Composite material forming equipment and method for stable-pressure resin injection and product

Abstract

The invention discloses a composite material forming device and method for stable-pressure resin injection and a product, the composite material forming device for stable-pressure resin injection comprises a press system, a resin injection system and a mold, and further comprises a mold cavity pressure dynamic adjusting system; the die cavity pressure dynamic adjusting system comprises a controller, a die cavity pressure sensor and a die position sensing device; the die cavity pressure sensor is used for monitoring the pressure in the die cavity in real time and feeding back a pressure value; the mold position sensing device is used for monitoring the height of a mold cavity of the mold in real time and feeding back a height value; the controller is used for receiving the pressure value and the height value; the controller is further in communication connection with the press system and controls the press system, when the pressure of the die cavity is larger than the preset standard pressure, a control instruction is output to the press system, the press system dynamically adjusts the position of the upper die and / or the lower die so as to adjust the height of the die cavity in real time, and therefore the pressure in the die cavity is stabilized within the preset target pressure range.

Description

Technical Field

[0001] This invention belongs to the field of fiber-reinforced composite material molding technology, specifically relating to a composite material molding equipment, method, and product that uses a dynamic mold cavity pressure adjustment system to adjust the mold cavity height in real time to achieve stable pressure injection of resin. Background Technology

[0002] Currently, there are two main methods for resin injection molding in composite liquid molding technology (VARI, RTM, HP-RTM): one is constant resin injection pressure, where the pressure of the resin injected into the mold cavity remains constant throughout the injection process. This method does not consider the influence of the product's shape and fabric preform after the mold closes. To maintain a consistent injection pressure, the resin injection flow rate gradually decreases, resulting in problems such as long injection time or insufficient resin filling. The other method is constant resin injection flow rate, where the flow rate of the resin injected into the mold cavity remains constant throughout the injection process. Similarly, this method does not consider the influence of the product's shape and fabric preform after the mold closes. To maintain a consistent injection flow rate, the resin injection pressure gradually increases, causing fiber erosion and resulting in texture disorder and other appearance defects.

[0003] The defects and shortcomings of existing technologies are specifically manifested as follows: 1. Insufficient monitoring of in-mold pressure during injection: Regardless of whether resin pressure stabilization injection or constant flow injection is used, it is impossible to monitor the entire resin injection process in real time, let alone avoid the effects of similar defects.

[0004] 2. Mold cannot be adjusted in real time: In the existing technology, the thickness of the mold cavity is fixed after the mold is closed and clamping force is applied, and it is impossible to make real-time adjustments according to the changes in injection pressure and pressure inside the mold cavity during the injection process.

[0005] This can lead to a high pressure fluctuation rate, which may adversely affect the resin flow, fiber wetting, mechanical properties and appearance quality of the product.

[0006] Chinese patent application CN202210070817.0 discloses a method for manufacturing resin molded articles that can reduce molding defects even when resin molding is performed while the chip is temporarily fixed to a carrier by a temporary fixing piece. The method for manufacturing resin molded articles of the present invention is a method for manufacturing resin molded articles by transfer molding of a molding object in which a chip (21) is temporarily fixed to a carrier (11) by a temporary fixing piece (12). The method includes a resin molding step in which the molding object is resin molded by transfer molding using a molding mold (1000). The resin molding step is performed in a state in which the temporary fixing piece (12) disposed in the molding mold (1000) and the opposing surface of the temporary fixing piece (12) on the side where the chip (21) is temporarily fixed are not in contact, and a gap (G) is formed. Summary of the Invention

