Journal of Materials Processing Technology 164–165 (2005) 1294–1300
Design and optimisation of conformal cooling channels in
injection moulding tools
D.E. Dimla
a, ∗
, M. Camilotto
b
, F. Miani
b
a
School of Design, Engineering and Computing, Bournemouth University, 12 Christchurch Road, Bournemouth, Dorset BH13NA, UK
b
DIEGM, Universit`a Degli Studi di Udine, via delle Scienze 208, 33100 Udine, Italy
Abstract
With increasingly short life span on consumer electronic products such as mobile phones becoming more fashionable, injection moulding
remains the most popular method for producing the associated plastic parts. The process requires a molten polymer being injected into a
cavity inside a mould, which is cooed and the part ejected. The main phases in an injection moulding process therefore involve filling, cooling
and ejection. The cost-efficiency of the process is dependent on the time spent in the moulding cycle. Correspondingly, the cooling phase is
the most significant step amongst the three, it determines the rate at which the parts are produced. The main objective of this study was to
determine an optimum and efficient design for conformal cooling/heating channels in the configuration of an injection moulding tool using
FEA and thermal heat transfer analysis. An optimum shape of a 3D CAD model of a typical component suitable for injection moulding was
designed and the core and cavity tooling required to mould the part then generated. These halves were used in the FEA and thermal analyses,
first determining the best location for the gate and later the cooling channels. These two factors contribute the most in the cycle time and
if there is to be a significant reduction in the cycle time, then these factors have to be optimised and minimised. Analysis of virtual models
showed that those with conformal cooling channels predicted a significantly reduced cycle time as well as marked improvement in the general
quality of the surface finish when compared to a conventionally cooled mould.
© 2005 Elsevier B.V. All rights reserved.
Keywords: Tool design optimisation; Injection moulding
1. Introduction
Injection moulding is one of the most exploited industrial
processes in the production of plastic parts. Its success re-

both has been proposed. This method utilises a contour-like
channel, constructed as close as possible to the surface of the
0924-0136/$ – see front matter © 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jmatprotec.2005.02.162
D.E. Dimla et al. / Journal of Materials Processing Technology 164–165 (2005) 1294–1300 1295
mould to increase the heat absorption away from the molten
plastic. This ensures that the part is cooled uniformly as well
as more efficiently.
The first part of this investigation concentrates on review-
ing and evaluating the injection moulding process, to set the
knowledge and background on the subject. Then a study of
proposed methods for developing and applying conformal
channels is conducted, identify the most viable method.
Specific softwarewasusedtooptimisethe design and con-
struction of the mould, with attention on refining the tool de-
sign through application of finite element and thermal flow
analyses. Successively, a study on the effectiveness of the
conformal cooling channel based on virtual models was per-
formed using I-DEAS
TM
software for prototyping and simu-
lation. The study is on going and hopefully would culminate
in the suggestion of the level of proficiency required using
virtual models in deciding moulding specifications for pro-
duction parts.
2. Brief overview of the injection moulding process
The injection moulding industry, like all industries, at
present needs to reduce costs to remain competitive. This
need has been addressed using various technologies rang-
ing from design software to computer numerical control ma-

Both the injection unit and the clamping system require
pressure with the latter developedtoresistthe former (Fig. 2).
Three different pressures can be distinguished in the injec-
tion unit: initial, hold and back. All these are obtained by
the action of a screw. In the clamping unit the oil pump of
the hydraulic system controls the pressure needed to move
the mould. Holding pressure is required to finish the filling
operation and maintained during solidification to supply the
shrinkage.
2.3. Time control
Time is the most significant parameter in the entire opera-
tion. Cost and machine efficiency can be estimated from the
cycle time. The principle temporal aspects to be controlled
include: gate-to-gate time, injection time and coolingtime. A
simple schematic illustration of a typical cycle time is shown
in Fig. 3.
2.4. Thermal proprieties
Despite their large diffusion, for all plastic materials tem-
perature range is a limit to their purpose. Both high and low
temperature can create damage to plastic components. It is
important to study thermal proprieties to understand and pre-
dict this behaviour. Therefore cooling times in moulding ma-
Fig. 2. Pressure history during injection moulding [2].
1296 D.E. Dimla et al. / Journal of Materials Processing Technology 164–165 (2005) 1294–1300
Fig. 3. Cycle time in injection moulding [2].
chines must be set carefully to permit, first, plasticization of
thethicknessand secondlydissipationof meltingheat.Unlike
metals,thethermalcapacityof plasticsis highwithcrystalline
plastics having a higher capacity than non-crystalline. Plas-
ticshavealargecoefficient of thermalexpansionifcompared,

