This document provides an introduction to electrical discharge machining (EDM). EDM is an unconventional machining process where material is removed by electric sparks between an electrode tool and conductive workpiece, with no direct contact between them. Key aspects of EDM covered include the construction of EDM machines, the role of dielectric fluids, factors that affect the material removal rate such as capacitance and spark parameters, and electrode tool materials and wear characteristics. Graphite, copper, and copper-tungsten are commonly used as tool materials in EDM due to properties like machinability and erosion resistance.

1. INTRODUCTION TO
UNCONVENTIONALMACHINING PROCESS
Prepared by
L.LOGANATHAN,M.E,(PhD),
Department of Mechanical Engineering,
Kamaraj college of Engineering and
Technology.

2. Syllabus
• Unconventional machining Process
• Need
• Classification
• Brief overview

3. WHAT IS UCM?
An unconventional(non-traditional) machining process can be
defined as a material removal process in which no direct contact
between tool and work-piece occurs. In this type of machining
process, a form of energy is used to remove unwanted material from
a given workpiece.

4. Conventional Machining Process
• Metal Removal ?
• Nature of Contact ?
• Scrap ?

5. Demerits
• Disposal of Waste
• By products of chips
• Work holding Devices for larger cutting
force
• Heat Generation
• Not possible without chips

6. Unconventional Manufacturing
process
• Unconventional Manufacturing process
1. Unconventional Machining process
or
Non Traditional Machining Process
2. Unconventional Forming process

7. Unconventional
Manufacturing process
Machining process
• Metal Removal
• No Direct Contact b/w
tool and work piece
Forming process
• Metals are formed
• Releases large amount of
Energy in very short time
interval

8. Need for UCM
• Machining – produces finished products with high degree of
accuracy
• Conventional machining
• Utilizes cutting tools (harder than workpiece material).
• Needs a contact between the tool and workpiece.
• Needs a relative motion between the tool and workpiece.

9. Need
•
•
•
•
•
•
The need for higher productivity, accuracy and surface quality
Improve the capability of automation system and decreasing their
sophistication (decreasing the investment cost) requirements
Very hard fragile materials difficult to clamp for traditional
machining
When the work piece is too flexible or slender
When the shape of the part is too complex
Internal and external profiles, or small diameter holes.

10. 12
Unconventional Machining Processes – Based on
Energy

11. 13
Unconventional Machining Processes – Based
Mechanism

12. 14
Unconventional Machining Processes – Based on
Energy used for Removal

13. 15
Unconventional Machining Processes – Based on
Transfer of Energy

14. 16
Mechanical Based Processes
1. Working principles
2. Equipment used
3. Process parameters
4. MRR
5. Variation in techniques used
6. Applications
AJM
WJM
AWJM
USM

15. 17
Electrical Based Processes
1. Working principle
2. Equipment used
3. Process parameters
4. Surface finish & MRR
5. Electrode/Tool
6. Power & Control circuits
7. Tool wear
8. Dielectric
9. Flushing
10. Applications
Electrical
EDM
WEDM

16. 18
Chemical & Electrochemical Based Processes
1. Working principles
2. Etchants & Maskants
3. Techniques of applying maskants
4. Process parameters
5. Surface finish & MRR
6. Electrical circuits in case of ECM
7. Applications
CHM
ECM
ECG
ECH

17. 19
Thermal Based Processes
1. Working principles
2. Equipment used
3. Types
4. Beam control techniques
5. Applications
LBM
PAM
EBM

18. Selection Process
• Selection Process is based of following
parameters
– Physical Parameter
– Shapes to be Machined
– Process Capability
– Economic consideration

19. Physical Parameter
fluid
Parameter ECM EDM EBM LBM PAM USM AJM
Potential, V 5- 30 50-500 200 x 103 4.5 x 103 250 220 220
Current, A 40,000 15-500 0.001 2 600 12 1.0
Power, kW 100 2.70 0.15 20 220 2.4 0.22
Gap, mm 0.5 0.05 100 150 7.5 0.25 0.75
Medium Electrolyte Die electric Vacuum Air Argon NitrogenAbrasive
grains
Work
Material
M/C diff Tungsten
carbide
All Mtl All Mtl All Mtl Tungsten HSS
carbide

