Exhaust control equipment and method for hot press molding of fiber composite material

Abstract

The invention relates to the technical field of composite material processing, and discloses exhaust control equipment for fiber composite material hot press molding, which comprises a bottom plate, a bracket is mounted on the bottom plate, an oil cylinder is mounted at the top of the bracket, a top plate is fixedly connected to the output end of the oil cylinder, and an upper heating plate is arranged at the bottom of the top plate; a lower heating plate installed on the bottom plate is arranged in the support, a mold is installed above the lower heating plate, the oil cylinder stretches out and draws back to drive the mold to complete mold closing and mold opening actions, and a vacuum cover is arranged above the mold. The action logic of the hot pressing equipment is optimized according to different material characteristics, the efficient and accurate exhaust control method and the matched equipment are provided, the problem of poor products caused by uneven glue flowing and insufficient exhaust is solved through sufficient exhaust and uniform glue flowing, the product forming quality and the production yield are improved, and the production cost is reduced.

Description

Technical Field

[0001] This invention belongs to the field of composite material processing technology, specifically relating to the exhaust control method and supporting equipment for hot pressing of glass fiber prepreg sheets. It is particularly suitable for the mass production of high-precision glass fiber composite material products such as mobile phone back covers and laptop shells that have strict requirements for appearance accuracy and structural strength. It can achieve precise hot pressing according to different material properties. Background Technology

[0002] With the rapid development of the consumer electronics industry, the requirements for appearance precision and structural strength of terminal products such as smartphones and laptops are constantly increasing, and product structures are becoming increasingly complex. Fiberglass composite materials are widely used in the production of related products due to their excellent mechanical properties and lightweight characteristics. However, existing hot-pressing processes for fiberglass composite materials have the following key problems: Smaller protrusions and grooves on the back of the product are prone to incomplete molding and insufficient glue, which affects the product's structural strength and assembly accuracy. If the release film does not adhere completely to the product surface during hot pressing, residual air inside the cavity cannot be expelled, resulting in bubble marks on the product surface after molding, which reduces the appearance pass rate. The complex structure on the back of the product results in uneven pressure transmission during hot pressing, causing obvious structural marks on the front and affecting the consistency of appearance.

[0003] The aforementioned problems resulted in low product yield, increased raw material waste and production costs, making it difficult to meet end customers' demand for mass production of high-precision glass fiber composite products, and hindering the further promotion and application of glass fiber composite materials in the consumer electronics field. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects in appearance and structure of existing glass fiber composite hot pressing molding processes, such as insufficient glue on the back of the product, incomplete filling, and surface bubbles and structural marks. It optimizes the operation logic of hot pressing equipment for different material characteristics and provides an efficient and precise venting control method and supporting equipment. By ensuring sufficient venting and uniform glue flow, it solves the product defects caused by uneven glue flow and insufficient venting, improves product molding quality and production yield, and reduces production costs.

[0005] The present invention provides the following technical solution: an exhaust control device for hot pressing of fiber composite materials, including a base plate, a bracket installed on the base plate, a hydraulic cylinder installed on the top of the bracket, a top plate fixedly connected to the output end of the hydraulic cylinder, an upper heating plate configured at the bottom of the top plate, a lower heating plate installed on the base plate inside the bracket, a mold installed above the lower heating plate, and the extension and retraction of the hydraulic cylinder drives the mold to complete the mold closing and opening actions, and a vacuum hood is provided above the mold.

[0006] Furthermore, the mold is located below the top plate and carries the glass fiber composite material blank, with the internal cavity of the mold adapted to the structure of the target product.

[0007] Furthermore, the vacuum hood can be raised and lowered and positioned above the mold, and its opening and closing are controlled by a lifting mechanism. The vacuum hood can cover the mold and extract air from the mold cavity.

[0008] Furthermore, a method for controlling exhaust gas in hot pressing of fiber composite materials, using the aforementioned exhaust gas control equipment for hot pressing of fiber composite materials, includes the following steps: S1. Blank preparation and positioning: Place the laminated fiberglass cloth and epoxy resin prepreg into the mold to ensure that the blank is laid flat. Then move the mold to the preset position of the lower heating plate. S2. Vacuum Cover and Vacuuming: The vacuum cover descends and precisely covers the mold. The vacuum system is activated to vacuum the mold cavity, so that the vacuum level inside the cavity reaches the preset vacuum level threshold. S3. Initial Pressing Down: The hydraulic cylinder drives the top plate to move downward, causing the mold to close until the pressure on the mold reaches the preset pressure value or the top plate moves to the preset pressing position. The hydraulic cylinder then stops pressurizing. S4. Lifting and Pausing: The hydraulic cylinder drives the top plate to move in the opposite direction, causing the mold to open slightly and pause for 1-2 seconds, so that the residual air and excess epoxy resin inside the mold cavity can be released. S5. Secondary pressure: The hydraulic cylinder drives the top plate to move downward again, causing the mold to close again until the preset pressure value or preset pressure position is reached, completing a complete venting action. S6. Circulating exhaust: Repeat the exhaust action in steps 3-5 until the preset number of exhaust cycles is completed; S7. Pressure Holding and Curing: After the venting is completed, the hydraulic cylinder is kept under pressure for pressure holding and curing. The pressure holding time is 100-300 seconds. During the pressure holding process, the preset pressure value and molding temperature are maintained to ensure that the epoxy resin is fully cured. S8. Stepped cooling and demolding: After pressure holding and curing, the product is cooled down according to the preset stepped cooling process. After cooling to the preset temperature of 40℃-45℃, it is demolded to obtain a high-precision glass fiber composite material product.

