A method for precision injection molding of fiber-reinforced propellers based on polymorphic compensation

Abstract

The present application relates to a kind of fibre-reinforced propeller precision injection molding method based on polymorphism compensation.The method steps of the present application are as follows:1) establish a shrinkage prediction model for fibre-reinforced thermoplastic composite material;2) carry out conventional injection molding simulation by shrinkage prediction model, and the deformation result of product is predicted;3) shrinkage prediction model and simulation result and solidification are specific design rules for propeller type product;4) according to the shrinkage prediction model after correction according to above anti-deformation strategy, design and process corresponding injection mold;5) implant pressure sensor and optical fiber temperature detector in the key position of mold cavity;6) define a set of multi-stage injection pressure curve optimized for fibre-reinforced propeller;7) through special-shaped runner design or independent pressure control of multiple hot runner nozzles.The present application can guarantee the profile accuracy of propeller, internal quality stability and mechanical property consistency.

Description

Technical Field

[0001] This invention belongs to the field of precision injection molding technology of polymer materials, specifically relating to a precision injection molding method for fiber-reinforced propellers based on multi-state compensation, with particular focus on solving the technical challenges of shape and property control during the molding process through multi-state compensation. Background Technology

[0002] With the rapid development of low-altitude aircraft technology and unmanned underwater vehicle (UUV) technology, the demand for high-performance materials in the fields of low-altitude aircraft technology, marine technology, and intelligent equipment technology is increasing. In low-altitude aircraft and unmanned underwater vehicles (UUVs), propellers, as key components that withstand high-cycle fatigue and impact, need to have good impact resistance and long-term service capability.

[0003] Compared to traditional metals and thermosetting materials, thermoplastic fiber-reinforced composites have significant advantages such as low water absorption, excellent corrosion resistance, fatigue resistance, impact resistance, high specific strength, and production efficiency. They are better suited to harsh environmental conditions such as humid / hot, dry / cold, sandstorms / rainforests, and seawater. Therefore, thermoplastic fiber-reinforced composites have great potential in the application of unmanned aerial vehicles (UAVs) and unmanned underwater vehicles (UUVs).

[0004] Thermoplastic fiber-reinforced composite injection-molded propellers face the following challenges: 1) Anisotropic shrinkage leading to warping: The reinforcing fibers exhibit an oriented distribution during injection molding, resulting in inconsistent shrinkage rates in different directions of the propeller. This anisotropic shrinkage makes thin-walled complex structures such as propeller blades prone to warping and twisting, making it difficult to meet the requirements for blade profile accuracy and dynamic balance performance; 2) Fiber distribution and orientation are difficult to control precisely: During injection molding, the distribution and orientation of fibers are greatly affected by the runner design and process parameters. Irregular fiber orientation not only causes uneven shrinkage but also leads to poor consistency in the mechanical properties of the propeller, affecting its service life and reliability; 3) Molding internal stress and springback: Residual stress exists in thermoplastic composites after molding, and the stress release after demolding causes the component to spring back. For fiber-reinforced composites, the causes of this problem are more complex. Traditional mold design and process adjustment rely heavily on experience and trial and error, resulting in long development cycles and high costs. 4) Traditional deformation compensation methods are simplistic and lack adaptability: Existing technologies mostly employ anti-deformation mold design based on uniform shrinkage rate or fixed parameter process adjustments. This method is difficult to effectively cope with complex deformations caused by nonlinearity and multi-factor coupling in fiber-reinforced materials, and lacks online adjustment and adaptive compensation capabilities. Summary of the Invention

[0005] To address the aforementioned technical problems in the background art, this invention provides a precision injection molding method for fiber-reinforced propellers based on multi-mode compensation, ensuring the propeller's surface accuracy, internal quality stability, and consistency of mechanical properties.

