This document contains information about a student named Sourabh Tailor with roll number 2013btechme041. It discusses unconventional machining processes including electrochemical machining (ECM) and electric discharge machining (EDM). For ECM, it describes the principles, equipment, electrolyte, tools, advantages, disadvantages and applications. For EDM, it discusses the physical principles, characteristics, tools, dielectric fluid, advantages, disadvantages and applications such as wire EDM and electric discharge grinding.

1. Name:- Sourabh Tailor
Roll no :- 2013btechme041

2. Content
• INTRODUCTION
▫ Need of unconventional machine
▫ Unconventional machining
▫ Classification of NTMM
▫ Limitations of NTMM
• ECM
▫ Electro Chemical machining
▫ ECM Equipment
▫ Electrolyte
▫ Tool
▫ Advantageous
▫ Disadvantageous
▫ Application
▫ Electro chemical Grinding(ECG)

3. • EDM
▫ Physical principle
▫ Characteristics Of EDM
▫ EDM Tool
▫ Dialectical fluid
▫ Advantages
▫ Disadvantages
▫ Applications
▫ Wire EDM
▫ Electric Discharge Grinding (EDG)
Content

4. Need for Unconventional Processes
New materials having high strength and hardness, such as nimonic
alloys and alloys with alloying elements such as tungsten,
molybdenum, and columbium are difficult to machine by the
traditional methods.
By conventional machining the MRR reduces with an increase in the
work material hardness.
Need for development of non-traditional machining processes which
utilize other methods such as electrochemical processes for the
material removal.
Introduction

5. Need for Unconventional Processes
Complex shapes.
A very high accuracy is desired besides the complexity of the
surface to be machined.

6. Unconventional Machining
Different forms of energy directly applied to the workpiece to have
shape transformation or material removal from work surface.
No chips, No lay pattern on work surface, no direct physical contact
between the tool and the workpiece .
The tool material does not have to be harder than the work
material.
Tool forces do not increase as the work material gets harder.

7. Classification of NTMM
The Non-traditional Machining Methods are classified
according to the major energy sources employed in
machining.
1.Thermal Energy Methods
2.Electro - Chemical Energy Method
3.Chemical Energy Methods
4.Mechanical Energy Methods

8. Limitations of NTMM
Expensive set up, low MRR and skilled labour required.
The limitation of electrical machining methods is that the work
material must be an electrical conductor. Also, consumption of
electrical energy is very large.
The NTMM which have not been proved commercially
economical are: USM, AJM, CHM, EBM and PAM.

9. ECM

10. Electro Chemical Machining
Electrochemical machining is the reverse of electro plating.
The work-piece is made the anode, which is placed in close
proximity to an electrode (cathode), and a high- amperage direct
current is passed between them through an electrolyte, such as salt
water, flowing in the anode- cathode gap.
Metal is removed by anodic dissolution and is carried away in the
form of a hydroxide in the electrolyte for recycling or recovery.
MRR in ECM depends on atomic weight of work material.

11. Fig. :- Principle of ECM

12. Electrochemical Machining
Variation in the current density will result in work taking the
electrodes shape.
The electrode is fed with a constant velocity, and the
electrolyte is fed through the tool

13. Fig. :-ECMEquipment

14. ECM Equipment
Supply Voltage 2 to 35 V DC and Current 500 to 40,000 A.
The tool-to-work gap needs to be maintained at a very small value 0.1 to 0.25
mm. A servo drive is provided on the tool axis for this purpose.
The electrolyte needs to be pumped through this gap at high pressures
ranging from 0.70 to 3.00 MPa. This introduces a large amount of load on the
machine, because of the large working areas involved. Hence the machine
structure will have to be made rigid to a withstand such forces.
The electrolyte consists of the metal debris removed from the anode, which
will have to be filtered before it is re-pumped into the system.
Also a large amount of heat is generated during the electrolysis, which heats up
the electrolyte, and hence it needs to be cooled.

15. Electrolyte
The electrolyte is so chosen that the anode (workpiece) is
dissolved but no deposition takes place on the cathode
(tool).
Properties electrolyte should be
1.High electrical conductivity
2.Low viscosity
3.High specific heat
4.Chemical stability
5.Non-corrosive and non-toxic
6.Inexpensive and readily available.

