A foaming injection molding machine

Abstract

The application discloses a foaming injection molding machine and relates to the technical field of foaming injection molding machines.The foaming injection molding machine comprises a processing box, a lower mold and an upper mold, the lower mold is fixedly connected to the top of the processing box, the upper mold is arranged above the lower mold, a molding cavity is arranged between the lower mold and the upper mold, a flow channel assembly is arranged between the lower mold and the upper mold, the flow channel assembly surrounds the outside of the molding cavity, the inside of the processing box is provided with a filter screen through an elastic assembly, the filter screen is arranged obliquely, the inside of the processing box is provided with an air bag which is in communication with the flow channel assembly, the bottom end of the air bag abuts against the top of the filter screen, the bottom wall of the air bag is thin, a hose section is in communication with the air bag, and a hard pipe section is in communication with the end of the hose section which is far away from the air bag.The foaming injection molding machine is provided with the filter screen, the collecting screen frame, the air bag and the elastic assembly and the like, so that the effect of impurity filtering and automatic collection is achieved, meanwhile, the filter screen can swing up and down, the sliding speed of the impurities is accelerated, and the use efficiency of the foaming injection molding machine is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of foaming injection molding machine, in particular to a foaming injection molding machine. BACKGROUND

[0002] Foaming injection molding is a technology that liquid raw materials are extruded into a mold and then foamed. Generally, an extruder is used to extrude liquid raw materials into the mold, and in order to ensure the surface quality and smoothness of the finished product, the amount of bubble separation during injection molding needs to be strictly controlled.

[0003] When the foaming injection molding machine is in use, it is usually necessary to use a hot water circulation system to heat the molding cavity. Due to the change of water temperature, impurities are easily produced. The hot water circulation system of the existing foaming injection molding machine is mostly only provided with a filter screen for filtering treatment. Impurities are easily attached to the filter screen, causing blockage, which affects the use efficiency of the foaming injection molding machine.

[0004] Therefore, it is necessary to provide a foaming injection molding machine to solve the above problems. SUMMARY

[0005] The present application aims to provide a foaming injection molding machine to solve the problem that the hot water circulation system of the existing foaming injection molding machine is mostly only provided with a filter screen for filtering treatment, impurities are easily attached to the filter screen, causing blockage, which affects the use efficiency of the foaming injection molding machine.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a foaming injection molding machine, comprising a treatment box, a lower mold and an upper mold, the lower mold being fixedly connected to the top of the treatment box, the upper mold being arranged above the lower mold, a molding cavity being arranged between the lower mold and the upper mold;

[0007] A flow channel assembly is arranged between the lower mold and the upper mold, and the flow channel assembly surrounds the outside of the molding cavity;

[0008] The inside of the treatment box is provided with a filter screen through an elastic assembly, the filter screen is arranged obliquely, the inside of the treatment box is provided with an air bag in communication with the flow channel assembly, the bottom end of the air bag abuts against the top of the filter screen, the bottom wall of the air bag is thin, a soft tube section is communicated with the air bag, a hard tube section is communicated with one end of the soft tube section away from the air bag, and an electromagnetic valve is installed on the hard tube section;

[0009] The soft tube section is arranged obliquely, and the side wall of the soft tube section is thin;

[0010] The flow channel assembly comprises an upper flow inner cavity and a lower flow inner cavity, the upper flow inner cavity is arranged in the inside of the upper mold, the lower flow inner cavity is arranged in the inside of the lower mold, the inside of the treatment box is provided with a conveying pipe, the top end of the conveying pipe is in communication with the lower flow inner cavity, and the bottom end of the conveying pipe is in communication with the air bag;

[0011] The flow channel assembly also includes a first conveying channel, a second conveying channel, a third conveying channel, and a fourth conveying channel. The first and fourth conveying channels are located at the top of the lower mold, and the fourth conveying channel is connected to the lower flow cavity. The second and third conveying channels are located at the bottom of the upper mold, and both the second and third conveying channels are connected to the upper flow cavity. The first and second conveying channels are connected to each other, and the third and fourth conveying channels are connected to each other.

[0012] Preferably, the elastic component includes a first elastic band and a second elastic band. The second elastic band is fixedly connected to the upwardly inclined end of the filter screen, and the end of the second elastic band away from the filter screen is fixedly connected to the inner wall of the processing chamber. The first elastic band is fixedly connected to the end of the filter screen away from the second elastic band.

