Module
9
Non conventional
Machining
Version 2 ME, IIT Kharagpur

Lesson
39
Electro Discharge
Machining
Version 2 ME, IIT Kharagpur

Instructional Objectives
(i)
(ii)
(iii)
(iv)
(v)
(vi)
(vii)
(viii)
(ix)
(x)
(xi)
(xii)
(xiii)
(xiv)
(xv)
(xvi)
(xvii)
(xviii)
(xix)

Identify electro-discharge machining (EDM) as a particular type of non-tradition processes
Describe the basic working principle of EDM process
Draw schematically the basics of EDM
Describe spark initiation in EDM
Describe material removal mechanism in EDM
Draw the basic electrical waveform used in EDM
Identify the process parameters in EDM
Describe the characteristics of EDM
Identify the purpose of dielectric fluid in EDM
List two common dielectric fluid
Analyse the required properties of EDM tool
List four common tool material for EDM
Develop models for material removal rate in EDM
Identify the machining characteristics in EDM
Analyse the effect of process variables on surface roughness
Analyse taper cut and over cut in EDM
Identify different modules of EDM system
Draw schematic representation of different electrical generators used in EDM
Analyse working principle of RC type EDM generator

1. Introduction
Electro Discharge Machining (EDM) is an electro-thermal non-traditional machining process, where electrical energy is used to generate electrical spark and material removal mainly occurs due to thermal energy of the spark.
EDM is mainly used to machine difficult-to-machine materials and high strength temperature resistant alloys. EDM can be used to machine difficult geometries in small batches or even on job-shop basis. Work material to be machined by EDM has to be electrically conductive.

2. Process
Fig. 1 shows schematically the basic working principle of EDM process.

V
(-ve)

I

Fig. 1

Schematic representation of the basic