Injection molding apparatus and process for flexible demolding with pressure holding

Abstract

The application discloses a flexible demolding pressure maintaining injection device and process in the field of injection molds, which comprises a fixed mold and a movable mold, a ventilation hole communicating with a cavity is arranged in the movable mold core, and the inside of the core is divided into a suction cavity and a piston cavity. A piston in the piston cavity divides a first cavity, the piston is connected with a plugging piece corresponding to the ventilation hole, and a gas-permeable glue-blocking micro air channel is arranged on the outer wall of the plugging piece. The first cavity and the suction cavity are respectively connected to an external air source. When negative pressure is provided, the negative pressure of the first cavity drives the piston to drive the plugging piece to lock the ventilation hole, and the negative pressure of the suction cavity is used to suck and exhaust the cavity through the micro air channel; when positive pressure is switched, the positive pressure of the first cavity drives the piston to open the ventilation hole, and the positive pressure airflow of the suction cavity is sprayed out through the ventilation hole to form an air cushion demolding. The application realizes the precise linkage of anti-overflow exhaust and flexible demolding without an independent driving source by switching the positive and negative pressure of a single air source.

Description

Technical Field

[0001] This invention relates to the field of injection molds, and more specifically to an injection molding device and process for flexible demolding and pressure holding. Background Technology

[0002] In the field of precision injection molding, where ultra-thin walls and surfaces with micro-nano textures or high gloss are required, the venting efficiency and demolding method of the mold directly determine the final molding quality and yield of the product.

[0003] In traditional injection molding processes, as the high-temperature and high-pressure polymer melt rapidly fills the mold cavity, if the air inside the cavity cannot be expelled in time, it is very easy to generate "trapped air" or "closed air" phenomena at the melt front or blind corner areas, which in turn leads to defects such as empty packages, insufficient glue, surface flow marks, or even scorching defects caused by local gas being extremely compressed and heated.

[0004] To remove the molded product, existing injection molding equipment generally relies on mechanical ejection mechanisms such as ejector pins, ejector tubes, or ejector plates for mold opening and demolding. However, for ultra-thin-walled or large-area precision plastic parts, mechanical ejector pins generate highly concentrated local stress at the moment of contact with the product. This can easily lead to whitening, perforation, or severe mechanical scratches on the product surface, and can also cause irreversible warping deformation of the entire product due to uneven local stress.

[0005] How to effectively solve the problem of air trapped in the cavity during the injection molding process, and completely avoid mechanical stress after molding to achieve non-destructive demolding of the product, has become a technical problem that urgently needs to be solved in the field of precision injection molding. Summary of the Invention

[0006] The purpose of this invention is to solve the problems of air leakage during injection molding and damage to molded parts caused by ejector pins in traditional mold opening methods. To address these technical problems, this invention provides the following technical solution:

[0007] A flexible demolding and pressure-holding injection molding device is provided, including a fixed mold and a moving mold. The moving mold has a core with a molding end. An air gap exchange area is formed on the molding end. At least one vent hole is formed within the air gap exchange area. An air cavity is formed on the inner side of the core. The air cavity is divided into a suction cavity near the air gap exchange area and a piston cavity away from the air gap exchange area by a partition mechanism. The vent hole connects the cavity and the suction cavity.

[0008] The piston chamber is equipped with a piston with a dynamic seal. The piston chamber is divided into a first chamber close to the suction chamber and a second chamber away from the suction chamber. The second chamber is connected to the atmosphere. The piston has a coaxial piston rod that is dynamically sealed and passes through the partition mechanism to the suction chamber. The free end of the piston rod is equipped with a sealing element corresponding to the vent hole.

[0009] The outer wall of the sealing component fits tightly with the inner wall of the corresponding vent hole, and several micro-channels are formed on the outer wall of the sealing component, which are evenly distributed along their circumference. The micro-channels are used to form a breathable and adhesive-resistant channel that allows gas to pass through and blocks melt penetration when the sealing component fits tightly with the vent hole.

