**Insert Molding Process Employing Vapour Chamber**

Jung-Chang Wang1, Tien-Li Chang2 andYa-Wei Lee3 *1National Taiwan Ocean University, 2National Taiwan Normal University, 3National Defense University, Taiwan, R.O.C.* 

#### **1. Introduction**

Insert molding process is a simplified injection molding method that eliminates secondary processing and assembly. In this process, the metal inserts are firstly formed, and placed in the mold during injection molding (the metal inserts can be designed into a grooved pattern, allowing them to be connected closely with the plastics), and then the mold is closed for injection molding. Although insert molding process can greatly improve the assembly and manufacturing procedure, the joining of two materials is the main problem yet to be solved. Because the molten plastic drives the air out of the mold cavity from the vent resulting in welding lines of a plastic part during the filling step in an injection molding process, then there will be a V-notch formed between the plastic and the mold wall if the air cannot exhaust before the melted plastic fronts meet. Thus, this chapter concerns about a V-notch found on the exterior surfaces of welding lines, which will form between the plastic and the mold wall. Not only are they appearance defects, but they also decrease the mechanical strength of the parts. Once the plastics are filled, the temperature of plastics bypassing one side of the inserts may decline more quickly than that of plastics contacting the temperature side of the mold wall, so a weld line may be formed when meeting again after bypassing the inserts. The strength at the position of weld line is generally lower than that at the region of plastics; moreover, the metal inserts are generally located at the stress region when the product is utilized. Hence, the rupture of plastics often occurs from the weld line at the rear of the metal inserts, leading to damage of products (Wang & Tsai 2011). The key approach is to rapidly and uniformly increase the temperature of inserts before the plastics enter into the mold cavity.

Some studies indicated that, during the injection molding process, the defect of weld line could be resolved by adjusting the mold temperature. The locations of the welding lines are usually decided by the part shapes and the gate locations. Welding lines can be eliminated by the following three methods. The first method is increasing the molten plastic temperature. The viscosity of the molten plastic fluid decreases with the increasing temperature, which improves the flow pattern of the plastic, and reduces the depth of the Vnotch of the welding lines. However, degradation of the material strength sometimes occurred if the melting temperature is too high. The second method is increasing the number of the vents. Increasing the number of the vents (eg. ejecting pin or inserts) at the

Insert Molding Process Employing Vapour Chamber 207

(a)

(b)

may regard as many thermal pins to heat spreading area. Wang et al. (2011a) uses the local heating mechanism, along with the excellent thermal performance of vapour chamber, to analyze and enhance the strength of products formed after insert molding process. Finally, it has been found that a vapour chamber based rapid heating and cooling system for injection mold is proposed for reducing the welding lines of the transparent plastic products and

Vapour has advantages of fast, large amount and safety. The effectiveness and better thermal performance of vapour chamber has been already confirmed according up-to-date researches and mass production application in server system and VGA thermal module. Moreover, vapour chamber-based thermal module has existed in the thermal-module industry for a year or so especially in server application (Wang & Chen 2009; Wang 2010; Wang et al. 2011b). A novel formula for effective thermal conductivity of vapour chamber has been developed by use of modified dimension analysis in combination with thermal-

Fig. 1. Heat pipe / thermal pin for mold cooling.

enhancing their strengths through these results.

vicinity of the welding line will dispel air from mold cavity more easily. Nevertheless, these extra vents will leave marks on the product surfaces, especially for transparent plastics. The third method is raising the mold temperature. Raising the mold temperature will increase the viscosity of the material, which in turn can reduce the depth of the V-notch. On the other hand, raised mold temperature also increases cycle time of the injection molding process, thus increases the production costs. If increased cycle time is not a problem then raise mold temperature is the simplest way for elimination of the welding lines among the three methods mentioned above.

