Injection molding demolding method for forming arc hook plastic part with arc shell-drawing type inner cavity

Abstract

The invention relates to the technical field of injection molding products and injection molds, in particular to an injection molding demolding method for forming an arc hook plastic part with an arc shell-pulling type inner cavity. A core-pulling type core part of an E-shaped structure and a rotary core-pulling mechanism formed by the core-pulling type core part, a pull rod and a connecting rod are adopted; the arc core-pulling part rotates around the rotating shaft to be separated from the inner cavity of the plastic part, and the problems that demolding cannot be achieved through traditional straight pulling and structure interference is caused are solved. The mold adopts a multi-mold-plate sequential mold opening mode, retreat of a core pulling piece is limited through a movable mold insert and a supporting block, a fixed mold sliding block is driven by means of a bent pin mechanism to give way, and reliable demolding of a sprue is achieved through a scraping plate in the ejection stage. The mold can form an arc cavity structure with uniform wall thickness, obviously improves the shrinkage and dent defects of a plastic part, and is suitable for multi-cavity mass production.

Description

Technical Field

[0001] This invention relates to the field of injection molded products and injection molds, and in particular to an injection molding demolding method for forming arc hook plastic parts with arc-shaped shell-type inner cavities. Background Technology

[0002] Hook-type plastic parts need to withstand tensile, impact, and repeated fatigue loads over long periods of daily use. Their structural shape directly affects the stress distribution, product strength, and safety. Traditional hooks are usually designed with right angles or sharp hook shapes. This type of structure not only creates significant stress concentration in the stress area, making it prone to cracking and breakage, but the sharp edges can also easily scratch users or damage the hung items during use. Furthermore, sharp-angled structures often result in defects such as weld lines, shrinkage, and poor filling during injection molding, limiting product appearance quality and production consistency.

[0003] Due to the aforementioned limitations, the industry has gradually begun to adopt rounded stress-bearing configurations to improve structural reliability. The first-generation rounded hook, with its optimized design, features a rounded edge and a horn-like shape, resulting in a smoother stress path and better adaptability to injection molding processes. However, when this structure was used in mass production, appearance defects such as shrinkage and dents appeared on the outer surface of the hook. This was due to insufficient internal hollowness; the hook failed to form an effective cavity along its outer contour, leading to excessive local wall thickness and uneven cooling and shrinkage.

[0004] To further improve the product's appearance and molding quality, the internal structure of the hook needs to be redesigned to create cavities arranged along an arc contour, and to connect the inner cavity of the main mounting part with the inner cavity of the hook, thus achieving a more uniform cooling path and wall thickness control. This resulted in the design of the second-generation arc hook. However, due to its complex internal arc surface and the fact that the center of the arc is close to the mold parting surface, conventional straight or angled pulling structures cannot achieve demolding, and may even interfere with other mold components. Therefore, a dedicated core-pulling mold structure is required that can achieve rotary core pulling, sequential displacement, avoidance of mold structures, and reliable reset function to successfully mold this type of plastic product. Summary of the Invention

[0005] The purpose of this invention is to provide an injection molding demolding method for forming arc hook plastic parts with arc-shaped shell-type inner cavities, addressing the shortcomings of existing technologies.

[0006] The present invention achieves the above-mentioned objective through the following technical solution: an injection molding demolding method for forming a plastic part with an arc-shaped hook having an arc-shaped shell-like inner cavity, comprising the following steps:

[0007] Pre-positioning step: After the mold is closed, the core-pulling part is restricted by the positioning component set on the moving mold side, so that the core-pulling part maintains its corresponding cavity forming position during the injection stage and avoids backward displacement under the action of injection pressure.