[0007] To overcome the shortcomings of existing technologies, this invention provides a method that allows for real-time monitoring of in-mold pressure throughout the resin injection process and controls the mold cavity pressure below a preset standard value, thus avoiding the problem of disordered fiber texture. The specific technical solution of this invention is as follows: A composite material molding equipment for pressure-stabilized injection resin includes a press system, a resin injection system, a mold, and a mold cavity pressure dynamic adjustment system. The mold cavity pressure dynamic adjustment system includes a controller, a mold cavity pressure sensor, and a mold position sensor. The mold cavity pressure sensor is installed inside the mold cavity to monitor the pressure within the cavity in real time and provide feedback on the pressure value. The mold position sensor monitors the mold cavity height in real time and provides feedback on the height value. The controller is communicatively connected to the mold cavity pressure sensor and the mold position sensor to receive the pressure and height values. The controller is also communicatively connected to and controls the press system. When the mold cavity pressure exceeds a preset standard pressure, the controller outputs a control command to the press system, which dynamically adjusts the position of the upper mold and / or lower mold to adjust the mold cavity height in real time, thereby stabilizing the pressure within the mold cavity within the preset target pressure range. The preset target pressure range is a pressure range less than or equal to a preset standard value.

[0008] Preferably, the controller is a PID control system.

[0009] The resin injection system injects resin into the mold cavity according to a set resin injection flow rate. It includes a storage tank, a circulation pipeline, a high-pressure regulating valve, a metering pump, an injection control system, and a high-pressure injection nozzle. The high-pressure injection nozzle is connected to the mold, and the circulation pipeline connects the storage tank and the high-pressure injection nozzle. A high-pressure regulating valve is installed on the circulation pipeline to control the resin injection pressure. The resin injection system is connected to a press system.

[0010] The press system includes a locking module, a mold-locking column, a vacuum system, a hydraulic system, and a mold temperature control device. The locking module includes an upper locking module and a lower locking module. The upper locking module is used to lock the upper mold, and the lower locking module is used to lock the lower mold. The vacuum system is used to evacuate the mold cavity. The hydraulic system controls the up and down movement of the upper and / or lower locking modules on the mold-locking column.

[0011] The composite material is a compound of resin and carbon fiber, wherein the resin is a thermosetting resin, and more specifically, the thermosetting resin is an epoxy resin or a polyurethane resin.

[0012] The mold cavity pressure sensor, which uses a pressure sensor to monitor the internal pressure of the mold cavity in real time and feeds the pressure data back to the control system, is a mature technology in this field.

[0013] Preferably, the cavity pressure sensor is a Kistler-601C series, which features high sensitivity, small sensor size, short rise time, high natural frequency, and a very wide operating temperature range.

[0014] Furthermore, the mold's mating surface is provided with a sealing structure; the sealing structure includes a sealing groove and a sealing ring disposed within the sealing groove; the cross-sectional height of the sealing ring is greater than the depth of the sealing groove, and the cross-section of the sealing ring is provided with at least one hollow hole, which can ensure the compression amount while also changing with the mold cavity height and maintaining a vacuum seal between the upper and lower molds.

[0015] The mold position sensing device is installed on the mold locking column of the press system, preferably at one end of the moving mold. That is, when the lower mold is fixed and the upper mold is a movable mold, the mold position sensing device is installed above the upper mold; when the upper mold is fixed and the lower mold is a movable mold, the mold position sensing device is installed below the lower mold. The mold position sensing device can sense the distance to the moving mold and feed the distance back to the PID control system. It monitors the real-time position of the mold through devices such as displacement sensors and converts the position data into a mold cavity height value and feeds it back to the control system. This is a well-known technology in the field.

[0016] The cavity pressure sensor is installed inside the mold cavity, in an area 10cm to 15cm away from the resin injection port.

[0017] The mold has a sealing structure on its mating surface; the sealing structure includes a sealing groove and a sealing ring disposed in the sealing groove; the height of the sealing ring is greater than the depth of the sealing groove, and the cross-section of the sealing ring has at least one hollow hole.

[0018] The sealing ring has a cross-sectional height of 2.3 mm and the sealing groove has a depth of 2.0 mm.

