Multi Objective Optimization of Plastic Welding Parameters in USPW of PMMA CM-205 using Grey Relational Analysis

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
Volume: 04 Issue: 06 | June -2017 www.irjet.net p-ISSN: 2395-0072
© 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 1324
MULTI OBJECTIVE OPTIMIZATION OF PLASTIC WELDING PARAMETERS
IN USPW OF PMMA CM-205 USING GREY RELATIONAL ANALYSIS
Sathananthan R1, Madhu Mohan2, Dr. Suresh K S3
1PG Scholar, Dept. Of Mechanical Engineering
NSS College of Engineering, Palakkad-8
2,3Assistant Professor, Dept. of Mechanical Engineering
N S S College of Engineering, Palakkad-8
---------------------------------------------------------------------***---------------------------------------------------------------------
Abstract - Ultrasonic Plastic Welding (USPW) has received
significant attention in the past few years and has become
more durable & suitable for a wide range of uses. The major
aspect of this study is to have a good understanding of the
joint design will ensure the good quality of weld. Since, the
joint configurations find its most importance in USPW to
ensure that plastic assemblies are adequately joined. Because,
the joint configurations is considered to be one of the major
influencing parameterthatresponsiblefortransferringenergy
to the welding zone & the main objectives of this study
investigate and evaluate the effect of different USPW
parameters (Joint configurations, Hold time, Weld time &
Pressure) on welding tensile strength & percent elongation of
PMMA. Poly(methyl methacrylate) PMMA is also known as
acrylic glass, it is a transparent thermoplastic and is used as
an shatter- resistant alternative to glass. It is having a very
wide range of applications in automobile industry like,
assembling vehicle lightunits and dashboard instrumentsetc..,
In this paper various parametersinvolvedinUSPWofPMMA is
investigated for obtaining optimal weldingconditionatwhich
the maximum weld joint strength can achieve to improve
weld-ability of plastic material & production rate. Minitab 17
is used for L27 full factorial DOE & Taguchi method is used for
analysis. Grey RelationalAnalysis(GRA)methodwasemployed
to determine the optimal set of parameters forthebestquality
of weld.
Key words: USPW, PMMA, Minitab 17, Taguchi design, GRA
1. INTRODUCTION
1.1 Importance of Plastics in Engineering:
Within the basic engineering materials widely
utilized and accepted now a days, plastics have attainedfirm
place. As with any particularmaterial ormaterials,plasticsin
general are no issues for design problems. However,
necessary degree of action is to be taken in their application
otherwise disappointing results may lead to wrong
impressions regarding their more possible advantages.Asis
characteristic with other types of production, where
machining, fitting, assembling and finishing operations can
be minimized/ eliminated, plastics molding may prove
highly in economical. The critical design consideration thus
highly that of suitability of the material for the uses. The
suitability factor cannot be over-emphasized. Properly
applied plastic materials provide a host of unusual
properties which suit them for a wide range of applications.
Generally, Plastics are strong, light, highly di-electric in
nature, workable, corrosion and chemical resistant and
durable. Satisfactory applications range over a wide variety
of machine parts from hard wheels, gears and levers to
housing, frames, and insulators. It would be difficult tothink
our modem world without plastics. Now a day’s they are an
integral part of everyone’s lifestylewithapplicationsvarying
from commonplace domestic articles to modern scientific
and medical instruments. Today designers and engineers
readily turn to plastics because they provide combinations
of properties which are not available in any other materials.
Plastics provides advantages such as lightness, resilience,
resistance to corrosion, colour, fastness, transparency, ease
of processing, etc., and although they have their own
limitations like burns out or distortedathighertemperature,
their developments is limited only by the ingenuity of the
designers.[1]
1.2 What is ultrasonic?
Ultrasonic is acoustic (sound) energy in the form of
waves having a frequency above the human hearing range.
The highest frequency that the human ear can detect is
approximately 20 thousand cycles per second (20,000
Hz).This is where the sonic range ends, and where the
ultrasonic range begins. Ultrasound is used in electronic,
navigational, industrial, and security applications. It is also
used in medicine to view internal organs of the body.
Ultrasonic is a branch of acoustics dealing with the
generation and use of (generally) in audible acoustic waves.
There are two broad areas of use, sometimes called as the