20. Shapes to be Machined
Process Machines
Holes ( Micro, Small,
deep,Shallow)
LBM, EBM,ECM, USM & EDM
Precision Work USM & EDM
Horning ECM
Etching ECM & EDM
Grinding AJM & EDM
Deburring USM & AJM
Threading EDM
Profile Cut PAM

21. Process Capability or Machining Characteristics
Process
MRR
( mm3/s )
Surface Finish
(μm)
Accuracy
(μm)
Power (kW/
cm3/ min
LBM 0.10 0.4 – 6.0 25 2700
EBM 0.15 - 40 0.4 – 6.0 25 450
EDM 15 - 80 0.25 10 1.8
ECM 27 0.2 -0.8 50 7.5
PAM 2500 Rough 250 0.90
USM 14 0.2 – 0.7 7.5 9.0
AJM 0.014 0.5- 1.2 50 312.5

22. Process Economy
Process Capital Cost Tool & Fixtures
Power
Requirement
Efficiency
EDM Medium High Low High
CHM Medium Low High Medium
ECM V. High Medium Medium V. Low
AJM V. Low Low Low Low
USM High High Low Medium
EBM High Low Low V. High
LBM Medium Low V. Low V. High
PAM V. Low Low V. Low V. Low
Convention
al
V. Low Low
Low
V. Low

23. Limitation
• More Expensive
• Slow Process
• Commercial

24. UNIT 2
MECHANICAL ENERGY BASEDPROCESS
B
ME6004 UNCONVENTIONAL MACHINING
PROCESSES

25. SYLLABUS
 Abrasive Jet Machining (AJM)
 Water Jet Machining (WJM)
 Abrasive Water Jet Machining (AWJM)
 Ultrasonic Machining. ( USM)
 Working Principles – equipment used – Process
parameters – MRR-Variation in techniques used –
Applications.

26. ABRASIVE JET MACHINING (AJM)
Principle
In Abrasive Jet Machining process, a
high speed stream of abrasive particles mixed with
high pressure air or gas which is injected on the
work piece through nozzle

27. Schematic Representation

30. Typical AJM Parameters
Abrasives used.
 Aluminum Oxide (Al o



Silicon Carbide (Sic)
Glass Powder.
Dolomite
) 10 to 50 mic
25 to 50 mic
0.3 to 0.6 mm
200 grit size
Working Medium.


Dry air
Gases ( Nitrogen or carbon dioxide)

31. Nozzle Material
 Tungsten Carbide
 Silicon carbonate
 ABRASIVE MATERIAL
Abrasive material Grit size (μin) Orifice diameter (in)
Aluminum oxide 10 - 50 0.005 - 0.018
Silicon carbide 25 - 50 0.008 - 0.018
Glass beads 2500 0.026 - 0.05

32. ADVANTAGES
 Low capital cost
 Less vibration
 No heat generated in the work piece
 Eco friendly
 Only one tool is required

33. DISADVANTAGES
 Low metal removal rate
 Abrasive powder can not be reused
 The machining accuracy is poor
 Nozzle wear rate is high

34. Water Jet Machining
Principle
In WJM, the high velocity of water jet
comes out of the nozzle and strikes the material, its
kinetic energy is converted into pressure energy
including high stress in the work material. when this
exceeds the ultimate shear stress of the material,
small chips of the material get loosened and fresh
surface is exposed.

35. Schematic Representation

36. PROCESS PARAMETERS
 Material removal rate(MRR)
-Depends on the reactive force of the jet
Reactive force = Mass flow rate (m) X jet
velocity (V)
 Geometry and finish of work piece
 Wear rate of the nozzle

37. Advantages of water jet cutting
 There is no heat generated in water jet cutting; which
is especially useful for cutting tool and other metals
where excessive heat may change the properties of
the material.
 Unlike machining or grinding, water jet cutting does
not produce any dust or particles

38. Disadvantages of water jet cutting
 One of the main disadvantages of water jet cutting is
that a limited number of materials can be cut
economically.
 Thick parts cannot be cut by this process
economically and accurately
 Taper is also a problem with water jet cutting in
very thick materials.
 Taper is when the jet exits the part at different angle
than it enters the part, and cause dimensional
inaccuracy.

39. Applications Of WJM Process
 Water jet cutting is mostly used to cut lower strength
materials such as wood, plastics and aluminum.
 When abrasives are added, (abrasive water jet
cutting) stronger materials such as steel and tool steel
can be cut.