[0019] A method for molding composite materials using pressure-stabilized injection resin, employing the aforementioned pressure-stabilized injection resin composite material molding equipment, the method comprising the following steps: S1: Parameter setting steps: Set the preset standard value of the cavity pressure and the maximum allowable adjustment value of the cavity height in the controller; S2: Injection and Dynamic Pressure Adjustment Steps: The fiber reinforcement is laid in the mold, the mold is closed to the theoretical cavity height and a vacuum is drawn; the resin injection system is turned on to inject resin into the mold cavity; during the injection process, the mold cavity pressure is monitored in real time by the mold cavity pressure dynamic adjustment system. When the mold cavity pressure is greater than the preset standard value, the controller controls the press system to raise the upper mold and / or lower the lower mold to increase the mold cavity height, thereby reducing the mold cavity pressure to below the preset target value; the dynamic pressure adjustment process is iteratively adjusted in steps with a preset minimum adjustment accuracy; S3: Pressure holding and curing step: After the resin injection is completed, control the press system to drive the mold to close to the initial position or the specified pressure and hold the pressure until the resin is cured; S4: Open the mold and remove the parts.

[0020] In step S2, the minimum adjustment accuracy is 0.05 mm.

[0021] In step S2, during the dynamic pressure adjustment process, when the pressure inside the mold cavity is equal to or less than the preset standard value, the height adjustment is stopped, and the injection continues while maintaining the current height value.

[0022] A composite material part, prepared using the aforementioned equipment or according to the aforementioned method, wherein the surface resin texture of the part is uniform, continuous and orderly.

[0023] The technical principle of this invention is as follows: based on Darcy's law and the permeability formula... K is the permeability coefficient, representing the ability of the resin matrix to pass through the fiber reinforcement under constant pressure. It is a constant value under constant pressure, and the unit is m. 2 Q represents the resin flow rate, in meters per second (m³). 3 / s; η is the resin viscosity, in Pa•s; L is the length of the straight-line flow path of the resin from the injection port to the pressure sensor, in meters; ΔP is the pressure difference between the resin injection pressure and the pressure inside the mold cavity, in Pa; A is the cross-sectional area of ​​the mold cavity perpendicular to the flow direction, i.e., the longitudinal cross-sectional area at the pressure sensor inside the mold cavity, in m². 2 .

[0024] The cross-sectional area of ​​the mold cavity perpendicular to the flow direction is A = W × T, where T is the height of the mold cavity at the pressure sensor (in meters), and W is the flow width, i.e., the width of the mold cavity perpendicular to the flow direction (in meters).

[0025] Therefore, we can obtain: , then .

[0026] In constant resin injection flow molding technology, during product injection, the resin flow rate Q, resin viscosity η, flow path L, and cavity width W perpendicular to the flow direction are all constant values. ΔP is the pressure difference between the resin injection pressure and the cavity pressure (resin injection pressure - cavity pressure). During production, as the injection progresses, the cavity pressure gradually increases, and the resin injection pressure - cavity pressure difference ΔP decreases, leading to an increase in the permeability coefficient, causing fiber erosion and texture disorder. Therefore, to maintain a stable permeability coefficient, the cavity height can be increased while ΔP decreases to maintain relative stability. Based on this, this application, during the preparation of composite materials, sets a preset standard value for the cavity pressure in the controller. When the cavity pressure exceeds the preset standard pressure (i.e., when the permeability coefficient is too high), the cavity height is increased for adaptive adjustment. When T performs iterative adjustment in step units, the height adjustment stops when the cavity pressure value is less than or equal to the preset standard pressure value.

[0027] This invention can effectively solve the problem of unstable permeability caused by resin injection and flow by controlling the mold cavity height through a pressure stabilization control system, thereby achieving the following: 1. Stable internal pressure in the mold cavity: By real-time detection of the internal pressure in the mold cavity, the mold cavity height can be adjusted in real time, and the pressure fluctuation rate in the mold cavity can be controlled within ±3%.

[0028] 2. Prevent fiber scattering: Avoid fiber displacement or damage caused by sudden pressure changes. The performance of fibers that are displaced or damaged decreases by about 10-15%.

[0029] 3. Wide system adaptability: Applicable to various fabric preforms such as carbon fiber, glass fiber or other high-performance fibers. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the device in Embodiment 1 of the present invention; Figure 2 A photograph of the composite material obtained in Example 2 of this invention; Figure 3 A photograph of the composite material obtained in Example 3 of this invention; Figure 4 A photograph of the composite material obtained in Comparative Example 1; Figure 5Photograph of the composite material obtained in Comparative Example 2.