low-and high-intensity applications. In low-intensity
applications, the intent is to convey information about or
through a system, while in high-intensity applications; the
intent is to permanently alter a system. To some extent, the
low- and high-intensity fields are also delineated by a
frequency range and power level. Thus, low-intensity
applications typically involve frequencies on the order of
106Hz or higher and power levels on the order of mille
watts. High-intensity applications will typically involve
frequencies of 5 to 100 kHz and powers of hundreds to
thousands of watts. In actual fact, the total frequency range
of all ultrasonic applications is enormous, rangingfrom5-10
kHz to as high as 10 GHz. There are also applications,such as
sonar, which are exceptions to the previous categorizations,
since intense power levels are involved in conveying
information via underwater sound.[2]
1.3 Concept of Ultrasonic plastic Welding:
Ultrasonic plastic welding is the joining of plastic
through the use of heat generated from high-frequency
mechanical motion. It is accomplished by converting high-
frequency electrical energy into high-frequency mechanical
motion. That mechanical motion, along with applied force,
creates frictional heat at the plastic components mating
surfaces (joint area) so the plastic material will melt and
form a molecular bond between the parts. No solvents,
adhesives, mechanical fasteners, or other consumables are
required, and finished assemblies are strong and clean.
Ultrasonic plastic Welding is the fastest and most cost
effective method used today to join and assemble plastic
parts. Ultrasonic plastic welding is cost effective and a green
technology. Ultrasonic welding eliminates the need to use
fasteners, glues and/or solvents. Ultrasonic plastic Welding
can be used to join all rigid thermoplastics. Ultrasonic
welding uses an acoustic tool called an ultrasonic horn made
to match your parts design. Ultrasonic Welding is converted
to heat through friction that melts the plastic. The main
components of an ultrasonic weldingsystemaretheactuator
and power supply, converter/booster and ultrasonic horn,
part holding weld fixture/jig.[3]
1.4 Ultrasonic Plastic Welding Principle:
Connecting hard plastics by ultrasonic is done through
friction on the contact surfaces. The principle is to touch the
surface of the work pieces vertically with a tool that
oscillates with a high frequency (e.g.20 KHz). This tool,
oscillating with the frequency produced by the machine
(called sonotrode) touchestheplastic work piece&transfers
energy.
Figure -1: Principle of USPW [6]
The work piece as the element of energy
transformation getsthemost possibleenergyforthewelding
process if the losses between the two contact surfaces of
sonotrode and plastic are the smallest possible. The work
piece begins to oscillate in the standing transverse wave
train, and the maximum begins to form itself on the contact
surfaces of the two pieces of plastic to be connected. This
phenomena is similar to the one discovered by MELDE,
called the effect of the oscillating ropes (loop of oscillationat
the loose end!). Under the effect of the ultrasonic,
transmitted through the sonotrode, the energized part
begins oscillating on its surface in a locally limited way,
while the other part – the one to be connected – does not
move. Under the influence of a set pressure, superimposed
by ultrasonic, a secondary friction of a highfrequency begins
to heat up the contact surfaces of the parts to be connected.
The plastic melts immediately and after cooling off a sturdy
& homogeneous weld is obtained.
2. EXPERIMENTAL PROCEDURES
2.1 Experimental Setup
All the welding was carried out using a conventional
ultrasonic plastic machine (1500W, 20 kHz) manufactured
by M/s National Indosonic.

