SlideShare a Scribd company logo
Seminar
ELECTRICAL DISCHARGE
MACHINING (EDM): A REVIEW
Introduction
 Electrical discharge machining (EDM) is an electro-thermal process.
 It is one of the most extensively used material removal processes.
 Its unique feature is to use thermal energy to machine electrically conductive
parts regardless of hardness.
 With no direct contact between the tool and workpiece, EDM supports smooth
machining.
 The main principle of EDM is to erode a material through the effect of electric
discharge (spark).
EDM
Ref: https://www.makino.com
History
 The origin of EDM dates back to 1770 when English scientist Joseph Priestly
discovered the erosive effect of electrical discharges.
 Several attempts were made to achieve a controlled EDM process.
 But, These processes were not very precise due to overheating of the
machining area.
 Pioneering work on EDM was carried out in 1943 by two Russian scientists, B.R.
and N.I. Lazarenko at the Moscow University.
 They developed a controlled process for machining materials by vaporizing
and melting its surface.
History (Cont…)
 The RC (resistance–capacitance) relaxation
circuit was introduced in 1950s.
 Later, it served as the model for successive
developments in EDM technology.
 It provided the first consistent dependable
control of pulse times.
RC circuit
Ref: https://www.sciencedirect.com
Main Components in EDM
 Workpiece and tool
 Electrical power supply
 Dielectric
 Servo control unit
 Fixture
Ref: https://www.researchgate.net
Schematic of EDM process
Working Principle
 A potential difference is applied between the tool and workpiece.
 Depending upon the applied potential difference and the gap between the tool and
workpiece, an electric field would be established.
 As the electric field is established between the tool and the job, the
free electrons on the tool are subjected to electrostatic forces.
 If the bonding energy of the electrons is less, electrons would be emitted from the tool (cold
emission).
 They start moving towards the job and there would be collisions between the electrons and
dielectric molecules (ionization).
Ref: https://www.rajagiritech.ac.in
Working Principle (Cont…)
 This cyclic process would increase the concentration of electrons
and ions in the dielectric medium between the tool and the job at
the spark gap.
 Concentration would be so high that the matter existing in that
channel could be characterized as “plasma”.
 Electrical resistance of such plasma channel would be very less.
 Thus all of a sudden, a large number of electrons will flow from the
tool to the job and ions from the job to the tool.
 This is called avalanche motion of electrons.
 High speed electrons then impinge on the job and ions on the tool.
Plasma channel
Ref: https://link.springer.com
Working Principle (Cont…)
 Kinetic energy of the electrons and ions on impact with the surface
of the job and tool respectively would be converted into thermal
energy or heat flux.
 Localized extreme rise in temperature leads to material removal.
 Material removal occurs due to instant vaporization of the material
as well as due to melting.
 As the potential difference is withdrawn, the plasma channel is no
longer sustained.
 As the plasma channel collapse, it generates pressure or shock
waves, which evacuates the molten material forming a crater of
removed material around the site of the spark.
Spark initiation
Ref: https://www.sciencedirect.com
EDM Process Parameters
Discharge Voltage
 Discharge voltage in EDM is related to the spark gap and break down strength of
the dielectric.
 Before current can flow, the open gap voltage increases until it has created an
ionization path through the dielectric.
 Once the current starts to flow voltage drops and stabilizes at the working gap
level.
 The preset voltage determines the width of the spark gap between the leading
edge of the electrode and workpiece.
Ref: https://www.slideshare.net
EDM Process Parameters
 It is most important machining parameter in EDM.
 Higher current is directly related to the surface area of the cut.
 It is used in roughing operations and cavities.
 Higher current improves MRR, but it leads to poor surface finish and tool wear.
 New improved electrode materials, especially graphite, can work on high currents
without much damage.
Peak Current
Ref: https://www.sciencedirect.com
EDM Process Parameters
Pulse Duration and Pulse Interval
 Pulse on-time is commonly referred to as pulse duration
