In the machining business, it’s often possible to use traditional cutting tools, like grinders and end mills, to create parts and other items with particular shapes. But what about when the usual cutting tools aren’t up to the task?
In that case, there’s electrical discharge machining, known in the industry as EDM. EDM comes in two main forms that cover a variety of exacting machining applications across different industries.
In this guide, we’ll discuss what EDM is, what the two primary types of EDM machines are and what advantages they each have.
What is EDM?
EDM is a nontraditional method of machining that creates items using thermal energy to remove material — similar to laser cutting, for example. EDM uses tools of graphite or soft metal as electrodes and runs voltage through them to generate high-frequency spark discharges. During machining, both the electrode and the material being worked are typically submerged in a bath of dielectric fluid, which cools the electrode and workpiece, acts as a current conductor and flushes out debris.
The electrical discharges can easily cut through conductive materials like metals. EDM is valuable because it is useful for machining any conductive metal, no matter what the metal’s physical properties are.
Using EDM’s thermal energy for machining has several benefits. It is advantageous with notoriously hard materials, such as titanium, tungsten, hardened steel or carbides, where traditional tools are often inadequate. EDM is also useful for crafting items with elaborate, intricate shapes.
The Two Main Types of EDM Machines
What’s the Difference Between EDM and Wire EDM?
Below are the two main types of EDM machines:
1. Conventional EDM Machines
Conventional EDM also goes by several other names, such as sinker EDM, die sinking, cavity-type EDM, volume EDM and ram EDM. This type of EDM is popular because of its suitability for creating complex shapes.
Conventional EDM uses machining to create an electrode in a distinctive shape. It then sinks the electrode deep into the material that requires forming. The electrode creates a negative impression of its shape, thereby forming a mold.
2. Wire EDM Machines
Wire EDM, also known as spark EDM, wire burning and wire erosion, uses a thin heated wire as an electrode. Hard diamond guides hold the wire steady. The wire electrode moves through the metal to craft a particular shape — though the wire itself does not actually touch the metal, its electrical discharges do. During wire EDM machining, the wire constantly unspools from an automated feeder, so wire is always available for cutting a smooth, uninterrupted form.
Sometimes, a shape requires a cut through the middle rather than along the outside. In this case, machinists couple wire EDM with what is known as hole-drilling EDM. As the name of this technique suggests, hole-drilling EDM involves drilling a small hole through the middle of the workpiece. The wire can then thread through the hole to continue its accurate shaping. In this case, the electrodes are tube-shaped, and a dielectric fluid flows through them to the hole.
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In general, EDM makes sense as a machining technique when the material in question is conductive — basically any type of metal, even very hard ones. And EDM allows for complex shapes — such as sharp corners and thin slits — and depths that a conventional cutting tool could not achieve.
EDM is also ideal in many applications because it involves a minimal exertion of force. So it is suitable for even delicate shapes and fragile materials because it will not damage them with excessive mechanical energy during the machining process.
The choice of conventional EDM or wire EDM is sometimes more complicated. Below are some of the capabilities and applications of the two main types of EDM machines:
Capabilities and Applications of Conventional EDM Machines
Because of its use of shaped electrodes, conventional EDM is particularly useful for making dies and molds. It is also advantageous for small-batch production, particularly the production of prototypes. It has wide applications in industries like the automotive and aerospace industries because it can accurately produce complex engine parts. It is also commonly used in a range of industries for injection molding processes.
Capabilities and Applications of Wire EDM Machines
Wire EDM capabilities offer a few distinct benefits. They provide robust, reliable, cutting-edge performance while remaining user-friendly. Here are some of the advantages of wire EDM over conventional EDM:
Ease of production
With traditional EDM, the electrodes are susceptible to erosion and must receive regular replacement when they have become too worn to function. Traditional EDM also requires the machining of electrodes of particular shapes, and this additional pre-machining is time-consuming.
Wire EDM, on the other hand, is ready to go as soon as the wire is in place and does not require the time and material expenditures associated with preparatory machining. It is suitable for time-sensitive applications and shapes where the machining of matching electrodes would present a challenge. It is also commonly used in extrusion dies.
Components of EDM Machines
Below are some of the components used in the two main types of EDM machines:
Components and Construction of Conventional EDM Machines
Conventional EDM machines use a shaped electrode, a power source and a ram for propulsion. These machines often incorporate computer numeric controls (CNC) that assist with the automation process.
The electrodes used in conventional die-sinking EDM are usually made from copper or graphite. The choice between the two often depends on the ideal conductivity and erosion resistance of the electrodes. Graphite is more malleable, so it offers the advantage of making the electrodes of EDM machines easier to craft. On the other hand, copper is more durable and more conductive, so copper is useful for machining stronger metals.
Components and Construction of Wire EDM Machines
Wire EDM machines incorporate a spool of wire, diamond guides and an automated wire feeder.
The wire electrodes used in wire EDM machines are often made from copper or sometimes from brass, an alloy of copper and zinc. Brass is also useful for making the tube-shaped electrodes necessary for hole-drilling EDM machines.
Unlike the components of conventional EDM machines, however, the wire used in wire EDM machines does not necessarily need to have strong resistance properties. The reason is that the automatic feeder constantly unspools new wire for use in the machining, so as the old wire becomes dull, new wire is available to take its place.
Contact Astro Machine Works for All Your EDM Machining Needs
We provide full-service machining solutions in a variety of industries, from defense and government operations to pharmaceuticals manufacturing and food-processing industries. Our 35 years of experience in the custom machine building, machining and fabricating business means we can help you get the machining services and parts you need to need to ensure product quality, timeliness and performance.