The Principle of Electrical Discharge Machining Is So Simple, Its Role And Importance In Machining
Knowledge

The Principle of Electrical Discharge Machining Is So Simple, Its Role And Importance In Machining

The principle of electrical discharge machining is simply a thermal processing method that converts electrical energy into heat energy of the work piece to quickly melt the work piece.
Published: May 20, 2020
The Principle of Electrical Discharge Machining Is So Simple, Its Role And Importance In Machining

Definition of Electrical Discharge Machining

Electrical Discharge Machining (EDM) is a manufacturing process that generates sparks by discharge to make the workpiece into the desired shape. The dielectric liquid separates the two electrodes and applies a voltage to produce a rapidly and periodically changing current discharge to process the material. One of the electrodes is called a tool electrode, or pole head, and the other electrode is called a workpiece electrode, or simply a workpiece. In the process of electrical discharge machining, there will be no actual contact between the tool electrode and the workpiece electrode.

When the potential difference between the two electrodes increases, the electric field between the two electrodes also increases until the electric field strength is higher than the dielectric strength. At this time, dielectric breakdown occurs, and current flows through the two electrodes. This phenomenon is the same as the capacitor collapse, removing part of the electrode material. When the current stops, the new dielectric will flow into the electric field between the electrodes, excluding solid particles, and the insulation of the dielectric is restored. After the current flows, the potential difference between the two electrodes will return to before the dielectric breakdown, so that a new dielectric breakdown can be repeated.

Machining Process

Electric discharge machining is commonly used in mold processing: EDM and wire cutting. The electrical discharge machining referred to here mainly refers to wire cutting, although the same is an electrical discharge, the efficiency is very different.

The working principle of electrical discharge machining is: between the machine tool and the workpiece (positive and negative electrodes), a method of machining to remove excess material by electrical corrosion during electrical discharge to achieve the size and shape quality of the remaining workpiece. Take discharge as an example:

Electrode:The electrode selection material needs good conductivity, high melting point, easy processing, and corrosion-resistant materials. Common materials are copper, graphite, copper-tungsten alloy, and molybdenum. Copper and molybdenum wire are the main wire cutting materials. When processing, the electrode and the product will be corroded at the same time, but because of the characteristics of the electrode, the degree of corrosion is much smaller than the amount of erosion of the workpiece, which can be almost ignored.

Liquid Coolant:The main function of the liquid coolant is not cooling, but as a discharge medium, which plays a role in cooling and chip removal during processing. The requirements are low viscosity, high melting point, and relatively stable, non-volatile materials, common are: kerosene, deionized water, and emulsion.

After the pulse voltage is applied between the machine tool electrode and the workpiece, once there is a proper gap between the workpiece and the electrode, the current will break the medium between the workpiece and the electrode, and a connected discharge channel appears.
The discharge channel will instantly generate high temperatures, causing the surface of the workpiece to melt or even vaporize. It rapidly shrinks and explodes at the discharge gap. A small part of the surface of the workpiece is eroded and thrown out, and a huge electrical pit appears.
After the completion of one electrical discharge machining, the two electrodes will quickly return to a safe distance, relying on the dielectric to restore insulation. In this way, the surface of the workpiece is gradually eroded by the pulse voltage repeatedly acting on the workpiece and the electrode, but this process is very slow.

Electric Discharge Machine

Electrical Discharge Machine(EDM), Die-sinking EDM, also called cavity type EDM or volume EDM consists of an electrode and workpiece submerged in an insulating liquid such as more typically, oil or, less frequently, other dielectric fluids. The electrode and workpiece are connected to a suitable power supply. The power supply generates an electrical potential between the two parts. As the electrode approaches the workpiece, dielectric breakdown occurs in the fluid, forming a plasma channel, and a small spark jumps.
These sparks usually strike one at a time because it is improbable that different locations in the inter-electrode space have identical local electrical characteristics which would enable a spark to occur simultaneously in all such locations. These sparks happen in huge numbers at seemingly random locations between the electrode and the workpiece. As the base metal is eroded, and the spark gap subsequently increased, the electrode is lowered automatically by the machine so that the process can continue uninterrupted. Several hundred thousand sparks occur per second, with the actual duty cycle carefully controlled by the setup parameters. These controlling cycles are sometimes known as "on time" and "off-time." The on-time setting determines the length or duration of the spark. Hence, a longer on time produces a deeper cavity for that spark and all subsequent sparks for that cycle, creating a rougher finish on the workpiece. The reverse is true for a shorter time. Off time is the period of time that one spark is replaced by another. A longer off time, for example, allows the flushing of dielectric fluid through a nozzle to clean out the eroded debris, thereby avoiding a short circuit. These settings can be maintained in microseconds. The typical part geometry is a complex 3D shape, often with small or odd-shaped angles. Vertical, orbital, vectorial, directional, helical, conical, rotational, spin, and indexing machining cycles are also used.