16. Tool
The properties of tool materials should be:
1.High electrical and thermal conductivity
2.Easy machinability
3.Good stiffness
4.High corrosion resistance
Tool materials: Copper, brass, bronze, Al, Stainless Steel, nickel,
etc.
Material wear / Tool wear: Infinite

17. Advantages
1.Complex three-dimensional surfaces can be machined
accurately. Good for low machinability or complicated shapes.
2.As ECM leads to atomic level dissolution, the surface finish is
excellent (Ra 0.2 to 0.6 μm) with almost stress free machined
surface and without any thermal damage.
3.The tool wear is practically nil which results in a large number of
components produced per tool.
4.MRR is highest (1600 mm3/min) among NTMM and comparable
with conventional machining.

18. Disadvantages
1. Use of corrosive media as electrolytes make it difficult to
handle.
2. Sharp interior edges and corners re difficult to produce.
3. Very expensive machine.
4. Forces are large with this method because of fluid pumping
forces.
5. Very high specific energy consumption.(about 150times of
conventional processes.
6. Not applicable with electrically non-conducting materials and
jobs with very small dimensions.

19. Applications
•Any electrically conductive work materials irrespective of their
hardness, strength or even thermal properties.
•Shape application – blind complex cavities, curved surfaces ,
through cutting , large through cavities.
•It is used for marching of gas turbines blades.
•Die sinking
•Profiling and contouring
•Trepanning
•Grinding
•Drilling
•Micro-machining

20. Electrochemical Grinding (ECG)
•In ECG, the tool electrode is a rotating , metal bonded diamond grit
grinding wheel.
•As the electric current flows between the workpiece and the wheel,
through the electrolyte, the surface metal is changed to a metal
oxide, which is ground away by the abrasives. As the oxide film is
removed, new surface metal is oxidized and removed.
ECG is a low-voltage high-current electrical process.
The purpose of the abrasive is to increase the efficiency of the ECG
process and permit the continuance of the process.
The abrasive particles are always nonconductive material such as
aluminium oxide, diamond, or borazon . Thus they act as an
insulating spacer maintaining a separation of from 0.012 to 0.050
mm between the electrodes.

21. Fig :- Equipment setup and electrical circuit for
electrochemical grinding.

22. Electrochemical Grinding (ECG)
The process is used for shaping and sharpening carbide cutting
tools, which cause high wear rates on expensive diamond
wheels in normal grinding. Electrochemical grinding greatly
reduces this wheel wear.
Fragile parts (honeycomb structures), surgical needles, and
tips of assembled turbine blades have been ECG- processed
successfully.
Inter electrode gap in ECG is controlled by Controlling the size
of diamond particle in the wheel.

23. EDM

24. Physical Principle
Basicprocess

25. Physical Principle
An arc jumps between two points along the path of least
resistance.

26. Physical Principle
The energy of the arc is so concentrated that it causes the
electrode, and the work to melt. But the electrode material is
chosen so that it melts less.

27. Physical Principle
The metal and dielectric fluid is partly vaporized, causing
sudden expansion.

28. Physical Principle
The blast from the expanding vapours knocks some molten
particles loose, and the remaining molten metal hardens.

29. Characteristics of EDM
Mechanics of material removal - melting and evaporation
aided by cavitations.
The process is based on melting temperature, not hardness, so
some very hard materials can be machined this way.
The arc that jumps heats the metal, and about 1 to 10% of the
molten metal goes into the fluid. The melted metal then recast
layer is about 1 to 30 μm thick, and is generally hard and rough.
The electrode workpiece gap is in the range of 10 μm to 100
μm.

30. EDM Tool
• Prime requirements EDM tool Material
1.It should be electrically conductive.
2.It should have good machinability, thus allowing easy manufacture
of complex shapes.
3.It should have low erosion rate or good work to tool wear ratio.
4.It should have low electrical resistance.
5.It should have high melting point.
6.It should have high electron emission.

