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Citation: Wang, R.-T.; Wang, J.-C.;
Chen, S.-L. Investigations on
Temperatures of the Flat Insert Mold
Cavity Using VCRHCS with CFD
Simulation. Polymers 2022,14, 3181.
https://doi.org/10.3390/
polym14153181
Academic Editors: Roberto Pantani,
Andrea Sorrentino and Dagmar
R. Dhooge
Received: 17 May 2022
Accepted: 3 August 2022
Published: 4 August 2022
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4.0/).
polymers
Review
Investigations on Temperatures of the Flat Insert Mold Cavity
Using VCRHCS with CFD Simulation
Rong-Tsu Wang 1,*, Jung-Chang Wang 2,* and Sih-Li Chen 3
1Department of Tourism and Leisure Management, Yu Da University of Science and Technology,
Miaoli County 36143, Taiwan
2Department of Marine Engineering (DME), National Taiwan Ocean University (NTOU),
Keelung 202301, Taiwan
3Department of Mechanical Engineering (ME), National Taiwan University (NTU), Taipei 10617, Taiwan
*Correspondence: rtwang@ydu.edu.tw (R.-T.W.); jcwang@ntou.edu.tw (J.-C.W.);
Tel.: +886-2-24622192 (ext. 7109) (R.-T.W.); +886-2-24622192 (ext. 7139) (J.-C.W.)
Abstract:
This paper adopted transient CFD (Computational Fluid Dynamics) simulation analysis
with an experimental method for designing and surveying the quick and uniform rise in the tempera-
ture of the plastics into the insert mold cavity. Plastic injection molding utilizing VCRHCS (Vapor
Chamber for Rapid Heating and Cooling System) favorably decreased the defects of crystalline plastic
goods’ welding lines, enhancing the tensile intensity and lowering the weakness of welding lines of a
plastic matter. The vapor chamber (VC) possessed a rapid uniform temperature identity, which was
embedded between the heating unit and the mold cavity. The results show that the tensile strength of
the plastic specimen increased above 8%, and the depths of the welding line (V-gap) decreased by
24 times (from 12
µ
m to 0.5
µ
m). The VCRHCS plastic injection molding procedure can constructively
diminish the development time for novel related products, as described in this paper.
Keywords: plastic; injection molding; simulation; vapor chamber; heating and cooling system
1. Introduction
Globally, the used capacity of plastic first became greater than steel after the 1980s [
1
,
2
].
Injection molding was the most frequently applied manufacturing procedure and one of
the most important techniques for global fabricating plastic parts [
3
,
4
]. However, it was a
technologically complicated procedure and very hard to consider all the transformations
occurring during the procedure. These complications include varying temperatures, filling
velocity and pressure, heating and cooling times, and packing and injection times [
5
–
7
]. A
wide variety of goods can be made utilizing injection molding [
8
]. Plastic materials have
been widely employed in machinery, the automobile industry, electrical, optical, medical,
and food. They are also used in other industries, including mobile phones, computers,
high-precision optical fiber connectors, CD films, and light guide plates. This is due to the
improvement in the quality of plastic materials and the development of types [
9
–
11
]. These
products have good electrical and mechanical properties and are lightweight and easy to
process with corrosion resistance and no-conductivity [
12
]. The injection molding process
had the advantages of fast production and automation. It was one of the most widely
used processes in producing plastic products [
13
]. The plastic was melted through the
screw of the injection molding machine and injected into the mold. The plastic cools and
solidifies to make a product. In the injection molding process, the plastic flows in a laminar
flow, and the melt front fills the mold cavity in the form of a fountain flow [
14
,
15
]. The
fountain flow allows the plastic to gradually solidify from the contact side of the mold wall
to the center layer of the plastic [
16
]. The increased solidification rate of the consolidating
layer accelerated as the mold temperature was too low. The passage area for the melt
was reduced, increasing the melt flow resistance [
17
]. When the plastic was difficult to
Polymers 2022,14, 3181. https://doi.org/10.3390/polym14153181 https://www.mdpi.com/journal/polymers
Polymers 2022,14, 3181 2 of 15
flow during the filling stage, it caused appearance defects (surface finish, roughness, and
sink marks) and had the problems of warping and deformation due to uneven residual
thermal stress and volume shrinkage [
18
,
19
]. Therefore, suitable operating parameters were
important for improving the effectiveness of the process and consistent product quality. The
operating parameters include injection speed, mechanical properties, holding pressure, melt
temperature, mold temperature, injection time, holding time, and cooling time. Although
the injection molding process had certain advantages in production, the appearance defects
of plastic products involving wind wrapping, burrs, appearance scratches, short shot,
welding line, warpage caused by residual stress, and poor precision were still problems.
The manufacturers must invest a lot of time and money to solve the process of product
development and production under the constraints of product modeling, mold structure,
and machine adjustment [20,21].
Most researchers have investigated injection molding process parameters and estab-
lished some correlations during production to assure quality and minimize defects [
22
].
Among these problems, welding lines were one of the most common cosmetic defects.
