What is EDM?

Electrical Discharge Machining (EDM) is a non-contact machining method that uses electrical energy to shape metal without the tool directly touching the workpiece. Unlike cutting, grinding, or polishing, EDM removes material through thermal energy generated by electrical discharges.

Let’s explore the basic principles and advantages of EDM.

What is Electrical Discharge?

An electrical discharge occurs when a high voltage is applied to an insulating material, causing dielectric breakdown and allowing current to flow. Common examples include lightning and static electricity.

Even the flow of electricity from a battery to power a device is a form of discharge—current flows from the positive to the negative terminal, completing the circuit.

How EDM Works

EDM creates a series of electrical sparks between an electrode and a workpiece submerged in dielectric fluid. These sparks generate intense heat that melts the material locally. The molten metal is then rapidly cooled and expelled by vaporization, removing unwanted material and forming the desired shape.

Electrodes made of copper or graphite are typically used, and the process takes place inside specialized insulating oil or fluid (dielectric).

Types of EDM

1. Die-Sinking EDM

Uses a pre-shaped electrode with the inverse of the desired geometry. The electrode is controlled via NC (Numerical Control) machinery to move across the X and Y axes and form complex shapes.

Micro-hole EDM, using thin rod electrodes, allows the machining of deep, narrow holes that are difficult to achieve by traditional drilling.

2. Wire EDM

A thin wire acts as the electrode and cuts through the workpiece like a wire saw. It’s also automated using NC controls and is ideal for precise profile cutting.

Advantages of EDM

1. High-Precision Machining
   Achieves micrometer-level accuracy, suitable for intricate and delicate features.
2. Can Process Hard Materials
   Materials like tungsten carbide and hardened steels can be machined without needing expensive cutting tools.
3. Non-Contact Machining
   No mechanical stress is applied, reducing the risk of residual stress, deformation, or burrs.
4. Continuous Cooling During Machining
   The dielectric fluid keeps the workpiece cool, preventing thermal distortion.

Disadvantages of EDM

1. Slow Machining Speed
   Material is removed gradually, making the process unsuitable for high-volume production.
2. Cannot Machine Non-Conductive Materials
   The workpiece must be electrically conductive; otherwise, no discharge occurs.
3. Electrode Wear
   Electrodes erode during use, especially at the edges, requiring replacement to maintain precision.

Process-Specific Drawbacks

• Die-Sinking EDM: Requires custom electrode fabrication for each shape, increasing time and cost.
• Wire EDM: Since the wire is vertically aligned, it’s limited in applications where through-cuts are not possible.

About EDM Oil

In wire EDM machines, water is mainly used as the working fluid, whereas in shape EDM machines, hydrocarbon-based EDM oils are used. Initially, kerosene (paraffin), spindle oil, and hydraulic oil were used as EDM fluids, but with the development of low-viscosity petroleum-based oils, they became widely used. Later, due to concerns regarding fire hazards, odors, and skin irritation, synthetic hydrocarbon-based oils began to be more widely adopted. However, synthetic oils generally result in slower processing speeds compared to petroleum-based oils, which can reduce productivity. This has led to increased interest in the development of synthetic EDM fluids with better performance.

Reasons for Using EDM Oil in the EDM Process

1. Quick Recovery of Insulation and Stable Processing
   The use of EDM fluids helps quickly restore insulation, ensuring stable processing throughout the operation.
2. Cooling and Removal of Debris
   EDM generates debris during the process, which is rapidly cooled and removed by the fluid, maintaining the insulation state of the discharge gap. This allows for a continuous EDM cycle without loss of processing efficiency.
3. Maintaining Discharge Uniformity
   If conductive debris remains between the workpiece and the wire, the discharge can become irregular, leading to instability in the discharge gap and affecting processing accuracy. EDM fluid helps maintain uniform discharge.
4. Higher Flashpoint for Fire Prevention
   Compared to previously used kerosene or petroleum, EDM fluids with a higher flashpoint (average 100°C) reduce the risk of fire and prevent property loss. Kerosene and petroleum had lower flashpoints, exposing many companies to fire risks.
5. Reduced Consumption and Cost Savings
   The low volatility and reduced natural consumption of high-flashpoint fluids help reduce costs and improve overall cost efficiency.

For all of these reasons, EDM fluids play a critical role in ensuring “stable processing” in EDM operations.

Oxidation and Maintenance of EDM Oil

Although EDM fluids do not oxidize easily, using oxidized fluid can lead to several issues:

• Insulation recovery is impaired, causing increased processing time.
• The discharge gap widens, reducing precision.
• Abnormal discharges occur.

To prevent these issues, regular maintenance, including fluid replacement, is essential.

Our EDM Fluid Products

Our company has long recognized these issues and has developed high-quality EDM fluids using polymerized hydrocarbon-based formulas. Our EDM fluid excels in cooling and cleaning properties, offers low viscosity and high flashpoint, providing excellent insulation and reducing extreme wear, making it ideal for ultra-precision machining. Additionally, we use additives to prevent smoke and odor, maintaining a clean working environment and ensuring stability for the user.

We offer various resources and solutions to assist in your processing needs. Please feel free to contact us with any inquiries.

Dyna Co., Ltd.
Industrial Lubricant Solution
E-Mail : dyna@dynachem.co.kr
Web : dyna.co.kr/en/