JP2010083124A - Injection molding system for forming minute foam-molded article and method of using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding system for forming a minute foam-molded article and a method of using the same, in which the foam-molded article has no defect on the external appearance and the problem of excessive injection of a liquid raw material can be avoided. <P>SOLUTION: After the dies are clamped to each other, first negative pressure is continuously imparted to a cavity, the liquid raw material is injected by using a molding machine, a high-pressure gas is injected into a liquid resin to form fine bubbles, and successively the first negative pressure is stopped and a positive pressure pulse is imparted to the cavity. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to molding of a foam molded product, and more particularly to an injection molding system and method for a fine foam molded product that improves the appearance of the foam molded product and accelerates molding.

  FIG. 1 shows a cross-sectional view of a conventional injection molding system for fine foam molded products. In the process of producing a foam molded product, in the process of injecting the raw material liquid into the cavity of the mold 1, the foaming gas supply source 2 injects high pressure air into the molding machine 3 and mixes the high pressure air into the raw material liquid to form microbubbles. Form. After the solidification of the raw material liquid is completed, the microbubbles form micropores in the molded product. Micropores can reduce the weight of the molded product. At the same time, since the presence of pores changes the overall expansion coefficient, the shrinkage phenomenon in the process of cooling the raw material liquid to form a molded product becomes relatively inconspicuous. For this reason, the warpage due to the size reduction of the foam-molded product or the material being cooled and contracted becomes relatively unnoticeable.

  After the raw material liquid having microbubbles enters the cavity, the temperature of the raw material liquid in contact with the cavity surface rapidly decreases, and the bubbles located on the cavity surface cannot continue to move. For this reason, the microbubbles located on the cavity surface form swirl marks on the surface of the molded product, and these swirl marks are distributed radially along the flow direction of the raw material liquid. Since the swirl mark impairs the smoothness of the appearance of the foam molded product, the foam molded product needs to be subjected to surface treatment such as painting, otherwise the foam molded product can only be used as an internal member, forming the appearance It cannot be used as a member.

  In addition, the high-pressure gas injected into the raw material liquid leaves the free surface of the raw material liquid and enters the cavity. As the raw material liquid flows, the cavity is gradually filled, and when these gases are sealed in the end structure of the cavity by the raw material liquid, it becomes impossible to leave the cavity from the pores or the gap between the male and female dies, This phenomenon is called gas entrainment 4. The gas entrainment 4 makes it impossible to reliably fill the cavity with the raw material liquid, and at the same time, the temperature of the source liquid is in contact with the part of the gas entrainment 4 and reliably contacts the cavity surface, so the temperature is not too high. The phenomenon of scorching appears. Thus, not only the surface structure of the foam-molded product becomes incomplete due to the gas entrainment 4, but also the phenomenon of scorching occurs at the location of these structural defects. In order to eliminate the gas entrainment phenomenon, it is necessary to inject the raw material liquid that exceeds a predetermined amount with a molding machine, and to flow the molding material into the gas entrainment 4 to eliminate the gas entrainment 4. However, an excessive amount of raw material liquid may cause a space for the expansion of microbubbles inside the cavity (the raw material liquid is an incompressible flow with respect to microbubbles), which affects the foaming effect and reaches the effect of weight reduction. Can not be.

  For this reason, it is an important technical problem how to improve the molding process of the foam-molded product and to avoid the defects of the foam-molded product due to the entrainment of gas and the problem due to the excessive injection of the raw material liquid.

  An object of the present invention is to provide an injection molding system for a fine foam molded product and a method thereof that can eliminate defects in the appearance of the foam molded product and avoid problems caused by injection of an excessive amount of raw material liquid.

  The injection molding system for a fine foam molded article of the present invention includes a mold, a temperature control device, a molding machine, a foaming gas supply source, and a cavity pressure control device. The mold includes a male mold and a female mold, which are closed together to form a cavity and used to inject the raw material liquid into the cavity. The temperature controller is used to heat the mold to the working temperature or to cool the mold to the mold opening temperature. The molding machine is used to inject the raw material liquid into the cavity, and the foaming gas supply source injects the high-pressure gas into the raw material liquid, and causes the high-pressure gas to form microbubbles in the raw material liquid. The cavity pressure control device continuously generates the first negative pressure to the cavity before the molding machine injects the raw material liquid into the cavity, removes the gas entrainment phenomenon and the swirl mark on the surface of the foam molded product, and foams. Used to improve the appearance of the molded product. In addition, the cavity pressure control device stops the first negative pressure in the process in which the raw material liquid is injected into the cavity, generates a positive pressure pulse to the cavity, thereby suppressing the flow of the raw material liquid, and the excessive amount of the raw material Avoid the occurrence of liquid injection problems.

