Composite hot press forming die and stress release control method thereof

Abstract

The application discloses a composite material hot-press forming die and a stress release control method thereof. The die is mainly provided with a lateral constraint mechanism on at least one side of a cavity. The lateral constraint mechanism comprises a lateral slider capable of moving laterally and reciprocally, and the lateral slider constitutes a side wall of the cavity. The control method comprises the following steps: before entering the cooling stage of the die, reading a contact pressure, setting the pressure value as a constant-pressure following target value, and setting an allowable fluctuation range; and actively releasing residual stress by allowing the controller to drive the lateral slider to perform multiple retreat actions, so as to always maintain the contact pressure in the allowable fluctuation range of the constant-pressure following target value, and realize a stress-free accumulation state of the composite material component product in the cooling process. Therefore, the product deformation can be effectively reduced, and the product quality can be ensured.

Description

Technical Field

[0001] This invention relates to the technical field of composite materials, and in particular to a hot pressing mold for composite materials and a method for controlling stress release therefrom. Background Technology

[0002] Carbon fiber composites are high-performance, lightweight materials made of carbon fibers combined with resins or other matrices. They possess high strength, low density, and corrosion resistance, and are widely used in various industries due to these excellent properties.

[0003] Carbon fiber composite materials can be molded into various shapes and styles using compression molding processes. For example, curved CT bed plates made of carbon fiber composite materials can be produced by hot pressing and curing. However, in the current technology for hot pressing carbon fiber CT bed plates, there is a serious mismatch between the thermal expansion coefficients of the carbon steel mold and the carbon fiber CT bed plate product, leading to deformation after cooling. Specifically, the carbon fiber CT bed plate will deform and warp after the mold cools, and its flatness cannot meet the precision requirements of medical imaging equipment.

[0004] In a method for monitoring the interaction force between a mold and a component using a fiber optic grating sensor disclosed in Chinese patent CN105588673B, it is pointed out that the residual stress generated during the curing process of carbon fiber reinforced composite materials can cause component deformation. The patent proposes a method for testing the interaction force between different molds and carbon fiber reinforced composite material components in the autoclave molding process, but does not provide a method for solving this stress.

[0005] Molds made with other coefficients of thermal expansion have the following drawbacks: 1. Carbon fiber molds are not easily expanded or contracted, but they are expensive, have a short lifespan, and are not suitable for hot pressing. 2. Invar steel molds have a low coefficient of thermal expansion, but are extremely expensive and have poor thermal conductivity, and are only suitable for specific products and processes. Summary of the Invention

[0006] The purpose of this invention is to provide a composite material hot pressing mold and its stress release control method, which has the advantages of reducing mold cost, reducing product deformation, and ensuring product quality.

[0007] To achieve the above objectives, the solution of the present invention is: A stress relief control method for a composite material hot pressing mold, wherein a lateral constraint mechanism is provided on at least one side of the cavity of the mold; the lateral constraint mechanism includes a lateral slider capable of lateral reciprocating movement, the lateral slider forming a side wall of the cavity; the control method includes the following steps: (1) Before the mold is heated; the lateral slider moves forward from the initial position and contacts the side of the composite material component before molding in the cavity, and the contact pressure between the two reaches the preset initial contact pressure value to establish the initial contact state, while locking the position of the lateral slider in the current state; (2) During the main molding process in which the mold is heated to the peak process temperature and kept at that temperature, the controller of the lateral constraint mechanism continuously monitors the temperature of the mold and the contact pressure. (3) When the mold temperature reaches the peak process temperature and the heat preservation time reaches the process setting value, the main molding process is determined to be over, and the current contact pressure is read and the pressure value is set as the constant pressure following target value; enter the cooling stage, with the constant pressure following target value as the benchmark and the allowable fluctuation range is set; until the contact pressure drops to the constant pressure following target value, then enter the constant pressure control cycle mode, and periodically decide whether to adjust and move the lateral slider according to the deviation between the contact pressure and the constant pressure following target value, so as to keep the contact pressure always within the allowable fluctuation range of the constant pressure following target value, so as to achieve the state of no lateral stress accumulation of the composite material component during the cooling process, and at the same time, the mold temperature is detected in real time; (4) When the mold temperature drops to the demolding set value, the cooling stage is completed, the controller exits the constant pressure control cycle mode, drives the lateral slider of the lateral constraint mechanism to return to the initial position, and completes a single production cycle.

