1. UNIT I
UNIT I INTRODUCTION AND MECHANICAL ENERGY
BASED PROCESSES
Unconventional machining Process – Need – classification – merits,
demerits and applications. Abrasive Jet Machining – Water Jet
Machining – Abrasive Water Jet Machining - Ultrasonic Machining.
(AJM, WJM, AWJM and USM). Working Principles – equipment
used – Process parameters – MRR- Applications.
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.
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.
15. 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
16. 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
17. 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
18. 19
Thermal Based Processes
1. Working principles
2. Equipment used
3. Types
4. Beam control techniques
5. Applications
LBM
PAM
EBM
19. Selection Process
• Selection Process is based of following
parameters
– Physical Parameter
– Shapes to be Machined
– Process Capability
– Economic consideration
20. 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 Nitrogen
Abrasive
grains
Work
Material
M/C diff Tungsten
carbide
All Mtl All Mtl All Mtl Tungsten HSS
carbide
23. 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
26. 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.
27. 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
31. 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)
33. ADVANTAGES
Low capital cost
Less vibration
No heat generated in the work piece
Eco friendly
Only one tool is required
34. DISADVANTAGES
Low metal removal rate
Abrasive powder can not be reused
The machining accuracy is poor
Nozzle wear rate is high
35. Water Jet Machining
Principle
In WJM, the high velocity of water jet
comes out of the nozzle and strikes the material, its
pressure energy is converted into kinetic 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.
38. 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
39. Advantages of water jet cutting
There is no heat generated in water jet cutting; which
is especially useful for cutting tool steel 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
40. 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.
41. 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.
42. 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.
45. 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
46. 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.
47. Disadvantages of Abrasive water jet cutting
Cannot drill flat bottom
Cannot cut materials that degrades quickly with
moisture
48. 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.
49. 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).
52. 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
53. CONTD…
EFFECT `VELOCITY`
MRR is Directly Proportional to the Particle Velocity
M
R
R
Feed force
Mean grain
diameter
Surface
rough
54. CONTD..
EFFECT OF STATIC LOADING OR
FEED FORCE:
- MRR increases with an increase in feed
force.
EFFECT OF GRAIN SIZE:
- Grain size increases with an increase in
MRR
55. 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.
56. USMApplications
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
Hard, brittle work materials such as ceramics, glass,
and carbides.