40. Abrasive Water Jet Machining
 Principle:
In abrasive water jet machining process a
high stream of abrasive jet particles is mixed with
pressurized water & injected through the nozzle on
the work piece.

41. Schematic Representation

42. Advantages of Abrasive water jet cutting
 In most of the cases, no secondary finishing required
 No cutter induced distortion
 Low cutting forces on work pieces
 Limited tooling requirements
 Little to no cutting burr
 Typical finish 125-250 microns
 Smaller kerfs size reduces material wastages
 No heat affected zone

43. CONTD…
 Localizes structural changes
 No cutter induced metal contamination
 Eliminates thermal distortion
 No slag or cutting dross
 Precise, multi plane cutting of contours, shapes, and
bevels of any angle.

44. Disadvantages of Abrasive water jet cutting
 Cannot drill flat bottom
 Cannot cut materials that degrades quickly with
moisture

45. Ultrasonic Machining
Principle
 In the Ultrasonic Machining process the
material is removed by micro-chipping or erosion with
abrasive particles.
 The tool forces the abrasive grits, in the gap between the
tool and the work piece, to impact normally and
successively on the work surface, thereby machining the
work surface.

46. Contd….
 In USM process, the tool , made of softer material
than that of the work piece, is oscillated by the
Booster and Sonotrode at a frequency of about 20
kHz with an amplitude of about 25.4 um(0.001 in).

47. Schematic Representation

48. Schematic Representation

49. PROCESS PARAMETER
Effect of amplitude and frequency of vibration
on MRR

 MRR is directly proportional to the first power of
frequency for a fixed amplitude
Theoretical
M
R
R
Frequency
Actual
M
R
R
High
amplitude
Low
frequency
High
frequency

50. CONTD…
EFFECT `VELOCITY`
MRR IS DIRECTLY PROPORTIONAL TO THE PARTICLE
VELOCITY
M
R
R
Feed force
Mean grain
diameter
Surface
rough

51. CONTD..
 EFFECT OF STATIC LOADING OR FEED
FORCE:
- MRR increases with an increase in feed
force.
 EFFECT OF GRAIN SIZE:
1. - Grain size increases with an increase in
MRR

52. Advantages of USM
 There is no cutting forces therefore clamping is not
required except for controlled motion of the work
piece
 Extremely hard and brittle materials can be easily
machined
 There is no heat affected zone.
 Can machine harder metals
 Faster than EDM
 No tool wear at all.
 No heat affected zone.
 Better finish and accuracy.

53. USMApplications
 Hard, brittle work materials such as ceramics, glass,
and carbides.


 Also successful on certain metals, such as stainless steel and
titanium.
• Shapes include non-round holes, holes along a curved axis.
• “Coining operations” - pattern on tool is imparted to a flat work
surface

54. UNCONVENTIONALMACHINING
PROCESS– UNIT3
Electrical Energybased processes

55. Electrical Energy based processes
• Electrical energy is directly used to cut the
material to get the finalshape and size
– Electrical discharge machining (EDM)
– Wire cut Electrical Discharge Machining (WCEDM)

56. Electrical Discharge Machining (EDM)
• Principle
– Metal is removed by producing powerful electric
spark discharge between the tool (cathode) and
the work material(anode)
– Also known as Spark erosion machining or electro
erosion machining

57. Why EDM?
• EDMhasthe following advantages:
• 1. Cavities with thin walls and finefeatures
canbe produced.
• 2. Difficult geometry ispossible.
• 3. Theuseof EDMis not affected bythe
hardnessof the workmaterial.
• 4. Theprocessis burr-free.

61. EDM
• Construction and Working

63. EDM
• Dielectric Fluid
– Fluid medium which doesn’t conduct electricity
– Dielectric fluids generally used are paraffin, white
spirit, kerosene, mineral oil
– Must freely circulate between the work piece and
tool which are submerged init
– Eroded particles must be flushed out easily
– Should be available @reasonableprice
– Dielectric fluid must be filtered before reuse so
that chip contamination of fluid will not affect
machining accuracy

64. EDM
• Functions of dielectricfluid
– Acts asan insulating medium
– Coolsthe spark region & helps in keeping the tool
and work piece cool
– Carries away the eroded material along with it
– Maintains aconstant resistance acrossthe gap
– Remainselectrically non-conductive

