This document provides an overview of abrasive water jet machining (AWJM). It begins with an introduction that defines AWJM as a non-traditional machining process that uses the mechanical energy of water and abrasives for material removal. The working principle and basic mechanism of material removal are then described. Key aspects of AWJM equipment and processes are discussed, including the pumping system, abrasive feed system, nozzle, process parameters like water pressure and abrasive flow rate, and applications of the technique. Advantages include the ability to machine many materials without thermal damage but disadvantages include relatively low machining speeds.

1. PRESENTED BY :
P.AKHIL KUMAR
ABRASSIVE WATER JET MACHENING

2. CONTENTS
• INTRODUCTION
• WORKING PRINCIPLE
• BASIC MECHANISM OF METAL REMOVAL
• PROCESS PRINCIPLE
• APPROACHES
• EQUIPMENT DESCRIPTION
• CUTTING GEOMETRY
• PROCESS PARAMETERS
• PROCESS CAPABILITIES
• ADVANTAGES & DIS -ADVANTAGES
• APPLICATIONS
• AWJM vs. OTHER MODERN PROCESS
• COCLUSION

3. • Abrasive Water Jet Machining (AWJM) is non-
traditional or non-conventional machining
process.
• In these processes , the mechanical energy of
water and abrasive phases are used to achieve
material removal or machining.
• Abrasive water jet machining – Developed in
1974 to clean metal prior to surface treatment of
the metal.
INTRODUCTION

4. WORKING PRINCIPLE OF AWJM
• The cutter is commonly
connected to a high pressure
water pump where the water
is then ejected from the
nozzle, cutting through the
material by spraying it with
the jet of high speed water.
• Additives in the form of
suspended grit or other
abrasives, such as garnet and
aluminum oxide can assist in
this process.

5. BASIC MECHANISM OF MATERIAL REMOVAL

6. Process Principle
• An abrasive jet starts out the same as a pure
water jet.
• As the thin stream of water leaves the nozzle,
abrasive is added to the stream and mixed.
• The beam of water accelerates abrasive particles
to speeds fast enough to cut through much
harder materials.
• Silicon carbides, sand (SiO2), corundum, and glass
beads of grain size 10 to 150 μm are often used
as abrasive materials.

7. Process Principle
• The mixing of abrasive particles in water jet is in
such a manner that water jet’s momentum is
transferred to the abrasives.
• The coherent, abrasive water jet that exits the
AWJM nozzle has the ability to cut various
materials, such as metals, glass, ceramics and
composites.
• Generally, AWJM cuts 10 times faster than the
conventional machining methods of composite
materials.

8. APPROACHES
Different approaches IN AWJM
• AWJM – entrained – three phase (water + air +
abrasives)
• AWJM – suspended – two phase (water + abrasives)
• Direct pumping
• Indirect pumping
• Bypass pumping

9. APPROACHES

10. Schematic Setup of AWJM

11. Schematic Setup of AWJM

12. EQUIPMENT DESCRIPTION

13. EQUIPMENT DESCRIPTION

14. EQUIPMENT DESCRIPTION
• Pumping system :Identical as WJM
• Abrasive Feed System:
Purpose: Controlled flow of abrasive particles
to the abrasive jet nozzle.
AWJM abrasive feed systems deliver a stream
of dry abrasives to the nozzle.
Drawback with dry abrasive delivery systems
is that the delivery of abrasives over long
distances is difficult.

15. EQUIPMENT DESCRIPTION
Typical work materials involve soft metals, paper, cloth, wood,
leather, rubber, plastics, and frozen food. If the work material
is brittle it will fracture, if it is ductile, it will cut well .
Abrasive Water jet Machining consists of:
1. Hydraulic Pump
2. Intensifier
3. Accumulator
4. High Pressure Tubing
5. Jet Cutting Nozzle
6. Catcher

16. HYDRAULIC PUMP
• Powered from a 30 kilowatt (kW) electric motor
• Supplies oil at pressures as high as 117 bars.
• Compressed oil drives a reciprocating plunger pump termed
an intensifier.
• The hydraulic pump offers complete flexibility for water jet
cutting and cleaning applications.
• It also supports single or multiple cutting stations for
increased machining productivity.