31. EDM Tool
The usual choices for tool(electrode) materials are
Copper,
brass,
alloys of zinc and tin,
hardened plain carbon steel,
copper tungsten,
silver tungsten,
tungsten carbide,
copper graphite, and graphite.
Electrical & thermal conductivity Good

32. Servo-Mechanism
The gap between the tool and work has a critical importance. As the
workpiece is machined, this gap tends to increase. For optimum
machining efficiency, this gap should be maintained constant. This is
done by servo- mechanism which controls the movement of the
electrode.

33. Dielectric Fluid
Fluid is used to act as a dielectric, and to help carry away
debris.
If the fluid is pumped through and out the end of the
electrode, particles will push out, and mainly collect at the
edges. They will lower the dielectric resistance, resulting in
more arcs. As a result the holes will be conical.
Quite often kerosene-basedoil.
The dielectric fluid is circulated through the tool at a pressure
of 0.35 N/m2 or less. To free it from eroded metal particles, it is
circulated through a filter.

34. Advantages
•Hardness, toughness or brittleness of the ,material poses no
problem. Due to this EDM can be used for machining materials that
are too hard or brittle to be machined by conventional methods.
•The method does not leave any chips or burrs on the work piece.
•Cutting forces are virtually zero. So very delicate and fine work can
be done.
•The process dimension repeatability, and surface finish obtained in
finishing are extremely good.
•The characteristics surface obtained, which is made up of crates,
helps in better oil retentions. This improves die life.
•Because the forces between the tool and the workpiece and
virtually zero, very delicate work can be done.

35. Disadvantages
1.Only electrically conductive materials can be machined by EDM.
Thus non - metallic, such as plastics, ceramics or glass, cannot be
machined by EDM.
2.Electrode wear and over-cut are serious problems.
3.A re-hardened, highly stressed zone is produced on the work
surface by the heat generated during machining. This brittle layer
can cause serious problems when the part is put into service.
4.Perfectly square corners cannot be made by EDM.
5.MRR is quite low.
6.High specific energy consumption ( about 50 times that in
conventional machining)

36. Applications
EDM can be used for machining any material that is electrically
conductive, thus including metals, alloys and mostcarbides.
EDM is widely used for machining burr free intricate shapes, narrow slots
and blind cavities etc., for example, sinking of dies for moulding, die
casting, plastic moulding, wire drawing, compacting, cold heading, forging,
extrusion and press tools.
EDM is particularly useful when dealing with internal cuts that are hard to
get tools into. Machining tends to work best with external cuts.
Almost any geometry (negative of tool geometry) can be generated on a
workpiece if a suitable tool can be fabricated (the use of punch as a tool to
machine its own mating die is commonly employed in EDM method).

37. The method is also employed for blanking parts from sheets,
cutting off rods of materials, flat or form grinding and sharpening
of tools, cutters and broaches.
In EDM method, small holes, about 0.13 mm, in diameter and as
deep as 20mm diameters can be drilled with virtually no bending
or drifting of hole. Due to this, EDM is particularly useful for
machining of small holes, orifices or slots in diesel-fuel injection
nozzles, or in aircraft engines, air brake valves and so on.
Application

38. Wire EDM
Wire EDM is a special form of EDM wherein the electrode is a
continuously moving conductive wire.
A thin wire of brass, tungsten, or copper is used as an electrode.
The electrode wire is typically made with a 0.05 to 0.25- mm diameter,
which is wire electrode wound between thetwo spools.
Deionised water is used as the dielectric.
This process is much faster than electrode EDM.
This process is widely used for the manufacture of punches, dies, and
stripper plates, with modern machines capable of cutting die relief,
intricate openings, tight radius contours, and corners routinely.

39. Geometrically accurate but moderately finished straight toothed
metallic spur gears, both external and internal type, can be produced by
wire type Electro discharge Machining (EDM).
Fig. :- wire EDM

40. Electric Discharge Grinding (EDG)
EDG is similar to EDM except that the electrode is a rotating
wheel (usually graphite).
Positively charged work pieces are immersed in or flooded by
a dielectric fluid and fed past the negatively charged wheel by
servo-controlled machine table.
Metal is removed by intermittent high frequency electrical
discharges passing through the gap between wheel and
workpiece.
Each spark discharge melts or vaporizes a small amount of
metal from the workpiece surface, producing a small crate at
the discharge sit, as in EDM.

41. Fig :- EDG Machine