resistivity: A material property measuring how strongly a substance resists electric current. Workpiece and electrode resistivity affect current paths and local heating.
Electrochemical machining: A machining process that removes conductive material through controlled electrochemical dissolution. It removes metal by anodic dissolution rather than spark-driven melting and ejection.
Heat-affected zone: Material near a heated process zone whose properties or microstructure changed without melting. EDM's localized heating can alter material beneath the recast surface.

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