Download CHAPTER 5 – ELECTRICAL METHODS OF MATERIAL REMOVAL

CHAPTER 5 – ELECTRICAL METHODS OF MATERIAL
REMOVAL
Electrical Discharge Machining (EDM) - The process of removing metal
with an electric arc.
a) The workpiece and cathode (shape of tool/ impression) are submerged
in a dielectric fluid
b) Voltage is applied (DC 300V)
c) Material is arced away and flushed out by the dielectric fluid
d) Electrodes are usually made of graphite
EDM is best suited for parts that to be made of very hard (conducting)
materials and to a high precision (or low surface roughness), at a low
production rate, and having some strange shapes which would be difficult to
machine by conventional techniques
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 (passed through a previously formed hole or started
from the edge of the material) to erode the sides of the hole to form two
external surfaces, which can have an elaborate shape. (electrode is a brass,
copper, tungsten or molywire).
Skimming – A final light pass for polishing or to meet dimensional
tolerances.
Electric Discharge Grinding (EDG) is a gentle process excellent for thin
materials.
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.