[0031] Among them, 1-press system; 2-vacuum system; 3-upper mold; 4-lower mold; 5-resin injection system; 6-controller; 7-hydraulic system. Detailed Implementation

[0032] The following are some of the embodiments listed in this invention.

[0033] Example 1

[0034] like Figure 1 As shown, a composite material molding equipment for pressure-stabilized injection resin includes a press system 1, a resin injection system 5, and a mold. The mold has an upper mold 3 and a lower mold 4. The equipment also includes a mold cavity pressure dynamic adjustment system. The mold cavity pressure dynamic adjustment system includes a controller 6, a mold cavity pressure sensor, and a mold position sensor. The mold cavity pressure sensor is installed inside the mold cavity to monitor the pressure inside the mold cavity in real time and provide feedback on the pressure value. The mold position sensor is used to monitor the mold cavity height in real time and provide feedback on the height value. The controller 6 is communicatively connected to the mold cavity pressure sensor and the mold position sensor to receive the pressure value and the height value. The controller 6 is also communicatively connected to and controls the press system 1. Based on the pressure value, when the mold cavity pressure is greater than a preset standard pressure, the controller 6 outputs a control command to the press system 1. The press system 1 dynamically adjusts the position of the upper mold and / or the lower mold to adjust the mold cavity height in real time, thereby stabilizing the pressure inside the mold cavity within the preset target pressure range, and thus maintaining the resin permeability coefficient within a stable numerical range.

[0035] The resin injection system 5 includes a storage tank, a circulation pipeline, a high-pressure regulating valve, a metering pump, an injection control system, and a high-pressure injection nozzle; the high-pressure injection nozzle is connected to the mold, and the circulation pipeline connects the storage tank and the high-pressure injection nozzle; a high-pressure regulating valve is installed on the circulation pipeline to control the resin injection pressure.

[0036] The press system 1 includes a locking module, a mold locking column, a vacuum system 2, a hydraulic system 7, and a mold temperature device. The locking module includes an upper locking module and a lower locking module. The upper locking module is used to lock the upper mold, and the lower locking module is used to lock the lower mold. The vacuum system is used to evacuate the mold cavity. The hydraulic system 7 controls the up and down movement of the upper and / or lower locking modules on the mold locking column.

[0037] The resin injection system is connected to the press system and injects resin into the mold cavity according to the set resin injection flow rate. The high-pressure regulating valve on the resin injection system pipeline is used to set the resin injection pressure.

[0038] The cavity pressure sensor is a Kistler-601C series. This series of miniature pressure sensors features high sensitivity, small sensor size, short rise time, high natural frequency, and a very wide operating temperature range.

[0039] The mold has a sealing structure on its mating surface; the sealing structure includes a sealing groove and a sealing ring disposed in the sealing groove; the cross-sectional height of the sealing ring is greater than the depth of the sealing groove, and the cross-section of the sealing ring has at least one hollow hole, which can ensure the compression amount while changing with the mold cavity height and maintaining a vacuum seal between the upper and lower molds.