There are several methods for raising the mold temperature. For example, replacing the water in the mold temperature controller for oil can increase the mold temperature for about 100°C. But the time required for the mold to rise to the designed temperature is too long to be practical. The mold heating is achieved by using high pressure vapour as a media in this method. When the filling stage in the injection molding process was finished, high pressure vapour was introduced for cooling. The technology does achieve a very fast heating and cooling cycle, however, its application was limited by the mold size. Wang et al. (2011a) demonstrated a vapour chamber of a two-phase flow heat transfer device consists of sealed container, wick structure and working fluid can occupy the technology easily. Its working theorem is as same as the heat pipe and generates high pressure vapour as the process of Rapid Heat Cycle Moulding (R.H.C.M.). Vapour chamber (V.C.) is verified through experiment and theory that the temperature difference between the center and edge of vapour chamber-based thermal module is within 1°C and this temperature difference for the copper Integral Heat Spreader (IHS) with the same size at the same experimental parameters are more than 6°C (Wang, 2011a). Therefore, vapour chamber represents better temperature homogeneity. In recent years, technical development related with the application of two-phase flow heat transfer assembly to thermal modules has become mature and heat pipe-based twophase flow heat transfer module is one of the best choices (Wang & Wang, 2011). The thermal performance of a heat sink with embedded heat pipes has been developed a Windows program for rapidly calculating through Visual Basic commercial software (Wang et al., 2010b). Moreover, one set of risers of the L-shape heat pipes were functioning as the evaporating section while the other set acted as condensing section. Six L-type heat pipes are arranged vertically in such a way that the bottom acts as the evaporating section and the risers act as the condensing section (Wang, 2011c). The temperature difference is under 1°C while the percentage of the non-condensation gas is less than 8 × 10-5%, and the single heat pipe has the maximum heat capacity (Wang, 2011b). To establish a practical quick methodology that can effectively and efficiently determine the thermal performances of heat pipes so as to substitute the use of the conventional steady-state test. This is much more efficient than the steady-state test and would be greatly beneficial to the notebook PC industry or other heat dissipation technologies that use heat pipes.

Fig. 1 showed a heat pipe / thermal pin employed in the injection molding process over several decades. Liquid thermoplastics require the cooling inside the injected cavity. The mold must be equipped to provide the cooling surroundings. Thermal pins had become standard components to cool areas that are difficult to reach with water lines. A commercially available thermal pin with heat conductivity several magnitudes higher than core, which accomplishes better cooling effect and more uniform temperature distribution. However, thermal pin is just only one-dimensional heat conducting path. Vapour chamber

vicinity of the welding line will dispel air from mold cavity more easily. Nevertheless, these extra vents will leave marks on the product surfaces, especially for transparent plastics. The third method is raising the mold temperature. Raising the mold temperature will increase the viscosity of the material, which in turn can reduce the depth of the V-notch. On the other hand, raised mold temperature also increases cycle time of the injection molding process, thus increases the production costs. If increased cycle time is not a problem then raise mold temperature is the simplest way for elimination of the welding lines among the three

There are several methods for raising the mold temperature. For example, replacing the water in the mold temperature controller for oil can increase the mold temperature for about 100°C. But the time required for the mold to rise to the designed temperature is too long to be practical. The mold heating is achieved by using high pressure vapour as a media in this method. When the filling stage in the injection molding process was finished, high pressure vapour was introduced for cooling. The technology does achieve a very fast heating and cooling cycle, however, its application was limited by the mold size. Wang et al. (2011a) demonstrated a vapour chamber of a two-phase flow heat transfer device consists of sealed container, wick structure and working fluid can occupy the technology easily. Its working theorem is as same as the heat pipe and generates high pressure vapour as the process of Rapid Heat Cycle Moulding (R.H.C.M.). Vapour chamber (V.C.) is verified through experiment and theory that the temperature difference between the center and edge of vapour chamber-based thermal module is within 1°C and this temperature difference for the copper Integral Heat Spreader (IHS) with the same size at the same experimental parameters are more than 6°C (Wang, 2011a). Therefore, vapour chamber represents better temperature homogeneity. In recent years, technical development related with the application of two-phase flow heat transfer assembly to thermal modules has become mature and heat pipe-based twophase flow heat transfer module is one of the best choices (Wang & Wang, 2011). The thermal performance of a heat sink with embedded heat pipes has been developed a Windows program for rapidly calculating through Visual Basic commercial software (Wang et al., 2010b). Moreover, one set of risers of the L-shape heat pipes were functioning as the evaporating section while the other set acted as condensing section. Six L-type heat pipes are arranged vertically in such a way that the bottom acts as the evaporating section and the risers act as the condensing section (Wang, 2011c). The temperature difference is under 1°C while the percentage of the non-condensation gas is less than 8 × 10-5%, and the single heat pipe has the maximum heat capacity (Wang, 2011b). To establish a practical quick methodology that can effectively and efficiently determine the thermal performances of heat pipes so as to substitute the use of the conventional steady-state test. This is much more efficient than the steady-state test and would be greatly beneficial to the notebook PC industry or other heat

