Injection molding system and local light-transmitting product molding method

Abstract

The invention discloses an injection molding system and a local light-transmitting product forming method, and relates to the technical field of injection molding, and the injection molding system comprises an injection mold which comprises a mold cavity, a mold core, a driving device, a first pouring system and a second pouring system; the first injection unit is connected with the first pouring system; the second injection unit is connected with the second pouring system; the position sensor is used for detecting the position of the mold core; the control system is configured to control the first injection unit and the second injection unit to inject materials according to a time sequence; and after the second injection unit completes injection, closed-loop control is performed on the driving device based on a mold core position signal detected by the position sensor and a preset mold core speed curve so as to drive the mold core to compress the melt in the mold cavity. The problems of internal density difference and microdefects caused by poor melt flowability and uneven cooling can be solved, the light transmission uniformity and optical performance of the product are improved, and the appearance quality and stability of the local light transmission product are guaranteed.

Description

Technical Field

[0001] This application relates to the field of injection molding technology, specifically to an injection molding system and a method for molding partially translucent products. Background Technology

[0002] With consumers increasingly demanding personalized vehicle appearances, translucent bumpers have become a new trend in vehicle exterior design. To produce such products, one existing technology involves using a drive device (such as a hydraulic cylinder) to drive the mold core, injection molding the opaque body and the translucent body in stages within a single mold. While this approach reduces costs, the core movement is largely controlled by simple open-loop mechanisms, and after the second injection, it relies solely on natural cooling and pressure holding, lacking active intervention in the melt. This results in poor flowability and uneven cooling of the transparent plastic material after filling, leading to internal density differences and microscopic defects. Macroscopically, this manifests as uneven light transmission and stress marks, severely impacting the product's optical performance and appearance quality. Summary of the Invention

[0003] In view of the above, the purpose of this application is to provide an injection molding system and a method for molding partially translucent products to solve at least one of the above technical problems.

[0004] In a first aspect, this application provides an injection molding system, comprising: an injection mold, the injection mold including a cavity and a core for molding a product, a drive device for driving the core to move, and a first gating system and a second gating system that are connected to and independent of the cavity; a first injection unit connected to the first gating system; a second injection unit connected to the second gating system; a position sensor for detecting the position of the core; and a control system, the control system being signal-connected to the drive device, the first injection unit, the second injection unit, and the position sensor, the control system being configured to: control the first injection unit to inject a first material into the cavity; after the first injection unit completes injection, control the drive device to drive the core to retract, so as to form a space in the cavity for filling with a second material, and control the second injection unit to inject the second material into the cavity; and after the second injection unit completes injection, perform closed-loop control on the drive device based on the core position signal detected by the position sensor and a preset core speed curve, so as to drive the core to compress the melt in the cavity; wherein the preset core speed curve is configured to make the melt flow uniformly in the cavity and reach a preset target thickness.

[0005] In conjunction with the first aspect, in some optional embodiments, the control system is further configured to: calculate and set the injection stroke of the second injection unit based on the preset volume of the molding area of ​​the second material before controlling the second injection unit to inject the second material into the cavity.

[0006] In conjunction with the first aspect, in some alternative embodiments, the control system is further configured to: control the second injection unit to inject the second material at a predetermined temperature, the predetermined temperature being sufficient to remelt the surface of the first material, so as to achieve fusion bonding between the first material and the second material.

[0007] In conjunction with the first aspect, in some alternative implementations, the drive device is a servo electric cylinder.

[0008] In conjunction with the first aspect, in some optional implementations, the preset core speed curve is constructed in segments based on the change of melt viscosity over time and the stroke of the core.

[0009] In conjunction with the first aspect, in some optional embodiments, the preset core speed curve includes an initial section, a compression section, and a holding section connected in sequence. The initial section is configured to ensure that the melt fills the cavity and fully removes air bubbles. The compression section is configured to perform main compression on the melt and make the melt flow uniformly. The holding section is configured to achieve a dense arrangement of the molecular chains of the melt.

[0010] Secondly, this application provides a method for molding a partially translucent product, including the injection molding system in any of the embodiments of the first aspect described above. The method includes: controlling a first injection unit to inject a first material into the cavity of an injection mold to form the base portion of the product; after the first injection unit completes injection, controlling a driving device of the injection mold to drive the core backward to form a space in the cavity for filling with a second material; controlling a second injection unit to inject a second material into the cavity to fill the space and form a partially translucent portion of the product; after the second injection unit completes injection, performing closed-loop control on the driving device based on the core position signal detected by a position sensor and a preset core speed curve to drive the core to compress the melt in the cavity; wherein the preset core speed curve is configured to make the melt flow uniformly in the cavity and reach a preset target thickness.