[0009] The present invention has the following beneficial effects: 1. This invention optimizes the operation logic of hot pressing equipment for different material properties, providing an efficient and precise exhaust control method and supporting equipment. By ensuring sufficient exhaust and uniform glue flow, it solves the product defects caused by uneven glue flow and insufficient exhaust, improves product molding quality and production yield, and reduces production costs.

[0010] 2. This invention effectively removes residual air from the mold cavity through a cyclic venting action of "pressing down - lifting and holding - pressing down again," including residual air between multiple layers of materials. This promotes uniform flow of epoxy resin, thereby greatly reducing the defect rate of bubble prints, incomplete glue structure, and structural print defects, improving production quality, reducing raw material waste and rework costs, and enhancing the economics of mass production.

[0011] 3. This invention can adapt to high-precision glass fiber composite material products of different sizes and structures by presetting different process parameters through the control system. It can also be flexibly adjusted according to material characteristics such as glass fiber cloth weight and semi-cured sheet adhesive content. It has strong versatility and the entire process is automatically controlled. The parameters can be precisely adjusted to avoid human operation errors and ensure product quality consistency. Furthermore, it can be achieved by optimizing the action logic and control parameters on the basis of existing hot pressing equipment. The modification cost is low and it is easy to promote industrially. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the structure of the invention. Figure 2 This is a schematic diagram of the overall structure of the present invention.

[0013] In the diagram: 1. Lower heating plate; 2. Mold; 3. Vacuum hood; 4. Oil cylinder; 5. Top plate; 6. Upper heating plate; 7. Bottom plate. Detailed Implementation

[0014] 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.

[0015] Please see Figure 1-2A venting control device for hot pressing of fiber composite materials includes a base plate 7, a bracket mounted on the base plate 7, a hydraulic cylinder 4 mounted on the top of the bracket, and a top plate 5 fixedly connected to the output end of the hydraulic cylinder 4. The extension and retraction of the hydraulic cylinder 4 drives the mold 2 to complete the mold closing and opening actions. An upper heating plate 6 is arranged at the bottom of the top plate 5, and a lower heating plate 1 is installed inside the bracket and mounted on the base plate 7. The upper heating plate 6 and the lower heating plate 1 cooperate to heat the blank inside the mold 2. The heating plates are heated by direct electric heating or indirect heat medium circulation heating, and the heating plates integrate temperature control devices. A temperature sensor monitors the plate temperature in real time and feeds the data back to the control system. The system controls the temperature by adjusting the electric heating power or the flow rate of the heat medium. The heating plate is equipped with a built-in cooling device to achieve gradual cooling. A mold 2 is installed above the lower heating plate 1 and is located below the top plate 5. The mold 2 carries the glass fiber composite material blank. The internal cavity of the mold 2 is adapted to the structure of the target product. The mold 2 consists of a male mold and a female mold. The heating plate heats the blank inside, and the pressure is provided by the oil cylinder 4 to achieve the hot pressing function.

[0016] Please see Figure 1 A vacuum hood 3 is installed above the mold 2. The vacuum hood 3 can be raised and lowered above the mold 2 and its opening and closing are controlled by a lifting mechanism. The vacuum hood 3 can cover the mold 2 and extract the air inside the mold cavity. Hot pressing in a vacuum environment can reduce the gas source, ensure the working environment for material molding, and help reduce air bubbles. The exhaust control equipment for hot pressing of fiber composite materials can adapt to high-precision glass fiber composite products of different sizes and structures by preset different process parameters through the control system. It can also be flexibly adjusted according to the material characteristics such as the basis weight of glass fiber cloth and the content of semi-cured film adhesive. It has strong versatility and can adapt to different production needs. The whole process is automatically controlled and the parameters can be precisely adjusted to avoid human operation errors and ensure product quality consistency.