Fig. 1 showed a heat pipe / thermal pin employed in the injection molding process over several decades. Liquid thermoplastics require the cooling inside the injected cavity. The mold must be equipped to provide the cooling surroundings. Thermal pins had become standard components to cool areas that are difficult to reach with water lines. A commercially available thermal pin with heat conductivity several magnitudes higher than core, which accomplishes better cooling effect and more uniform temperature distribution. However, thermal pin is just only one-dimensional heat conducting path. Vapour chamber

methods mentioned above.

dissipation technologies that use heat pipes.

Fig. 1. Heat pipe / thermal pin for mold cooling.

may regard as many thermal pins to heat spreading area. Wang et al. (2011a) uses the local heating mechanism, along with the excellent thermal performance of vapour chamber, to analyze and enhance the strength of products formed after insert molding process. Finally, it has been found that a vapour chamber based rapid heating and cooling system for injection mold is proposed for reducing the welding lines of the transparent plastic products and enhancing their strengths through these results.

Vapour has advantages of fast, large amount and safety. The effectiveness and better thermal performance of vapour chamber has been already confirmed according up-to-date researches and mass production application in server system and VGA thermal module. Moreover, vapour chamber-based thermal module has existed in the thermal-module industry for a year or so especially in server application (Wang & Chen 2009; Wang 2010; Wang et al. 2011b). A novel formula for effective thermal conductivity of vapour chamber has been developed by use of modified dimension analysis in combination with thermal-

Insert Molding Process Employing Vapour Chamber 209

single molding process, helping to shorten the processing time and reduce the possible human error arising from several procedures. These common defects are often found on the exterior surfaces of welding lines, which are not only appearance defects; they also decrease the mechanical strength of the parts. When the metal inserts are placed in the mold for injection molding, a weld line may be formed from the plastics after bypassing the inserts. Traditionally, the inserts are placed in the mold at room temperature, but the temperature of inserts is lower than that of the mold (the temperature of inserts cannot rise sharply within a

Fig. 2 reveals the apparatus of VC\_RHCS employing vapour chamber to rapid heating and cooling system for injection molding process. A local heating mechanism of vapour chamber proposed that the mold is a moveable slider, at inner side of which a heating rod is installed; a vapour chamber is mounted at the joint of the frontal edge of the slider and the mold wall. When the inserts are placed in the mold and the mold is closed, the heated slider will move forward, and contact the vapour chamber, so that the inserts are heated up rapidly and quickly with the vapour chamber. A heating and cooling system with vapour chamber was developed in this chapter. A vapour chamber was installed between the mold cavity and the heating block. The heating and cooling system used in the experiment was 50 x 50 x 80mm3. It can be incorporated with the mold at any location regardless of the mold size. The heating cycle is activated by a lever mechanism which pushes the vapour chamber to contact with the mold at the filling stage. The lever pusher is a hydraulic cylinder. Two electrical heating tubes are provided a mold steel block named P20 material and thermocouples are embedded to measure the temperature of the heat insert device. The heat source for vapour chamber is a low density cartridge heater which contact with the vapour chamber only when the lever is activated.

