2. BITS Pilani, Hyderabad Campus
1.CNC Wire cut EDM
OBJECTIVE:
Study and Prepare a program by ELCAM software and cut the profile by using
CNC Wire cut EDM.
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Electrical energy is directly used to cut the material to get the final shape and size
– Electrical discharge machining (EDM)
– Wire cut Electrical Discharge Machining (WCEDM)
Introduction to EDM
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Principle
Metal is removed by producing powerful electric
spark discharge between the tool (cathode) and the
work material (anode)
Also known as Spark erosion machining or electro
erosion machining
Machining action forms a gap between the part and
electrode (tool) which causes a spark which removes
the material from work piece
Electrode is (-) negative and part is (+) positive
Electrode can be made form brass, copper, graphite
Working Principle
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EDM has the following advantages:
1. Cavities with thin walls and fine features
can be produced.
2. Difficult geometry is possible.
3. The use of EDM is not affected by the
hardness of the work material.
4. The process is burr-free.
Electrical Discharge Machining (EDM)
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Wire Cut Electrical Discharge Machining
(WC-EDM)
Wire cut EDM machining (Electrical Discharge Machining) is an electro thermal production process.
In WEDM, A thin wire of brass, tungsten or copper is used as an electrode
Deionized water is used as the dielectric
Greater flexibility due to independent movement of upper guide helps in programming the wire-cut EDM, for
cutting very intricate and delicate shapes.
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Working Principle
The working principle is based on thermoelectric energy. This energy is created between work piece and tool.
Major Components
1. Process is controlled by CNC.
2. Power supply . Provide energy to the spark.
3. Mechanical section . worktable,workstand,wire drive mechanism.
4. Dielectric system. The water reservoir where filtration , condition
of water(resistivity/conductivity)and temperature of water is
provided and maintained.
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Important characteristics
Tool material : brass, tungsten or copper
Work piece material :conducting material and alloys.
Process parameters : voltage, spark gap and melting
temperature of work.
Material removal : Melting and vaporization
Wire diameter : 0.25mm
Die electric flushing pressure : ( 10 -15 kgf/𝑐𝑚2 )
Spark gap :0.005-0.05mm
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Dielectric Fluid
Fluid medium which doesn’t conduct electricity
Dielectric fluids generally used are paraffin, white
spirit, kerosene, mineral oil
Must freely circulate between the work piece and
tool which are submerged in it
Eroded particles must be flushed out easily
Should be available @ reasonableprice
Dielectric fluid must be filtered before reuse so that chip
contamination of fluid will not affect machining
accuracy
Wire Cut Electrical Discharge Machining
(WC-EDM)
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In this process, a thin metallic wire is fed on-to the work piece, which is submerged in a tank of
dielectric fluid such as deionized water.
The wire, which is constantly fed from a spool, is held between upper and lower guides. The
guides are usually CNC-controlled.
In the wire-cut EDM process, water is commonly used as the dielectric fluid. Filters and de-
ionizing units are used for controlling the resistivity and other electrical properties.
Wires made of brass are generally preferred.
The area where in discharge takes place gets heated to very high temperatures such that the
surface gets melted and removed. The cut particles (debris) get flushed away by the
continuously flowing dielectric fluid and keep the wire and work piece cool.
The wire and work piece must be electrically conductive.
As much as 50 hours of machining can be performed with one reel of wire, which is then
discarded.
Pieces over 16 in thick can be machined.
(WC-EDM) Process
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Advantages and disadvantages of (WC-EDM)
Advantages
Machining accuracy is higher.
During machining, electrode wire doesn’t touch work piece, there is no physical cutting force.
There is very little heat impact on the surface of work piece
It can machine small shape holes, small gap or job with complicated shape.
The process can be employed for extremely hardened work piece materials.
Disadvantages
o Consumes high levels of energy
o Only able to machine conductive materials.
o More expensive process than conventional milling or turning.
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Aerospace, Medical, Electronics and Semiconductor applications
Tool & Die making industries.
In making Gauges & Cams
Cutting of Gears
Manufacturing hard Electrodes.
Applications of (WC-EDM)