[0013] Preferably, a collection frame is fixedly connected to the inner wall of the treatment box. The collection frame is fixedly connected to the end of the first elastic band away from the filter screen. The collection frame is arc-shaped and the top is concave.

[0014] Preferably, a pump body is fixedly connected to the outer wall of the treatment tank, an outer pipe is connected to the water outlet end of the pump body, the end of the outer pipe away from the pump body is connected to the first conveying channel, and a suction pipe is connected to the water inlet end of the pump body, the suction pipe extending into the interior of the treatment tank.

[0015] Preferably, a heating device is installed inside the processing box, and the heating device is installed at the bottom of the processing box.

[0016] Preferably, an air extraction pipe and an air inflation pipe are fixedly connected to the upper mold, and both the air extraction pipe and the air inflation pipe are connected to the molding cavity. An injection molding pipe is fixedly connected to the lower mold, and the injection molding pipe is connected to the molding cavity.

[0017] Preferably, a top plate is provided above the upper mold, and sliding pillars are fixedly connected to the four corners of the bottom of the top plate. The bottom end of the sliding pillar is fixedly connected to the lower mold. A through groove is provided on the upper mold for the sliding pillar to pass through. An electric push rod is fixedly connected to the top plate, and the upper mold is fixedly connected to the telescopic end of the electric push rod.

[0018] This invention also discloses a control method for a foam injection molding machine, applicable to the aforementioned foam injection molding machine, and further includes the following operating steps:

[0019] S1. The upper and lower molds close to form a molding cavity;

[0020] S2. Hot water is supplied into the flow channel assembly until the temperature inside the molding cavity reaches 70°C, and then the temperature is maintained at a constant temperature.

[0021] S3. Use an inflation system to fill the molding cavity with air at a certain pressure, generally around 3 to 4 MPa.

[0022] S4. Use a vacuum screw extruder to squeeze liquid or viscous raw materials into the molding cavity until the air pressure in the molding cavity reaches the preset value. Then, evacuate the gas inside the molding cavity, and the raw material quickly fills the molding cavity under negative pressure.

[0023] The technical effects and advantages of this invention are as follows:

[0024] This invention achieves the effects of impurity filtration and automatic collection by setting up structures such as filter screen, collection frame, air bag and elastic component. At the same time, the filter screen can swing up and down to accelerate the sliding speed of impurities and improve the efficiency of foam injection molding machine.

[0025] Because the bottom wall of the airbag is thinner than other parts, the expansion deformation is more obvious, the squeezing effect on the filter is more obvious, and the up-and-down swing amplitude of the filter is increased;

[0026] The airbags are installed to increase the up-and-down swing amplitude of the filter screen, and at the same time, the water is sprayed out faster, which washes the impurities towards the collection frame and reduces the residue.

[0027] The flexible hose section is designed with a thin wall on one side to expand the coverage area of ​​the water sprayed from the rigid pipe section, making full use of the effective filtration area of ​​the entire filter screen, while avoiding the water from always acting on the same position and extending the service life of the filter screen.

[0028] The gas inside the molding cavity is evacuated, and the raw material quickly fills the molding cavity under negative pressure, making the foamed part more solid and preventing gaps or defects. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the foam injection molding machine of the present invention from one perspective.

[0030] Figure 2 This is a schematic diagram of the foam injection molding machine of the present invention from another perspective.

[0031] Figure 3 This is a schematic diagram of the upper mold and forming cavity structure of the present invention.

[0032] Figure 4 This is a schematic diagram of the upper mold and upper flow cavity structure of the present invention.

[0033] Figure 5 This is a schematic diagram of the lower mold and lower cavity structure of the present invention.

[0034] Figure 6 This is a schematic diagram of the lower mold and lower flow cavity structure of the present invention.

[0035] Figure 7 This is a schematic diagram of the lower and upper cavities of the present invention.

[0036] Figure 8 For the present inventionFigure 7 Enlarged schematic diagram of the structure at point A in the middle.

[0037] Figure 9 For the present invention Figure 8 Enlarged schematic diagram of the structure at point B.

[0038] Figure 10 This is a schematic diagram of the flexible hose section and rigid hose section of the present invention.