Although this defect can be overcome by secondary processing, such as painting and
electroplating, manufacturers want to avoid painting or electroplating as much as possible
during product development. Manufacturers especially avoid these solutions where a
large-scale application of plastic transparent appearance parts (such as Apple’s comput-
ers), plastic recycling restrictions caused by environmental protection issues, and product
cost control are involved. Moreover, this demand also made the appearance defect of
the welding line become the most troublesome problem for product developers when
designing the appearance. The main reason for the welding line defect was that the air
at the plastic junction could not be discharged from the mold cavity [
23
]. It was often
impossible to increase the exhaust in the mold when making transparent plastic parts,
resulting in the more obvious traces of the welding line. From the experience of previous
molding personnel, increasing the mold temperature or the plastic molding temperature
assisted in eliminating the welding line under the limitation that there is no additional
exhaust mechanism. The major method used was to increase the mold temperature (in-
creasing the plastic molding temperature can easily cause the plastic to crack) in the above
two methods. Sánchez et al. [
24
] introduced the mold temperature curve to understand
how RHCM (rapid heat cycle molding) works and compared the results with conven-
tional molding. They studied an electrical power system for a testing part injected with
two amorphous polymers (PC and ABS) under conventional and RHCM systems using
a pressure–temperature transducer and IR (infrared camera) to record both parameters
in the injection molding cavity. Measured values and tendencies were compared with
simulation tools with good correspondence. They considered that surface temperature
curves simulated and measured for both processes and thermal inertia observed in the heat
and cool processes should be carefully premeditated at the beginning of the plastic part
project. Li et al. [
25
] presented a novel method for predicting the warpage of crystalline
parts molded using the RHCM process. The results showed that the microstructure and
temperature were symmetrical along the thickness direction in CIM and asymmetrical in
RHCM. The predicted warpage was influenced by crystallinity. The warpage predicted
with crystallinity was larger than the warpage without crystallinity, especially in the parts
molded by RHCM. The proposed method was accurate and effective. It was a potential
candidate technology for quantitatively predicting the warpage of plate parts and optimiz-
ing the molding process for manufacturing. Poszwa et al. [
26
] investigated the influence
of RHCM on the basic parameters of filling the cavity using numerical analysis. Obtained
results showed strong nonlinear relations between maximum flow length, part thickness,
and volumetric flow rate. Whereas the relation between flow length, injection pressure,
and cavity surface temperature was linear.
Liparoti et al. [
27
] carried out the thermal transient simulation with very thin mul-
tilayer heating devices layered on the cavity surface for an injection molding process. A
conductive layer made these thin heating devices between two insulating layers with thick-
Polymers 2022,14, 3181 3 of 15
nesses. They were layered on the cavity surface, allowing temperature evolution between
injection and cooling channel’s temperatures to be as fast as possible. The results of the
simulations (temperature and pressure distribution evolutions) were compared with exper-
imental results and were successfully justified. An increase in the mold temperature and a
high mold temperature reduced the viscosity of the plastic entering the mold cavity. A better
fluidity reduced the forming pressure and the clamping force. However, the time required
for the plastic to achieve ejection temperature from the melting temperature was inevitably
increased as the mold temperature and the forming cycle time increased.
Bianchi et al. [28]
compared a novel approach based on cooling rate optimization with RHCM techniques in
ceramic injection molding. Results showed that the new method emerged with the benefits
of higher dimensional control and reduction of differential shrinkage compared to the other
analyzed approaches. This resulted in an increased capability to use injection molding
to manufacture ceramic components characterized by non-uniform wall thickness. Cho
et al. [
29
] designed a 3D printed insert core to improve weld line defects on an automotive
crash pad with a high standard of appearance by local heating and cooling. Results showed
that it is more efficient than other RHCM techniques because the 3D printed insert core
does not need additional equipment or high energy consumption. Kitayama et al. [
30
]
adopted a radial basis function network to determine the optimal multi-objective process
parameters in rapid heat cycle molding (RHCM) for improving the weld line, clamping
force, and cycle time. The numerical and experimental results clarified that the weld line re-
duction could be achieved by the proposed RHCM.
Fu et al. [31]
proposed a novel ejection
criteria model based on the partial solidification for early ejection in plastic part molding.
They investigated the general time determination model targeting to lessen the cycle time.
They compared the traditional ejection criterion of the fully solidified by in-mold cooling.
The results revealed that the cycle time could be decreased significantly. Nevertheless,
increasing the mold temperature will prolong the molding time required for the plastic
part (the plastic part must be cooled to the ejection temperature in the mold before the
mold can be opened), resulting in unnecessary costs. Poszwa et al. [
32
] investigated the
injection molded flexible hinge parts manufactured with selective induction heating to
improve their properties. The linear relation between the number of cycles the hinges can
withstand, mold temperature, and injection time was identified. The mold temperature
was a more significant factor. Monti et al. [
33
] studied the influences of distinct ethylene
copolymers in raising the collision strength of a fiber-reinforced composites based on a
recycled rPET from post-consumer bottles. This research indicated that a post-consumer
PET from city waste could be utilized as a high-performance pattern. Injection-molded
composites are appropriate for application in the automotive sector with no agreement
regarding mechanical demands or thermal steadiness.
