EDM or electric discharge machining is a machining technique that makes parts without the need for direct contact with the workpiece. It erodes the surface of conductive materials through the use of electricity. EDM can maintain good surface finishes even on complex and sensitive items since no EDM tool makes physical contact with the workpiece.
The method is divided into subtypes for drilling, wire, and die. EDM facilitates the manufacture of different parts and components, including die molds and medical equipment like pacemakers, as well as hip and knee implants.
In this article, we’ll discuss electrical discharge machining, how it works, the types of materials used for the process, and when to use it for manufacturing. Do read on.
What’s Electrical Discharge Machining (EDM)?
So, what is EDM machining? It is an alternative machining technique used for making parts that would be difficult to make using traditional machining practices. It is important to note that it only works on conductive metals. The process involves the use of electricity to erode the surface of a workpiece. There is usually no contact between the tool used during the cutting process and the workpiece, thus guaranteeing that parts produced using this process have the best surface finish.
In the 1960s wire EDM was developed, and the first wire EDM machine was launched in the Soviet Union in 1967. Since then, the EDM process has become more robust and advanced.
The major purpose of the EDM process is that it facilitates the creation of parts with delicate or thin walls. Parts that risk damage when machined using traditional methods. It is a contactless technique that guarantees high precision and a seamless surface finish.
How EDM Machining Works
Another popular question is; How does EDM work? Well, to kick start the process, a soft electrode made of graphite creates a spark between the electrode and the target area. The spark created usually has a temperature ranging between 14,500 and 21,500 ºF and when it occurs, it vaporizes or cuts part of the workpiece. After the cut/ vaporization, a dielectric fluid, which is another component of the system, carries the vaporized part away from the already machined region of the workpiece. This occurs repeatedly until the part is completely machined.
EDM engineering can machine most materials that conduct electricity flawlessly, aside from premium nickel often used in aircraft manufacture. However, with the aid of specific electrodes, the EDM technique can be great for machining parts using this material.
Key Components of EDM Machines
There are several key components of an electrical discharge machine, each playing a specific role in ensuring the production of parts that are precise and accurate.
Power Supply
Power Supply powers the entire system. It supplies the spark necessary to erode the workpiece. This component also helps regulate the voltage, current, and frequency of electricity supplied to the system. The regulation is based on the properties of the job at hand. In EDM, the power supply has to be optimal, as it runs the whole process.
Electrode
The electrodes integrated into this system boast exceptional conductivity. When positioned near the workpiece, they are designed to initiate a spark effectively. In an EDM system, common materials for electrodes include graphite, copper, tungsten, brass, and various metal alloys. The specific choice of electrode material typically depends on the EDM application, whether for wire, die, or tube processes. Notably, during the EDM operation, the electrode maintains a gap from the workpiece, ensuring there is no direct contact.
Dielectric System
The dielectric system serves as the fluid component in an EDM setup, consisting of non-conductive lubricating oil or deionized water. This fluid plays a critical role, not only by cooling the system but also by removing eroded materials from the machining zones. Without an effective dielectric system, these particles could migrate toward the electrode, potentially bonding with it and damaging the tool. Therefore, it is crucial to maintain a constant circulation of the dielectric fluid. Additionally, this system is essential for preventing untimely sparks during the machining process.
Servo Control System
The primary role of the servo control system in an EDM setup is to manage the gap between the electrode and the workpiece, enhancing the efficiency of spark generation. Beyond just spatial adjustments, this system is pivotal in regulating the actual spark production during the EDM manufacturing process.
Control Panel
This component is one of the most important parts of an EDM system. It manages the movement of parts, as well as the timing of electrical discharge. The control panel also makes sure EDM cuts are more accurate and precise.
Three Types of EDM
There are three major types of EDM. These different methods cater to a wide range of conductive materials, and they include:
Die-sinking EDM
Sometimes referred to as “ram” or “cavity” EDM, die-sinking EDM operates by utilizing discharge from an essentially 2D electrode. An intricate three-dimensional end to this two-dimensional electrode can be elevated a short distance on the Z-axis to remove debris and repeatedly descend to arc erode into the work. The electrode in question has a complicated end form devoid of undercuts and can take on any cross-sectional shape. To erode the correct cavity form into hard materials, the sinker type requires precision EDM machining of copper and/or graphite electrodes.
Furthermore, using sinker EDM machining reduces the need for post-processing to enhance surface quality or harden it. It is perfect for fabricating dies and molds because of its ability to create deep ribs and sharp inside corners.
Wire EDM
Known as wire-cut EDM, this process erodes material by sparking between the wire and the workpiece, using a wire as the “cutter.” Wire EDM is a type of electrical discharge machining that uses a very thin wire usually around 0.05mm to 0.35mm in diameter for its operation. This type of EDM finds application in the production of automotive and aerospace parts, blanking punches, and extrusion dies, as well as medical and dental devices.