[0039] In the diagram: 1. Processing box; 2. Lower mold; 3. Upper mold; 4. Molding cavity; 401. Lower cavity; 402. Upper cavity; 5. Filter screen; 6. Collection mesh frame; 7. First elastic band; 8. Second elastic band; 9. Airbag; 10. Rigid pipe section; 11. Conveying pipe; 12. Heating device; 13. Solenoid valve; 14. Flexible hose section; 15. Pump body; 16. Suction pipe; 17. Outer pipe; 18. Upper flow inner cavity; 19. Lower flow inner cavity; 20. First conveying channel; 21. Second conveying channel; 22. Third conveying channel; 23. Fourth conveying channel; 24. Sliding column; 25. Electric push rod; 26. Air extraction pipe; 27. Inflation pipe; 28. Injection pipe; 29. ​​Top plate. Detailed Implementation

[0040] This invention provides, for example Figures 1-10 The foam injection molding machine shown includes a processing box 1, a lower mold 2 and an upper mold 3. The lower mold 2 is fixedly connected to the top of the processing box 1, and the upper mold 3 is disposed above the lower mold 2. A top plate 29 is disposed above the upper mold 3, and sliding pillars 24 are fixedly connected to the four corners of the bottom of the top plate 29. The bottom end of the sliding pillars 24 is fixedly connected to the lower mold 2, and a through groove is provided on the upper mold 3 for the sliding pillars 24 to pass through.

[0041] An electric push rod 25 is fixedly connected to the top plate 29. The upper mold 3 is fixedly connected to the telescopic end of the electric push rod 25. The electric push rod 25 is connected to the factory's power supply and drives the upper mold 3 to move up and down.

[0042] The lower mold 2 has a lower cavity 401 at the top and an upper cavity 402 at the bottom of the upper mold 3. The lower cavity 401 and the upper cavity 402 form a molding cavity 4.

[0043] In addition, the lower mold 2 is equipped with an injection tube, which is connected to the lower cavity 401. Liquid or viscous raw materials are extruded into the molding cavity 4 through the injection tube using a vacuum screw extruder.

[0044] An air extraction pipe 26 and an air inflation pipe 27 are fixedly connected to the upper mold 3, and both the air extraction pipe 26 and the air inflation pipe 27 are connected to the molding cavity 4. An injection molding pipe 28 is fixedly connected to the lower mold 2, and the injection molding pipe 28 is connected to the molding cavity 4. In actual use, solenoid valves are installed on both the air extraction pipe 26 and the air inflation pipe 27 to control their opening and closing states.

[0045] Before the liquid or viscous raw material is extruded into the molding cavity 4 through the injection pipe using a vacuum screw extruder, a certain pressure of air is injected into the molding cavity 4 through the air injection pipe 27 using an air inflation system (including an air pump, etc.); after the raw material is extruded into the molding cavity 4, the gas inside the molding cavity 4 is evacuated by the air extraction pipe 26, and the raw material quickly fills the molding cavity 4 under the action of negative pressure.

[0046] A flow channel assembly is provided between the lower mold 2 and the upper mold 3, surrounding the outside of the molding cavity 4. Specifically, before the liquid or viscous raw material is extruded into the molding cavity 4 through the injection tube using a vacuum screw extruder, hot water flows inside the flow channel assembly to heat the molding cavity 4; and before the molding process begins, cold water flows inside the flow channel assembly to cool the molding cavity 4 and harden it. This invention focuses on the issues related to the use of hot water flow.

[0047] In a specific configuration, the flow channel assembly includes an upper flow cavity 18 and a lower flow cavity 19. The upper flow cavity 18 is located inside the upper mold 3 and can cover the upper cavity 402; the lower flow cavity 19 is located inside the lower mold 2 and can cover the lower cavity 401.

[0048] The flow channel assembly also includes a first conveying channel 20, a second conveying channel 21, a third conveying channel 22 and a fourth conveying channel 23. The first conveying channel 20 and the fourth conveying channel 23 are opened on the top of the lower mold 2. The first conveying channel 20 and the fourth conveying channel 23 are located on both sides of the lower cavity 401, and the fourth conveying channel 23 is connected to the lower flow inner cavity 19.

