MECHANICAL BASED ENERGY PROCESS

ME2026 UNCONVENTIONAL MACHINING
PROCESSES
UNIT 2
MECHANICAL ENERGY BASED PROCESS
By
G.NANTHINI,
LECTURER,
DEPT OF MECHANICAL,
KRCE, Trichy.

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.

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

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

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

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

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

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.

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

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

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.

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.

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.

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

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.

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

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.

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).

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

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

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

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.

USM Applications
 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

MECHANICAL BASED ENERGY PROCESS

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