[0017] A method for controlling exhaust gas in hot pressing of fiber composite materials, using the aforementioned exhaust gas control equipment for hot pressing of fiber composite materials, includes the following steps: S1. Blank preparation and positioning: Place the laminated fiberglass cloth and epoxy resin semi-cured sheet into mold 2 to ensure that the blank is laid flat. Then move mold 2 to the preset position of the lower heating plate 1. S2. Vacuum Cover and Vacuuming: The vacuum cover 3 descends and precisely covers the mold 2. The vacuum system is activated to vacuum the cavity of the mold 2, so that the vacuum degree inside the cavity reaches the preset vacuum degree threshold. S3, Initial Pressing: The hydraulic cylinder 4 drives the top plate 5 to move downward, causing the mold 2 to close until the pressure on the mold 2 reaches the preset pressure value or the top plate 5 moves to the preset pressing position, after which the hydraulic cylinder stops pressurizing; S4, Lifting and Pausing: The hydraulic cylinder 4 drives the top plate 5 to move in the opposite direction, causing the mold 2 to open slightly and pause for 1-2 seconds, so that the residual air and excess epoxy resin in the cavity of the mold 2 can be released. S5. Secondary pressure: The hydraulic cylinder 4 drives the top plate 5 to move downward again, causing the mold 2 to close again until the preset pressure value or preset pressure position is reached, completing a complete venting action. S6. Circulating exhaust: Repeat the exhaust action of steps 3-5 until the preset number of exhausts is completed. The number of exhausts is set according to the actual situation of the product. Generally, the larger the product volume, the more exhausts are required. S7. Pressure Holding and Curing: After the venting is completed, the oil cylinder 4 is kept under pressure for pressure holding and curing. The pressure holding time is 100-300 seconds. During the pressure holding process, the preset pressure value and molding temperature are maintained to ensure that the epoxy resin is fully cured. The pressure holding and curing is a three-stage process. The pressure holding and curing time is adjusted according to the product process requirements to maintain the specified pressure and achieve three-stage pressure holding. S8. Stepped cooling and demolding: After pressure holding and curing, the product is cooled down according to the preset stepped cooling process, so that the product gradually cools down according to the preset stepped temperature. After cooling to the preset temperature of 40℃-45℃, the product is demolded to obtain a high-precision glass fiber composite material product.

[0018] By implementing a cyclic venting process and setting the venting frequency according to actual production needs, production quality can be improved while ensuring production efficiency. It effectively removes residual air from the mold cavity, including air between multiple layers of material, greatly promoting uniform flow of epoxy resin. The defect rate of bubble marks is reduced from 10% to below 1%, the defect rate of incomplete or missing resin structures is reduced from 7% to below 1%, and the defect rate of structural marks is reduced from 5% to below 1%. Furthermore, the overall product yield is increased from 81% in traditional processes to 96%-97%, reducing raw material waste and rework costs, and improving the economics of mass production. Moreover, this venting control method for hot pressing of fiber composite materials can be achieved by optimizing the action logic and control parameters of existing hot pressing equipment, resulting in low modification costs, easy industrial application, and good practicality.

[0019] In addition, the present invention provides the following two embodiments.

[0020] Example 1: Hot pressing molding of 5G mobile phone back cover Product parameters and product name: 5G mobile phone back cover; size: 15mm×8mm×5mm; structural requirements: at least 6 small structures on the back are fully formed, and there are no bubble marks or structural marks on the surface.

[0021] Preliminary preparation: 12K fiberglass cloth with a weight of 200g / m² is selected. 2The epoxy resin semi-cured sheet contains 35% adhesive; it is laminated in three layers in the order of fiberglass cloth-semi-cured sheet-fiberglass cloth-semi-cured sheet-fiberglass cloth and then laid in the mold cavity.

[0022] Process parameter settings: Preheating: 120℃×100s→140℃×100s, step-by-step temperature increase to ensure uniform preheating of the billet; Vacuum hot pressing: preset vacuum degree 100Pa, preset pressure 80MPa, molding temperature 170℃, holding time 100s, venting times 2 times; Pressure holding and curing: 170℃×100s→170℃×100s→170℃×100s, three-stage pressure holding, all maintaining a pressure of 80MPa; Cooling: 170℃×100s→130℃×100s→100℃×100s→40℃×100s (Step cooling to avoid product deformation).

[0023] Processing results: Production time is the same as traditional processes, and the overall product yield has increased from 81% to 97%. Among them, the defect rate of bubble printing has been reduced from 10% to 1%, the defect rate of incomplete glue structure has been reduced from 7% to 1%, and the defect rate of structural printing has been reduced from 5% to 1%, which fully meets the requirements of end customers for product precision and appearance.