[0040] Example 2

[0041] This embodiment uses the preparation of a rectangular plate of uniform thickness as an example. The plate is 50cm long, 30cm wide, and 2mm thick; the height of the sealing ring on the mold is 2.3mm, and the depth of the sealing groove on the mold for installing the sealing ring is 2mm. Because there is a small hole in the middle of the sealing ring, its height can be varied within the range of 2-2.3mm; the resin matrix used is an epoxy resin matrix. Using the equipment described in Example 1, the composite resin is processed according to the following steps: Step 1. Initial parameter settings: Taking the fabrication of a 2mm thick plate as an example, epoxy resin is selected with a viscosity of 0.12 Pa·s. The resin flow rate in the resin injection system is set to 30 cm³. 3 / s; The initial parameters are set in the PID control system of the pressure stabilization system. The resin injection pressure is 14MPa, the molding clamping pressure is 500t, and the constant (preset standard) pressure in the mold cavity is 6MPa. That is, if the actual value of the mold cavity pressure is less than or equal to 6MPa, it is within the preset target pressure range, and the dynamic adjustment system of the mold cavity pressure will not intervene. If the actual value of the mold cavity pressure is greater than 6MPa, the dynamic adjustment system of the mold cavity pressure will start to work. The PID control system controls the press system in real time to adjust the mold cavity height. The minimum height adjustment accuracy of the press system is 0.05mm. Step 2. Vacuuming after mold insertion: Place the pre-formed fabric into the mold and close the mold to the theoretical height of the mold cavity, then vacuum the cavity. The theoretical height is 2mm. Step 3. Resin Injection Molding Process: The resin injection system is activated, injecting resin into the mold. Simultaneously, based on real-time pressure feedback from the pressure sensor within the mold, the PID control system continuously monitors the pressure within the mold cavity and dynamically adjusts the cavity height to ensure a constant pressure (preset standard value is 6 MPa). The PID control system feeds back to the press control system to adjust the cavity height in real time. Specifically, when the pressure sensor reading exceeds 6 MPa, the PID control system feeds back to the press system to raise the mold by 0.05 mm; this increases the cavity height by 0.05 mm. This causes the cavity pressure to decrease due to the increased cavity height. When the pressure sensor reading drops below 6 MPa, the dynamic pressure adjustment system discontinues operation. As resin injection continues, if the pressure sensor reading exceeds 6 MPa, the PID control system feeds back to the press system to raise the mold another 0.05 mm; this increases the cavity height by another 0.05 mm. This causes the pressure inside the mold cavity to decrease as the mold cavity height increases; when the pressure sensor value drops below 6MPa, the dynamic mold cavity pressure adjustment system stops working. This cycle of adjusting the mold cavity height achieves stable injection pressure. Finally, when the mold cavity height automatically adjusts to the upper limit parameter (2.2mm), the system will automatically stop adjusting the mold cavity height and maintain the current value. Step 4. Pressure holding and molding: When the resin injection is finished, the PID control system is used to make the mold completely close to the theoretical height of the mold cavity (2mm) and hold the pressure for molding. Step 5. Demolding and Part Removal: After holding the pressure for a certain period of time, remove the parts. The resulting resin product is as follows: Figure 2 As shown, Figure 2 It can be seen that the composite resin prepared by the method of the present invention has a neat and orderly fiber texture, and the pressure fluctuation rate during the entire manufacturing process is reduced from ±15% to ±3%, which greatly improves the disordered fiber texture and insufficient resin filling of flat products.

[0042] Example 3

[0043] Compared to Example 2, this example uses a Z-shaped beam product of uniform thickness. The Z-shaped beam is 78cm long, 22cm wide, and 3mm thick; the height of the sealing ring on the mold is 2.3mm, and the depth of the sealing groove on the mold where the sealing ring is installed is 2mm. Because there is a small hole in the middle of the sealing ring, it can be varied within the range of 2-2.3mm; the flow path length of the injection system is 12cm, and the flow width is 70cm. Compared to Example 2, the initial parameters are set as follows: resin viscosity is 0.1Pa·s, and resin flow rate in the resin injection system is set to 30 cm³. 3 / s; The initial parameters are set in the PID control system of the pressure stabilizing system: resin injection pressure is 15MPa, molding clamping pressure is 800t, and the preset standard value of the pressure sensor in the mold cavity is 6MPa; the remaining steps and processes are the same as in Example 2. The obtained resin product is as follows: Figure 3 As shown, Figure 3 It can be seen that the composite resin prepared by the method of the present invention has a neat and orderly fiber texture, and the pressure fluctuation rate during the entire manufacturing process is reduced from ±15% to ±3%, which greatly improves the disordered fiber texture and insufficient resin filling of the Z-beam product.

[0044] Comparative Example 1 This comparative example serves as a comparison example for Example 2, employing a conventional injection molding method, i.e., a constant resin injection flow rate but without pressure stabilization. The resulting composite resin is as follows: Figure 4 As shown, by Figure 4 It is known that composite resins prepared by conventional methods have defects such as resin deficiency, fiber texture being broken down, and disordered fiber texture.

