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1802111055 SEMINAR REPORT-converted-converted

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SEMINAR REPORT
On
ABRASIVE JET MACHINING
submitted to Veer Surendra Sai University of Technology in partial fulfillment of
the requirements for the award of the degree of
Bachelor of Technology
In
Production Engineering
Submitted by :SUBHASISH HARSH-1802111055
Facilitator:
Dr. Sudhansu Ranjan Das
DEPARTMENT OF PRODUCTION ENGINEERING
VEER SURENDRA SAI UNIVERSITY OF TECHNOLOGY BURLA
ODISHA
APRIL 2022
व ीी स ीर ीी ीीी स ीी ीीीीीीीीग ीीी ग व ीीी
ग व ीीीील य ब ील ीी, ीीीश ी
उ ततप तद न अ भतततततभ ततत भ तततत
Veer Surendra Sai University of Technology Burla, Odisha
Department of Production Engineering
P.O: Engineering College Burla (Siddhi Vihar), Dist: Sambalpur, Odisha –
768018, India. Website : www.vssut.ac.in, E-mail: head_prod@vssut.ac.in
CERTIFICATE
This is to certify that the seminar report entitled “ABRASIVE JET MACHINING” submitted
by Subhasish Harsh (1802111055), in the partial fulfillment of the requirement for the award of
the degree of Bachelor of Technology from the Department of Production Engineering, Veer
Surendra Sai University of Technology, is a record of candidate’s own work carried out by him.
The matter embodied in this report has not been submitted in part or full to any other university or
institute for the award of any degree.
This is to certify that the above statement made by the candidate is correct to the best
of my knowledge.
Approved by:
Dr. Sudhansu Ranjan Das
(Facilitator)
Dr. Kamal Pal
(Head Of Dept.)
Associate Professor
DoPE, VSSUT Burla
Associate Professor
DoPE, VSSUT Burla
DECLARATION OF ACADEMIC INTEGRITY
I, Subhasish Harsh (1802111055) students of B. Tech (Semester-VIII) of Veer Surendra Sai
University of Technology Burla, Odisha hereby declare that the seminar report entitled
“Abrasive Jet Machining” is an original work and data provided in the study is authentic to
the best of my knowledge. This report has not been submitted to any other Institute for the
award of any other degree.
Date: 05/04/2022
Place: Burla
Subhasish Harsh
Roll no.- 1802111055
ACKNOWLEDGEMENT
It is my pleasure to be indebted to various people, who directly or indirectly
contributed in the development of this work and who influenced my thinking, behavior and
acts during the course of study.
I am thankful to Dr. Sudhansu Ranjan Das for his support, cooperation, and
motivation provided to me during the seminar for constant inspiration, presence and blessings.
I also extent my sincere appreciation to the faculties of my department who
provided their valuable suggestions and precious time in accomplishing my Seminar report.
Lastly, I would like to thank the almighty and my parents for their moral support
and my friends with whom I have shared our day-to-day experience and received lots of
suggestions about my quality of work.
Subhasish Harsh (180211055)
Table of Contents
SL. NO.
TOPICS
PAGE NO.
1
Abrasive jet machining: Abstract
6
2
Introduction
6-7
3
Equipment
7-8
4
Operating Principle
8-9
5
Mechanism of material removal
6
Abrasives
9-10
7
Process Parameter Influence MRR
10-13
8
Benefits
13-14
9
Limitations
14
10
Application
14-15
11
Conclusion
15
12
Reference
16
9
ABSTRACT:Abrasive jet machining is one of the mechanical type non-conventional machining. This
process used to cut hard and brittle material like glass, mica, germanium etc. Here the operating
elements are carrier gas, nozzle and abrasives. Here material removal takes place by an impact
erosion through a concentrated stream of grit abrasives in high velocity gas stream. The
equipment consists of gas supply unit, pressure regulator, filter, mixing chamber, dust
collecting device according with the work-holding device. Here carrier gas comes out from
compressor needs to be dry and filtered for removal of unnecessary contamination. Then
abrasive grits are allowed to flow with the gas stream where mixing ratio is controlled by
vibrator. Then the gas and abrasive mixture enters into the machining chamber and comes out
from nozzle hence machining will done. Here the accuracy of cut area depends upon the
standoff distance from work piece. AJM has become a useful technique for micro machining.
It has various distinct advantages over the other non-traditional cutting methods, which are
high machining versatility, minimum stresses on the substrate. This paper deals with several
experiments that have been conducted by many researchers to assess the influence of abrasive
jet machining (AJM) process parameters such as type of abrasive Particle , Abrasive Particle
size, Jet pressure Nozzle tip distance. Various experiments were conducted to assess the
influence of abrasive jet machine.
INTRODUCTION:In Non-traditional machining process different forms of energies are directly supplied to the
work piece for material removal. Here material removal takes place without chip formation, if
chip formation takes place in some cases then that would be of microscopic size. Most of the