[0008] First mold opening clearance step: Drive the first template and the second template to separate along the mold parting direction, which is used to restrict the positioning component of the core-pulling part from being removed from the core-pulling part, and provide clearance space for the subsequent rotation of the core-pulling part;

[0009] The second mold opening and retraction step: continue to drive the fourth and fifth templates to separate, and use the bent pin mechanism between them to drive the fixed mold slider to retract away from the cavity, so as to avoid interference with the molding area during the core pulling rotation process;

[0010] Rotary core-pulling step: Drive the second template and the third template to separate from each other, so that the linkage set pull rod assembly moves downward and drives the connected core-pulling part to rotate around the preset rotating axis, so that the arc core-pulling part on the core-pulling part disengages from the arc inner cavity of the plastic part hook, thereby realizing the core-pulling of the inner cavity of the plastic part.

[0011] Ejection and demolding steps: Drive the third and fourth mold plates to continue separating, and use the ejector pin assembly to eject the plastic part from the moving mold side. At the same time, use the scraper arranged on the fixed mold side to scrape the gate away from the moving mold core, thereby completing the overall demolding of the plastic part.

[0012] Furthermore, in the pre-positioning step, the positioning component includes a moving mold insert and a support block disposed on the moving mold side, which respectively abut against the core foot and its bottom area of ​​the core-pulling part to limit the axial or radial displacement of the core-pulling part during injection.

[0013] Furthermore, in the first mold opening and clearance step, the separation of the first template and the second template ensures that the moving mold insert and the support block are removed from the core-pulling part by a distance not less than the safety clearance required for the core-pulling part to rotate.

[0014] Furthermore, in the second mold opening and retraction step, the bending pin mechanism includes a bending pin block and a cooperating inclined guide surface, which drives the fixed mold slider to retract synchronously along the guide groove through the relative movement between the templates.

[0015] Furthermore, in the rotating core-pulling step, the relative displacement between the second and third templates drives the tie rod assembly to move downward, thereby forming a mechanical transmission through the connecting rod, causing the core-pulling part to generate angular displacement around the rotation axis.

[0016] Furthermore, after the rotational core-pulling step is completed, an elastic restoring force is provided in the mold-closing direction by a set reset spring, so that the core-pulling part automatically resets to the forming position during the next mold closing.

[0017] Furthermore, in the ejection and demolding step, the gate is scraped laterally by a scraper, so that no additional ejection mechanism is needed when the gate detaches from the moving mold side, thus adapting to situations where the mold structure space is limited.

[0018] Furthermore, the method is applicable to arc hook plastic parts having a shell-type inner cavity arranged along the outer arc contour of the hook, in order to improve their cooling shrinkage and surface defects.

[0019] Furthermore, cooling is achieved through a water circulation structure on the core-pulling part before injection, thereby improving the temperature uniformity between the core-pulling part and the cavity area and enhancing the molding quality.

[0020] A core-pulling mechanism for injection molds of arc hook plastic parts includes a first core-pulling assembly and a second core-pulling assembly that are mirror images of each other, and a return spring. Each core-pulling assembly includes a core-pulling part, a pull rod, and a connecting rod.

[0021] The core-pulling part has a mountain-shaped structure, including a first connecting foot, a second connecting foot, and a core foot located between the two. The first connecting foot and the second connecting foot are respectively provided with water interface for connecting to the water inlet pipe or the water outlet pipe, connecting ear for hooking to the return spring, and rotating shaft mounting position for hinged to the moving mold core. The core foot is provided with an arc-shaped core-pulling part that matches the arc-shaped inner cavity of the plastic part hook.

[0022] The tie rod includes a first tie rod and a second tie rod located on one side of the first connecting leg and the second connecting leg, respectively;

[0023] The connecting rod includes a first connecting rod and a second connecting rod. The two ends of the first connecting rod are respectively hinged to a first connecting foot and a first pull rod, and the two ends of the second connecting rod are respectively hinged to a second connecting foot and a second pull rod.

[0024] Among them, the tie rod is driven to move downward by the mold opening action, which drives the connecting rod to rotate the core-pulling part around the rotating shaft at the mounting position of the rotating shaft, so that the arc-shaped core-pulling part is pulled out from the arc-shaped inner cavity of the plastic part.

