Multi-layer mould pressing device for heating and melting fiber reinforced thermoplastic composite material

Abstract

The invention relates to the technical field of composite materials, in particular to a fiber reinforced thermoplastic composite material heating and melting multilayer mold pressing device which comprises an upper mold and a lower mold. A plurality of ejection assemblies used for ejecting the formed model away from the lower mold are arranged in the lower mold, distance sensors are arranged on the ejection assemblies, and spraying assemblies are symmetrically arranged on the two sides in the lower mold; each ejection assembly comprises a hydraulic cylinder and an ejection rod, the bottom end of each ejection rod is fixedly connected to the output end of the corresponding hydraulic cylinder, each ejection rod is axially provided with a plurality of spraying holes, the diameters of the spraying holes are sequentially increased from top to bottom, and the lower portion of each ejection rod is provided with an input hole communicated with the spraying assembly; and the top walls of the ejector rods are pneumatic diaphragms. The pneumatic diaphragm is driven to vibrate to generate a synergistic demolding mechanism while micro demolding force is provided through air pressure, and low-damage demolding of a product with a complex structure is achieved.

Description

Technical Field

[0001] This invention relates to the field of composite materials technology, and more specifically to a multilayer molding device for heating and melting fiber-reinforced thermoplastic composite materials. Background Technology

[0002] Heated melting and multi-layer molding of thermoplastic composites is an advanced composite material molding technology. This process typically involves stacking multiple layers of prepreg or preforms within a mold, then externally heating to melt and plasticize the thermoplastic resin matrix, followed by cooling and solidification under pressure to obtain a part with a specific shape and properties. This process integrates material compounding and product molding, and is particularly suitable for preparing structural components with complex geometries, high specific strength, and recyclability, showing broad application prospects in aerospace, automotive lightweighting, and other fields.

[0003] However, this process faces significant challenges in the demolding stage. Because thermoplastic composites have high viscosity in their molten state at high temperatures, they exhibit strong adhesion to the mold surface. Simultaneously, a vacuum negative pressure zone may form during molding, resulting in enormous demolding resistance. Traditional demolding methods primarily rely on mechanical ejector pins or single pneumatic assistance, which have obvious drawbacks: the demolding force provided by mechanical ejector pins is too concentrated, easily leaving ejector marks on the product surface, affecting appearance and surface quality; for thin-walled products or products with complex structures such as deep cavities or undercuts, this uneven ejection force can even cause irreversible deformation, tearing, or internal damage at the moment of demolding, severely restricting product quality and production yield. Therefore, there is an urgent need to develop a novel molding device that can provide uniform, controllable, and low-damage demolding force. Summary of the Invention

[0004] To address the aforementioned issues, this invention discloses a multi-layer molding device for heating and melting fiber-reinforced thermoplastic composite materials. By providing micro-demolding force through air pressure, it drives a pneumatic diaphragm to vibrate and generate a synergistic demolding mechanism, thereby achieving low-damage demolding of complex structural products.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: a multi-layer molding device for heating and melting fiber-reinforced thermoplastic composite materials, comprising an upper mold and a lower mold; the lower mold is provided with a plurality of ejection components for ejecting the molded model away from the lower mold, each ejection component being provided with a distance sensor, and spraying components for ejecting high-pressure gas to separate the model are symmetrically provided on both sides of the lower mold.

[0006] Each ejector assembly includes a hydraulic cylinder and an ejector rod. The bottom end of the ejector rod is fixedly connected to the output end of the hydraulic cylinder. Several spray holes are axially opened on the ejector rod, and the diameter of the spray holes increases from top to bottom. An input hole communicating with the injection assembly is opened at the bottom of the ejector rod. The top wall of the ejector rod is a pneumatic diaphragm.