  In the injection molding method of the fine foam molded article of the present invention, after the mold is closed, the first negative pressure is continuously applied to the cavity of the mold to make the pressure of the cavity smaller than the external pressure. Subsequently, the raw material liquid is continuously injected into the cavity, and high-pressure air is injected into the raw material liquid. The high-pressure gas forms microbubbles in the raw material liquid, and the first negative pressure removes the gas entrainment phenomenon and the swirl mark on the surface of the foam molded product, thereby improving the appearance of the foam molded product. Subsequently, the first negative pressure is stopped and a positive pressure pulse is applied to the cavity, thereby suppressing the flow of the raw material liquid and avoiding the occurrence of an excessive amount of the raw material liquid injection. Finally, after the gas in the cavity is discharged as the raw material liquid is injected and the cavity is filled with the raw material liquid, the injection of the raw material liquid is stopped and the mold is cooled. After the cooling of the mold is completed, the mold can be opened to take out the foamed molded product formed by solidifying the raw material liquid.

  The present invention reduces the phenomenon that the appearance of a foam molded product becomes non-flat due to entrainment of gas or a swirl mark, and makes the foam molded product have a glossy appearance and can be an appearance member. At the same time, the present invention can suppress the excessive growth of bubbles and avoid the problem that the molding machine injects an excessive amount of raw material liquid.

  As shown in FIGS. 2, 3, and 4, an injection molding system for a fine foam molded product according to an embodiment of the present invention includes a mold 10, a mold opening / closing device 20, a temperature control device 30, a cavity pressure control device 40, A molding machine 50 and a foaming gas supply source 60 are included.

  As shown in FIGS. 2, 3, and 4, the mold 10 includes a male mold 11 and a female mold 12, and the male mold 11 and the female mold 12 each have a concave or protruding structure corresponding to each other. After the mold 11 and the female mold 12 are coupled to each other and the mold is closed, a cavity 13 is formed inside the mold 10. The mold 10 further includes a plurality of passages 14 embedded in the male die 11 or the female die 12, and each passage 14 can be connected in parallel with the head and tail in parallel, and can be connected to a high temperature fluid or cooling Used to pass fluid and heat or cool the mold 10. The female die 12 includes a plurality of gas passages, and the cavity 13 communicates with the outside world. When the male mold 11 and the female mold 12 are closed together, the cavity 13 becomes airtight and the gas path is used to allow gas to pass through and into or out of the cavity. The plurality of gas paths include at least one inlet gas path 131 and one exhaust gas path 132, and the inlet gas path 131 is used to inject high-pressure gas into the cavity 13 and generates a positive pressure in the cavity 13 ( The pressure in the cavity 13 is greater than the external pressure). The exhaust gas path 132 is used for sucking out the gas and generates a negative pressure in the cavity 13 (the pressure in the cavity 13 is smaller than the pressure in the external environment).

  In addition, the male mold 11 includes an injection path 111, and the outer side surface of the male mold 11 and the cavity 13 are communicated. The molding machine 50 is connected to the injection path 111 and is used to inject a raw material liquid (liquid resin melted at a high temperature) into the cavity 13 from the injection path 111. The foaming gas supply source 60 is connected to the molding machine 50, and when the molding machine 50 sends out the raw material liquid and enters the cavity 13, a high pressure gas is injected into the raw material liquid by a nozzle, and microbubbles are injected into the high pressure gas in the raw material liquid. Used to form. The microbubbles are distributed in the raw material liquid with the flow of the raw material liquid, and expand under high temperature to increase its diameter. After the raw material liquid is cooled and solidified into a foamed molded product, the location of the microbubbles forms a porous structure.

