Today we will learn about electrical discharge machining
principle, working, equipment’s, advantages and disadvantages with diagram. This machining process uses electric spark to remove metal form work piece. This machining is same
as removal of metal burr in presence of electric spark. An electric spark used
as the cutting tool to cut the work piece and produce desire shape. This process
is done by applying high frequency current through the electrode to work piece.
The spark produce removes metal in form of very small chips. This process is done in a dielectric fluid.
Electrical discharge Machining:
Principle:
Electrical discharge machining process works on the basic
principle of spark generation and metal removed by spark erosion. EDM spark erosion is same as electric spark
which burn a small hole in a piece of metal through witch it contacts. The spark generated by
this process produces heat, which remove metal by erosion and evaporation. In
this machining process both the work piece and tool must be made by conductive
material.
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| Diagram of Electrical Discharge Machining |
Equipment’s:
Power Supply:
In a EDM process a high frequency current used to generate
spark between electrode and work piece. This spark generates heat and remove
metal form work piece.
Dielectric fluid supply and flushing system:
The dielectric fluid acts as a vehicle to drive away the
chips and thus preventing them from sticking to the surface. This fluid acts as
flushing system for chips. It also helps in increasing the metal removal rate
by promoting spark between tool and work. This fluid also works as coolant
medium.
Tool and tool holding devices:
In EDM process, tool also erodes due to spark hence the selection of
tool depends on wear ratio, ease to tool fabrication and cost of material. The most commonly used electrode material are Cu, Tungsten
alloy, Cast Iron, Steel, Silver tungsten alloy, graphite.
Work piece and work holding devices:
In this process only
good conductors of electricity can be machined. So the work piece should have good electric conductivity. This process does not depend on hardness of work piece so there is no criteria of hardness.
Working:
In this process, work piece should be well electric
conductive. Only electric conductive material can be machined by this method.
The working of EDM is as follow.
- First both work piece and tool are submerged into dielectric fluid. The dielectric fluid help to control the arc discharge. This also removes suspended particles of work piece material and tool from the work cavity.
- A servomechanism is used which maintains a very small gap between the work piece and the tool. This gap is desirable for proper arc formation. It is about the thickness of human hair.
- The tool is made as the opposite shape of work piece.
- A high frequency current supplied to electrode, which produces a spark between the tool and work piece. This spark generates high in work cavity.
- The metal removed from the work piece due to erosion and evaporate ion.
- The chips or suspended particle between tool and work piece should be removed to prevent them to form bridge that causes short circuit. This is done by continuous supply of dielectric fluid.
- The EDM produce a cavity slightly larger than the electrode because of overcut.
For better understanding of EDM working process, watch the following video.
Advantages and Disadvantages:
Advantages:
- Every conductive material can be cut by this process.
- It is independent on hardness of workpiece so hardened work piece can be machined easily.
- Complex die section and complex shapes can be produce accurately.
- This process is burr free.
- Thin section can be easily machined without deforming the part.
Disadvantages:
- In this machining process high tool wear occurs.
- Tool wears limits accuracy and surface finish of metal.
- Only good conductors of electricity can be machined by EDM.
This is all about electrical discharge machining, principle,
working, equipment’s, advantages and disadvantages with its diagram. If you have any query
regarding this article, ask by commenting. If you like this article, don’t
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