[0008] Furthermore, the constant pressure control loop mode in step (3) is a constant pressure control loop based on real-time pressure feedback. It continuously collects the contact pressure under the current cooling stage at a fixed period. When the contact pressure is higher than the allowable fluctuation range, it calculates the deviation between the contact pressure and the constant pressure following target value. It calculates the required displacement based on the deviation, drives the lateral slider to retract according to the displacement, and the displacement sensor provides real-time feedback of position information to form a closed-loop adjustment. Otherwise, it does not adjust the lateral slider and detects whether the mold temperature has reached the demolding set value.

[0009] Furthermore, the displacement sensor is a grating ruler.

[0010] Furthermore, the lateral slider of the lateral constraint mechanism is driven by a servo electric cylinder, and a pressure sensor for detecting the contact pressure is installed between the force application surface of the servo electric cylinder and the lateral slider; a temperature sensor for detecting the mold temperature is installed on the outside of the lateral slider.

[0011] Furthermore, the initial contact pressure value is preset as a reference pressure value, allowing a deviation range of ±20%; the constant pressure following target value is used as a reference to maintain stable contact, and can fluctuate slightly within a preset range of ±10%; the pre-retreat step is executed according to the preset displacement amount.

[0012] Compared with the prior art, the present invention has the following advantages by adopting the above solution: 1. Active management of internal stress during hot pressing is achieved. This invention transforms the traditional rigid lateral constraint into a controllable flexible lateral constraint mechanism based on real-time pressure feedback. During the heating stage, constant pressure is maintained to ensure the compaction quality of the composite component, and during the cooling stage, constant pressure is used to actively release the lateral pressure generated by mold shrinkage, thereby eliminating and reducing the accumulation of residual stress inside the composite component.

[0013] 2. Fully adaptive process compatibility. This invention uses pressure as the core control target and does not rely on preset values ​​of geometric parameters such as mold length and product thickness. Regardless of changes in mold size, the system can automatically match the total amount of heat shrinkage through multiple micro-retractions, achieving intelligent control that is "one set of parameters for all".

[0014] 3. A high-precision dual closed-loop control architecture was constructed. This invention uses a pressure sensor to form an outer force control closed loop and a grating ruler to form an inner position control closed loop. Through a multi-level linkage mechanism of pressure deviation driving displacement correction and displacement execution feedback verifying pressure fall, the invention achieves a balance between execution accuracy and force control stability.

[0015] The present invention also provides a hot pressing mold for composite materials, including an upper mold, a lower mold and a lateral restraint mechanism, wherein the upper mold and the lower mold are detachably connected and the two are closed to form a hot pressing cavity; at least one side of the cavity has a side opening, and the lateral restraint mechanism is disposed at the side opening; The lateral restraint mechanism includes a lateral slider, a slider drive assembly, a controller, a pressure sensor, and a temperature sensor; The lateral slider can reciprocate laterally to block the side opening and form one side wall of the cavity; the slider drive assembly is spaced apart on the outside of the lateral slider and is drively connected to the lateral slider; the pressure sensor is installed between the slider drive assembly and the lateral slider to detect the contact pressure between the lateral slider and the composite material component in the cavity; the temperature sensor is installed on the outside of the lateral slider to detect the temperature of the mold; the controller is electrically connected to the slider drive assembly, the pressure sensor and the temperature sensor, and controls the slider drive assembly to drive the lateral slider to slide according to the temperature and the contact pressure.

[0016] Furthermore, the lateral constraint mechanism also includes a displacement sensor electrically connected to the controller, which is mounted parallel to one side of the slider drive assembly to detect the sliding position of the lateral slider.

[0017] Furthermore, the upper mold, lower mold, and side slider are all made of S50C medium carbon steel or P20 pre-hardened mold steel; the slider drive assembly is a servo electric cylinder; the temperature sensor is a magnetic temperature sensor; and the displacement sensor is a grating ruler.

[0018] Furthermore, the cavity is used to form a carbon fiber CT bed plate; at least one side of the cavity along its length is provided with the side opening and the lateral constraint mechanism.

