Among most modern industrial manufacturing techniques, electrical discharge machining stands out due to its high precision and minimal wear or tear on the target material. In this article, I’ll describe everything about this machining process, including its applications and the key components of the EDM system.
Moreover, I will talk about the advantages and disadvantages of EDM machining to determine its suitability in modern machining. Towards the end, we’ll examine how EDM differs from other machining methods like CNC. The article will also outline the common materials that can be EDM-machined and the dangers associated with this machining process.
History of development
Electrical discharge machining industry was first developed in the 1940s as a way to machine difficult-to-machine materials like tungsten. It wasn’t until the 1970s that EDM began to be used more widely, as advances in technology made it possible to create smaller and more precise electrical discharges. Today, EDM is used in a variety of industries, from aerospace to medical device manufacturing.
What Is Electrical Discharge Machining?
Electrical discharge machining, or EDM, is a subtractive manufacturing process that uses thermal instead of mechanical energy to melt or vaporize excess material from a workpiece. Essentially, the process entails converting an electrical discharge into thermal energy, creating a hot electrical spark that then works on the target material.
Also known as spark machining, EDM works based on the principle of electricity conduction, hence it only supports materials that are good conductors. The electrical discharge machining process is known for its high accuracy, regardless of the hardness or softness of the material. It’s also suitable for cutting complex shapes, unlike traditional methods.
How the EDM Process Works
The electrical discharge machining process comprises two core parts: 1) an electrode to generate the sparks, and 2) the workpiece or simply the material under processing. Both components connect to a power supply, where the electrode transports one side of the charge while the workpiece carries the other.
When the two opposite charges get closer, a white hot electrical spark is generated from the electrode and jumps to the workpiece, creating high temperatures between 14,500 and 21,500 degrees Fahrenheit within the spark gap. This impact causes the workpiece/material to melt and erode.
Given the high temperatures in the system, a dielectric fluid functions as the insulating component. Therefore, the electrode and the workpiece stay inside the fluid for the entire process. Besides controlling the electric spark, the dielectric fluid also cools the system and flushes away the eroded particles.
Types of Electrical Discharge Machining Processes
We can group electrical discharge machining processes into different types, depending on the electrode shape and the general process setup. The three standard EDM process types include:
1. Die Sinking EDM
During this type of electrical discharge machining process, a die is attached (‘sunk’) into the workpiece with the availability of a dielectric fluid. As a result, repeated electrical discharges across the electrode and the workpiece generate a negative impression of the die directly in the workpiece.
Therefore, the workpiece assumes a negative shape of the die. The other names for this conventional EDM process include cavity-type, sinker, or ram EDM.
2. Wire EDM
This EDM process type uses a hair-thin wire (about 0.05 mm to 0.35 mm) to conduct electrical discharge to the target material. While serving as an electrode for the process, the wire goes vertically through the material, creating two microscopic eroded dimensions. Primarily made of brass or copper, the wire is placed between diamond guides as it keeps burning.
At the same time, another fresh wire is constantly ejected from a spool to maintain the accuracy and precision of the final product.
3. Hole Drilling EDM
When in operation, this EDM method uses tubular electrodes to drill small but deep holes in the target material. This technique is mostly used when placing intricate cavities in a material. Though it works similarly to the other two methods, the dielectric fluid in hole drilling EDM is supplied using the electrode itself.
Unlike most traditional machining processes, hole drilling EDM doesn’t leave any burrs.
What Are the Key Components of an EDM System?
An efficient electrical discharge machining system comprises the following core parts:
Power supply: Provides the necessary electrical energy to erode material from the workpiece.
Electrode: This normally comprises a conductive material like copper or graphite, which is used to develop intricate shapes within the workpiece.
Dielectric fluid: Serves as the system’s coolant and helps push away the eroded material from the machined area.
Control unit: Manages the movement of machine parts and the precise release of electrical discharges.
Work tank: This component houses the workpiece and the dielectric fluid, ensuring the system precisely crafts the raw material into the desired machined output.
Flushing system: Provides a constant flow of dielectric fluid to the EDM system, cools the other components, and supports the appropriate removal of eroded particles.
Servo control system: Maintains and adjusts the electrode-workpiece gap, hence managing the spark generation process.
Workpiece holder and fixture: Helps to hold the workpiece in place during the entire machining process, ensuring it remains stable for efficient precision from the electrode.
Application Areas of Electrical Discharge Machining
Thanks to its precision and versatility, EDM applies to different industrial processes, especially where traditional machining methods have failed. The most common application industries for this type of machining include:
Medical devices: Manufacturers use EDM to produce surgical tools and intricate implants.
Aerospace: For manufacturing critical components like engine parts and turbines.
Defense: Develop essential parts for military equipment and vehicles.
Tool and die making: EDM can generate dies, molds, and stamps.
Research and development: Used to create experimental parts and prototypes.
Automotive: Production of molds and dies necessary for car components.
Manufacturing machinery: Used to generate complex machinery parts, including gears and threads.
Electronics: Used in the large-scale production of semiconductor parts and other connectors.
EDM is also applicable in other areas of the energy, telecommunication, and manufacturing sectors.