65. EDM
• Toolmaterials and tool wear
– Metallic materials
• Copper, Brass,Copper-tungsten
– Non metallic materials
• graphite
– Combination of metallic and nonmetallic
• Copper – graphite
– Three most commonly used tool materials are
• Copper, graphite, copper-tungsten

66. EDM
• Tool materials
– Graphite
• Non-metallic
• Canbe produced by molding, milling, grinding
• Wide range of grades are available for wideapplications
• It is abrasive and gives better MRRand surfacefinish
• But costlier than copper
– Copper
• Secondchoice for tool material aftergraphite
• Canbe produced by casting or machining
• Cutools with very complex features are formed by chemical
etching or electroforming
– Copper-tungsten
• Difficult to machine and also haslowMRR
• Costlier than graphite andcopper

67. EDM
• Selection of cutting toolis influenced by
– Sizeof electrode
– Volume of material to beremoved
– Surfacefinish required
– Toleranceallowable
– Nature of coolantapplication
• Basicrequirement of any tool materialsare
– It should havelow erosionrate
– Should be electrically conductive
– Should havegood machinability
– Melting point of tool should be high
– Should havehigh electron emission

68. EDM
• Tool wear
– Tooldoes not comesin contact with thework
– So,life of tool is long and lesswear takesplace
Wear ratio = vol. of workmaterial removed
vol. of electrodeconsumed
• Toolwear ratio for
– Brasselectrode is 1:1
– Copper of 2:1
– Copper tungsten is 8:1
– Graphite varies between 5 and 50:1

69. EDM
• Metal Removal Rate(MRR)
– Defined asvolume of metal removed per unit time
– Depends upon current intensity and it
increases with current
– Usually a rough cut with heavy current and
finishing cut with alesscurrent isperformed
– MRRup to 80Cu.mm/S, canbeobtained
– Surface finish of 0.25 microns isobtained
– Tolerances of the order of ±0.05 to 0.13 mm are
commonly achieved

70. EDM
• Factorsaffecting MRR
– Increases with forced circulation of dielectricfluid
– Increases with capacitance
– Increases up to an optimal value of work-tool gap,
after that it drops suddenly
– Increases up to an optimum value of spark
discharge time, after that itdecreases
– MRR is maximum, when the pressure is below
atmospheric pressure

71. EDM
• Power generating circuits
– Resistancecapacitance circuit (RCCircuit)
– R-C-LCircuit

72. EDM
– Rotary pulse generator circuit
– Controlled pulse generatorcircuit

73. EDM
• ProcessParameters
– Operating parameters
• Electrical energy
• Voltage
• Time interval
• Instantaneous current
• Torque
• Pulse width
– Taper
– Surface finish
• Energy of the pulse
• Frequency of operation
– Current density

74. EDM
• Characteristics of EDM
Metal removaltechnique Byusing powerful electric spark
Work material Electrically conductive materials
Toolmaterial Copper, alloy of Zinc, yellow brass,Copper-Tungsten
MRR 15 to 80Cu.mm/S
Spark gap 0.005 to 0.05mm
Spark frequency 200 to 500KHz
Volts 30 to 250V
Current 5 to 60A
Temperature 10,000 degree celcius
Dielectricfluid Petroleum basedHCfluids, Paraffin, White Spirit

75. EDM
• Applications
– Production of complicated and irregular profiles
– Thread cutting in jobs
– Drilling of microholes
– Helical profile drilling
– Curved hole drilling
– Re-sharpening of cutting tool andbroaches
– Re-machining of die cavities without annealing
• Recent developments
– EDMchange from using relaxation circuit to faster
and more efficient impulsecircuits
– Instead of using Cu;WCis used aselectrode

76. EDM
• Advantages
– Canbe used to machine various conductive materials
– Givesgood surface finish
– Machining of very thin section ispossible
– Doesnot leaves any chips or burrs on the workpiece
– High accuracy is obtained
– Fine holes canbe easily drilled
– Process once started does not need constant
operators attention
– It is aquicker process
– Well suited to machine complicatedcomponents

77. EDM
• Disadvantages
– Used to machine only electrically conductive
materials
– Non-metallic compounds such as plastics,
ceramics or glasscannever be machined
– Suitable for machining small work pieces
– Electrode wear and overcut are seriousproblems
– Perfect square corners cannot be machined
– MRRisslow
– Power requirement is high
– The surface machined has been found to have
micro holes