and pulse off-time is called pulse interval.
 With longer pulse duration, more workpiece material will be
melted away.
 Metal removal is directly proportional to the amount of
energy applied during the on-time.
 Pulse interval will affect the speed and stability of the cut.
 In theory, the shorter the interval, the faster will be the
machining operation.
 But if the interval is too short, the ejected workpiece
material will not be swept away by the flow of the dielectric
and the fluid will not be deionized.
 This will cause the next spark to be unstable.
Ref: https://www.sciencedirect.com
EDM Process Parameters
Polarity
 The polarity of the electrode can be either positive or negative.
 The plasma channel is composed of ion and electron flows.
 As the electron processes (mass smaller than anions) show quicker
reaction, the anode material is worn out predominantly.
Ref: https://www.researchgate.net
EDM Process Parameters
Electrode Gap
 The tool servo-mechanism is of considerable importance in the efficient
working of EDM.
 Its function is to control responsively the working gap to the set value.
 The gap stability and the reaction speed of the system is important for
good performance.
 Gap width is not measurable directly, but can be inferred from the average
gap voltage.
Ref: https://www.edm.kd-solution.com
Properties of Tool Materials
A tool material need to have these properties:
 High electrical conductivity
 High thermal conductivity
 Higher density
 High melting point
 Easy manufacturability
 Graphite is the most commonly used material.
 Other materials are brass, tellurium copper, electrolytic oxygen free
copper etc.
EDM Surface Layers
 There is a top white layer which crystallizes from the liquid cooled at high speed.
 The depth of this top melted zone depends on the pulse energy and duration.
 Below the top layer there is a chemically affected layer with changes in the average
chemical composition and phase changes.
 There after, a plastically deformed zone is observed with strains.
Surface layers after electrical discharge machining
Ref: https://www.sciencedirect.com
Surface Modifications
 When mild steel is eroded in liquid medium paraffin using copper electrode, the
workpiece is coated with a very hard layer.
 Using Titanium powder compact electrodes with carbon steel results increase in
hardness of steel.
 Powder-mixed dielectric is used to facilitate ignition process and get good surface
finish.
 Some powder that is usually used in doping are Ni, Co, Ti, Cr etc.
 Abrasive powders such as silicon carbide and alumina are mixed in the dielectric
to improve the material removal rate.
Product Quality Issues
 surface roughness in EDM would increase with increase in spark energy.
 Surface finish can be improved by decreasing working voltage, working current
and pulse on time.
 Taper cut can be prevented by suitable insulation of the tool.
 Overcut cannot be prevented as it is inherent to the EDM process.
 But the tool design can be done in such a way so that same gets compensated.
Ref: https://www.sciencedirect.com
Conclusions
 EDM is a viable machining option of producing highly complex parts.
 Extremely hard materials can also be machined to very close clearances by this.
 Very small workpieces can be machined where conventional tools may damage
the part from excess cutting tool pressure.
 There is no direct contact between tool and work piece.
 Therefore, delicate sections and weak materials can be machined without
perceivable distortion.
Conclusions (Cont…)
 Material removal in EDM mainly occurs due to formation of shock waves
as the plasma channel collapse.
 Material removal depends mainly on thermal properties of the work
material rather than its strength, hardness etc.
 Hybrid processes enhance stability by influencing the flushing.
 Material transfer from electrode bodies and material transfer from
powders suspended dielectric is under research.
 References:
https://www.sciencedirect.com/science/article/pii/S092401360800705X
https://www.slideshare.net/GopinathGuru3/electrical-discharge-machining-70522354
https://www.rajagiritech.ac.in
https://www.sciencedirect.com/science/article/pii/S0890695503001627
https://www.irjet.net/archives/V4/i5/IRJET-V4I521.pdf
https://www.ijser.org/researchpaper/Current-Research-trends-in-Electric-Discharge-Machining-EDM-Review
https://www.sciencedirect.com/topics/engineering/discharge-energy
https://www.edm.kd-solution.com/en_edm08.html
https://nptel.ac.in/courses/112105127
EDM.pptx