Verma et al. [34]
first designed dif-
ferent lattice structures in a CAD environment. The strength of the subsequent lattice-resin
interlock was predicted using the finite element analysis (FEA) method. Individual stress
status of lattice and resin during the tensile test were investigated to determine the failure
strength of lattice-resin interlock. FEA predicted failure strength was correlated with the
experimental result with reasonable deviations. Xu et al. [
35
] presented a detailed study on
the compression-molding process of micro-grooves on the carbon fiber-reinforced plastic
(CFRP) surface. They successfully obtained the appropriate parameters. The experimental
results showed that the micro-groove array structures on the CFRP surface could effectively
improve the composite parts’ tensile strength of the connection interface.
These general defects were often discovered on the external appearances of welding
lines. They are conformation shortcomings and also lower the mechanical intensity of the
assemblies. A welding line may be taking shape for the plastics by moving around the
inserts as the metal embeds were put in the mold for injection molding. Conventionally, the
inserts were placed in the mold at the surrounding temperature, yet the inserts’ temperature
was inferior to that of the mold, as the filling was executed due to mold sealing. Therefore,
this paper attempted to design and present a set of local rapid heating mechanisms (e.g.,
RHCM and VCRHCS) at the meeting point of the welding line of the molded product. The
Polymers 2022,14, 3181 4 of 15
design considered the procedure parameters and effect on the quality of goods and used the
local increase of the mold temperature to lower the viscosity of the plastic. This is because
the plastic can heighten the fluidity of the plastic when it meets, and the welding line traces
can be eliminated. Throughout this study, the procedure parameters, reaction, the material
employed, and the technology applied to the best research in the field of injection molding
were highlighted.
2. Methodology and Materials
The experimental framework of this study was divided into four categories: heating
mechanism design, temperature measurement and heat transfer simulation, welding line
strength experiment, and welding line appearance experiment. First, a heating mech-
anism was designed by lever contact and separation with the VC (vapor chamber) for
the temperature measurement. The results were compared and verified with the CFD
simulation analysis. Tensile test pieces and holes in flat mold cores were used to make
test specimens employing an injection molding machine. They were subjected to tensile
tests, appearance observation, and SEM (scanning electron microscope) microstructure
observation. Figure 1displays the complete experimental architecture diagram. Figure 2
displays a vapor chamber (VC) [
36
,
37
] with superior thermal performance and a two-phase
(vapor–liquid) heat transfer device [
38
]. High-performance servers, high-end VGA, and
high-power LEDs were employed [
39
,
40
]. The general operating fundamental of a vapor
chamber is explained. The inside of the VC has a vacuum, and then the working fluid
will be quickly converted into vapor by boiling or evaporation after the wall face of the
VC cavity assimilates the heat from the heat source [
41
–
43
]. Finally, the vapors will be
condensed into liquid because of the cooling resulting from the heat convection on the
external barrier of the VC cavity and restream to the area of the heat origin along the wick
structure [
44
,
45
]. Therefore, VC propagates huge heat capacity speedily and is achievable to
be adopted in insert molding manufacture. The metal insert was put into the mold initially
and fabricated into inserted plastic goods via injection molding [
46
,
47
]. The dimensions of
the VC employed in this study were 80
×
50
×
4 mm
3
with a porosity of 0.46 and the lowest
thermal resistance of 0.15
◦
C/W. The goods can be created in a single molding procedure,
reducing the processing time and decreasing the possible manual mistakes emerging from
some processes.
The installation of VCRHCS adopted a vapor chamber to promote the heating and
cooling apparatus for the injection molding procedure, as shown in Figure 3. A current
heating structure of the VC required that the mold have a movable slider at the interior
area installed with two heating rods. The VC was fixed at the union of the front side of the
slider and the mold barrier. The mold temperature was increased upon the glass transition
temperature of the plastic before the filling phase. Then, the cooling of the mold was
initiated at the packing phase. The operation sequence of VCRHCS is that the heated slider
will move ahead and touch the VC. As the embeds are placed in the mold, the mold is
locked, and the inserts are warmed instantly with the VC. Subsequently, the heating cycle
is operated by a pedal mechanism composed of a hydraulic cylinder. It presses the VC to
touch the mold at the filling phase. A heating and cooling apparatus with VC was exploited
in the present study. A VC was mounted between the heating block and the mold cavity.
The dimensions of the heat source of VCRHCS were 50
×
50
×
80 mm
3
. It can be combined
with the mold in any situation, regardless of the mold’s magnitude. The mold steel block of
P20 was heated by heating rods constituted with two electrical heating tubes. These tubes
touched VC when the pedal was functioning, and the T-type thermocouples were inserted
for recording the temperatures of the facilities. The heat source was disconnected from the
VC when the filling was accomplished.
Polymers 2022,14, 3181 5 of 15
Polymers 2022, 14, x FOR PEER REVIEW 5 of 15
Processes
CFD simulation Experiment
Vapor Chamber Temperature-Time curve
VCRHCS Mold design
Strength Appearance
Tensile specimens Welding lines
Observation Product Verify
Tensile tests
Figure 1. Experimental architecture diagram.
Figure 2. Photo of vapor chamber (VC).
Figure 1. Experimental architecture diagram.
Polymers 2022, 14, x FOR PEER REVIEW 5 of 15
Processes
CFD simulation Experiment
Vapor Chamber Temperature-Time curve
VCRHCS Mold design
Strength Appearance
Tensile specimens Welding lines
Observation Product Verify
Tensile tests
Figure 1. Experimental architecture diagram.