[0010] The core also has a first branch air passage and a second branch air passage that connect the first cavity and the suction cavity respectively. The first branch air passage and the second branch air passage are connected to an external air source in the outer area of ​​the moving mold.

[0011] When the external air source provides negative pressure, the first chamber and the suction chamber are simultaneously or sequentially formed into a negative pressure state. The negative pressure in the first chamber drives the piston to move towards the molding end so that the sealing component blocks the corresponding vent hole. At the same time, the negative pressure in the suction chamber generates a suction and exhaust effect on the cavity through the micro air channel.

[0012] When the external air source is switched to positive pressure, the first cavity and the suction cavity are simultaneously or sequentially formed into a positive pressure state. The positive pressure in the first cavity drives the piston to move away from the molding end to open the vent hole. At the same time, the positive pressure airflow in the suction cavity enters the space between the injection molded part and the molding end through the opened vent hole to provide pneumatic demolding.

[0013] Furthermore, the vent is a frustum-shaped hole with a larger inner diameter and a smaller outer diameter, and the sealing component is a frustum-shaped body that matches the shape of the vent. The micro-air passage is formed on the outer wall of the frustum-shaped body, and its extension direction is the generatrix direction of the frustum-shaped body.

[0014] Furthermore, the depth and / or width of the micro-channels are configured to be between 0.005 mm and 0.03 mm, so that their size is smaller than the critical gap for melt overflow of the target injection molding material at the process temperature.

[0015] Furthermore, multiple dispersed vent holes are formed within the air gap exchange zone. A support plate is fixedly connected to the free end of the piston rod. The side of the support plate away from the piston rod is fixedly connected to all the sealing components. The support plate has a partially hollowed-out structure to guide airflow within the suction chamber.

[0016] Furthermore, the first and second branch air passages are connected to an external air source outside the moving mold via a dual-channel solenoid valve.

[0017] Furthermore, the effective pressure-bearing area of ​​the piston within the first chamber is greater than the sum of the areas of all the sealing components that bear the air pressure on the side facing the suction chamber.

[0018] Furthermore, there is one vent hole located at the center of the forming end, and one sealing element coaxially connected to the piston rod.

[0019] An injection molding process using a flexible demolding and pressure-holding injection molding device is provided. A first pressure sensor and a second pressure sensor are respectively installed in a first cavity and a suction cavity. The method includes the following steps:

[0020] S1, control the external air source to output negative pressure to the first branch airway and the second branch airway. According to the pressure signal fed back by the first air pressure sensor, when the negative pressure in the first cavity reaches the first preset threshold, it is determined that the piston has driven the sealing member to fully wedge in and lock the vent hole, and the device allows the injection action to be performed.

[0021] S2, the injection molding machine injects melt into the cavity. During this process, the negative pressure in the suction chamber continuously draws gas from the cavity through the micro-air channel. The system obtains the pressure value fed back by the second air pressure sensor in real time to adjust the suction power of the external air source, so that the negative pressure value in the suction chamber is dynamically maintained within a preset safe negative pressure range to prevent the loss of negative pressure caused by the instantaneous change of cavity exhaust volume or the excessive penetration of melt caused by excessive negative pressure, until the injection and holding pressure process is completed.

[0022] S3, during the cooling phase after the pressure holding is completed, the external air source stops evacuating the vacuum and switches to output positive pressure airflow to the first branch air channel. When the first air pressure sensor detects that the positive pressure in the first cavity reaches the second preset threshold, it is determined that the piston has retracted into place and the vent is fully open.

[0023] S4, the device performs the mold opening action. At the same time or after the moving mold separates from the fixed mold, the external air source outputs a demolding positive pressure airflow to the second branch air channel. The positive pressure airflow fills the suction chamber and is ejected through the fully opened vent hole, forming a demolding air cushion between the inner surface of the injection molded part and the air gap exchange area, so as to use the uniformly distributed positive pressure of the fluid to peel the injection molded part from the molding end.