[0024] Example 2: Thermoforming of a Laptop Casing Product parameters and product name: Laptop casing; Dimensions: 350mm×250mm×3mm; Structural requirements: No obvious structural marks on the surface, no missing glue on the edges, and overall flatness error ≤0.1mm.

[0025] Preliminary preparation: 12K fiberglass cloth with a weight of 220g / m² is selected. 2 The epoxy resin semi-cured sheet contains 38% adhesive; four layers are stacked in the order of fiberglass cloth-semi-cured sheet-fiberglass cloth-semi-cured sheet-fiberglass cloth-semi-cured sheet-fiberglass cloth, and then laid in the mold cavity.

[0026] Process parameter settings: Preheating: 130℃×120s→150℃×120s (Extended preheating time, suitable for large-size billets); Vacuum hot pressing: preset vacuum degree 80Pa, preset pressure 90MPa, molding temperature 175℃, holding time 120s, 3 times of venting (increase the number of venting times to ensure sufficient venting of large-size cavities). Pressure holding and curing: 175℃×100s→175℃×100s→175℃×100s (three-stage pressure holding, all maintaining a pressure of 90MPa); Cooling: 175℃×120s→140℃×120s→110℃×120s→45℃×120s (Extend the cooling time of each stage to ensure uniform cooling of large-sized products).

[0027] Processing results: The production time is basically the same as that of traditional processes, and the overall product yield has increased from 78% to 96%. Among them, the defect rate of bubble printing is ≤1.2%, the defect rate of incomplete glue structure is ≤1%, the defect rate of structural printing is ≤0.8%, and the product flatness error is ≤0.1mm, which meets the high precision requirements of laptop shells.

[0028] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0029] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An exhaust control device for a fiber composite hot press molding, comprising a base plate (7), characterized by: The bottom plate (7) is provided with a support, the top of the support is provided with an oil cylinder (4), the output end of the oil cylinder (4) is fixedly connected with a top plate (5), the bottom of the top plate (5) is provided with an upper heating plate (6), a lower heating plate (1) is arranged in the support and is arranged on the bottom plate (7), the upper side of the lower heating plate (1) is provided with a mold (2), the oil cylinder (4) drives the mold (2) to complete the actions of closing and opening the mold, and the upper side of the mold (2) is provided with a vacuum cover (3).

2. The exhaust control device for fiber composite hot press forming according to claim 1, characterized in that: The mold (2) is located below the top plate (5), and the mold (2) bears a glass fiber composite material blank, and the internal cavity of the mold (2) is adapted to the structure of the target product.

3. The vent control apparatus for a fiber composite thermoformed article of claim 2, wherein: The vacuum cover (3) is arranged above the mold (2) in a lifting manner, is controlled to open and close through a lifting mechanism, and can cover the mold (2) and extract the air in the cavity of the mold (2).

4. A method of controlling exhaust gas in hot press molding of a fiber composite material, using the exhaust gas control apparatus for hot press molding of a fiber composite material according to any one of claims 1 to 3, characterized by, The method comprises the following steps: S1, blank preparation and positioning: the laminated glass fiber cloth and epoxy resin prepreg are placed in the mold (2), and the blank is ensured to be flatly laid, and then the mold (2) is moved to a preset station of the lower heating plate (1); S2, vacuum cover closing and vacuumizing: the vacuum cover (3) is lowered and accurately covers the mold (2), and a vacuum system is started to perform vacuumizing treatment on the cavity of the mold (2), so that the vacuum degree in the cavity reaches a preset vacuum degree threshold; S3, first pressing: the oil cylinder (4) drives the top plate (5) to move downward, and drives the mold (2) to close, until the pressure borne by the mold (2) reaches a preset pressure value or the top plate (5) moves to a preset pressing position, and then the oil cylinder stops pressing; S4, lifting and stopping: the oil cylinder (4) drives the top plate (5) to move reversely, drives the mold (2) to slightly open, stops for 1-2 seconds, so that the residual air and excess epoxy resin glue in the cavity of the mold (2) can be released; S5, second pressing: the oil cylinder (4) drives the top plate (5) to move downward again, drives the mold (2) to close again, until a preset pressure value or a preset pressing position is reached, and a complete exhaust action is completed; S6, circulating exhaust: the exhaust actions of steps 3-5 are repeated until a preset exhaust number is reached; S7, pressure maintaining and curing: after the exhaust is completed, the oil cylinder (4) maintains the pressing state to perform pressure maintaining and curing, the pressure maintaining time is 100-300 seconds, the preset pressure value and the molding temperature are maintained during the pressure maintaining process, so that the epoxy resin is fully cured; S8, step cooling and demolding: after the pressure maintaining and curing are completed, the temperature is lowered according to a preset step cooling process, the demolding is performed after the temperature is lowered to a preset temperature of 40-45℃, and a high-precision glass fiber composite material product is obtained.

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