[0025] Furthermore, it also includes a third core-pulling assembly and a fourth core-pulling assembly. The third core-pulling assembly is arranged in an array along the first direction by the first core-pulling assembly, and the fourth core-pulling assembly is arranged in an array along the first direction by the second core-pulling assembly. Adjacent core-pulling components are connected by water pipe joints to form a water circulation system.

[0026] An injection mold for a circular arc hook plastic part includes the aforementioned core-pulling mechanism, and further includes a fixed mold core, a moving mold core, an ejector pin assembly, a first template, a second template, a third template, a fourth template, and a fifth template. The moving mold core is installed on the third template, the fixed mold core is installed on the fourth template, the core-pulling mechanism is installed on the moving mold core, and the core foot is located inside the cavity when the mold is closed.

[0027] The first template, second template, third template, fourth template and fifth template are separated in a predetermined order to sequentially form the functions of core pulling, driving the bending pin, rotating the core pulling and ejecting the finished product.

[0028] Furthermore, the moving mold core is provided with a rotating shaft and a rotating shaft positioning block for positioning the rotating shaft.

[0029] Furthermore, it also includes a moving mold insert and a support block. When the mold is closed, the moving mold insert and the support block respectively abut against the bottom of the core foot and the core-pulling part to prevent the core-pulling part from moving backward under the injection pressure.

[0030] Furthermore, a limit rod is installed on the fixed mold core, and the end of the limit rod is provided with a gate and a scraper, which is used to scrape the gate away from the moving mold core during the mold opening process.

[0031] Furthermore, a bent pin structure is provided between the fourth and fifth templates. The bent pin structure is used to drive the fixed mold slider backward during the mold opening process.

[0032] An injection molding method for an arc-shaped hook plastic part includes the following steps:

[0033] Preliminary steps: After mold closing, the moving mold insert and support block position the core-pulling mold core, so that it abuts against the core foot and prevents it from retracting due to injection pressure;

[0034] First mold opening step: The first template separates from the second template, allowing the moving mold insert and support block to detach from the core-pulling core, making room for the core-pulling rotation action;

[0035] Second mold opening step: The fourth template separates from the fifth template, and the bent pin structure drives the fixed mold slider to retract;

[0036] Core pulling steps: The second template separates from the third template, the pull rod moves down and drives the connecting rod, so that the core pulling part rotates around the rotating axis, realizing the arc core pulling part detaching from the inner cavity of the plastic part;

[0037] Ejection process: The third and fourth mold plates separate, the ejector pin assembly ejects the finished product, and the scraper simultaneously scrapes the gate away from the moving mold core.

[0038] The beneficial effects of this invention are:

[0039] This design allows for precise formation of a shell-like arc-shaped inner cavity arranged along the outer arc contour within the hook, effectively controlling the wall thickness of the plastic part and significantly improving appearance defects such as shrinkage and dents in the finished product. The "mountain"-shaped core-pulling component solves the structural interference problem caused by the arc center being too close to the parting surface, making the rotating core-pulling action smooth and feasible. A return spring ensures stable reset of the core-pulling assembly in the mold-closed state, preventing mold jamming or damage due to positional misalignment. The moving mold insert and support block provide rigid positioning during the injection stage, preventing the core-pulling component from retracting under injection pressure, effectively avoiding burrs and improving the edge quality of the product. A special gate scraper overcomes space limitations, achieving reliable gate demolding. An array of multiple core-pulling components and a connected cooling circuit are suitable for multi-cavity mass production, increasing production capacity and maintaining product consistency. The overall structure realizes a complete functional chain of core pulling, repositioning, demolding, and scraping, ensuring high-quality molding of the second new type of arc hook. Attached Figure Description

[0040] Figure 1 This is a cross-sectional view of the first novel arc hook described in this invention.

[0041] Figure 2 This is a schematic diagram and a cross-sectional view of the second novel arc hook (i.e., the finished product) according to the present invention.

[0042] Figure 3 This is a schematic diagram of the core-pulling part of the present invention.