17. INTENSIFIER
• Intensifier – driven by a hydraulic power pack.
• Heart of hydraulic power pack is a positive displacement
hydraulic pump.
• The power packs in modern commercial systems are often
controlled by microcomputers to achieve programmed rise
of pressure, etc.

18. INTENSIFIER
• Hydraulic power pack – delivers hydraulic oil at a pressure ph
to Intensifier.
• CONDITIONS:
Ratio of cross-section of the two cylinders, A ratio =A large /A small
Thus, pressure amplification at the small cylinder takes place
as follows:
Thus, if the hydraulic pressure is set as 100 bar and area ratio
is 40, pw = 100 x 40 = 4000 bar.

19. INTENSIFIER
• By using direction control valve, the intensifier is driven by
the hydraulic unit.
• The water may be directly supplied to the small cylinder
of the intensifier, Or it may be supplied through a booster
pump, which typically raises the water pressure to 11 bar
before the intensifier.
• Sometimes water is softened or long chain polymers are
added in “additive unit”.
• Thus, as the intensifier works, it delivers high pressure
water.

20. ACCUMULATOR
• As the larger piston changes direction within the intensifier,
there would be a drop in the delivery pressure
• To counter such drops, a thick cylinder is added to the
delivery unit to accommodate water at high pressure which is
called as “Accumulator”.
• Maintains the continuous flow of the high-pressure water
and eliminates pressure fluctuations.
• It relies on the compressibility of water (12 percent at 3800
bar) in order to maintain a uniform discharge pressure and
water jet velocity, when the intensifier piston changes its
direction.

21. HIGH PRESSURE TUBING
• Transports pressurized water to the cutting head.
• Typical tube diameters are 6 to 14 mm.
• The equipment allows for flexible movement of the cutting
head.
• The cutting action is controlled either manually or through a
remote-control valve specially designed for this purpose.

22. Injection & Suspension Heads

23. JET CUTTING NOZZLE
Purpose of the abrasive
jet nozzle is to provide
efficient mixing of the
abrasives and the water
jet and to form the high-
velocity abrasive water-jet
combination

24. JET CUTTING NOZZLE
There is a difference between a pure
water nozzle and an abrasive jet nozzle.
With the abrasive jet nozzle, an opening
in the side of the nozzle allows for the
introduction of the abrasive to the high-
pressure water stream. The two are
mixed in a mixing tube and then exit the
nozzle. With a pure water jet nozzle,
there is no opening and no mixing tube
and the high-pressure water is directed
to the material after it exits the jewel.

25. 25
Mixing Chamber
• Abrasive particles during mixing try to enter the jet, but they are
reflected away due to interplay of buoyancy and drag force.
• They go on interacting with the jet and the inner walls of the
mixing tube, until they are accelerated using the momentum of
the water jet.
• In entrained AWJM, the abrasive water jet, which finally comes
from the focussing tube or nozzle, can be used to machine
different materials.

26. ABRASSIVE MOVEMENT

27. WORKPIECE CUTTING

28. bt Jet affected
zone
Jet affected zone
burr
Outer dia
Inner dia
CUTTING GEOMETRY
TOP VIEW BOTTOM VEIW
Rough surface

29. Cutting Geometry
Stand off diameter

30. Cutting Geometry

31. EFFECT OF FEED RATE

32. EFFFECT OF FEED RATE

33. ROUGHNESS

34. • To minimize abrasive wear, the nozzle is
usually made from either tungsten carbide or
boron carbide.
• Two major design concepts are currently used
for the design of abrasive jet nozzles.
• They are :
Single-jet side feed nozzle
Multiple jet feed nozzle
JET CUTTING NOZZLE

35. JET CUTTING NOZZLE
• Single-jet side feed nozzle
• This design is based on a central
water jet with abrasives fed into
the mixing chamber from the side.
• This configuration is easily
machined and can be made quite
small, which is an advantage when
cutting in tight locations.
• But this concept does not provide
for optimal mixing efficiency and
usually experiences rapid wear of
the exit section.
• The major advantage with this
system is this that, it incorporates a
central, conventional water jet, the
abrasive flow can be stopped and
the system will function as a
conventional WJM system.