78. Wire Cut Electrical Discharge
Machining (WC-EDM)
• Principle
– Metal is removed by producing powerful electric
spark discharge between the tool (cathode) and
the work material(anode)
– Also known as Spark erosion machining or electro
erosion machining

79. Wire Cut Electro-DischargeMachining
(WCEDM)

80. WCEDM

81. WCEDM
• Applications
– Best suited for production of gears, tools, dies,
rotors, turbine blades andcams
• Disadvantages
– Capital cost is high
– Cutting rate isslow
– Not suitable for large workpieces

82. WCEDM
• Features / Advantages ofWCEDM
– Manufacturing electrode
– Electrode wear
– Surface finishing
– Complicated shapes
– Time utilization
– Straight holes
– Rejection
– Economical
– Cycletime
– Inspection time

83. UNCONVENTIONALMACHINING
PROCESS– UNIT4
Chemical and Electrochemical
Energy Basedprocesses

84. Chemical EnergyBasedprocesses
• Metal is removed from the work piece
through a controlled etching of work piece
material in contact with thechemical solution
• Example
– Chemical Machining (CHM)

85. Electrochemical EnergyBased
processes
• Material is removed by ion displacement of
work piece material in contact with a chemical
solution
• Example
– Electro-Chemical Machining (ECM)
– Electro-Chemical Grinding (ECG)
– Electro-Chemical Honing (ECH)
– Electro-Chemical deburring (ECD)

86. Chemical Machining (CHM)
• Also called asChemical Milling (CHM)

87. CHM
• Etchant
– Chemical reagent used to removed the metal from
work piece
– Metal is removed by the chemical conversion of
metal into metallicsalt
S.No Material Etchant
1 Aluminum Causticsoda
2 Steel HCl/ HNO3Acid
3 Stainlesssteel FeCl
4 Magnesium HNO3Acid
5 Titanium HNO3Acid

88. CHM
• Maskant
– Areas of work piece which are covered with
a resistant material called amaskant or
resist
• Methods of masking
– Scribed or peeledmaskants
– Photo resists maskants
S.No Material Maskant
1 Aluminum Butyl rubber, neoprene rubber
2 Magnesium Polymers
3 Titanium Translucent chlorinated polymers
4 Nickel Neoprene
5 Ferrous metals Polyvinyl chloride, polyethylene

89. CHM
• Metal RemovalRate
– Depends upon selected etchant
– Fastwith certain etchant
– Etchrate is limited to 0.02 to 0.04mm/min
– Etching rate and depth of cut are high for hard
materials and low for softermaterials
– Surface finish of the order of5µ are produced
– Sizeof work piece depends upon the sizeof tank
– With optimum time, temperature and solution
control; accuracies of order ±0.01 mm isobtained

90. CHM
• Classification of CHM
– Chemicalblanking
• Material is etched entirely on the workpiece
• Used to cut out the parts from thin sheet metal or foil sheets
– Chemicalmachining
• Material is selectively etched from certain areas on work
piece
• Usedto remove material from thicker workpieces
• Application of CHM
– Usedin manufacturing burr freecomponents
– Applied where the depth of metal removal is critical to
few microns and the tolerances areclose

91. CHM
• Advantages of CHM
– Burr free components areproduced
– Most difficult to machine components aremachined
– High surface finish is obtained
– Stressfree components are produced
– No need of skilledlabor
– Tooling cost is low
– Complex contours canbe easily machined
– Hard and brittle materials canbemachined
– Both facesof work piece are simultaneouslymachined

92. CHM
• Disadvantages
– MRRislow
– Manufacturing cost is high
– Largefloor area isneeded
– Not possible to produce sharpcorners
– Work piece thickness that can be machinedis
limited

93. Electro Chemical machining (ECM)
• Principle
– Faraday’s first law
• Amount of material dissolved or deposited is
proportional to the quantity of electricity passed
– Faraday’s second law
• Amount of charge produced in the material is
proportional to its electrochemical equivalent of material
– Work piece connected to positive terminal
(cathode)
– Tool connected to negative terminal (anode)

94. ECM

95. ECM

96. ECM
• Analysis of metal removal
– Mild D.C. Voltage of about 5 to 30V is applied
between the tool and workpiece
– Current flows through the electrolyte with
charged ions
– The following reactions are possible at the
cathode (tool)
 Na++e- = Na
 Na+H2O= Na(OH)+H+
 2H++2e- =H2
– Thus there is no deposition on tool and only
hydrogen gasis evolved