More Related Content

Similar to EDM.pptx

Current Advanced Research Development of Electric Discharge Machining (EDM): ...
Current Advanced Research Development of Electric Discharge Machining (EDM): ...Current Advanced Research Development of Electric Discharge Machining (EDM): ...
Current Advanced Research Development of Electric Discharge Machining (EDM): ...
sushil Choudhary
 
Seminar report on electric discharge machine
Seminar report on electric discharge machineSeminar report on electric discharge machine
Seminar report on electric discharge machine
Ankit Amlan
 
Electric Discharge Machining (Modern Machining Process)
Electric Discharge Machining (Modern Machining Process)Electric Discharge Machining (Modern Machining Process)
Electric Discharge Machining (Modern Machining Process)
Dinesh Panchal
 
ELECTRO_DISCHARGE_MACHINING_EDM.pptx
ELECTRO_DISCHARGE_MACHINING_EDM.pptxELECTRO_DISCHARGE_MACHINING_EDM.pptx
ELECTRO_DISCHARGE_MACHINING_EDM.pptx
JiaJunWang17
 
Electrical Discharge Machining Process
Electrical Discharge Machining ProcessElectrical Discharge Machining Process
Edm
EdmEdm
edm
edmedm
F0324024035
F0324024035F0324024035
F0324024035
theijes
 
Electrical discharge machining
Electrical discharge machiningElectrical discharge machining
Electrical discharge machining
YOGESHHV
 
Electrical discharge machining
Electrical discharge machiningElectrical discharge machining
Electrical discharge machining
MountaionRaj
 
Electrical discharge machining
Electrical discharge machining Electrical discharge machining
Electrical discharge machining
Gopinath Guru
 
Wirecut edm
Wirecut edm Wirecut edm
Wirecut edm
ParthaTripathy2
 
Electrical discharge machining
Electrical discharge machiningElectrical discharge machining
Electrical discharge machining
Asha A
 
PMEDM
PMEDMPMEDM
Electrical Discharge Machining Process
Electrical Discharge Machining ProcessElectrical Discharge Machining Process
Electrical Discharge Machining Process
Vishal Kumar Jaiswal
 
Full details of Electroc discharge machine ,Ultrasonic machining, Electro Che...
Full details of Electroc discharge machine ,Ultrasonic machining, Electro Che...Full details of Electroc discharge machine ,Ultrasonic machining, Electro Che...
Full details of Electroc discharge machine ,Ultrasonic machining, Electro Che...
ManojSingh376471
 
Comparative study on variation of process characteristics on al and die steel...
Comparative study on variation of process characteristics on al and die steel...Comparative study on variation of process characteristics on al and die steel...
Comparative study on variation of process characteristics on al and die steel...
IAEME Publication
 
Electrical discharge machining
Electrical discharge machiningElectrical discharge machining
Electrical discharge machining
Nitin Vadhel
 
Spot welding /certified fixed orthodontic courses by Indian dental academy
Spot welding /certified fixed orthodontic courses by Indian dental academy Spot welding /certified fixed orthodontic courses by Indian dental academy
Spot welding /certified fixed orthodontic courses by Indian dental academy
Indian dental academy
 
Spot welding /certified fixed orthodontic courses by Indian dental academy
Spot welding /certified fixed orthodontic courses by Indian dental academy Spot welding /certified fixed orthodontic courses by Indian dental academy
Spot welding /certified fixed orthodontic courses by Indian dental academy
Indian dental academy
 

Similar to EDM.pptx (20)

Current Advanced Research Development of Electric Discharge Machining (EDM): ...
Current Advanced Research Development of Electric Discharge Machining (EDM): ...Current Advanced Research Development of Electric Discharge Machining (EDM): ...
Current Advanced Research Development of Electric Discharge Machining (EDM): ...
 