What Are the Advantages and Disadvantages of EDM?
To determine if electrical discharge machining is the right choice, it’s important to analyze its advantages and disadvantages. We can analyze this manufacturing process based on its benefits and challenges as follows:
Advantages of Electrical Discharge Machining
It can create intricate and complex shapes, a feature not possible with most conventional machining methods.
Minimizes mechanical stress and tool wear since there’s no direct contact with the workpiece.
It provides high precision and accuracy, which is critical for the aerospace and medical device manufacturing industries.
It conveniently machines hard materials that are often challenging for traditional methods.
High-quality surface finishes on the final product.
It can work on various materials as long as they can conduct an electric current.
Disadvantages of Electrical Discharge Machining
Only supports electrically conductive material.
Has high operational costs, ranging from power consumption to equipment maintenance.
If not properly disposed of, the used dielectric fluid may result in environmental concerns.
Setting up an EDM machine is difficult, especially if working on a complex job.
EDM vs CNC Machining: What Is the Difference?
Both electrical discharge machining (EDM) and computer numerical control (CNC) machining are modern manufacturing methods. While EDM suits hard, complex, and delicate parts, CNC machining thrives in general-purpose manufacturing. The table below shows a detailed comparison of both machining methods.
EDM vs CNC Machining Comparison Table
| Parameter | EDM | CNC Machining |
| Material Removal Method | Thermal (using electrical discharges) | Mechanical (via cutting tools) |
| Material Compatibility | Only works on conductive material | Supports both conductive and non-conductive materials |
| Precision and Finish | Extremely precise and excellent surface finish | Highly accurate, but the final product may need polishing |
| Tool-Workpiece Contact | No direct contact | There's direct contact between the cutting equipment and the workpiece |
| Machining Speed | Slower because of spark erosion | Faster |
| Tool Wear | Less mechanical wear | The cutting tools could wear out over time |
| Best For | Hard metals, molds, dies, and complex shapes | Large production runs, general manufacturing, and prototypes |
EDM is generally best for precision work on hard conductive materials, while CNC machining is mostly suitable for multi-material fabrication and mass production.
When To Use EDM
- Manufacturing punch mould, forging mold and die casting dies，
- Machining small holes, malformed holes and screw holes ，
- Cut out parts from sheet metal，
- Machining parts of complex shape,
- Processing small mirror parts, surface roughness Ra< 0.2μM,
- Deep hole processing, mesh parts processing.
EDM is typically used when other machining processes are not able to produce the desired results. EDM can be used to machine parts with very complex shapes and tight tolerances. EDM can also be used to machine parts made from hard materials that are difficult to machine with other methods.
When To Use CNC Machining
- Any part can be use CNC machining, other manufacturing processes cost less than CNC machining for some special parts，
- Suitable for non-decorative surfaces, as well as textured surfaces.
- More precise parts are needed. Milling makes it easier to maintain tight tolerances.
- Non-conductive materials, EDM can only process conductive materials.
CNC machining is typically used when parts do not require very tight tolerances or complex shapes. CNC machining is also a good choice for low-volume production runs. CNC machining can be used to create parts from a variety of materials, including metals, plastics, and composites.
What Materials Can Be Machined Using EDM?
As I’ve already outlined, electrical discharge machining primarily works with material that conducts electric current. Therefore, non-conductive materials like plastics, glass, ceramics, or wood are unsuitable for this machining process. The common materials that manufacturers can use in EDM include:
Graphite.
Steel.
Tungsten Carbide.
Aluminum.
Copper.
Titanium.
Gold.
Brass.
Inconel.
Kovar.
Nickel.
When to Use Electrical Discharge Machining (EDM machines)
The common scenarios where EDM is ideal include:
When you need complex geometries or fine details.
When no mechanical stress on the workpiece can be tolerated.
When working on conductive materials only.
When machining hard materials like tungsten carbide or hardened steel.
When the process requires high precision and a smooth surface finish.
When working on difficult shapes or blind holes.
Dangers Associated with Electrical Discharge Machining
Despite being a high-precision machining process, EDM also comes with some risks that require strict safety measures. For example, the high voltages applied during manufacturing may lead to an electrocution hazard if you don’t follow the appropriate safety protocols. Workers will therefore need to follow appropriate safety guidelines to minimize electrocution incidents.
Moreover, the dielectric fluid used on the EDM machine may pose fire risks because of the high temperatures originating from the electrical sparks. As a result, appropriate cooling systems are necessary. Also, ensuring that your working area is properly ventilated safeguards against the accumulation of toxic fumes emitted during fluid breakdown.
Conclusion
This article has outlined everything you need to know about electrical discharge machining, including how it works, the EDM process types, key components, applications, advantages, and disadvantages. EDM machining stands out from other techniques due to its accuracy, high precision, and the ability to work on intricate and complex shapes.
EDM should be your go-to solution if you’re looking for an alternative machining method with minimal mechanical stress and tool wear. Do you have any further questions, or are you just eager to learn more about this versatile machining process? Don’t hesitate to contact us today. We’re more than eager to answer all your queries.