97. ECM
• Similarly following reaction occur at theanode
Fe2+ +2e-
FeCl2
• Fe
• Fe+++2Cl-
• Fe+++2 (OH)-
• FeCl2+2(OH)
Fe(OH)2
Fe(OH)2+ 2Cl-
• This shows that work piece goesinto solution
and machined
– Bycombining the faraday’s first and second law of
electrolysis we get
• Where,
– W – massof ions dissolved in Kg
– E– Equivalent weight of substancedissolved
– T-time in S
– FaradaysConstant =96,500 Coulombs =26.8 Amp.Hr

98. ECM
• Tool material, tool design andinsulation
– Any material which is a good conductor of
electricity canbe used astool material
– Thegeneral requirement of tool material in ECM
are
• Must be agood conductor of electricity
• Must be chemically inert to the electrolyte
• Must be easilymachinable
• Must be rigid enough to take up the load due to fluid
pressure
– Thetool is made hollow for drillingholes
– Outer surface of the tool must be insulated by
vinyl, teflon, enamels or high temperaturevarnish

99. ECM
• While designing the tool, thefollowing
aspectsare taken into consideration
– Determine the tool shape
– Design the tool by considering the electrolyte
• Electrolyte
– Carries current between tool and workpiece
S.No Material Electrolyte
1 Febasedalloys 20%NaClsolution in water
2 Ni basedalloys Mixture of brine and sulphuricacid
3 Tibased alloys 10%HF+10%HCl+10%HNO3
4 Co-Crbased alloys NaCl
5 WCbasedalloys Strong alkaline solutions

100. ECM
• Theessential characteristics of electrolyteare
– Should be agood conductor of electricity
– Should have non-corrosive property
– Should be non-toxic
– Should have low viscosity
• Surface finish
– Depends mainly on
• Machining voltage
• Toolfeed rate
• Temperature of electrolyte
• Concentration of electrolyte

101. ECM
• Applications
– Tomachine complicated profiles like jet engine blades,
turbine blades, turbinewheels
– Todrill small deep holes in nozzles
– Tomachine cavities and holes of irregularshapes
– Tomachine blind holes and pockets in forgingdies
– Tomachine hard and heat resistant materials
• Limitations
– Sharpinternal corners cannot bemachined
– Postmachining cleaning isneeded
– Tooldesign is very complicated
– Control mechanism is needed to maintain high
tolerances

102. ECM
• Characteristics
Metal removaltechnique Faraday’slaw of electrolysis
Work material Difficult to machine
Toolmaterial Copper, brassor steel
Voltage 5 to 30v
Current 50 to 40000A
MRR 27 Cu.mm/S
Electrolyte 20%NaClsolution in water,
mixture of brine insulphuric
acid
Surfacefinish 0.2 to 0.8µ
Tolerance 0.005mm
Specific powerconsumption 7 W/Cu.mm/min

103. ECM
• Advantages
– MRRishigh
– Wear and tool tear isnegligible
– Machining is done at low voltage
– Intricate and complex shapes can be
machined easily
– Machined work surface is free of stress
– No cutting forces are involved
– High surface finish of order 0.2 to 0.8µ isobtained
– Tolerance of 0.005mm canbe obtained
– No burrs are produced

104. ECM
• Disadvantages
– Non conducting materials cannot bemachined
– Initial investment is quite high
– More spaceis required
– Machining process is comparatively low
– Power consumption is 100 times more than
conventional machining
– Difficulty in designing aproper tooling system
– Constant monitoring is required

105. ECM
S.No EDM ECM
1 Work piece is submerged in
dielectric fluid
Work piece need not to be
submerged in electrolyte
2 Toolwear takes place No tool wear
3 Control system is required No control system isrequired
4 Machining cannot be doneat
low voltages
Machining canbe done at low
voltages
5 MRRis slow compared to
ECM
MRRis high compared to
EDM
6 Lessenergy isconsumed More energy isconsumed

106. Electro Chemical Grinding (ECG)
• Materials that cannot be easily shapeddueto
their extreme hardness canbeground
– Example
• Cemented carbides
• Hardened steel
• Principle
– Work is machined by the combined action of
electrochemical effect and conventionalgrinding
operation