Figure 2. Photo of vapor chamber (VC).
Figure 2. Photo of vapor chamber (VC).
Polymers 2022,14, 3181 6 of 15
Polymers 2022, 14, x FOR PEER REVIEW 6 of 15
The installation of VCRHCS adopted a vapor chamber to promote the heating and
cooling apparatus for the injection molding procedure, as shown in Figure 3. A current
heating structure of the VC required that the mold have a movable slider at the interior
area installed with two heating rods. The VC was fixed at the union of the front side of
the slider and the mold barrier. The mold temperature was increased upon the glass
transition temperature of the plastic before the filling phase. Then, the cooling of the mold
was initiated at the packing phase. The operation sequence of VCRHCS is that the heated
slider will move ahead and touch the VC. As the embeds are placed in the mold, the mold
is locked, and the inserts are warmed instantly with the VC. Subsequently, the heating
cycle is operated by a pedal mechanism composed of a hydraulic cylinder. It presses the
VC to touch the mold at the filling phase. A heating and cooling apparatus with VC was
exploited in the present study. A VC was mounted between the heating block and the
mold cavity. The dimensions of the heat source of VCRHCS were 50 × 50 × 80 mm3. It can
be combined with the mold in any situation, regardless of the mold’s magnitude. The
mold steel block of P20 was heated by heating rods constituted with two electrical heating
tubes. These tubes touched VC when the pedal was functioning, and the T-type
thermocouples were inserted for recording the temperatures of the facilities. The heat
source was disconnected from the VC when the filling was accomplished.
Figure 3. Mechanisms of heating and cooling cycle system with Vapor chamber (VCRHCS).
In addition, Figure 3 revealed five thermocouples arranged on the outside of the
cavity for gauging the temperatures of the vapor chamber. The central temperature of the
cavity and VC was metered at Point O. The temperatures of the opponent to the locations
Figure 3. Mechanisms of heating and cooling cycle system with Vapor chamber (VCRHCS).
In addition, Figure 3revealed five thermocouples arranged on the outside of the cavity
for gauging the temperatures of the vapor chamber. The central temperature of the cavity
and VC was metered at Point O. The temperatures of the opponent to the locations of the
heat embed apparatus and VC on the outside of the cavity were metered by Points A and B
and Points C and D, respectively. Point C was the farthest from point O. The photograph of
the whole heating and cooling apparatus is shown in Figure 4. The weight of this mold of
VCRHCS is over several hundred kilograms. The magnitude and capacity of the heating
and cooling system can be altered to adapt to the mold. In this experimentation, the plastic
was ABS (Chi-Mei PA-758) with a glass transition temperature of 109
◦
C. The mold base and
mold core materials were JIS S50C and ASSAB 718, respectively. There were two injection
molds judged the flat goods utilizing VC, and the testing material was ABS. The VCRHCS
can enhance the tensile intensity and decrease the flaw of welding lines of plastic goods
because of fast and consistent heating and cooling recurrence with VC.
Polymers 2022,14, 3181 7 of 15
Polymers 2022, 14, x FOR PEER REVIEW 7 of 15
of the heat embed apparatus and VC on the outside of the cavity were metered by Points
A and B and Points C and D, respectively. Point C was the farthest from point O. The
photograph of the whole heating and cooling apparatus is shown in Figure 4. The weight
of this mold of VCRHCS is over several hundred kilograms. The magnitude and capacity
of the heating and cooling system can be altered to adapt to the mold. In this
experimentation, the plastic was ABS (Chi-Mei PA-758) with a glass transition
temperature of 109 °C. The mold base and mold core materials were JIS S50C and ASSAB
718, respectively. There were two injection molds judged the flat goods utilizing VC, and
the testing material was ABS. The VCRHCS can enhance the tensile intensity and decrease
the flaw of welding lines of plastic goods because of fast and consistent heating and
cooling recurrence with VC.
(a) Right side (b) Left side
Figure 4. Actual photograph of this mold of VCRHCS.
Before the VCRHCS experimental verification, the VC thermal performance of CFD
(computational fluid dynamics) simulation analysis, in which fluid mechanics, discrete
mathematics, numerical method, and computer technology were integrated by applying
computer-aided design (CAD) and analytical software tools (Ansys Icepak 2022R1,
Canonsburg, PA, USA). The relationships of the rapid uniform temperature
characteristics at unsteady state conditions were coordinated to predict and control the
heat source temperatures during the heating stage. Figure 5 demonstrates the simulation
analytical models of the present device. Figure 5a shows a no vapor chamber system
meaning that the heat source directly touched the P20 mold. Figure 5b is a VC system.
Consequently, the VC was placed between the heat source and P20 mold. The heat flow
field of VC was simulated transiently through numerical analysis, and a contrast was
depicted between the experimental and simulation results. The numerical analysis
procedure in this simulation can be separated into pre-processing, numerical solving, and
post-processing. They had the same simulation conditions, power, and size of the heat
source. All conditions of CFD models were the same except when using VC or not. CFD
can reduce many costs of manufacturing and rapid design. It can verify the thermal
performance of VC within a short period. The entire simulation analysis range was 250 ×
150 × 150 mm3. The dimension and input power of the thermal source were 20 × 25 mm2
Figure 4. Actual photograph of this mold of VCRHCS.
