CN-122008512-A - Self-adaptive control method for carbon fiber long fiber injection molding

CN122008512ACN 122008512 ACN122008512 ACN 122008512ACN-122008512-A

Abstract

The application relates to a carbon fiber long fiber injection self-adaptive control method which comprises the steps of applying pretension to carbon fibers in a die cavity after an injection die is closed, monitoring melt pressure and a melt front position in real time in a filling process, adjusting carbon fiber tension in real time by using a rheological-tension coupling model based on the melt pressure to offset flow drag force, and controlling an auxiliary supporting unit to controllably withdraw before melt contact based on the melt front position. The application has the advantages of being capable of dynamically adapting to the melt rheological state, effectively preventing carbon fiber from displacement and sagging, simultaneously avoiding welding marks generated by a fixed supporting structure and remarkably improving the mechanical property of the composite material product.

Inventors

WANG KUN
ZHU XINAI
Fang Peixi

Assignees

湖南徕木科技有限公司

Dates

Publication Date: 20260512
Application Date: 20260226

Claims (9)

1. The self-adaptive control method for the carbon fiber long fiber injection molding is characterized by comprising the following steps of: S1, after an injection mold is closed, sending a command to a tension adjusting system, and applying pretension to carbon fibers in a mold cavity to enable the carbon fibers to be kept in a tensioned and neutral space posture in the mold cavity; S2, acquiring rheological state parameters of the melt in the die cavity in real time based on a rheological state monitoring unit in the injection filling process, wherein the rheological state parameters at least comprise real-time pressure values of the melt and front position information of the melt; S3, calculating a target tension value required by counteracting the flow drag force of the melt at the current moment by utilizing a preset rheological-tension coupling model based on the obtained real-time pressure value, and adjusting the output tension of a tension adjusting system in real time, so that the tension on the carbon fiber is adjusted in real time along with the change of the real-time pressure value of the melt, and the position stability of the carbon fiber in the injection filling process is maintained; s4, judging whether the melt front reaches a preset trigger threshold of the auxiliary supporting unit or not based on the obtained melt front position information, and generating an avoidance control instruction when judging that the trigger condition is met, and driving the auxiliary supporting unit to controllably withdraw from the die cavity before the melt contacts.
2. The method according to claim 1, wherein the tension adjusting system comprises a damping brake mechanism arranged at the feeding end of the injection mold and/or a servo traction mechanism arranged at the discharging end of the injection mold, and is used for applying adjustable axial tension to the carbon fibers passing through the mold cavity; the auxiliary supporting unit comprises at least one group of telescopic pin bodies arranged on the side wall of the die cavity and used for extending before the melt front contacts the auxiliary supporting unit so as to support the carbon fiber to keep the carbon fiber in the neutral layer and retracting into the side wall of the die cavity after receiving the avoidance control instruction.
3. The method according to claim 2, wherein in step S3, the rheological-tensile coupling model is configured to establish a positive correlation mapping between a real-time pressure value and a target tension value; when the rise of the real-time pressure value of the melt is monitored, the control system instructs the tension adjusting system to increase the output tension so as to resist the enhanced flow drag force; when the fluctuation amplitude of the real-time pressure value of the melt is monitored to be lower than a preset range, the control system instructs the tension adjusting system to maintain constant tension.
4. The method according to claim 3, wherein the preset trigger threshold is set based on a time point or a spatial coordinate at which the melt front reaches the position of the auxiliary supporting unit; The controlled withdrawal is configured to control the auxiliary support unit to retract fully into the cavity sidewall within a predetermined safety margin before the melt front reaches the auxiliary support unit position, to fill the space left by the auxiliary support unit with melt flowing subsequently, and to increase tension compensation to maintain the attitude based on S3 while the auxiliary support unit is withdrawn.
5. The method for adaptively controlling injection molding of carbon fiber long fibers according to claim 1, further comprising: S5, when the injection filling process is monitored to enter a pressure maintaining stage, the control system switches a tension control strategy, and the tension value applied to the carbon fiber is gradually reduced according to a preset stress release curve until the melt is completely solidified, so that the residual stress in the injection molded product is eliminated.
6. The method according to claim 1, wherein in step S1, the pre-tension set value is configured to be larger than the drop force caused by the gravity of the carbon fiber and smaller than the yield strength of the carbon fiber material, and the control system eliminates the suspension deformation of the carbon fiber in the mold cavity before the injection is started through closed loop feedback adjustment.
7. The method for adaptively controlling injection molding of carbon fiber long fibers according to claim 1, further comprising: S6, before entering the next injection molding cycle after injection molding is completed, the control system executes periodic reset logic: s61, controlling a non-return clamping mechanism positioned at the upstream of the die to be closed, and locking the end position of a new section of carbon fiber; S62, driving a shearing mechanism in the runner to act, and cutting off the connection between the injection molding product and the unshaped carbon fiber; s63, after the die is opened, a new section of carbon fiber is pulled into the die cavity through a tension adjusting system.
8. The method of claim 4, wherein the act of controlled withdrawal further comprises a secondary pressure compensation logic: After the auxiliary supporting unit is withdrawn, if the pressure drop at the withdrawn position of the auxiliary supporting unit is detected, the injection molding machine is instructed to execute the instantaneous pressure compensation action so as to compact the partial cavity formed after the withdrawal of the auxiliary supporting unit.
9. The method for adaptively controlling injection molding of carbon fiber long fibers according to claim 1, wherein the rheological state monitoring unit comprises a pressure sensor or a temperature sensor array arranged in a mold cavity, and the position information of the melt front is obtained by analyzing signal abrupt timing calculation of the sensor array.