[0011] In conjunction with the second aspect, in some optional embodiments, before controlling the second injection unit to inject the second material into the cavity, the method further includes: calculating and setting the injection stroke of the second injection unit based on the preset volume of the second material forming area.

[0012] In conjunction with the second aspect, in some alternative embodiments, in the step of controlling the second injection unit to inject the second material into the cavity, the second material is injected at a predetermined temperature sufficient to remelt the surface of the first material, so as to achieve fusion bonding between the first material and the second material.

[0013] In conjunction with the second aspect, in some optional implementations, the preset core speed curve is constructed in segments based on the change of melt viscosity over time and the stroke of the core.

[0014] Based on the above technical solutions, the injection molding system and the method for molding partially translucent products provided in this application achieve precise control of the core movement by introducing a position sensor into the injection mold and closed-loop control of the drive device. By actively compressing the melt through a preset core speed curve, the internal density difference and micro-defects caused by poor melt flow and uneven cooling are effectively solved. This eliminates macroscopic defects such as uneven light transmission and stress marks in the product, thereby significantly improving the uniformity of light transmission and optical performance of the product, ensuring the appearance quality and stability of partially translucent products, and can be used in the production and manufacturing of large partially translucent parts for vehicles. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of this application, 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 this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the structure of the base portion of an in-cavity molded product in an injection molding system provided in an embodiment of this application.

[0017] Figure 2 This is a schematic diagram of the structure of a core in an injection molding system that retracts under the drive of a driving device, as provided in an embodiment of this application.

[0018] Figure 3 This is a schematic diagram of the structure of a partially light-transmitting portion of a product formed inside a cavity in an injection molding system, as provided in an embodiment of this application.

[0019] Figure 4 This is a schematic flowchart of a partially translucent product forming method provided in an embodiment of this application.

[0020] Reference numerals: 100, Injection molding system; 10, Injection mold; 11, Cavity; 12, Core; 13, Drive device; 14, First gating system; 15, Second gating system; 20, First injection unit; 21, First feeding port; 30, Second injection unit; 31, Second feeding port; 1, Substrate portion; 2, Second material forming area; 3, Partially translucent portion. Detailed Implementation

[0021] The specific embodiments of this application will now be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely a part of the embodiments of this application, and not all of them. Based on the description of this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0022] In the description of this application, unless otherwise expressly specified and limited, the terms "connection," "setup," "installation," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0023] The terms “upper,” “lower,” “left,” “right,” “front,” “back,” “center,” “top,” “bottom,” “inner,” “outer,” “vertical,” “horizontal,” “clockwise,” “counterclockwise,” “axial,” “radial,” and “circumferential” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. They are used only for the convenience of description and simplification, and do not indicate or imply that the device or element 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.

[0024] The terms “first,” “second,” “third,” etc., are used only to distinguish elements with similar properties, and do not indicate or imply relative importance or a specific order, unless otherwise explicitly stated or limited.

[0025] The terms “comprising,” “including,” “having,” or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase “comprising one…” does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0026] The term "multiple" means two or more (including two).

[0027] The term "and / or" describes the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three cases: A exists alone, A and B exist simultaneously, and B exists alone.

[0028] The terms "an embodiment," "as an example," and "in one implementation" refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which may be included in at least one embodiment or example of this application. These illustrative expressions do not necessarily refer to the same embodiment, nor are they independent or alternative embodiments mutually exclusive with other embodiments. Where there is no conflict, the embodiments and features described in these embodiments can be combined in a suitable manner.

[0029] like Figures 1 to 3 As shown in the figure, this application embodiment provides an injection molding system 100. This injection molding system 100 adopts an integrated architecture of dual independent injection units, a movable core, and closed-loop compression control, for manufacturing plastic products composed of two materials through sequential injection and dynamic compression. Specifically, the injection molding system 100 includes an injection mold 10, a first injection unit 20, a second injection unit 30, a position sensor (not shown in the figure), and a control system (not shown in the figure). The details of each part are described below.

