An integrated molding tool and method for thermo-plastic composite molding combined with injection molding

Abstract

The application provides a kind of thermoplastic composite mould pressing combined injection molding integrated forming die and method.The die includes upper die and lower die, the cavity is formed between the upper die and lower die, the inner wall of the upper die and lower die corresponding cavity area is provided with groove for forming reinforcing rib structure;The injection mold is provided with hot runner system, the hot runner system includes needle valve gate and side gate;The needle valve gate is set on the side of the upper die, and is communicated with the groove on the side of the upper die, for injection molding part close to the reinforcing rib on one side of the upper die, the side gate is set at the parting surface of the upper die and the lower die, and is communicated with the plastic structure groove on the side of the lower die, for injection molding part close to the reinforcing rib on one side of the lower die.In the die, after laying fiber felt material, first, mould pressing is formed, then, the mold is injected with molten plastic, and the reinforcing rib is formed.The process realizes "one clamping, one positioning, one forming", and improves production efficiency.

Description

Technical Field

[0001] This invention relates to the field of composite material molding technology, specifically to an integrated molding die and method for thermoplastic composite material compression molding combined with injection molding. Background Technology

[0002] Carbon fiber composites, due to their excellent properties of being lightweight and high-strength, have been widely used in aerospace, automotive manufacturing, and sporting goods. Carbon fiber felt, as a common carbon fiber reinforced material, has advantages such as low cost and good isotropy. Its main molding methods include hand lay-up, vacuum casting, wet molding, HP-RTM process, and prepreg board rubbing molding. While composite products made from carbon fiber felt possess certain strength and appearance quality, they exhibit the following significant drawbacks when used in automotive structural components: Insufficient mechanical properties: Compared to woven carbon fiber fabrics and unidirectional tapes, carbon fiber felt lacks continuous oriented fibers. Its internal fibers are randomly and irregularly overlapped, with only weak point contact between fibers, making load transfer difficult. Consequently, its tensile and flexural strengths are low, resulting in poor load-bearing capacity, making it unsuitable for direct use as a primary load-bearing structural component. Weak interlayer bonding: Carbon fiber felt fibers rely solely on physical overlap, lacking a woven interlocking structure. This leads to low interlayer shear strength in composite parts, making them prone to delamination and fiber peeling under impact. Large dispersion in mechanical properties: While the directional differences are smaller compared to woven fabrics and unidirectional tapes, the random fiber distribution results in uneven fiber density in different areas, causing significant fluctuations in the mechanical properties of the products and poor batch consistency. Insufficient compressive performance: Porous carbon felt is prone to compaction and creep under pressure, with fibers slipping against each other. Irreversible compressive deformation occurs under long-term loads, making it unsuitable for long-term pressure-bearing structures.

[0003] Due to the aforementioned limitations in mechanical properties, products molded from carbon fiber felt typically require direct reinforcement with metal parts or the addition of reinforcing ribs to meet strength standards. For reinforcing ribs, current technology usually separates the molding of the carbon fiber felt from the injection molding of the reinforcing ribs: first, the carbon fiber felt is hot-pressed in a molding machine, and then the molded part is transferred to an injection molding machine for the injection molding of the reinforcing ribs. This step-by-step molding method has the following problems: First, the process is complicated and requires a lot of equipment. The molding and injection molding processes are completed on molding and injection molding equipment respectively, requiring two clamping and two positioning operations, resulting in a large investment in equipment and a large space requirement; Secondly, the process is time-consuming and inefficient. After compression molding, the product needs to be cooled, removed, transported, re-clamped, and then re-injected, resulting in a long cycle time with each finished product taking approximately 15 minutes on average. Third, injection molding of double-sided reinforcing rib structures is difficult. Forming reinforcing ribs simultaneously on both the front and back sides of the fiber-molded matrix requires solving the problem of synchronous filling of the molten plastic on both sides. Therefore, there is an urgent need in this field for an integrated molding technology that can continuously complete the compression molding of carbon fiber felt and the injection molding of reinforcing ribs on the same mold and machine, so as to simplify the process, improve production efficiency, ensure product precision and reduce manufacturing costs. Summary of the Invention

[0004] To address the technical problems of existing technologies involving the compression molding of carbon fiber felt and the injection molding of reinforcing ribs, such as cumbersome processes, large equipment requirements, poor product dimensional accuracy, long processing time, and difficulty in injection filling of double-sided reinforcing ribs, this invention provides an integrated molding die and method for thermoplastic composite materials that combines compression molding and injection molding.