Some of the advantages of EDM include machining of:

  1. Complex shapes that would otherwise be difficult to produce with conventional cutting tools.
  2. Extremely hard material to very close tolerances.
  3. Very small workpieces where conventional cutting tools may damage the part from excess cutting tool pressure.
  4. There is no direct contact between tool and workpiece. Therefore delicate sections and weak materials can be machined without any distortion.
  5. A good surface finish can be obtained.
  6. Very fine holes can be drilled.

Some of the disadvantages of EDM include:

  1. The slow rate of material removal.
  2. Potential fire hazard associated with use of combustible oil-based dielectrics.
  3. The additional time and cost used for creating electrodes for ram/sinker EDM.
  4. Specific power consumption is very high.
  5. Power consumption is high.
  6. Electrically non-conductive materials can be machined only with specific set-up of the process.
Published by May 20, 2020 Source :wikipedia Source :kknews Source :yawjet

Further reading

You might also be interested in ...

Headline
Knowledge
What is Laser Cutting and Uses?
There is more than one type of laser cutting. It can use different medias to generate lasers of different wavelengths, so the scope, characteristics and functions of the applications are different. In the following, the article will take you to understand the uses of laser cutting in different fields, so that you can better understand the laser cutting technology.
Headline
Knowledge
What is a Metal Shredder? Used in the Steel Industry to Manufacture Scrap Steel Resources
With the rapid development of the iron and steel industry, the iron steel industry has gradually shown contradictions such as insufficient natural resources, excessive energy consumption per ton of output, and environmental pollution. As the second mining industry of the iron and steel industry, scrap steel resources have the advantages of saving energy, reducing pollution, protecting the environment, recycling, etc., and its influence will be increasing.
Headline
Knowledge
What is A Punch? Introduction of Punching Principles, Types and Materials
A punch, also known as a punch press, is a forming process technology. There are many kinds of it. Due to different structural principles, the price and processing effect will change in response, but they all have the same structure. With the rapid development of the stamping industry, competition in all walks of life has increased. "Punches are also used in various industries, such as aerospace, education, auto parts, diving equipment and so on.
Headline
Knowledge
What is an Injection Mold?
An injection mold is a tool for producing plastic products; it is also a tool for imparting complete structure and precise dimensions to plastic products. Because the production method is to inject the plastic melted at high temperature into the mold through high pressure and mechanical drive.
Headline
Knowledge
What is a Belt Drive?
A method of transmitting rotational force between two separated shafts using pulleys and belts. The rotation speed ratio is inversely proportional to the diameter of the two pulleys, and it can slide when the load is excessive to prevent mechanical damage.
Headline
Knowledge
What are Welding and Welding Types?
Welding refers to the joining or fusing of workpieces by heating and/or compression to form a continuum. The fusion of weldments can be based entirely on the heat generated by the arc to fuse the weldments.
Headline
Knowledge
What Do You Know About Planetary Reducer?
Planetary reducer has been in existence for more than 30 years. During this long period of time, planetary reducer has gradually entered the field of automation from only appearing in high-end equipment in Europe and America, and has been widely used in machine tools, semiconductors, and packaging industries in recent years. The equipment in the medical food industry, aerospace and other fields will be used with planetary reducers. High, medium and low power servo motors with planetary reducers have become standard. What are the applications and advantages of planetary reducers? This article will let you know more about planetary reducers.
Headline
Knowledge
What are the Classifications of Packaging Equipment?
Packaging involves all walks of life. Manufacturers that produce physical products and need to enter the circulation field all need packaging processes, especially in light industry, and packaging equipment is indispensable. With the development of all walks of life, more and more industries use packaging equipment to reduce the labor intensity of the packaging process, improve product quality, reduce investment costs, and improve the labor environment. In the following, we are going to learn more about the common classifications of packaging equipment.
Headline
Knowledge
What is Paint Treatment Technology?
The baking paint treatment can give metal various colors and different textures. It is painted on the metal surface as a surface treatment, which has both protective and aesthetic functions.
Headline
Knowledge
Safety and Use of Woodworking Machinery
Woodworking machine, as the name suggests, is the mechanical equipment used in wood processing. It is a variety of cutting and processing equipment used in the process of sawing logs and processing them into wood products, and furniture machinery is an important part of woodworking machinery. Woodworking machines are the same as machine tools, and can be divided into milling machines, lathes, planers, drilling, rotary cutting, sanding, etc. according to different processing methods. However, do you understand the safety and use of woodworking machinery? Check out the following.
Headline
Knowledge
What is the Importance of Lithography Technology and Mask Aligner in Chip Manufacturing?
Lithography is the most important processing technology of integrated circuits and the most critical technology for manufacturing chips. In the entire chip manufacturing process, the implementation of almost every process is inseparable from the technology of lithography.
Headline
Knowledge
What is A Switching Power Supply? Through Principal Analysis, Understand the Basics In 3 Minutes!
Many people do not know about switching power supply and have always thought that is similar to a linear power supply. Actually, there is difference. The following will explain the principles of basic regarding switching power supplies. Learn with us now!
Agree