[0019] After adopting the above technical solution, during the mold cooling process, most molds shrink and shorten as the temperature decreases, while composite material components, due to their low coefficient of thermal expansion, basically maintain their original length. This means that the mold exerts lateral pressure on the component during cooling. However, the molding mold in this embodiment, by setting a lateral constraint mechanism, can actively retract the lateral slider according to pressure changes, releasing the lateral pressure generated by the mold on the composite material component within the cavity during cooling, thereby reducing the deformation of the composite material component. Simultaneously, it ensures that the lateral slider maintains a certain lateral pressure on the composite material component, guaranteeing its density. Therefore, the mold material is not limited; low-cost carbon steel can be used, effectively reducing mold manufacturing costs and extending mold lifespan while ensuring the quality of the hot-pressed product. Attached Figure Description

[0020] Figure 1 This is a perspective view of the mold according to an embodiment of the present invention; Figure 2 for Figure 1 Enlarged view of point A; Figure 3 This is an exploded view of the mold according to an embodiment of the present invention; Figure 4 This is a logic control diagram for the first stage of a specific embodiment of the present invention; Figure 5 This is a logic control diagram for the second stage of a specific embodiment of the present invention.

[0021] Labeling: Upper mold 1, Lower mold 2, Lateral constraint mechanism 3, Lateral slider 31, Slider drive assembly 32, Pressure sensor 33, Temperature sensor 34, Magnetic probe 341, Displacement sensor 35, Fixed base 36, Cavity 4, Side opening 41, Composite material component 5. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0023] This invention provides a composite material hot pressing mold and its stress release control method. By establishing a constant pressure control loop based on real-time pressure feedback, the internal stress generated during the hot pressing process due to the difference in thermal expansion coefficients between the mold and the composite material can be actively released and dynamically managed, thus solving the problem of component warping and deformation.

[0024] Specifically, such as Figures 1 to 3 As shown, this embodiment provides a composite material hot pressing molding die, including an upper die 1, a lower die 2 and a lateral constraint mechanism 3.

[0025] The upper mold 1 and the lower mold 2 are detachably connected and joined together to form a hot-pressed cavity 4; at least one side of the cavity 4 has a side opening 41, and the lateral constraint mechanism 3 is disposed at the side opening 41.

[0026] In this embodiment, both the upper mold 1 and the lower mold 2 are made of S50C medium carbon steel, which can effectively reduce mold costs and improve mold lifespan. Of course, the upper mold 1 and the lower mold 2 can also be made of materials such as P20 pre-hardened mold steel.

[0027] The composite material component 5 formed by the cavity 4 is exemplified by a carbon fiber CT bed plate; the side opening 41 and the lateral constraint mechanism 3 are provided on one side of the cavity 4 along its length. During the hot pressing process, the carbon steel mold in the S50C of this embodiment expands due to heat, with an axial (length) elongation of about 0.12%–0.15%, while the carbon fiber CT bed plate will elongate due to the thermal expansion of the mold under pressure.

[0028] This embodiment uses the hot pressing molding of a carbon fiber CT bed plate as an example for illustration, but it is not limited to this and can also be applied to other carbon fiber composite material products. Furthermore, for the carbon fiber CT bed plate, the mold in this embodiment only has one lateral restraint mechanism 3 on one side along the length direction. In other words, for other products, the mold can also have lateral restraint mechanisms 3 on multiple sides.

[0029] The lateral constraint mechanism 3 includes a lateral slider 31, a slider drive assembly 32, a controller (not shown), a pressure sensor 33, a temperature sensor 34, a displacement sensor 35, and a fixed base 36.

[0030] The lateral slider 31 can slide laterally back and forth to block the side opening 41 and form one side wall of the cavity 4; specifically, the lateral slider 31 can be slidably disposed at the side opening 41 provided on the lower mold 2, and the lateral slider 31 can be made of S50C medium carbon steel or P20 pre-hardened mold steel, etc.

[0031] The slider drive assembly 32 can be installed at intervals on the fixed base 36 on the outside of the side slider 31. The fixed base 36 can be locked or welded to the lower mold 2. The slider drive assembly 32 can be a servo electric cylinder or the like that connected to the side slider 31 in transmission, which can drive the side slider 31 to perform step sliding.

[0032] The pressure sensor 33 can be installed between the force-applying surface of the slider drive assembly 32 and the lateral slider 31 to detect the contact pressure between the lateral slider 31 and the composite material component 5 in the cavity 4.

