Wire EDM is a way of cutting electrically conductive metal with electrical sparks instead of a cutting edge. A thin wire is fed through the workpiece, and the sparks between the wire and the part erode the metal along a programmed path. It is how many punches, tools and dies are made from hard metals. This guide explains how wire EDM works, names the parts of the machine, and sets it beside sinker EDM, the other main type of EDM.
Machine Tool Exchange buys used wire and sinker EDM machines directly from the shops that own them, so the guide ends with the specs that describe an EDM, the same details an owner needs when the time comes to sell one.
What Is Wire EDM?
Wire EDM, short for wire electrical discharge machining, is a machining process that removes material with rapidly recurring electrical discharges between a wire and the workpiece, which are separated by a dielectric liquid. It typically works on materials that are electrically conductive.
In wire EDM the tool is a thin single-strand metal wire, usually brass. The wire is fed through the workpiece while the part sits in a tank of dielectric fluid, typically deionized water. Because the material is removed by sparks rather than a cutting edge, wire EDM can cut hard metals that are difficult to machine by conventional means.
How Does Wire EDM Work?
A wire EDM machine cuts by running a wire along a programmed path through the part while sparks erode the metal. The wire and the workpiece do not touch. The spark jumps the small gap between them, and the CNC control steers the wire to trace the shape.
Step by step:
- Set up the part. The workpiece is clamped in the work tank and, on most machines, submerged in deionized water, which acts as the dielectric.
- Thread the wire. To cut an internal form, such as a die opening, a pilot hole is provided first and the wire is threaded through it. Modern wire EDM machines provide automatic threading.
- Cut. The wire is held between upper and lower guides. The guides, usually CNC-controlled, move in the X and Y plane to follow the profile. Because the wire erodes a little as it cuts, the machine constantly feeds fresh wire from a spool.
- Angle the cut. On most machines the upper guide can also move independently, which gives the machine the ability to cut tapered shapes and shapes that change from one profile at the bottom to another at the top.
The water is filtered to maintain performance, and brass is the standard, economical wire choice.
What Are the Main Parts of a Wire EDM Machine?
The main parts of a wire EDM machine are the work tank, the power supply, the wire drive and guides, the dielectric system and the control. Each matters when the machine is described or valued.
- Work tank: holds the dielectric fluid, usually deionized water, and the workpiece, which on most machines is submerged during cutting.
- Power supply (generator): produces the electrical discharges. Its generation matters as much as the frame.
- Wire drive and guides: the spool, the feed path, and the upper and lower guides that hold the wire and position it. Their condition is one of the first things checked on a used wire machine.
- Automatic wire threader: on modern machines, it threads the wire through the start hole automatically.
- Dielectric system: filtration and deionization for the water, including filters and resin.
- Control (CNC): runs the programmed path and coordinates the axes.
What Is Sinker EDM?
Sinker EDM, also called ram EDM or die-sink EDM, uses a shaped electrode instead of a wire. A graphite, copper tungsten or pure copper electrode is machined into the negative of the shape wanted. The electrode and the part are submerged in an insulating liquid, typically oil, and the electrode is sunk into the part, leaving its shape behind.
The typical sinker job is a complex three-dimensional shape, such as a mold cavity.
A third variety, hole-drilling EDM, produces small, deep, accurate holes. It is close to sinker EDM, but the electrode is a rotating tube that carries a pressurized jet of dielectric fluid.
What Is the Difference Between Wire EDM and Sinker EDM?
The main difference is the electrode. Wire EDM cuts with a thin moving wire and works best for through-cuts and profiles. Sinker EDM sinks a shaped electrode into the part and can produce blind features and cavities.
| Wire EDM | Sinker EDM | |
|---|---|---|
| Electrode | A thin wire, usually brass, fed from a spool | A shaped electrode of graphite, copper tungsten or copper |
| Dielectric | Typically deionized water | Typically oil |
| What it cuts | Through-cuts and profiles, including tapered shapes | Cavities and blind features, including complex 3D shapes |
| Blind features | No | Yes |
| Before cutting | A pilot hole for an internal cut | The electrode must be made first |
| Typical work | Punches, tools and dies from hard metals | Mold and die cavities |
Both typically work on electrically conductive materials, and both are used most widely by mold-making, tool and die shops. For where EDM fits among the other families of machine, see our guide to the CNC machine families.
