You can think of wire EDM as the non-contact, 21st Century version of the fretsaw. A fretsaw is used to cut complex shapes from blocks of wood. The key to its versatility is the blade, which is essentially just an abrasive wire. Being thin and able to cut on all sides, the woodworker can turn it easily to follow a path through the wood. By threading the blade through a hole drilled in the wood it’s even possible to cut out internal sections.
The same principle is used to make the complex hole patterns needed in extrusion dies, but owing to the hardness of the materials, wire EDM is preferred process. In fact, there’s a perception that wire EDM services are of interest only to toolmakers, but that’s a mistake. Wire EDM has advantages in a range of applications including low volume production.
Wire EDM 101
To understand where to use this process helps to know a bit about it. Like EDM sinking and hole cutting, wire EDM uses electrical arcing to erode material. The electrically conductive workpiece is placed under flowing water and brought close to the electrode. At the closest point, high voltage leaps across the gap, blasting a microscopic piece of material from the surface, which is carried away by the water.
That arcing happens at very high frequency, progressively widening the gap between tool and workpiece. If the gap gets too big an arc can’t form, so the electrode is moved closer as the workpiece erodes. Modern machines use advanced gap-monitoring algorithms to maximize cutting speed while preventing wire-to-workpiece contact.
In sinking EDM the arcing happens over a wide area, so the electrode advances slowly. In contrast wire edm uses a wire typically just 0.010” diameter. This doesn’t have to remove much material to cut a path, so the wire can move through the workpiece at several inches per minute.
In a typical CNC machine, the wire is vertical and the workpiece moves against it in X and Y directions. Because the wire also erodes it gets fed through the gap, so is technically a consumable. Inclining the wire makes it possible to cut tapers in the workpiece.
Machining with wire EDM
EDM is often the most cost-effective way of machining very hard materials like tool steel, carbides and exotic alloys like inconel and hastaloy. It has the advantage of not putting any cutting forces into the workpiece, so there’s no distortion, making it possible to produce very thin sections. In addition, wire EDM can produce internal corners with radii not much bigger than that of the wire itself.
In conventional metal cutting, two passes are usual to achieve the desired final size and finish. The same holds true for wire EDM. Turning up the electrical power erodes the metal faster but the finish suffers. Reducing the power for a second pass creates a finishing cut that leaves a good surface finish.
Unlike machining processes that make chips, wire EDM has the potential for increased material utilization. (Something of great interest when cutting high-value materials!) As the wire removes very little material there’s often a large internal slug left behind. Milling or grinding would turn this into a pile of chips, but with wire EDM it can be saved and used on another job.
Tooling applications for wire EDM
Probably the best-known application is cutting the profile in extrusion dies. For aluminum extrusion, these are usually made from H13 tool steel. A hole is first drilled through the die blank, (often also by EDM,) and the wire is then threaded through. The CNC moves the blank through the wire to cut the required profile. On modern wire EDM machines, the wire can be inclined to cut of shapes with tapered sides.
Wire EDM is also useful for making punch tools. A blank of tool steel is moved around the wire to cut the profile needed. Again, the ability to cut tapers is extremely useful.
Applications other than tooling
Any 2D profile can be cut from a conductive material by wire EDM. Broaching and milling may be possible in some cases, but wire EDM offers several advantages:
- Creates sharp internal corners.
- No cutting forces, allowing machining of very small parts.
- Ability to cut very hard material at relatively high speed.
- Suitable for unattended machining.
- Removes constraints on the design imposed by conventional metal removal.
- No special purpose tooling needed.
- Higher material utilization.
One class of applications for wire EDM is making precision machine parts, particularly where they are needed in small volumes. Sewing machine components would be a good example, gears, and splines another.
Other categories are medical devices, surgical instruments, and small hand tools. For each of these, the ability to cut complex paths in very hard material, like stainless steel, makes wire EDM highly cost-effective.
Qualifying wire EDM services
EDM is a highly specialized technology. Most manufacturers prefer using external EDM services rather than trying to develop the expertise themselves.
When looking for EDM services, and especially wire EDM services, it’s essential to evaluate potential partners carefully. Verify their CNC equipment is well-maintained for the highest precision, and look for advanced control technology that minimizes cutting time. And as with any contract service, look at how they organize their shop. One that looks disciplined will almost certainly do a better job with your order.
Think about using EDM
Tooling companies use wire EDM services to make extrusion dies, but it’s applications extend much wider. Consider using this process for low-volume production of complex parts such as gears, splines, medical equipment/tools. The speed, quality, cost etc… may pleasantly surprise you!
About Micropulse West
Since 1994, Micropulse West has been proudly offering Precision Manufacturing Services such as EDM, CNC and Manual Machining to companies within highly regulated industries like Aerospace/Defense, Energy, Medical, High Tech as well as the Automotive and Firearms Industry. Our skilled and experienced machinists use the latest and most accurate Precision Machining technologies in order to deliver the highest quality precision machined parts. From small prototyping projects to high volume machining projects, Micropulse West is the Precision Machine Shop you can trust.
If you would like to learn more about what makes Micropulse West different and how we can help with your precision machining needs, call 1- 480-966-2300.