[0024] The beneficial effects of this invention are:

[0025] This invention constructs a first cavity and a suction cavity separated by a piston and a partition inside the core, and connects the piston to a sealing component with micro-air channels. By switching between positive and negative pressure from a single external air source, it achieves mechanical linkage between venting and flexible demolding functions. During injection molding, when negative pressure is introduced, the negative pressure in the first cavity drives the piston to close the vent hole, while the negative pressure in the suction cavity continuously draws in gas from inside the cavity through the micro-air channels, effectively avoiding gas trapping defects during injection molding. During demolding, when switching to positive pressure, the positive pressure in the first cavity drives the piston to retract to fully open the vent hole, while the positive pressure airflow in the suction cavity is ejected through the vent hole, forming a demolding air cushion between the injection molded part and the molding end, achieving stress-free integral peeling of the injection molded part. This technical solution utilizes the pressure distribution of the dual chambers to directly convert changes in air pressure into precise switching between venting and air blowing. Without the need for an additional independent mechanical drive source, it achieves both efficient anti-overflow venting during the injection molding stage and flexible demolding during the mold opening stage. Attached Figure Description

[0026] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0027] Figure 1 This is a planar structural cross-sectional view of the injection molding state according to an embodiment of the present invention;

[0028] Figure 2 This is a planar structural cross-sectional view of the demolded state according to an embodiment of the present invention;

[0029] Figure 3 This is a partial cross-sectional view of an embodiment of the multi-ventilation port of the present invention;

[0030] Figure 4 This is a schematic diagram of the planar structure of the sealing component and the support plate in an embodiment of the multi-ventilation hole invention;

[0031] The labels in the diagram represent the following: 1-fixed mold; 1a-cavity; 2-moving mold; 2a-core; 2a1-forming end; 2a11-air gap exchange area; 2a12-vent hole; 2b-air cavity; 2b1-partition mechanism; 2b2-suction cavity; 2b3-piston cavity; 2b31-first cavity; 2b32-second cavity; 2c-first branch air passage; 2d-second branch air passage; 3-piston; 3a-piston rod; 3b-support plate; 3c-sealing component; 3c1-micro air passage; 4-first air pressure sensor; 5-second air pressure sensor. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] This embodiment provides a flexible demolding and pressure-holding injection molding device, aiming to solve the problems of air blockage during injection molding and damage to the molded parts caused by ejector pins in traditional mold opening methods. For details, see [link to documentation]. Figures 1 to 4 As shown, this flexible demolding and pressure-holding injection molding device includes a fixed mold 1 and a moving mold 2. The moving mold 2 has a core 2a, and the core 2a has a molding end 2a1. An air gap exchange area 2a11 is formed on the molding end 2a1, and at least one vent hole 2a12 is formed within the air gap exchange area 2a11. An air cavity 2b is formed on the inner side of the core 2a. The air cavity 2b is divided into a suction cavity 2b2 near the air gap exchange area 2a11 and a piston cavity 2b3 away from the air gap exchange area 2a11 by a partition mechanism 2b1. The vent hole 2a12 connects the cavity 1a and the suction cavity 2b2.

[0034] A piston 3 with a dynamic seal is provided in the piston chamber 2b3. The piston chamber 2b3 is divided by the piston 3 into a first chamber 2b31 near the suction chamber 2b2 and a second chamber 2b32 away from the suction chamber 2b2. The second chamber 2b32 is connected to the atmosphere. The piston 3 has a coaxial piston rod 3a that is dynamically sealed and passes through the partition mechanism 2b1 to the suction chamber 2b2. The free end of the piston rod 3a is provided with a sealing element 3c corresponding to the vent hole 2a12.