[0033] The temperature sensor 34 can be installed on the outside of the side slider 31 to detect the temperature of the mold. Specifically, it can be a magnetic temperature sensor 34, whose magnetic probe 341 can be easily magnetically attached and fixed to the outer surface of the carbon steel side slider 31. Since the side slider 31 is a side wall of the mold cavity and has a tight fit with the upper mold 1 and the lower mold 2, the temperature of the entire mold can be accurately obtained by measuring the temperature of the side slider 31. Of course, the temperature sensor 34 can also be installed in other locations and is not limited to the setting of this embodiment.

[0034] The displacement sensor 35 can be a grating ruler and can be installed in parallel on one side of the slider drive assembly 32, and can detect the sliding position of the lateral slider 31.

[0035] The controller may be a PLC controller and is electrically connected to the slider drive assembly 32, the pressure sensor 33, the temperature sensor 34 and the displacement sensor 35. It controls the slider drive assembly 32 to drive the lateral slider 31 to perform adaptive quantitative sliding adjustment based on the temperature, contact pressure and sliding position.

[0036] During the mold cooling process, the mold shrinks and shortens as the temperature drops, while the carbon fiber CT bed plate, due to its low coefficient of thermal expansion, maintains its original length. This means that the mold exerts lateral pressure on the carbon fiber CT bed plate during cooling, primarily concentrated along its axial length. (Since the carbon fiber CT bed plate has a smaller thickness in the height direction perpendicular to the axial direction, the deformation under pressure is smaller. Similarly, the width direction perpendicular to the axial direction is also small and has a curved surface, resulting in minimal deformation under pressure and minimal impact on the bed plate's accuracy.) In this embodiment, the molding mold, by incorporating a lateral constraint mechanism 3 located on one side of the length direction, can actively retract the lateral slider 31 according to pressure changes. This releases the lateral pressure generated by the mold on the composite material component 5 within the cavity 4 during cooling, thereby reducing deformation of the composite material component 5 and ensuring the flatness of the carbon fiber CT bed plate meets requirements. Simultaneously, it ensures that the lateral slider 31 maintains a certain lateral pressure on the composite material component 5 to guarantee its density.

[0037] Based on the above-mentioned mold, this embodiment proposes a stress relief control method for composite material hot pressing molds, including the following steps: (1) Before the mold is heated; the lateral slider 31 moves forward from the initial position and contacts the side of the composite material component 5 before molding in the cavity 4, and the contact pressure between the two reaches the preset initial contact pressure value to establish the initial contact state, while locking the position of the lateral slider 31 in the current state; the initial contact pressure value is preset as the reference pressure value, and a deviation range of ±20% is allowed, in order to ensure that the lateral slider 31 can reliably contact the composite material component 5, and avoid excessive pressure that damages the uncured composite material component 5.

[0038] (2) During the main molding process in which the mold is heated to the peak process temperature and kept warm, the controller of the lateral constraint mechanism 3 continuously monitors the temperature of the mold and the contact pressure, while the lateral slider 31 remains locked and does not actively adjust. In this embodiment, the lateral slider 31 is driven to move by the slider drive assembly 32. When it remains locked, the controller instructs the slider drive assembly 32 to stop driving, so that the lateral slider 31 remains in a constant relative position with the fixed base 36, that is, the lateral slider 31 remains in a constant relative position with the lower mold 41, thereby realizing that the lateral slider 31 passively moves with the mold during heating, without actively squeezing the product.

[0039] (3) When the mold temperature reaches the process peak temperature and the heat preservation time reaches the process setting value, the main molding process is determined to be over, the current contact pressure is read, and the pressure value is set as the constant pressure following target value; then the cooling stage is entered.

[0040] After entering the cooling stage of the mold, the constant pressure following target value is used as a reference, and an allowable fluctuation range is set; the constant pressure following target value is used to maintain stable contact and can fluctuate slightly within ±10%, that is, the allowable fluctuation range is set to 90%-110% of the constant pressure following target value.

[0041] By having the controller drive the lateral slider 31 to perform a retraction action at least once, residual stress is actively released until the contact pressure is reduced to within the allowable fluctuation range of the constant pressure following target value, and then the constant pressure control cycle mode is entered; the pre-retraction step distance of the retraction action is executed according to the preset displacement amount.

