A dual cavity mold closed film forming process

Abstract

The present application relates to a kind of double-cavity mould closed film forming process, double-cavity mould includes upper die, intermediate soft film and lower die;Lower die and intermediate soft film are cooperated to form first cavity, upper die and intermediate soft film are cooperated to form second cavity;Forming process includes the following steps: dry fiber is laid in lower die, pours into resin;Intermediate soft film and upper die are attached by negative pressure, then the mold closing between upper die and lower die is carried out and locked;First cavity is pumped, while upper die is vented, so that intermediate soft film gradually attaches to lower die, and first cavity reaches vacuum state;Again, air compressor is used to inject gas and pressurize;Using air heater to inject heating gas to cure;After curing, first cavity and second cavity are both vented;Demoulding.The forming process of the present application can rely on mould itself to play the role of negative pressure bubble removal, positive pressure compaction and high-temperature curing without large equipment, and can be moved flexibly without fixed site restriction.

Description

Technical Field

[0001] This invention relates to the field of fiberglass composite material product processing, and in particular to a double-cavity mold closed-film molding process. Background Technology

[0002] In the closed-film molding production process of fiberglass composite products, a closed cavity is formed by upper and lower molds (rigid or flexible molds), and a vacuum state is achieved by a vacuum pump to allow resin to be poured or injected.

[0003] Currently, there are many closed-mold molding processes available, including the RTM series (resin transfer molding, double hard mold / semi-hard mold closed mold), such as lightweight RTM (LRTM), vacuum-assisted RTM (VRTM), rubber diaphragm-assisted RTM (RARTM), thermal expansion core mold RTM (TERTM), and high-pressure RTM (HPRTM); vacuum infusion (single hard mold + vacuum bag sealing, soft closed mold, the most commonly used in the market) such as vacuum-assisted resin transfer molding (VARTM, VIP), SCRIMP resin infusion process, VIMP variable flow infusion process, intermediate soft film molding (CCBM), intermediate soft film infusion (VIB), etc. In addition, there are compression molding, reaction injection closed-mold molding, liquid closed-mold molding, or other special closed-mold molding methods.

[0004] The above molding methods cannot perfectly solve the problems of high quality, low material consumption, short cycle, low equipment investment, and high mobility. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a double-cavity mold closed-film molding process that is high in quality, low in material consumption, short in cycle, low in equipment investment, and highly mobile.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is: a closed-film molding process for a dual-cavity mold, the innovation of which is: the dual-cavity mold includes an upper mold, a middle soft film and a lower mold arranged sequentially from top to bottom; The lower mold has a lower cavity on its upper side, and the lower cavity and the intermediate soft film work together to form a first cavity. The first cavity is the product forming cavity, which plays the role of negative pressure, de-bubbling, and shaping. The upper mold has an upper cavity on its lower side, and the upper cavity and the intermediate soft film work together to form a second cavity. The second cavity is an auxiliary molding cavity, which plays the role of negative pressure, pressurization and heating. The lower mold is also provided with a vacuum tube, and the upper mold is also provided with an air extraction tube, a high-pressure air tube, an air heater outlet and an air heater inlet. The vacuum tube and the air extraction tube are both connected to a vacuum pump, the high-pressure air tube is connected to an air compressor, and the air heater outlet and the air heater inlet are both connected to an air heater. The molding process includes the following steps: S1: First, lay the dry fibers required for product molding in the lower cavity of the lower mold; S2: Pour the pre-prepared resin evenly into the lower cavity of the mold. S3: The middle soft film is bonded to the upper mold, and air is drawn out through the air extraction pipe on the upper mold to create a negative pressure between the middle soft film and the upper mold, so that the middle soft film and the upper mold are adsorbed and bonded together. S4: Close and lock the upper mold with the middle soft film attached to it. S5: After the mold is closed, the first cavity is evacuated, and then the second cavity is slowly degassed, so that the intermediate soft film gradually adheres to the lower mold and the first cavity reaches a vacuum state. S6: Use an air compressor to inject air and pressurize the second chamber from the high-pressure air pipe; S7: Using an air heater, heating gas is introduced into the second cavity from the air heater inlet of the upper mold to solidify the product in the first cavity; S8: After the product has cured, both the first and second cavities should be vented and the tubes should be disassembled. S9: The entire mold is moved to the demolding position using a power arm to demold the product and complete the processing.