[0043] Figure 4 This is a schematic diagram of the core-pulling mechanism described in this invention.

[0044] Figure 5 This is a cross-sectional view of the injection mold described in the present invention in the mold parting state.

[0045] Figure 6 for Figure 5 A partial structural diagram.

[0046] Figure 7 This is another partial structural schematic diagram of the present invention.

[0047] Figure 8 This is another partial structural schematic diagram of the present invention. Detailed Implementation

[0048] 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 embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It is understood that the accompanying drawings are provided for reference and illustration only, and are not intended to limit the present invention. The connection relationships shown in the accompanying drawings are only for clear description and do not limit the connection method.

[0049] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, 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 the invention. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. The terminology used in this specification is only for the purpose of describing specific embodiments and is not intended to limit the invention.

[0050] In related technologies, hook plastic parts need to withstand tensile, impact, and repeated fatigue loads in actual use. Traditional right-angle or sharp hook structures are prone to stress concentration, leading to cracking, breakage, and scratches to users or damage to the hung objects during use. Furthermore, sharp-angle structures are more likely to cause defects such as poor filling, weld lines, and shrinkage during injection molding, affecting product consistency. To improve structural strength, safety, and molding quality, after repeated research and design by the technical personnel involved in this project, a novel arc-shaped hook 7 was developed, such as... Figure 1 As shown, it adopts a rounded edge and horn-shaped hook 62 design, which makes the force more even, the operation smoother, and better meets the requirements of injection molding manufacturing process. The first novel rounded hook 7 includes a main body mounting part 61 and a hook part 62 provided on the main body mounting part 61. The hook part 62 and the main body mounting part 61 are integrally formed by injection molding, and the hook part 62 has a rounded edge and horn-shaped structure.

[0051] It should be mentioned that during the production of this first novel arc hook 7, defects such as shrinkage and dents / imprints appeared on the outer surface of its hook portion 62, affecting the appearance of the plastic product. After repeated research by technicians, it was found that this was because the internal hollowness of the hook portion 62 was insufficient, retaining too much wall thickness, and the hollowing process was not carried out along the arc contour of the outer wall of the hook portion 62. Therefore, the defects such as shrinkage and dents / imprints appeared on the hook portion 62. Ultimately, the product of this case (i.e. the final plastic product) was improved to a second novel arc hook 6 (hereinafter referred to as the finished product), including a main body mounting part 61 and a hook part 62 provided on the main body mounting part 61. The hook part 62 and the main body mounting part 61 are integrally molded by injection molding. The hook part 62 has an arc edge and a bull horn-shaped structure. The hook part 62 has an arc-shaped hollow inner cavity 63 formed inside, which is formed along the arc contour of the outer wall of the hook part 62. The side of the main body mounting part 61 away from the hook part 62 is hollow and communicates with the arc-shaped inner cavity 63 of the hook part 62.

[0052] To produce this second novel arc hook 6, after repeated research by technical personnel, a molding die for an arc hook plastic part and its demolding method were proposed in this case, such as... Figures 2-8 As shown.

[0053] A core-pulling mechanism for injection molds includes a first core-pulling assembly 101, a second core-pulling assembly 102, and a return spring 14. The first core-pulling assembly 101 and the second core-pulling assembly 102 are mirror images of each other. The return spring 14 is hooked onto the core-pulling core 11 corresponding to the first core-pulling assembly 101 and the second core-pulling assembly 102, respectively.

[0054] The first core-pulling assembly 101 includes a core-pulling member 11, a pull rod member 12, and a connecting rod member 13, wherein:

[0055] The core-pulling part 11 has a mountain-shaped structure, including a first connecting foot 111 on one side, a second connecting foot 112 on the other side, and a core foot 113 between the first connecting foot 111 and the second connecting foot 112. The first connecting foot 111 and the second connecting foot 112 are respectively provided with pipe interfaces connected by a water inlet pipe 15 and / or a water outlet pipe 16, a connecting ear 111a hooked by a return spring 14, and a rotating shaft mounting position. The rotating shaft mounting position is used to install a rotating shaft 111b that hinges the core-pulling part 11 to the moving mold core 3. The core foot 113 is provided with an arc-shaped core-pulling part 113a that matches the arc-shaped inner cavity 63 of the hook part 62 of the finished product.

