Electrical Discharge Machining

Introduction-

Want to know about the Electrical discharge machining?

Then you landed in the right place. Here you will get complete details about the electro-discharge machining process, from scratch to end.

So, I invite you to come along the board and stay with me while I take you on the journey of knowledge, here in Engineers Rail.

So, Shall we start?

Wait, Before I start, Here I have a bonus for you, you can get PDF to download, of this whole article at the end.

So, let’s Start…

What is Electrical Discharge Machining?

Electric discharge machining is a non-conventional machining process that uses an electric spark to remove metal from the workpiece.

This process is done by applying high-frequency current through electrodes and Workpiece emerging in the dielectric fluid.

It is also known as Spark erosion, Electro-erosion or spark machining.

Electrical discharge machining(EDM) is used to machine very hard materials.

Working Principle of electrical discharge machining-

Here is the working principle of EDM machining-

  • EDM works on the principle of Heat energy generated by a spark is used to remove the material from the workpiece.
  • The tool and workpiece are separated by a small gap called a spark gap. The gap is varied from 0.01mm to 0.5mm.
  • When supply is ON, thousands of sparks are produced per second.
  • When the spark comes in the contact with the dielectric fluid in the spark gap, the fluid gets ionized. It allows current to flow between the tool and workpiece.

Types of Electrical discharge machining-

  • Die sinking EDM process
  • Wire cut EDM process
  • Hole drilling EDM process

Die Sinking EDM process-

When two metals parts are placed in the dielectric fluid and connected to the source power supply, erosion of material takes place due to spark energy generated by electric tension between two metals parts, ie, anode and cathode. It is also known as the sinker EDM process.

In this case, the metal removal is affected by non-stationary electrical discharges which are separated from each other both spatially and temporarily.

die-shinking-edm-process

Wire Cut EDM Process-

The fundamental principle of metal removal in wire cut EDM is the same as EDM. It is also known as WEDM.

It employs electrical energy to remove metal from the workpiece without touching it.

The maximum depth of the workpiece is to be 90mm, wire dia is to be 0.3mm and speed should be 2.5 to 150mm/sec.

Here in WEDM wire acts as a tool and EDM wire is made of copper or a mixture of copper graphite.

wire-cut-edm-process

Hole Drilling EDM Process-

Here in hole drill EDM, High-pressure dielectric fluid enters through the rotating electrode to produce fast and accurate drills.

hole drill EDM is just similar to die sink EDM, But there is a number of differences.

Hole drilling EDM is used to drill holes where difficult to machine materials is to drill.

To drill, different types of electrodes are used in different materials, from small as 0.3mm diameter to 6mm diameter.

Hole-drilling-edm

After knowing the types of EDM, Now let’s move to the various parts and construction of the EDM machines.

Parts of Electric discharge machining-

Here are the principal components of the EDM process-

  • DC pulse generator
  • workpiece and tool
  • Servo control unit
  • Pinion
  • Dielectric Medium
  • Dielectric fluid

DC pulse generator-

This converts the AC power supply into a high pulse DC supply, responsible for generating spark between the tool in the workpiece.

The negative terminal sets to the tool and the positive terminal is supplied to the workpiece.

Workpiece and tool-

Here workpiece acts as Anode and the tool acts as a cathode.

Servo control unit-

A servo control unit controls the spark gap between the tool and workpiece.

Pinion-

The pinion is used to controlling the motion of the tool directed by the servo control unit

Dielectric Medium-

Dielectric medium is consist of dielectric fluid, fixture, and workpiece itself.

Dielectric fluid-

It works to maintain the gap between workpiece and tool, acting as a non-conductor. Mostly, Deionized water, silicon oil, glycol, kerosene oil is used as dielectric in ed machining.

Here is the explanation of the EDM process with a neat sketch-

Fig. electric discharge machining diagram-

 electric-discharge-machining

How does it work?

Here is a working explanation of electric discharge machining, step by step-

  • As the pulse of DC electricity reaches the electrode and applies an intense electrical field develops in the gap.
  • Microscopic contaminants suspended in the dielectric fluid are attracted by the field contrasted in the field’s strongest point.
  • These contaminants build a high conductive bridge across the gap.
  • As the field’s voltage increases, the material of the conductive bridge heats up.
  • Some pieces are ionized to form a spark channel between the electrode and the workpiece.
  • At this point, Both the temperature and pressure in the channel rapidly increase, generating a spark.
  • A small amount of material is melt and vaporized from the electrode and the workpiece at the point of spark contact.
  • Hence, metal removal in electric discharge machining takes place through Spark erosion.