[0007] Furthermore, the intermediate soft membrane is a soft membrane made of an intermediate soft membrane or other soft materials that can play a sealing role.

[0008] Furthermore, the fixing between the upper mold, the intermediate soft film, and the lower mold is as follows: the lower side of the upper mold has a horizontally outwardly folded upper bending structure, and the upper side of the lower mold has a horizontally outwardly folded lower bending structure. The two sides of the intermediate soft film are clamped by the cooperation of the upper bending structure and the lower bending structure. After clamping, the upper mold, the intermediate soft film, and the lower mold are fixed by the cooperation of several pressing clamps.

[0009] Furthermore, the upper end face of the lower bending structure is provided with a mold locking groove, and the middle soft film is also provided with a mold locking protrusion embedded in the mold locking groove. The two sides of the middle soft film are respectively provided with an upward folding middle bending structure that covers the side of the upper bending structure. The middle bending structure is fixed to the upper bending structure by the cooperation of fixing pins. The lower bending structure and the upper bending structure are respectively provided with mold locking air extraction nozzles.

[0010] Furthermore, in step S3, the negative pressure value is below -0.09 MPa.

[0011] Furthermore, in step S5, the vacuuming speed of the first cavity is 30-100 m3 / h, and when the pressure of the first cavity reaches -0.07 MPa or below, the upper mold begins to degas at a rate of 20-60 m3 / h.

[0012] Furthermore, in step S6, during the gas injection and pressurization, 0.5-0.8 MPa of compressed air is injected into the second cavity. If the dual-cavity mold is a fiberglass mold, the gas injection speed can reach up to 0.1 MPa / min. If the dual-cavity mold is a metal mold, the gas injection speed can reach up to 0.2 MPa / min.

[0013] Furthermore, in step S6, if there is any abnormal noise from the mold during gas injection and pressurization, pressurization should be stopped immediately. If the upper mold needs to maintain pressure, the high-pressure air pipe can be disconnected. If the lower mold needs to maintain pressure, the air extraction pipe can also be disconnected, and the mold should be moved to the turnover area. Otherwise, the pressure can only be cut off after the product has solidified.

[0014] Furthermore, in step S7, the temperature of the heating gas introduced is 40-80℃, and the introduction time is 30-90 minutes.

[0015] Furthermore, the air heater has a built-in temperature display, which allows for control of temperature and heating time.

[0016] The advantages of this invention are: the molding process of this invention can achieve negative pressure degassing, positive pressure compaction, and high temperature curing by relying solely on the mold itself without relying on large equipment. At the same time, it can be moved flexibly without the limitation of a fixed site, and is suitable for molding small and medium-sized fiberglass products such as body panels and engineering machinery covers.

[0017] In this invention, a product with quality similar to that of an autoclave can be produced using only a vacuum pump, an air compressor, and an air heater. This is equivalent to miniaturizing an autoclave and installing it on a mold, which greatly reduces equipment investment and maintenance costs, saves space, and increases the flexibility of site operation.

[0018] The molding process of this invention uses resin pouring and intermediate soft film. The mold heating system can greatly shorten the molding cycle. It is faster and more reliable than traditional RTM and vacuum bag molding, with a shorter molding cycle, reduced labor costs, and improved site utilization.

[0019] The equipment in this invention is highly replaceable; if any parts are damaged, they can be directly replaced and assembled together for immediate use. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the dual-cavity mold of the present invention. Detailed Implementation

[0021] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0022] like Figure 1 As shown, the dual-cavity mold includes an upper mold 1, a middle soft mold 2, and a lower mold 3, which are arranged sequentially from top to bottom.

[0023] The lower mold 3 has a lower cavity on its upper side, and the lower cavity and the middle soft film 2 work together to form the first cavity 4. The first cavity 4 is the product forming cavity, which plays the role of negative pressure, de-bubbling, and shaping.

[0024] A vacuum tube 31 connected to the first cavity 4 is also provided at the bottom end of the lower mold 3. The vacuum tube 31 is connected to a vacuum pump. The vacuum tube 31 is used to evacuate and release the first cavity 4. A reinforcing rib 32 is also provided on the outer wall of the bottom end of the lower mold 3, thereby improving the structural strength of the lower mold 3.

[0025] The upper mold 1 has an upper cavity on its lower side, and the upper cavity and the middle soft film 2 work together to form a second cavity 5. The second cavity 5 is an auxiliary molding cavity, which plays the role of negative pressure, pressurization and heating.

