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Proceedings of the World Congress on Engineering 2009 Vol I
WCE 2009, July 1 - 3, 2009, London, U.K.
New Cooling Channel Design for I njection
Moulding
A B M Saifullah, S.H. Masood and Igor Sbarski
Abstract— Injection moulding is one of the most versatile and
important operation for mass production of plastic parts. In this
process, cooling system design is very important as it largely
determines the cycle time. A good cooling system design can
reduce cycle time and achieve dimensional stability of the part.
This paper describes a new square sectioned conformal cooling
channel system for injection moulding dies. Both simulation and
experimental verification have been done with these new cooling
channels system. Comparative analysis has been done for an
industrial part, a plastic bowel, with conventional cooling
channels using the Moldflow simulation software.
Experimental verification has been done for a test plastic part
with mini injection moulding machine. Comparative results are
present ed based on temperature distribution on mould surface
and cooling time or freezing time of the plast ic part. The results
provide a uniform temperature distribution with reduced
freezing time and hence reduction in cycle time for the plastic
part.
Index Terms—Conformal cooling channel, Cycle time
Moldflow, Square shape.
I. INTRODUCTION
Injection moulding is a widely used manufacturing process
in the production of plastic parts [1]. The basic principle of
injection moulding is that a solid polymer is molten and
injected into a cavity inside a mould which is then cooled and
the part is ejected fro m the machine. Therefore the main
phases in an injection moulding process involve filling,
cooling and ejection. The cost-effectiveness of the process is
mainly dependent on the time spent on the moulding cycle in
which the cooling phase is the most significant step. Time
spent on cooling cycle determines the rate at which parts are
produced. Since, in most modern industries, time and costs
are strongly linked, the longer is the time to produce parts the
more are the costs. A reduction in the time spent on coo ling
the part would drastically increase the productio n rate as well
as reduce costs. So it is important to understand and optimize
the heat transfer process within a typical moulding process.
The rate of the heat exchange between the injected plastic and
the mo uld is a decisive factor in the economical performance
of an injection mould
A B M Saifullah is a research doctoral student at Industrial Research Institute
Swinburne (IRIS), Swinburne University of Technology, Melbourne,
Australia (e-mail- msaifullah@swin.edu.au), also Member, IAENG.
S. H. Masood is a Professor of Mechanical & Manufacturing Engineering at
Faculty of Engineering and Industrial Sciences, Swinburne University of
Technology, Melbourne, Australia. (Corresponding author, ph:+61-3-9214
8260, fax: +61-3-9214 5050, e-mail: smasood@swin.edu.au)
Dr Igor Sbarski is a Senior Lecturer at Faculty of Engineering and Industrial
Sciences, Swinburne University of Technology, Melbourne,
Australia.(e-mail: isbarski@swin.edu.au ).
3
.Heat has to be taken away from the plastic material until a
stable state has been reached, which permits demolding. The
time needed to accomplish this is called cooling time or
freezing time of the part. Proper design of cooling system is
necessary for optimum heat transfer process between the
melted plastic material and the mould. Traditionally, this has
been achieved by creating several straight holes inside the
mould core and cavity and then forcing a cooling fluid (i.e.
water) to circulate and conduct the excess heat away from the
molten plastic. The method s used for producing these holes
rely on the conventional machining process such as straight
drilling, which is incapable of producing complicated
contour-like channels or anything vaguely in 3D space.
An alternative method of coo ling system that co nforms or
fits to the shape of the cavity and core of the mould can
provide better heat transfer in injection moulding process, and
hence can result in optimum cycle time. This alternative
method uses contour-like channels of different cross-section,
constructed as close as po ssible to the surface of the mould to
increase the heat absorption away from the molten plastic.
This ensures that the part is cooled uniformly as well as more
efficiently. Now-a-days, with the advent of rapid p rototyping
technology such as Direct Metal Deposition (DMD), Direct
Metal Laser Sintering (DMLS) and many advanced computer
aid ed engineering (CAE) software, more efficient co oling
channels can be designed and manufactured in the mould with
many complex layout and cross-sections[2,3,4].