In this way one can reduce the time required when the
moulding machine is started. When the polymer is injected,
it solidifies immediately touching the wall of the mould. If
the volume of the part is sufficiently big and its thickness is
too small, polymer solidified can obstruct the flow and hinder
a complete fillingof the cavity. In this casethe mould must be
heated to a particular temperature in order to permit the poly-
mer to flow. Despite all these advantages it may be noticed
that newtechnologiesinvolved in the production ofmoulding
tools with conformal channels can increase initial costs for
the additional complexity of the construction process.
3. Conformal channels—an overview
Results from an investigation of the effectiveness of con-
formal channels by Ring et al. [5] through the construction
of three different moulds with and without conformal cool-
ing, showed that the latter technique led to significant im-
provements and a general reduction of the cycle time while
ameliorating heat transfer.
A contribution to understanding the importance ofconfor-
mal channels and the employment of new high-conductivity
materials is given by Jacobs [6]. This research showed that
using nickel/copper moulds with conformal channels (cop-
per layered) led to productivity improvements of about 70%
when compared to a similar mould made with conventional
steel with drilled cooling channels. A comparison between
conformal channels and drilled cooling channels has also
beenconductedby Sachsetal.[3]. Theybased their investiga-
tion on modelling the core and cavity coupled with software
using both techniques and proceeded to construct the moulds
to compare theory and experimental data. Subsequent anal-

moulds are divided into simple shapes through a recognition
algorithm. Then for each shape, a specific cooling system is
constructed and at the end all of these are assembled. The
algorithm is based on the “superquadrics”, a family of para-
metrical shapes capable of modelling features, such as those
used in computer graphic. The main problem in this method
is selecting the best superquadric in order to approximate the
whole part. Once this is done, the cooling system becomes
easy to be modelled. This approach is very useful when there
are complex parts to create.
4. Mould part adviser (MPA) analysis
The basic idea was to construct a virtual model using
Model Master in I-DEAS
TM
and then use its Moldflow anal-
ysis option to find the best position for the runner. Then a
cooling system was designed for the part. Successively the
model was ready for further analysis such as finite element
analysis to refine the design, etc. MPA is a tool used ex-
clusively on the virtual solid model of the object, to help the
designer todeterminethemanufacturability ofthepartsofthe
mould. The only requirement of the software is the choice of
the material from which the object is intended to be made
from.
4.1. The model
The geometry of the model used in this exercise was cho-
sen according to specifications and characteristics required
in the object such as the inclusion of a draft angle to permit
the part to be ejected easily once cooled. To create this model
(Fig. 6) a rectangular surface was created and than extruded,