When the filling completed, the heat source separates form the vapour chamber.

Fig. 2. Mechanics of heating and cooling cycle system with vapour chamber (VC\_RHCS).

**Point O Point B** 

**Point A** 

**Point C** 

**Point D** 

There are five thermal couples placed on the surface of cavity to measure the temperature of vapour chamber as shown in Fig. 2. Points A and B are measured the temperatures of the opposite to the position of the heat insert device on the surface of cavity. Points C and D are measured the temperature of the opposite to the position of vapour chamber on the surface of cavity. Point O is measured the central temperature of cavity and vapour chamber. And

very short period) when the filling is conducted after mold sealing.

**2.1 Verification of VC\_RHCS** 

performance experimental method (Wang & Wang 2011). It is deduced from the novel formula that the maximum effective thermal conductivity is above 800 W/m°C, and comparing it with the experimental value, the calculating error is no more than ±5%. It respectively discussed these values of one, two and three-dimensional effective thermal conductivity and compared them with that of metallic heat spreader. For metallic materials as the heat spreaders, their thermal conductivities have constant values when the operating temperature is slight change. The thermal conductivities of pure cooper and aluminum as heat spreaders are 401 W/m°C and 237 W/m°C at operating temperature of 27 °C, respectively. When the operating temperature is 127 °C, they are 393 W/m°C and 240 W/m°C, respectively. The maximum heat flux of the vapour chamber is over 800,000 W/m2, and its effective thermal conductivity will increase with input power increasing. Thermal performance of V.C. is closely relate to its dimensions and heat-source flux, in the case of small area vapour chamber and small heat-source flux, the thermal performance will be less than that of pure copper material.

A vapour chamber is a two-phase heat transfer components with a function of spreading and transferring uniformly heat capacity so that it is ideal for use in non-uniform heating conditions especially in LEDs (Wang 2011d). The solid-state light emitting diode (SSLED) has attracted attention on outdoor and indoor lighting lamp in recent years. LEDs will be a great benefit to the saving-energy and environmental protection in the lighting lamps region. Wang et al. (2010a) introduce a thermal-performance experiment with the illumination-analysis method to discuss the green illumination techniques requesting on LEDs as solid-state luminescence source application in relative light lamps. The temperatures of LED dies are lower the lifetime of lighting lamps to be longer until many decades. The thermal performance of the LED vapour chamber-based plate (LED-VCPCB) is many times than that of LED copperand aluminium-based plates (Wang & Huang 2010; Wang 2011d). Wang et al. (2010a) utilizes experimental analysis with window program VCTM V1.0 to investigate the thermal performance of the vapour chamber and apply to 30 Watt high-power LEDs. Results show that the maximum effective thermal conductivity is 965 W/m°C at 187.5 W/cm2. Anyway, the chapter is divided into two parts; first part examines a vapour chamber to rapid heating and cooling system for injection molding process. Second part employs the vapour chamber system with numerical method and performance experiment to investigate the key factors affecting the performance of the Self-Contained Underwater Breathing Apparatus (SCUBA) system utilizing the insert molding process (Tsai et al. 2011).

### **2. Vapour chamber for rapid heating and cooling system (VC\_RHCS)**

Vapour Chamber (V.C.) is a two-phase heat transfer device inside vapour-liquid working, which has better thermal performance than metallic material in a large footprint heat sink. The overall operating principle of V.C. is defined as follows: at the very beginning, the interior of the vapour chamber is in the vacuum, after the wall face of the cavity absorbing the heat from its source, the working fluid in the interior will be rapidly transformed into vapour under the evaporating or boiling mechanism and fill up the whole interior of the cavity, and the resultant vapour will be condensed into liquid by the cooling action resulted from the heat convection effect between the fins and fan on the outer wall of the cavity, and reflow to the place of the heat source along the capillary structure. Thus, vapour chamber spreads large amount heat flow rapidly and is feasible to utilize in the insert molding process, which the metal insert is firstly placed into the mold, and then formed into an embedded plastic product by injection molding. Therefore, the products can be formed in a single molding process, helping to shorten the processing time and reduce the possible human error arising from several procedures. These common defects are often found on the exterior surfaces of welding lines, which are not only appearance defects; they also decrease the mechanical strength of the parts. When the metal inserts are placed in the mold for injection molding, a weld line may be formed from the plastics after bypassing the inserts. Traditionally, the inserts are placed in the mold at room temperature, but the temperature of inserts is lower than that of the mold (the temperature of inserts cannot rise sharply within a very short period) when the filling is conducted after mold sealing.

