What Is Electrical Discharge Machining (EDM). Machining with EDM

What Is Electrical Discharge Machining (EDM)?

Especially preferred in mold making, Electrical Discharge Machining is a shaping method that removes material electro-thermally by causing localized melting and vaporization on the workpiece through sparks applied to its surface.

It’s also known as EDM (Electric Discharge Machining). It’s a non-traditional form of precision machining that uses thermal energy instead of mechanical force to remove material from a workpiece. Because it uses electrical sparks between 8000°C and 12000°C, it’s sometimes referred to as Spark Machining. Engineers often turn to EDM when machining processes like CNC milling and CNC turning can’t produce the desired cut, such as sharp internal corners.

electrical discharge machining (EDM) machine — Electrical discharge machining (EDM) machine

Thanks to the EDM process, any electrically conductive material can be machined regardless of its hardness or machinability. Because of this, the method is especially suitable for hardened steels, hard metals, and fit/mating parts that are difficult to manufacture.

How EDM Works

In EDM, electricity is applied to the workpiece and to the material used as the electrode. The electrode acts as the cathode (- pole), while the workpiece is the anode (+ pole).

The electrode is brought close to the workpiece, but never touches it. An electric arc forms between the electrode and the workpiece. Because of this current, the area opposite the electrode heats up and melts or vaporizes.

This way, the workpiece is given the desired shape through melting and vaporization.

For the electric arc discharge process to be carried out properly, it isn’t enough for the gap between the electrode and the workpiece to simply be the desired amount. The material removal process, and the area from which material is removed, need to be controlled in a stable environment. For this, dielectric fluid is used, and the area where material is removed is isolated. For detailed information, see: What is dielectric fluid, what does it do?

Sinker (Die-Sink) EDM

EDM machining is done in two ways. One is called “sinker (die-sink) EDM,” a method in which an electrode shaped to a specific form is pressed into the workpiece, creating a cavity in the shape of the electrode in the workpiece.

Wire EDM

The other EDM machining method is wire EDM. A wire electrode cuts the part with positioning directed by the machine (technically it’s not accurate to call this a mechanical cut — “melting” would be more correct). With this method, it’s possible to make smooth, complex-shaped cuts, similar to laser cutting.

cutting on an EDM machine — Cutting on an EDM machine (wire EDM)

Video of the wire EDM operating system and wire EDM cutting

Spark Erosion Principle

EDM is a non-contact machining method that removes conductive material by melting it with electrical sparks.

Machining Hardened Steel

EDM can machine extremely hard or brittle materials that conventional cutting tools cannot machine.

Role of Dielectric Fluid

The dielectric fluid used during the process both cools the work zone and flushes away the melted metal particles.

Applications of EDM

Micro-hole drilling
Cutting sharp internal corners
Creating injection molding tools
Cutting extrusion dies
Cutting rotational forms
Drilling curved holes
Engraving on hard materials
Removing broken tools from workpieces

Questions About EDM

QUESTION: What is the precision of EDM?
ANSWER: EDM can work within very tight tolerances, such as +/- 0.012 mm. This is why the aerospace and medical industries benefit from this process.

QUESTION: Is EDM environmentally friendly?
ANSWER: Because of the amount of electricity required for Electrical Discharge Machining to take place, it doesn’t represent an environmentally friendly machining method. As more and more companies globally try to take measures to reduce their carbon footprint, other machining methods that require less electricity, and are therefore less harmful to the environment, are preferred over EDM.

QUESTION: Which materials can be machined with EDM?
ANSWER: The material must be electrically conductive. Any metal known to be conductive can be machined, even hard materials such as Inconel and tungsten carbide. Although the process is technically stress-free, it should also be kept in mind that machining is still a thermal process that can change the metallurgy of the workpiece.