Abrasive jet machining

1. ABRASIVE JET MACHININGABRASIVE JET MACHINING
• An unconventional machining process.An unconventional machining process.
• It is the process of removal of materials by impactIt is the process of removal of materials by impact
erosion through the action of a concentrated, higherosion through the action of a concentrated, high
velocity of the grit abrasives entertained in a high-velocity of the grit abrasives entertained in a high-
velocity gas stream.velocity gas stream.

2. WHY ABRASIVE JET MACHINING ?WHY ABRASIVE JET MACHINING ?
• Since it is an unconventional machiningSince it is an unconventional machining
process, so it is used where conventionalprocess, so it is used where conventional
machining processes cannot be used, like inmachining processes cannot be used, like in
machining of hastalloy, nitralloy, nimonics,etc.machining of hastalloy, nitralloy, nimonics,etc.
• Also it differs from conventional sand blastingAlso it differs from conventional sand blasting
process for its fineness of particle size andprocess for its fineness of particle size and
controllable machining parameters.controllable machining parameters.

3. SCHEMATIC SET UP OF ABRASIVE JETSCHEMATIC SET UP OF ABRASIVE JET
MACHINING PROCESS:-MACHINING PROCESS:-

4. PROCESS DESCRIPTION:-PROCESS DESCRIPTION:-
• In this process, a gas (nitrogen or carbon dioxideIn this process, a gas (nitrogen or carbon dioxide
or air), is supplied under pressure (2-8kg/sq.cm) isor air), is supplied under pressure (2-8kg/sq.cm) is
supplied and after filter and regulator, it is passedsupplied and after filter and regulator, it is passed
to a mixing chamber (containing abrasiveto a mixing chamber (containing abrasive
particles) vibrating at 50c/sec.particles) vibrating at 50c/sec.
• From the mixing chamber , the gas along with theFrom the mixing chamber , the gas along with the
abrasive particles of size 10-50 micro-mt. passesabrasive particles of size 10-50 micro-mt. passes
on to a nozzle having its tip of tungsten carbideon to a nozzle having its tip of tungsten carbide
and diameter around 0.45mm , with a velocity ofand diameter around 0.45mm , with a velocity of
150-300m/sec.150-300m/sec.

5. • The air consumption is of the order of 0.6 cu-The air consumption is of the order of 0.6 cu-
m/hr.m/hr.
• The nozzle tip distance is of the order of 0.81mmThe nozzle tip distance is of the order of 0.81mm
• The abrasive powder feed rate is controlled by theThe abrasive powder feed rate is controlled by the
amplitude of vibration of the mixing chamber.amplitude of vibration of the mixing chamber.
• The relative motion between the nozzle and theThe relative motion between the nozzle and the
work piece is obtained by cams,pantographs towork piece is obtained by cams,pantographs to
control size and shape of cut.control size and shape of cut.
• Dust removal equipment is also incorporated toDust removal equipment is also incorporated to
protect the environment.protect the environment.

6. OPERATING PRINCIPLES IN ABRASIVEOPERATING PRINCIPLES IN ABRASIVE
JET MACHINING:-JET MACHINING:-
• Carrier gasCarrier gas
• Shape of cutShape of cut
• Nozzle designNozzle design
• Work materialWork material
• Type of abrasiveType of abrasive
• Stand-off distanceStand-off distance
• Size of abrasive grainSize of abrasive grain
• Velocity of abrasive jetsVelocity of abrasive jets
• Mean of abrasive particle/unit volume of the carrier gasMean of abrasive particle/unit volume of the carrier gas

7. EFFECT OF VARIOUS PARAMETERSEFFECT OF VARIOUS PARAMETERS
ON MATERIAL REMOVAL RATEON MATERIAL REMOVAL RATE

9. ABRASIVES USED IN ABRASIVEABRASIVES USED IN ABRASIVE
JET MACHININGJET MACHINING
ABRASIVESABRASIVES::
1.1. AluminaAlumina
2.2. Silicon carbideSilicon carbide
3.3. Sodium bicarbonateSodium bicarbonate
4.4. DolomiteDolomite
5.5. Glass beadsGlass beads
GRAINGRAIN
SIZE(micron)SIZE(micron)
10,27,5010,27,50
-do--do-
2727
6666
0.635-1.27mm0.635-1.27mm