Before the VCRHCS experimental verification, the VC thermal performance of CFD
(computational fluid dynamics) simulation analysis, in which fluid mechanics, discrete
mathematics, numerical method, and computer technology were integrated by apply-
ing computer-aided design (CAD) and analytical software tools (Ansys Icepak 2022R1,
Canonsburg, PA, USA). The relationships of the rapid uniform temperature characteris-
tics at unsteady state conditions were coordinated to predict and control the heat source
temperatures during the heating stage. Figure 5demonstrates the simulation analytical
models of the present device. Figure 5a shows a no vapor chamber system meaning that
the heat source directly touched the P20 mold. Figure 5b is a VC system. Consequently,
the VC was placed between the heat source and P20 mold. The heat flow field of VC was
simulated transiently through numerical analysis, and a contrast was depicted between the
experimental and simulation results. The numerical analysis procedure in this simulation
can be separated into pre-processing, numerical solving, and post-processing. They had
the same simulation conditions, power, and size of the heat source. All conditions of CFD
models were the same except when using VC or not. CFD can reduce many costs of man-
ufacturing and rapid design. It can verify the thermal performance of VC within a short
period. The entire simulation analysis range was 250
×
150
×
150 mm
3
. The dimension
and input power of the thermal source were 20
×
25 mm
2
and 130
◦
C, respectively. The
size of VC was 80
×
50
×
5 mm
3
with a thermal conductivity of 700 W/mk, density of
8900 kg/m
3
, and specific heat of 2.283 kJ/kg
◦
C. The size of P20 plastic mold steel (ASSAB
718) was 160
×
80
×
50 mm
3
, which had a better thermal conductivity of 29.5 W/mk. The
boundary conditions and physical heat properties involved the environmental temperature
of 23
◦
C. The whole simulation analysis model was a transient situation from 0 to 60 s.
There were about 1500 thousand grid elements, a 0.01 s time step, and 200 iterations in the
present study. Each simulation took about 4 h.
Polymers 2022,14, 3181 8 of 15
Polymers 2022, 14, x FOR PEER REVIEW 8 of 15
and 130 °C, respectively. The size of VC was 80 × 50 × 5 mm3 with a thermal conductivity
of 700 W/mk, density of 8900 kg/m3, and specific heat of 2.283 kJ/kg°C. The size of P20
plastic mold steel (ASSAB 718) was 160 × 80 × 50 mm3, which had a better thermal
conductivity of 29.5 W/mk. The boundary conditions and physical heat properties
involved the environmental temperature of 23 °C. The whole simulation analysis model
was a transient situation from 0 to 60 s. There were about 1500 thousand grid elements, a
0.01 s time step, and 200 iterations in the present study. Each simulation took about 4 h.
(a) Without VC
(b) With VC
Figure 5. CFD simulation models.
3. Results and Discussions
Figure 6 reveals top to bottom temperature transfer changes for the simulation results
of the heat transfer between the process with a vapor chamber and the process without a
VC at 1, 20, 40, and 60 s, respectively. At the beginning of heating at 1 s, the rapid uniform
temperature characteristic of VC was demonstrated. The ranges of heat transfer using a
VC were larger than that of the case without the VC, and the temperature distributions
were also relatively uniform from the temperature lines and colors distribution. The
simulation results of the two points of A and B were all 82 °C at 60 s with VC. The
temperatures of the two points of A and B were all 51 °C at 60 s without VC. Figure 7
displayed the temperature profiles of 0 to 60 s with VC and without VC. The temperatures
of Point O and the farthest side from Point O to point C were 74 °C and 35 °C under no
Figure 5. CFD simulation models.
3. Results and Discussions
Figure 6reveals top to bottom temperature transfer changes for the simulation results
of the heat transfer between the process with a vapor chamber and the process without a
VC at 1, 20, 40, and 60 s, respectively. At the beginning of heating at 1 s, the rapid uniform
temperature characteristic of VC was demonstrated. The ranges of heat transfer using a VC
were larger than that of the case without the VC, and the temperature distributions were
also relatively uniform from the temperature lines and colors distribution. The simulation
results of the two points of A and B were all 82
◦
C at 60 s with VC. The temperatures of the
two points of A and B were all 51
◦
C at 60 s without VC. Figure 7displayed the temperature
profiles of 0 to 60 s with VC and without VC. The temperatures of Point O and the farthest
side from Point O to point C were 74
◦
C and 35
◦
C under no VC and 60 s. Moreover, the
temperature variances of the other points of A, B, and D were great morals around 10
◦
C
each other at 60 s and without VC. However, the temperatures of Point O and Point C
were separately 84
◦
C and 68
◦
C at 60 s with VC. Moreover, the temperatures of the other
points of A, B, and D were nearly 80
◦
C at 60 s with VC (simulation results of 82
◦
C). The
temperature profile of Point O without VC was raised faster than that with VC between 0 s
to 30 s due to the heater’s immediate touch but decelerated after 30 s. Point O reveals the
central temperature of the cavity and VC. In summary, the temperature of Point O without
VC was higher than with VC before 30 s. However, the slope of the temperature of Point O
with VC was high than that of Point O without VC. The mean temperatures of these five
Polymers 2022,14, 3181 9 of 15
points with VC and without VC were 78
◦
C and 56
◦
C based on the experimental results.