non-traditional machining do not require any physical contact between tool and work piece.
These processes are not affected by hardness, toughness or brittleness of material and can
produce any intricate shape on any material by suitable control over various process parameters
of the process. Here the basic mechanisms for material removal are impact erosion, ionic
dissolution, and vaporization while source of immediate energy required for material removal
are hydrostatic pressure, high current density, high voltage, ionized material etc.
These can be classified according to the source of energy used to generate such a machining
action: mechanical, thermal, chemical and electrochemical.
Abrasive Jet Machining (AJM), or in other words Abrasive jet cutting, is a mechanically
advanced unconventional machining process where abrasives having a very high velocity is
used to erode away small portions of materials from the work piece surface. AJM was initially
used for cutting soft materials, in early 70s. Softer materials like wood, plastic and rubber were
cut using this technique. It does not encounter any vibration problems. However, in order to
machine hard materials like metals and granite, another machining process called Abrasive Jet
Machining (AJM) was developed.
ABRASIVE JET MACHINING:
In AJM, the material removal takes place due to impingement of the fine abrasive particles. It
can be used to cut hard and brittle material such as germanium, silicon, mica, glass and ceramic
in a high velocity cutting and deburring action. This process is smooth and free from vibration.
EQUIPMENT:The machine tool of abrasive jet machine consists of gas supply unit, filter, pressure gauge,
mixing chamber, nozzle and dust collecting chamber along with the work holding device.
Gas supply :
The filtered gas, supplied under a pressure of 2 to 8 kgf/cm to the mixing chamber containing
the abrasive powder and vibrating at 50 Hz entrains the abrasive particles and is then passed
into a connecting hose. This abrasive and gas mixture emerges from a small nozzle mounted
on a fixture at a high velocity ranging from 150 to 300 m/min.
Filter:
The filter is used to clean the fuel supply so that dirt or other impurities do not hamper the
progress of the process.
Pressure gauge:
It is used to control the pressure of the compressed used in the abrasive jet machining. As the
pressure decides the depth of cutting and the amount of force required for cutting.
Mixing Chamber:
In the mixing chamber, abrasive powder is being fed and with the help of a vibrator amount of
abrasives can be controlled. So that the abrasives and the gases will be mixed thoroughly in the
mixing chamber.
Nozzle:
The nozzle is used to increase the velocity of the fine abrasive jet slurry at the expense of the
pressure, as we know if we decrease the pressure, the velocity will increase. The material of
the nozzle should be able to withstand corrosion. The nozzle is made of either circular or
rectangular cross-sections and the head can be straight or at a right angle.
Nozzle material:
For aluminium oxide (Al2O3) abrasive: Tungsten Carbide (WC) nozzle
For Silicon Carbide (SiC) abrasive: sapphire nozzle
Where hardness of tungsten carbide (WC) < Hardness of sapphire
Life of nozzle varies between (12hrs-30hrs) and standoff distance varies between (0.25-7.5)
mm.
Machining Chamber:
It is well closed so that concentration of abrasive particles around the working chamber does
not reach to the harmful limits. Machining chamber is equipped with vacuum dust collector.
Special consideration should be given to dust collection system if the toxic material (like
beryllium) are being machined.
OPERATING PRINCIPLE
Here the material removal rate is governed by mass flow rate and velocity of the abrasive
particles uniquely related to gas mass flow rate. The jet coming of the nozzle remains straight
for some time then flares out, so the accuracy of the cut area depends upon the nozzle tip
distance from the work piece.
Here carrier gas from nozzle needs to be dried for removal of water/ oil vapor. Then filtering
is done for removal of unnecessary contamination. The abrasive is allowed to flow into the gas
stream where the mixing ratio is generally controlled by vibrator. The mass flow rate of
abrasive entering into the mixing chamber depends upon amplitude and frequency of vibration
of shaker and hence the sieve.
Then the particle and gas mixture comes out of the nozzle inside the machining chamber of the
machine tool unit. Here feed motion can be given either to the work-holding device or to nozzle.
Here operating elements are carrier gas, abrasive and nozzle.
The variables that affect the cutting phenomena are abrasive, carrier gas and nozzle, where in
abrasive we have to consider its composition, strength, shape, size and mass flow
rate.Simillarly in carrier gas: composition, pressure and velocity and for nozzle: geometry,
composition and standoff distance respectively.
MECHANISM OF MATERIAL REMOVAL:
Here material removal takes place by impact erosion through the action of a concentrated high
