International Journal of Engineering Trends and Technology (IJETT) – Volume 26 Number 2- August 2015
A Study on the Influence of Abrasive Flow Machining
Parameters on Edge Radius in Cross Drilled Holes
Deepak Devassia*1, Dr. Shajan Kuriakose#2, George Oommen#3 .
1
PG Scholar, Department of Mechanical Engineering, MA college of Engineering, Kothamangalam, Kerala,
India
2
Professor, Department of Mechanical Engineering, MA college of Engineering, Kothamangalam, Kerala, India.
3
SCI/Engr „SF‟ Manager, CS&SC-CF, CSC/LPSC/ISRO, Valiyamala, Trivandrum
Abstract — The effect of abrasive flow machining
parameters on edge radius in cross drilled holes of
launch vehicle fluid component made of Z30C13
stainless steel are studied. The main parameters are
abrasive size, abrasive concentration and number of
cycles. The experiment is conducted based on
Taguchi‟s L9 orthogonal array. The optimum
parameters for edge radius and the influence of each
parameter on edge radius are analysed by signal to
noise ratio and ANOVA.
Keywords — Abrasive flow machining, Cross drilled
hole , Edge radius, Orthogonal array, Signal to noise
ratio, ANOVA
I . INTRODUCTION
Abrasive flow machining (AFM) is a nonconventional machining process in which the
machining of inaccessible profiles are made possible
by the flow of an abrasive laden medium through the
profile. The accessibility of the medium is so high that
it can flow through small passages/vents where
conventional tool cannot reach. The advantages of
AFM can be utilized in machining fluid components
with cross holes and internal passages /vents.
Polishing and deburring of these features is difficult
because of inaccessibility of tools. Manual deburring
increases the risk of damaging finished surfaces.
Many of the recent anomalies in control components
have been attributed to loose metal particles getting
entrapped on the seating surfaces. More often these
particles are found to be generated from cross holes or
internal passageways which are hidden from the
normal vision. These particles are at many times not
visible to the naked eye and can be seen only under
magnification. Specialized viewing equipment’s are
not normally available at the shop floor to locate such
type of particles. As a result machining of such
components to the required finish become difficult at
the shop floor. AFM is an ideal solution for precision
deburring, polishing and edge radiusing of surfaces of
machined components. Abrasive action is highest in
most restricted passage leading to the removal of burrs
and edge polishing. This study aims at the
optimization of edge radius of launch fluid component
ISSN: 2231-5381
made of Z30C13 stainless steel by varying the
parameters .
II. LITERATURE SURVEY
Abrasive flow machining (EDM) is a widely used
unconventional manufacturing process that uses an
abrasive laden medium for machining complex shaped
workpieces or workpiece with internal passages /vents.
Jain[1] analyzed the effects of different process
parameters, such as number of cycles, concentration of
abrasive, abrasive mesh size and media flow speed, on
material removal and surface finish. He found the
dominant process parameters as concentration of
abrasive, followed by abrasive mesh size, number of
cycles, and media flow speed. Brass and aluminum are
the work materials and the experiments performed on
it. He also found that the material removal (MR) is
governed by initial surface finish and workpiece
hardness. As the percentage concentration of abrasive
in the medium increases, material removal increases
while the surface roughness value decreases. With
higher abrasive mesh size, both material removal and
improvement in the roughness value decreases.
S.Chouhan [2] investigated the surface finishing of die
steel with the use of abrasive flow machining.
Grinding medium is pressed along the contours at a
defined pressure and temperature. Depending on the
respective machining task, different specifications of
media are used. The surface finishing is better with
use of abrasive flow machining process as compared
to other flow machining processes. The change in
surface roughness, increases with the increase in
length of the work-piece and decreases with the
increase in cross section of the work-piece. Siddiqui[3]
studied the effect of different type of passages for the
laden medium outflow and the process parameters in
the abrasive flow machining. Cylindrical workpiece
made of brass with different cross sections of internal
passages and length have been micro machined by
abrasive flow machining technique and the output
responses material removal and surface roughnes
value are measured. The input parameters, such as
abrasive particle concentration, particle size, number
of cycles and media flow speed kept as constant. The
results infer the work-piece surfaces having single
passage for media outflow have higher material
removal and more improvement in surface roughness
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International Journal of Engineering Trends and Technology (IJETT) – Volume 26 Number 2- August 2015
compared surfaces having multiple passages and with
increase in the number of vents for media outflow the
performance measures decrease. J.Cherian[4] studied
the effect of AFM process parameters on surface
roughness and material removal rate. He found that
the average percent reduction in the surface roughness
can be improved by keeping the grain mesh number,
extrusion pressure and abrasive concentration at high
levels, also the average force ratio can be improved by
keeping abrasive concentration and extrusion pressure
at high level and grain mesh number at low level.