[0006] The technical solution of this invention is as follows: This invention is a precision injection molding method for fiber-reinforced propellers based on multi-mode compensation, characterized in that the method includes the following steps: 1) Establish a shrinkage prediction model for fiber-reinforced thermoplastic composites; the inputs to the shrinkage prediction model include the length of the reinforcing fiber, the thermal shrinkage rate of the thermoplastic matrix, the injection flow rate, and the local wall thickness; 2) The deformation result of the product is predicted by performing a conventional injection molding simulation using a shrinkage prediction model. Then, this deformation result is used as the initial input, and the mold cavity surface is adjusted in reverse through a reverse iterative algorithm until the final product surface that meets the design requirements is simulated. 3) Integrate the shrinkage prediction model and simulation results into specific design rules for propeller-type parts; 4) Design and process the corresponding injection mold based on the shrinkage prediction model modified by the above anti-deformation strategy; 5) Implant pressure sensors and fiber optic temperature sensors at key locations in the mold cavity; dynamically adjust the switching point and magnitude of the injection pressure based on the real-time feedback of the in-mold pressure and temperature data from the sensors; 6) Define a set of optimized multi-stage injection pressure curves for fiber-reinforced propellers, and clarify the control objectives for each stage: 7) By using irregular flow channel design or independent pressure control of multiple hot runner nozzles, different pressure holding pressures are applied to different areas of the propeller during the pressure holding stage.

[0007] Furthermore, the specific design rules in step 3) include suggestions for different anti-deformation amounts for the blade root and tip, blade profile compensation coefficients for different twist angles, and reinforcement strategies for the hub-blade connection.

[0008] Furthermore, in step 4), when designing the injection mold, continuous fiber reinforcement is achieved by prefabricating a continuous fiber-reinforced skeleton along the main load-bearing path of the blade and then injection molding it; and mechanical locking of the matrix is ​​achieved by designing a groove array at the mold-part interface.

[0009] Furthermore, the key locations of the mold cavity in step 5) are the gate, the blade end, and the blade hub.

[0010] Furthermore, step 6) includes the following three stages: The first stage is high-speed filling; The second stage is the first pressure holding stage; The third stage is the second / third stage of pressure holding.

[0011] Furthermore, the first stage specifically involves using a higher injection speed to ensure that the fibers are not frozen before reaching the end, and precise control through the v / p switching point to prevent jetting and excessive shearing from generating heat.

[0012] Furthermore, the second stage specifically involves using higher pressure to compensate for the shrinkage of thick-walled areas such as the hub and thick areas of the blades, and to force the fibers to be oriented at a certain angle in the core to enhance rigidity.

[0013] Furthermore, the third stage specifically involves using progressively decreasing pressure to focus on controlling fiber stability and reducing orientation internal stress in thin-walled areas such as blade edges and hub end faces, thereby reducing warping.

[0014] This invention provides a precision injection molding method for fiber-reinforced propellers based on multi-state compensation, comprising two aspects: shape and property control anti-deformation design for fiber-reinforced thermoplastic composite propellers and a multi-level collaborative control process for injection pressure based on precise fiber state regulation. The shape and property control anti-deformation design for fiber-reinforced thermoplastic composite propellers involves establishing a predictive model of anisotropic shrinkage rate considering fiber orientation, utilizing a cavity reverse compensation surface generation method based on coupled simulation, and ultimately forming propeller-specific anti-deformation design rules that integrate structure and process. The multi-level collaborative control process for injection pressure based on precise fiber state regulation is an adaptive pressure control strategy using real-time in-mold sensor data as feedback. It generates a multi-stage precise switching and parameter set of "speed-pressure-holding pressure" optimized for fiber distribution and orientation, ultimately forming a method for constructing a differentiated holding pressure field based on the functional requirements of different parts. Therefore, this invention has the following advantages: 1) This invention revolves around the core concept of "multi-state compensation," and systematically innovates from multiple dimensions and stages, including "mold design," "process structure," and "material structure." From a static pre-compensation perspective, it employs anti-deformation design to accurately predict and compensate for deformation caused by anisotropic shrinkage. From a dynamic real-time compensation perspective, it utilizes multi-level control design for the injection molding process to regulate fiber state in real time and suppress defects.

[0015] 2) This invention, through simulation-based digital anti-deformation design, multi-parameter real-time sensing and adaptive control, and collaborative design of materials and structures, can offset deformation from the source stage of mold design, actively control fiber distribution and residual stress, and improve dimensional stability from the product itself, thus ensuring the dimensional accuracy and internal quality stability of the parts.