[0035] The outer wall of the sealing component 3c fits tightly with the inner wall of the corresponding vent 2a12, and a number of micro-channels 3c1 are formed on the outer wall of the sealing component 3c evenly distributed along its circumference. The micro-channels 3c1 are used to form a breathable and adhesive-resistant channel that allows gas to pass through and blocks the melt from penetrating when the sealing component 3c fits tightly with the vent 2a12.

[0036] The core 2a also has a first branch air passage 2c and a second branch air passage 2d that are respectively connected to the first cavity 2b31 and the suction cavity 2b2. The first branch air passage 2c and the second branch air passage 2d are connected to an external air source in the outer region of the moving mold 2.

[0037] When an external air source provides negative pressure, the first cavity 2b31 and the suction cavity 2b2 are simultaneously or sequentially formed into a negative pressure state. The negative pressure in the first cavity 2b31 drives the piston 3 to move toward the molding end 2a1 so that the sealing member 3c blocks the corresponding vent 2a12. At the same time, the negative pressure in the suction cavity 2b2 generates a suction and exhaust effect on the cavity 1a through the micro air channel 3c1.

[0038] When the external air source is switched to positive pressure, the first cavity 2b31 and the suction cavity 2b2 are simultaneously or sequentially in a positive pressure state. The positive pressure in the first cavity 2b31 drives the piston 3 to move away from the molding end 2a1 to open the vent 2a12. At the same time, the positive pressure airflow in the suction cavity 2b2 enters between the injection molded part and the molding end 2a1 through the opened vent 2a12 to provide pneumatic demolding.

[0039] In the aforementioned basic design, if the vent 2a12 and the sealing component 3c are fitted with a conventional cylindrical shape, the presence of machining tolerances makes it difficult to ensure an absolutely tight fit between their sidewalls, which could easily affect the throttling and exhausting effect of the micro-channel 3c1. To improve the reliability of the sealing fit, the vent 2a12 is a frustum-shaped hole with a larger inner diameter and a smaller outer diameter, and the sealing component 3c is a frustum-shaped body that matches the shape of the vent 2a12.

[0040] In this configuration, the negative pressure in the first cavity 2b31 during injection molding is much greater than the negative pressure in the suction cavity 2b2. This pressure difference between the cavities can strongly drive the sealing component 3c to move outward and wedge into the vent hole 2a12, thereby ensuring that the outer wall of the frustum of the sealing component 3c and the inner wall of the vent hole 2a12 are tightly fitted. While ensuring a tight fit, the suction cavity 2b2 can still maintain its effective suction capability for air inside the cavity 1a by utilizing the micro-air channels 3c1 formed on the outer wall of the frustum and extending along the generatrix.

[0041] Further analysis reveals that the micro-airway 3c1, as a permeable and adhesive-resistant channel, faces several challenges. If its size is too large, it can lead to blockage due to high-temperature melt intrusion; if its size is too small, it cannot meet the rapid venting flow requirements during the injection molding cycle. To address this conflict between venting flow and anti-clogging, the depth and / or width of the micro-airway 3c1 are configured to be between 0.005 mm and 0.03 mm.

[0042] In practice, the micro-channel 3c1 can be fabricated using femtosecond laser micromachining or precision micro-electro-discharge molding processes, ensuring its size is smaller than the critical gap for melt overflow of the target injection molding material at the process temperature, thus physically preventing melt penetration. Furthermore, to more reliably prevent high-temperature melt from penetrating the micro-channel 3c1 under suction, the negative pressure within the suction chamber 2b2 will not increase indefinitely, but will be maintained within a preset safe negative pressure range through system regulation. This effectively avoids excessive melt penetration caused by excessive negative pressure suction while meeting venting requirements.