  As shown in FIGS. 3 and 4, the mold opening / closing device 20 is used to linearly actuate a part or all of the members of the mold 10 to cause the mold 10 to open or close the mold. The mold opening / closing device 20 can be a hydraulic device, a link actuator, or a feed screw assembly. In this embodiment, the mold opening / closing device 20 is a hydraulic device, and includes a support 21 and a plurality of hydraulic cylinders 22. The support body 21 and the hydraulic cylinder 22 are installed on the seat portion 24, and the drive rod 23 of the hydraulic cylinder 22 is penetrated through the support body 21 and connected to the molding die 10. Among them, the female die 12 of the mold 10 is movably installed, the male die 11 is fixedly installed on the seat 24, the drive rod 23 is connected to the female die 12, and the female die 12 is moved linearly. The mold 10 is used for closing the mold 10 and closing the mold 10, or moving the female mold 12 linearly to separate it from the male mold 11 and opening the mold 10.

  2, 3, and 4, the temperature control device 30 includes a heating device 31, a cooling device 32, and a drainage device 33, and the heating device 31 is used to heat the mold 10 to the working temperature. Thus, the fluidity of the molding raw material is maintained, the foaming efficiency is enhanced, and the pore size and the porosity of the foamed molded product reach predetermined values. The cooling device 32 is used for cooling the mold 10, accelerates the cooling of the temperature of the mold 10 to the mold opening temperature, and shortens the waiting time from the completion of injection of the forming raw material to the mold opening.

  In the present embodiment, the heating device 31 is a high-temperature fluid supply source, and is used to provide a high-temperature fluid. For example, a boiler can be used to heat pure water and generate high-pressure high-temperature steam. In addition, the heating device 31 is connected to the passage 14 of the mold 10 through the heating valve 312, provides a high temperature fluid to pass through each passage 14, and heats the mold 10 to the working temperature. The cooling device 32 is used to provide a cooling fluid, for example, a condenser connected to a water tank, and provides low-temperature cooling water. The cooling device 32 is connected to the passage 14 of the mold 10 through a cooling valve 322, and provides cooling fluid to pass through each passage 14 to cool the mold 10 to the mold opening temperature. The high temperature fluid remaining in the passage 14 affects the cooling effect of the cooling fluid. Conversely, the cooling fluid remaining in the passage 14 also affects the heating effect of the high temperature fluid. The drainage device 33 is connected to the passage through a drainage valve 332 and provides high pressure and dry gas to pass through each passage 14 and is used to discharge the cooling liquid or high temperature fluid remaining in the passage 14. It is done.

  As shown in FIGS. 2 and 3, the cavity pressure control device 40 is connected to the cavity 13 through an inlet gas passage 131 and an exhaust gas passage 132. The cavity pressure control device 40 supplies the compressed gas from the inlet gas passage 131 into the cavity 13 and generates a positive pressure inside the cavity 13. Alternatively, the gas inside the cavity 13 is sucked out through the exhaust gas passage 132 and a negative pressure is generated inside the cavity 13. The cavity pressure control device 40 includes a high-pressure gas supply source 41 and a suction device 42. The high-pressure gas supply source 41 is a high-pressure cylinder or a high-pressure pump and is used to generate high-pressure gas. The suction device 42 is a vacuum pump and is negative. It is used to generate pressure and suck the gas in the cavity 13. The high pressure gas supply source 41 is connected to the inlet gas path 131 via the positive pressure air valve 412 and is connected to the cavity 13. The suction device 42 is connected to the exhaust gas passage 132 via the negative pressure air valve 422 and connected to the cavity 13. Among them, the positive pressure air valve 412 and the negative pressure air valve 422 can be switched on or off, and switches whether the high pressure gas supply source 41 and the suction device 42 are connected to the cavity 13 or not.

  The operation flow of the embodiment of the present invention will be described below. Please refer to FIG. 5 and FIG. 6 together with FIG. 2 and FIG. When the foam injection molding operation is started or after the previous foam injection molding operation is completed, the mold 10 is in the mold opening state, and the mold opening device 20 drives the female mold 12 to leave the male mold 11. Then, the surface of the cavity 13 is exposed, and the foam molded product completed in the previous injection molding operation can be taken out. At the same time, the heating device 31 of the temperature control device 30 starts to provide the high-temperature fluid, and is introduced into the passage 14 to start heating the mold 10 as shown in FIG. The heating method of the mold 10 is not limited to only introducing the high-temperature fluid into the passage 14, and the heating method of the mold 10 includes induction heating, electric heating rod heating, or direct flame heating. When the surface temperature of the cavity 13 reaches the working temperature, the heating device 21 stops providing the high-temperature fluid, and the temperature control device 30 stops heating the mold 10. Whether the surface of the cavity 13 has reached the working temperature is determined by acquiring the temperature of the surface of the cavity 3 by measuring a temperature sensor such as a thermocouple. Alternatively, the heating time is determined based on the experimental results, and it can be considered that the temperature of the cavity 13 surface has already reached the working temperature when the heating time has elapsed. After the temperature of the surface of the cavity 13 reaches the working temperature, the mold opening / closing device 20 drives the female mold 12 to close the male mold 11, and the mold closing operation is completed as shown in FIG.

