A molding system for automotive plastic grilles

Abstract

This invention relates to the field of plastic molding technology, specifically to an automotive plastic grille molding system. It includes an injection molding machine, a mold module connected to the injection molding machine's outlet, and a stress testing module. The mold module includes a fixed mold and a moving mold, and both the fixed mold and the moving mold have two symmetrically arranged cooling water channels on their sides near the cavity. The automotive plastic grille molding system of this invention significantly improves the consistency of cooling efficiency during the cooling and curing stage of the finished automotive plastic grille by providing two symmetrically arranged cooling water channels on the sides of both the fixed mold and the moving mold near the cavity. Furthermore, the system adjusts the operating parameters of the two symmetrical water channels by periodically sampling and checking the elastic distribution on the left and right sides of some finished automotive grilles, thereby making the cooling efficiency of the two symmetrically arranged cooling water channels as consistent as possible, and thus ensuring the symmetry of the elastic distribution on the left and right sides of the finished automotive plastic grille.

Description

Technical Field

[0001] This invention relates to the field of plastic molding technology, and more specifically, to an automotive plastic grille molding system. Background Technology

[0002] Plastic injection molding is the core process in the manufacture of automotive plastic grilles. Essentially, it is a phase transition and structural forming process in which a material transforms from a high-temperature molten plastic state to a solid state. This process, especially the cooling and solidification stage, directly determines the final arrangement, orientation, crystallization (for semi-crystalline materials), and internal stress distribution of the polymer chains. These microstructures together constitute the macroscopic mechanical properties of the product.

[0003] For elongated, thin-walled plastic parts like automotive grilles that require high assembly symmetry, the consistency of mechanical properties on both sides is crucial. In existing technologies, mold cooling is typically treated as a simple heat exchange process, achieved by opening a single cooling water path in the stationary and moving molds, thus neglecting the impact of consistent cooling efficiency on the plastic product. Summary of the Invention

[0004] The purpose of this invention is to provide an automotive plastic grille molding system to improve the above-mentioned technical problems.

[0005] To achieve the above objectives, the embodiments of this application provide the following technical solutions:

[0006] This application provides an automotive plastic grille molding system, including: an injection molding machine and a mold module connected to the discharge port of the injection molding machine. The mold module includes a fixed mold and a moving mold. Both the fixed mold and the moving mold have two symmetrically arranged cooling water channels on the side near the cavity. A stress testing module is used to detect the stress parameters of the finished automotive grille at two preset left and right points within a preset deformation amount. If the stress parameters at the left and right points are abnormal, the operating parameters of the cooling water channels in the fixed mold and the moving mold are adjusted based on the multi-point stress parameters, thereby improving the elastic distribution symmetry of the left and right sides of the finished automotive grille.

[0007] Optionally, the fixed mold and the moving mold are provided with a constant temperature oil circuit, which is connected to an external mold temperature controller to maintain the fixed mold and the moving mold at a preset constant temperature before injection molding. The preset constant temperature is 80℃-120℃. The cooling water circuits of the fixed mold and the moving mold on the same side share a cooling system. The stress testing module includes a fixing unit for fixing the middle part of the finished car grille and stress testing push rods respectively located at both ends of the fixed finished car grille. The top of the push rod is provided with a pressure sensor.

[0008] Optionally, adjusting the operating parameters of the cooling water circuits in the fixed mold and moving mold based on multi-point force parameters includes:

[0009] Periodically obtain the multi-point stress parameters corresponding to this batch of test samples. The stress parameters include the deformation pressure value on the left side and the deformation pressure value on the right side. The deformation pressure value on the left side represents the deformation pressure from the middle of the finished car grille to the left end.

[0010] If the first difference between the deformation pressure value on the left and the deformation pressure value on the right is greater than the threshold, calculate the average value of the deformation pressure value on the left and the deformation pressure value on the right, and record it as the average deformation pressure value.

[0011] If the average deformation pressure is greater than the standard threshold range, the pressure difference between the larger of the two deformation pressure values ​​on the left and right sides and the average deformation pressure is calculated, and the pressure difference is increased based on a preset amplification factor, so that the larger pressure value after correction is closer to the smaller pressure value.

[0012] The cooling water circuit control parameters on the corresponding side are adjusted based on the increased pressure difference. The control parameters include the inlet temperature of the cooling water circuit and the supply pressure of the cooling water circuit.