velocity stream of the grit abrasive in a high velocity gas stream. So the kinetic energy of the
particle is utilized to cause micro indentation in the work material and the material removal is
a major of indentation.
ABRASIVES:
Aluminum oxide (Al2O3 ) ,Silicon carbide (SiC) ,Glass beads, crushed glass and sodium
bicarbonate are some of abrasives used in AJM. Selection of abrasives depends on MRR, type
of work material, machining accuracy. Silicon carbide is used as a loose or solid abrasive
material in a variety of applications Due to its high abrasion resistance and relatively low cost.
Synthetic silicon carbide is the hardest abrasive blasting media in use today. Silicon carbide
offers the benefit of an extremely fast cutting speed, which, when combined with its hardness,
allows for much shorter blasting times. This results in a lower per-hour cost than most other
abrasive media types. The abrasive particles are considered rigid and spherical bodies of
diameter equal to the average grit size. These abrasives are used in AJM are non-circulating as
their effectiveness reduce a lot within one cycle.
Aluminium oxide (Al2O3)
Silicon carbide (SiC)
PROCESS PARAMETER INFLUENCES (MRR):
Parameters of Abrasive Jet Machining (AJM) are factors that influence its Metal Removal Rate
(MRR). In a machining process, Metal Removal Rate (MRR) is the volume of metal removed
from a given work piece in unit time. The following are some of the important process
parameters of abrasive jet machining:
1. Abrasive mass flow rate
2. Nozzle tip distance
3. Gas Pressure
4. Velocity of abrasive particles
5. Mixing ratio
6. Abrasive grain size
Abrasive mass flow rate:
Mass flow rate of the abrasive particles is a major process parameter that influences the metal
removal rate in abrasive jet machining. In AJM mass flow rate of the gas (or air) in abrasive
jet is inversely proportional to the mass flow rate of the abrasive particles. Use to this fact,
when continuously increasing the abrasive mass flow rate, Metal Removal Rate (MRR) first
increases to an optimum value (because of increase in number of abrasive particles hitting the
work piece) and then decreases. However, if the mixing ratio is kept constant, Metal Removal
Rate (MRR) uniformly increases with increase in abrasive mass flow rate.
Nozzle tip distance:
Nozzle Tip Distance (NTD) is the gap provided between the nozzle tip and the work piece. As
the standoff distance is increased, the initially MRR increases due to increase in velocity as the
abrasives get enough time to gain velocity before collision. But as the standoff distance further
increases then atmospheric resistance checks on the kinetic energy of the abrasives and through
the velocity and hence kinetic energy tend to increase the atmospheric drag keeps checking on
and the impact energy remains almost constant and hence a constant MRR is maintained for
increasing standoff distance. After which the atmospheric resistance start to dominate the
kinetic energy of abrasive and hence further increase in standoff distance results in decreasing
MRR.
Gas pressure:
Gas pressure has a direct impact on metal removal rate. In abrasive jet, machining, metal
removal rate is directly proportional to air or gas pressure.
Velocity of abrasive particles:
Whenever the velocity of abrasive particles is increased, the speed at which the abrasive
particles hit the work piece is increased. Because of this reason, in abrasive jet machining,
metal removal rate increases with increase in velocity of abrasive particles.
Here velocity effects are more predominant than mass flow rate on material removal rate.
Under lower velocity condition ductile material show lower material removal, rate for an angle
of impingement 90 degree than brittle materials. However, at certain velocity U*, both material
may exhibit similar property for impact erosion rate and above this velocity; ductile materials
may erode very fast.
Mixing ratio:
Mixing ratio is a ratio that determines the quality of the air-abrasive mixture in Abrasive Jet
Machining (AJM). It is the ratio between the mass flow rate of abrasive particles and the mass
flow rate of air (or gas). When mixing ratio is increased continuously, metal removal rate first
increases to some extent and then decreases.
Abrasive grain size:
Size of the abrasive particle determines the speed at which metal is removed. If smooth and
fine surface finish is to be obtained, abrasive particle with small grain size is used. If metal has
to be removed rapidly, abrasive particle with large grain size is used.
BENEFITS:
1. This method facilitates to machine the complex holes and intricate cavities of harder
materials of desired shape.
2. The fragile metals, which are very difficult to machine in the conventional machining
process, are easily machined by this process with better accuracy.
3. Machining can be performed easily for brittle type of materials of thin sections.
4. Capital investment if very low.
5. No direct contact occurs between the work piece and the tool.
6. Heat generated in this process is very less.
LIMITATION:

Less capacity of the process due to low Material removal rate.

While machining soft material abrasive gets embedded which will decrease its surface
finish.

The accuracy of cutting is disturbed by the tapering of the hole due to the unavoidable
variation of an abrasive jet.

Accuracy is not good due to stray cutting.

A dust collection system is a basic requirement to prevent atmospheric pollution and health
hazards so the extra cost will be there.

Nozzle life is limited (300 hours).

Abrasive powders cannot be reused as the sharp edges are worn and smaller particles can
jam the nozzle.

A small standoff distance can damage the nozzle.

The process accuracy is poor because of the flaring effect of the abrasive jet.

Deep holes will have a taper.

AJM Process is not environment-friendly and causes pollution.

Airborne abrasives can cause a hazardous atmosphere.
APPLICATION:

It is used for abrading and frosting glass, ceramics, and refractories and it is more
economical as compared to etching or grinding.

Cleaning of layering of metals like resistive coating.

Deflating small castings and trimming of parting lines of injection moulded parts and
forgings.

It is used for engraving registration numbers on toughened glass for car windows.

AJM is used for cutting thin fragile components like germanium, silicon, quartz, mica, etc.

Abrasive jet machining is used effectively for micro module fabrication.

Deburring etching, drilling, Cutting, and polishing of hard and brittle materials.

It can be used for micromachining of brittle materials.

It is used in fine drilling and aperture drilling for an electronic microscope.

Used for cleaning metallic moulds and cavities.

Cleaning surfaces from corrosion, paints, glues, and other contaminants.

Deburring of surgical needles and hydraulic valves, nylon, Teflon, and Delran.

Engraving on glass using rubber or metallic masks.
CONCLUSION:
AJM process is receiving more and more attention in the machining areas, particularly for the
processing of difficult-to-cut materials. Its unique advantages over other conventional and unconventional methods make it a new choice in the machining industry. Various materials can
be machined using this process. Efficiency of Abrasive Jet Machining process is impacted by
nozzle wear, which intern depends on certain process as well as geometrical parameters such
as nozzle length, nozzle diameter, orifice size, nozzle inlet angle. This process is smooth and
free from vibration. This process having very low capital investment as well as heat generated
in this process becomes very less, so this process is used in various industrial application.
REFERENCES:1) https://learnmechanical.com/abrasive-jet-machining/
2) http://www.minaprem.com/micro-machining/ajm/advantages-and-limitations-ofabrasive-jet-machining-ajm-process/
3) https://learnmechanical.com/abrasive-jet-machining/
4) https://crbtech.in/abrasive-jet-machining-principles-advantages-limitations
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