[0043] For injection molded parts with large surface areas or complex structures, pneumatic demolding at only a single point can easily lead to deformation due to uneven force distribution, and excessive local ejection torque can even cause breakage. To achieve large-area, uniform, and flexible demolding, multiple dispersed vent holes 2a12 are formed within the air gap exchange zone 2a11. A support plate 3b is fixedly connected to the free end of the piston rod 3a, and the side of the support plate 3b away from the piston rod 3a is fixedly connected to all the sealing components 3c. Since the support plate 3b is located inside the suction cavity 2b2, it has a partially hollowed-out structure to guide airflow within the suction cavity 2b2 and prevent it from obstructing the normal flow of internal gas.

[0044] Conversely, for small, precision injection molded parts with smaller dimensions and compact structures, using a multi-hole parallel structure would significantly increase processing costs and occupy too much internal mold space. To address the needs of this compact injection molding scenario, the number of vent holes 2a12 is one, located at the center of the molding end 2a1, and the number of sealing parts 3c is one, coaxially connected to the piston rod 3a, thereby simplifying the mechanism components and reducing space occupation.

[0045] When positive pressure is introduced during the demolding process, the positive pressure airflow in the suction chamber 2b2 acts on the side of the sealing element 3c facing the suction chamber 2b2, generating a locking thrust that pushes the sealing element 3c outward. This locking thrust counteracts the retraction opening force generated by the piston 3 in the first chamber 2b31. If the pulling force is insufficient, the vent 2a12 will not open smoothly. To overcome this potential interference and jamming risk, the effective pressure-bearing area of ​​the piston 3 in the first chamber 2b31 is greater than the sum of the areas of all sealing elements 3c facing the suction chamber 2b2. This ensures that, under the same air pressure, the retraction pulling force generated by the piston 3 is always greater than the locking thrust experienced by the sealing element 3c.

[0046] Although the force direction is ensured by the area difference, if the first cavity 2b31 and the suction cavity 2b2 are filled with positive pressure simultaneously, the impact of the airflow may still cause short-term force distortion in the mechanism. To more precisely control the timing of mechanical and fluid actions, the first branch airway 2c and the second branch airway 2d are connected to an external air source outside the moving mold 2 via a dual-channel solenoid valve. By configuring this dual-channel solenoid valve, the system can stagger the inflation times of the two cavities, allowing the first cavity 2b31 to build pressure first to open the sealing member 3c, and the suction cavity 2b2 to build pressure subsequently for blowing.

[0047] Based on the above-described device, this embodiment also provides an injection molding method to achieve fully automated closed-loop control. Simply relying on time presets for air pressure switching can easily lead to defective products due to delays in actual mechanical actions or air pressure fluctuations.

[0048] To address the monitoring gap in this process, a first pressure sensor 4 and a second pressure sensor 5 are respectively installed in the first cavity 2b31 and the suction cavity 2b2. The method includes the following steps:

[0049] S1, control the external air source to output negative pressure to the first branch airway 2c and the second branch airway 2d. According to the pressure signal fed back by the first air pressure sensor 4, when the negative pressure in the first cavity 2b31 reaches the first preset threshold, it is determined that the piston 3 has driven the sealing member 3c to fully wedge in and lock the vent 2a12. The device allows the injection action to be performed.

[0050] S2, the injection molding machine injects melt into cavity 1a. During this process, the negative pressure in the suction chamber 2b2 continuously draws gas from cavity 1a through micro air channel 3c1. The system obtains the pressure value fed back by the second air pressure sensor 5 in real time to adjust the suction power of the external air source, so that the negative pressure value in the suction chamber 2b2 is dynamically maintained within a preset safe negative pressure range to prevent the loss of negative pressure caused by the instantaneous change of the exhaust volume of cavity 1a or the excessive penetration of melt caused by excessive negative pressure, until the injection molding and holding pressure process is completed.

[0051] S3, during the cooling stage after the pressure holding is completed, the external air source stops evacuating the vacuum and switches to output positive pressure airflow to the first branch air channel 2c. When the first air pressure sensor 4 detects that the positive pressure in the first cavity 2b31 reaches the second preset threshold, it is determined that the piston 3 has retracted into place and the vent 2a12 is in a fully open state.