[0030] The injection mold 10 includes a cavity 11, a core 12, a drive device 13, a first gating system 14, and a second gating system 15. The cavity 11 forms the outer contour of the product. The core 12 is located inside the cavity 11, and its position is adjustable under the drive device 13. The first gating system 14 and the second gating system 15 are independently connected to different areas of the cavity 11 to form different parts of the product.

[0031] The first injection unit 20 is connected to the first inlet of the first gating system 14 and is used to inject a first material into the cavity 11. The second injection unit 30 is connected to the second inlet of the second gating system 15 and is used to inject a second material into the cavity 11. The first injection unit 20 and the second injection unit 30 can be any injection unit in the prior art that includes a barrel, nozzle, screw and power unit.

[0032] The drive device 13 is connected to the core 12 and is used to drive the core 12 to move. In this embodiment, the drive device 13 is a servo electric cylinder.

[0033] A position sensor is used to detect the position of the core 12. The position sensor can be directly mounted on the core 12 or a moving part rigidly connected to the core 12. The position sensor can be a linear encoder or a magnetic encoder. It can directly and in real time measure the position of the core 12 and convert it into a signal that is fed back to the control system. The control system then uses a PID (Proportional-Integral-Derivative) algorithm to calculate the deviation between the measured position and the target position and outputs an adjustment command to the drive device 13 to dynamically correct the position error of the core 12.

[0034] The control system is signal-connected to the drive device 13, the first injection unit 20, the second injection unit 30, and the position sensor. The control system is configured to: control the first injection unit 20 to inject a first material into the cavity 11; after the first injection unit 20 completes injection, control the drive device 13 to drive the core 12 backward to form a space for filling the second material in the cavity 11, and control the second injection unit 30 to inject the second material into the cavity 11; and after the second injection unit 30 completes injection, based on the position signal of the core 12 detected by the position sensor and the preset core speed curve, perform closed-loop control on the drive device 13 to drive the core 12 to compress the melt in the cavity 11.

[0035] Among them, such as Figure 1 As shown, the initial position of the core 12 corresponds to the space within the cavity 11 that only accommodates the first material. After the first material is injected, it can form the base portion 1 of the product. Once the first material has been injected and cooled to set, as... Figure 2 As shown, the core 12 retracts under the drive of the drive device 13, thereby expanding a new volume space, namely the second material forming area 2, on the basis of the original molding, for filling the second material. After the second material is injected, the core 12 advances again under the drive of the drive device 13, applying pressure to the unsolidified melt, promoting dense molecular arrangement and achieving precise thickness control, ultimately forming as shown. Figure 3 The product shown is partially translucent.

[0036] Furthermore, the control system is configured to: before controlling the second injection unit 30 to inject the second material into the cavity 11, calculate and set the injection stroke of the second injection unit 30 based on the preset volume of the second material molding area 2. The injection stroke L of the second injection unit 30 can be calculated according to formula (1), with the unit being mm: (1) in, This represents the actual volume of the second material forming area 2, in cm³, which can be measured using a three-dimensional model. This indicates the density of the second material in its solid state, expressed in g / cm³. This indicates the density of the second material in its molten state. and All were obtained through experiments or material handbooks; This indicates the cross-sectional area of ​​the injection screw, in mm². This represents the correction factor under injection pressure, which comprehensively considers the effect of pressure on melt density and barrel residue. It is calculated by comparing the actual weight of the injected material with the theoretical weight of the barrel. The specific calculation formula is as follows: .

[0037] The control system is also configured to control the second injection unit 30 to inject the second material at a predetermined temperature, which is sufficient to remelt the surface of the first material, thereby achieving a molten bond between the first and second materials. For example, the temperature of the second material injected by the second injection unit 30 upon entering the cavity 11 can be above 200°C, ensuring that upon contact with the substrate portion 1 solidified from the first material, it can melt the surface of the substrate portion 1, thereby causing the melted first and second materials to moltenly bond together, and subsequently be compressed together under the action of the core 12.