What Can Wire EDM Cut?
Wire EDM typically cuts electrically conductive materials, including very hard ones. Materials that are difficult to machine conventionally, such as carbides, titanium alloys and heat-treated tool steels, can be machined precisely by EDM. Wire EDM is typically used to cut plates as thick as 300 mm (about 12 in) and to make punches, tools and dies from hard metals.
Beyond mold, tool and die work, EDM is also used for prototype and production parts, especially in aerospace, automotive and electronics.
What Are the Limits of Wire EDM?
Wire EDM trades speed and shape range for its ability to cut hard metal. The main limits:
- It is slower. Material removal is slow compared with conventional machining, and thicker sections are harder to flush, which limits cutting speed.
- Conductive materials, typically. EDM typically works with electrically conductive materials.
- Profiles, not pockets. Wire EDM cannot produce blind features. Blind cavities are sinker work.
- A recast layer. The arc melts a thin layer of the surface, and that layer can remain on the cut surface.
Where Does EDM Come From?
The erosive effect of electrical discharges was first noted in 1770 by the English physicist Joseph Priestley. In 1943 two Soviet scientists, B. R. Lazarenko and N. I. Lazarenko, were tasked with investigating ways of preventing the erosion of tungsten electrical contacts caused by sparking. At the same time, but independently, an American team developed an EDM machine for removing broken drills and taps from aluminum castings.
Which Specs Describe a Wire EDM Machine?
A wire EDM is described by its generator and control generation, its work tank size, its X, Y and Z travels and the maximum workpiece height, its wire threading (automatic or manual), and the options it carries, such as submerged cutting, taper cutting or automatic wire threading. The builder and model narrow it down further. Fanuc's ROBOCUT line and machines from Makino, Mitsubishi, Sodick and Agie Charmilles are among the wire EDM builders we buy.
A wire machine and a sinker machine are scoped on different things. For a wire machine, the questions are whether automatic wire threading still threads reliably and what shape the wire drive and guides are in. For a sinker, they are the C axis, whether an electrode changer comes with it, the electrode holding setup and the tank capacity. On both, the dielectric and filtration system deserves a look on an idle machine, and whether the machine still holds tolerance sits under all of it.
For how condition and specs feed into what a used machine is worth, see our CNC machine values guide.
If you own an EDM you no longer need, note the brand, model, year, condition and control type, and whether it has been sitting. Machine Tool Exchange buys used EDM machines outright, wire and sinker, in all sizes and control generations and any condition. For a wire machine specifically, see how to sell your used wire EDM machine. We buy outright and arrange the pickup. Request a quote or call 800-822-9524.
Frequently Asked Questions
What does EDM stand for?
EDM stands for electrical discharge machining. Material is removed by rapidly recurring electrical discharges between an electrode and the workpiece, which are separated by a dielectric liquid.
What is wire EDM used for?
Wire EDM is used to cut profiles and through-shapes in electrically conductive metal, especially hard metals. It is widely used to make punches, tools and dies, and EDM is also used for prototype and low-volume production parts in aerospace, automotive and electronics.
How does a wire EDM machine differ from a sinker EDM machine?
Wire EDM uses a thin moving wire, usually brass, and cuts through-shapes and profiles, typically in deionized water. Sinker EDM uses a shaped electrode of graphite or copper, typically works in oil, and can produce blind cavities and complex 3D shapes.
Can wire EDM cut any material?
No. EDM typically works with materials that are electrically conductive. Within those, very hard materials such as carbides, titanium alloys and heat-treated tool steels can be machined precisely by EDM.
Does Machine Tool Exchange buy used wire EDM machines?
Yes. Machine Tool Exchange buys wire EDM and sinker EDM machines, in all sizes and control generations and in any condition, including machines that are idle or decommissioned. It also buys hole-drilling EDMs. Send the details through the quote form or call 800-822-9524.
Have a wire EDM or sinker EDM you want to sell? Machine Tool Exchange is a direct buyer, so the offer comes from the buyer. We buy outright and arrange the pickup. Get a quote or call 800-822-9524.