[0007] The technical principles of the above solution are as follows:

[0008] At the start of the demolding process, each ejector component provides real-time feedback on its ejection displacement via a distance sensor. The control system pre-sets the ejection sequence and pressure for each area based on the product shape, such as ejecting deep cavity areas first and then ejecting chamfered areas in stages. For example, for products with a stepped structure, the control system can instruct the bottom ejector to eject a certain distance first. After the upper structure loosens, the ejector pins in other areas can then be coordinated to move synchronously, avoiding product cracking caused by uneven ejection. The control system instructs the injection components to operate, and high-pressure gas enters the internal cavity of the ejector through the input hole at the bottom of the ejector and is finally ejected from the axially distributed nozzles. The high-pressure gas forms a gas film between the mold cavity and the product, which can effectively neutralize some of the vacuum adsorption force and surface adhesion force, providing an initial, uniform separation force for the product, thereby loosening it. When the control system introduces high-frequency pulsed air pressure into the ejector, the pneumatic diaphragm generates high-frequency vibration, which can directly act on the surface of the product, breaking the adhesion between the material and the mold.

[0009] Distance sensors monitor the ejection displacement of each ejector pin in real time and feed the data back to the control system. The system dynamically adjusts the thrust of the hydraulic cylinder and the gas pressure of the injection assembly according to the preset demolding curve. For example, when the ejection resistance in a certain area increases abnormally, the control system can increase the gas pressure or vibration frequency in that area, while slowing down the ejection speed to avoid damage to the product caused by forced ejection.

[0010] The above approach has the following beneficial effects:

[0011] 1. The control system of this invention can preset the action sequence and pressure gradient of the ejection components in each region according to the product structure. For example, when the sheet structure is adapted to a deep cavity, the ejector rods in the deep cavity region are ejected first, and the bottom of the stepped structure moves first to loosen the upper structure. By ejecting in stages, the force on each part is balanced, avoiding stress concentration and cracking caused by uneven ejection. It is especially suitable for demolding products with complex geometric shapes.

[0012] 2. In this invention, high-pressure gas is sprayed through axial nozzles on the ejector rod, with the nozzle diameter increasing from top to bottom. This optimizes gas diffusion efficiency and forms a uniform gas film between the mold and the product, neutralizing the vacuum adsorption force and surface adhesion force, and providing initial separation force. At the same time, the pneumatic diaphragm at the top of the ejector rod vibrates under high-frequency pulsed air pressure, directly acting on the surface of the product, further disrupting the interfacial adhesion between the material and the mold. The combination of these two factors can significantly reduce demolding resistance, protect the surface finish of the product, and reduce scratches or deformation caused by mechanical ejection.

[0013] 3. This invention uses a distance sensor to monitor the ejection displacement in real time, forming a closed-loop control. When abnormal ejection resistance is detected in a certain area, the thrust and gas pressure of the hydraulic cylinder in that area can be dynamically adjusted to achieve adaptive processing. This allows the device to flexibly respond to different product geometries, material properties, and minor changes in the production process, improving equipment stability and process reproducibility, and reducing the scrap rate.

[0014] Furthermore, each push rod is equipped with a piezoelectric ceramic actuator.

[0015] Beneficial effects: The addition of a piezoelectric ceramic actuator inside the ejector pin and its connection to the control system allows for the generation of additional vibrations via electrical signals. This vibration, combined with the vibration of the pneumatic diaphragm, further enhances the breaking effect on the adhesion between the product and the mold. It is particularly effective in promoting separation in areas of stubborn adhesion, thereby improving the thoroughness of demolding.

[0016] Furthermore, each pneumatic diaphragm is fixedly connected to a high-temperature resistant elastic gasket.

[0017] Beneficial effects: The high-temperature resistant elastic gasket at the top of the pneumatic diaphragm can buffer the direct contact between the ejector rod and the product surface, avoiding damage or indentation to the product surface caused by rigid ejection. At the same time, it can withstand the residual high temperature during the demolding process, ensuring the structural stability and protective function of the gasket in the thermal environment.

[0018] Furthermore, each injection component includes a gas distribution chamber and a gas source symmetrically arranged in the lower mold. The output end of the gas source is connected to the input end of the gas distribution chamber. The output end of the gas distribution chamber is connected to several gas delivery pipes. The other end of each gas delivery pipe away from the gas distribution chamber is connected to the input hole.