[0038] The preset core velocity curve aims to ensure that the melt flows uniformly within the cavity 11 and reaches the preset target thickness. Its construction is based on the change in melt viscosity over time and the actual stroke of the core 12, and is divided into three continuous stages: the initial stage, the compression stage, and the holding stage. The initial stage primarily ensures that the melt fills the cavity 11 and removes entrained air bubbles through slow advancement, preventing defect formation. The compression stage, as the main compression stage, dynamically adjusts the core 12 speed in response to changes in melt viscosity, ensuring uniform melt flow under pressure. During this process, the molecular chains undergo compression, shearing, and stretching, gradually becoming densely packed, while maintaining a uniform distribution of the internal pressure field, which helps improve subsequent elastic recovery capability. The holding stage further consolidates and ensures the dense packing of the melt's molecular chains, suppressing shrinkage and deformation, ultimately achieving a high degree of uniformity in melt density within the second material forming region 2.

[0039] Regarding the core speed curve, as an example, with a total compression stroke H=5mm, the core speed curve is constructed in three segments. The initial segment is 0 ≤ s < 1, the compression segment is 1 ≤ s ≤ 4, and the holding segment is 4 < s ≤ 5, all in mm. Here, s represents the core compression stroke in mm, and t represents the core compression time in seconds. The preset core speed curve is shown below. It can be expressed as equation (2):

[0040] in, This indicates the initial core velocity, in mm / s; This represents the initial (i.e., when s=0) melt viscosity, in Pa·s. This represents the real-time viscosity of the melt at time t, in Pa·s. This indicates the core velocity in the compression section, expressed in mm / s. This represents the real-time pressure gradient in the compression section as the core travels, expressed in MPa / mm. This represents the pressure gradient in the initial section as the core compression stroke changes, expressed in MPa / mm. Indicates the velocity smoothing coefficient of the compression section; This indicates the core speed in the pressure holding section, in mm / s. This indicates the maximum viscosity of the melt in the pressure holding section, expressed in Pa·s.

[0041] like Figure 4 As shown in the embodiment of this application, a method for molding a partially translucent product is also provided. This method uses the injection molding system 100 described above and includes: S101. Control the first injection unit 20 to inject the first material into the cavity 11 of the injection mold 10 to form the base part 1 of the product.

[0042] In this embodiment, the first material is colored plastic. The specific process of this step is as follows: the first injection unit 20 is started, and the colored plastic particles are fed into the barrel from the first feeding port 21 of the first injection unit 20; under the action of the heating device and the screw shearing, the colored plastic particles are gradually melted into a homogeneous melt; as the screw advances, the melt is injected into the cavity 11 through the first gating system 14 at a set pressure, and is rapidly cooled and shaped under the action of the low temperature wall of the mold to form the base part 1 of the product, that is, the non-transparent area; after the injection is completed, the pressure can be maintained for a certain period of time to prevent shrinkage and deformation, and then the next stage is entered.

[0043] S102. After the first injection unit 20 completes the injection, the driving device 13 controls the injection mold 10 to drive the core 12 to retract, so as to form a space in the cavity 11 for filling with the second material.

[0044] In this step, after the first injection unit 20 completes injection, or more precisely, after the first material has solidified, the control system issues a command to activate the servo electric cylinder to drive the core 12 to retreat axially. The retreat distance is preset according to the target volume of the light-transmitting part, typically 3mm-8mm. After the retreat action is completed, a cavity is formed in the cavity 11 that fits tightly against the original substrate, specifically for accommodating the second material.

[0045] S103, control the second injection unit 30 to inject the second material into the cavity 11 to fill the space and form a partially translucent part 3 of the product.

[0046] In this embodiment, the second material is translucent plastic. The specific process of this step is as follows: the second injection unit 30 is started, and translucent plastic particles (such as high-transparency polypropylene) are fed into the barrel from the second feeding port 31 of the second injection unit 30; under the action of the heating device and the screw shearing, the translucent plastic particles gradually melt into a homogeneous melt; as the screw advances, the melt is injected into the space formed by the retraction of the core 12 through the second gating system 15 at a set pressure and a set temperature; when the translucent plastic melt comes into contact with the surface of the solidified colored plastic, it melts the surface layer and achieves fusion bonding between the two under the action of injection pressure.

[0047] Before the second injection unit 30 injects the second material into the cavity 11, the injection stroke of the second injection unit 30 needs to be calculated and set according to the preset volume of the second material forming area 2. This part is explained in the relevant content of the injection molding system 100, and will not be repeated here.

[0048] S104. After the second injection unit 30 completes the injection, the drive device 13 is controlled in a closed loop based on the position signal of the core 12 detected by the position sensor and the preset core speed curve, so as to drive the core 12 to compress the melt in the cavity 11.

