Optimization of Process Parameters on Kerf Width & Taper Angle on En-8 Carbon Steel by Abrasive Water Jet Machining

Abstract

Abrasive water jet machining is a process where the material is removed by the principle of erosion. In this paper, the cutting of EN-8 carbon steel was carried out by AWJM process where the input parameters are water jet pressure, abrasive flow rate and traverse speed, which are taken into consideration machining. kerf width and the kerf taper angle of EN-8 steel are measured with respect to the above-mentioned input parameters using Taguchi L9 orthogonal array Design of Experiments. In this experiment, it has been observed that the main parameter which affects the experimental values is the abrasive flow rate.

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International Journal of Research in Advent Technology, Special Issue, March 2019
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Optimization of Process Parameters on Kerf Width & Taper Angle on En-8 Carbon Steel by Abrasive Water Jet Machining
1
Lakshmigalla Sunil Kumar,
2
U.Ashok Kumar,
3
P. Laxminarayana
4
P.Vivek Yadav,
4
T.Sachindra Bhushan,
4
P.Saikumar,
4
B..Nagaraju
1
Asst.prof,
4
UG Student, Department of Mechanical Engineering,NNRESGI, Ghatkesar,India
2
Asst.prof.
3
Prof. Mech. Engg., Dept., University College of engineering, Osmania University, Hyderabad
Abstract: Abrasive water jet machining is a process where the material is removed by the principle of erosion. In this paper, the
cutting of EN-8 carbon steel was carried out by AWJM process where the input parameters are water jet pressure, abrasive flow
rate and traverse speed, which are taken into consideration machining. kerf width and the kerf taper angle of EN-8 steel are
measured with respect to the above-mentioned input parameters using Taguchi L9 orthogonal array Design of Experiments. In
this experiment, it has been observed that the main parameter which affects the experimental values is the abrasive flow rate.
Keywords: Kerf Width, Kerf Taper Angle, Taguchi L9 Array.
1. INTRODUCTION
Abrasive water jet machining is a mechanical machining
process where the material is removed by the principle of
erosion. In this process, a high velocity stream of water jet
mixed with abrasive is made to impinge on the target
material that is to be machined. Upon the impingement of the
high velocity water and abrasive jet the material from the
target material is removed. In this process the water from the
reservoir is pumped to the intensifier where its pressure
increases up to 4 bars. The intensifier increases the pressure
of water from 4 bar to about 40000 bars and above as per the
requirement. The water from the intensifier is sent to the
accumulator where the pressure fluctuations due to high
pressures are eliminated. Then the pressurized water from
the accumulator is sent to the mixing chamber through
control valves. Before entering the nozzle the water is mixed
with abrasives particles in mixing chamber in a proportionate
ratio. This high pressure of water is converted into kinetic
energy of abrasive water jet in nozzle which is made to
impinge on the material which is to be machined.
2. WORKING
PRINCIPLE
The Abrasive Jet Machining is a non-traditional
machining process involves the application of a high-speed
stream of abrasive particles assisted by the pressurized air on
to the work surface through a nozzle of small diameter.
Material removal takes place by abrading action of abrasive
particles. Water jet machining is an erosion process
technique in which water under high pressure and velocity
precisely cuts through and grinds away minuscule amounts
of material. The addition of an abrasive substance greatly
increases the ability to cut through harder materials such as
steel and titanium. Water jet Machining is a cold cutting
process that involves the removal of material without heat.
This revolutionary technology is an addition to non-
traditional cutting processes like laser and plasma, and is
able to cut through virtually any material. The water jet
process is combined with CNC to precisely cut machine
parts and etch designs. Abrasive water jet uses the
technology of high-pressure water to create extremely
concentrated force to cut stuff. A water cutter pressurizes a
stream of pure water flow (without abrasive) to cut materials
such as foam, rubber, plastic, cloth, carpet and wood.
Abrasive jet cutters mix abrasive garnet to a pressurized
water stream to cut harder materials. Examples are stainless
steel, Titanium, glass, ceramic tile, marble and granite.
Water jet metal cutting machine yields very little heat and
therefore there is no Heat Affected Zone (HAZ). Water jet
machining is also considered as "cold cut" process and
therefore is safe for cutting flammable materials such as
plastic and polymers. With a reasonable cutting speed
setting, the edges resulting are often satisfactory. In Abrasive
Water Jet Machining, the abrasive particles are mixed with
water and forced through the small nozzle at high pressure so
that the abrasive slurry impinges on the work surface at high
velocity. Each of the two components of the jet, i.e., the
water and the abrasive materials have both separate purpose
and a supportive purpose. The primary purpose of the
abrasive material in the jet stream is to provide the erosive
forces. The water in the jet acts as the coolant and carries
both the abrasive and eroded material to clear of the work.

