Electrical Discharge Machining is a metal fabrication process in which a specific shape is obtained using electrical discharges. Controlled EDM can be described as a non-traditional machining process, and it removes material by utilising a series of repeated electrical discharges between tools, known as electrodes, in the presence of a deionised fluid that cools and cleans. EDM is a popular method due to the fact that such a machine can work with any materials, no matter how tough they may be and a range of EDM Wires can be utilised.
What is a Wire EDM Machine?
Wire EDM machines work in a very similar way to normal EDM devices as described above, but they use a rapidly charged, conductive metal wire to melt the material instead. It’s important to note that no contact is ever made between the wire and the material itself, as this prevents any distortion of the wires path, while reducing the likelihood of causing damage to the part. Sparks essentially jump the gap between the wire and the part, and in the process they melt away excess material. A wire EDM machine can be used in a variety of different working environments, for a number of applications.
EDM Wires Explained
There are many EDM wires,with each type boasting their own unique selling points that make them suitable for specific purposes and materials. These include:
EDM Wire Types
- Copper wire - the very first wire used for wire EDM was copper. It’s easily accessible and highly conductive, but it has a limited cutting speed and low tensile strength. Copper wire is best suited for older EDM machines.
- Brass wire - adding zinc to copper produces brass, which is no doubt the most common EDM wire. Brass wires can have a lower melting point when they have a high zinc content, allowing faster cuts. It’s important to note that high zinc percentages can cause the crystalline structure to convert to a gamma phase, making the wire brittle and potentially difficult to draw. Brass wires are a good all-around option that can be utilised by many modern machines.
- Coated wire - coated EDM wires have a thin layer of pure zinc that has been applied to a brass or copper core. Zinc coated wires can cut quickly and do not break often, meaning they are recommended for fast roughing and finishing of steels. They can also produce a superior surface finish along with improved surface integrity.
- Diffusion-annealed wire - although wires that boast a high zinc can be great, they are tricky to produce; so, a special method of production was devised, which essentially includes a heavy coating of pure zinc being applied to either a copper or brass core. Then, annealing takes place within a special furnace, diffusing the zinc coating so that it becomes a combination of around 50% brass and 50% zinc.
EDM Wire Properties
- Tensile strength - high-tensile EDM wire offers improved edge straightness, making it the perfect choice for single-pass parts, tall parts and in fine-diameter wires to minimise the chances of wire breakage. EDM wire that has high tensile strength is also suitable for skim cuts, as it can aid geometric accuracy.
- Fracture resistance - fracture resistance of an EDM wire can be better described as wire toughness or resilience. EDM wire resists the effects of the incredibly dynamic environment of the spark gap.
- Conductivity - EDM wire boasts the ability to carry electrical current. Generally speaking, the higher the conductivity of the wire, the more power can actually be delivered to the workpiece, leading to increased cutting speeds.
- Vaporisation temperature - you need a low vaporisation temperature if you want the best flushability, as the wire surface should vaporise and convert to gaasses quickly rather than contaminating the gap.
- Hardness - not to be confused with tensile strength, the hardness of a wire refers to its ability to undergo elongation. You can find both soft and hard EDM wire, ensuring there’s always the perfect device to suit every individual requirement.
Conclusion
With any luck, this guide has helped you to better understand your options when it comes to EDM wire, ensuring it’s never been so simple to locate your ideal EDM match in no time at all. There are so many different types of EDM wires that you can choose between, so no matter what your task or material will be, you can easily locate the perfect device and accessory for your unique needs. Whether you require copper wire or coated wire, you’ll be able to do the job right with Electrical Discharge Machining.
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