Abrasive jet machining uses a high-velocity stream of abrasive particles suspended in a gas or liquid to erode material from a workpiece. It involves an abrasive delivery system, control system, pump, nozzle, mixing tube, and motion system to direct the abrasive jet. The abrasive particles impact the workpiece surface at high velocities and remove material primarily through brittle fracture or microcutting. Key factors that influence the material removal rate include abrasive type and size, jet velocity and pressure, stand-off distance, and impingement angle. Abrasive jet machining can precisely machine many materials and offers advantages like fast setup times and no heat affected zones.

1. ABRASIVE JET
MACHINING
Melbin K Mathew

2.  What is abrasive jet machining ?
It is the material removal process where the
material is removed by high velocity stream of
air/gas or water and abrasive mixture .
An abrasive is small, hard particle having sharp
edges and an irregular shape .
High velocity jet is aimed at a surface under
controller condition .

3.  components of abrasive jet
machining
Abrasive delivery system
Control system
Pump
Nozzle
Mixing tube
Motion system

4. 1.abrasive delivery system
Auto abrasive delivery system has the
capability of storing abrasive & delivery
the abrasive to the bucket . It’s works
auto programming system by help of
once measuring record & no adjustment
or fine tuning system . High sensitive
sensor gives extremely reliable &
repeatable .

5. 2.Control system
The control algorithm that computes exactly
how the feed rate should vary for a given
geometry in a given material to make a precise
part .
The algorithm actually
determines desired variation
in the feed rate & the tool
path to provide an extremely
smooth feed rate .

6. 3.pump
Crankshaft & intensifier pump are mainly use in
the abrasive jet machine .
The intensifier pump was the
only pump capable of reliably
creating pressures high .
Crankshaft pumps are more
efficient than intensifier pumps
because they do not require a power robbing
hydraulic system ultra high pressure & more
stroke per minute .

7. 4.nozzle
All abrasive jet systems use the same basic two
stage nozzle . First , water passes through a small
diameter jewel orifice to form a narrow jet .
The abrasive particles are
accelerated by the moving
stream of water & they pass
into a long hollow cylindrical
ceramic mixing tube.
Generally two type of nozzle
use , right angle head &
straight head .

8. NOZZLE

9. 5. Mixing tube
The mixing tube is where the abrasive mixes with
the high pressure water .
The mixing tube should be
replaced when tolerances
drop below acceptable levels .
For maximum accuracy ,
replace the mixing tube
more frequently .

10. Water Jet and Abrasive Water Jet Machining

WJM - Pure

WJM - with stabilizer

AWJM – entrained – three phase –
abrasive, water and air

AWJM – suspended – two phase –
abrasive and water
o Direct pumping
o Indirect pumping
o Bypass pumping

11. 6.Motion system
In order to make precision parts , an abrasive
jet system must have a precision x-y table and
motion control system .
Tables fall into three general categories .
Floor-mounted gantry systems
Integrated table/gantry systems
Floor-mounted cantilever systems

12.  working process
High pressure water starts at the pump , and is
delivered through special high pressure
plumbing to the nozzle .
At the nozzle , abrasive is introduced & as the
abrasive/water mixture exits , cutting is
performed .
Once the jet has exited the nozzle , the energy
is dissipated into the catch tank , which is
usually full of water & debris from previous
cut .

13. Water Jet and Abrasive Water Jet Machining

14. Components of AWJM
Catcher
(c) catcher plates (TiB2)
(b) steel/WC/ceramic balls
(a) water basin

15. Components of AWJM

16. Components of AWJM

17.  fig . schematic diagram of ajm

18. Abrasive Jet Machining

19.  ajm features
There are main features of AJM
Obtainable tolerances
Material to machine
Material thickness
Accuracy of table
Stability of table
Control abrasive jet

20.  Machine aspects
Around curves
Inside corner
Feed rate
Acceleration
Nozzle focus
Speed cutting
Pump pressure
Hardness & thickness
Software controlling the motion
Power at the nozzle

21.  Types of abrasive materials
Different types of abrasive are used in
abrasive jet machining like garnet ,
aluminum oxide , olivine , silica sand ,
silicon carbide ,etc .
Virtually any material can be cut by
using abrasive jet machining method ,
i.e harder
materials like titanium to steel.
Abrasive particles must be hard ,high
toughness,
irregular in shape & edges should be

22.  Advantages
Extremely fast setup & programming
No start hole required
There is only one tool
Low capital cost
Less vibration
No heat generated in work piece
Environmentally friendly

23. .
• Extremely fast set-up and programming
• Very little fixturing for most parts
• Machine virtually any 2D shape on any material
• Very low side forces during the machining
• Almost no heat generated on the part
• Machine thick plates
Advantages of AWJM

24.  Disadvantages
Low metal removal rate
Due to stay cutting accuracy is affected
Abrasive powder cannot be reused
Tapper is also a problem

25. Modelling
Photographic view of kerf (cross section)

26. General Experimental conditions
Orifice – Sapphires – 0.1 to 0.3 mm
Focussing Tube – WC – 0.8 to 2.4 mm
Pressure – 2500 to 4000 bar
Abrasive – garnet and olivine - #125 to #60
Abrasive flow - 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

27. Abrasive Jet Machining
Modelling of material removal
Material removal in AJM takes place due to brittle fracture of the
work material due to impact of high velocity abrasive particles.
Modelling has been done with the following assumptions:
(i) Abrasives are spherical in shape and rigid. The particles are
characterised by the mean grit diameter
(ii) The kinetic energy of the abrasives are fully utilised in
removing material
(iii) Brittle materials are considered to fail due to brittle fracture
and the fracture volume is considered to be hemispherical with
diameter equal to chordal length of the indentation
(iv) For ductile material, removal volume is assumed to be equal
to the indentation volume due to particulate impact.

28. Process Parameters and
Machining Characteristics
Abrasive : Material – Al2O3 / SiC / glass beads
Shape – irregular / spherical
Size – 10 ~ 50 μm
Mass flow rate – 2 ~ 20 gm/min
Carrier gas : Composition – Air, CO2, N2
Density – Air ~ 1.3 kg/m3
Velocity – 500 ~ 700 m/s
Pressure – 2 ~ 10 bar
Flow rate – 5 ~ 30 lpm
Abrasive Jet : Velocity – 100 ~ 300 m/s
Mixing ratio – mass flow ratio of abrasive to gas
Stand-off distance – 0.5 ~ 5 mm
Impingement Angle – 600
~ 900
Nozzle : Material – WC
Diameter – (Internal) 0.2 ~ 0.8 mm
Life – 10 ~ 300 hours

29. Abrasive Jet Machining
effect of process parameters on MRR

31. Abrasive Jet Machining
In AJM, generally, the abrasive particles of around 50 μm grit size
would impinge on the work material at velocity of 200 m/s from a
nozzle of I.D. of 0.5 mm with a stand off distance of around 2 mm.
The kinetic energy of the abrasive particles would be sufficient to
provide material removal due to brittle fracture of the work piece or
even micro cutting by the abrasives.

32. Abrasive Jet Machining
In Abrasive Jet Machining (AJM), abrasive particles are made to impinge
on the work material at a high velocity. The high velocity abrasive particles
remove the material by micro-cutting action as well as brittle fracture of the
work material.

33.  conclusion
The better performance , and the
applications represented above
statements confirm that
ABRASIVE JET MACHINING is
continue to expand .
The new software’s used to minimize
time and investments , there by making
it possible for more manufacturers of
precision parts to install AJM centers .