  Please refer to FIG. 5 and FIG. 6 together with FIG. After the mold closing operation is completed, the suction device 42 of the cavity pressure control device 40 is activated, the corresponding negative pressure air valve 422 is opened, and the suction device 42 continues to generate the first negative pressure to the cavity 13. The pressure of the cavity 13 is made smaller than the external pressure.

  As shown in FIGS. 5, 6, and 7, the molding machine 50 injects a raw material liquid into the mold 10 and performs high-speed injection molding. As shown in FIG. 6, the first negative pressure accelerates the entry of the raw material liquid into the cavity 13, and at this time, the flow rate of the raw material liquid becomes relatively high. At the same time, the foaming gas supply source 60 also injects high-pressure air into the molding machine 50 and mixes microbubbles into the raw material liquid. At this time, since the cavity pressure control device 40 continues to apply the first negative pressure to the cavity 13, the growth of the bubbles is accelerated to a predetermined hole diameter. Since the first negative pressure continues to suck out the gas in the hollow portion of the cavity 13 (the area not yet filled with the raw material liquid), the entry of the raw material liquid into the cavity 13 is accelerated. At the same time, since the gas in the cavity 13 is continuously sucked out, the phenomenon of gas entrainment in the fine structure portion is generated, and the occurrence of the phenomenon of incomplete filling is avoided. In addition, since the raw material is injected after the mold 10 is heated to reach the working temperature, the raw material liquid maintains good fluidity, and bubbles located at the surface portion of the cavity 13 are used as the leading edge of the raw material liquid. The swirl mark can be prevented from being formed on the surface of the foam molded product after the raw material liquid is cooled and solidified.

  As shown in FIGS. 5, 6, and 7, the application of the first negative pressure is stopped after the first negative pressure time has elapsed after the start of high-speed molding. This time is usually when the injection of the forming raw material is completed by half and when the injection amount has already reached almost half of the total injection amount. At this time, the raw material liquid has already been filled in most of the space of the cavity 13, but the gas passage 131 and the exhaust gas passage 132 have not been filled yet. Taking the case where the injection time for completely filling the cavity 13 with the raw material liquid is 1-2 seconds as an example, the first negative pressure time is between about one quarter to one half of the injection time, It takes about 0.5 seconds. Since the method of stopping the first negative pressure is mainly performed by cutting the communication between the suction device 42 and the cavity 13, the first negative pressure is cut only by closing the negative pressure air valve 422 of the corresponding exhaust gas passage 132. be able to. The suction device 42 may be stopped or operated continuously at the same time. Since it is necessary to apply a negative pressure to the cavity 13 again thereafter, it is best to keep the suction device 42 continuously operated.

  As shown in FIGS. 5, 6, and 7, after the first negative pressure time is over, the positive pressure air valve 412 is opened, the high pressure gas supply source 41 is communicated with the cavity 13, and the hollow portion in the cavity 13 is opened. A positive pressure pulse is generated and a specific amount of high-pressure gas is injected. A positive pressure pulse momentarily applies pressure to the raw material liquid, thereby suppressing the continued growth of microbubbles, fixing the bubbles to a specific diameter, and simultaneously generating new bubbles. To keep the porosity in the finished foam-molded product constant. At this time, the flow rate of the raw material liquid decreases under the action of positive pressure, the rate at which the injection amount has already increased is slowed (see FIG. 6), and the molding machine injects the raw material liquid that exceeds a predetermined amount. To prevent. After the high pressure gas supply source 41 provides the positive pressure pulse, the positive pressure air valve 412 is immediately closed, and the high pressure gas is continuously injected along with the raw material liquid. Slowly leave the cavity 13 from the gap between the molds 12.