[0042] In the constant pressure control cycle mode, the contact pressure is periodically detected and the deviation between the contact pressure and the constant pressure following target value is used to determine whether to adjust and move the lateral slider 31 so that the contact pressure is always maintained within the allowable fluctuation range of the constant pressure following target value, thereby achieving a state of no lateral stress accumulation in the composite material component 5 during the cooling process, while the mold temperature is detected in real time.

[0043] The constant pressure control loop mode is a constant pressure control loop based on real-time pressure feedback. It continuously collects the contact pressure under the current cooling stage at a fixed period. When the contact pressure is higher than the allowable fluctuation range, it calculates the deviation between the contact pressure and the constant pressure following target value, calculates the required displacement based on the deviation, drives the lateral slider 31 to retract or move forward according to the displacement, and the displacement sensor 35 provides real-time feedback of position information to form a closed-loop adjustment; otherwise, it does not adjust the lateral slider 31 and detects whether the mold temperature has reached the demolding set value.

[0044] (4) When the mold temperature drops to the demolding set value, exit the constant pressure control cycle mode, drive the lateral slider 31 of the lateral constraint mechanism 3 to return to the initial position, and complete a single production cycle.

[0045] In summary, the present invention has at least the following advantages: 1. Active management of internal stress during hot pressing is achieved. This invention transforms the traditional rigid lateral constraint into a controllable flexible lateral constraint mechanism 3 based on real-time pressure feedback. During the heating stage, constant pressure is maintained to ensure the compaction quality of the composite component 5. During the cooling stage, constant pressure is used to actively release the lateral pressure generated by mold shrinkage, thereby eliminating and reducing the accumulation of residual stress inside the composite component 5.

[0046] 2. Fully adaptive process compatibility. This invention uses pressure as the core control target and does not rely on preset values ​​of geometric parameters such as mold length and product thickness. Regardless of changes in mold size, the system can automatically match the total amount of heat shrinkage through multiple micro-retractions, achieving intelligent control that is "one set of parameters for all".

[0047] 3. A high-precision dual closed-loop control architecture was constructed. This invention uses a pressure sensor 33 to form an outer force control closed loop and a grating ruler to form an inner position control closed loop. Through a multi-level linkage mechanism of pressure deviation driving displacement correction and displacement execution feedback verifying pressure fall, the invention achieves a balance between execution accuracy and force control stability.

[0048] The following combination Figure 4 and Figure 5 Specific examples will be used to illustrate this: Phase 1: Heating and Insulation Phase Step S11: Establish initial contact state Before the mold is unloaded or before the first component is produced, the lateral slider 31 is controlled to advance at an extremely low speed (0.1 mm / s); the grating ruler records the displacement increment, and the pressure sensor 33 records the pressure increment.

[0049] During the forward movement of the lateral slider 31, the pressure sensor 33 detects the contact pressure in real time. Based on process testing or experience, in this embodiment, the PLC controller sets the initial contact pressure value to 0.2 kN. When the contact pressure first reaches the initial contact pressure value of 0.2 kN, the PLC controller immediately stops the movement of the lateral slider 31 and locks the current position of the lateral slider 31.

[0050] Step S12 Heating and Insulation The mold is heated and continues to be heated to the peak process temperature and held at the preset process setting value to achieve hot pressing molding of composite material component 5; During the hot pressing process, temperature sensor 34 continuously collects mold temperature data with a period of 200 milliseconds. Pressure sensor 33 reads the current contact pressure and transmits the temperature and contact pressure data to the PLC controller in real time. When the mold temperature reaches the peak process temperature and the holding time reaches the set process value, the main molding process is considered complete. The current contact pressure is then read and set as the constant pressure following target value. The position information of the lateral slider 31 is also read and recorded using a grating ruler.

[0051] Phase 2: Cooling Phase Step S21: Cooling Start-up and Initial Adjustment After the cooling stage begins, the mold attempts to drive the lateral slider 31 to further compress the composite material component 5, causing the pressure sensor 33 to detect an upward pressure trend and determine that the pressure release process has entered the constant pressure control cycle mode.