Seminar report on electric discharge machine
Seminar report on electric discharge machineSeminar report on electric discharge machine
Seminar report on electric discharge machine
 
Electric Discharge Machining (Modern Machining Process)
Electric Discharge Machining (Modern Machining Process)Electric Discharge Machining (Modern Machining Process)
Electric Discharge Machining (Modern Machining Process)
 
ELECTRO_DISCHARGE_MACHINING_EDM.pptx
ELECTRO_DISCHARGE_MACHINING_EDM.pptxELECTRO_DISCHARGE_MACHINING_EDM.pptx
ELECTRO_DISCHARGE_MACHINING_EDM.pptx
 
Electrical Discharge Machining Process
Electrical Discharge Machining ProcessElectrical Discharge Machining Process
Electrical Discharge Machining Process
 
Edm
EdmEdm
Edm
 
edm
edmedm
edm
 
F0324024035
F0324024035F0324024035
F0324024035
 
Electrical discharge machining
Electrical discharge machiningElectrical discharge machining
Electrical discharge machining
 
Electrical discharge machining
Electrical discharge machiningElectrical discharge machining
Electrical discharge machining
 
Electrical discharge machining
Electrical discharge machining Electrical discharge machining
Electrical discharge machining
 
Wirecut edm
Wirecut edm Wirecut edm
Wirecut edm
 
Electrical discharge machining
Electrical discharge machiningElectrical discharge machining
Electrical discharge machining
 
PMEDM
PMEDMPMEDM
PMEDM
 
Electrical Discharge Machining Process
Electrical Discharge Machining ProcessElectrical Discharge Machining Process
Electrical Discharge Machining Process
 
Full details of Electroc discharge machine ,Ultrasonic machining, Electro Che...
Full details of Electroc discharge machine ,Ultrasonic machining, Electro Che...Full details of Electroc discharge machine ,Ultrasonic machining, Electro Che...
Full details of Electroc discharge machine ,Ultrasonic machining, Electro Che...
 
Comparative study on variation of process characteristics on al and die steel...
Comparative study on variation of process characteristics on al and die steel...Comparative study on variation of process characteristics on al and die steel...
Comparative study on variation of process characteristics on al and die steel...
 
Electrical discharge machining
Electrical discharge machiningElectrical discharge machining
Electrical discharge machining
 
Spot welding /certified fixed orthodontic courses by Indian dental academy
Spot welding /certified fixed orthodontic courses by Indian dental academy Spot welding /certified fixed orthodontic courses by Indian dental academy
Spot welding /certified fixed orthodontic courses by Indian dental academy
 
Spot welding /certified fixed orthodontic courses by Indian dental academy
Spot welding /certified fixed orthodontic courses by Indian dental academy Spot welding /certified fixed orthodontic courses by Indian dental academy
Spot welding /certified fixed orthodontic courses by Indian dental academy
 

Recently uploaded

NEC 2023 NATIONAL ELECTRICAL DODE 2023 NEC
NEC 2023 NATIONAL ELECTRICAL DODE 2023 NECNEC 2023 NATIONAL ELECTRICAL DODE 2023 NEC
NEC 2023 NATIONAL ELECTRICAL DODE 2023 NEC
PANIQUEPOMAJAELYOSSE
 
Monitoring and reporting of transparent forest data and information under the...
Monitoring and reporting of transparent forest data and information under the...Monitoring and reporting of transparent forest data and information under the...
Monitoring and reporting of transparent forest data and information under the...
Pilar Valbuena Perez
 
21EC63_Module1B.pptx VLSI design 21ec63 MOS TRANSISTOR THEORY
21EC63_Module1B.pptx VLSI design 21ec63 MOS TRANSISTOR THEORY21EC63_Module1B.pptx VLSI design 21ec63 MOS TRANSISTOR THEORY
21EC63_Module1B.pptx VLSI design 21ec63 MOS TRANSISTOR THEORY
PradeepKumarSK3
 
UNIT I INCEPTION OF INFORMATION DESIGN 20CDE09-ID
UNIT I INCEPTION OF INFORMATION DESIGN 20CDE09-IDUNIT I INCEPTION OF INFORMATION DESIGN 20CDE09-ID
UNIT I INCEPTION OF INFORMATION DESIGN 20CDE09-ID
GOWSIKRAJA PALANISAMY
 
PMSM-Motor-Control : A research about FOC
PMSM-Motor-Control : A research about FOCPMSM-Motor-Control : A research about FOC
PMSM-Motor-Control : A research about FOC
itssurajthakur06
 
IWISS Catalog 2024
IWISS Catalog 2024IWISS Catalog 2024
IWISS Catalog 2024
Iwiss Tools Co.,Ltd
 