[0013] Optionally, the cooling water circuit control parameters on the corresponding side are adjusted based on the increased pressure difference, including:

[0014] The target pressure value is calculated based on a larger pressure value and the increased pressure difference.

[0015] When the injection molding material is a semi-crystalline plastic, the cooling water circuit operating parameters corresponding to the target pressure value are retrieved from the corresponding operating parameter reference table based on the current injection molding material type. The operating parameters include the target inlet temperature of the cooling water circuit and the target supply pressure of the cooling water circuit.

[0016] Adjust the opening degree of the proportional valve for the corresponding cooling water circuit and the heat dissipation power of the coolant based on the difference between the current inlet temperature and cooling water supply pressure of the cooling water circuit and the target inlet temperature and target cooling water supply pressure.

[0017] The beneficial effects of this invention are as follows:

[0018] The automotive plastic grille molding system of this invention greatly improves the consistency of cooling efficiency during the cooling and curing stage of the finished automotive plastic grille by providing two symmetrically arranged cooling water channels on both the fixed mold and the moving mold near the cavity. Furthermore, the system adjusts the operating parameters of the two symmetrical water channels by periodically sampling and inspecting the elastic distribution on the left and right sides of some finished automotive grilles, thereby making the cooling efficiency of the two symmetrically arranged cooling water channels as consistent as possible, and thus ensuring the symmetry of the elastic distribution on the left and right sides of the finished automotive grille.

[0019] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing embodiments of the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of an automotive plastic grille molding system as described in an embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram showing the connection between the cooling water channels and the cooling system in the fixed mold and the moving mold as described in the embodiments of the present invention;

[0023] Figure 3 This is a simplified schematic diagram illustrating the operating principle of the stress testing module described in this embodiment of the invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0025] Example 1:

[0026] like Figure 1 - Figure 2 As shown, this embodiment provides an automotive plastic grille molding system, including: an injection molding machine and a mold module connected to the discharge port of the injection molding machine. The mold module includes a fixed mold and a moving mold, and both the fixed mold and the moving mold are provided with two symmetrically arranged cooling water channels on the side near the cavity.

[0027] Stress testing module, such as Figure 3As shown, it is used to detect the force parameters at two preset points on the left and right sides of the finished car grille within a preset deformation amount. When the force parameters at the left and right points are abnormal, the operating parameters of the cooling water circuit in the fixed mold and the moving mold are adjusted based on the multi-point force parameters, thereby improving the elastic distribution symmetry of the left and right sides of the finished car grille.

[0028] The fixed mold and the moving mold are equipped with a constant temperature oil circuit, which is connected to an external mold temperature controller to maintain a preset constant temperature of 80℃-120℃ before injection molding. The cooling water circuit of the fixed mold and the moving mold on the same side shares a cooling system. The stress testing module includes a fixing unit for fixing the middle part of the finished car grille and stress testing push rods respectively located at both ends of the finished car grille. The push rods are equipped with pressure sensors at the top.

[0029] Secondly, this embodiment also provides a specific implementation method for adjusting the operating parameters of the cooling water circuit in the fixed mold and the moving mold based on multi-point force parameters. The core of this control method is to make the cooling efficiency of the two symmetrically set cooling systems tend to be consistent when only the operating parameters of one cooling system are controlled.

[0030] Secondly, the reason why this embodiment does not directly restore the two cooling systems to their initial operating parameters is that the two cooling systems will have deviations in cooling efficiency during long-term operation and dynamic parameter adjustment. Even within the same cooling efficiency range, the corresponding cooling parameters are different (i.e., within the same cooling efficiency range, the inlet liquid temperature and inlet liquid rate of the two devices are different; the cooling efficiency of a lower inlet liquid temperature matched with a slower flow rate and a higher inlet liquid temperature matched with a faster flow rate may be very similar). If the initial operating parameters are restored rashly, the consistency of the cooling efficiency of the two symmetrically set cooling systems may be even worse.

[0031] If real-time monitoring and adjustment of operating parameters is adopted, frequent adjustments will occur, requiring the configuration of an additional independent controller to accurately ensure such adjustments, which has little economic value. On the production line, the corresponding initialization parameters are usually configured directly at startup, and adjustments are minimized as long as the preset high-risk operating parameter thresholds within the system are not triggered.