[0005] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, a one-piece molding die for thermoplastic composite material compression molding combined with injection molding is provided, including an upper die and a lower die, with a part cavity formed between the upper die and the lower die. Grooves for molding reinforcing ribs are provided on the inner walls of corresponding cavity areas of the upper die and the lower die. The injection mold is provided with a hot runner system, which includes a needle valve gate and a side gate. The needle valve gate is located on the upper die side and communicates with the groove on the upper die side, for injection molding of reinforcing ribs on the side of the part close to the upper die. The side gate is located at the parting surface between the upper die and the lower die and communicates with the groove on the lower die side, for injection molding of reinforcing ribs on the side of the part close to the lower die.

[0006] In another embodiment, the mold further includes sheet positioning posts disposed on the surface of the lower mold core for positioning the carbon fiber felt material placed in the lower mold. There are multiple sheet positioning posts distributed around the central area of ​​the molding cavity.

[0007] In another embodiment, the mold has multiple needle valve gates distributed on the upper mold side for forming multi-point injection on the front side of the carbon fiber molding matrix; and multiple side gates distributed on the periphery of the molding cavity for forming multi-point injection on the back side of the carbon fiber molding matrix.

[0008] In another embodiment, the mold further includes an ejection mechanism disposed in the lower mold for ejecting the finished part after mold opening.

[0009] In another embodiment, the mold further includes a heating system comprising heating elements (such as electric heating rods) disposed inside the upper and lower molds for heating the mold to the temperature required for compression molding.

[0010] In another embodiment, the mold further includes a cooling system comprising cooling channels disposed inside the upper mold and the lower mold for cooling the product within the molding cavity.

[0011] In another embodiment, the hot runner system further includes a sequence valve control device connected to the needle valve gate and the side gate, for controlling the opening sequence and opening time of each gate.

[0012] Secondly, the present invention provides an integral molding method for thermoplastic composite materials combining compression molding and injection molding, comprising the following steps: Step 1: Prepare a mold for both compression molding and double-sided injection molding. Step 2: Lay and position the heated and softened carbon fiber felt; place the carbon fiber felt into the injection mold and position it using the positioning pins set in the injection mold; Step 3: Compression Molding; The upper and lower molds are driven to close by the mold closing action of the injection molding machine to compress the carbon fiber felt material, forming a carbon fiber molded matrix; Specifically, the mold closing mechanism of the injection molding machine drives the upper mold to move towards the lower mold, and the upper and lower molds gradually close; During the mold closing process, the mold core surfaces of the upper mold and the lower mold jointly apply pressure to the carbon fiber felt material, causing the carbon fiber felt material to deform under high temperature and high pressure, conforming to the shape of the molding cavity, forming the carbon fiber molded matrix; During the compression molding process, the magnitude of the compression pressure is determined according to factors such as the thickness and area of ​​the carbon fiber felt material and the molding temperature; Step 4: Injection Molding of Plastic Reinforcing Ribs; After compression molding, molten plastic is injected into the molding cavity through the hot runner system. Plastic is simultaneously injected into the front and back of the carbon fiber mold substrate via the needle valve gate and the side gate, respectively, filling the grooves inside the mold and forming the front and back plastic reinforcing rib structures. Specifically, after the carbon fiber felt is compression molded, the injection molding machine remains in the mold-closed state and injects molten plastic into the molding cavity through the hot runner system. The needle valve gate is used to inject plastic into the front of the carbon fiber mold substrate; the side gate is used to inject plastic into the back of the carbon fiber mold substrate. The combined use of the needle valve gate and the side gate allows the molten plastic to enter the grooves of the molding cavity simultaneously from both the front and back sides, forming plastic reinforcing rib structures on both the front and back sides of the carbon fiber mold substrate. The position, shape, size, and quantity of the front and back plastic reinforcing rib structures are determined according to the mechanical performance requirements of the product. The reinforcing rib structure can be mesh-like, radial, strip-like, or any combination of shapes. The molten plastic is preferably a thermoplastic, such as polypropylene (PP), polyamide (PA), polyetheretherketone (PEEK), polyphenylene sulfide (PPS), etc. Step 5: Pressure Holding and Cooling; After holding pressure for a certain period of time, cooling is performed to allow the carbon fiber molded matrix, the front plastic reinforcing rib structure, and the back plastic reinforcing rib structure to solidify integrally. Specifically, after injection molding, the injection molding machine remains in the mold-closed state, holding pressure on the molten plastic in the molding cavity to compensate for the volume reduction caused by the cooling shrinkage of the plastic. After holding pressure, the mold enters the cooling stage. To achieve rapid cooling, cooling water channels can be installed inside the mold to quickly cool the product, allowing the plastic reinforcing rib structure to fully solidify and simultaneously forming a strong bonding interface between the carbon fiber molded matrix and the plastic reinforcing rib structure.