Figure -2: USPW Machine
Horn made of Al-Ti alloy was used for this study.
The horn (Bezier) used for welding had diameters of 28 and
30mm for near field welding, the material investigated is
PMMA (amorphous).
Table -1: Properties of PMMA
Material PMMA cm-205
Colour Transparent
Density (ρ)
1190
Melting point ( (104-118)
Decomposition temperature ( >288
Flexural modulus (GPa) 2.8
Maximum tensile strength (Mpa) 70
Maximum tensile elongation (%) 12
The standard sample shown in Figure 3 (developed
by Nedulandse Philips) [5] was used for analysis and
experimental work.
Figure -3: Model used for analysis and
experimental work
A standardized sample (which was developed by
Nedulandse Philips) was used in all the experiments in near
field welding. The specimen with different energy directors
were made by injection molding. A ZWICK 1484 tensile
tester was used to measure the strengths of the welded
joints. TestproceduresaccordingtoASTMstandardD638-97
(Standard Test Method for Tensile properties of plastics)
were used. The deformation rate used in the testing was 20
mm/min.
Figure 4 Tensile testing of PMMA welded specimen

2.2 USPW Parameters
Table -2: Properties of PMMA
Parameter Levels
1 2 3
Joint Configuration T C S
Hold Time (sec) 2 2.5 3
Weld Time (sec) 2 2.25 2.5
Pressure (bar) 2 2.5 3
An experiment must be designed so that the
information about the parameters affecting the process and
inference about the system can be drawn with minimum of
efforts & time being consumed.DesignofExperiments(DOE)
is a methodology which helps us exactly do this. Hence, the
experimental work is planned using the DOEprocedure.The
design of experiments is indicated in Table 3. The first &
foremost consideration is to selecttheparameterswhichare
to be controlled i.e. independent variables or confounding
variables & the parameters that are to be measured as the
response parameters representingthequalityoftheprocess.
The key parameters for ultrasonic plastic welding are joint
configurations, hold time, weld time & pressure.
Tensile strength and Percentage of elongation at breaking
load are taken as the response variables. The frequency of
generator is not taken as parameter for the experiment. as
the machine is having fixed generator frequency (i.e. 20
kHz). Also the Bezier horn [4] as shown in figure 5. Is tuned
at only one frequency.
Figure -5: Bezier shaped Horn
3. RESULTS AND DISCUSSIONS
Experiments were conducted as per L27 full
factorial DOE. The results obtained after USPW is
represented in Table 4.
Table -3: Design of Experiments
Exp.
No.
Joint
Configuration
Hold
Time
(sec)
Weld
Time
(sec)
Pressure
(bar)
1 T 2 2 2
2 T 2 2.25 2.5
3 T 2 2.5 3
4 T 2.5 2 2.5
5 T 2.5 2.25 3
6 T 2.5 2.5 2
7 T 3 2 3
8 T 3 2.25 2
9 T 3 2.5 2.5
10 C 2 2 2
11 C 2 2.25 2.5
12 C 2 2.5 3
13 C 2.5 2 2.5
14 C 2.5 2.25 3
15 C 2.5 2.5 2
16 C 3 2 3
17 C 3 2.25 2
18 C 3 2.5 2.5
19 S 2 2 2
20 S 2 2.25 2.5
21 S 2 2.5 3
22 S 2.5 2 2.5
23 S 2.5 2.25 3
24 S 2.5 2.5 2
25 S 3 2 3
26 S 3 2.25 2
27 S 3 2.5 2.5
Grey relational method is applied in the USPW
response data. Out of two output responses,moreweightage
(0.9) was given to the Tensile strength and less weightage
(0.1) was applied to the percentage of elongation. Signal to