[0049] The second conveying channel 21 and the third conveying channel 22 are located at the bottom of the upper mold 3. The second conveying channel 21 and the third conveying channel 22 are respectively distributed on both sides of the lower cavity 401. The second conveying channel 21 and the third conveying channel 22 are both connected to the upper flow cavity 18.

[0050] The first conveying channel 20 is connected to the second conveying channel 21, and the third conveying channel 22 is connected to the fourth conveying channel 23.

[0051] The processing box 1 is equipped with a conveying pipe 11, and the top end of the conveying pipe 11 is connected to the lower flow cavity 19.

[0052] The water flows sequentially through the first conveying channel 20, the second conveying channel 21, the upper flow cavity 18, the third conveying channel 22, the fourth conveying channel 23, the lower flow cavity 19, and the conveying pipe 11, before entering the interior of the treatment tank 1.

[0053] A pump body 15 is fixedly connected to the outer wall of the treatment tank 1. An outer pipe 17 is connected to the water outlet end of the pump body 15. The end of the outer pipe 17 away from the pump body 15 is connected to the first conveying channel 20. A suction pipe 16 is connected to the water inlet end of the pump body 15 and extends into the interior of the treatment tank 1. When the pump body 15 is running, the water is circulated.

[0054] The treatment tank 1 is equipped with a heating device 12, which is installed at the bottom of the treatment tank 1. The heating device 12 includes structures such as electric heating wires, and is used to heat the water when powered on. If cooling is required, the heating device 12 can be replaced with a cooling device, including semiconductor cooling chips, which is powered on and can be connected to the factory's power supply.

[0055] Considering the changes in water temperature, which can easily generate impurities, a filter screen 5 is installed inside the treatment tank 1 via an elastic component to treat these impurities. The filter screen 5 is inclined, with the conveying pipe 11 near the upwardly inclined end of the filter screen 5. A collection frame 6 is fixedly connected to the inner wall of the treatment tank 1. The collection frame 6 is fixedly connected to the end of the first elastic band 7 away from the filter screen 5. The collection frame 6 is arc-shaped with a concave top. The collection frame 6 can collect impurities, and the highest water level inside the treatment tank 1 will not exceed the bottom of the collection frame 6.

[0056] The elastic component includes a first elastic band 7 and a second elastic band 8. The second elastic band 8 is fixedly connected to the upwardly inclined end of the filter screen 5, and the end of the second elastic band 8 away from the filter screen 5 is fixedly connected to the inner wall of the processing box 1. The first elastic band 7 is fixedly connected to the end of the filter screen 5 away from the second elastic band 8. Both the first elastic band 7 and the second elastic band 8 can be made of rubber and have a certain degree of elasticity, allowing the filter screen 5 to swing up and down, accelerating the sliding of impurities from the top inclined surface of the filter screen 5 towards the collection frame 6.

[0057] Specifically, under the action of the pump body 15, the water flows through the first conveying channel 20, the second conveying channel 21, the upper flow cavity 18, the third conveying channel 22, the fourth conveying channel 23, the lower flow cavity 19 and the conveying pipe 11 in sequence, and enters the interior of the treatment tank 1; it flows out from the conveying pipe 11 and falls onto the filter screen 5, and the impurities slide down from the top slope of the filter screen 5 toward the collection frame 6 and are collected inside the collection frame 6.

[0058] Driven by the force of water flow and with the cooperation of the elastic components, the filter screen 5 swings up and down, accelerating the sliding speed of impurities.

[0059] To increase the speed at which impurities slide off, an air bladder 9 is installed inside the treatment box 1. The air bladder 9 is connected to the bottom end of the conveying pipe 11. The bottom end of the air bladder 9 abuts against the top of the filter screen 5. The bottom wall of the air bladder 9 is thin. When a large amount of water is injected into the air bladder 9, the expansion deformation is more obvious because the bottom wall of the air bladder 9 is thinner than other parts, and the squeezing effect on the filter screen 5 is more obvious, increasing the up-and-down swing amplitude of the filter screen 5.

[0060] This invention achieves the effects of impurity filtration and automatic collection by setting up a filter screen 5, a collection frame 6, an air bag 9, and elastic components. At the same time, the filter screen 5 can swing up and down to accelerate the sliding speed of impurities and improve the efficiency of the foam injection molding machine.