Vernier Caliper and How to use Vernier Caliper.ppsx
Vernier Caliper and How to use Vernier Caliper.ppsxVernier Caliper and How to use Vernier Caliper.ppsx
Vernier Caliper and How to use Vernier Caliper.ppsx
Tool and Die Tech
 
DBMS Commands DDL DML DCL ENTITY RELATIONSHIP.pptx
DBMS Commands  DDL DML DCL ENTITY RELATIONSHIP.pptxDBMS Commands  DDL DML DCL ENTITY RELATIONSHIP.pptx
DBMS Commands DDL DML DCL ENTITY RELATIONSHIP.pptx
Tulasi72
 
SCADAmetrics Instrumentation for Sensus Water Meters - Core and Main Training...
SCADAmetrics Instrumentation for Sensus Water Meters - Core and Main Training...SCADAmetrics Instrumentation for Sensus Water Meters - Core and Main Training...
SCADAmetrics Instrumentation for Sensus Water Meters - Core and Main Training...
Jim Mimlitz, P.E.
 
Quadcopter Dynamics, Stability and Control
Quadcopter Dynamics, Stability and ControlQuadcopter Dynamics, Stability and Control
Quadcopter Dynamics, Stability and Control
Blesson Easo Varghese
 
Concepts Basic/ Technical Electronic Material.pdf
Concepts Basic/ Technical Electronic Material.pdfConcepts Basic/ Technical Electronic Material.pdf
Concepts Basic/ Technical Electronic Material.pdf
OBD II
 
IS Code SP 23: Handbook on concrete mixes
IS Code SP 23: Handbook  on concrete mixesIS Code SP 23: Handbook  on concrete mixes
IS Code SP 23: Handbook on concrete mixes
Mani Krishna Sarkar
 
1239_2.pdf IS CODE FOR GI PIPE FOR PROCUREMENT
1239_2.pdf IS CODE FOR GI PIPE FOR PROCUREMENT1239_2.pdf IS CODE FOR GI PIPE FOR PROCUREMENT
1239_2.pdf IS CODE FOR GI PIPE FOR PROCUREMENT
Mani Krishna Sarkar
 
Time-State Analytics: MinneAnalytics 2024 Talk
Time-State Analytics: MinneAnalytics 2024 TalkTime-State Analytics: MinneAnalytics 2024 Talk
Time-State Analytics: MinneAnalytics 2024 Talk
Evan Chan
 
Stiffness Method for structure analysis - Truss
Stiffness Method  for structure analysis - TrussStiffness Method  for structure analysis - Truss
Stiffness Method for structure analysis - Truss
adninhaerul
 
Design and Application of Side Channel Spillways
Design and Application of Side Channel SpillwaysDesign and Application of Side Channel Spillways
Design and Application of Side Channel Spillways
ahmed42488
 
Girls Call Chennai 000XX00000 Provide Best And Top Girl Service And No1 in City
Girls Call Chennai 000XX00000 Provide Best And Top Girl Service And No1 in CityGirls Call Chennai 000XX00000 Provide Best And Top Girl Service And No1 in City
Girls Call Chennai 000XX00000 Provide Best And Top Girl Service And No1 in City
sunnuchadda
 
OSHA LOTO training, LOTO, lock out tag out
OSHA LOTO training, LOTO, lock out tag outOSHA LOTO training, LOTO, lock out tag out
OSHA LOTO training, LOTO, lock out tag out
Ateeb19
 
GUIA_LEGAL_CHAPTER-9_COLOMBIAN ELECTRICITY (1).pdf
GUIA_LEGAL_CHAPTER-9_COLOMBIAN ELECTRICITY (1).pdfGUIA_LEGAL_CHAPTER-9_COLOMBIAN ELECTRICITY (1).pdf
GUIA_LEGAL_CHAPTER-9_COLOMBIAN ELECTRICITY (1).pdf
ProexportColombia1
 
Lecture 3 Biomass energy...............ppt
Lecture 3 Biomass energy...............pptLecture 3 Biomass energy...............ppt
Lecture 3 Biomass energy...............ppt
RujanTimsina1
 

Recently uploaded (20)

NEC 2023 NATIONAL ELECTRICAL DODE 2023 NEC
NEC 2023 NATIONAL ELECTRICAL DODE 2023 NECNEC 2023 NATIONAL ELECTRICAL DODE 2023 NEC
NEC 2023 NATIONAL ELECTRICAL DODE 2023 NEC
 
Monitoring and reporting of transparent forest data and information under the...
Monitoring and reporting of transparent forest data and information under the...Monitoring and reporting of transparent forest data and information under the...
Monitoring and reporting of transparent forest data and information under the...
 
