Download Chapter 5 Electrical Methods of Material Removal

Electrical Methods of
Material Removal
Chapter 5
Competencies

Identify the general operating principles
of EDM
Electrical Methods
of Material Removal
Electrical Discharge Machining (EDM) - The process of
removing metal with an electric arc.
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The workpiece and cathode (shape of tool/ impression)
are submerged in a dielectric fluid
Voltage is applied (DC 300V)
Material is arced away and flushed out by the dielectric
fluid
Electrodes are usually made of graphite
The material removal rate is influenced by the melting
temperature of the workpiece material and is faster for
materials of lower melting temperature.
Electrical Methods
of Material Removal

EDM is best suited for materials whose parts
are:
• Made of very hard (conducting) materials and
• To have a high precision (or low surface
roughness)
• At a low production rate
• To have some strange shapes which would be
difficult to machine by conventional
techniques
Electrical Methods
of Material Removal

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RAM EDM= Plunge EDM = Die Sinking EDM - complex
cavities are formed by penetration of shaped electrode
into the part.
• Used to make dies for forging or punching operations.
Wire EDM- Uses a wire to erode the sides of the hole
to form two external surfaces, which can have an
elaborate shape.
• wire electrode is of brass, copper, tungsten or
molybdenum
Electrical Methods
of Material Removal
Advantages over faster methods of material removal:
• Unaffected by the hardness of the workpiece.
• Holes with extremely complex shapes can be made.
• There is no distortion of the metal, and no burrs left.
• Produces surfaces to very fine dimensional and
roughness tolerances
• EDM operates unattended.
Disadvantages:
• EDM is slow, expensive, and cannot be used on
nonconductive materials.