What is Electrical Discharge Machining?
Electrical discharge machining (EDM) is an unconventional manufacturing method that relies on the principle of erosion by electric discharge. A process discovered by Joseph Priestley, one of chemistry’s founding fathers, in 1770. But it would take another 200 years for electrical discharge machining to become a viable fabrication technique.
How Does Electrical Discharge Machining work?
Electric discharge machining takes away material from a workpiece until it has achieved its intended form. EDM utilizes the principle of electric or thermoelectric erosion, meaning that a series of rapid-firing sparks removes (or erodes) material from a workpiece. The temperatures exceed 10,000 degrees Celsius and can vaporize material from the workpiece. And while each spark only makes a minute impression, an electrical discharge machine can deliver tens of thousands of sparks per second.
As in some other electrical processes, both intentional and inadvertent, the sparking occurs between two electrodes. The machine provides the first electrode, and the second electrode is the workpiece itself. Therefore, EDM is used to fabricate electrically conductive metals and is employed when conventional machining methods fail to cut through tough, exotic metals.
Both the wire and workpiece are bathed in dielectric fluid, usually a hydrocarbon oil or deionized water, which acts as a coolant and insulator to prevent unwanted electrical discharges.
As it flows, it flushes away debris and reduces the risk of an unstable discharge that might otherwise occur in a contaminated fluid.
Automation
The automation of electrical discharge machining is nothing new, in theory, but advanced features have electrified output in various ways. For example, improved HMI (human-machine interface) and other intuitive software upgrades yield greater control and cutting stability, minimizing labor for human engineers.
Additionally, automation allows multiple processes to occur simultaneously, benefiting our clients with higher workloads, less downtime, and the resultant top-quality products at competitive prices.
Applications
EDM’s ability to craft tight shapes and effortlessly erode tough, resistant metals makes it a preferred method for producing dies and molds for die casting. Attempting to create these items using other machining methods would yield poorer quality tools with rougher features while placing undue stress on the cutting implements.
EDM is also capable of precision at minuscule scales. When equipped with a small, spinning electrode, it can consistently and accurately produce small-diameter, tight tolerance holes, as would be necessary for many precision technologies such as plane engines, automotive fuel injectors, and medical implants. Our capabilities allow precision at ever-tinier scales for the multi-industry components shrinking in size but increasing in sophistication.
Different Types of Electric Discharge Machining
Sinker EDM
The traditional electrical discharge machining technology is known as sinker EDM because it creates a plasma channel in the workpiece as it erodes material. The machine's electrode sinks into this channel to complete the desired cut.
Wire EDM
Wire EDM works according to the same thermoelectric principle as its counterpart. The difference is the type of electrode used. In this case, it's a thin wire constantly renewed through a spool. The rapid-sparking action of EDM deteriorates the wire, so the machine continually refreshes it to yield the cleanest cuts.
Hole Drilling EDM
Hole drilling EDM is similar to conventional drilling, except it utilizes thermoelectric erosion to vaporize material and form a hole. It uses a pipe-shaped electrode to achieve exceptional accuracy and tight tolerances.
EDM and Safety
Electrical discharge machining can be a safe process with appropriate care, attention, and adherence to safety standards.
Attend all operations.
Ensure that the machine's fire-extinguishing system is working properly. Provide additional fire protection equipment throughout the facility.
Make sure that the workpiece and electrode are bathed in dielectric fluid.
Keep the machines well-maintained and clean.
Guarantee that the work area is grounded and kept dry.
Wear proper attire, including any PPE (such as eyewear), and avoid jewelry or other conductive or dangling accessories.
Provide adequate ventilation and worker safety precautions, as EDM processes can produce flammable gasses or airborne particulate matter that's hazardous if inhaled.
When is EDM Needed?
Electrical discharge machining is needed when engineers tackle tough or exotic metals that resist other manufacturing methods. Since EDM works via the principle of thermoelectric erosion, it can efficiently and effectively cleave through stubborn, challenging metals. It does so gradually, delivering tens of thousands of sparks per second, each removing a bit of material from the workpiece.
EDM also provides a desirable option for creating tight, complex geometries, various fixtures, small sophisticated components, and features with thin walls. And, due to its ability to cut completely through a workpiece, it's valuable for creating apertures and other holes.
Additionally, its no-contact mode of action minimizes physical stress, making it an engineer's go-to when fabricating delicate, fragile pieces that can't stand up to other machining processes. Its many advantages combine to make EDM a stand-out selection for producing ultra-precise components in the aerospace, automotive, medical, and electronics industries.
Dialectic Fluid
In addition to the two electrodes, provided by the electrical discharge machine and the workpiece, the EDM process requires that the electrodes and the space between them be submerged in dielectric fluid. Dielectric fluid is generally deionized water or a hydrocarbon oil, such as kerosene, and isolates the two electrodes to allow high current density within the plasma channel.
This fluid is a medium for sparking and a coolant since it is not thermally or electrically conductive. It also prevents unwanted sparking, thermoelectric damage, and flushes away the debris that would otherwise accumulate as it's eroded from the electrodes.
Dielectric fluid can have a lifespan of several years, possibly around five years, though it depends on use, amperage, and other facility-specific factors. Typically, experimental results recommend replacing the fluid when cutting efficiency drops by 20% or when pulse discharge probability becomes less than 70%.
Bottlenecks of EDM Efficiency
As with all manufacturing modalities, EDM offers many advantages but also some limitations. For one, it's more time-consuming than other types of machining since each spark removes only a bit of material at a time. It may be necessary, when applicable, to subject the workpiece to conventional cutting methods before using EDM techniques for more intricate shaping.
EDM is also more expensive, requiring additional labor and costlier equipment and consumables. Additionally, EDM can only be used on electrically conductive materials, precluding its use on non-conductive materials such as ceramics or plastics. Electrical processes may also be harder to control than traditional machining processes, and thermal defects can occur if the pulse energy is not effectively managed.
What Are the Advantages of Electrical Discharge Machining?
Electrical discharge machining is preferred when working with tough but electrically conductive metals that may resist other cutting methods. EDM’s ability to create tiny apertures, internal cuts, and other fine features makes it a perfect choice for processing small, sophisticated, and delicate parts.
And since there’s no physical contact between the machine and workpiece, EDM creates no residual stress and increases the lifespan of end product parts.
It’s also exceptionally accurate, highly reproducible, and majorly error-proof. It doesn’t require much human attention and EDM-produced components don’t need additional tooling or finishing, reducing production costs and time to market.
Applications for Electrical Discharge Machining
EDM’s ultra-precise capabilities make it indispensable for crafting aerospace, medical, and military equipment. Its influence is felt domestically as well. Many of the intricate little components that power your household appliances owe their existence to this 250-year-old discovery.
Our state-of-the-art machinery and expert engineers can create highly intricate, perfectly precise turn-key components. Get a quote today to find out how Beltim & Associates can make EDM work for you!