[0056] The pull rod 12 includes a first pull rod 121 located on one side of the first connecting foot 111 and a second pull rod 122 located on one side of the second connecting foot 112;

[0057] The connecting rod member 13 includes a first connecting rod 131 and a second connecting rod 132. Two ends of the first connecting rod 131 are respectively hinged to a first connecting foot 111 and a first pull rod 121. Two ends of the second connecting rod 132 are respectively hinged to a second connecting rod and a second pull rod 122;

[0058] Wherein, the first pull rod 121 and the second pull rod 122 are pulled downward to pull the first connecting rod 131 and the second connecting rod 132, and further pull the core pulling core member 11 to rotate along the rotating shaft, so that the arc core pulling part 113a on the core foot 113 of the core pulling core member 11 rotates together, so that the arc core pulling part 113a is pulled out from the arc inner cavity 63 of the hook part 62 of the finished product, realizing core pulling.

[0059] Specifically, due to the new arc hook of this plastic part product, the position of the center point of its feature is relatively close to the mold parting surface and interferes with other parts of the mold. The core pulling core member 11 is specifically designed in a "mountain" shape to avoid interference between the core pulling core member 11 and other parts of the mold during rotational core pulling.

[0060] In addition, in order to avoid or reduce the possibility of jamming and不顺 (smoothness problem not clear in Chinese, assuming it means non - smoothness) during the mold closing and resetting processes after the core pulling core member 11 completes rotational core pulling, a reset spring 14 is designed to play the role of automatically resetting the core pulling core member 11 during mold closing.

[0061] Preferably, the core pulling mechanism further includes a third core pulling component 103 and a fourth core pulling component 104. The third core pulling component 103 is obtained by arraying the first core pulling component 101 along the first direction, and the fourth core pulling component 104 is obtained by arraying the second core pulling component 102 along the first direction. Reset springs 14 respectively hooked to the corresponding core pulling core members 11 are also arranged in a matching manner between the third core pulling component 103 and the fourth core pulling component 104. The core pulling core members 11 corresponding to the first core pulling component 101 and the third core pulling component 103 are connected through a water pipe joint 17. The core pulling core member 11 of the first core pulling component 101 is connected with a water inlet pipe 15, and the core pulling core member 11 of the third core pulling component 103 is connected with a water outlet pipe 16. Similarly, corresponding water pipe joints 17, water inlet pipes 15 and water outlet pipes 16 are also respectively arranged among the second core pulling component 102 and the fourth core pulling component 104.

[0062] An injection mold for an arc - hook plastic part product includes any one of the aforementioned core pulling mechanisms for injection molds, and further includes: a fixed mold core 2, a movable mold core 3, a thimble assembly 4, a first template 51, a second template 52, a third template 53, a fourth template 54, and a fifth template 55; wherein:

[0063] The fourth template 54 is provided with a limiting hook 551 installed;

[0064] The third template 53 is adjacent to the fourth template 54;

[0065] The mold core 2 is installed on the fourth template 54;

[0066] The moving mold core 3 is installed on the third template 53. The core pulling mechanism is installed on the moving mold core 3. When the mold is closed, the moving mold core 3 and the fixed mold core 2 form a cavity 21, and the core foot 113 is located in the cavity 21 when the mold is closed. The moving mold core 3 is provided with a rotating shaft 111b hinged by the core pulling core 11, and a rotating shaft positioning block 111c installed by the rotating shaft 111b.

[0067] The ejector assembly 4 includes an ejector plate 41 located on the side of the third template 53 away from the fourth template 54, an ejector support plate 42 located on the side of the ejector plate 41 opposite to the third template 53, and an ejector 43 extending from the ejector plate 41 and passing through the moving mold core 3.