[0016] 3) High system integration: This invention integrates mold, process, and materials as a whole system for collaborative optimization, which solves the limitations of single methods.

[0017] 4) Strong adaptability: This invention has online monitoring and feedback capabilities, which can adapt to material fluctuations and environmental changes, ensuring batch stability.

[0018] 5) High precision: This invention achieves precise control over complex deformation and fiber orientation through high-precision simulation and real-time adjustment.

[0019] 6) Good versatility: The "multi-state compensation" framework of this invention can be extended to injection molding of other fiber-reinforced complex components with high precision and high performance requirements. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the propeller's shape.

[0021] Figure 2 This is a schematic diagram of the injection molding flow channel of the present invention.

[0022] The attached figures are labeled as follows: 1. First gate; 2. Second gate; 3. First riser; 4. Second riser. Detailed Implementation

[0023] This invention provides a precision injection molding method for fiber-reinforced propellers based on multi-mode compensation. The specific steps of the embodiment are as follows: 1) Establish a shrinkage prediction model for fiber-reinforced thermoplastic composites; the inputs to the shrinkage prediction model include the length of the reinforcing fiber, the thermal shrinkage rate of the thermoplastic matrix, the injection flow rate, and the local wall thickness; 2) The deformation result of the product is predicted by performing a conventional injection molding simulation using a shrinkage prediction model. Then, this deformation result is used as the initial input, and the mold cavity surface is adjusted in reverse through a reverse iterative algorithm until the final product surface that meets the design requirements is simulated. 3) Solidify the shrinkage rate prediction model and simulation results into specific design rules for propeller-type components; the specific design rules include suggestions for different anti-deformation amounts for the blade root and blade tip, blade profile compensation coefficients for different twist angles, and reinforcement strategies for the connection between the blade hub and the blade. 4) Design and process the corresponding injection mold based on the shrinkage prediction model modified by the above anti-deformation strategy; when designing the injection mold; achieve continuous fiber local reinforcement by prefabricating a continuous fiber reinforced skeleton in the main load-bearing path of the blade and then injection molding it; and mechanically lock the matrix by designing a groove array at the mold-part interface. 5) Implant pressure sensors and fiber optic temperature sensors at key locations in the mold cavity; dynamically adjust the switching point and magnitude of injection pressure based on real-time feedback of in-mold pressure and temperature data from the sensors; key locations in the mold cavity are the gate, the blade end, and the blade hub. 6) Define a set of optimized multi-stage injection pressure curves for fiber-reinforced propellers, and clarify the control objectives for each stage: specifically including the following three stages: The first stage is high-speed filling; a high injection speed is used to ensure that the fibers are not frozen before reaching the end, and precise control is achieved through the v / p switching point to prevent jetting and excessive shearing from generating heat.

[0024] The second stage is the first-level pressure holding stage; higher pressure is used to compensate for the shrinkage of thick-walled areas such as the hub and thick areas of the blades, and to force the fibers to be oriented at a certain angle in the core to enhance rigidity. The third stage involves secondary / tertiary pressure holding; using progressively decreasing pressure, the focus is on controlling fiber stability and reducing orientation internal stress in thin-walled areas such as blade edges and hub end faces, thereby reducing warping.

[0025] 7) By using irregular flow channel design or independent pressure control of multiple hot runner nozzles, different pressure holding pressures are applied to different areas of the propeller during the pressure holding stage.

[0026] The overall solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: The specific embodiments of the present invention are as follows: 1) CAE accurate prediction model; Based on multiphysics coupling simulation and fiber orientation tensor model, a coherent coupling analysis of melt flow-pressure holding-fiber orientation-thermal stress-structural deformation sequence is performed. The Folga-Tucker model is used to predict fiber orientation, and its orientation tensor is used as the input for shrinkage calculation. The anisotropic thermo-elastic-plastic body constitutive model is used to calculate non-uniform shrinkage stress and deformation, and finally the anisotropic shrinkage and warping predicted deformation caused by fibers is formed.