21EC63_Module1B.pptx VLSI design 21ec63 MOS TRANSISTOR THEORY
21EC63_Module1B.pptx VLSI design 21ec63 MOS TRANSISTOR THEORY21EC63_Module1B.pptx VLSI design 21ec63 MOS TRANSISTOR THEORY
21EC63_Module1B.pptx VLSI design 21ec63 MOS TRANSISTOR THEORY
 
UNIT I INCEPTION OF INFORMATION DESIGN 20CDE09-ID
UNIT I INCEPTION OF INFORMATION DESIGN 20CDE09-IDUNIT I INCEPTION OF INFORMATION DESIGN 20CDE09-ID
UNIT I INCEPTION OF INFORMATION DESIGN 20CDE09-ID
 
PMSM-Motor-Control : A research about FOC
PMSM-Motor-Control : A research about FOCPMSM-Motor-Control : A research about FOC
PMSM-Motor-Control : A research about FOC
 
IWISS Catalog 2024
IWISS Catalog 2024IWISS Catalog 2024
IWISS Catalog 2024
 
Vernier Caliper and How to use Vernier Caliper.ppsx
Vernier Caliper and How to use Vernier Caliper.ppsxVernier Caliper and How to use Vernier Caliper.ppsx
Vernier Caliper and How to use Vernier Caliper.ppsx
 
DBMS Commands DDL DML DCL ENTITY RELATIONSHIP.pptx
DBMS Commands  DDL DML DCL ENTITY RELATIONSHIP.pptxDBMS Commands  DDL DML DCL ENTITY RELATIONSHIP.pptx
DBMS Commands DDL DML DCL ENTITY RELATIONSHIP.pptx
 
SCADAmetrics Instrumentation for Sensus Water Meters - Core and Main Training...
SCADAmetrics Instrumentation for Sensus Water Meters - Core and Main Training...SCADAmetrics Instrumentation for Sensus Water Meters - Core and Main Training...
SCADAmetrics Instrumentation for Sensus Water Meters - Core and Main Training...
 
Quadcopter Dynamics, Stability and Control
Quadcopter Dynamics, Stability and ControlQuadcopter Dynamics, Stability and Control
Quadcopter Dynamics, Stability and Control
 
Concepts Basic/ Technical Electronic Material.pdf
Concepts Basic/ Technical Electronic Material.pdfConcepts Basic/ Technical Electronic Material.pdf
Concepts Basic/ Technical Electronic Material.pdf
 
IS Code SP 23: Handbook on concrete mixes
IS Code SP 23: Handbook  on concrete mixesIS Code SP 23: Handbook  on concrete mixes
IS Code SP 23: Handbook on concrete mixes
 
1239_2.pdf IS CODE FOR GI PIPE FOR PROCUREMENT
1239_2.pdf IS CODE FOR GI PIPE FOR PROCUREMENT1239_2.pdf IS CODE FOR GI PIPE FOR PROCUREMENT
1239_2.pdf IS CODE FOR GI PIPE FOR PROCUREMENT
 
Time-State Analytics: MinneAnalytics 2024 Talk
Time-State Analytics: MinneAnalytics 2024 TalkTime-State Analytics: MinneAnalytics 2024 Talk
Time-State Analytics: MinneAnalytics 2024 Talk
 
Stiffness Method for structure analysis - Truss
Stiffness Method  for structure analysis - TrussStiffness Method  for structure analysis - Truss
Stiffness Method for structure analysis - Truss
 
Design and Application of Side Channel Spillways
Design and Application of Side Channel SpillwaysDesign and Application of Side Channel Spillways
Design and Application of Side Channel Spillways
 