10. CHARACTERISTICS OF THECHARACTERISTICS OF THE
PROCESS:-PROCESS:-
1.1. Size of abrasiveSize of abrasive Around 25 micro-mt.Around 25 micro-mt.
2.2. Flow rateFlow rate 3-20 g/min.3-20 g/min.
3.3. Life of nozzleLife of nozzle WC(12-30 hrs),sapphire(300 hrs).WC(12-30 hrs),sapphire(300 hrs).
4.4. ToleranceTolerance + or – 0.05mm+ or – 0.05mm
5.5. Surface roughnessSurface roughness 0.15-0.2 micro-m with particles of size 10micro-0.15-0.2 micro-m with particles of size 10micro-
m, 0.4-0.8 micro-m.m, 0.4-0.8 micro-m.
6.6. Work materialWork material Hard and brittle materials like glass, ceramics,Hard and brittle materials like glass, ceramics,
mica, etc.mica, etc.
7.7. Machining operationsMachining operations Drilling , cutting , deburring , cleaning.Drilling , cutting , deburring , cleaning.

11. APPLICATIONS OF THE PROCESS:-APPLICATIONS OF THE PROCESS:-
• Used for abrading and frosting glass moreUsed for abrading and frosting glass more
economically as compared to etching or grinding.economically as compared to etching or grinding.
• For cleaning of metallic smears on ceramics, oxidesFor cleaning of metallic smears on ceramics, oxides
on metals, resistive coatings, etc.on metals, resistive coatings, etc.
• Cutting and machining of fragile material like Ge, Si,Cutting and machining of fragile material like Ge, Si,
etc.etc.
• For deburring small hole in hypodermic needles andFor deburring small hole in hypodermic needles and
for small milled slots in hard metallic components.for small milled slots in hard metallic components.
• Register treaming can be done very easily and micro-Register treaming can be done very easily and micro-
module fabrication for electrical contact,module fabrication for electrical contact,
semiconductor processing can also be donesemiconductor processing can also be done
effectively.effectively.

12. ADVANTAGES OF THE PROCESS:-ADVANTAGES OF THE PROCESS:-
• Ability to cut fragile, brittle or heat sensitiveAbility to cut fragile, brittle or heat sensitive
material without damage.material without damage.
• Ability to cut intricate holes in materials ofAbility to cut intricate holes in materials of
any hardness.any hardness.
• Low capital cost.Low capital cost.
• Can cut materials without damage becauseCan cut materials without damage because
there is no heating of the working surface.there is no heating of the working surface.

13. DISADVANTAGES OF THEDISADVANTAGES OF THE
PROCESSPROCESS
• Slow material removal rate.Slow material removal rate.
• Low accuracy (0.1mm) due to strayLow accuracy (0.1mm) due to stray
cutting.cutting.
• Abrasives get embedded on theAbrasives get embedded on the
material surface, if it is soft.material surface, if it is soft.
• Abrasives powder cannot be refused.Abrasives powder cannot be refused.

14. FUTURE PROSPECTS OF THEFUTURE PROSPECTS OF THE
PROCESSPROCESS
• This process can be used in future in thoseThis process can be used in future in those
places where there is intricacy and costlyplaces where there is intricacy and costly
machining, so this process can be used tomachining, so this process can be used to
remove both of these difficulties.remove both of these difficulties.
• Also, due to cost-effectiveness of the set ofAlso, due to cost-effectiveness of the set of
AJM, this process can be used in small-scaleAJM, this process can be used in small-scale
industries.industries.

15. REFERENCESREFERENCES
• Production technology- R.K.JainProduction technology- R.K.Jain
• Non-conventional machining- P.K.MishraNon-conventional machining- P.K.Mishra
• GoogleGoogle
• WikipediaWikipedia