  As shown in FIGS. 5, 6, and 7, after providing the positive pressure pulse, the negative pressure air valve 422 can be reopened and a second negative pressure can be continuously applied to the cavity 13. The second negative pressure sucks out the remaining gas in the cavity 13, accelerates the flow rate of the raw material liquid to quickly increase the injected amount, and accelerates the filling of the raw material liquid into the remaining space of the cavity 13, And a good filling effect is maintained. However, as described above, the gas inside the cavity 13 can be naturally discharged without applying the second negative pressure.

  As shown in FIGS. 5, 6, and 8, after the injection is completed, that is, after the raw material liquid has already been completely filled into the cavity 13, the injection operation of the molding machine 50 is stopped and the negative pressure air valve 422 is closed at the same time. To stop the second negative pressure. A drain device 33 of the temperature control device 30 provides high pressure air to pass through the passage 14 and eliminates the remaining hot fluid. Subsequently, the cooling fluid supply source 31 provides the cooling fluid, passes through the passage 14, cools the mold 10, and quickly reduces the temperature of the mold 10 to the mold opening temperature. After the mold 10 reaches the mold opening temperature, the mold opening / closing device 20 drives the female mold 12 to be detached from the male mold 11 to expose the surface of the cavity 13. At the same time, high-pressure air is first provided by the drainage device 33, and the remaining cooling fluid is removed by passing through the passage 14. Subsequently, the high-temperature fluid source 10 starts providing the high-temperature fluid, passes through the passage 14, heats the mold 10, and prepares for the next injection molding operation.

  In the present invention, a first negative pressure is generated in the cavity 13 in the process of foam molding to accelerate the injection speed. At the same time, the flow of the raw material liquid is maintained by preheating the mold 10, and the generation of the first negative pressure is assisted to effectively prevent the swirl mark from appearing on the surface of the foam molded product, and the foam molded product has a light-smooth appearance. Is provided. For this reason, the foam-molded article manufactured by this invention can be directly used as an external appearance member. At the same time, the first negative pressure sucks out the gas entrainment in the cavity 13 and can avoid the occurrence of the gas entrainment phenomenon and affecting the integrity of the foam molded product. In the injection process, pressure is instantaneously applied with a positive pressure pulse to suppress excessive bubble growth. At the same time, the positive pressure pulse can temporarily slow the flow rate of the raw material liquid, and the injection amount can be adjusted appropriately to prevent the molding machine from injecting an excessive amount of the raw material liquid. The second negative pressure accelerates the flow of the raw material liquid again, and further shortens the time required for the raw material liquid injection.

It is sectional drawing of the injection molding system of the fine foaming molded article in a prior art. It is a system block diagram of the Example of this invention. It is sectional drawing which shows the mold open state of the metal mold | die of the Example of this invention. It is sectional drawing which shows the mold closing state of the metal mold | die of the Example of this invention. It is a figure which shows the timing of the shaping | molding process in the Example of this invention. It is a curve diagram which shows the influence with respect to the raw material liquid flow volume of the 1st negative pressure in the Example of this invention, a positive pressure pulse, and a 2nd negative pressure, and the injection-completed quantity. It is sectional drawing which shows the cavity injection | pouring state of the raw material liquid in the Example of this invention. It is sectional drawing which shows the cavity injection | pouring state of the raw material liquid in the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 .... Mold 2 ... Foaming gas supply source 3 ... Molding machine 10 ... Mold 11 ... Male die 111 ... Injection path 12 ··· Female mold 13 ··· Cavity 131 ··· Inlet gas passage 132 ··· Exhaust gas passage 14 ··· Channel 20 ··· Mold opening / closing device 21... Support 22... Hydraulic Cylinder 23... Drive Rod 24... Seat 30. ... Heating valve 32 ... Cooling device 322 ... Cooling valve 33 ... Drainage device 332 ... Drainage valve 40 ... Cavity pressure control device 41- .... High pressure gas supply source 412 ... Positive pressure air valve 42 ... Suction device 422 ... Negative pressure air valve 50 ... Molding machine 60 ... foaming gas supply source

Claims (20)