Description

Self-adaptive control method for carbon fiber long fiber injection molding Technical Field The application relates to the field of injection molding processing, in particular to a self-adaptive control method for carbon fiber long fiber injection molding. Background The carbon fiber long fiber reinforced thermoplastic composite material has wide application in the fields of automobile manufacture, aerospace and high-end electronic equipment shell manufacture due to the excellent specific strength and specific modulus. In the injection molding process for such materials, the spatial distribution state of the long fibers or continuous fibers in the mold cavity directly determines the mechanical properties and structural stability of the final molded product. In order to achieve the desired mechanical reinforcement, it is generally desirable in the art that the carbon fibers remain stably positioned in the neutral layer of the article cross-section to ensure that the article is uniformly stressed when subjected to bending or stretching loads. However, in actual injection filling processes, achieving this goal faces a number of process challenges. The injection of thermoplastic in the molten state into the mold cavity at a relatively high velocity and pressure can create significant flow drag and impact forces on the carbon fibers pre-positioned within the mold cavity. The traditional control method usually adopts constant pretightening force to fix the carbon fiber, and the static control strategy is difficult to cope with complex and changeable rheological environments in the injection molding process. When the melt filling pressure is increased along with the increase of the flow resistance, if the tension applied to the carbon fibers cannot be synchronously adjusted, the increased melt flow drag force easily causes the carbon fibers to displace, bend and even be flushed to the wall surface of the mold, thereby causing defects of uneven fiber distribution or reinforcement failure of the finished product. On the other hand, in order to prevent the carbon fiber from sagging due to its own weight over a long span, the prior art generally provides a fixed supporting pin or a positioning structure inside the mold. Although these fixing structures can solve the problem of fiber positioning in the early stage of injection molding, they introduce new potential hazards in the melt filling stage. The fixed support structure can impede the continuous flow of the melt, easily creating weld marks or air pockets behind the support points, compromising the structural continuity and appearance quality of the article. Some of the improved techniques have attempted to use a timed telescoping mechanism, but due to the lack of real-time monitoring of the actual arrival position of the melt front in the mold cavity, the support mechanism often relies on empirically set times to actuate. If the withdrawal is too early, the carbon fibers lose support and deform before the melt arrives, and if the withdrawal is too late, the flow of the melt is blocked or the carbon fibers interfere with the melt. Disclosure of Invention The application provides a carbon fiber long fiber injection self-adaptive control method, which aims to automatically adjust fiber tension according to real-time pressure change of a melt and accurately control an auxiliary supporting unit to avoid according to the actual position of a melt front. In a first aspect, the application provides a carbon fiber long fiber injection molding self-adaptive control method, which adopts the following technical scheme: an adaptive control method for carbon fiber long fiber injection molding is used for injection molding equipment comprising an injection molding machine and a control system, and comprises the following steps: S1, after an injection mold is closed, sending a command to a tension adjusting system, and applying pretension to carbon fibers in a mold cavity to enable the carbon fibers to be kept in a tensioned and neutral space posture in the mold cavity; S2, acquiring rheological state parameters of the melt in the die cavity in real time based on a rheological state monitoring unit in the injection filling process, wherein the rheological state parameters at least comprise real-time pressure values of the melt and front position information of the melt; S3, calculating a target tension value required by counteracting the flow drag force of the melt at the current moment by utilizing a preset rheological-tension coupling model based on the obtained real-time pressure value, and adjusting the output tension of a tension adjusting system in real time, so that the tension on the carbon fiber is adjusted in real time along with the change of the real-time pressure value of the melt, and the position stability of the carbon fiber in the injection filling process is maintained; s4, judging whether the melt front reaches a preset trigger threshold of the auxiliary suppor