[0052] Specifically, when the heat preservation time reaches the process set value, the PLC controller uses the constant pressure follow target value as the benchmark for pressure control and sets the allowable pressure fluctuation range to ±10% of the constant pressure follow target value. If an upward pressure trend is detected and the current pressure is higher than the target value and exceeds the allowable fluctuation range, the PLC controller system first instructs the lateral slider 31 to perform a pre-retreat, with a preset displacement step of 0.2mm. The servo cylinder is then instructed to perform the displacement, while the grating ruler provides real-time feedback on the actual position of the lateral slider 31 to ensure accurate displacement execution. The grating ruler confirms whether the displacement is in place based on the position information obtained in the first stage. After execution, the system returns to continue reading the pressure until it falls back to the allowable fluctuation range. Then, the "constant pressure control" main loop is entered; otherwise, another pre-retreat is performed.

[0053] Step 22: Enter constant pressure control cycle mode This phase runs continuously with a period of 100ms, and performs the following actions in each period: Read the current contact pressure; calculate the deviation between the current contact pressure and the constant pressure following target value; If the absolute value of the deviation is within the deviation range (the deviation range is the difference between the allowable fluctuation range and the constant pressure following target value), no adjustment is needed, and the temperature judgment is directly entered; by defining the deviation range, the current contact pressure can be quickly determined to be outside the allowable fluctuation range by comparing the magnitude of the deviation and the deviation range.

[0054] If the deviation exceeds the deviation range, then: calculate the required displacement based on the magnitude of the deviation (the specific displacement calculation method can refer to existing technology). The PLC controller instructs the servo cylinder to retract or move the lateral slider 31 at low speed according to the displacement. The retraction of the lateral slider 31 is used to match the shrinkage of the mold and prevent excessive lateral pressure on the product, while the forward movement of the lateral slider 31 is used to prevent insufficient lateral pressure on the product. The accuracy of the product is ensured through dynamic adjustment.

[0055] The grating ruler provides real-time feedback on the position of the lateral slider 31, forming a position closed loop to ensure accurate displacement execution. After displacement execution, the pressure sensor 33 displays that the pressure has fallen back to near the target value, and returns to step 22 to continue the cyclic monitoring.

[0056] Throughout the cooling process (the mold temperature drops from 135°C to 40°C), the above-mentioned adjustment cycle runs continuously at a frequency of 10 times per second. The lateral slider 31 retracts slightly multiple times according to the pressure deviation, and the total cumulative displacement automatically matches the thermal shrinkage of the mold, so that the lateral extrusion pressure of the composite material component 5 is always precisely controlled at a low level of ±10% of the constant pressure following the target value, achieving a state of no lateral stress accumulation.

[0057] Step 23: Cooling End and Reset During the constant pressure control cycle, temperature sensor 34 continuously monitors the mold temperature. When the mold temperature drops to the demolding set value (40℃), the PLC controller determines that the cooling stage is complete and exits the constant pressure control cycle. The PLC controller switches to position control mode, and instructs the servo cylinder to drive the lateral slider 31 at medium speed to return to the preset position. The grating ruler verifies the reset accuracy throughout the process. After the reset is complete, the PLC controller's human-machine interface displays "Cycle complete, demolding ready," awaiting the operator to open the mold and remove the parts, and the start of the next production cycle.

[0058] The above description is merely a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, equivalent changes and modifications without departing from the principle of the present invention should still fall within the scope of protection of the present invention.

[0059] In the description of the embodiments of this application, it should be understood that the indicated orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, or the orientations or positional relationships commonly used when the product is in use, or the orientations or positional relationships commonly understood by those skilled in the art. These are only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. In the description of this application, "a plurality of" and "several" mean two or more, unless otherwise explicitly specified.

[0060] In the description of the embodiments of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows for mutual communication; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0061] Furthermore, this application provides examples of various specific processes and materials, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

