What Is EDM Machining?

EDM stands for Electrical Discharge Machining. Unlike conventional machining, which uses cutting tools to remove material by force, EDM uses controlled electrical sparks to erode material with extreme precision.

The process works by passing an electrical current between an electrode and a conductive workpiece through a dielectric fluid. Each spark removes a tiny amount of material — thousands of times per second — until the desired geometry is achieved.

Why Use EDM Instead of Conventional Machining?

EDM has several properties that make it uniquely suited for demanding applications:

• No cutting force. Because there's no physical contact between the electrode and the workpiece, there's no deflection, no residual stress, and no distortion — even in thin-walled or fragile geometries.
• No heat-affected zone. The thermal energy is highly localised and controlled, meaning material properties are preserved close to the machined surface.
• Works on any conductive material. EDM can machine hardened steel, titanium, Inconel, tungsten carbide, and other materials that would destroy a conventional cutting tool.
• Extreme precision. Modern EDM systems routinely hold tolerances of ±0.001" or better — in materials at full hardness.

The Two Main Types of EDM

Sinker EDM (Ram EDM / Die Sinking)

A shaped electrode — typically graphite or copper — is fed into the workpiece to produce a 3D cavity or feature. Used for die cavities, mold tooling, blind pockets, and complex internal geometry that a milling cutter can't reach.

Wire EDM

A thin brass or coated wire is used to cut through-profiles in conductive material. Think of it like a bandsaw, but using electrical discharge instead of a blade — capable of cutting any 2D profile in any conductive material at full hardness, with exceptional surface finish.

When Is EDM the Right Choice?

EDM is the process of choice when:

• The material is too hard for conventional cutting tools
• The geometry includes sharp internal corners, blind pockets, or undercuts
• Surface finish requirements are tight
• No residual stress or distortion can be tolerated
• The feature is inaccessible to a rotating cutter

Industries That Rely on EDM

EDM is used across aerospace, nuclear, medical device, automotive, moldmaking, and forging industries — anywhere that precision, material hardness, or geometry complexity makes conventional machining impractical.

EDM Zap has been engineering EDM solutions for manufacturers across these industries since 1971. If you have a part that's pushing the limits of what conventional machining can deliver, talk to one of our engineers.