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Fig :1 Line Diagram of Abrasive Water jet Machining
3.
EXPERIMENTAL
SETUP
Aquajet abrasive water jet machine G3020 German
Engineering was used for the experiment. the input
parameters were taken into consideration with respect to
previous papers i.e. water jet pressure, traverse speed and
abrasive flow rate.
Fig :2. Abrasive Water jet Machining setup used for the Experiment of EN-8
Table:1 Machining Range of parameters of Abrasive Water Jet machine
Condition Range
Water jet pressure(bar) 4000
Abrasive flow rate(gm/min) 700
Traverse speed(mm/min) 1200
Nozzle diameter(mm) 1
Orifice(mm) 0.35

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Water flow rate(liters/min) 4
Abrasive particles(mesh garnet) 80
4.
EXPERIMENTAL
MATERIAL
EN8 carbon steel is a common medium carbon and
medium tensile steel, with improved strength over mild steel,
through-hardening medium carbon steel.EN8 steels are
generally used in the as supplied untreated condition. and
further surface-hardened by induction processes, producing
components with enhanced wear resistance. Material in its
heat treated forms possesses good homogenous metallurgical
structures, giving consistent machining properties. EN-8 is
used in manufacture of general purpose axles, shafts, bolts
etc.
Table:2. Shows the Chemical composition of EN-8 steel.
Element
Carbon
Silicon
Manganese
phosphorous
Sulphur
Composition 0.36 to 0.44% 0.10to 0.40% 0.60to 1.00% 0.050 max 0.050 max
Table:3. Mechanical properties of EN-8 steel.
Property Value
Max stress 700-850 n/mm
2
Yield stress 468 n/mm
2
min
Proof stress 450 n/mm
2
min
Elongation 16% min
Hardness 201-255 Brinell
5.
DESIGN
OF
EXPERIMENT:
The techniques usually performed in Design Of
Experiments to determine the individual and interactive
effects of many factors which could affects the results in
any design models. The shortest way for this experiment
that predicts the outcomes by changing the process
parameters which represents by one or more independent
variables. Main concepts in the experimental design
includes the establishment of validity, reliability, and
replicable of the experiments. These concerns may be
partially addressed by choosing the independent variables,
thus reduction in the risk of measurement errors, and
ensuring the documentation of the method is sufficiently
explained in detail. Related concerns includes achieving
appropriate level of statistical power and sensitivity is
observed and it cannot be manipulated of rewritten without
proper concerns.
To achieve a perfect cut, it requires that the combinations of
the process variables that gives the jet high enough energy
to penetrate through the work piece, which are considered
for machining and also for further performances. In present
study some
process parameters are water jet pressure, traverse speed and
abrasive flow rate were preferred as control factors for the
experiment and for obtaining the results.
Table:4.The initial input parameters for AWJM of EN-8 material
Parameter Level-1 Level-2 Level-3
Water jet pressure 3200 3400 3600
Abrasive flow rate 250 350 450
Traverse speed 154 176 220
Table:5.Experimental Design of Taguchi L9 orthogonal array with parameters for AWJM of EN-8 material cutting
Levels Water jet pressure Abrasive flow rate Traverse speed
1 3200 250 154
2 3200 350 176
3 3200 450 220
4 3400 250 176
5 3400 350 220