[0032] Secondly, due to multiple fine-tuning, although the cooling efficiency of the two cooling systems is not much different, the inlet temperature and flow rate may have formed a relatively obvious difference. However, as long as the cooling efficiency of the two cooling systems is not much different, it will not affect the operation of the entire automotive plastic grille molding system. That is, the core point of this embodiment is to ensure that the deformation pressure values ​​on both sides of the finished automotive plastic grille are not much different.

[0033] The specific implementation method for adjusting the operating parameters of the cooling water circuit in the fixed mold and the moving mold based on multi-point force parameters can be as follows:

[0034] Step S100: Periodically obtain the multi-point stress parameters corresponding to the batch of test samples. The stress parameters include the left deformation pressure value and the right deformation pressure value. The left deformation pressure value represents the deformation pressure from the middle of the finished car grille to the left end.

[0035] Step S200: If the first difference between the deformation pressure value on the left and the deformation pressure value on the right is greater than the threshold, calculate the average value of the deformation pressure value on the left and the deformation pressure value on the right, and record it as the average deformation pressure value. The first difference being greater than the threshold indicates that there is a large difference in the material properties on both sides of the finished car grille. Under normal injection molding and holding pressure, this is usually caused by the inconsistent cooling efficiency on both sides. Therefore, it is necessary to adjust the consistency of the cooling efficiency on both sides.

[0036] When there is a significant difference between the deformation pressure values ​​on the left and right sides, the usual approach is to move both values ​​closer to the average value. However, when both the left and right deformation pressure values ​​are significantly higher than the midpoint of the standard threshold range (in which case the average deformation pressure is greater than the upper limit of the standard threshold range), it is only necessary to adjust the value with the higher deformation pressure towards the value with the lower deformation pressure. Furthermore, the magnitude of this adjustment is greater than the previous adjustment towards the average value. Therefore, an amplification factor is introduced to increase this adjustment magnitude. The specific implementation method is as follows:

[0037] Step S300: If the average deformation pressure is greater than the upper limit of the standard threshold range, calculate the pressure difference between the larger of the two deformation pressure values ​​on the left and right sides and the average deformation pressure. Based on the difference between the average deformation pressure and the upper limit of the standard threshold range, find the corresponding preset amplification factor in the operating parameter comparison table to increase the pressure difference, thereby making the larger pressure value after correction closer to the smaller pressure value. Overall, the larger the average deformation pressure is compared to the upper limit of the standard threshold range, the larger the corresponding amplification factor will be.

[0038] Step S400: Adjust the cooling water circuit control parameters on the corresponding side based on the increased pressure difference. The control parameters include the inlet temperature of the cooling water circuit and the supply pressure of the cooling water circuit. Specifically, this can be implemented as follows:

[0039] Step S410: Calculate the target pressure value based on the larger pressure value and the increased pressure difference;

[0040] Step S420: When the injection molding material is a semi-crystalline plastic, the cooling water circuit condition parameters corresponding to the target pressure value are retrieved from the corresponding operating parameter reference table based on the current injection molding material type. The condition parameters include the target inlet temperature and the target cooling water supply pressure. The cooling water circuit condition parameters in the operating parameter reference table are the deformation pressure test values ​​corresponding to different cooling rates after ensuring sufficient pressure holding during the injection molding process. Specifically, under the condition of ensuring sufficient pressure holding, the pressure values ​​corresponding to the preset deformation of the automotive plastic grille products with different mechanical properties obtained by repeatedly adjusting different inlet rates and different initial inlet temperatures are obtained under the condition of preset deformation at a fixed test position.

[0041] Step S430: Adjust the opening degree of the inlet proportional valve of the corresponding cooling water circuit and the heat dissipation power of the coolant based on the difference between the current inlet temperature and cooling water supply pressure of the cooling water circuit and the target inlet temperature and target cooling water supply pressure.

[0042] For steps S410-S430, it should be noted that there are three main factors affecting the cooling efficiency of the cooling water circuit: inlet temperature, inlet flow rate, and cooling time. However, in terms of actual mold module control, usually only the inlet temperature and inlet flow rate are controlled. The cooling time is not adjusted because it involves the overall processing time and many other linkage parameters. The operating parameter reference table will record the various cooling water circuit operating parameters corresponding to different deformation pressures obtained from the experiment. In other words, within the same pressure range, there are multiple different temperatures and flow rates. The system will use a weighted algorithm to comprehensively evaluate the optimal solution among the corresponding multiple solutions. The inlet temperature and cooling water circuit supply pressure in the optimal solution are the target inlet temperature and target cooling water circuit supply pressure.