[0061] The airbag 9 is connected to a flexible hose section 14, which can be made of rubber. The end of the flexible hose section 14 away from the airbag 9 is connected to a rigid tube section 10, and a solenoid valve 13 is installed on the rigid tube section 10.

[0062] In actual use, when the solenoid valve 13 is closed, under the action of the pump body 15, the water flows sequentially through the first conveying channel 20, the second conveying channel 21, the upper flow inner cavity 18, the third conveying channel 22, the fourth conveying channel 23, the lower flow inner cavity 19, and the conveying pipe 11 into the interior of the airbag 9, where it accumulates. The airbag 9 expands and squeezes the filter screen 5, causing the filter screen 5 to swing downwards. Furthermore, because the bottom wall of the airbag 9 is thinner than other parts, the expansion deformation is more obvious, and the squeezing effect on the filter screen 5 is more obvious.

[0063] Next, the solenoid valve 13 is opened, and water is sprayed out from the hose section 14 and the rigid pipe section 10. The airbag 9 contracts and becomes smaller. With the cooperation of the elastic component, the filter screen 5 swings upward. At the same time, under the action of the airbag 9's own reset elasticity, the water is sprayed out faster, which can flush impurities toward the collection frame 6 and reduce residue.

[0064] The airbag 9 is installed to increase the up-and-down swing amplitude of the filter screen 5, and at the same time, it can accelerate the spraying of water, flushing impurities toward the collection frame 6 to reduce residue.

[0065] Repeat the operation multiple times to make filter 5 swing up and down.

[0066] The flexible hose section 14 is inclined, and one side of the flexible hose section 14 has a thin wall, as shown in the reference. Figure 10The flexible hose section 14 is tilted to the left. The left wall of the flexible hose section 14 is thin. When the solenoid valve 13 is closed, water will also enter the interior of the flexible hose section 14 when water accumulates inside the water bladder 9. Because the left wall of the flexible hose section 14 is thin, the deformation on the left side is greater than that on the right side, and the rigid pipe section 10 will tilt to the right. When the solenoid valve 13 is opened, water is sprayed out from the flexible hose section 14 and the rigid pipe section 10. At this time, the rigid pipe section 10 will tilt to the left to reset, so that the rigid pipe section 10 forms an arc-shaped movement trajectory, expanding the coverage area of ​​the water sprayed out from the rigid pipe section 10, making full use of the effective filtration area of ​​the entire filter screen 5, while avoiding the water always acting on the same position, thus extending the service life of the filter screen 5.

[0067] A flexible hose section 14 is provided, and one side wall of the flexible hose section 14 is thin to expand the coverage area of ​​the water sprayed from the rigid pipe section 10.

[0068] This invention also discloses a control method for a foam injection molding machine, applicable to the aforementioned foam injection molding machine, and further includes the following operating steps:

[0069] S1, the upper mold 3 and the lower mold 2 are closed to form the molding cavity 4;

[0070] S2. Hot water is supplied into the flow channel assembly until the temperature inside the molding cavity 4 reaches 70°C, and then the temperature is kept constant.

[0071] S3. Use the inflation system to fill the molding cavity 4 with a certain pressure of air, generally around 3 to 4 MPa.

[0072] S4. Using a vacuum screw extruder, liquid or viscous raw materials are extruded into the molding cavity 4 until the air pressure inside the molding cavity 4 reaches the preset value (an increase of 0.1 MPa is sufficient). Then, the gas inside the molding cavity 4 is evacuated, and the raw materials quickly fill the molding cavity 4 under negative pressure, making the foamed part more solid and preventing leaks or defects.

