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Wire EDM is an ultra-precise method to cut virtually any electrically conductive material, regardless of alloy or hardness.

A thin wire is rapidly charged to a voltage. When the voltage reaches a certain level, a spark jumps the gap to the part, and melts a tiny bit of material. This "spark erosion" happens continuously, and appears to the eye as being a steady "burning away" of material.

The entire process typically happens while submerged in very pure, deionized, temperature-controlled water. This water is what continually flushes away microscopic particles of removed material.

There is no physical contact between the wire and the part being machined, so there are no cutting forces as in other methods of machining.

The wire is "continuous", and constantly fed from a large spool. It passes through the work area (the part) and is discarded out the back of the machine. The wire is not consumed or "burned up" as it passes through the area where the "spark erosion" occurs, however wire is never re-used. Wire diameters range from .0008"-.013" although .004" to .012" is the range most typically used. Wire can be anything from plain brass (in varying hardnesses) to coated brass or copper (plated with zinc, zinc oxide, or some other formulation that promotes better cutting in certain materials), to moly, or even pure tungsten.

The position/movement of the wire through the workpiece is controlled by a computer and servo motors, not unlike any other CNC machine (although generally more accurately than a CNC mill or lathe).

The hardness of the workpiece material has no adverse effect on the cutting speed, and cutting parts after heat treating is quite common and often desireable.

A modern Wire EDM machine has 4 independent axes of movement. The position of the wire guides can be independently and precisely controlled both above and below the part which allows "tipping" of the wire in any direction (often to 30° or even more). The 2 axes "below" the part are known as X/Y, and the 2 axes "above" the part are known as U/V (see drawing at the bottom of this page). The U and V axis are actually "differential" axis in that moving X/Y moves the entire wire while keeping it vertical, while moving U and/or V moves the top of the wire relative to X/Y.
This allows the cutting of tapered parts, as well as other very complex shapes. The only limitation is that the wire must be able to pass through or by the workpiece (since the wire is continuous).

When cutting an inside/contained shape, a "start hole" is required to feed the wire through. This hole can either be drilled (if the material is not too thick, and not heat treated) or it can be burned through using a special type of edm machine made specifically for this purpose.

The Wire EDM cutting process can be accurate and repeatable to ±.0001" or even better under certain conditions. When extreme accuracy and/or super-fine surface finishes are required, it is common to take "multiple cuts" across the same surface -- these are known as "rough" and "trim" passes. The amount of material removed on "trim" passes is rarely more than .001" or .002", and can be as little as .0001". Typically a rough pass would be done using a high power setting, and then subsequent trim passes (as few as 1 and as many as 4 or 5) use less and less power to obtain the very high accuracy and fine finish that might be required.

Since there are no cutting forces and no burrs, extremely delicate and/or small parts can be cut. Quite literally, it is possible to cut parts that can only be seen under a microscope.

On the other end of the scale, parts as thick as 10" or more can be cut as well. Some custom machines can even cut parts over 20" thick!

You can jump to the Video Page to see this process in action, or to the Examples page to see sample parts.

For more specific questions and answers about wire edm, see the Wire EDM FAQ page.