[0019] Beneficial effects: The gas distribution chamber and gas pipeline design of the jet assembly can evenly and stably distribute the gas source to the input holes of each ejector rod, ensuring that the gas pressure and flow rate of each ejector rod are consistent, making the gas film formed between the mold and the product more uniform, and improving the overall coordination and reliability of gas-assisted demolding.

[0020] Furthermore, heating elements are provided in both the upper and lower molds.

[0021] Beneficial effects: The heating elements in the upper and lower molds are connected to the control system, which can precisely control the temperature during the molding process according to the characteristics of the composite material, ensuring that the material is molded in the optimal melting state, reducing internal defects in the product caused by uneven temperature, and improving the stability of molding quality.

[0022] Furthermore, both the upper and lower mold surfaces are coated with an anti-stick coating.

[0023] Beneficial effects: The non-stick coating on the molding surface can reduce the physical adhesion between the product and the mold surface from the source, reduce the resistance during demolding, reduce the scratching of the product surface by the mold during demolding, protect the appearance of the product, and the coating can reduce the frequency of mold cleaning and extend the service life of the mold.

[0024] Furthermore, a cooling channel is provided at the bottom of the lower mold, and the cooling channel is connected to an external cooling system.

[0025] Beneficial effects: The cooling channel at the bottom of the lower mold, in conjunction with the external cooling system, can quickly remove the residual heat from the molded product, accelerate its cooling and setting, shorten the production cycle of a single product, improve the production efficiency of the equipment, and at the same time avoid deformation of the product due to slow cooling.

[0026] Furthermore, buffer springs are provided between the pneumatic diaphragm and the elastic gasket, and the buffer springs are evenly distributed along the axial direction of the push rod.

[0027] Beneficial effects: The buffer spring between the pneumatic diaphragm and the elastic gasket can further absorb the impact force during vibration and ejection, making the force exerted by the ejector rod on the product more gentle and uniform, avoiding local damage to the product caused by excessive instantaneous force, and is especially suitable for composite material products with high brittleness.

[0028] Furthermore, the vibration frequency range of the piezoelectric ceramic actuator is 20-50kHz, and the outer periphery of the piezoelectric ceramic actuator is provided with a heat-insulating mica sheet.

[0029] Beneficial effects: The specific vibration frequency range of the piezoelectric ceramic actuator can effectively match the needs of breaking the adhesion of materials. The heat-insulating mica sheet on the outer periphery can isolate the high temperature of the mold, prevent the actuator from being affected by overheating and affecting its vibration performance or shortening its service life, and ensure its long-term stable operation.

[0030] Furthermore, the control system includes:

[0031] The acquisition module is connected to the distance sensor signal. The acquisition module is used to receive the model distance data transmitted by the distance sensor, and uses analog-to-digital conversion to generate digital distance data which is then transmitted to the processing module.

[0032] The processing module receives digital distance data, uses a preset algorithm to generate control commands, and transmits them to the control module.

[0033] The control module is used to receive control commands, generate hydraulic cylinder control signals using pulse width modulation, and transmit them to the hydraulic cylinder; it is also used to receive control commands, generate gas injection signals using switch control, and transmit them to the gas distribution chamber; and it is also used to receive control commands, generate vibration control signals using frequency modulation, and transmit them to the piezoelectric ceramic actuator.

[0034] The temperature control module is connected to the heating element via a signal. The temperature control module receives the temperature data transmitted by the heating element and generates a temperature control signal to be transmitted to the heating element using a PID control method.