This paper presents a square section conformal co oling
channel (SSCCC) for injection moulding die. Simulation has
been done for an industrial p lastic part, a circular plastic
bowel for these SSCCC and compared with conventional
straight cooling channels (CSCC) with Moldflow Plastic
Inside (MPI) software. Comparative experimental
verification has also been performed with SSCCC and CSCC
die for a circular shape test part with mini injectio n moulding
machine for two plastic materials. Result shows that SSCCC
die gives better cooling time and temperature distribution than
that of CSCC dies.
II. DESIGN OF THE PART AND MOULDS
A. Part design
The part circular plastic bowl made of polyprop ylene (PP)
thermoplastic, as shown in Fig 1(a) has been designed with
Pro -Engineer CAD software. It was then exported to IGES
(Initial Graphics Exchange Specification) file surface
model to impo rt in MPI for analysis. Material volume of
the plastic part is 177.90cm and its weight is 162.3 gm.
Experimental test part as shown in Fig 1(b) has also been
d esigned with Pro-Engineer software. Experimental
ISBN: 978-988-17012-5-1
WCE 2009
Proceedings of the World Congress on Engineering 2009 Vol I
WCE 2009, July 1 - 3, 2009, London, U.K.
verification has b een done with two types of plastic
materials, PP and ABS (Acrylonitrile Butadiene Styrene).
Test part volume was 8.8 cm3, and part weight for ABS and
PP were 8.68 gm and 8.13gm respectively.
(a)
(b)
(a) (b)
Fig-1 CAD model of (a) Circular plastic bowel, (b) Test part.
B. Mould Design
Mould design has been done using Pro/Moldesign module
of the Pro /Engineer system. This mould is then manufactured
with Computer Numerical Control (CNC) machine. The
mould shown in Fig 2 has two parts, the core and the cavity.
Square section conformal cooling channel (SSCCC) has been
produced around the cavity by CNC machining of one half of
the channel on cavity part and the other half on the core part.
Both halves are then joined with screws and sealed with liquid
gasket (Permatex) to avoid water leakage.
Fig-2 Assembly CAD model of mould with core (top )
and two cavity parts.
III. ANALYSIS AND RESULTS
MPI simulation software has been used for part analysis
[5]. Analysis sequence was flow-cool-warp. Polyprop ylene
plastic material has been used for analysis. Comparative
analysis has been done with conventional straight coo ling
channel (CSCC) and SSCCC. The diameter of CSCC was 12
mm and the length of SSCCC section size was 12 mm (Fig 3).
Fusion meshing with global edge length of 0.995 cm has been
used . The numbers of mesh elements used were 12944 and
12291 for CSCC and SSCCC respectively.
3
Fig-3 Analysis setting in MPI (a) CSCC (b) SSCCC
Both cases used cooling medium as normal water of 25°C.
Reynolds number was 10000, melting temperature was 230
°C. Comparative analysis result from MPI as shown in Fig 4
shows that SSCCC shows better temperature distribution and
(a) (b)
Fig-4 Comparative freezing or cooling time (a) CSCC
(b) SSCCC.
less part freezing time than CSCC. In case of CSCC, most of
the part cools in about 24 second except the top few areas,
while on the other hand SSCCC diagram shows that it is less
than 20 seconds. And also CSCC shows the time to freeze
range to be 0.4 6-93.7sec and SSCCC shows this to be
0.3-87.15sec. So, using SSCCC, 5 second of cooling time has
been reduced which is 3 5% reduction of cooling time.
IV. EXPERIMENTAL VERIFICATION AND RESULTS
Experimental verification has been done with a circular
shap e plastic test part using the machined mould as shown in
Fig 5. Part diameter was 40 mm and thickness was 7 mm.
The mould dimension was 10x10x2.5 cm . Mould material
was mild steel. Experiment has been done with a mini
(a) (b)
Fig-5 (a) Mild steel Core (left) and cavity with SSCCC
(b) CSCC of mild steel.