[0013] Step 6: Mold opening and part removal; Specifically, after cooling, the injection molding machine opens the mold, the upper mold moves upward and separates from the lower mold, and the ejection mechanism (such as ejector plate, ejector pin, etc.) set in the lower mold ejects the finished part from the lower mold and removes the finished part. At this point, a complete molding cycle is completed.

[0014] Preferably, the molding pressure range in step three is 20-160 bar, the molding temperature is determined according to the type of thermoplastic matrix in the carbon fiber felt, and is usually 50℃~150℃. The molding time (i.e., the mold closing and pressure holding time) is preferably 1s~60s. Preferably, in step five, the holding pressure for pressure holding and cooling is 15 bar to 150 bar, the holding time is 0 s to 30 s, and the cooling time is 60 s to 150 s. The cooling channels are located inside the upper and lower molds, and the cooling medium is preferably water or oil, with the cooling temperature determined according to the type of plastic.

[0015] Thirdly, the present invention provides an integrally molded part of thermoplastic composite material by compression molding and injection molding, prepared using the above-described mold or method, the part comprising: The carbon fiber molded matrix is ​​obtained by molding carbon fiber felt. The front plastic reinforcing rib structure is integrally molded on the front of the carbon fiber molded matrix; The back plastic reinforcing rib structure is integrally molded on the back of the carbon fiber molded matrix; The front plastic reinforcing rib structure and the back plastic reinforcing rib structure are respectively integrated with the carbon fiber molded matrix by injection molding.

[0016] In the product, the carbon fiber molded matrix serves as the main structural component, providing basic mechanical properties and shape contours. The front and back plastic reinforcing ribs act as reinforcement structures, significantly improving the overall strength, stiffness, and load-bearing capacity of the product. Because the carbon fiber molded matrix and the plastic reinforcing ribs are integrally molded in the mold, a strong physical and chemical bonding interface is formed between them, eliminating the need for additional bonding processes.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. Process integration, one-step molding. This invention integrates the molding process of carbon fiber felt and the injection molding process of reinforcing ribs into the same mold, realizing "one clamping, one positioning, one molding". Compared with the traditional process where molding and injection molding are carried out in separate steps, this invention reduces the number of tooling and inspection molds, simplifies the process flow, and reduces equipment investment and space occupation.

[0018] 2. High product precision. Because the molding of carbon fiber felt and the injection molding of plastic reinforcing ribs are completed continuously in the same mold, the product does not require secondary clamping and positioning during the entire molding process. This avoids the positioning errors caused by process transfer in traditional processes, and significantly improves the dimensional accuracy of the product structure.

[0019] 3. Significantly improved production efficiency. In traditional processes, carbon fiber felt needs to be cooled, demolded, transported, clamped, and then injected again after molding. The entire process is lengthy, with an average of 40 minutes per finished product. This invention, however, completes molding and injection molding continuously, shortening the molding cycle per unit and increasing production efficiency several times over.

[0020] 4. Simultaneous injection filling of double-sided reinforcing rib structure is achieved. This invention, through a hot runner system combining needle valve gate and side gate, enables simultaneous injection filling of plastic on both the front and back sides of the carbon fiber molded matrix, solving the injection filling problem of double-sided plastic reinforcing rib structure. Furthermore, the injection timing of each gate can be optimized through a sequence valve control device, improving injection quality. Attached Figure Description

[0021] Figure 1 A schematic diagram of the structure of a one-piece molded product combining carbon fiber thermoplastic molding and double-sided injection molding; Figure 2 A schematic diagram of the front structure of a one-piece molded product combining carbon fiber thermoplastic molding and double-sided injection molding; Figure 3 A schematic diagram of the back structure of a one-piece molded product combining carbon fiber thermoplastic molding and double-sided injection molding; Figure 4 This is a schematic diagram of the AA section structure; Figure 5 This is a schematic diagram of a mold structure for a double-sided injection molding process combining compression molding and traditional Chinese molding. Figure 6 This is a schematic diagram of the enlarged structure of Part I; Figure 7 This is a schematic diagram of the lower mold structure; Figure 8 This is a schematic diagram of the hot runner system structure; The meanings of the numbers marked in the diagram are as follows: 1—Upper mold; 2—Lower mold; 3—Cavity; 4—Groove; 5—Hot runner system; 51—Needle valve gate; 52—Side gate; 6—Positioning pin; 7—Carbon fiber molding matrix; 8—Plastic reinforcing rib. Detailed Implementation