[0035] Beneficial effects: By setting up a control system, rapid acquisition, accurate analysis, and independent closed-loop control of multiple parameters such as ejection displacement, gas injection, high-frequency vibration, and mold temperature are achieved. This transforms the entire demolding process from a simple mechanical action into an intelligent process that can be preset, optimized in real time, and where all actuators work closely together, ultimately significantly improving the automation level of the equipment, process repeatability, and product quality consistency. Attached Figure Description

[0036] Figure 1 This is an isometric schematic diagram of an embodiment of a fiber-reinforced thermoplastic composite heating and melting multilayer molding device according to the present invention;

[0037] Figure 2 This is a front cross-sectional view of the lower mold of an embodiment of a multilayer molding device for heating and melting fiber-reinforced thermoplastic composite materials according to the present invention;

[0038] Figure 3 This is an embodiment of a multilayer molding apparatus for heating and melting fiber-reinforced thermoplastic composite materials according to the present invention. Figure 2 Axonometric sectional view of section A in the middle;

[0039] Figure 4 This is a schematic diagram of the control system framework of an embodiment of a fiber-reinforced thermoplastic composite heating and melting multilayer molding device according to the present invention.

[0040] List of reference numerals in the attached diagram:

[0041] 1. Upper mold; 2. Molding; 3. Elastic gasket; 4. Lower mold; 5. Heating element; 6. Gas supply line; 7. Gas distribution chamber; 8. Hydraulic cylinder; 9. Pneumatic diaphragm; 10. Push rod; 11. Nozzle; 12. Input port; 13. Piezoelectric ceramic actuator; 14. Buffer spring. Detailed Implementation

[0042] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the following description refer to directions in the accompanying drawings, and the terms "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0043] As attached Figure 1-3 As shown:

[0044] This embodiment provides a multilayer molding device for heating and melting fiber-reinforced thermoplastic composite materials, including an upper mold 1 and a lower mold 4. Both the upper mold 1 and the lower mold 4 are provided with heating elements 5. The molding surfaces of both the upper mold 1 and the lower mold 4 are coated with an anti-stick coating. The bottom of the lower mold 4 is provided with a cooling channel, which is connected to an external cooling system.

[0045] The lower mold 4 is equipped with several ejection components for ejecting the molded model away from the lower mold 4. Each ejection component is equipped with a distance sensor. The lower mold 4 is symmetrically equipped with spray components for ejecting high-pressure gas to separate the model.

[0046] Each ejector assembly includes a hydraulic cylinder 8 and an ejector rod 10. The bottom end of the ejector rod 10 is fixedly connected to the output end of the hydraulic cylinder 8. Several spray holes 11 are axially opened on the ejector rod 10, and the diameter of the spray holes 11 increases from top to bottom. An input hole 12 communicating with the injection assembly is opened at the bottom of the ejector rod 10. The top wall of the ejector rod 10 is a pneumatic diaphragm 9. A high-temperature resistant elastic pad 3 is fixedly connected to the top of the pneumatic diaphragm 9. A buffer spring 14 is provided between the pneumatic diaphragm 9 and the elastic pad 3. The buffer springs 14 are evenly distributed along the axial direction of the ejector rod 10. A piezoelectric ceramic actuator 13 is also provided inside the ejector rod 10. The vibration frequency range of the piezoelectric ceramic actuator 13 is 20-50kHz, and the outer periphery of the piezoelectric ceramic actuator 13 is provided with a heat-insulating mica sheet.

[0047] Each injection assembly includes a gas distribution chamber 7 and a gas source symmetrically arranged in the lower mold 4. The output end of the gas source is connected to the input end of the gas distribution chamber 7. The output end of the gas distribution chamber 7 is connected to several gas delivery pipes 6. The other end of the gas delivery pipes 6 away from the gas distribution chamber 7 is connected to the input hole 12.

[0048] like Figure 4 As shown, the control system of this embodiment includes:

[0049] The acquisition module is connected to the distance sensor signal. The acquisition module is used to receive the model distance data transmitted by the distance sensor, and uses analog-to-digital conversion to generate digital distance data which is then transmitted to the processing module.

[0050] The processing module receives digital distance data, uses a preset algorithm to generate control commands, and transmits them to the control module.