In the electrical discharge machining cutting process, the wire electrode passes through and discharges along the entire length of a cut. Though its complexity has increased, the technology was originally designed to conduct 2D cuts in hard materials—in other words, cuts that could only be made along a part’s X and Y axes, with the material’s thickness measured along the Z-axis.
By offsetting the wire rollers, wire EDM can cut at controlled angles to the Z-axis. The later addition of a rotational axis led to powerful 5-axis wire EDM centers.
Wire EDM only machines through cavities—not blind ones. Top and bottom wire guides ensure cutting accuracy and adjust vertically to match the workpiece height. The process also requires a pre-made through-hole for the wire to pass through, known as threading.
Wire EDM is ideal for producing automotive and aerospace parts, blank punches, and extrusion dies.
Hole-drilling EDM
Hole drilling is a vital tool in many industries, including the aerospace, medical, technological, and scientific industries. This is because it presents the only method for cutting long, straight, tiny boreholes. A hole that perfectly reflects the tool’s profile is eroded using a straight electrode. One merit of hole-drilling EDM is that it keeps exact dimensional correctness the whole way through the hole. This technique is ideal for making start holes in wire EDM cutting, removing broken taps and drills in machinery, and creating cooling channels in turbine blades.
This technique can produce straight holes of any depth and with a diameter of 0.0015″ or more, even with small diameters and high aspect ratios. An EDM drill machine makes it possible to drill both blind and through-holes, with smooth walls, in materials that would otherwise be impossible to deal with. Holes made using hole drilling EDM have a smooth enough surface finish right out of the machine to be used as bearing surfaces without further post-processing.
Suitable EDM Types for Complex Cavities
Sinker discharge machining is the most effective EDM method for producing parts with complex or intricate cavities. This is because it is more appropriate for drilling, deburring, finishing, 3D contouring, and other machining processes. Sinker EDM is particularly ideal for making parts that cannot be produced using conventional machining techniques, as its ability to cut through a material is not affected by the material’s hardness. Its cutting ability makes sinker EDM the go-to method for working on parts with complex internal features like cavities and pockets.
When to Choose EDM Machining
EDM performs a variety of tasks, such as drilling long or fine holes in any metal, extracting precise 2D shapes from difficult-to-work materials, and creating complex cavity shapes, which are essentially 3D relief shapes cut into the bottom face of 2D blind cavities.
One can also use electrical discharge machining (EDM) for cutting extrusions, rotary forms, and sharp internal corners. Looking to engrave on a hard material like tungsten? EDM is also ideal. It is important to note that with virtually no tension applied to the workpiece, EDM can create flawlessly finished one-step drilled holes in any cross-section.
Tips: EDM vs Traditional Machining Process
EDM uses electrical sparks to cut materials without physical contact, reducing the risk of deformation and ensuring high dimensional accuracy and surface finish. In contrast, traditional machining relies on contact-based cutting tools, which generate heat and can distort the part. While EDM offers better precision, conventional methods are typically faster, more material-versatile, and more cost-effective.
Advantages and Limitations of EDM
| Advantages | Limitations |
| Design Flexibility | Limited Material Compatibility |
| Easily machines complex shapes and hard materials like tungsten and nickel. | Only works on electrically conductive materials; heat can alter metal properties. |
| No Mechanical Deformation | Slow Material Removal |
| Contactless process prevents warping and damage to delicate features. | Lower cutting speed makes it unsuitable for large-scale production. |
| Precision and Accuracy | High Electrode Cost |
| Ideal for high-tolerance parts in aerospace and automotive applications. | Custom electrodes for die sinking increase cost, especially at low volumes. |
| Excellent Surface Finish | High Energy Consumption |
| Leaves smooth surfaces with minimal post-processing. | Consumes a lot of electricity, resulting in a larger carbon footprint. |
Conductive Materials for the EDM Process
Almost any conductive material can be machined using electric discharge machining without too many difficulties. Materials that are not conductive, such as composites, glass, ceramics, plastics, and wood, cannot be worked with by EDM. The substance of the workpiece must carry electricity since it is a component of the spark’s circuit. Materials suitable for EDM machining include:
| Material | EDM Applications |
| Brass | Excellent conductivity and machinability, ideal for wire EDM, die sinking, and drilling. Produces smooth surfaces, precise cuts, and intricate shapes. |
| Aluminum | Lightweight with high thermal conductivity. Used in wire EDM and die sinking for efficient heat removal and detailed, complex parts. |
| Steel | Hard material challenging for traditional machining; EDM machines steel precisely for durable molds, dies, and complex parts. |
| Copper | Great electrical conductivity and ductility. Enables accurate wire EDM cuts, used in die sinking for molds, and effective heat dissipation in drilling EDM. |
| Nickel | Resistant to heat and corrosion; difficult to machine conventionally. EDM easily cuts nickel for detailed, durable parts in wire and die sinking processes. |
| Tungsten | High melting point and hardness. EDM machines tungsten for wear-resistant molds and parts, especially with die sinking. |
Specific Industries and Examples of EDM in Manufacturing
| Industry | Description | Examples |
| Medical Industry | EDM is a critical technology in the medical sector, known for its high precision and accuracy—essential for manufacturing medical devices where even slight deviations can have serious consequences. | Cochlear implants, pacemakers, neurostimulators, dental parts like abutments, crowns, bridges |
| Aerospace Industry | EDM is invaluable in aerospace for fabricating complex parts with precise dimensions, crucial for aircraft performance and safety. | Stator vanes, turbine discs, compressor discs, landing gear components, fuel system parts, dies, aero blades, metallic molds |
| Manufacturing Industry | Precision is key, so EDM is widely used for making plastic die molds, extrusion dies, die sinking, gears, threads, and intricate machinery parts. | Plastic die molds, extrusion dies, die sinking, gears, threads |
| Electronics Industry | EDM benefits the electronics industry by working only with conductive metals, producing parts that must fit perfectly for optimal function. | Connectors, sensors, switches, electrodes, dies, masks |
Cost Considerations When Choosing Electrical Discharge Machining
When deciding whether to choose EDM for your machining, here are some cost considerations to keep in mind:
Machine Investment
The initial investment into a machine is on the high side for EDM machinery. This is particularly true for more advanced models. So, keep this in mind when considering EDM machines for making your parts. The cost of the machine makes EDM impractical for short production runs, as it would impact the cost of production greatly.