36. JET CUTTING NOZZLE
• Multi jet feed nozzle :
While cutting the same type
of material, one can choose
the nozzle that works best
for that material.
This type of nozzle is used
for cutting materials like
Hardened tool steel,
Titanium, Aluminium,Hard
Rubber,Stone ,Inconel , mild
steel ,Stainless Steel

37. JET CUTTING NOZZLE
• Limitations of abrasive jet nozzles
Despite their simple design, abrasive jet
nozzles can be troublesome at times. There
are many designs, but they share the same
problems which are listed below.
• Short life of the mixing tube
• Occasional plugging of mixing tube
• Wear, misalignment, and damage to the jewel

38. CATCHER
• “Catcher” is used to absorb the residual energy of the AWJ
and dissipate the same.
• Acts as a reservoir for collecting the machining debris
entrained in the water jet.
• Moreover, it reduces the noise levels [105 decibels (dB)]
associated with the reduction in the velocity of the water
jet from Mach 3 to subsonic levels
• Catcher is of two types
(a)Pocket type: The catcher basin travels along the jet
(along X&Y) .
(b)Line type :The catcher basin travels along one axis and
its length covers the entire width of the other
axis of the CNC table.

39. 39
CATCHER

40. PROCESS PARAMETERS

41. WATER JET PRESSURE:
• Pc is the minimum
critical pressure required
to cut the material.
• A minimum critical
pressure Pc exits because
of the minimum abrasive
particle velocity
required to cut specific
materials.
PROCESS PARAMETERS

42. PROCESS PARAMETERS
• fig. Shows the depth of cut is
affected by varying the water flow
rate (increasing the nozzle
diameter) while maintaining the
constant pressure.
• As the flow rate increases, the
slope of the curve decreases
because the saturation point is
reached.
• As the nozzle diameter increases
and the water flow rate increases,
the rate of increase in the particle
velocity is reduced, thus reducing
the depth of cut.
WATER FLOW RATE
& NOZZLE DIA

43. PROCESS PARAMETERS
Abrasive flow rate:
• Abrasive flow rate versus depth of cut is a
linear relationship up to a point
• Above a critical flow rate, the cutting
efficiency decreases.
• This is because of the fact that, as the abrasive
flow rate increases( with a fixed water flow
rate), particle velocity begins to decrease
faster than the rate at which the number of
abrasive particle impacts increase.

44. PROCESS PARAMETERS
Abrasive Particle Size:
• The most common abrasive particle sizes used
for AWJM range from 100 to 150 grit
• An optimum abrasive particle size also exists
for each particular nozzle mixing chamber
configuration.

45. PROCESS PARAMETERS
Abrasive Type:
• The type of abrasive used is also an important
parameter.
• Garnet(30% more efficient than sand), silica
and silicon carbide are the most commonly
used abrasives.
• Selection of abrasive type is usually
determined by the hardness of the material
that is being cut.

46. PROCESS PARAMETERS
Abrasive Type:
• Steels & Non-ferrous alloys
• Ti alloys, Ni- alloys
• Polymers
• Honeycombs
• Metal Matrix Composite &
Ceramic Matrix Composite
• Concrete
• Stone – Granite
• Wood
• Reinforced plastics
• Metal Polymer Laminates
• Glass Fibre Metal Laminates

47. PROCESS PARAMETERS
Traverse Rate:
• When traverse rates are increased the depth
of cut decreases.
• There is also a minimum critical traverse rate
below which further increases in depth of cut
are not obtained.
• If the traverse rate is not maintained at a
relatively uniform velocity, a rough edge will
result because of the nature of the process.