107. ECG

108. ECG

109. ECG
• Processparameters
– Current density
– Electrolyte
– Feed rate
– Grinding wheel speed
• Applications
– Best suited for high precision grinding ofhard
metals like WC
– Also suited to cut thin sections ofhard materials
without anydamage

110. ECG
• Advantages
– Tool wear is negligible
– Work is free of surface cracksand not subjectedto
any structural changes
– Burr and stress free components are produced
– Good surface is obtained
– Surface finish of 0.2 to 0.4µ areproduced
– Accuracy of 0.01mm canbe achieved
– Intricate paths canbe machined without any
distortion

111. ECG
• Disadvantages
– Initial cost ishigh
– Power consumption is high
– MRRislow
– Non conductive materials cannot bemachined
– Maintenance cost is high
– Tolerance achieves is low
– Preventive measures are needed against corrosion
of electrolyte

112. Electro Chemical Honing (ECH)
• Similar to ECG
• ECHusesrotating and reciprocating, non-
conducting bonded honing stones instead of a
conducting grinding wheel

113. ECH
• Advantages
– MRRis faster with reduced tool wear
– Burr and stress free components are produced
– Lesspressure is required between honing stones
and work piece
– Usedto machine burred edges
– Noise and distortion are reduced

114. UNCONVENTIONALMACHINING
PROCESS– UNIT5
Thermal EnergyBasedprocess

115. Thermal Energybased Processes
• Heat energy is concentrated on a small area of
work piece to melt and vaporize the tiny bits
of workmaterial
• Required shape is obtained by the continued
repetition of theprocess
• Example
1. Electron BeamMachining (EBM)
2. LaserBeamMachining (LBM)
3. PlasmaArc Machining (PAM)

116. Electron BeamMachining (EBM)
• A beam of high velocity electrons travelling at
half the velocity of light (1.6 X 10^8 m/S) are
focused on the work piece to remove the metal
• Principle
– When high velocity beam of electrons strike the work
piece its kinetic energy is converted intoheat
– This concentrated heat raises the temperature of work
piece material and vaporizes a small amount of it,
resulting in removal of material from work piece

117. EBM
• Types
– Machining inside the vacuumchamber
– Machining outside the vacuumchamber

118. EBM

119. EBM
• Processparameters
– Control of current
– Control of spotdiameter
– Control of focal distance of magneticlens
• Applications
– Usedfor micromachining operations
– Usedto drill holes in pressure differentialdevices
– Usedto remove small broken taps fromholes
– Usedto machine low thermal conductivityand
high melting point materials

120. EBM
Acceleratingvoltage 50 to 200KV
Beam current 100 to 1000µA
Electronvelocity 1.6X10^8 m/S
Medium Vacuum
Work piecematerials All materials
Depth ofcut Up to 6.5mm
MRR Up to 4.Cu.mm/S
Specific powerconsumption 0.5 to 50KW
Power density 6500 billion W/mm^2

121. EBM
• Advantages
– Excellent process for micromachining
– Very small holes and holes of different sizedcanbe
machined
– No mechanical contact between tool and workpiece
– Quick process
– Easily automated
– Closetolerances are obtained
– Brittle and fragile materials canbemachined
– Physicaland metallurgical damage to work piece are
less

122. EBM
• Disadvantages
– MRRis verylow
– Costof equipment ishigh
– Not suitable for large workpieces
– Little taper is produced onholes
– Vacuumrequirements limits the sizeof workpiece
– Not suitable to produce perfectlycylindrical
profiles
– Applicable for thin materials
– Energyconsumption is high

123. Laserbeam Machining (LBM)
• LASER – Light Amplification by Stimulated
Emissionof Radiation
• LikeEBM;LBMis also used to drill micro holes
up to 25µ
on the work piece by
• Principle
– Laser beam is focused
means of lens to give extremely high energy
density to melt and vaporize thework material

124. LBM

125. LBM

126. LBM
• Accuracy
– To get best possible results, the material should be
placed within atolerance of ±0.2mm focalpoint
• Lasingmaterials
– Solid laser
• Rubylaser, neodymium doped Yttrium –Aluminum –Garnet
(Nd-YAG)laser and neodymium doped glass laser
– GasLaser
• Canbe operated continuously
• Produces exceptionally high monochromaticity and high
stability of frequency
• Example
– Carbon dioxide Laser
– Helium-Neon Laser