#### **2.1 Verification of VC\_RHCS**

208 Some Critical Issues for Injection Molding

performance experimental method (Wang & Wang 2011). It is deduced from the novel formula that the maximum effective thermal conductivity is above 800 W/m°C, and comparing it with the experimental value, the calculating error is no more than ±5%. It respectively discussed these values of one, two and three-dimensional effective thermal conductivity and compared them with that of metallic heat spreader. For metallic materials as the heat spreaders, their thermal conductivities have constant values when the operating temperature is slight change. The thermal conductivities of pure cooper and aluminum as heat spreaders are 401 W/m°C and 237 W/m°C at operating temperature of 27 °C, respectively. When the operating temperature is 127 °C, they are 393 W/m°C and 240 W/m°C, respectively. The maximum heat flux of the vapour chamber is over 800,000 W/m2, and its effective thermal conductivity will increase with input power increasing. Thermal performance of V.C. is closely relate to its dimensions and heat-source flux, in the case of small area vapour chamber and small heat-source flux, the thermal performance will be less

A vapour chamber is a two-phase heat transfer components with a function of spreading and transferring uniformly heat capacity so that it is ideal for use in non-uniform heating conditions especially in LEDs (Wang 2011d). The solid-state light emitting diode (SSLED) has attracted attention on outdoor and indoor lighting lamp in recent years. LEDs will be a great benefit to the saving-energy and environmental protection in the lighting lamps region. Wang et al. (2010a) introduce a thermal-performance experiment with the illumination-analysis method to discuss the green illumination techniques requesting on LEDs as solid-state luminescence source application in relative light lamps. The temperatures of LED dies are lower the lifetime of lighting lamps to be longer until many decades. The thermal performance of the LED vapour chamber-based plate (LED-VCPCB) is many times than that of LED copperand aluminium-based plates (Wang & Huang 2010; Wang 2011d). Wang et al. (2010a) utilizes experimental analysis with window program VCTM V1.0 to investigate the thermal performance of the vapour chamber and apply to 30 Watt high-power LEDs. Results show that the maximum effective thermal conductivity is 965 W/m°C at 187.5 W/cm2. Anyway, the chapter is divided into two parts; first part examines a vapour chamber to rapid heating and cooling system for injection molding process. Second part employs the vapour chamber system with numerical method and performance experiment to investigate the key factors affecting the performance of the Self-Contained Underwater Breathing Apparatus (SCUBA)

than that of pure copper material.

system utilizing the insert molding process (Tsai et al. 2011).

