EDM Machining Guide - Sinker EDM and Wire EDM

Complete guide to Electrical Discharge Machining: sinker EDM vs wire EDM, applications, surface finish, and process parameters.

What is EDM?

Electrical Discharge Machining (EDM) removes material via controlled electrical sparks between an electrode and the workpiece submerged in dielectric fluid. It machines any conductive material regardless of hardness.

Sinker EDM (Ram EDM)

A shaped electrode (graphite or copper) is plunged into the workpiece, creating the inverse shape. Used for mold cavities, complex 3D shapes, and internal features.

• Electrode Material: Graphite (fast, wears faster), Copper (slower, better finish)
• Surface Finish: Ra 0.4-3.2 microns
• Applications: Mold cavities, deep ribs, internal corners
• Pros: Complex 3D shapes, excellent corner detail
• Cons: Electrode wear, slow material removal

Wire EDM

A thin brass or coated wire acts as the electrode, cutting through the workpiece like a bandsaw.

• Wire Diameter: 0.1-0.3 mm
• Cutting Accuracy: +/-0.002 mm achievable
• Surface Finish: Ra 0.1-1.6 microns
• Applications: Precision punches, dies, extrusion dies, gears
• Pros: Extremely precise, no electrode needed
• Cons: Through-cuts only (requires starting hole)

Process Parameters

• Pulse Duration: Longer = more material removal, rougher finish
• Pulse Interval: For flushing debris. Longer = slower but more stable
• Current: Higher = faster cutting, more electrode wear
• Gap Voltage: Typically 30-100V

Advantages

• Machines hardened tool steel up to 70 HRC
• No mechanical cutting forces
• Burr-free process
• Sharp internal corners down to 0.05 mm radius