127. LBM
• Processing with LASER
S.No Special characteristics of aLASER
beam
Cutting processcharacteristics
1 Canbe focused to amaximum or
minimum intensity asneeded
MRRis maximum tominimum
2 Canbe moved rapidly on work piece Cutting of complexshapes
3 Projected on the work piece ata
particular distance from thelens
Remote cutting over longstand-off
distances
4 Dedicated to on-line processes Re-routing is not necessary
5 Power is shared on ajob Twoor more cutssimultaneously

128. LBM
• Machining applications of LBM
– Laserin metal cutting
– Laserin drilling
– Laserin welding
• Conduction limited welding
• Deep penetration welding
– Laserfor surface treatment
– Other applications
• Sheet metal trimming
• Blanking
• Resistor trimming

129. LBM
• Characteristics
Metal removaltechnique Heating, melting & vaporization ofmaterial by
using high intensity of laserbeam
Work material All materials expect those having highthermal
conductivity
Tool Laserbeam of wavelength range 0.3 to 0.6µ
Power density 10^7 W/sq.mm
Output energylaser 20 J
MRR 6 Cu.mm/min
Pulse duration 1 millisecond
Dimensionalaccuracy ±0.025mm
Medium Atmosphere
Efficiency 10 to 15%
Specificpower
consumption
1000 W/Cu.mm/min

130. LBM
• Advantages
– Micro sizedholes are produced
– Soft materials like rubber canbemachined
– No tool wear
– No direct contact between tool and workpiece
– Dissimilar materials canbe easily welded
– Easily automated
– Hardness of material does not affect theprocess
– Heat affected zone is very small
– Deepholes of short diameter canbe easilydrilled

131. LBM
• Disadvantages
– Initial investment ishigh
– Operating cost is also quite high
– Highly skilled operators are needed
– Rateof production islow
– Safety procedures to be followed strictly
– Overall efficiency is extremely low
– Life of flash lamp isshort
– Machined hole is not round andstraight

132. PlasmaArc Machining (PAM)
or
PlasmaJet machining (PJM)
• Principle
– Material is removed by directing a high velocity jet
of high temperature [11000 to 28000 deg. celcius]
ionized gas on the work piece, which in turn melts
the material from workpiece

133. PAM

134. PAM

135. PAM
• Gasesused in PAM
– Gasused should not affect the electrode orwork
piece to bemachined
S.No Gas or GasMixture Material to bemachined
1 Nitrogen-
hydrogen, Argon-
hydrogen
Stainless steel, non ferrous
material
2 Nitrogen-hydrogen,
Compressed air
Carbon & alloy steel, castiron
3 Nitrogen,
nitrogen-hydrogen
Argon-hydrogen
Aluminum, Magnesium

136. PAM
• Types
– Direct arc plasma torch
– Indirect arc plasma torch
• Accuracy of PAM
– Accuracy of 1.4mm isobtained
– Accuracy on width of slots and diameter ofholes
is ordinarily from ±4mm to 150 mm thickplates

137. PAM
• Characteristics
Metal removaltechnique Heating, melting and vaporising by using plasma
Work material All materials which conductelectricity
Tool Plasmajet
Velocity of plasmajet 500 m/S
Power range 2 to 200KW
Current Ashigh as600 A
Voltage 40 to 250V
Cuttingspeed 0.1 to 7m/min
MRR 145 Cu.mm/min

138. PAM
• Processparameters
– Standoff distance
– Thermo physical and metallurgical properties of
plasma
– Cutting speed or velocity of plasmajet
• Applications
– Usedfor profile cutting
– Used for turning and milling of hard to machine
materials
– Canbe used for stack cutting, shapecutting
– Uniform thin film spraying of refractory materials
– Usedto cut alloy steels, SS,copper, nickel, titanium,
Aluminum and alloy of copper andnickel

139. PAM
• Advantages
– Usedto cut anymaterial
– Cutting rate ishigh
– Cancut plain carbon steel four times fasterthan
ordinary flame cutting process
– Usedfor rough turning of very difficultmaterials
• Disadvantages
– Produces tapered surface
– Noise protection isnecessary
– Equipment cost is high
– Protection of eyesis necessary for theoperator
– Work surface may undergo metallurgical changes