[0052] S4, the device performs the mold opening action. Simultaneously or after the separation of the moving mold 2 and the fixed mold 1, the external air source outputs a demolding positive pressure airflow to the second branch air channel 2d. The positive pressure airflow fills the suction chamber 2b2 and is ejected through the fully opened vent 2a12, forming a demolding air cushion between the inner surface of the injection molded part and the air gap exchange area 2a11, so as to use the positive pressure of the fluid to peel the injection molded part from the molding end 2a1.

[0053] The above embodiments are merely exemplary embodiments of the present invention and are not intended to limit the present invention. The scope of protection of the present invention is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to the present invention within its spirit and scope of protection, and such modifications or equivalent substitutions should also be considered as falling within the scope of protection of the embodiments of the present invention.

Claims

1. A flexible demolding and pressure-holding injection molding device, comprising a fixed mold (1) and a moving mold (2), wherein the moving mold (2) has a core (2a) and the core (2a) has a molding end (2a1), characterized in that, An air gap exchange area (2a11) is formed on the molding end (2a1), and at least one vent hole (2a12) is formed within the range of the air gap exchange area (2a11). An air cavity (2b) is formed on the inner side of the core (2a). The air cavity (2b) is divided into a suction cavity (2b2) ​​close to the air gap exchange area (2a11) and a piston cavity (2b3) away from the air gap exchange area (2a11) by a partition mechanism (2b1). The vent hole (2a12) connects the cavity (1a) and the suction cavity (2b2). The piston chamber (2b3) is provided with a dynamically sealed piston (3). The piston chamber (2b3) is divided by the piston (3) into a first chamber (2b31) close to the suction chamber (2b2) ​​and a second chamber (2b32) away from the suction chamber (2b2). The second chamber (2b32) is connected to the atmosphere. The piston (3) has a coaxial piston rod (3a) that dynamically seals through the partition mechanism (2b1) to the suction chamber (2b2). The free end of the piston rod (3a) is provided with a sealing element (3c) corresponding to the vent (2a12). The outer wall of the sealing member (3c) is tightly fitted with the inner wall of the corresponding vent (2a12), and a plurality of micro-channels (3c1) are formed on the outer wall of the sealing member (3c) evenly distributed along its circumference. The micro-channels (3c1) are used to form a gas-permeable and adhesive-resistant channel that allows gas to pass through and blocks melt penetration when the sealing member (3c) and the vent (2a12) are tightly fitted. The core (2a) also has a first branch air passage (2c) and a second branch air passage (2d) that respectively connect the first cavity (2b31) and the suction cavity (2b2). The first branch air passage (2c) and the second branch air passage (2d) are connected to an external air source in the outer region of the moving mold (2). When the external air source provides negative pressure, the first cavity (2b31) and the suction cavity (2b2) ​​are simultaneously or sequentially formed into a negative pressure state. The negative pressure in the first cavity (2b31) drives the piston (3) to move toward the molding end (2a1) so that the sealing member (3c) blocks the corresponding vent (2a12). At the same time, the negative pressure in the suction cavity (2b2) ​​generates a suction and exhaust effect on the cavity (1a) through the micro air channel (3c1). When the external air source is switched to positive pressure, the first cavity (2b31) and the suction cavity (2b2) ​​are simultaneously or sequentially in a positive pressure state. The positive pressure in the first cavity (2b31) drives the piston (3) to move away from the molding end (2a1) to open the vent (2a12). At the same time, the positive pressure airflow in the suction cavity (2b2) ​​enters between the injection molded part and the molding end (2a1) through the opened vent (2a12) to provide pneumatic demolding.