[0022] 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 a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0023] In the description of this invention, the terms "upper", "lower", "front", "back", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0024] The terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0025] See appendix Figures 1 to 3This illustrates a monolithic part made of thermoplastic composite material through compression molding combined with double-sided injection molding, comprising: The carbon fiber molded matrix is ​​obtained by molding carbon fiber felt; the areal density of the carbon fiber felt is 1050±50 g / m², and the thickness after molding is 5 mm. The front plastic reinforcing rib structure is integrally molded on the front of the carbon fiber molded matrix; The back plastic reinforcing rib structure is integrally molded on the back of the carbon fiber molded matrix; The front plastic reinforcing rib structure and the back plastic reinforcing rib structure are respectively integrated with the carbon fiber molded matrix by injection molding.

[0026] See appendix Figures 4 to 7 The diagram illustrates a compression-bonded double-sided injection molding die for molding the aforementioned part, comprising an upper die 1 and a lower die 2, with a cavity 3 formed between the upper die 1 and the lower die 2. Grooves 4 for molding reinforcing ribs are provided on the inner walls of the corresponding areas of the cavity 3 in the upper die 1 and the lower die 2. The injection mold also includes a hot runner system 5, comprising a needle valve gate 51 and a side gate 52. The needle valve gate 51 is located on one side of the upper die 1 for injection molding the reinforcing ribs near it, and the side gate 52 is located at the parting surface between the upper die 1 and the lower die 2 for injection molding the reinforcing ribs on the other side.

[0027] The mold also includes sheet positioning posts 6, which are disposed on the surface of the mold core of the lower mold 2 and are used to position the fiber felt material placed in the lower mold 2. There are multiple sheet positioning posts 6, which are distributed around the central area of ​​the molding cavity 3.

[0028] There are multiple needle valve gates 51, which are distributed on the side of the upper mold 1 and are used to form multi-point injection on the front side of the carbon fiber molding substrate 7; there are multiple side gates 52, which are distributed on the periphery of the molding cavity 3 and are used to form multi-point injection on the back side of the carbon fiber molding substrate 7.

[0029] The mold also includes an ejection mechanism disposed in the lower mold for ejecting the finished part after mold opening. The mold further includes a heating system comprising heating elements, such as electric heating rods, disposed inside the upper and lower molds for heating the mold to the temperature required for compression molding. The mold also includes a cooling system comprising cooling water channels disposed inside the upper and lower molds for cooling the product within the molding cavity via circulating water. The above structures are prior art and will not be elaborated further here.

[0030] The above-mentioned method for integral molding of parts by compression molding combined with double-sided injection molding includes: Step 1: Prepare a mold for both compression molding and double-sided injection molding; Step 2: Place the heated and softened carbon fiber felt into the lower mold cavity; positioning holes are made in the carbon fiber felt to cooperate with the felt positioning posts on the mold to achieve the positioning of the carbon fiber felt; Step 3: Compression molding; Close the upper and lower molds, and use the mold closing mechanism of the injection molding machine to drive the upper mold to move towards the lower mold and close the mold. The compression pressure is 80 bar, the mold temperature is controlled at 80±5℃, and the pressure is held for at least 1 second to compress the carbon fiber felt into a carbon fiber molded matrix. Step 4: Injection molding of plastic reinforcing ribs; After compression molding, keep the mold closed and inject molten plastic into the hot runner system. The molten plastic enters the molding cavity through the needle valve gate and side gate respectively, filling the grooves on the inner wall of the cavity, thereby forming the reinforcing rib structure.

[0031] Step 5: Pressure Holding and Cooling; After injection molding, the injection molding machine remains in the mold closed state and holds the molten plastic in the molding cavity under pressure of 30 bar for 0.5 seconds; After pressure holding, the part is cooled through the cooling water channels in the mold for 90 seconds to allow the plastic reinforcing rib structure to fully solidify.

[0032] Step 6: Mold opening and part removal; Specifically, after cooling, open the mold, use the ejection mechanism to eject the part from the mold, and then remove it.

