PMEDM is a kind of EDM Process where powder particles are mixed in the dielectric fluid for improving various machining parameters.

1. SEMINAR
PRESENTED BY
SOUMAVABORAL
Undertheguidanceof
Prof.(Dr.)B.Bhattacharyya
ROLLNO.:-001411702015
REGISTRATIONNO.:-129418OF2014-2015
ProductionEngineeringDepartment
JadavpurUniversity,Kolkata

2.  Joseph Priestley, in 1770 first
discovered, erosive effect of electric
discharge on various metals.
 In 1943 Dr. B.R. Lazarenko and Dr.
N.I. Lazarenko learned to control the
erosive effects in EDM.
 EDM is a Non-conventional
Machining Process where no physical
cutting forces between tool and work-
piece are present.
 Material removal takes place by
means of electric spark of 8000°C -
12000°C.
Joseph Priestley
(1733-1804)

3.  Tool is made cathode
and workpiece is
anode.
 Metal from workpiece
are removed through
spark erosion.
 Plasma channel created
due to high voltage
between tool and
workpiece.
Working Principle of EDM

4.  Its a dielectric material in the liquid state.
 They are used as electrical insulators in high voltage
applications.
 Dielectric fluid should provide a oxygen free machining
environment to the workpiece.
 It breaks down and ionized when collided with electrons.
 It helps in initiating discharge, and conveys the spark.
 It helps in cooling the electrode, workpiece and system.
 It carries away the eroded particles with it.
 It may be mineral oils, kerosene, transformer oil, EDM oils
or synthetic oils.

5.  Poor Overcut size, causes
easy removal of wear
debris particles and better
machining efficiency.
Low Material Removal
Rate of conventional EDM.
Low Surface Finish in
Conventional EDM.
Higher machining time.
Higher Tool Wear Rate.

6.  The use of semi conductive solid particles in EDM Dielectric
named as PMEDM.
 It is a recent innovation of EDM for enhancing its
capabilities.
 To enhance the machined surface properties by means of fine
powders of Silicon, Graphite, Aluminum are mixed with
dielectric solution.
 Reduces Surface Roughness(SR), Tool Wear Rate(TWR).
 Increases overcut size and Material Removal Rate (MRR).
 Any material that is electrically conductive can be machined
regardless of its hardness, toughness, strength and
microstructure.

7.  Fine powder is mixed with
dielectric solution by means of
stirrer and a circulation pump is
installed for reuse of powder.
Gap distance between tool and
work-piece is kept at 25µm to
50µm.
Gap voltage- 80 to 320 V.
Electric field crated due to gap
voltage- 10˄5 to10 ˄7 V/m.
 Powder particles between tool and work-piece get energized and behave in a zig-
zag fashion. Also they arrange themselves in chain form.
These Chains help in ‘Bridging Effect’.
Due to ‘Bridging Effect’ gap voltage and insulating strength of the dielectric
fluid decreases.
This causes short-circuit and early explosion in the gap.
Principle of PMEDM Process

8. Due to this series
discharge and faster
sparking in the inter-
electrode gap , MRR
becomes higher.
Added powder makes
the plasma channel
wider and enlarged.
Electric density decreases and sparking is uniformly distributed
among the powder particles.
Due to the uniform discharges, uniform erosion takes place and
improves the Surface Finish.
PMEDM Experimental Setup

9.  Material Removal Rate (MRR) is greatly influenced
by current, pulse-on time and electrode materials. Type of
powder and its concentration have lower contribution to the
MRR improvement.
 Tool Wear Rate(TWR) is basically influenced by powder
concentration, whereas pulse-on time, current, electrode
material and type of powder have less contribution.
 Overcut size improvement is influenced by pulse-on time
and powder concentration.
 Powder concentration and supplied current has significant
effect to improve Surface Roughness (SR).

10.  Advantages :-
1. Any electrically conductive material can be machined.
2. Stress free complicated geometries can be produced.
3. Eliminates the necessity of grinding and fine surface finish.
 Limitations :-
1. MRR is low making the process economical only for very
hard and difficult to machine materials.
2. Work-piece material must be electrically conductive.
3. Process can not be monitored during machining. Thus high
skilled persons are able to operate.

11.  In high precision instruments where large area with fine
surface finish are required to be machined.
 Making and machining of micro-products and sophisticated
micro mechanical element such as in micro-pumps, micro-
robot, micro-engines etc.
 It can be used where rough machining is required.
Conclusions :-
 Researches are going on to optimize the input parameters to
get the desired output. Process optimization can integrate
Genetic Algorithm, Taguchi Methodology, Response Surface
Methodology, Grey Relational Analysis.
 Researches are also going on to combine PMEDM with
ultrasonic or abrasive, powder mixed near dry EDM, and
Powder mixed ECDM process.