[0051] The control module is used to receive control commands and generate control signals for the hydraulic cylinder 8 using pulse width modulation, which are then transmitted to the hydraulic cylinder 8. It is also used to receive control commands and generate gas injection signals for the gas distribution chamber 7 using a switch control method. Furthermore, it is used to receive control commands and generate vibration control signals for the piezoelectric ceramic actuator 13 using a frequency modulation method.

[0052] The temperature control module is connected to the heating element via a signal. The temperature control module receives the temperature data transmitted by the heating element 5 and generates a temperature control signal to be transmitted to the heating element 5 using a PID control method.

[0053] The operation flow of this embodiment is as follows: First, the control system starts the heating element 5 to heat the upper mold 1 and the lower mold 4. The temperature regulation module receives the temperature data transmitted by the heating element 5 in real time, generates a temperature regulation signal using PID control, and dynamically adjusts the power of the heating element 5 to stabilize the mold temperature within the range required for material melting. During molding, the melting of most materials stabilizes at around 200°C. When the temperature is lower than the set value, the PID algorithm calculates the deviation and increases the output signal to increase the heating power; conversely, it reduces the power to ensure precise temperature control. At the same time, an anti-stick coating, such as a polytetrafluoroethylene coating, is applied to the molding surfaces of the upper mold 1 and the lower mold 4 to further reduce initial adhesion. The thermoplastic composite prepreg is placed on the lower mold 4, and the upper mold 1 is pressed down for molding. Under heating and pressure, the material melts and fills the cavity.

[0054] After molding, the control system activates the external cooling system, circulating cooling water containing ethylene glycol solution through the cooling channels to accelerate product curing. During cooling, the distance sensor of the ejector assembly monitors the distance between the product and the surface of the lower mold 4 in real time. The acquisition module receives the analog voltage signal transmitted by the distance sensor, uses analog-to-digital conversion to generate digital distance data at a sampling rate of 1000 times per second, and transmits it to the processing module. The processing module analyzes the data according to a preset algorithm based on the product's geometric model and the demolding threshold of the material shrinkage rate. When the digital distance data indicates that the product has cooled and met the demolding conditions—for example, when the digital distance is less than 1 mm and the product temperature is below 50°C—a control command is generated and transmitted to the control module.

[0055] During demolding, the control module first receives the control command transmitted from the processing module, generates a gas injection signal using a switch control method, and triggers the gas source. High-pressure gas enters the ejector pin 10 through the gas distribution chamber 7 and the gas supply line 6, entering the ejector pin 10 through the input hole 12, and is ejected through the axial nozzle 11. Because the diameter of the nozzle 11 increases sequentially from top to bottom, the gas is evenly distributed at the interface between the product and the mold, forming a "gas film" with a thickness of approximately 0.1-0.5 mm, providing initial separation force and effectively reducing adhesion. For example, at the chamfer of the dashboard, the gas film preferentially penetrates into narrow gaps, causing the product to slightly float.

[0056] Simultaneously, the control module receives and processes a vibration control signal using frequency modulation, which is then transmitted to the piezoelectric ceramic actuator 13. The piezoelectric ceramic actuator 13 vibrates at a high frequency, which is transmitted to the surface of the product through the buffer spring 14 and the elastic pad 3, generating micro-vibrations with an amplitude of 1-5 μm, disrupting the molecular-level adhesion between the material and the mold. During vibration, the heat-insulating mica sheet prevents heat from being transferred from the mold to the actuator, ensuring its long-term stability.

[0057] The processing module generates control commands for hydraulic cylinder 8 based on real-time distance data and a preset algorithm. The control module uses pulse width modulation (PWM) to generate control signals for hydraulic cylinder 8, adjusting the output force and stroke of each hydraulic cylinder 8. The ejection area operates in a preset sequence: first, the ejector rods 10 in the chamfer and deep cavity areas are activated, ejecting slowly with low pressure while the vibrator operates; then, it gradually expands to other areas; for example, in the demolding of the instrument panel, the system ejects the edge chamfer first, then the central area, avoiding stress concentration.

[0058] The technical means disclosed in this invention are not limited to those disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features.