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6 3400 450 154
7 3600 250 220
8 3600 350 154
9 3600 450 176
6.
EXPERIMENTAL
OUTCOMES
The outcomes of the experiments are kerf width and kerf
taper angle of the material. Kerf width is the width of the cut made by the abrasive water jet on the target material. it
is measured by the formula given below
Kerf width =
(   )

Where, Top width is the width of the cut on the surface of
the material which is facing the abrasive water jet
Bottom width is the width of the cut at bottom surface
Kerf taper angle is the angle subtended by the kerf taper. It
is the deviation of the cut from the original cut. Kerf taper
angle is given by the formula as given below
Kerf taper angle,
Ɵ
=
tan
 (   )

Where, L is the length of the cut made by the abrasive water
jet
7.
RESULTS
AND
DISCUSSIONS
Table:6 .Results of AWJM of EN-8 material cutting using L9 Taguchi Design of Experiments
Experiments Input Parameters Outcomes
Water jet pressure Abrasive flow rate Traverse speed
Kerf width
Kerf Taper angle
1 3200 250 154 0.473 0.046
2 3200 350 176 0.539 0.012
3 3200 450 220 0.492 0.007
4 3400 250 176 0.448 0.065
5 3400 350 220 0.473 0.005
6 3400 450 154 0.636 0.002
7 3600 250 220 0.447 0.002
8 3600 350 154 0.604 0.005
9 3600 450 176 0.600 0.013
E
FFECT OF
K
ERF
W
IDTH WITH
W
ATER
J
ET
P
RESSURE
,
A
BRASIVR
F
LOW RATE
,
T
RAVERSE
S
PEED
Table:7 . Signal to Noise Ratios of AWJM of EN-8 material
Level Water Jet Pressure Abrasive Flow Rate Traverse Speed
1 6.013 6.827 4.939
2 5.804 5.417 5.59

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3 5.271 4.843 6.557
Delta 0.742 1.984 1.618
Rank 3 1 2
Fig 3:Signal to Noise Graph Kerf width of EN-8 by AWJM Process
EFFECT OF
K
ERF ANGLE
W
ATER
J
ET
P
RESSURE
,
A
BRASIVR
F
LOW RATE
,
T
RAVERSE
S
PEED
Level Water Jet Pressure Abrasive Flow Rate Traverse Speed
1 36.09 45.21 42.35
2 41.25 43.49 33.29
3 45.91 45.91 47.7
Delta 9.82 10.11 14.41
Rank 3 2 1
360034003200
7.0
6.5
6.0
5.5
5.0
450350250 2201 761 54
W
a
t
e
r
J
e
t
P
r
e
s
s
u
r
e
Mean of SN ratios
A
b
r
a
s
i
v
r
F
l
o
w
r
a
t
e
T
r
a
v
e
r
s
e
S
p
e
e
d
Main Effects Plot for SN ratios
Data Means
Signal-to-noise: Smaller is better

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Fig 4: Means Graph Kerf Taper angle of EN-8 by AWJM Process
8.
CONCLUSIONS
The present work deals with the abrasive water jet
machining of EN-8 Carbon steel materials.the following
results were drawn as follows
•
The optimum combination for Kerf Width is
A1B1C3 ie(water pressure of 3200 bar,
Abrasive flow rate of 250 gm/min, Traverse
speed of 220mm/min).
•
The optimum combination for Kerf Taper angle
is A3B3C3 ie(water pressure of 3620 bar,
Abrasive flow rate of 450 gm/min, Traverse
speed of 220mm/min)
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0.575
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450350250 2201 7 61 54
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