Here is the video guide to help you to see the actual working of EDM-

Are you there?

If so, then I am heading you to the Advantages, disadvantages, and applications of this electrical machining.

So, Let’s go…

Advantages-

Here are some advantages of EDM-

  • Fast Process
  • Every conductive material can be machined by EDM.
  • Ii is independent of the hardness of the workpiece, hence hardened workpiece can be machined easily
  • Complex die sections and complex shapes can be produced accurately.
  • EDM process is a burr-free process.
  • The thin section can be easily machined without deforming the part.
  • Fragile parts can also be machined.

Disadvantages-

Here are some disadvantages of EDM-

  • Slow MRR
  • Additional time and cost for creating electrodes for ram/sinker EDM.
  • In this machining process, high tool wear occurs.
  • High electricity consumption
  • Square corners can not be formed.
  • Tool wears limits the accuracy and surface finish of the material sometimes.
  • Only a good conductor of electricity can be machined in electrical discharge machining.
  • Edm is not suitable for machining non-conducting materials.

Applications-

  • Prototype production
  • Metal disintegration machining
  • Coinage die making
  • Textured surface finish
  • Used to make small holes in nozzles.
  • It is used to machine hard and brittle materials
  • It is used to sharpening the tools and cutters.

After going through various topics above, let’s talk about the history and further recent revolution of the EDM machine process.

History-

In 1970, the English scientist, Priestley, first detected the erosive effect of electrical discharges on metals. More recently, during research, the soviet scientists, Lazarenko and Lazarenko, decided to exploit the destructive effect of an electrical discharge and develop a controlled method of metal machining.

In 1943, they announced the construction of the first Spark erosion machine.

The Spark generator used in 1943, known as the Lazarenko circuit, has been employed over many years in power supplies for EDM machines and an improved form is being used in many current applications.

Recent Revolutions-

Spark machining has been in production use for approximately seventeen years and is a well-established process for producing holes and cavities in tough materials with high precision.

There are, however, quite a number of problems still to be solved to enable the process to be adopted on an extensive basis.

The problems are-

Problems
Ignition of spark discharge in a contaminated flushed dielectric
Mechanism of metal erosion by spark discharge
Distribution of discharge energy on anode and cathode during a pulse and its relation to the discharge
Distribution of temperature and pressure in the discharge gap for different operating times

There are many instances of spark erosion being applied as a production process in addition to its more usual capacity as a jobbing process.

Its use as a production process is largely the result of multiple tooling techniques which allow several components to be eroded simultaneously.

A prominent factor of multiple tooling is the development of multi-channel techniques. 

Work has been conducted with as many as 77 channels and it is a high probability that there will be a considerable increase in the number of channels used.

Numerical control has been tried in the case of a few machines but the technique is still in its infancy.

Conclusion-

Electric discharge machining(EDM) is the removal of materials conducting electricity by an electrical discharge between two electrodes(Workpiece and tool), a dielectric fluid being used in the process.

The aim of this process is controlled removal of material from the workpiece, As I have discussed in several topics above.

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Bookmark Engineers Rail for further Awesome readings. Thank you for being with me, see you in the next session.

 

Here are some more topics related to the machining process, You should Read also-

Electrochemical Machining

Water Jet Machining

Abrasive Jet Machining

Ultrasonic Machining

Difference Between Conventional and Non-Conventional Machining Processes

 

Here is your surprise gift… You can download this whole article electric discharge machining PDF here-
 
electric discharge machining pdf
 
 
 

Before you go, Here are some Q&A sections, You should hang on there for sometimes-

FAQs

What is electrical discharge machining used for?

When EDM can be used-
(i) Where deep cutting is required
(ii) In unattended cutting
(iii) For hard materials
(iv) For sharp inside corners
(v) For the most complex geometry

Who invented electrical discharge machining?

In 1943, the soviet scientists, Lazarenko and Lazarenko, firstly introduced electrical discharge machining.

Is distilled water a dielectric fluid?

Yes! Distilled water is an ideal dielectric fluid.

 

References-

Wikipedia

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