ELECTRIC DISCHARGE MANUFACTURING

• MOIZ FAROOQUI• ME 3rd YEAR• ITM GIDA, GORAKHPUR

Electric Discharge Machining

Moiz Farooqui ME-3rd year

Introduction

• EDM is unconventional Machining technique of Material Erosion or Material Removal using Electric Discharge Spark.

• It is also called spark machining, spark eroding, burning, die sinking, wire burning or wire erosion, is a manufacturing process whereby a desired shape is obtained using electrical discharges (sparks).Material is removed from the workpiece by a series of rapidly recurring current discharges between two electrodes , separated by a dielectric liquid and subject to an electric voltage.

History

• The erosive effect of electrical discharges was first noted in 1770 by English physicist Joseph Priestly .

• B. R. Lazarenko and N. I. Lazarenko, were tasked in 1943 to investigate ways of preventing the erosion of tungsten electrical contacts due to sparking

Types OF EDM

• Wire EDM:- It Is used for Shape Cut out of a flat Sheet or Plate Of Metal.

• Sinker EDM:- They Are generally Used for Very Small pieces where conventional Milling not practical .

CONSTRUCTION

Principle

Physical quantities Vs MMR

Terminology

• MRR( Metal Removal Rate)• Two broad categories of generators, also

known as power supplies, are in use on EDM machines commercially available: the group based on RC circuits and the group based on transistor controlled pulses.

Material Suitable

• Cast Iron• Carbon Steel• Alloy Steel• Stainless steel• Aluminium an alloys• Zinc an alloys• Magnesium and alloys• Thermoplastic,Ceramic,Photo Polymer and Wood

Why EDM ?

• Reduces Fixture and Tooling Cost• Capable of machining Exotic Material• High accuracy and Surface Finish• Complex and Intricate Shapes• Can Machine Hardened Material • Eliminate need for Heat treatment after

Machining

Why not EDM ?

• High Specific energy Consumption• Depends on dielectric fluid• Not applicable to non conducting Material• The slow rate of material removal.• The additional time and cost used for creating

electrodes for ram/sinker EDM.• Reproducing sharp corners on the workpiece

is difficult due to electrode wear.

Application

• Compatible like planar, prismatic Shape• Blind complex cavities• Microholes for Nozzle• Turbine blades, deep holes and narrow slots

Conclusion

• EDM is fast material removal technique though expensive

• But it has various advantage over other unconventional metal removal technique like ECM etc

Reference

• Manufacturing Sciences II by K.M. Moeed

• http://en.wikipedia.org/wiki/Electrical_discharge_machining