[0043] The system uses a weighted algorithm to comprehensively evaluate multiple solutions to determine the optimal solution. A specific implementation of this algorithm could be as follows:

[0044] Multiple inlet temperature and cooling water supply pressure allocation schemes corresponding to the target pressure value are retrieved. The difference between the inlet temperature and supply pressure value in each scheme and the current inlet temperature and supply pressure value is calculated. Based on the difference between the inlet temperature and supply pressure value, a weighted algorithm is used to evaluate the adjustment difficulty index, thereby obtaining the scheme that is easiest to adjust. The inlet temperature and supply pressure value in this scheme are marked as the target inlet temperature and target cooling water supply pressure value. The difficulty of temperature adjustment and flow rate adjustment are different, so a comprehensive weighted evaluation of the control difficulty is required.

[0045] Secondly, the theoretical feasibility of adjusting cooling parameters based on deformation pressure values ​​is based on the following:

[0046] Under the premise of sufficient pressure holding (ensuring the density of the injection molding material and compensating for shrinkage), the effect of different cooling rates (different injection temperatures and injection speeds) on the final flexural strength of the molded part is complex and varies depending on the material type, such as semi-crystalline and amorphous materials.

[0047] For semi-crystalline plastics (such as PP, PA, POM, and PBT), slow cooling (high mold temperature) allows sufficient time for the molecular chains to move and align, forming a highly crystalline and well-developed, coarse spherulitic structure. High crystallinity typically results in higher yield strength and elastic modulus, making it more difficult for parts to yield under bending loads, corresponding to greater deformation stress. However, the coarse spherulitic structure forms distinct grain boundaries, which are weak points. Under stress, cracks easily propagate along these grain boundaries, increasing the material's brittleness. Overall, while the flexural strength may be high, the plasticity is poor, and failure may manifest as sudden brittle fracture after reaching the yield point.

[0048] Rapid cooling (low mold temperature): The crystallization process is suppressed, leading to reduced crystallinity and the formation of fine, imperfect crystals or microcrystalline structures. Decreased crystallinity typically results in lower yield strength and elastic modulus, making parts more prone to yield deformation. However, the fine crystal structure also implies a more uniform material without obvious weak grain boundaries, resulting in better material toughness and the ability to absorb more energy. Overall, although the initial yield point may be lower (corresponding to lower deformation pressure within a preset small deformation range), its good toughness may lead to greater deflection during bending.

[0049] For amorphous plastics (such as PC, ABS, PS, PMMA), which do not have a crystallization process, the influencing mechanism is different.

[0050] Slow cooling allows the molecular chains more time to relax, resulting in tighter molecular packing, lower residual thermal stress, and a material closer to equilibrium with more uniform properties. It typically exhibits the material's inherent yield strength and toughness, and its bending properties are stable and predictable. Such materials can be slowly cooled but not rapidly.

[0051] Rapid cooling: The molecular chains are "frozen" in a non-equilibrium state, resulting in a large free volume. At the same time, it locks in higher orientation stress and thermal stress. In terms of the effect on resistance to bending strength, the modulus may decrease slightly, but the key effect is internal stress: the high residual internal stress will be superimposed on the external bending load, which will significantly reduce the actual ability of the part to withstand external load. The part may warp, silver streaks or even crack under loads far below the material yield strength, that is, the toughness may deteriorate - the molecular chains in the "frozen" tense state are more prone to brittle fracture.

[0052] In general, for amorphous plastics, slower cooling (higher mold temperatures) is usually more beneficial because it reduces harmful residual internal stresses, resulting in more uniform and closer-to-optimal material properties, thus achieving better and more stable flexural strength. Rapid cooling primarily introduces the risk of internal stresses rather than performance improvements.

[0053] It is evident that different types of materials respond to cooling rate in completely different ways. For semi-crystalline plastics, the overall trend is relatively strong, while for amorphous plastics, the impact of cooling rate is relatively small and the trend is weak. Therefore, the control method described in this embodiment is not applicable.