R.Guptha[5] analyzed the the key parameters abrasive
concentration, abrasive mesh size, diameter of rod and
rotational speed of tooling rod were varied to see their
effects on material removal. In this study a hybrid
machining process has been developed to enhance the
material removal rate . Effective MR is obtaind by
providing a centrifugal force to abrasive media by
rotating tool rod inside the workpiece .he also found
that abrasive concentration has the highest
contribution to MR. S. S. Hiremath[6] developed a
prototype model of an Abrasive Flow Machine (AFM)
with various sensors to monitor process parameters.
Experimentation was carried out on various
engineering materials and studied the quality
characteristics-surface finish achieved on various
kinds of workpieces. It was shown that a very high
surface finish is achieved as the experiments were
carried out for more number of passes and even small
intricate cavities available on internal surface of the
workpiece was machined to high quality surface finish.
Also the obtained results show that this process
completely removes all traces of thermal recast layers
remaining after spark erosion processes.
The abrasive laden media is filled inside the cylinders
and the workpiece is positioned in the fixture. The
media can move back and forth through the workpiece,
when the system is operating. The system is
automated with a timer circuit to control the direction
of flow and to set the number of cycles. One back and
forth movement of the cylinder is called one cycle.
B. Abrasive Media
The abrasive media consists of two parts, the abrasive
particles and the polymeric base. The abrasive
particles used is silicon carbide (SiC) and
the
polymeric base is developed
Fig.2. Abrasive media
from Vikram Sarahbhai Space Center of
Trivandrum
ISRO,
C. Workpiece
The workpiece used is a launch vehicle fluid
component made of Z30C13 stainless steel. The
workpiece is machined to the
II. EXPERIMENTAL DETAILS
The experiment is conducted at Liquid Propulsion
System Center of Indian Space Research
Organization, Trivandrum. The experimental details
are given below.
A. AFM Machine
For the study a two way abrasive flow machine has
been developed with two opposing pneumatic
cylinders connected each other to a fixture as shown in
Figure. 1.
Fig.3. CADD model of workpiece
required dimensions in CNC milling machine. The
experiment is conducted on the machined workpiece.
D. AFM Process Parameters and their Levels
Based on references from literatures and books the
process parameters and their levels selected are shown
below in Table.I.
Fig.1. AFM setup
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International Journal of Engineering Trends and Technology (IJETT) – Volume 26 Number 2- August 2015
TABLE I. PROCESS PARAMETERS AND LEVELS SELECTED
Parameters
Levels
Units
Response
1
2
3
Abrasive size
µm
8
63
150
Concentration
%by
weight
30
40
50
No. of cycles
Cycles/min
100
200
300
The edge radius is formed at the cross drilled hole of
the workpiece. So it can be measured only by cutting
the workpice
Edge
radius
.
E. Selection of Orthogonal Array
In this experiment the input parameters selected are
Abrasive size (As), Abrasive concentration (Ac) and
Number of cycles (Nc). Taguchi’s L9 orthogonal array
was selected for conducting the experiments, since
three factors are chosen with three levels each. The
selected orthogonal array for the experiment is shown
in the Table II.
Fig.4. CAD model showing edge radius
The computer generated cross sectional view of the
workpiece is shown in figure 4. The marked region is
the edge where the radius is measured.
IV RESULTS AND DISCUSSION
After the experimentation, the workpiece is cut to
equal half’s through the cross hole, as shown in figure.
5
TABLE II. L9 ORTHOGONAL ARRAY
Exp.
No
1
Parameter Combinations
Abrasive
No. of
Abrasive
Concentration
Cycles
size (A)
(B)
(C)
(µm)
(% by weight) (cycles/min)
8
30
100
2
8
40
200
3
8
50
300
4
63
30
200
5
63
40
300
6
63
50
100
7
150
30
300
8
150
40
100
9
150
50
200
F. Experimentation
The workpiece is machined as per the required
dimensions in a CNC milling machine. The abrasive
media is filled inside the cylinders of the AFM
machine. The media size is selected based on the
values in the OA, for each run. The workpiece is
positioned in the fixture of the AFM. The time is set in
the timer circuit for required cycles and the machine is
switched on. After machining the workpiece is taken
out from the fixture, cleaned and cut to two equal half
for measuring the edge radius.
Fig .5. Cross section of machined workpiece
The edge radius is measured and tabulated. The
optimum combination of parameters were found out
by calculating the signal to noise ratio and the
significance of each parameter on edge radius were
obtained by ANOVA [7-8].
A. Edge Radius
In the experiment, the desired characteristic for edge
radius is larger the better. The larger value of edge
radius is preferred within 0 – 0.5 mm tolerance as
smoothening of the edge at the cross drilled hole
reduce the chance of burr formation at the edge and
also reduce the pressure drop of fluid which flow
through that area.
