Sinker EDM

Sinker EDM (also called die-sinking EDM) shapes a cavity in a conductive workpiece by plunging a precisely formed electrode toward it, eroding material with controlled electrical sparks until the cavity mirrors the electrode's shape.¹ It is the branch of EDM used for closed cavities and complex 3D shapes, such as mold and die cavities, rather than open through-profiles.

What actually drives sinker EDM cycle time

Cycle time depends heavily on cavity depth, required surface finish, and electrode wear, since a worn electrode gradually loses the precision of its shape and may need replacing partway through a deep or fine cavity.

Where it appears on the drawing

Implied by a closed cavity in a hardened conductive material with a complex 3D shape a rotating cutting tool cannot reach, such as a mold cavity or a sharp internal corner.

Common mistakes

Underestimating electrode cost and lead time; a sinker EDM job requires its own precisely made electrode before the cavity itself can even begin, which is a separate manufacturing step with its own cost and schedule.

How is sinker EDM different from wire EDM?

Sinker EDM shapes a closed cavity by plunging a formed electrode; wire EDM cuts a through profile with a continuously moving wire.

Why does sinker EDM need its own electrode?

Because the electrode's shape is what determines the cavity's shape; producing that electrode is itself a manufacturing step before EDM can start.

Does electrode wear affect accuracy?

Yes, a worn electrode loses precision over the course of a job, which is why deep or fine cavities may need a fresh or roughing/finishing electrode pair.