Claims

1. A multi-layer molding apparatus for heating and melting fiber-reinforced thermoplastic composite materials, comprising an upper mold (1) and a lower mold (4), characterized in that, The lower mold (4) is provided with several ejection components for ejecting the molded model away from the lower mold (4). Each ejection component is provided with a distance sensor. The lower mold (4) is provided with symmetrical spraying components on both sides for ejecting high-pressure gas to separate the model. Each ejection component includes a hydraulic cylinder (8) and a push rod (10). The bottom end of the push rod (10) is fixedly connected to the output end of the hydraulic cylinder (8). Each push rod (10) has several spray holes (11) axially opened. The diameter of the spray holes (11) increases from top to bottom. Each push rod (10) has an input hole (12) connected to the spraying component at the bottom. The top wall of the push rod (10) is a pneumatic diaphragm (9).

2. The multi-layer molding device for heating and melting fiber-reinforced thermoplastic composite materials according to claim 1, characterized in that, Each push rod (10) is also equipped with a piezoelectric ceramic actuator (13).

3. The multi-layer molding device for heating and melting fiber-reinforced thermoplastic composite materials according to claim 1, characterized in that, Each pneumatic diaphragm (9) has a high-temperature resistant elastic gasket (3) fixedly connected to its top.

4. The multi-layer molding device for heating and melting fiber-reinforced thermoplastic composite materials according to claim 1, characterized in that, Each injection assembly includes a gas distribution cavity (7) and a gas source symmetrically arranged in the lower mold (4). The output end of the gas source is connected to the input end of the gas distribution cavity (7). The output end of the gas distribution cavity (7) is connected to several gas delivery pipes (6). The other end of the gas delivery pipes (6) away from the gas distribution cavity (7) is connected to the input hole (12).

5. The multi-layer molding device for heating and melting fiber-reinforced thermoplastic composite materials according to claim 1, characterized in that, Heating elements (5) are provided in both the upper mold (1) and the lower mold (4).

6. The multi-layer molding device for heating and melting fiber-reinforced thermoplastic composite materials according to claim 1, characterized in that, The molding surfaces of the upper mold (1) and the lower mold (4) are coated with an anti-stick coating.

7. The multi-layer molding apparatus for heating and melting fiber-reinforced thermoplastic composite materials according to claim 6, characterized in that, The bottom of the lower mold (4) is provided with a cooling channel, which is connected to an external cooling system.

8. The multi-layer molding device for heating and melting fiber-reinforced thermoplastic composite materials according to claim 2, characterized in that, A buffer spring (14) is provided between the pneumatic diaphragm (9) and the elastic pad (3), and the buffer spring (14) is evenly distributed along the axial direction of the top rod (10).

9. The multi-layer molding device for heating and melting fiber-reinforced thermoplastic composite materials according to claim 1, characterized in that, The piezoelectric ceramic actuator (13) has a vibration frequency range of 20-50kHz, and the outer periphery of the piezoelectric ceramic actuator (13) is provided with heat-insulating mica sheets.

10. The multi-layer molding apparatus for heating and melting fiber-reinforced thermoplastic composite materials according to claim 1, characterized in that, The control system includes: The acquisition module is connected to the distance sensor signal. The acquisition module is used to receive the model distance data transmitted by the distance sensor, and uses analog-to-digital conversion to generate digital distance data which is then transmitted to the processing module. The processing module receives digital distance data, uses a preset algorithm to generate control commands, and transmits them to the control module. The control module is used to receive control commands, generate control signals for the hydraulic cylinder (8) using pulse width modulation, and transmit them to the hydraulic cylinder (8); it is also used to receive control commands, generate gas injection signals for the gas distribution chamber (7) using switch control; and it is also used to receive control commands, generate vibration control signals for the piezoelectric ceramic actuator (13) using frequency modulation. The temperature regulation module is connected to the heating element (5) via signal. The temperature regulation module is used to receive the temperature data transmitted by the heating element (5) and generates a temperature regulation signal to the heating element (5) using PID control.

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