48. PROCESS PARAMETERS
Stand-off-Distance:
• Data generated by some researchers indicate that
depth of cut is approximately linear relative to
SOD.
• Increasing SOD decreasing the depth of cut.
• When mixing is efficient and process parameters
are correct, a deviation in SOD of up to +-12.7mm
can be tolerated without degradation of the cut
quality.
• If SODs are increased to a distances of about
80mm, the process will no longer cut but will
efficiently clean and de-scale surfaces.

49. PROCESS PARAMETERS
Surface Roughness:
• Surface roughness depends on the workpiece material,
grit size, and type of abrasives.
• A material with a high removal rate produces large surface
roughness.
• Fine grains are used for machining soft metals to achieve
better roughness
• The decrease in surface roughness by using smaller grain
size is related to the reduced depth of cut and the
undeformed chip cross section.

50. PROCESS PARAMETERS
Surface Roughness:
• A carrier liquid consisting of water with anticorrosive
additives has higher density and contributes to higher
acceleration of the grains.
• This results in higher grain speed and increased metal
removal rate. Moreover, the carrier liquid spreads over the
surface filling its cavities and forming a film that impedes
the striking action of the grains.
• Therefore, peaks in the surface irregularities are the first to
be affected and the surface quality improves.

51. Typical Parameters in Entrained AWJM
 Orifice – 0.1 to 0.3 mm
 Focussing Tube– 0.8 to 2.4 mm
 Pressure – 2500 to 4000 bar
 Abrasive – garnet and olivine - 125 to 60 micron
 Abrasive flow rate - 0.1 to 1.0 kg/min
 Stand off distance – 1 to 2 mm
 Machine Impact Angle – 60o to 900
 Traverse Speed – 100 mm/min to 5 m/min
 Depth of Cut – 1 mm to 250 mm

52. PROCESS CAPABILITIES
• AWJM can be thought of as a combination of WJM and
AJM principles.
• But in terms of capability, AWJM combines the best of
both processes, resulting in a new process that can cut
materials whether they are hard or soft at high rates and
in very thick sections.
• AWJM can cut materials as thick as 200mm and still
maintain a comparatively narrow kerf.
• Kerf width is a function of the material thickness and
usually is between 1.5 and 2.3mm.

53. PROCESS CAPABILITIES
• The resulting taper on the cut edge is a function of
the material hardness.
• Where hard materials have the widest kerf at the top
of the cut and
• Soft materials have the widest kerf at the bottom of
the cut.

54. Advantages
19-01-2017
• Cut virtually any material.
• Cut thin or thick stuff.
• Make all sorts of shapes with only one tool
• No heat generated.
• Leaves a smooth finish, thus reducing
secondary operations.
• Modern systems are now very easy to learn and safe.
•Unlike machining or grinding, cutting does not
produce any dust or particles that are harmful if
inhaled.
• Abrasive Water jet cutting can be easily used to
produce prototype parts very efficiently
This part is shaped with waterjet
using one tool. Slots, radii, holes,
and profile in one 2 minute setup.

55. DISADVANTAGES
• COST
• DIMENSIONAL ACCURACY

56. APPLICATIONS
• Paint removal
• Cleaning
• Cutting soft materials
• Cutting frozen meat
• Textile, Leather industry
• Peening
• Pocket Milling
• Drilling & Turning
• Nuclear Plant Dismantling

57. AWJM vs. OTHER MODERN PROCESS
19-01-2017 57
After laser cutting After Abrasive waterjet cutting Abrasive Water jets are much
faster than EDM.
After plasma cutting After waterjet cutting

58. CONCLUSION
• In technical field technology plasma arc , laser
welding e.t.c has been huge success due to
their flexibility and adaptability.
• AWJ has also attracted the vision of
entrepreneur by their capabilities.
• Advanced AWJ machines are now available
where the computer loads a CAD drawing
from another system which increasing its eco-
friendly .