In the simulation results they were 81
◦
C and 60
◦
C, separately. The high-speed uniform
temperature influence of the employed VC heating system (VCRHCS) was beneficial,
although the heater touched Point O on the outside of cavity with no VC apparatus.
Polymers 2022, 14, x FOR PEER REVIEW 9 of 15
VC and 60 s. Moreover, the temperature variances of the other points of A, B, and D were
great morals around 10 °C each other at 60 s and without VC. However, the temperatures
of Point O and Point C were separately 84 °C and 68 °C at 60 s with VC. Moreover, the
temperatures of the other points of A, B, and D were nearly 80 °C at 60 s with VC
(simulation results of 82 °C). The temperature profile of Point O without VC was raised
faster than that with VC between 0 s to 30 s due to the heater’s immediate touch but
decelerated after 30 s. Point O reveals the central temperature of the cavity and VC. In
summary, the temperature of Point O without VC was higher than with VC before 30 s.
However, the slope of the temperature of Point O with VC was high than that of Point O
without VC. The mean temperatures of these five points with VC and without VC were
78 °C and 56 °C based on the experimental results. In the simulation results they were 81
°C and 60 °C, separately. The high-speed uniform temperature influence of the employed
VC heating system (VCRHCS) was beneficial, although the heater touched Point O on the
outside of cavity with no VC apparatus.
Figure 6. CFD simulation results.
Figure 6. CFD simulation results.
Two distinct mold designs, including one gate mold and two opposite gates mold in
the present experiments, applied VCRHCS in tensile testing pieces, as shown in Figure 8.
The tensile test samples were one and two gates, as shown in Figure 8a. The parts of
the injection molding experimentations were tensile inspecting pieces. They assessed the
successfulness of the heating and cooling system accompanied by a vapor chamber with no
VC. The welding line was in the central position, and the tensile sectional area was smooth,
as shown in Figure 8b,c. However, the cut sectional area was sharp for one gate tensile
testing piece because there was no welding line in the central place. as shown in Figure 8d.
Figure 9exhibited testing pieces SEM images of welding line and the relationships of the
temperatures with the heating time with/without VC. If there were no influence of VC,
these welding lines are clearly displayed under the SEM photographs in Figure 9a. One
gate piece had no welding line in the central position, as shown in Figure 9d. Raise the
heating temperature, less obvious the welding line for using the VCRHCS. Figure 9b had
a slight welding line at a heating temperature of 75
◦
C. Figure 9c had almost no welding
line at a heating temperature of 110
◦
C. The dimensions of these tensile testing pieces were
215.9 ×12.7 ×25.4 mm3with a thickness of 3.175 mm. Table 1shows the tensile intensity
of the testing pieces in the distinct status of one gate and two opposite gates with and
without VC and a 0.5% error. The tensile intensity theorizes the highest value for the one
gate system due to no welding line in the central place from Figure 9d. There were no
defects of welding lines in the tensile testing pieces from the no VC one gate system. The
two gates with no VC heating apparatus showed obvious welding lines. Its tensile intensity
dropped by 11.1%, more than the piece with one gate from Table 1and Figure 9. The two
Polymers 2022,14, 3181 10 of 15
gates with VC heating apparatus showed a tiny welding line, and its tensile intensity of
testing piece was better, at 6.8%, than the piece with two gates and no VC apparatus. By
raising the warming temperature from 75
◦
C to 110
◦
C on the piece with two gates and a
VC apparatus, the tensile intensity increases by 3.2%. This is because the VC can dissipate
heat rapidly and uniformly transfers heat to the molding steel of P20. The regional increase
of the mold temperature lowers the viscosity of the fluidic plastic, and the plastic could
ameliorate the fluidity and the welding line marks could be extirpated.
Polymers 2022, 14, x FOR PEER REVIEW 10 of 15
Figure 7. Relations of the temperatures with the heating time with/without vapor chamber.
Two distinct mold designs, including one gate mold and two opposite gates mold in
the present experiments, applied VCRHCS in tensile testing pieces, as shown in Figure 8.
The tensile test samples were one and two gates, as shown in Figure 8a. The parts of the
injection molding experimentations were tensile inspecting pieces. They assessed the
successfulness of the heating and cooling system accompanied by a vapor chamber with
no VC. The welding line was in the central position, and the tensile sectional area was
smooth, as shown in Figure 8b,c. However, the cut sectional area was sharp for one gate
tensile testing piece because there was no welding line in the central place. as shown in
Figure 8d. Figure 9 exhibited testing pieces SEM images of welding line and the
relationships of the temperatures with the heating time with/without VC. If there were no
influence of VC, these welding lines are clearly displayed under the SEM photographs in
Figure 9a. One gate piece had no welding line in the central position, as shown in Figure
9d. Raise the heating temperature, less obvious the welding line for using the VCRHCS.
Figure 9b had a slight welding line at a heating temperature of 75 °C. Figure 9c had almost
no welding line at a heating temperature of 110 °C. The dimensions of these tensile testing
Figure 7. Relations of the temperatures with the heating time with/without vapor chamber.