Girls Call Chennai 000XX00000 Provide Best And Top Girl Service And No1 in City
Girls Call Chennai 000XX00000 Provide Best And Top Girl Service And No1 in CityGirls Call Chennai 000XX00000 Provide Best And Top Girl Service And No1 in City
Girls Call Chennai 000XX00000 Provide Best And Top Girl Service And No1 in City
 
OSHA LOTO training, LOTO, lock out tag out
OSHA LOTO training, LOTO, lock out tag outOSHA LOTO training, LOTO, lock out tag out
OSHA LOTO training, LOTO, lock out tag out
 
GUIA_LEGAL_CHAPTER-9_COLOMBIAN ELECTRICITY (1).pdf
GUIA_LEGAL_CHAPTER-9_COLOMBIAN ELECTRICITY (1).pdfGUIA_LEGAL_CHAPTER-9_COLOMBIAN ELECTRICITY (1).pdf
GUIA_LEGAL_CHAPTER-9_COLOMBIAN ELECTRICITY (1).pdf
 
Lecture 3 Biomass energy...............ppt
Lecture 3 Biomass energy...............pptLecture 3 Biomass energy...............ppt
Lecture 3 Biomass energy...............ppt
 

EDM.pptx

  • 2. Introduction  Electrical discharge machining (EDM) is an electro-thermal process.  It is one of the most extensively used material removal processes.  Its unique feature is to use thermal energy to machine electrically conductive parts regardless of hardness.  With no direct contact between the tool and workpiece, EDM supports smooth machining.  The main principle of EDM is to erode a material through the effect of electric discharge (spark). EDM Ref: https://www.makino.com
  • 3. History  The origin of EDM dates back to 1770 when English scientist Joseph Priestly discovered the erosive effect of electrical discharges.  Several attempts were made to achieve a controlled EDM process.  But, These processes were not very precise due to overheating of the machining area.  Pioneering work on EDM was carried out in 1943 by two Russian scientists, B.R. and N.I. Lazarenko at the Moscow University.  They developed a controlled process for machining materials by vaporizing and melting its surface.
  • 4. History (Cont…)  The RC (resistance–capacitance) relaxation circuit was introduced in 1950s.  Later, it served as the model for successive developments in EDM technology.  It provided the first consistent dependable control of pulse times. RC circuit Ref: https://www.sciencedirect.com
  • 5. Main Components in EDM  Workpiece and tool  Electrical power supply  Dielectric  Servo control unit  Fixture Ref: https://www.researchgate.net Schematic of EDM process
  • 6. Working Principle  A potential difference is applied between the tool and workpiece.  Depending upon the applied potential difference and the gap between the tool and workpiece, an electric field would be established.  As the electric field is established between the tool and the job, the free electrons on the tool are subjected to electrostatic forces.  If the bonding energy of the electrons is less, electrons would be emitted from the tool (cold emission).  They start moving towards the job and there would be collisions between the electrons and dielectric molecules (ionization). Ref: https://www.rajagiritech.ac.in
  • 7. Working Principle (Cont…)  This cyclic process would increase the concentration of electrons and ions in the dielectric medium between the tool and the job at the spark gap.  Concentration would be so high that the matter existing in that channel could be characterized as “plasma”.  Electrical resistance of such plasma channel would be very less.  Thus all of a sudden, a large number of electrons will flow from the tool to the job and ions from the job to the tool.  This is called avalanche motion of electrons.  High speed electrons then impinge on the job and ions on the tool. Plasma channel Ref: https://link.springer.com
  • 8. Working Principle (Cont…)  Kinetic energy of the electrons and ions on impact with the surface of the job and tool respectively would be converted into thermal energy or heat flux.  Localized extreme rise in temperature leads to material removal.  Material removal occurs due to instant vaporization of the material as well as due to melting.  As the potential difference is withdrawn, the plasma channel is no longer sustained.  As the plasma channel collapse, it generates pressure or shock waves, which evacuates the molten material forming a crater of removed material around the site of the spark. Spark initiation Ref: https://www.sciencedirect.com
  • 9. EDM Process Parameters Discharge Voltage  Discharge voltage in EDM is related to the spark gap and break down strength of the dielectric.  Before current can flow, the open gap voltage increases until it has created an ionization path through the dielectric.  Once the current starts to flow voltage drops and stabilizes at the working gap level.  The preset voltage determines the width of the spark gap between the leading edge of the electrode and workpiece. Ref: https://www.slideshare.net