[0026] The upper mold 1 is also equipped with a vacuum pipe 11, a high-pressure air pipe 12, an air heater outlet 13, and an air heater inlet 14. The vacuum pipe 11 is connected to a vacuum pump and is used to evacuate and release air from the second cavity 5. The high-pressure air pipe 12 is connected to an air compressor and is used to introduce gas into the second cavity 5 for compression. The air heater outlet 13 and the air heater inlet 14 are both connected to an air heater so that heated gas that can circulate can be introduced into the second cavity 5. The air heater also has a temperature display and can control the temperature and heating time.

[0027] A positive and negative pressure gauge 15 is also installed on the upper mold 1 to detect the pressure of the second cavity 5, so that the operator can intuitively see the pressure status of the negative and positive pressure, providing a basis for on-site decision-making. A hook 16 is also set on both sides of the upper mold 1 to lift and move the upper mold 1.

[0028] In this embodiment, valves are also installed on the vacuum tube 31, the extraction tube 11, the high-pressure air tube 12, the air heater outlet 13, and the air heater inlet 14 to control the opening and closing of different pipes and realize operations such as pressurization, depressurization, and vacuuming.

[0029] The intermediate soft membrane 2 is a soft membrane made of an intermediate soft membrane or other soft materials that can play a sealing role.

[0030] The upper mold 1, the intermediate soft mold 2, and the lower mold 3 are fixed together as follows: the upper mold 1 has a horizontally outward-folding upper bending structure 17 on its lower side, and the lower mold 3 has a horizontally outward-folding lower bending structure 33 on its upper side. The two sides of the intermediate soft mold 2 are clamped by the combined action of the upper bending structure 17 and the lower bending structure 33. After clamping, the upper mold 1, the intermediate soft mold 2, and the lower mold 3 are fixed together by the cooperation of several pressing clamps 6. The pressing clamps 6 are commonly used pressing clamps on the market for fixing the upper and lower molds, such as quick clamps.

[0031] A mold-locking groove is provided on the upper end face of the lower bending structure 33. At the same time, a mold-locking protrusion 21 embedded in the mold-locking groove is provided on the middle soft film 2. Both sides of the middle soft film 2 are respectively provided with an upper bending structure 22 that is folded upward and covers the side of the upper bending structure 17. The middle bending structure 22 is fixed to the upper bending structure 17 by the cooperation of the fixing nail 23. A lower mold-locking air extraction nozzle 34 and an upper mold-locking air extraction nozzle 23 are respectively provided on the lower bending structure 33 and the upper bending structure 17. The design of the mold clamping groove, mold clamping protrusion 21, intermediate bending structure 22, fixing pin 23, lower mold clamping air extraction nozzle 34, and upper mold clamping air extraction nozzle 23 are all intended to stabilize the upper mold 1, intermediate soft film 2, and lower mold 3. They can provide relative positioning for the upper mold 1, intermediate soft film 2, and lower mold 3 before processing, and at the same time, they can limit the relative position of the upper mold 1, intermediate soft film 2, and lower mold 3 during processing, so as to avoid displacement of the intermediate soft film 2 under processing scenarios such as vacuuming and pressurization, which would affect the quality of subsequent product molding.

[0032] The dual-cavity mold closed-film molding process of the present invention is achieved through the following steps: S1: First, lay the dry fibers required for product molding in the lower cavity of the lower mold 3.

[0033] S2: Pour the pre-prepared resin evenly into the lower cavity of the mold 3. The amount of resin is prepared according to the requirements of the product to be molded. The resin is poured directly onto the dry fiber after being prepared in a quantitative manner, rather than being introduced by vacuum or injection. This can reduce the time for the resin to enter the membrane cavity.

[0034] S3: The intermediate soft film 2 is bonded to the upper mold 1, and air is drawn outward through the air extraction pipe 11 on the upper mold 1 to create a negative pressure between the intermediate soft film 2 and the upper mold 1. The negative pressure value is below -0.09MPa, so that the intermediate soft film 2 and the upper mold 1 are adsorbed and bonded together.

[0035] S4: The upper mold 1 and the lower mold 3, which are attached to the middle soft film 2, are closed together, and the upper mold 1 and the lower mold 3 are locked together by pressing the clamp 6.