Fig. 7. Weld lines on the model surface.
1298 D.E. Dimla et al. / Journal of Materials Processing Technology 164–165 (2005) 1294–1300
Fig. 8. Reduced weld lines on the external surface.
Fig. 9. Single gate position: quality prediction.
The following observations weremadefromtheoptimised
solution of the part through computer prediction:
• Significantly reduced weld lines on both the external and
internal surfaces (Fig. 8) compared to Fig. 7.
• Improved quality prediction (Fig. 9).
• Further check on quality, cooling and sink marks was con-
ducted. Results indicated that the position of the gate was
optimum as no visible marks were evidenced and the in-
jection time reasonable at about 1 s (Fig. 10).
Fig. 10. Results form from Moldflow window analysis.
Fig. 11. Surface temperature.
Fig. 12. Freezing time.
• Similarly, good prediction rates were achieved for both the
surface temperature and freezing time (Figs. 11 and 12).
Fig. 10 essentially shows that the condition chosen from
the optimisation lead to a better product as the process falls
within the zone that indicates a good possibility of creating
the object without problems (green area). In the same form
the injection time is estimated to be 1.18 s.
5. Cooling channel positioning
5.1. General considerations
The final aspect of the object andthe precision of its shape
are determined not only by the process condition, but also by
the temperature of the wall of the cavity [11]. An accurate
positioning of the cooling channel system is thus needed to
satisfy quality standards of the production, as the tempera-

these areas.
On the issue of dimensional criteria in designing cooling
channels, three dimensions have to be considered: the diame-
ter of the cross-section (or the cross-section area if not circu-
lar), the distance between channels and the distance between
channel and wall of the mould. The main problems that arise
whenchoosingthesedimensionsconcerns the pressure losses
derived from the choice of the diameter and the design of the
channel. A heating/cooling relationship reported in Zollner
[11] gives a guidelineon the channels positioning.This states
that the value resulting from the solution of the relationship
should stay between 2.5 and 5% for semi-crystalline thermo-
plastics and between 5 and 10% for amorphous thermoplas-
tics.
5.3. Cavity channels positioning
Different solutions for the core and the cavity cooling sys-
tem were suggested for this analysis, consisting of a confor-
mal cooling system (Fig. 15) and a straight drilled cooling
system (Fig. 16) for comparison. Because these parts had to
be analysed after with a FEM package, only a quarter of each
insert was analysed. A system of four channels was created
followingthe surfaceofthe object, withthreechannelsplaced
to cool the lateral surface and one to cool the bottom one.
5.4. Core channels positioning
The conformal channels system for the core consisted
of two channels that followed the geometry of the shape
(Fig. 17) with one channel cooling the upper and the short
side surfaces and the second one cooling the big side surface.
All corners of the channels were filleted to decrease fluid-
dynamic losses of the liquid cooler. In the straight channel

use planar elements is required and this should lead to a bet-
ter understanding of the cooling times between conformally
cooled tools and conventional ones.
References
[1] D.M. Bryce, Plastic Injection Moulding, Society of Manufacturing
Engineers, Dearborn, MI, 1996.
[2] Anon., Intelligent Systems Laboratory, Michigan State Univer-
sity, 1999 [accessed October 30, 2003]. />trp/inj/inj time.html.
[3] E. Sachs, et al., Production of injection molding with conformal cool-
ing channels using the three dimensional printing process, Polym.
Eng. Sci. 40 (5) (2000) 1232–1247.
[4] K.W. Delgarno, Layer manufactured production tooling incorporat-
ing conformal heating channels for transfer moulding of elastomer
compounds, Plastic Rubber Compos. 30 (8) (2001) 384–388.
[5] M. Ring, et al., An investigation of effectiveness of conformal cool-
ing channels and selective laser sintering material in injection mould-
ing tools, RPD (2002) 1–5.
[6] F. Jacobs, High-conductivity Materials and Conformal Cooling
Channels, Warwick Manufacturing Group, Warwick University, UK
[accessed September 29, 2003]. />rpd399.xpress.html.
[7] Anon., Rapid tooling/rapid prototyping, EGS Associates Corpora-
tion [accessed September 29, 2003]. />rapid
tooling.htm.
[8] S.J. Park, T.H. Know, Thermal and design sensitivity analyse for
cooling system of injection mold, Part 1 and Part 2, J. Manuf. Sci.
Eng. 120 (1998) 287–305.
[9] X. Xu, et al., The design of conformal cooling channels in injection
molding tooling, Polym. Eng. Sci. 41 (7) (2001) 1265–1279.
[10] C.L. Li, A feature-based approach to injection mould cooling system
design, Comput Aided Des. 33 (2000) 1073–1090.