[0068] The fifth template 55 is adjacent to the fourth template 54 on the side away from the third template 53. The two ends of the limiting hook 551 are respectively connected to the fourth template 54 and the fifth template 55, and are used to limit the mold opening distance between the fourth template 54 and the fifth template 55 to a predetermined distance.

[0069] The second template 52 is adjacent to the third template 53 on the side away from the second template 52;

[0070] The first template 51 is located adjacent to the second template 52 on the side away from the third template 53, and is connected to the second template 52 by a limiting screw 511, so that the parting distance between the first template 51 and the second template 52 is limited to a predetermined distance.

[0071] Preferably, the system further includes a moving mold insert 512 and a support block 513. One end of the moving mold insert 512 is mounted on the first mold plate 51, and the other end of the moving mold insert 512 passes through the moving mold core 3 and abuts against the core foot 113 when the mold is closed. One end of the support block 513 is mounted on the first mold plate 51, and the other end of the support block 513 extends toward the moving mold core 3 and abuts against the bottom of the core-pulling part 11 when the mold is closed. Specifically, since the injection pressure is relatively high during the injection molding process, in order to prevent the core-pulling part 11 from retracting under the action of the injection pressure, which would cause burrs to form on the finished product, this invention designs a moving mold insert 512 and a support block 513 to resist the core-pulling part 11, thereby preventing the core-pulling part 11 from retracting during the injection molding process. In addition, it can also separate the first template 51 from the second template 52 for the first time when the injection mold is opened, so that the moving mold insert 512 and the support block 513 are separated from the core-pulling core 11 by a certain distance, so as to make room for rotation when the core-pulling core 11 is rotated and demolded.

[0072] Preferably, a limiting rod 22 is installed on the fixed mold core 2. One end of the limiting rod 22, away from the fixed mold core 2, extends towards the fixed mold core 2, and a gate 221 and a scraper 222 are installed at its end. Specifically, due to space limitations in the mold structure, the mold cannot conventionally eject the gate 221 from the moving mold core 3 side. In this technology, a limiting rod 22 is designed on the side of the fixed mold core 2, and a gate 221 and a scraper 222 are designed on the other end of the limiting rod 22. After the parting surface of the fixed mold core 2 and the moving mold core 3 separates by a certain distance, the gate 221 is scraped out from the moving mold core by the scraper 222, realizing the demolding of the gate 221 on the side of the moving mold core 3.

[0073] Preferably, the fourth template 54 is further provided with a fixed mold slider 542 that extends into the inner cavity of the fixed mold core 2. A bent pin structure 541 for pushing and pulling the fixed mold slider 542 forward and backward is provided between the fourth template 54 and the fifth template 55. When the mold is closed, the fixed mold core 2, the moving mold core 3 and the fixed mold slider 542 form the cavity 21.

[0074] Preferably, the moving mold core 3 is also provided with a hydraulic cylinder 31 and a hydraulic oil outlet 33. Guide pillars 56 can be used to achieve sliding between the mold plates.

[0075] During mold opening, the first template 51 and the second template 52 separate first, until they reach the distance limited by the limit screw 511. During this process, the first template 51 pulls the moving mold insert 512 and the support block 513 downward to make room for the rotation of the core-pulling core 11 and avoid interference. Then, the fourth template 54 and the fifth template 55 separate, until they reach the distance limited by the limit hook 551. During this process, the bent pin structure 541 pulls the fixed mold slider 542 backward. Then, the second template 52 and the third template 53 separate. When the second template 52 pulls the first pull rod 121 and the second pull rod 122 down, the core-pulling core part 11 rotates and performs core pulling, and the core foot 113 is pulled out from the arc inner cavity 63 of the hook part 62 of the finished product; finally, the third template 53 and the fourth template 54 separate, the ejector pin 43 pushes out the finished product, namely the second new type arc hook 6, and the scraper 222 scrapes the gate 221 out from the moving mold core 3, realizing the demolding of the gate 221 in the moving mold core 3, and finally completing the mold parting action.