**2. Vapour chamber for rapid heating and cooling system (VC\_RHCS)** 

Vapour Chamber (V.C.) is a two-phase heat transfer device inside vapour-liquid working, which has better thermal performance than metallic material in a large footprint heat sink. The overall operating principle of V.C. is defined as follows: at the very beginning, the interior of the vapour chamber is in the vacuum, after the wall face of the cavity absorbing the heat from its source, the working fluid in the interior will be rapidly transformed into vapour under the evaporating or boiling mechanism and fill up the whole interior of the cavity, and the resultant vapour will be condensed into liquid by the cooling action resulted from the heat convection effect between the fins and fan on the outer wall of the cavity, and reflow to the place of the heat source along the capillary structure. Thus, vapour chamber spreads large amount heat flow rapidly and is feasible to utilize in the insert molding process, which the metal insert is firstly placed into the mold, and then formed into an embedded plastic product by injection molding. Therefore, the products can be formed in a Fig. 2 reveals the apparatus of VC\_RHCS employing vapour chamber to rapid heating and cooling system for injection molding process. A local heating mechanism of vapour chamber proposed that the mold is a moveable slider, at inner side of which a heating rod is installed; a vapour chamber is mounted at the joint of the frontal edge of the slider and the mold wall. When the inserts are placed in the mold and the mold is closed, the heated slider will move forward, and contact the vapour chamber, so that the inserts are heated up rapidly and quickly with the vapour chamber. A heating and cooling system with vapour chamber was developed in this chapter. A vapour chamber was installed between the mold cavity and the heating block. The heating and cooling system used in the experiment was 50 x 50 x 80mm3. It can be incorporated with the mold at any location regardless of the mold size. The heating cycle is activated by a lever mechanism which pushes the vapour chamber to contact with the mold at the filling stage. The lever pusher is a hydraulic cylinder. Two electrical heating tubes are provided a mold steel block named P20 material and thermocouples are embedded to measure the temperature of the heat insert device. The heat source for vapour chamber is a low density cartridge heater which contact with the vapour chamber only when the lever is activated. When the filling completed, the heat source separates form the vapour chamber.

Fig. 2. Mechanics of heating and cooling cycle system with vapour chamber (VC\_RHCS).

There are five thermal couples placed on the surface of cavity to measure the temperature of vapour chamber as shown in Fig. 2. Points A and B are measured the temperatures of the opposite to the position of the heat insert device on the surface of cavity. Points C and D are measured the temperature of the opposite to the position of vapour chamber on the surface of cavity. Point O is measured the central temperature of cavity and vapour chamber. And

Insert Molding Process Employing Vapour Chamber 211

gate mold and two opposite gates mold were selected for the experiments. Fig. 3 shows the relationships of the temperature with the heating time with/without vapour chamber. If there are no the effect of vapour chamber, these five thermal couples show non-uniform on the surface of cavity. However, the dimensions of these tensile testing parts are 215.9 x 12.7 x

Table 1 shows the tensile strength of the products in different situation of one gate and two opposite gates with and without vapour chamber. The tensile strength supposes maximum for one gate without vapour chamber heating system because of on welding line from the Fig. 4. Fig. 4 shows the test specimen and SEM images of welding line. One gate without vapour chamber system experiments resulted tensile test pars without any welding lines. Two gates without vapour chamber heating system appears apparent welding line and its tensile strength of testing part is lower 11.1% than the part of one gate from table 1 and Fig. 4.

(a) Different design for tensile test specimen

(c) Two opposite gates at the temperature of Point O is 75°C with

(e) One gate at the temperature of Point O is 75°C without vapour chamber system

vapour chamber system

25.4mm3 with 3.175mm thickness.

 (b) Two opposite gates at the temperature of Point O is 75°C without vapour chamber

 (d) Two opposite gates at the temperature of Point O is 110°C with vapour chamber

Fig. 4. SEM pictures of one gate and two opposite gates.

system

system

the point C is the farthest distance away from point O. Mold temperature was raised to above the glass transition temperature of the plastic before the filling stage. Cooling of the mold was then started at the beginning of the packing stage. The entire heating and cooling device was incorporated with the mold. The capacity and size of the heating and cooling system can be changed to accommodate the mold. The plastic was ABS (Chi-Mei PA-758) in the experiment, its glass transition temperature is 109°C. The material for mold base is JIS S50C. The material for mold core is ASSAB 718. There are two injection molds estimated the products using vapour chamber and the testing material is ABS. The VC\_RHCS can raise the tensile strength and reduce the defect of the welding lines of a plastic product because of rapid-uniform heating and cooling cycle with vapour chamber.