Polymers 2022,14, 3181 11 of 15
Polymers 2022, 14, x FOR PEER REVIEW 11 of 15
pieces were 215.9 × 12.7 × 25.4 mm3 with a thickness of 3.175 mm. Table 1 shows the tensile
intensity of the testing pieces in the distinct status of one gate and two opposite gates with
and without VC and a 0.5% error. The tensile intensity theorizes the highest value for the
one gate system due to no welding line in the central place from Figure 9d. There were no
defects of welding lines in the tensile testing pieces from the no VC one gate system. The
two gates with no VC heating apparatus showed obvious welding lines. Its tensile
intensity dropped by 11.1%, more than the piece with one gate from Table 1 and Figure 9.
The two gates with VC heating apparatus showed a tiny welding line, and its tensile
intensity of testing piece was better, at 6.8%, than the piece with two gates and no VC
apparatus. By raising the warming temperature from 75 °C to 110 °C on the piece with
two gates and a VC apparatus, the tensile intensity increases by 3.2%. This is because the
VC can dissipate heat rapidly and uniformly transfers heat to the molding steel of P20.
The regional increase of the mold temperature lowers the viscosity of the fluidic plastic,
and the plastic could ameliorate the fluidity and the welding line marks could be
extirpated.
(a) One gate/two opposite gates mold
(b) Production of two opposite gates mold with vapor chamber
(c) Smooth sectional area (d) Sharp sectional area
Figure 8. One gate mold with no VCRHCS and two gates mold with VCRHCS.
Figure 8. One gate mold with no VCRHCS and two gates mold with VCRHCS.
Polymers 2022, 14, x FOR PEER REVIEW 12 of 15
(a) (b)
(c) (d)
Figure 9. SEM photographs of one gate and two opposite gates. (a) Two opposite gates under Point
O at 75 °C and with no VC apparatus. (b) Two opposite gates under Point O at 75 °C and with VC
apparatus. (c) Two opposite gates under Point O at 110 °C and with VC apparatus. (d) One gate
under Point O at 75 °C and with no VC apparatus.
Table 1. The achievements of the tensile examination.
Requirement Max. Stretch Tension (Kgf/cm2) Intensity (%)
Two gates, no VC
Cavity temp. = 75 °C 165 88.9
Two gates, with VC
Cavity temp. = 75 °C 178 95.7
Two gates, with VC
Cavity temp. = 110 °C 184 98.9
One gate, no VC
Cavity temp. = 75 °C 186 100.0
Another testing multi-hole specimen was applied VCRHCS in eight holes pieces to
assess the successfulness of the system with vapor chamber in the distinct status of cavity
and core temperatures. These multi-hole pieces had eight holes with four 10 mm and 5
mm diameter holes, separately. The dimensions of the eight holes pieces were 110 × 53 ×
3.175 mm3, as shown in Figure 10. Three temperature associations (60 °C, 80 °C, and 130
°C) were evaluated in the present experiments. Case 1 was the requirement of a cavity
temperature of 60 °C and core temperature of 60 °C. Case 2 was the requirement of a cavity
temperature of 60 °C and core temperature of 130 °C. Case 3 was the requirement of a
cavity temperature of 80 °C and core temperature of 130 °C. Figure 10 illustrates the
criterion of the eight holes testing piece and the SEM images of the V-notch. There were
many welding lines on the appearance of the diaphanous pieces, especially in Case 1 of
Figure 10a. The V-gap was deeper than the welding line and was more evident for
transparent products. The depths of the V-gap seen in every case were 12 μm, 2 μm, and
0.5 μm. The piece from Case 1 exhibited a V-notch 24 times deeper than the piece from
Case 3. The effects of cavity and core temperatures were also significant for the welding
line when adopting the VCRHCS in the present work. Finally, employing VCRHCS
demonstrated that the temperature distinctions of cavity adopting VC were smaller than
that without VC. Raising preheating temperature can increase the tensile intensity for two
opposite gates due to elongating sufficient fluid stream and reducing the fluid’s viscosity.
Figure 9.
SEM photographs of one gate and two opposite gates. (
a
) Two opposite gates under Point
O at 75
◦
C and with no VC apparatus. (
b
) Two opposite gates under Point O at 75
◦
C and with VC
apparatus. (
c
) Two opposite gates under Point O at 110
◦
C and with VC apparatus. (
d
) One gate
under Point O at 75 ◦C and with no VC apparatus.
Another testing multi-hole specimen was applied VCRHCS in eight holes pieces
to assess the successfulness of the system with vapor chamber in the distinct status of
cavity and core temperatures. These multi-hole pieces had eight holes with four 10 mm
and 5 mm diameter holes, separately. The dimensions of the eight holes pieces were
110 ×53 ×3.175 mm3
, as shown in Figure 10. Three temperature associations (60
◦
C,
Polymers 2022,14, 3181 12 of 15
80
◦
C, and 130
◦
C) were evaluated in the present experiments. Case 1 was the requirement
of a cavity temperature of 60
◦
C and core temperature of 60
◦
C. Case 2 was the requirement
of a cavity temperature of 60
◦
C and core temperature of 130
◦
C. Case 3 was the requirement
of a cavity temperature of 80
◦
C and core temperature of 130
◦
C. Figure 10 illustrates the
criterion of the eight holes testing piece and the SEM images of the V-notch. There were
many welding lines on the appearance of the diaphanous pieces, especially in Case 1
of Figure 10a. The V-gap was deeper than the welding line and was more evident for
transparent products. The depths of the V-gap seen in every case were 12
µ
m, 2
µ
m,
and 0.5
µ
m. The piece from Case 1 exhibited a V-notch 24 times deeper than the piece
from Case 3. The effects of cavity and core temperatures were also significant for the
welding line when adopting the VCRHCS in the present work. Finally, employing VCRHCS
demonstrated that the temperature distinctions of cavity adopting VC were smaller than
that without VC. Raising preheating temperature can increase the tensile intensity for two
opposite gates due to elongating sufficient fluid stream and reducing the fluid’s viscosity.