[0045] Comparative Example 2 This comparative example serves as a comparison of Example 3, employing a conventional injection molding method, i.e., a constant resin injection flow rate but without pressure stabilization. The resulting composite resin is as follows: Figure 5 As shown, by Figure 5 It is known that composite resins prepared by conventional methods have defects such as resin deficiency, fiber texture being broken down, and disordered fiber texture.

Claims

1. A composite material molding equipment for pressure-stabilized injection resin, comprising a press system, a resin injection system, and a mold, characterized in that, It also includes a dynamic cavity pressure adjustment system; the dynamic cavity pressure adjustment system includes a controller, a cavity pressure sensor, and a mold position sensor; the cavity pressure sensor is installed inside the mold cavity to monitor the pressure inside the cavity in real time and provide feedback on the pressure value; the mold position sensor is used to monitor the cavity height of the mold in real time and provide feedback on the height value; the controller is communicatively connected to the cavity pressure sensor and the mold position sensor to receive the pressure value and the height value; the controller is also communicatively connected to and controls the press system, and when the cavity pressure is greater than the preset standard pressure, it outputs a control command to the press system, and the press system dynamically adjusts the position of the upper mold and / or the lower mold to adjust the cavity height in real time, thereby stabilizing the pressure inside the cavity within the preset target pressure range.

2. The composite material molding equipment for pressure-stabilized injection resin according to claim 1, characterized in that, The cavity pressure sensor is installed inside the mold cavity, in an area 10cm to 15cm away from the resin injection port.

3. The composite material molding equipment for pressure-stabilized injection resin according to claim 1, characterized in that, The mold has a sealing structure on its mating surface; the sealing structure includes a sealing groove and a sealing ring disposed in the sealing groove; the height of the sealing ring is greater than the depth of the sealing groove, and the cross-section of the sealing ring has at least one hollow hole.

4. The composite material molding equipment for pressure-stabilized injection resin according to claim 3, characterized in that, The sealing ring has a cross-sectional height of 2.3 mm and the sealing groove has a depth of 2.0 mm.

5. A method for molding composite materials using pressure-stabilized injection resin, characterized in that, The composite material molding equipment using the pressure-stabilized injection resin according to any one of claims 1 to 4 is used, and the method includes the following steps: S1: Parameter setting steps: Set the preset standard value of the cavity pressure and the maximum allowable adjustment value of the cavity height in the controller; S2: Injection and Dynamic Pressure Adjustment Steps: The fiber reinforcement is laid in the mold, the mold is closed to the theoretical cavity height and a vacuum is drawn; the resin injection system is turned on to inject resin into the mold cavity; during the injection process, the mold cavity pressure is monitored in real time by the mold cavity pressure dynamic adjustment system. When the mold cavity pressure is greater than the preset standard value, the controller controls the press system to raise the upper mold and / or lower the lower mold to increase the mold cavity height, thereby reducing the mold cavity pressure to below the preset target value; the dynamic pressure adjustment process is iteratively adjusted in steps with a preset minimum adjustment accuracy; S3: Pressure holding and curing step: After the resin injection is completed, the controller controls the press system to drive the mold to close to the theoretical mold cavity height or the specified pressure and hold the pressure until the resin is cured; S4: Mold opening and part removal.

6. The composite material molding method of the pressure-stabilized injection resin according to claim 5, characterized in that, In step S2, the minimum adjustment accuracy is 0.05 mm.

7. The composite material molding method of the pressure-stabilized injection resin according to claim 5, characterized in that, In step S2, during the dynamic pressure adjustment process, when the pressure inside the mold cavity is equal to or less than the preset standard value, the height adjustment is stopped, and the injection continues while maintaining the current height value.

8. A composite material part, characterized in that, The part is prepared by any of the devices described in claims 1 to 4 or by any of the methods described in claims 5 to 7, and the surface resin texture of the part is uniform, continuous and orderly.

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