An injection molding method for a fine foam molded article,
Providing a mold and closing the mold,
Continuously applying a first negative pressure to the cavity of the mold, making the pressure of the cavity smaller than the external pressure,
Continuously injecting the raw material liquid into the cavity, and injecting high-pressure air into the raw material liquid;
Stopping the first negative pressure and applying a positive pressure pulse to the cavity;
Exhausting the gas in the cavity,
Stopping the injection of the raw material liquid and cooling the mold,
Including a procedure of opening the mold and taking out a foamed molded product formed by solidifying the raw material liquid,
Injection molding method for fine foam molded products.   2. The method according to claim 1, wherein the step of discharging the gas in the cavity includes a step of continuously applying a second negative pressure to the cavity and sucking out the residual gas in the cavity. Injection molding method for fine foam molded products.   The method for injection molding a fine foam molded article according to claim 1, further comprising a step of heating the mold to an operating temperature before closing the mold.   4. The method for injection molding of a micro-foamed molded product according to claim 3, wherein the step of heating the mold includes a step of providing a high-temperature fluid to pass through the passage of the mold.   5. The microfoamed molded article according to claim 4, further comprising a step of providing a high-pressure gas in the mold passage to eliminate the remaining fluid before providing the hot fluid. Injection molding method.   2. The method for injection molding a micro-foamed molded product according to claim 1, wherein the step of cooling the mold includes a step of providing a cooling fluid to pass through the passage of the mold.   7. The method according to claim 6, further comprising the step of providing a high-pressure gas to pass through the mold passage to eliminate the remaining fluid before providing the cooling fluid. An injection molding method for foam molded products. An injection molding system for fine foam molded products,
A male mold and a female mold are provided, the male mold and the female mold are closed to each other to form a cavity, and a mold used for injecting the raw material liquid therein,
A temperature control device used to heat the mold to a working temperature, or to cool the mold to a mold opening temperature;
A molding machine used to inject the raw material liquid into the cavity;
A foaming gas supply source connected to the molding machine and used to inject high-pressure gas into the raw material liquid to form microbubbles in the raw material liquid;
The first negative pressure is generated in the cavity, and the first negative pressure is generated in the cavity before the raw material liquid is injected into the cavity by the molding machine. Comprising a cavity pressure control device used to stop the pressure and to generate a positive pressure pulse to the cavity;
Injection molding system for fine foam molded products.   The micro foam molded article according to claim 8, wherein the male mold includes an injection path, the outer surface of the male mold communicates with the cavity, and the molding machine is connected to the injection path. Injection molding system.   The temperature control device includes a heating device used to heat the mold to the working temperature, and a cooling device used to cool the mold to the mold opening temperature. Item 9. An injection molding system for a fine foam molded article according to Item 8.   The mold includes a plurality of passages, the passages are embedded in at least one of the male type and the female type, and are used to allow fluid to pass through, the heating device is a high-temperature fluid source, Fluid is provided to pass through each of the passages and used to heat the mold, and the cooling device is provided to provide cooling fluid to pass through each of the passages and used to cool the mold. The injection molding system for a fine foam molded article according to claim 10, wherein   A drainage device is further provided for supplying a high-pressure and dry gas to pass through each of the passages, and discharging a cooling liquid or a high-temperature fluid remaining in each of the passages. 11. An injection molding system for a fine foam molded article according to 11.   9. The injection molding system for a fine foam molded article according to claim 8, further comprising a mold opening / closing device, and used to close or open the male mold and the female mold.   14. The injection molding system for a fine foam molded product according to claim 13, wherein the male mold is fixedly installed and the female mold is moved by the mold opening / closing device.   9. The cavity pressure controller includes a high pressure gas source used to provide the positive pressure pulse and a suction device used to provide the first negative pressure. The injection molding system of the micro-foamed molded product described.   The injection molding of the fine foam molded product according to claim 15, wherein the mold includes an inlet gas passage connected to the high-pressure gas supply source and an exhaust gas passage connected to the suction device. system.   The high-pressure gas supply source is connected to the entry gas path via a positive pressure air valve, and the positive pressure air valve can be switched between open and closed, and whether to connect the high-pressure gas supply source to the cavity. The injection molding system for a fine foam molded article according to claim 16, wherein the system is used for switching.   The suction device is connected to the exhaust gas path via a negative pressure air valve, and the negative pressure air valve can be switched between open and closed, and is used to switch whether the suction device is connected to the cavity. The injection molding system for a fine foam molded article according to claim 16, wherein the system is an injection molding system.   16. The injection molding of a fine foam molded article according to claim 15, wherein the suction device applies a second negative pressure to the cavity after the high pressure gas supply source provides the positive pressure pulse. system.   9. The injection molding system for a fine foam molded article according to claim 8, wherein the cavity pressure control device applies a second negative pressure to the cavity after generating the positive pressure pulse.

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