These temperature curves of zero to sixty seconds with / without vapour chamber are shown in Fig.s 3. In the Fig. 3(a), the temperature of point O is 73.9°C and the farthest corner away from point O is 34.7°C of point C at 60 seconds. Furthermore, temperature differences of the other points A, B, D are large values about 10°C each other at 60 seconds. In the Fig. 3(b), the temperature of point O and point C is 83.7°C and 67.8°C at 60 seconds, respectively. In addition, the temperatures of the other points A, B, D are almost 80°C at 60 seconds. The temperature curve of point O of Fig. 3(a) is faster raise than that of Fig. 3(b) at zero to thirty seconds resulting from the heater direct contact and slows down after thirty seconds. In other words, the temperature of point O of Fig. 3(a) is higher than that of Fig. 3(b) before thirty seconds. The mean temperature of these five points with vapour chamber and without vapour chamber is 78.3°C and 56.1°C, respectively. Rapid uniform temperature effect employing vapour chamber heating system is better even if the heater is direct touching point O on the surface of cavity for no vapour chamber system.

Fig. 3. Relationships of the temperatures with the heating time with/without vapour chamber.

#### **2.2 Employing VC\_RHCS in tensile testing parts**

The products of the injection molding experiments were tensile testing parts. They are evaluated the effectiveness of the proposed heating and cooling system with vapour chamber and without vapour chamber. There are two different mold designs namely one

the point C is the farthest distance away from point O. Mold temperature was raised to above the glass transition temperature of the plastic before the filling stage. Cooling of the mold was then started at the beginning of the packing stage. The entire heating and cooling device was incorporated with the mold. The capacity and size of the heating and cooling system can be changed to accommodate the mold. The plastic was ABS (Chi-Mei PA-758) in the experiment, its glass transition temperature is 109°C. The material for mold base is JIS S50C. The material for mold core is ASSAB 718. There are two injection molds estimated the products using vapour chamber and the testing material is ABS. The VC\_RHCS can raise the tensile strength and reduce the defect of the welding lines of a plastic product because of

These temperature curves of zero to sixty seconds with / without vapour chamber are shown in Fig.s 3. In the Fig. 3(a), the temperature of point O is 73.9°C and the farthest corner away from point O is 34.7°C of point C at 60 seconds. Furthermore, temperature differences of the other points A, B, D are large values about 10°C each other at 60 seconds. In the Fig. 3(b), the temperature of point O and point C is 83.7°C and 67.8°C at 60 seconds, respectively. In addition, the temperatures of the other points A, B, D are almost 80°C at 60 seconds. The temperature curve of point O of Fig. 3(a) is faster raise than that of Fig. 3(b) at zero to thirty seconds resulting from the heater direct contact and slows down after thirty seconds. In other words, the temperature of point O of Fig. 3(a) is higher than that of Fig. 3(b) before thirty seconds. The mean temperature of these five points with vapour chamber and without vapour chamber is 78.3°C and 56.1°C, respectively. Rapid uniform temperature effect employing vapour chamber heating system is better even if the heater is direct

 (a) (b) Fig. 3. Relationships of the temperatures with the heating time with/without vapour chamber.

The products of the injection molding experiments were tensile testing parts. They are evaluated the effectiveness of the proposed heating and cooling system with vapour chamber and without vapour chamber. There are two different mold designs namely one

rapid-uniform heating and cooling cycle with vapour chamber.

touching point O on the surface of cavity for no vapour chamber system.

**2.2 Employing VC\_RHCS in tensile testing parts** 

gate mold and two opposite gates mold were selected for the experiments. Fig. 3 shows the relationships of the temperature with the heating time with/without vapour chamber. If there are no the effect of vapour chamber, these five thermal couples show non-uniform on the surface of cavity. However, the dimensions of these tensile testing parts are 215.9 x 12.7 x 25.4mm3 with 3.175mm thickness.

Table 1 shows the tensile strength of the products in different situation of one gate and two opposite gates with and without vapour chamber. The tensile strength supposes maximum for one gate without vapour chamber heating system because of on welding line from the Fig. 4. Fig. 4 shows the test specimen and SEM images of welding line. One gate without vapour chamber system experiments resulted tensile test pars without any welding lines. Two gates without vapour chamber heating system appears apparent welding line and its tensile strength of testing part is lower 11.1% than the part of one gate from table 1 and Fig. 4.

