Principle and Manufacturing Applications of Electrical Discharge Machining (EDM) (Part 1)

The EDM process involves using thermal energy to remove excess material from an object, creating the required shape for a task. 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?

To simply put, EDM involves removing excess material from a workpiece with the use of thermal energy. 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. EDM is often the way to go when you need to work on hard materials like titanium or form complex shapes.

How Does Electrical Discharge Machining Work?

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.

How Does Electrical Discharge Machining Work?
How Does Electrical Discharge Machining Work?

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 is the erosion of the material with a controlled electric spark. For this to occur, the two electrodes must not come in contact.

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 Electrical Discharge Machining process is unique and conventional. There are three different types of EDM. This helps to assure that there are alternative methods if one type does not fit adequately. 

Wire EDM - Hanoi Mould
Wire EDM – Hanoi Mould

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. This is because the electrical discharge may become compromised by the workpiece and the wire. However, engineers must note that the wire must pass through the workpiece completely. Hence, it essentially creates two-dimensional cuts in three-dimensional parts. 

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. 

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 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.

 

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