[0054] In this embodiment, the invention creatively introduces a stress testing module to directly perform quantitative mechanical symmetry testing on the finished grating, transforming the process variable of "cooling effect" into a directly measurable "product performance" result indicator. When an asymmetry deviation is detected to be out of tolerance, the system can automatically initiate a compensation program, forming a complete quality closed loop of "detection-judgment-adjustment." This fundamentally changes the traditional post-production inspection model, realizing proactive quality protection during the production process and greatly reducing the risk of batch defective products.

[0055] Secondly, the core of the control method described in this embodiment is not simply restoring equipment parameters, but rather calculating and executing the optimal adjustment scheme to bring the cooling efficiencies of both sides back to converge based on the actual state of the current system (reflected by the left and right force parameters). The system queries a pre-set "operating parameter comparison table" based on a large amount of process experimental data and uses a weighted algorithm to select the control path with the lowest execution difficulty, ensuring the accuracy, speed, and production stability of the adjustment. This "dynamic rebalancing" concept effectively overcomes the inevitable performance drift problem during long-term equipment operation.

[0056] Secondly, the control method described in this embodiment is specifically optimized for the process characteristics of semi-crystalline plastics. By establishing a database (operating parameter reference table) mapping the cooling parameters (inlet temperature, pressure) to the mechanical properties of the final product (deformation pressure value), the control has a solid materials science foundation. The system can precisely intervene based on the material's sensitivity to cooling rate, thereby broadening the process window and enhancing robustness to raw material fluctuations and changes in the production environment.

[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A molding system for automotive plastic grilles, characterized in that, include: An injection molding machine and a mold module connected to the discharge port of the injection molding machine, the mold module including a fixed mold and a moving mold, the fixed mold and the moving mold each having two symmetrically arranged cooling water channels on the side near the cavity; The stress testing module is used to detect the stress parameters at two preset points on the left and right sides of the finished car grille within a preset deformation amount. If the stress parameters at the two points on the left and right sides are abnormal, the operating parameters of the cooling water circuit in the fixed mold and the moving mold are adjusted based on the stress parameters at multiple points, thereby improving the elastic distribution symmetry of the left and right sides of the finished car grille. Among them, adjusting the operating parameters of the cooling water circuits in the fixed mold and the moving mold based on multi-point force parameters includes: Periodically obtain the multi-point stress parameters corresponding to this batch of test samples. The stress parameters include the deformation pressure value on the left side and the deformation pressure value on the right side. The deformation pressure value on the left side represents the deformation pressure from the middle of the finished car grille to the left end. If the first difference between the deformation pressure value on the left and the deformation pressure value on the right is greater than the threshold, calculate the average value of the deformation pressure value on the left and the deformation pressure value on the right, and record it as the average deformation pressure value. Then adjust the deformation pressure values ​​on both sides to make them closer to the average deformation pressure value. If the average deformation pressure is greater than the upper limit of the standard threshold range, the pressure difference between the larger of the two deformation pressure values ​​on the left and right sides and the average deformation pressure is calculated. Based on the difference between the average deformation pressure and the upper limit of the standard threshold range, the corresponding preset amplification factor is found in the operating parameter comparison table to increase the pressure difference, thereby making the larger pressure value after correction closer to the smaller pressure value. The cooling water circuit control parameters on the corresponding side are adjusted based on the increased pressure difference. The control parameters include the inlet temperature of the cooling water circuit and the supply pressure of the cooling water circuit. Among them, adjusting the cooling water circuit control parameters on the corresponding side based on the increased pressure difference includes: The target pressure value is calculated based on a larger pressure value and the increased pressure difference. When the injection molding material is a semi-crystalline plastic, the cooling water circuit operating parameters corresponding to the target pressure value are retrieved from the corresponding operating parameter reference table based on the current injection molding material type. Adjust the opening degree of the proportional valve for the corresponding cooling water circuit and the heat dissipation power of the coolant based on the difference between the current inlet temperature and cooling water supply pressure of the cooling water circuit and the target inlet temperature and target cooling water supply pressure.

2. The automotive plastic grille molding system according to claim 1, characterized in that, The fixed mold and the moving mold are equipped with a constant temperature oil circuit, which is connected to an external mold temperature controller to maintain the fixed mold and the moving mold at a preset constant temperature of 80℃-120℃ before injection molding. The cooling water circuit of the fixed mold and the moving mold on the same side shares a cooling system. The stress testing module includes a fixing unit for fixing the middle part of the finished car grille and stress testing push rods respectively located at both ends of the finished car grille. The push rods are equipped with pressure sensors at the top.

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