ISBN: 978-988-17012-5-1
WCE 2009
Proceedings of the World Congress on Engineering 2009 Vol I
WCE 2009, July 1 - 3, 2009, London, U.K.
injection moulding machine of TECHSOFT mini moulder
(Fig 6). Two thermocouples TC08 K type of PICO
technology have been used to measure temperature of top and
bottom surface of the test part. Melting temperature was
250°C fo r both ABS and PP. Normal water has been used as
a cooling medium, room temperature has been measured as 25
°C, so is cooling water. Cooling channel diameter was 5 mm
for CSCC and SSCCC section size was 5 mm. With two
thermocouples, surface temperature of the test part has been
measured for every second.
Fig-8 Comparative temperature plot for PP
In experimental tests, twenty samp le test parts have been
produced for ABS and PP material for experimental
verification and in every case almost the same data has been
found. Fig 9 shows the sample test parts in ABS and PP,
which have been produced fo r experimental verification.
Fig-6 Experimental setup for test injection moulding,
left: mini moulder, right: temperature outp ut in PC.
Fig
7
and
Fig
8
show the comparative temperature
distribution for top and bottom surface of the plastic parts for
30 second.
Fig-9 Sample test part prod uced for experimental verification
Left: ABS right: PP plastic.
V. CONCLUSION
The cooling process is one o f the most important sub processes
in
injection
moulding
because
it
normally
accounts
for
approximately half of the total cycle time and affects directly the
Fig-7 Comparative temperature plot for ABS
From Fig 7 it is noted that for the ABS plastic, using
SSCCC, the top face and bottom face of test part cooled
earlier than that with CSCC. In case of SSCCC, maximum top
and bottom surface temperature recorded at particular time
immediately after injection were 53.36 °C and 52.1°C. After
30 second, this temperature reduced to 42.47 °C and 43.07
°C, whereas, for CSCC they were 53.24, 52.01 and 47.47,
47.72 °C. So in average, 4 to 5 °C reduction in temperature
happens using the SSCCC. Similar results also have been
found when using PP as the part material. From Fig 8, it can
be shown that using SSCCC, about 2 to 3 °C reduction in
temperature can be possible.
shrinkage, bending and warp age of the moulded plastic product.
Therefore, designing a go od cooling channel system in the mould is
crucial since it influences the production rate and quality. The
results of MPI simulation and experimental verification show that
using square shape conformal cooling channels gives up to 35%
reduction in cooling time and 20% of the total cycle time can b e
obtained, thus greatly improving the production rate and the
production quality of injection moulded parts.
ACKNOWLEDGMENT
These authors are grateful to Mrs. Meredith and Phil Watson
of Faculty of Engineering and Industrial Science,
Swinburne University of Technology for their technical
support for die making with CNC machining.
ISBN: 978-988-17012-5-1
WCE 2009
Proceedings of the World Congress on Engineering 2009 Vol I
WCE 2009, July 1 - 3, 2009, London, U.K.
REFERENCES
[1 ] D.V. Rosato, D.V. Rosato and M.G. Rosato, Injection
Moulding Handbook-3rd ed , Boston, Kluwer Academic Publishers, (2003).
[2 ] X. Xu, E. Sach and S.Allen, The Design of Conformal
Cooling Channels In Injection Moulding Tooling,Polymer Engineering and
Science, 4, 1, pp 1269-1272, (2001).
[3] D.E. Dimla, M. Camilotto, and F. Miani: Design and optimization of
conformal cooling channels in injection moulding tools, J. of Mater.
Processing Technology, 164-165, pp 1294-1300, (2005).
[4] A B M Saifullah and S. H. Masood, Optimum cooling channels design and
Thermal analysis of an Injection moulded plastic part mould, Materials Science
Forum, Vols. 561-565, pp. 1999-2002, (2007).
[5] A B Saifullah, S. H. Masood and Igor Sbarski, cycle time
optimization and part quality improvement using novel cooling channels in plastic
injection moulding. ANTEC@NPE 2009, USA.
ISBN: 978-988-17012-5-1
WCE 2009
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