Claims

1. A method for stress relief control of a composite material hot pressing mold, characterized in that: A lateral constraint mechanism is provided on at least one side of the cavity of the mold; the lateral constraint mechanism includes a lateral slider capable of lateral reciprocating movement, the lateral slider forming one side wall of the cavity; the control method includes the following steps: (1) Before the mold is heated; the lateral slider moves forward from the initial position and contacts the side of the composite material component before molding in the cavity, and the contact pressure between the two reaches the preset initial contact pressure value to establish the initial contact state, while locking the position of the lateral slider in the current state; (2) During the main molding process in which the mold is heated to the peak process temperature and kept at that temperature, the controller of the lateral constraint mechanism continuously monitors the temperature of the mold and the contact pressure, and the lateral slider remains locked and does not make active adjustments. (3) When the mold temperature reaches the process peak temperature and the heat preservation time reaches the process set value, the main molding process is determined to be over, the current contact pressure is read, and the pressure value of the obtained contact pressure is set as the constant pressure following target value. Entering the cooling phase, the constant pressure following target value is used as a reference, and an allowable fluctuation range is set; When the contact pressure is detected to be rising and exceeding the allowable fluctuation range, at least one lateral slider retraction action is performed until the contact pressure is reduced to the allowable fluctuation range, and then the constant pressure control cycle mode is entered. In the constant pressure control cycle mode, the contact pressure is periodically detected and the deviation between the contact pressure and the constant pressure following target value is used to determine whether to adjust and move the lateral slider, so that the contact pressure is always maintained within the allowable fluctuation range of the constant pressure following target value, thereby achieving a state of no lateral stress accumulation in the composite material component during the cooling process, while the mold temperature is detected in real time. (4) When the mold temperature drops to the demolding set value, the cooling stage is completed, the controller exits the constant pressure control cycle mode, drives the lateral slider of the lateral constraint mechanism to return to the initial position, and completes a single production cycle.

2. The stress relief control method for a composite material hot pressing mold according to claim 1, characterized in that: The constant pressure control loop mode in step (3) is a constant pressure control loop based on real-time pressure feedback. It continuously collects the contact pressure under the current cooling stage at a fixed period. When the contact pressure is higher than the allowable fluctuation range, it calculates the deviation between the contact pressure and the constant pressure following target value, calculates the required displacement based on the deviation, drives the lateral slider to retract according to the displacement, and the displacement sensor provides real-time feedback of position information to form a closed-loop adjustment. Otherwise, the lateral slider is not adjusted, and it is detected whether the mold temperature has reached the demolding set value.

3. The stress relief control method for a composite material hot pressing mold according to claim 2, characterized in that: The displacement sensor is a grating ruler.

4. The stress relief control method for a composite material hot pressing mold according to claim 1, characterized in that: The lateral slider of the lateral constraint mechanism is driven by a servo electric cylinder. A pressure sensor for detecting the contact pressure is installed between the force application surface of the servo electric cylinder and the lateral slider. A temperature sensor for detecting the temperature of the mold is installed on the outside of the lateral slider.

5. The stress relief control method for a composite material hot pressing mold according to claim 1, characterized in that: The allowable fluctuation range is 90%-110% of the constant pressure following the target value.

6. A composite material hot pressing mold, comprising an upper mold and a lower mold, wherein the upper mold and the lower mold are detachably connected and joined together to form a hot pressing cavity; characterized in that, Also includes: Lateral restraint mechanism; The cavity has a side opening on at least one side, and the lateral restraint mechanism is disposed at the side opening; The lateral restraint mechanism includes a lateral slider, a slider drive assembly, a controller, a pressure sensor, and a temperature sensor; The lateral slider can reciprocate laterally to block the side opening and form one side wall of the cavity; the slider drive assembly is spaced apart on the outside of the lateral slider and is drively connected to the lateral slider; the pressure sensor is installed between the slider drive assembly and the lateral slider to detect the contact pressure between the lateral slider and the composite material component in the cavity; the temperature sensor is installed on the outside of the lateral slider to detect the temperature of the mold; the controller is electrically connected to the slider drive assembly, the pressure sensor and the temperature sensor, and controls the slider drive assembly to drive the lateral slider to slide according to the temperature and the contact pressure.

7. A composite material hot pressing mold according to claim 6, characterized in that: The lateral constraint mechanism also includes a displacement sensor electrically connected to the controller. The displacement sensor is mounted parallel to one side of the slider drive assembly and is used to detect the sliding position of the lateral slider.

8. A composite material hot pressing mold according to claim 7, characterized in that: The upper mold, lower mold, and side slider are all made of S50C medium carbon steel or P20 pre-hardened mold steel; the slider drive assembly is a servo electric cylinder; the temperature sensor is a magnetic temperature sensor; and the displacement sensor is a grating ruler.

9. A composite material hot pressing mold according to claim 6, characterized in that: The cavity is used to form a carbon fiber CT bed plate; at least one side of the cavity along its length is provided with the side opening and the lateral constraint mechanism.

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