[0036] S5: After mold closing, the first cavity 4 is evacuated at a speed of 30-100 m / s. 3 / h, and when the pressure in the first mold cavity 4 reaches -0.07MPa or below, the second cavity 5 formed between the upper mold 1 and the intermediate soft film 2 slowly degasses at a rate of 20-60m / h. 3 / h, through this slow degassing speed, the intermediate soft film 2 is prevented from suddenly sagging and wrinkling. The intermediate soft film 2 gradually adheres to the lower mold 3, and the first cavity 4 reaches a vacuum state. This process can remove air bubbles from the resin.

[0037] When evacuating the first chamber 4, the air should be evacuated slowly and not instantly to prevent the resin in the first chamber 4 from boiling suddenly. This would cause the resin or a large amount of volatiles to be discharged through the vacuum tube 31, affecting the fiber impregnation and curing degree. The defoaming process should be controlled within 5 minutes.

[0038] Similarly, when venting the second cavity 5, it is not allowed to vent all at once to prevent the middle soft film 2 from suddenly falling down and misaligning with the lower mold 3, resulting in uneven product wall thickness.

[0039] S6: Use an air compressor to inject and pressurize air into the second chamber 5 from the high-pressure air pipe 12. During the air injection and pressurization, inject 0.5-0.8MPa compressed air into the first chamber 4. If the dual-chamber mold is a fiberglass mold, the air injection speed can reach up to 0.1MPa / min. If the dual-chamber mold is a metal mold, the air injection speed can reach up to 0.2MPa / min. When injecting air, use a step-by-step pressurization method and pay close attention to the mold status. If there is any abnormal noise from the mold, stop pressurizing immediately. If the upper mold needs to maintain pressure, the high-pressure air pipe can be disconnected. If the lower mold needs to maintain pressure, the air extraction pipe can also be disconnected. Move the mold to the turnover area. Otherwise, the pressure can only be cut off after the product has cured.

[0040] In this method, the product is simultaneously subjected to the vacuum adsorption pressure of the first mold cavity 4 and the additional compressed air pressure provided by the second mold cavity 5. This dual pressure can increase the fiber content of the product and reduce the amount of air bubbles.

[0041] S7: Using an air heater, heating gas is introduced into the second cavity 5 from the air heater inlet 13 of the upper mold 1 to solidify the product in the first cavity 4. The temperature of the introduced heating gas is generally 40-80℃, and the heating time is 30-90 minutes. If the temperature is low, the time can be appropriately extended until the product hardens.

[0042] When heating, if the double-cavity mold is a metal mold and the middle soft film 2 is made of high-temperature resistant soft film, the temperature of the heating gas can reach up to 150℃. S8: After the product has cured, both the first cavity 4 and the second cavity 5 are vented and the tubes are disassembled.

[0043] S9: The entire mold is moved to the demolding position using a power arm to demold the product and complete the processing.

[0044] Throughout the entire molding process described above, operators can adjust parameters in real time by monitoring the pressure and temperature between the upper mold 1 and the intermediate soft film 2.

[0045] In the molding process of this invention, the negative pressure provided by the upper mold 1 can adsorb the intermediate soft film 2 onto the upper mold 1, and the pouring of resin can reduce the pouring time. The negative pressure of the lower mold 3 can remove the air bubbles in the poured resin. Then the intermediate soft film 2 falls down and fits with the lower mold 3. The upper mold 1 is then pressurized to discharge excess resin, increase the fiber content, and at the same time prevent air from leaking into the product through the air leakage point of the lower mold 3. The air circulation heating in the upper mold 2 can accelerate the resin reaction and shorten the curing time.

[0046] The molding process of this invention can achieve negative pressure defoaming, positive pressure compaction, and high-temperature curing using only the mold itself, without relying on large equipment. It is also flexible and has no fixed site restrictions, making it suitable for molding small and medium-sized fiberglass products such as vehicle body panels and engineering machinery covers.