[0027] 2) Adaptive control algorithm; See Figure 2 Based on model predictive control and digital coupling online calibration, during the segmented injection process, sensors are first implanted at the first gate 1, second gate 2, first riser 3, and second riser 4 to monitor the intramold pressure and temperature in real time. The sensor data is transmitted in real time to the state estimator, and the actuators are dynamically adjusted through the MPC controller. Model predictive control (MPC) dynamically solves for the optimal pressure and temperature trajectory using a rolling optimization method. The online monitoring data is fed back to the simulation model in real time for model parameter calibration, improving prediction reliability. This enables the implementation of process control measures to compensate for raw material fluctuations and optimize fiber state.

[0028] 3) Material structural optimization design; By prefabricating a continuous fiber-reinforced skeleton along the main load-bearing path of the blade and then injection molding it, continuous fiber local reinforcement is achieved. By designing the mold-part interface as a groove array and mechanically locking the matrix, the interface microstructure design is achieved, which suppresses part shrinkage, peeling and springback.

[0029] The following are specific application examples of the present invention. Example 1

[0030] See Figure 1 , 2 High-temperature nylon injection molding granules reinforced with glass fiber are used, with a glass fiber content of 30% and a fiber length of 1.5mm. Four miniature pressure sensors and four thermocouples are embedded in the propeller mold cavity at the root, middle, tip, and hub of the propeller blades. The injection molding machine is equipped with a high-frequency servo valve and a high-precision closed-loop controller. Initial process parameters for the injection molding machine are set as follows: melt temperature 290℃, injection speed 80cm / s. 3 / s, the first-stage holding pressure is 80MPa for 2s, and the second-stage holding pressure is 60MPa for 5s; after injection filling, the holding stage begins. The system reads the pressure values ​​P1(t), P2(t), P3(t), and P4(t) at the above four monitoring points in real time at a frequency of 100Hz; the MPC controller of the central processing unit has a built-in simplified holding pressure decay prediction model. This model predicts the pressure decay curve within the next 2 seconds based on the measured pressure values ​​at each point at the current moment, and compares it with the ideal "equal pressure gradient" decay trajectory; if the model predicts that the blade tip pressure will be lower than the lower limit of the ideal trajectory within the next 0.5 seconds, the MPC controller will immediately output a command to increase the second-stage holding pressure from 60MPa to 65MPa and extend the holding time of this stage by 0.6s to supplement more melt to the thin-walled area with more severe contraction; repeat the above steps until the gate freezes, and the holding stage ends. Example 2

[0031] For a certain type of UAV propeller (maximum diameter 300mm, blade length 120mm), CAE simulation was used. The material model, using Moldex3D or the equivalent software's Anisotropic Orthotropic model, predicted that the blade tip would tilt upwards by 0.5mm under free contraction. Based on this, the mold cavity was modified with reverse compensation, i.e., a negative offset of 0.5mm was made at the corresponding position in the lower mold cavity. The local reinforcing skeleton used T700 grade continuous fiber PA66 prepreg, pre-formed by hot pressing, and an "I"-shaped beam skeleton (volume fraction 60%) was used to suppress the main stress path of the blade. After mold opening, the pre-formed continuous fiber reinforced skeleton was precisely placed in the positioning groove of the lower mold; the mold was closed, and injection molding was performed according to conventional parameters. The short fiber reinforced PA66 melt enveloped the pre-formed skeleton and filled the cavity designed with reverse deformation; after cooling, the mold was opened and the part was ejected. Due to the reverse deformation compensation, the demolded blade springed back to the theoretically designed shape. Example 3

[0032] A high-fidelity simulation model corresponding to the physical system at a 1:1 scale is established in ANSYS or an equivalent platform. The core is a multi-scale simulation workflow: Moldex3D is used to simulate flow, fiber orientation (Folgar-Tucker model), and cooling, and the results are mapped to ANSYS Mechanical for anisotropic thermo-structural coupled stress analysis to predict deformation; virtual-physical communication is achieved through protocols such as OPC UA, and every 10 simulations, the system automatically compares the measured pressure and temperature curves of the most recent simulation with the virtual prediction curves. The system automatically runs simulations on the CAE simulator with the target of "blade tip runout < 0.15mm" to optimize the best anti-deformation surface data, cooling pipe layout, and five-segment injection pressure curve (injection pressure 90MPa→70MPa→holding pressure 1:85MPa→holding pressure 2:65MPa→holding pressure 3:50MPa). In actual production, if the system finds that the time-measured holding pressure at the blade tip decreases more than 5% faster than the virtual predicted value, it determines that the actual material flowability deviates from the standard parameters. The system will automatically reverse-calibrate the material viscosity model parameters in the CAE model to ensure that the virtual model is consistent with the physical world. The calibrated high-precision CAE model can be used for predictive maintenance. For example, if the system analysis finds that the simulated cooling efficiency value continues to deviate from the actual value, it can warn that "the cooling water channel may be partially blocked, and it is recommended to arrange cleaning after the 300th simulation".

