EDM

Process Definition & Working Principle

Electrical Discharge Machining (EDM) is a non-traditional thermoelectric manufacturing method that removes material via controlled thermal erosion. Material is detached from the workpiece surface through a series of rapidly recurring, spatially discrete electrical discharges (sparks) between two conductive electrodes: the tool (electrode-tool) and the workpiece (electrode-workpiece). These electrodes are separated by a microscopic distance known as the spark gap (typically $0.005-0.5$ mm) and are fully submerged in a dielectric medium (hydrocarbon oil or deionized water).

Spark Physics and Single Discharge Phases:

The physical material removal process of a single discharge pulse consists of four consecutive phases:

Kinematics, Axes, & Machine Configuration

The kinematic structure and mechanical configurations of EDM machines are categorized into two primary forms: Sinker (Die-Sinking / Ram) EDM and Wire EDM (WEDM).

Sinker (Ram) EDM Kinematics:

Sinker kinematics are built around the highly precise linear movement of a vertical axis (Z-axis Ram) carrying the pre-shaped tool electrode.

Tooling & Cutting Geometry

Since EDM is a non-contact manufacturing process, the tool electrode is not subjected to mechanical cutting forces and does not require conventional rake or relief angles ($\gamma ,\alpha$). Instead, tool engineering focuses on electrical conductivity, thermal stability, spark gap compensation (overcut), and wear resistance.