(a) Different design for tensile test specimen

 (b) Two opposite gates at the temperature of Point O is 75°C without vapour chamber system

 (d) Two opposite gates at the temperature of Point O is 110°C with vapour chamber system

(c) Two opposite gates at the temperature of Point O is 75°C with vapour chamber system

(e) One gate at the temperature of Point O is 75°C without vapour chamber system

Fig. 4. SEM pictures of one gate and two opposite gates.

Insert Molding Process Employing Vapour Chamber 213

(a)Case 1 (b)Case 2 (c)Case 3

(d) Specification of the eight holes test part

invention of breathing regulators. Basically, a regulator can be divided into the first and second stages. The first stage regulates air output pressure at a stable value of 14atm, reducing from the compressed air cylinder pressure of 200atm to 20atm, and then supplies that air to the second stage. The second stage is connected to the divers' mask and supplies

Underwater movement requires a higher expenditure of energy and an increased rate of respiration than the same movement on land. This is caused by the higher density of water, and the need to overcome water resistance or drag. The second stage supplies air at a pressure equivalent to water pressure, which in turn depends on the depth, in order to lessen the diver's lung burden. A structural representation of the second stage is shown in Fig.6, while Fig. 7 gives a schematic of the second stage. The second stage of the regulator thus affects the smoothness of diver breathing, a key factor in the divers' ability to function underwater. During this experiment, the relationship between characteristic factors and performance of breathing regulators will be explored through numerical methods, to enable

Breathing resistance is directly related to the diver's ability to receive sufficient air to safely perform in the underwater environment and must be considered a primary factor in the design of breathing apparatuses. An ideal breathing regulator allows divers to breathe without consuming additional energy when breathing under water. In other words, in the ideal regulator, respiratory work rate and respiratory impedance are zero. Many patents (Belloni 2001; Brown & Brown 2000 & 2002; Christianson 1987; Ferguson 1997; Garraffa 1997; Garraffe 1996; Hansen & Lingenfelter 1987; Houston 1981; Toth1985) involve optimum designs for breathing regulator. These patents discussed above provide researchers with a

Fig. 5. SEM picture of the eight holes plate.

air at ambient pressure based on the diver's respiration.

designers to create more efficient breathing regulators.


Table 1. The results of the tensile test.

Two gates with vapour chamber heating system appears light welding line and its tensile strength of testing part is higher 6.8% than the part of two gates without vapour chamber system. If increasing the preheating temperature from 75°C to 110°C with two gates vapour chamber system, the tensile strength can again add 3.2%.

#### **2.3 Employing VC\_RHCS in eight holes test part**

Another test part is the multi-holes products tested to evaluate the effectiveness of the system with vapour chamber in different situation of cavity and core temperatures. These multi-holes products have eight holes with four 10mm and 5mm diameter holes, respectively. The dimensions of eight holes products are 110 x 53 x 3.175mm3. Three temperature combinations were tested in the experiments. Case 1 is the conditions of cavity temperature 60°C and core temperature 60°C. Case 2 is the conditions of cavity temperature 60°C and core temperature 130°C. Case 3 is the conditions of cavity temperature 80°C and core temperature 130°C.

Figs. 5 show the specification of the eight holes test part and SEM images of V-notch. The means is that there are many welding lines on the surface of the transparent parts. The depth of the V-notch is deeper the welding line is more obvious for transparent. From the Figs. 5, the depths of the V-notch found on each case are 12μm, 2μm, and 0.5μm respectively. The product of the case 1 shows a V-notch 24 times deeper than the product of case 3. The effects of cavity and core temperatures are also important for welding line. Finally, utilizing VC\_RHCS shows that the temperature differences of cavity employing vapour chamber are smaller than that without vapour chamber and increasing preheating temperature can add the tensile strength for two opposite gates resulting from extending enough fluid flow. And the new VC\_RHCS can reduce the depth of v-notch as much as 24 times.