The novel VCRHCS can effectively lessen the deepness of the V-gap by 24 times, resulting
in the rapid uniform temperature characteristic of VC in this paper.
Table 1. The achievements of the tensile examination.
Requirement Max. Stretch Tension (Kgf/cm2)Intensity (%)
Two gates, no VC
Cavity temp. = 75 ◦C165 88.9
Two gates, with VC
Cavity temp. = 75 ◦C178 95.7
Two gates, with VC
Cavity temp. = 110 ◦C184 98.9
One gate, no VC
Cavity temp. = 75 ◦C186 100.0
Polymers 2022, 14, x FOR PEER REVIEW 13 of 15
The novel VCRHCS can effectively lessen the deepness of the V-gap by 24 times, resulting
in the rapid uniform temperature characteristic of VC in this paper.
(a) Case 1 (b) Case 2 (c) Case 3
(d) Specification of the eight holes testing example
Figure 10. SEM photographs of the eight holes plate.
4. Conclusions
This study employing a VCRHCS (Vapor Chamber for Rapid Heating and Cooling
System) certified that the inserts’ temperature values and distributions significantly
impact the finishing and gathering strengths of goods among existing insert molding
procedures. The rapid uniform temperature distributions of the inserts mold were
consistent and verified between the experimental and CFD simulation results. Moreover,
a VCRHCS with rapid uniform heating and cooling cycle was able to successfully lower
the defects of the welding lines of transparent plastic goods. It was even able to enhance
the tensile strength of injection molding products. The hydraulic cylinder controlled a
pedal mechanism to push the VC down to touch the mold during the filling phase while
heating. The heating temperature of the mold should not only reach the glass transition
temperature of the ABS plastic material (Chi-Mei PA-758, 109 °C) but should have a better
effect on eliminating the bonding line at a higher temperature (over 109 °C).
The simulation results were consistent with experimental results for the thermal
performance of VC. The experimental results indicated that the depths of the welding line
of the testing pieces with eight holes in the plastic plate were reduced from 12 μm to 0.5
μm. The tensile strengths of the other plastic testing pieces with two opposite gates were
enhanced to 6.8% and 10% compared to the conventional goods. The tensile intensity of
the testing piece with two gates and VC heating was only smaller by 1% than the piece
with one gate. Installing the VCRHCS on both the male and female mold sides was
effective in lowering the defects of the welding lines and accomplishing giant material
strength than on one side only. In the process of experiments and transient simulations in
Figure 10. SEM photographs of the eight holes plate.
Polymers 2022,14, 3181 13 of 15
4. Conclusions
This study employing a VCRHCS (Vapor Chamber for Rapid Heating and Cooling
System) certified that the inserts’ temperature values and distributions significantly impact
the finishing and gathering strengths of goods among existing insert molding procedures.
The rapid uniform temperature distributions of the inserts mold were consistent and
verified between the experimental and CFD simulation results. Moreover, a VCRHCS with
rapid uniform heating and cooling cycle was able to successfully lower the defects of the
welding lines of transparent plastic goods. It was even able to enhance the tensile strength
of injection molding products. The hydraulic cylinder controlled a pedal mechanism to
push the VC down to touch the mold during the filling phase while heating. The heating
temperature of the mold should not only reach the glass transition temperature of the ABS
plastic material (Chi-Mei PA-758, 109
◦
C) but should have a better effect on eliminating the
bonding line at a higher temperature (over 109 ◦C).
The simulation results were consistent with experimental results for the thermal
performance of VC. The experimental results indicated that the depths of the welding
line of the testing pieces with eight holes in the plastic plate were reduced from 12
µ
m to
0.5
µ
m. The tensile strengths of the other plastic testing pieces with two opposite gates
were enhanced to 6.8% and 10% compared to the conventional goods. The tensile intensity
of the testing piece with two gates and VC heating was only smaller by 1% than the piece
with one gate. Installing the VCRHCS on both the male and female mold sides was effective
in lowering the defects of the welding lines and accomplishing giant material strength than
on one side only. In the process of experiments and transient simulations in this study, it
can be concluded that the use of VC for injection molding mold heating and cooling is
better than the unused cases in this research.
Author Contributions:
Conceptualization, J.-C.W.; Data curation, R.-T.W. and J.-C.W.; Investigation,
J.-C.W. and R.-T.W.; Methodology, J.-C.W.; Supervision, R.-T.W. and S.-L.C. All authors have read and
agreed to the published version of the manuscript.
Funding: This research received no external funding.
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement:
All data are offered by the authors on reasonable request and the
VCRHCS are available from the authors.
Conflicts of Interest: The authors declare no conflict of interest.
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