[0076] In the specification and claims of this application, the terms "comprising / including" and "having / including" and variations thereof are used to specify the presence of the stated features, values, steps or components, but do not exclude the presence or addition of one or more other features, values, steps, components or combinations thereof.

[0077] Some features of the present invention are described in different embodiments for clarity; however, these features may also be described in combination in a single embodiment. Conversely, some features of the present invention are described only in a single embodiment for brevity; however, these features may also be described individually or in any suitable combination in different embodiments.

[0078] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for injection molding and demolding of a plastic part with an arc-shaped hook having an arc-shaped shell-like inner cavity, characterized in that, Includes the following steps: Pre-positioning step: After the mold is closed, the core-pulling part is restricted by the positioning component set on the moving mold side, so that the core-pulling part maintains its corresponding cavity forming position during the injection stage and avoids backward displacement under the action of injection pressure. First mold opening clearance step: Drive the first template and the second template to separate along the mold parting direction, which is used to restrict the positioning component of the core-pulling part from being removed from the core-pulling part, and provide clearance space for the rotation of the core-pulling part; The second mold opening and retraction step: continue to drive the fourth template to separate from the fifth template, and use the bending pin mechanism arranged between the fourth template and the fifth template to drive the fixed mold slider to retract away from the cavity, so as to avoid interference with the molding area during the core pulling rotation process; Rotary core-pulling step: Drive the second template and the third template to separate from each other, so that the linkage set pull rod assembly moves downward and drives the connected core-pulling part to rotate around the preset rotating axis, so that the arc core-pulling part on the core-pulling part disengages from the arc inner cavity of the plastic part hook, thereby realizing the core-pulling of the inner cavity of the plastic part. Ejection and demolding steps: Drive the third and fourth mold plates to continue separating, and use the ejector pin assembly to eject the plastic part from the moving mold side. At the same time, use the scraper arranged on the fixed mold side to scrape the gate away from the moving mold core, thereby completing the overall demolding of the plastic part.

2. The injection molding demolding method for forming a circular hook plastic part with a circular arc shell-type inner cavity according to claim 1, characterized in that, In the pre-positioning step, the positioning component includes a moving mold insert and a support block disposed on the moving mold side. The moving mold insert and the support block respectively abut against the core foot and the bottom of the core-pulling part to limit the axial or radial displacement of the core-pulling part during injection.

3. The injection molding demolding method for forming a circular hook plastic part with a circular arc shell-type inner cavity according to claim 2, characterized in that, In the first mold opening and clearance step, the separation of the first template and the second template ensures that the moving mold insert and the support block are removed from the core-pulling part by a distance that is not less than the safety clearance required for the core-pulling part to rotate.

4. The injection molding demolding method for forming a circular hook plastic part with a circular arc shell-type inner cavity according to claim 3, characterized in that, In the second mold opening and retraction step, the bending pin mechanism includes a bending pin block and an inclined guide surface that cooperates with the bending pin block. The relative movement between the fourth template and the fifth template drives the fixed mold slider to retract synchronously along the guide groove.

5. The injection molding demolding method for forming a circular hook plastic part with a circular arc shell-type inner cavity according to claim 4, characterized in that, During the rotating core-pulling step, the relative displacement between the second and third templates drives the tie rod assembly to move downward, which in turn forms a mechanical transmission through the connecting rod, causing the core-pulling part to generate angular displacement around the rotation axis.

6. The injection molding demolding method for forming a circular hook plastic part with a circular arc shell-type inner cavity according to claim 5, characterized in that, After the rotational core-pulling step is completed, the return spring provides elastic restoring force in the mold closing direction, so that the core-pulling part automatically returns to the forming position when the mold closes again.

7. The injection molding demolding method for forming a circular hook plastic part with a circular arc shell-type inner cavity according to claim 6, characterized in that, In the ejection and demolding process, the gate is scraped laterally by a scraper, so that no additional ejection mechanism is needed when the gate detaches from the moving mold side.

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