Operational Costs
Operational cost goes a long way in determining the total cost of production and, by extension, product profitability. The operational costs of EDM are quite high because the technique involves the use of different components such as electrodes, wires, and dielectric fluid. Also, the process runs purely on electricity, and the energy consumed adds to the overall operational costs.
Material Costs
Material costs impact production costs greatly, as the higher the material consumed, the higher the cost of production. Since there is minimal material waste when machining using EDM, the material cost is lower than that incurred when machining traditionally. The lower material costs also translate to lower operational costs.
Machine Maintenance and Upkeep
As with every machine, routine maintenance is important when using EDM too. Also, remember that the higher the frequency of maintenance, the higher the production costs. Nonetheless, it is important to carry out routine maintenance on the EDM machine to ensure its optimal accuracy and effectiveness.
Labor Costs
Acquiring the services of skilled labor costs more, depending on the qualifications of the laborer. EDM machines are complex to operate and often require the services of an expert EDM operator, which would impact operational costs. It is also important to note that the exact labor cost often depends on the EDM technology’s complexity.
Productivity and Turnaround Time
With EDM, it is possible to manufacture complex and intricate parts in a single setup as opposed to traditional machining, where multiple setups are necessary. This considerably increases productivity and turnaround time, reducing the time spent making parts and, by extension enhancing time to market. However, it is best to remember that EDM machines are slower than their CNC counterparts.
Tool Replacement and Design
Replacing worn-out tools costs money and when done frequently, impacts operational and total production costs. EDM cutting tools wear down at a substantially lower rate than their traditional machining counterparts. This helps save money on tool replacement and repairs and also improves the accuracy of parts.
Choosing the Right EDM Services
When choosing the right EDM service provider, it is best to look for providers with experience in the industry. Go for a service that provides different EDM techniques like sinker, wire, and hole drilling. It is also best to verify their machining capabilities, comparing their EDM equipment to the size and complexity of your project.
Also, when choosing an EDM service for your needs, consider communication as it is essential to make sure your parts get to you when they are due. Then consider their pricing about other service providers as well as turnaround time.
Conclusion
EDM is a productive machining technique that makes it easier to produce highly accurate products. Also known as electrical discharge machining, it offers benefits such as high precision and quality surface finish, as well as limitations including material versatility, speed, and cost of manufacturing. This article also touched on the different types of EDM technologies, including hole drilling, sinker, and wire, and delved into the sinker EDM vs. wire EDM debate, ensuring you make informed decisions when picking one for your needs.
Looking to make parts using EDM? Then RapidDirect is just the company for you. We are a versatile manufacturing company offering a comprehensive range of services, including EDM, CNC machining, sheet metal fabrication, 3D printing, and more. Regardless of your production scale, whether prototyping, small-scale, or large-scale manufacturing, we guarantee high-quality parts with one of the fastest lead times in the industry.
FAQs
While both methods facilitate the production of parts, they operate on different principles. For instance, EDM uses an electric spark to cut through a workpiece, while CNC machining uses a cutting tool to do so.
The purpose of EDM machining is to work on materials that would be impossible to machine using conventional practices. The process cuts materials by eroding the surface of the workpiece using electricity.
Although wire EDM accuracies of +/- 0.00004″ (0.001mm) are occasionally quoted, +/- 0.0002″ (0.005mm) is more commonly recognized. In actuality, several factors, including the intended surface smoothness, the workpiece’s properties, and the amount of machining time available, affect EDM accuracy.