noise ratios of the output responseswerefoundusinghigher
the better criterion for both the Tensile strength and
Percentage of elongation. The values of S/N ratios are
shown in Table 5. Now, the grey relational coefficients and
grey relational grades are calculated as shown in the Table6
and Table 7 respectively.
Higher the GRG, higher is the performance. Table 8
presents response table for mean of GRG. From this table, it
is clear that that the most influencing factor is Joint
configurations. Then it is Hold time, weldtimeandfinallythe
pressure. Also, from this table, we obtain the optimum set of
parameters. The optimum parameters was predicted to be
Triangular shaped joint configurations, Hold time = 3sec,
Weld time = 2.5sec and Pressure = 2.5bar. Figure 9 depicts
the same things discussed in the response table. Optimum
sets of parameters are those levels in whichthemeanofGRG
is maximum.
(a)
(b)
Figure -6: PMMA test specimens (a) After USPW & (b)
After tensile testing
Figure -7: Stress vs Strain curve of PMMA
Table -4: Experimental results
Exp.
No.
Tensile Strength
(
Percent
Elongation (%)
1 2.705 2.93
2 3.050 3.04
3 3.566 2.86
4 3.382 2.84
5 4.400 2.81
6 4.681 2.16
7 3.438 3.18
8 4.403 2.89
9 4.920 2.63
10 1.265 2.56
11 1.377 2
12 1.491 2.26
13 1.866 2.19
14 1.928 2.16
15 2.116 2.26
16 1.449 2.46
17 1.591 2.56
18 1.554 2.15
19 1.522 2.12
20 1.716 2.29
21 2.078 2.48
22 2.233 2.37
23 2.593 2.30
24 2.674 2.26
25 2.819 2.93
26 2.933 1.86
27 3.720 2.76

Table -5: Values of S/N ratios
0 S/N (T.S) S/N (% E)
1
8.6433 9.3374
2
9.6860 9.6575
3
11.0436 9.1273
4
10.5835 9.0664
5
12.8691 8.9741
6
13.4068 6.6891
7
10.7261 10.0485
8
12.8750 9.2180
9
13.8393 8.3991
10
2.0418 8.1648
11
2.7787 6.0206
12
3.4696 7.0822
13
5.4182 6.8089
14
5.7021 6.6891
15
6.5103 7.0822
16
3.2214 7.8187
17
4.0334 8.1648
18 3.8290 6.6488
19
3.6483 6.5267
20
4.6903 7.1967
21
6.3529 7.8890
22
6.9778 7.4950
23
8.2761 7.2346
24
8.5432 7.0822
25
9.0019 9.3374
26
9.3462 5.3903
27
11.4109 8.8182
Table -6: Grey Relational Coefficients
Exp
No.
Grey Relational Coefficient
Tensile Strength GRC Elongation GRC
1 0.4520 0.7252
2 0.4942 0.8250
3 0.5744 0.6734
4 0.5430 0.6600
5 0.7784 0.6407
6 0.8843 0.3928
7 0.5521 1.0000
8 0.7794 0.6947
9 1.0000 0.5454
10 0.3333 0.5156
11 0.3402 0.3586
12 0.3476 0.4177
13 0.3743 0.4000
14 0.3791 0.3928
15 0.3945 0.4177
16 0.3449 0.4782
17 0.3544 0.5156
18 0.3518 0.3905
19 0.3497 0.3837
20 0.3632 0.4258
21 0.3913 0.4852
22 0.4048 0.4489
23 0.4398 0.4285
24 0.4486 0.4177
25 0.4651 0.7252
26 0.4790 0.3333
27 0.6036 0.6111
Table -7: Grey Relational Grades
Exp No. GRG Rank
1
0.2396 11
2
0.2636 9
3
0.2921 7
4
0.2773 8
5
0.3823 4
6
0.4175 2
7
0.2984 6
8
0.3855 3
9
0.4772 1
10
0.1757 26
11
0.1710 27
12
0.1773 24
13
0.1884 19
14
0.1902 18
15
0.1984 17
16
0.1791 22