[0047] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A closed-film molding process using a dual-cavity mold, characterized in that: The dual-cavity mold includes an upper mold, a middle soft mold, and a lower mold arranged sequentially from top to bottom; The lower mold has a lower cavity on its upper side, and the lower cavity and the intermediate soft film work together to form a first cavity. The first cavity is the product forming cavity, which plays the role of negative pressure, de-bubbling, and shaping. The upper mold has an upper cavity on its lower side, and the upper cavity and the intermediate soft film work together to form a second cavity. The second cavity is an auxiliary molding cavity, which plays the role of negative pressure, pressurization and heating. The lower mold is also provided with a vacuum tube, and the upper mold is also provided with an air extraction tube, a high-pressure air tube, an air heater outlet and an air heater inlet. The vacuum tube and the air extraction tube are both connected to a vacuum pump, the high-pressure air tube is connected to an air compressor, and the air heater outlet and the air heater inlet are both connected to an air heater. The molding process includes the following steps: S1: First, lay the dry fibers required for product molding in the lower cavity of the lower mold; S2: Pour the pre-prepared resin evenly into the lower cavity of the mold. S3: The middle soft film is bonded to the upper mold, and air is drawn out through the air extraction pipe on the upper mold to create a negative pressure between the middle soft film and the upper mold, so that the middle soft film and the upper mold are adsorbed and bonded together. S4: Close and lock the upper mold with the middle soft film attached to it. S5: After the mold is closed, the first cavity is evacuated, and then the second cavity is slowly degassed, so that the intermediate soft film gradually adheres to the lower mold and the first cavity reaches a vacuum state. S6: Use an air compressor to inject air and pressurize the second chamber from the high-pressure air pipe; S7: Using an air heater, heating gas is introduced into the second cavity from the air heater inlet of the upper mold to solidify the product in the first cavity; S8: After the product has cured, both the first and second cavities should be vented and the tubes should be disassembled. S9: The entire mold is moved to the demolding position using a power arm to demold the product and complete the processing.

2. The closed-film molding process with a dual-cavity mold according to claim 1, characterized in that: The intermediate soft membrane is a soft membrane made of an intermediate soft membrane or other soft materials that can play a sealing role.

3. The closed-film molding process with a dual-cavity mold according to claim 1, characterized in that: The upper mold, the intermediate soft film, and the lower mold are fixed as follows: the upper mold has a horizontally outward folding upper bending structure on its lower side, and the lower mold has a horizontally outward folding lower bending structure on its upper side. The two sides of the intermediate soft film are clamped by the cooperation of the upper bending structure and the lower bending structure. After clamping, the upper mold, the intermediate soft film, and the lower mold are fixed by the cooperation of several pressing clamps.

4. The closed-film molding process with a dual-cavity mold according to claim 3, characterized in that: The upper end face of the lower bending structure is also provided with a mold locking groove, and the middle soft membrane is also provided with a mold locking protrusion embedded in the mold locking groove. The two sides of the middle soft membrane are also provided with an upward folding middle bending structure that covers the side of the upper bending structure. The middle bending structure is fixed to the upper bending structure by the cooperation of fixing pins. The lower bending structure and the upper bending structure are also provided with mold locking air extraction nozzles respectively.

5. The closed-film molding process with a dual-cavity mold according to claim 1, characterized in that: In step S3, the negative pressure value is below -0.09 MPa.

6. The closed-film molding process with a dual-cavity mold according to claim 1, characterized in that: In step S5, the vacuuming speed of the first cavity is 30-100 m / s. 3 / h, and when the pressure in the first cavity reaches -0.07MPa or below, the upper mold begins to depressurize at a rate of 20-60m / h. 3 / h.

7. The closed-film molding process with a dual-cavity mold according to claim 1, characterized in that: In step S6, during the pressurization process, compressed air at 0.5-0.8 MPa is injected into the second cavity. If the dual-cavity mold is a fiberglass mold, the maximum air injection rate is 0.1 MPa / min. If the dual-cavity mold is a metal mold, the maximum air injection rate is 0.2 MPa / min.

8. The closed-film molding process with a dual-cavity mold according to claim 1, characterized in that: In step S6, if there is any abnormal noise from the mold during gas injection and pressurization, pressurization should be stopped immediately. If the upper mold needs to maintain pressure, the high-pressure air pipe can be disconnected. If the lower mold needs to maintain pressure, the air extraction pipe can also be disconnected. The mold should be moved to the turnover area. Otherwise, the pressure can only be cut off after the product has solidified.

9. The closed-film molding process with a dual-cavity mold according to claim 1, characterized in that: In step S7, the temperature of the heating gas introduced is 40-80℃, and the introduction time is 30-90 minutes.

10. The closed-film molding process with a dual-cavity mold according to claim 1, characterized in that: The air heater has a built-in temperature display and can control the temperature and heating time.

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