Electrical Discharge Machining: Principle and Manufacturing Applications

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Electrical Discharge Machining: Principle and Manufacturing Applications

Manufacturers often turn to electrical discharge machining (EDM) whenever traditional machining methods reach their limit. The EDM process involves using thermal energy to remove excess material from an object, creating the required shape for a task. It is not the most popular CNC machining process available. However, engineers rely on it to create parts that are impossible to machine.

EDM is similar to processes such as laser cutting. It does not require or use mechanical force to remove the excess material. This is why many people consider it to be a non-traditional manufacturing process. This process helps in molding and tooling for a wide range of industries. In this article, we will examine how it works, the various types available, as well as its advantages and applications. Let’s dive right into it!

What is EDM?

You may have come across terms such as spark machining, die sinking, wire erosion, or spark eroding. Some engineers and manufacturers use these terms to refer to electrical discharge machining (EDM). But what is EDM? To simply put, EDM involves removing excess material from a workpiece with the use of thermal energy.

principle of electrical discharge machining

As mentioned earlier, the EDM process does not require mechanical force. This fabrication process ensures that engineers arrive at desired shapes only with the use of electrical discharges. It is a highly precise process that does not involve using a tool on the workpiece. When you need to work on hard materials like titanium or form complex shapes, EDM is often the way to go.

How Does Electrical Discharge Machining Work?

While the definition may seem simplistic, the physical process is a little bit more complex. The removal of material from a workpiece using EDM occurs through a series of recurring rapid current discharge between electrodes. These electrodes are separated using a dielectric fluid. Then, a voltage is sent through the dielectric fluid. It is important to note that EDM manufacturing only works for electrically conductive materials.

One of those electrodes serves to change shape to fit the exact purpose. This electrode is the workpiece electrode or the “anode.” The other electrode is the tool-electrode or the “cathode.” The basic principle behind this process is the erosion of the material with a controlled electric spark. For this to occur, the two electrodes must not come in contact.

There is the application of potential difference across the workpiece and the electrode in pulse form. As the electrode moves closer to the workpiece, the electric field present in the small gap between them increases. This continues until it reaches breakdown volume.

The electrical discharge causes extreme heating of the material. The heating leads to the melting away of some parts of the material. A steady flow of the dielectric fluid helps to remove the excess material. The liquid also assists in cooling during the machining process.

Types of Electrical Discharge Machining

The EDM process is unique and conventional. However, this does not mean that there is only one approach to this process. There are three different types of EDM. This helps to assure that there are alternative methods if one type does not fit adequately. The different types of electrical discharge machining include:

Wire EDM

Sometimes referred to as wire erosion or spark EDM, wire EDM is a popular process. It involves the use of a brass wire or thin copper to cut the workpiece. Here, the thin wire acts as the electrode. The dielectric liquid, in this case, is usually deionized water. During the wire EDM, there is the continuous unfurling of the wire from an automated feed using a spool.

wire edm

This is because the electrical discharge may become compromised by the workpiece and the wire. Therefore, there is a need for a new discharge path in the cut. This approach works very well. However, engineers must note that the wire must pass through the workpiece completely. Hence, it essentially creates two-dimensional cuts in three-dimensional parts. You tend to get results that are similar to the traditional CNC machining processes.

Hole EDM

The hole drilling EDM process is another type of electrical discharge machining. As the name implies, it helps explicitly in fast hole drilling. The electrodes for hole EDM are tubular, enabling the dielectric fluid to flow through the electrodes easily.

hole edm processing

Unlike the traditional drilling methods, hole EDM can machine very tiny and deep holes. Furthermore, these holes do not require any deburring. Regardless of the metal hardness or type, this process enables effective drilling of precision holes faster than the conventional methods.

Sinker EDM

This is the conventional EDM, also referred to as Ram EDM, die sinking, or cavity-type EDM. Cavity type because it creates complex cavity shapes for various casting applications such as plastic injection molding.

a sinker edm process

This process uses pre-machined copper or graphite electrodes to form a “positive” of the required shape. Then, there is the pressing of the electrode into the workpiece to create a negative of the original material shape. Some factors may influence the choice of electrode material in sinker EDM. These include the electrode’s resistance to erosion and its conductivity, which is usually easier to machine graphite than copper. However, copper is stronger and more conducive.

Advantages of Electrical Discharge Machining

There are several unique advantages associated with EDM. Some of them include:

1. It Can Work on Any Type of Electrically Conductive Material

When you think of EDM manufacturing, the first thing that will come to your mind is its ability to work on a wide range of materials. As long as your material is electrically conductive, EDM is always the right process. This makes it possible to machine parts that are difficult for traditional machining methods. These include parts made from titanium and tungsten carbide.

2. No Mechanical Force is Involved

Another crucial benefit of electrical discharge machining is that no mechanical force is put into the workpiece. Therefore, you don’t have to worry about producing fragile outlines. This becomes easy because there is no need for high cutting force before removing the material. Since no contact occurs between the tool and the workpiece, there is no issue of mechanical stress.

3. Enables Various Shapes and Depths

With EDM, you can reach shapes and depths that seem impossible with a cutting tool. It is an effective method for deep processing with very high tool lengths and diameter ratios. You can easily cut sharp internal corners, narrow slots, and deep ribs with the EDM process.

4. Encourages Better Surface Finish

Manufacturers also argue that injection molding surface finish is often better with EDM than traditional methods. This may be true because electrical discharge machining gives surfaces with high precision and fine finishes.

5. Can Be Used on Hardened Material

Other conventional machining processes need to be done before hardening the workpiece. On the other hand, EDM works perfectly on hardened material. Therefore, it is easy to avoid any potential deformation from heat treatment.

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Applications of Electrical Discharge Machining

EDM is particularly famous in small-volume production. Several processes are possible using electrical discharge machining. These processes include milling, turning, small hole drilling, and more. This unique process is also valuable for a wide range of industries ranging from automotive to the aerospace industry.

Being able to create unique and precise shapes, EDM helps in the following applications:

Injection Molding

Achieving the right dimension, depth, and shape of a mold is usually dependent on EDM. It is the major injection molding process used by mold manufacturers. Wire EDM is the main type used in this case.

injection molding applications of electrical discharge machining

Since injection molding requires various delicate and complex workpieces, so this is usually the best method to use. Moreover, it often produces high precision and fine EDM surface finish.

Small Hole Drilling

Electrical discharge machining is a quick and unique way to create accurate deep small holes drilling in materials, regardless of their hardness.

using edm for small hole sinking

The hole drilling process involves using a brass electrode tube to channel the electrical discharges onto the material. This helps to create holes of various small dimensions. The exciting thing is that it can make holes on inclined faces and other challenging positions.

Die Casting

EDM is also very suitable for die-making applications. Manufacturing highly tailored dies require extreme accuracy. These dies feature sharp internal corners, deep ribs, and other intricate features.

electrical discharge machining for die casting

Also, dies are often made from very hard steel alloys. These alloys are usually harder to machine with traditional methods. The hard steel alloys may require finishing prior to heat treatment, which may reduce the accuracy of details. Therefore, employing the EDM process is more appropriate.

Conclusion

Electrical discharge machining continues to be the answer for highly demanding machining applications. It helps engineers to reshape materials where traditional methods are difficult or impossible. This unique process contributes to the creation of high-quality components.

At RapidDirect, our EDM processes are the perfect solutions to your manufacturing needs. This process enables us to create high-precision cutting, and it works well for any conductive material. This way, we can serve you better, regardless of your parts requirement and applications. Upload your design file today, and you will receive an instant quote. All our services come at competitive prices.

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