EDMMax – The affordable fast wire solution for most wire EDM applications. This full 4 axis machine uses.007” diameter molybdenum high tensile wire. The most popular EDM wires are brass. They are a copper and zinc alloy and cut more quickly as the concentration of zinc increases. However, there are many other factors to consider when choosing an EDM wire.
1. High Tensile Strength
The ability of a wire to withstand the stretching forces of an EDM cut is called its tensile strength. Copper has one of the lowest tensile strengths, while molybdenum is significantly higher. This is why molybdenum is used in small and fine diameters for cutting tall parts and other jobs that require excellent straightness and crisp geometry. It also has high resistance to wire breakage and a long lifespan. Molybdenum wire has a lower disconnection rate and can be used for longer periods of time.
All materials conduct electricity, but the lower the melting point and vaporization temperature, the better. This allows the spark to burn more quickly and cleanly, reducing the chance of contaminants sticking in the gap. It also means that the spark craters left on the wire are much smaller, which makes it easier to flush them away.
2. High Conductivity
A wire’s conductivity reflects its ability to carry current. Higher ratings mean that a wire can deliver more power, which improves cutting speed and allows it to cut harder materials with less force. Molybdenum’s high conductivity also helps it disperse the heat generated during EDM machining. This minimizes thermal expansion, which can damage the wire and lead to premature failure.
Copper is commonly used as an electrode in EDM, but it has a high melting point and vaporization temperature that slows its cutting speed and causes it to burn more than other metals. Brass, on the other hand, has a lower melting/vaporization point and cuts much faster. It can even cut hardened steels with a relatively high speed. Brass wires are often coated with pure zinc to increase their conductivity and cut faster.
3. Good Flushing
Wire EDM machines use quickly repeating regulated electrical charges to erode material from the surface of metal wire. The technique can cut any conductive metal, regardless of hardness, but it is especially useful for complex shapes and fine details that would be difficult to cut using other methods. Tungsten is one of the last options considered when trying to solve a difficult EDM application, but it is also frequently the best choice. Tungsten has the highest tensile strength of any EDM electrode, which allows it to sharply define and carve small, straight-walled details.
The gap voltage (UAB-Ugap) between the workpiece and the wire electrode determines how quickly a discharge channel forms, which affects the cutting efficiency and surface quality of a part. Discharge waveforms of 0.18 mm molybdenum wire and 0.05 mm ultra-fine molybdenum wire during continuous cutting reveal that the former has a higher multi-channel discharge than the latter.
4. Low Disconnection Rate
Molybdenum wire has a very low disconnection rate which makes it ideal for electric discharge machining. It can cut narrow kerfs or near-sharp inside corner radii that would be impossible to achieve with brass EDM wire. The spark craters left on the surface of the electrode wire are also smaller than those of copper or brass-based wires, making them much easier to flush.
Tungsten wire is another choice for difficult applications, but it has the highest temperature of all wires and requires the machine to be running at higher speeds. In addition, one load of tungsten wire lasts only 30-50 hours before it needs to be replaced. This results in high operating costs.
5. Long Life
Edm molybdenum wire are very durable and can be used for much longer than brass wire. This is because the EDM spark craters left on the wire are much smaller, so the wire is not damaged and can be reused for weeks without any problems. This is especially true for coated wires, which have a pure zinc coating on a copper or brass core. This coating can be applied using electro-galvanization, which deposits the pure zinc atom by atom onto the body of the wire for a very uniform and precise thickness. It can also be applied by hot dipping, which is less precise but still effective.
Steel-core molybdenum wires have a carbon steel core for high strength and fracture resistance, and are clad with a thick layer of zinc-rich, diffusion-annealed brass for good cutting characteristics. They are a good choice for tall workpieces or when the part is being cut in poor flushing conditions.
GF Machining Solutions’ EDMMax series are not flush dependent, cutting up to three times faster than brass wire EDMs in interrupted conditions. They also consume less water than previous generation models, making them easier to maintain and run.