The wire used in the EDM (electrical discharge machining) process can be made of one of several different types of materials.
Options include brass, brass-coated copper, zinc-coated brass, brass with a steel core, tungsten, and molybdenum, to name a few. It’s worth noting that each of these materials has its own benefits, cost, and purpose.
EDM Wire Sizes
Electrical discharge machining wires range in diameter – from .0008 to .013 inches. Wires with a .0008-inch diameter generally produce a .00044-inch radius in corners, a feature that’s almost impossible to achieve using any other option.
Such precision might be needed for openings in dies used to make electrical components. However, it’s worth noting that wires with such a level of fineness are rarely used due to the unusual challenges they create.
Typically, the finer a wire is, the more difficult it is to thread, the slower the cut, and the lower the power settings. As a result, many shops prefer not to use such wires due to the lengthy machining times and only opt for the option if the application requires it.
EDM Wire Types
The most commonly used wire, when it comes to electrical discharge machining, is plain brass wire. Brass, which is .010-inches in diameter, is used in more than 80% of all EDM applications and is available in three forms: soft, half-hard, and hard.
Soft brass is generally used to cut tapers, which require a low tensile strength. The good thing about soft brass is that it can bend at an angle while cutting without breaking.
Hard brass, on the other hand, is perfect for skimming and roughing in applications that require higher tensile strengths. Hard brass can withstand forceful flushing and allows operators to apply higher voltages through the wire without it breaking. The result? A much faster cutting speed.
Apart from plain EDM brass wire, there is also a zinc-coated option for faster machining speeds. Since zinc’s melting point is much lower, it absorbs heat as it simmers away. As a result, the underlying brass wire absorbs less heat so it stays stronger for longer.
While plain brass EDM wire is smooth on the outside, the zinc-coated option has a rougher finish to it that improves flushing and increases the cutting speed. While zinc-coated wires are said to deliver a 10 – 15% improvement in cutting speeds, reality does not often support that. Here at Rs Electro Alloys
, we find that the higher cost of zinc wire isn’t justified, though we keep some on hand for cutting certain materials.
Wires with a defused zinc outer layer and a copper core are generally referred to as stratified wires or high-speed wires. While copper’s high electrical conductivity makes it easier to double cutting speeds, it typically is more expensive than other available options.
Stratified wires are generally used to make roughing cuts. Plain copper is rarely used nowadays because it’s too expensive and too soft.
Something worth noting about EDM wires is that regardless of the option you choose, the wire can only be used one time for best results. Some machines may have rewinders that collect and reuse wire, but for most applications this is not good practice.