2. The injection molding device with flexible demolding and pressure holding according to claim 1, characterized in that, The vent (2a12) is a frustum-shaped hole with a larger inner diameter and a smaller outer diameter. The sealing member (3c) is a frustum-shaped body that matches the shape of the vent (2a12). The micro-air channel (3c1) is formed on the outer wall of the frustum-shaped body and extends in the direction of the generatrix of the frustum-shaped body.

3. The injection molding device with flexible demolding and pressure holding according to claim 2, characterized in that, The depth and / or width of the micro-channel (3c1) are configured to be between 0.005 mm and 0.03 mm, so that its size is smaller than the critical gap for melt overflow of the target injection molding material at the process temperature.

4. The injection molding device with flexible demolding and pressure holding according to claim 1, characterized in that, Multiple dispersed ventilation holes (2a12) are formed within the air gap exchange zone (2a11). A support plate (3b) is fixedly connected to the free end of the piston rod (3a). The side of the support plate (3b) away from the piston rod (3a) is fixedly connected to all the sealing components (3c). The support plate (3b) has a partially hollow structure to guide airflow within the suction chamber (2b2).

5. The injection molding device with flexible demolding and pressure holding according to claim 1, characterized in that, The first branch airway (2c) and the second branch airway (2d) are connected to the external air source outside the moving mold (2) via a dual-channel solenoid valve.

6. The injection molding device with flexible demolding and pressure holding according to claim 4, characterized in that, The effective pressure-bearing area of ​​the piston (3) in the first cavity (2b31) is greater than the sum of the areas of all the sealing elements (3c) that bear the air pressure on the side facing the suction cavity (2b2).

7. The injection molding device with flexible demolding and pressure holding according to claim 1, characterized in that, The number of the vent (2a12) is one and it is located at the center of the forming end (2a1). The number of the sealing element (3c) is one and it is coaxially connected to the piston rod (3a).

8. An injection molding process using a flexible demolding and pressure-holding injection molding device as described in any one of claims 1-7, characterized in that, A first pressure sensor (4) and a second pressure sensor (5) are respectively provided in the first cavity (2b31) and the suction cavity (2b2). The method includes the following steps: S1, control the external air source to output negative pressure to the first branch airway (2c) and the second branch airway (2d). According to the pressure signal fed back by the first air pressure sensor (4), when the negative pressure in the first cavity (2b31) reaches the first preset threshold, it is determined that the piston (3) has driven the sealing member (3c) to fully wedge in and lock the vent (2a12), and the device allows the glue injection action to be performed. S2, the injection molding machine injects melt into the cavity (1a). During this process, the negative pressure in the suction chamber (2b2) ​​continuously draws gas from the cavity (1a) through the micro air channel (3c1). The system obtains the pressure value fed back by the second air pressure sensor (5) in real time to adjust the suction power of the external air source so that the negative pressure value in the suction chamber (2b2) ​​is dynamically maintained within a preset safe negative pressure range to prevent the loss of negative pressure caused by the instantaneous change of the exhaust volume of the cavity (1a) or the excessive penetration of melt caused by excessive negative pressure until the injection molding and holding pressure process is completed. S3, during the cooling stage after the pressure holding is completed, the external air source stops evacuating and switches to output positive pressure airflow to the first branch air channel (2c). When the first air pressure sensor (4) detects that the positive pressure in the first cavity (2b31) reaches the second preset threshold, it is determined that the piston (3) has retracted into place and the vent (2a12) is in a fully open state. S4, the device performs the mold opening action. Simultaneously or after the separation of the moving mold (2) and the fixed mold (1), the external air source outputs a demolding positive pressure airflow to the second branch air channel (2d). The positive pressure airflow fills the suction chamber (2b2) ​​and is ejected through the fully opened vent (2a12), forming a demolding air cushion between the inner surface of the injection molded part and the air gap exchange area (2a11), so as to peel the injection molded part from the molding end (2a1) by using the positive pressure of the uniformly distributed fluid.

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