[0033] In this embodiment, the carbon fiber molded matrix of the part is integrally formed with the plastic reinforcing ribs on the front and back. The molding cycle of a single part is about 5 minutes (including the part removal time). Compared with the prior art, which first forms the carbon fiber molded matrix in the molding mold and then transfers it to the injection mold to form the reinforcing rib structure, the time saved per part is about 35 minutes.

[0034] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A thermoplastic composite material compression molding combined with double-sided injection molding integral molding mold, comprising an upper mold and a lower mold, wherein a part cavity is formed between the upper mold and the lower mold, characterized in that, The inner walls of the corresponding cavity areas of the upper and lower molds are provided with grooves for forming reinforcing rib structures; the injection mold is provided with a hot runner system, which includes a needle valve gate and a side gate; the needle valve gate is located on the upper mold side and communicates with the groove on the upper mold side, and is used for injection molding of reinforcing ribs on the side of the molded part close to the upper mold; the side gate is located at the parting surface between the upper and lower molds and communicates with the groove on the lower mold side, and is used for injection molding of reinforcing ribs on the side of the molded part close to the lower mold.

2. The thermoplastic composite material molding and double-sided injection molding integrated mold according to claim 1, characterized in that, The mold also includes positioning pins, which are disposed on the surface of the mold core of the lower mold and are used to position the fiber felt material placed in the lower mold.

3. The thermoplastic composite material molding and double-sided injection molding integrated mold according to claim 1, characterized in that, The needle valve gates are multiple and distributed on the upper mold side, used to form multi-point injection on one side of the fiber molding matrix; the side gates are multiple and arranged circumferentially along the edge of the molding cavity, used to form multi-point injection on the other side of the carbon fiber molding matrix.

4. The thermoplastic composite material compression molding combined with double-sided injection molding integral molding die according to claim 1, characterized in that, The mold also includes an ejection mechanism disposed in the lower mold, used to eject the finished part after the mold is opened.

5. The thermoplastic composite material molding and double-sided injection molding integrated mold according to claim 1, characterized in that, The mold also includes a heating system, which includes heating elements disposed inside the upper mold and the lower mold for heating the mold to the temperature required for compression molding.

6. The thermoplastic composite material compression molding combined with double-sided injection molding integral molding die according to claim 1, characterized in that, The mold also includes a cooling system, which includes cooling water channels disposed inside the upper mold and the lower mold for cooling the product inside the molding cavity.

7. A method for integral molding of thermoplastic composite materials using compression molding combined with double-sided injection molding, characterized in that, Based on the molding die according to any one of claims 1-6, the process includes the following steps: Step 1: Prepare a mold for both compression molding and double-sided injection molding; Step 2: Lay and position the heated and softened fiber felt on the mold; Step 3: Compression molding; The upper and lower molds are closed to compress the carbon fiber felt material in the cavity to form a fiber-molded matrix; Step 4: Injection molding of plastic reinforcing ribs; After compression molding is completed, molten plastic is injected into the molding cavity through the hot runner system. The plastic is then filled into the grooves inside the mold cavity through the needle valve gate and side gate, forming plastic reinforcing rib structures on the front and back sides of the fiber molding matrix. Step 5: Pressure holding and cooling; After a certain period of pressure holding and cooling, the fiber molding matrix and the plastic reinforcing ribs on the front and back sides are solidified and formed as a whole. Step 6: Open the mold and remove the finished part; specifically, after cooling, open the mold and use the ejection mechanism to eject the finished part from the mold and remove the finished part.

8. The method for integral molding of thermoplastic composite materials by compression molding and double-sided injection molding according to claim 7, characterized in that, In step three, during compression molding, the molding pressure ranges from 20 to 160 bar, the molding temperature is from 50°C to 150°C, and the molding time is from 1 to 60 seconds.

9. A method for integral molding of thermoplastic composite materials by compression molding and double-sided injection molding according to claim 7, characterized in that, The pressure holding and cooling process in step five involves a pressure of 15 bar to 100 bar, a holding time of 0 s to 30 s, and a cooling time of 60 s to 150 s.

10. A thermoplastic composite material molded integrally formed part by double-sided injection molding, characterized in that, The product is prepared using a mold as described in any one of claims 1 to 6 or a molding method as described in any one of claims 7 to 9, and the product comprises: The carbon fiber molded matrix is ​​obtained by molding carbon fiber felt. The front plastic reinforcing rib structure is integrally molded with the front of the fiber molded matrix; The back plastic reinforcing rib structure is integrally molded with the back of the carbon fiber molded matrix; The front plastic reinforcing rib structure and the back reinforcing rib structure are respectively integrated with the carbon fiber molded matrix by injection molding.

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