/ = −10
(1)
Table III summarizes the edge radius of each slots and
their corresponding signal to noise (S/N) ratios
G. Measurement of Edge Radius
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International Journal of Engineering Trends and Technology (IJETT) – Volume 26 Number 2- August 2015
TABLE III. S/N RATIO FOR EDGE RADIUS
Parameters
TABLE IV. RESPONSE TABLE FOR EDGE RADIUS
Edge
radiu
s
S/N
ratio
100
0.048
-26.37
40
200
0.063
-24.01
8
50
300
0.089
-21.01
4
63
30
200
0.072
-22.85
5
63
40
300
0.093
-20.63
6
63
15
0
15
0
15
0
50
100
0.074
-22.61
30
300
0.099
-20.08
40
100
0.086
-21.31
50
200
0.108
-19.33
Exp.n
o
As
Ac
Nc
1
8
30
2
8
3
7
8
9
The main effects plot for S/N ratio is shown in Figure
6.
Level
As
Ac
Nc
-23.80
-23.10
-23.43
-22.03
-21.98
-22.06
-20.24
-20.98
-20.57
Optimum
3
3
3
Delta
3.55
2.11
2.85
rank
1
3
2
1
2
3
Based on the analysis of S/N ratio, the optimal
machining performance for edge radius is obtained at
abrasive size150µm (level 3), concentration 50 % by
weight (level 3) and number of cycles 300 cycles/min
(level 3). In the analysis, abrasive size is the most
influencing parameter followed by number of cycles
and concentration. Based on the ANOVA results in
Table V the percentage contribution of various factors
affecting edge radius is identified. Here, particle size
is the most influencing factor followed by number of
cycles. The percentage contribution of particle size
and number of cycles towards edge radius is 52.01 %
and 31.77 % respectively. Also the probability level of
concentration is more than α (0.05) which indicates
that it has least contribution towards edge radius.
Source
Degree of
freedom
Sum of
squares
Mean of
squares
Fig.6. Signal to noise plot for edge radius
The main effect plot shows that edge radius is
increasing as the particle size, concentration and the
number of cycle’s increases. This is because the
maximum material removal is occurring at these
conditions. From the S/N plot, highest values of S/N
ratio is selected as the optimum value and can be
inferred clearly from the response table of S/N ratio
given in Table IV
P
% Contribution
TABLE V. ANALYSIS OF VARIANCE FOR EDGE RADIUS
F
As
2
0.001454
0.000727
44.51
0.022
52.01
Ac
2
0.000453
0.000226
13.86
0.067
16.18
Nc
2
0.000889
0.000444
27.20
0.035
31.77
Error
2
0.000033
0.000016
Total
8
0.002828
0.04
B. Regression Equation
The obtained result of edge radius is used to
model a regression equation to predict other
combinations of parameters.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 26 Number 2- August 2015
Edge radius (mm) = 0.00633
+ 0.000217 Abrasive size (μm)
+ 0.000867 Abrasive concentration ( % by weight)
+ 0.000122 No. of cycles
C. Conformation Test
The optimal conditions and another four random
combination are set on the machine and experiment is
conducted and the result is noted. The same
combinations of parameters are tested by the
regression model and ANN. The predicted results are
compared to validate the regression model.
TABLE VI . EXPERIMENTAL V/S PREDICTED RESULT
Experimental
Level
Predicted edge radius
edge radius
Regression
ANN
0.110
0.1020
0.106
A1B3C1
0.067
0.0636
0.080
A2B3C3
0.093
0.0999
0.090
A3B3C3
(optimal)
A3B3C2
0.093
0.1066
0.108
A1B1C3
0.078
0.0706
0.080
The comparison shows that there is no much
difference in the three results obtained, which shows
that the regression model is fit for prediction of edge
radius for future reference. This can be clearly
understood from figure 7.
analysis, optimum condition for edge radius is
obtained at particle size of 150 μm (level3),
concentration 50% by weight (level 3) and number of
cycles 300 cycles/min (level 3). Particle size and
number of cycles are found to be the most influencing
parameter on edge radius with 52.01% and 31.77 %
contribution respectively followed by concentration
with 16.18% contribution. From the results obtained a
regression model is developed to predict the edge
radius. The validity of the model is found by
predicting and experimenting results with unknown
parameter combination and comparing the result. In
this study the predicted and experimented results are
almost similar which shows the regression model is fit
for prediction.
ACKNOWLEDGEMENT
The authors acknowledge the guidance and technical
support provided by the Liquid Propulsion System
Centre of Indian Space Research Organization,
Trivandrum and Carborundum Universal Limited,
Kalamassery for providing the essential abrasive
particles.
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Fig.7. Compared results for edge radius
V. CONCLUSION
In this study the influence of the process parameters
on Edge radius of launch vehicle fluid component
made of Z30C13 stainless steel by AFM was studied
using Taguchi L9 orthogonal array method. The edge
radius during machining is mostly influenced by
particle size and number of cycles. Concentration has
a little influence in case of edge radius. Based on the
ISSN: 2231-5381
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