  • 10. EDM Process Parameters  It is most important machining parameter in EDM.  Higher current is directly related to the surface area of the cut.  It is used in roughing operations and cavities.  Higher current improves MRR, but it leads to poor surface finish and tool wear.  New improved electrode materials, especially graphite, can work on high currents without much damage. Peak Current Ref: https://www.sciencedirect.com
  • 11. EDM Process Parameters Pulse Duration and Pulse Interval  Pulse on-time is commonly referred to as pulse duration and pulse off-time is called pulse interval.  With longer pulse duration, more workpiece material will be melted away.  Metal removal is directly proportional to the amount of energy applied during the on-time.  Pulse interval will affect the speed and stability of the cut.  In theory, the shorter the interval, the faster will be the machining operation.  But if the interval is too short, the ejected workpiece material will not be swept away by the flow of the dielectric and the fluid will not be deionized.  This will cause the next spark to be unstable. Ref: https://www.sciencedirect.com
  • 12. EDM Process Parameters Polarity  The polarity of the electrode can be either positive or negative.  The plasma channel is composed of ion and electron flows.  As the electron processes (mass smaller than anions) show quicker reaction, the anode material is worn out predominantly. Ref: https://www.researchgate.net
  • 13. EDM Process Parameters Electrode Gap  The tool servo-mechanism is of considerable importance in the efficient working of EDM.  Its function is to control responsively the working gap to the set value.  The gap stability and the reaction speed of the system is important for good performance.  Gap width is not measurable directly, but can be inferred from the average gap voltage. Ref: https://www.edm.kd-solution.com
  • 14. Properties of Tool Materials A tool material need to have these properties:  High electrical conductivity  High thermal conductivity  Higher density  High melting point  Easy manufacturability  Graphite is the most commonly used material.  Other materials are brass, tellurium copper, electrolytic oxygen free copper etc.
  • 15. EDM Surface Layers  There is a top white layer which crystallizes from the liquid cooled at high speed.  The depth of this top melted zone depends on the pulse energy and duration.  Below the top layer there is a chemically affected layer with changes in the average chemical composition and phase changes.  There after, a plastically deformed zone is observed with strains. Surface layers after electrical discharge machining Ref: https://www.sciencedirect.com
  • 16. Surface Modifications  When mild steel is eroded in liquid medium paraffin using copper electrode, the workpiece is coated with a very hard layer.  Using Titanium powder compact electrodes with carbon steel results increase in hardness of steel.  Powder-mixed dielectric is used to facilitate ignition process and get good surface finish.  Some powder that is usually used in doping are Ni, Co, Ti, Cr etc.  Abrasive powders such as silicon carbide and alumina are mixed in the dielectric to improve the material removal rate.
  • 17. Product Quality Issues  surface roughness in EDM would increase with increase in spark energy.  Surface finish can be improved by decreasing working voltage, working current and pulse on time.  Taper cut can be prevented by suitable insulation of the tool.  Overcut cannot be prevented as it is inherent to the EDM process.  But the tool design can be done in such a way so that same gets compensated. Ref: https://www.sciencedirect.com
  • 18. Conclusions  EDM is a viable machining option of producing highly complex parts.  Extremely hard materials can also be machined to very close clearances by this.  Very small workpieces can be machined where conventional tools may damage the part from excess cutting tool pressure.  There is no direct contact between tool and work piece.  Therefore, delicate sections and weak materials can be machined without perceivable distortion.
  • 19. Conclusions (Cont…)  Material removal in EDM mainly occurs due to formation of shock waves as the plasma channel collapse.  Material removal depends mainly on thermal properties of the work material rather than its strength, hardness etc.  Hybrid processes enhance stability by influencing the flushing.  Material transfer from electrode bodies and material transfer from powders suspended dielectric is under research.