[0049] For details on the closed-loop control of the drive device 13 and the preset core speed curve, please refer to the relevant content in the injection molding system 100, which will not be repeated here.

[0050] After the above injection and compression are completed, the product can be demolded to obtain a partially translucent product, which can then proceed to subsequent processing steps, including but not limited to: flame treatment of the product surface, spraying of transparent primer, spraying of surface varnish, baking and curing, etc.

[0051] In summary, the injection molding system and the method for molding partially translucent products provided in this application, by introducing a position sensor into the injection mold and implementing closed-loop control of the drive device, achieve precise control of the core movement. By actively compressing the melt through a preset core speed curve, the system effectively solves the problems of internal density differences and microscopic defects caused by poor melt flowability and uneven cooling. This eliminates macroscopic defects such as uneven light transmission and stress marks in the product, thereby significantly improving the uniformity of light transmission and optical performance of the product. It ensures the appearance quality and stability of partially translucent products and can be used in the production of large partially translucent vehicle components.

[0052] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope disclosed in this application, and these should all be included within the scope of protection of this application.

Claims

1. An injection molding system, characterized in that, include: The injection mold includes a cavity and a core for molding a product, a drive device for moving the core, and a first gating system and a second gating system that are connected to and independent of the cavity. The first injection unit is connected to the first gating system; The second injection unit is connected to the second gating system; A position sensor is used to detect the position of the core; A control system is connected to the drive device, the first injection unit, the second injection unit, and the position sensor. The control system is configured to: control the first injection unit to inject a first material into the cavity; after the first injection unit completes injection, control the drive device to drive the core backward to form a space for filling a second material in the cavity; control the second injection unit to inject the second material into the cavity; and after the second injection unit completes injection, perform closed-loop control on the drive device based on the core position signal detected by the position sensor and a preset core speed curve to drive the core to compress the melt in the cavity. The preset core speed curve is configured to make the melt flow uniformly in the cavity and reach the preset target thickness.

2. The injection molding system according to claim 1, characterized in that, The control system is further configured to: before controlling the second injection unit to inject the second material into the cavity, calculate and set the injection stroke of the second injection unit based on the preset volume of the molding area of ​​the second material.

3. The injection molding system according to claim 1, characterized in that, The control system is further configured to: control the second injection unit to inject the second material at a predetermined temperature, the predetermined temperature being sufficient to remelt the surface of the first material, so as to achieve a molten bond between the first material and the second material.

4. The injection molding system according to claim 1, characterized in that, The drive device is a servo electric cylinder.

5. The injection molding system according to claim 1, characterized in that, The preset core speed curve is constructed based on the change law of melt viscosity over time and the stroke of the core in segments.

6. The injection molding system according to claim 5, characterized in that, The preset core speed curve includes an initial section, a compression section, and a holding section connected in sequence. The initial section is configured to ensure that the melt fills the cavity and fully removes air bubbles. The compression section is configured to perform main compression on the melt and make the melt flow uniformly. The holding section is configured to achieve dense arrangement of the molecular chains of the melt.

7. A method for molding a partially translucent product, characterized in that, The method, employing the injection molding system as described in any one of claims 1-6, comprises: The first injection unit is controlled to inject the first material into the cavity of the injection mold to form the base part of the product; After the first injection unit completes the injection, the driving device that controls the injection mold drives the core to retract, so as to form a space in the cavity for filling with the second material. The second injection unit is controlled to inject a second material into the cavity to fill the space and form a partially translucent portion of the product; After the second injection unit completes the injection, the driving device is controlled in a closed loop based on the core position signal detected by the position sensor and the preset core speed curve, so as to drive the core to compress the melt in the cavity. The preset core speed curve is configured to make the melt flow uniformly in the cavity and reach the preset target thickness.

8. The method for forming a partially translucent product according to claim 7, characterized in that, Before the second injection unit injects the second material into the cavity, the method further includes: The injection stroke of the second injection unit is calculated and set according to the preset volume of the second material forming area.

9. The method for forming a partially translucent product according to claim 7, characterized in that, In the step of controlling the second injection unit to inject the second material into the cavity, the second material is injected at a predetermined temperature sufficient to remelt the surface of the first material, so as to achieve molten bonding between the first material and the second material.

10. The method for forming a partially translucent product according to claim 7, characterized in that, The preset core speed curve is constructed based on the change law of melt viscosity over time and the stroke of the core in segments.

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