Claims

1. A foam injection molding machine, comprising a processing box (1), a lower mold (2) and an upper mold (3), characterized in that: The lower mold (2) is fixedly connected to the top of the processing box (1), the upper mold (3) is located above the lower mold (2), and a forming cavity (4) is provided between the lower mold (2) and the upper mold (3). A flow channel assembly is provided between the lower mold (2) and the upper mold (3), and the flow channel assembly surrounds the outside of the molding cavity (4); The processing box (1) is equipped with a filter screen (5) through an elastic component. The filter screen (5) is inclined. The processing box (1) is equipped with an air bladder (9) that communicates with the flow channel component. The bottom end of the air bladder (9) abuts against the top of the filter screen (5). The bottom wall of the air bladder (9) is thin. A flexible hose section (14) is connected to the air bladder (9). The end of the flexible hose section (14) away from the air bladder (9) is connected to a rigid pipe section (10). A solenoid valve (13) is installed on the rigid pipe section (10). The hose segment (14) is inclined and one side wall of the hose segment (14) is thin; The flow channel assembly includes an upper flow cavity (18) and a lower flow cavity (19). The upper flow cavity (18) is located inside the upper mold (3), and the lower flow cavity (19) is located inside the lower mold (2). The processing box (1) is provided with a conveying pipe (11). The top end of the conveying pipe (11) is connected to the lower flow cavity (19), and the bottom end of the conveying pipe (11) is connected to the airbag (9). The flow channel assembly further includes a first conveying channel (20), a second conveying channel (21), a third conveying channel (22), and a fourth conveying channel (23). The first conveying channel (20) and the fourth conveying channel (23) are located at the top of the lower mold (2). The fourth conveying channel (23) is connected to the lower flow cavity (19). The second conveying channel (21) and the third conveying channel (22) are located at the bottom of the upper mold (3). The second conveying channel (21) and the third conveying channel (22) are both connected to the upper flow cavity (18). The first conveying channel (20) is connected to the second conveying channel (21), and the third conveying channel (22) is connected to the fourth conveying channel (23).

2. The foam injection molding machine according to claim 1, characterized in that: The elastic component includes a first elastic band (7) and a second elastic band (8). The second elastic band (8) is fixedly connected to the upwardly inclined end of the filter screen (5). The end of the second elastic band (8) away from the filter screen (5) is fixedly connected to the inner wall of the processing box (1). The first elastic band (7) is fixedly connected to the end of the filter screen (5) away from the second elastic band (8).

3. The foam injection molding machine according to claim 2, characterized in that: A collection frame (6) is fixedly connected to the inner wall of the processing box (1). The collection frame (6) is fixedly connected to the end of the first elastic band (7) away from the filter screen (5). The collection frame (6) is arc-shaped and the top is concave.

4. The foam injection molding machine according to claim 1, characterized in that: A pump body (15) is fixedly connected to the outer wall of the treatment tank (1). An outer pipe (17) is connected to the water outlet end of the pump body (15). The end of the outer pipe (17) away from the pump body (15) is connected to the first conveying channel (20). A suction pipe (16) is connected to the water inlet end of the pump body (15). The suction pipe (16) extends into the interior of the treatment tank (1).

5. The foam injection molding machine according to claim 1, characterized in that: The processing box (1) is equipped with a heating device (12) inside, and the heating device (12) is installed at the bottom of the processing box (1).

6. The foam injection molding machine according to claim 1, characterized in that: The upper mold (3) is fixedly connected to an air extraction pipe (26) and an air inflation pipe (27), both of which are connected to the molding cavity (4). The lower mold (2) is fixedly connected to an injection molding pipe (28), which is connected to the molding cavity (4).

7. A foam injection molding machine according to claim 1, characterized in that: A top plate (29) is provided above the upper mold (3). Sliding columns (24) are fixedly connected to the four corners of the bottom of the top plate (29). The bottom end of the sliding column (24) is fixedly connected to the lower mold (2). A through groove is provided on the upper mold (3) for the sliding column (24) to pass through. An electric push rod (25) is fixedly connected to the top plate (29). The upper mold (3) is fixedly connected to the telescopic end of the electric push rod (25).

8. A control method for a foam injection molding machine, characterized in that: The application to the foam injection molding machine as described in any one of claims 1 to 7 further includes the following operating steps: S1. The upper mold (3) and the lower mold (2) are closed to form a molding cavity; S2. Hot water is supplied into the flow channel assembly until the temperature inside the molding cavity (4) reaches 70°C, and then the temperature is kept constant. S3. Use the inflation system to fill the molding cavity (4) with air pressure of 3-4 MPa; S4. Use a vacuum screw extruder to squeeze liquid or viscous raw materials into the molding cavity (4) until the air pressure in the molding cavity (4) reaches the preset value. Then, evacuate the gas inside the molding cavity (4) and the raw materials quickly fill the molding cavity (4) under the action of negative pressure.

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