17
0.1852 20
18
0.1778 23
19
0.1765 25
20
0.1847 21
21
0.2003 16
22
0.2046 15
23
0.2193 14
24
0.2227 13
25
0.2455 10
26
0.2322 12
27
0.3021 5
Table 9 presents the results of USPW performance
using initial and optimal input variables. The results show
that the GRG has improved while USPW using the predicted
optimum sets of parameters.
Table -8: Response table for mean of GRG
Figure -8: Main effects plot for GRG
Table -9: Results of USPW performance using initial and
optimal input variables
Initial
parameter
setting
Optimal USPW parameter
Predicted Experimental
Setting level A1 B1
C1 D1
A1 B3
C3 D2
A1 B3
C3 D2
Tensile
Strength
2.7050 4.9200
% Elongation 2.93 2.63
GRG 0.2396 0.4772
Improvement in GRG =0.2376
3. CONCLUSIONS
Experimental studyonUSPWofPMMACM-205hasbeen
done using a Bezier horn. The following conclusions were
made.
1. From GRA method, the most influential factor
affecting the quality of weld wasjointconfiguration.
Then hold time, weld time & pressure respectively.
A Triangular shaped energy directorshowsthebest
quality weld than the other shaped (circular &
square) energy directors.
2. The predicted optimumparameterswasTriangular
shaped joint configurations, hold time 3 sec, weld
time of 2.5 sec & pressure of 2.5 bar.
3. The GRG of optimum parameter yielded an
improvement of 0.2376. Therefore, it can be
concluded that GRA method coupled with Taguchi
design of experimentscanimprovethe weldquality.
4. From this experimental study,theresultsshowthat,
the values obtained for one of the responsevariable
i.e., percentage of elongation having the values in
the range of (2-2.5%). So we can able to conclude
that, the values of percent elongation at the break
load is very less for PMMA specimen as compared
to the other materials, due to its brittle behavior in
response to appliedload.Nonetheless,brittlenature
can be minimized by adding rubbertougheninginto
the specimen to increase the toughness of PMMA,
owing to its brittle behavior in response to applied
load.
Results of present study have been very much useful to
choose the optimal welding condition, at which the
maximum weld joint-strength can achieve to improve weld-
ability of non-metallic materials and production rate.
Factor
Level
Max-Min Rank1 2 3
Joint-
configurati
ons 0.3371 0.1826 0.2209
0.1544 1
Hold time 0.2090 0.2556 0.2759 0.0669 2
Weld time 0.2206 0.2460 0.2740 0.0533 3
Pressure 0.2482 0.2496 0.2427 0.0069 4

ACKNOWLEDGEMENT
The authors gratefully acknowledge the support
provided by the N. S. S. College of Engineering for this study.
Thanks are due to the Management and the Principal, PSG
College of Technology, Coimbatore for providing the
necessary infrastructure to setup the laboratory with
Department of Production Engineering, PSG College of
Technology for the tensile testing of specimens is gratefully
acknowledged.
REFERENCES
[1] Rajani(2008)A M.TechThesison“someinvestigationsin
effect of ultrasonic welding process parameters on lap
joint of plastics.”
[2] K.C.Srivastava “Hand book of ultrasonic testing”
published by International-2001(page no.1).
[3] Sunil K. Patel, A thesis on “Experimental investigation
and Parametric characteristics of an Ultrasonic Plastic
Welding for ABS, Polycarbonate and Acrylic material,”
Ganpat University.
[4] M.Roopa Rani, R. Rudramoorthy, Computational
modeling and experimental studies of the dynamic
performance of ultrasonic horn profiles used in plastic
welding, 2012
[5] A. Benatar, R.V. Eswaran, S.K. Nayar, Ultrasonic welding
of thermoplastics in the near field, Polym. Eng. Sci. 29
(23) (1989) 1689–1698.
[6] http://www.bransoneurope.eu/products/ultrasonic-
welding/technology
BIOGRAPHIES
Sathananthan R, was born in Kerala,
India in 1991. He received the B.Tech
degree in mechanical engineering from
Palakkad Institute of Science and
Technology (PISAT), Kerala,in 2014.He
is currently a M.Tech Scholar of
mechanical engineering and specialized
in computer integrated manufacturing (CIM), at NSS College
of Engineering. His research interest is in modern
manufacturing technology.

Multi Objective Optimization of Plastic Welding Parameters in USPW of PMMA CM-205 using Grey Relational Analysis

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Multi Objective Optimization of Plastic Welding Parameters in USPW of PMMA CM-205 using Grey Relational Analysis