[0033] The technical contents of this invention and those not specifically described in the above embodiments are the same as those in the prior art.

[0034] The above are merely specific embodiments disclosed in this invention, but the scope of protection disclosed in this invention is not limited thereto. The scope of protection disclosed in this invention should be determined by the scope of the claims.

Claims

1. A precision injection molding method for fiber-reinforced propellers based on multi-mode compensation, characterized in that: The method includes the following steps: 1) Establish a shrinkage prediction model for fiber-reinforced thermoplastic composites; the model inputs include the length of the reinforcing fiber, the thermal shrinkage rate of the thermoplastic matrix, the injection flow rate, and the local wall thickness; 2) The deformation result of the product is predicted by performing a conventional injection molding simulation using a shrinkage prediction model. Then, this deformation result is used as the initial input, and the mold cavity surface is adjusted in reverse through a reverse iterative algorithm until the final product surface that meets the design requirements is simulated. 3) Integrate the shrinkage rate prediction model and simulation results into specific design rules for propeller-type parts; 4) Design and process the corresponding injection mold based on the shrinkage prediction model modified by the above anti-deformation strategy; 5) Implant pressure sensors and fiber optic temperature sensors at key locations in the mold cavity; dynamically adjust the switching point and magnitude of the injection pressure based on the real-time feedback of the in-mold pressure and temperature data from the sensors; 6) Define a set of optimized multi-stage injection pressure curves for fiber-reinforced propellers, and clarify the control objectives for each stage: 7) By using irregular flow channel design or independent pressure control of multiple hot runner nozzles, different pressure holding pressures are applied to different areas of the propeller during the pressure holding stage.

2. The precision injection molding method for fiber-reinforced propellers based on multi-mode compensation according to claim 1, characterized in that: The specific design rules in step 3) include suggestions for different anti-deformation amounts for the blade root and tip, blade profile compensation coefficients for different twist angles, and reinforcement strategies for the connection between the blade hub and the blade.

3. The precision injection molding method for fiber-reinforced propellers based on multi-state compensation according to claim 2, characterized in that: In step 4), when designing the injection mold, continuous fiber reinforcement is achieved by prefabricating a continuous fiber-reinforced skeleton along the main load-bearing path of the blade and then injection molding it; and the substrate is mechanically locked by designing a groove array at the mold-part interface.

4. The precision injection molding method for fiber-reinforced propellers based on multi-state compensation according to claim 3, characterized in that: The key locations of the mold cavity in step 5) are the gate, the blade end, and the blade hub.

5. The precision injection molding method for fiber-reinforced propellers based on multi-state compensation according to claim 4, characterized in that: Step 6) includes the following three stages: The first stage is high-speed filling; The second stage is the first pressure holding stage; The third stage is the second / third stage of pressure holding.

6. The precision injection molding method for fiber-reinforced propellers based on multi-state compensation according to claim 5, characterized in that: The first stage specifically involves using a high injection speed to ensure that the fiber is not frozen before reaching the end, and precise control through the v / p switching point to prevent jetting and excessive shearing from generating heat.

7. The precision injection molding method for fiber-reinforced propellers based on multi-mode compensation according to claim 5, characterized in that: The second stage involves using higher pressure to compensate for the shrinkage of thick-walled areas such as the hub and thick blade regions, and to force the fibers to be oriented at a certain angle in the core to enhance rigidity.

8. The precision injection molding method for fiber-reinforced propellers based on multi-state compensation according to claim 5, characterized in that: The third stage specifically involves using progressively decreasing pressure to focus on controlling fiber stability and reducing orientation internal stress in thin-walled areas such as blade edges and hub end faces, thereby reducing warping.

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