A molding device and a method for producing a thin-walled product

Abstract

The application discloses a forming device for injection molding of a thin-walled product, comprising a mold, a cooling assembly and an ejection assembly. The mold comprises a fixed mold and a movable mold which are matched with each other. The fixed mold and the movable mold jointly form a mold cavity for forming the thin-walled product after being closed. A plurality of inserts are installed on the fixed mold and / or the movable mold. An exhaust structure is arranged on the insert. The exhaust structure comprises a first exhaust section, a second exhaust section and a gas guide section. The first exhaust section, the second exhaust section and the gas guide section are sequentially arranged along the thickness direction of the insert, and jointly form an exhaust channel which connects the mold cavity and the external environment. The application further discloses a preparation method of the thin-walled product.

Description

Technical Field

[0001] This application relates to the field of injection molding technology, and in particular to a molding apparatus and a method for preparing thin-walled products. Background Technology

[0002] In recent years, with the development of consumer electronics, smart devices, and lightweight products, thin-walled products have been widely used due to their advantages such as light weight, low material consumption, and compact structure. Typically, thin-walled products have a small wall thickness, for example, no more than 0.8 mm. Therefore, during injection molding, the molten plastic needs to fill the mold cavity in a shorter time, placing higher demands on the mold structure and molding process.

[0003] However, due to the smaller wall thickness of thin-walled products, the molten plastic fills the mold cavity more quickly, making it difficult for air to escape in time. This easily leads to trapped air at the flow ends, structural transition areas, and around inserts. When the gas in the mold cavity is compressed at high speed, it can easily generate localized high temperatures, resulting in defects such as scorching and black spots on the product. At the same time, trapped air can also affect the normal flow of molten plastic, causing problems such as insufficient glue, short shots, poor welds, and poor dimensional stability, thus affecting the product molding quality and mass production stability.

[0004] In the existing technology, molds usually rely mainly on the venting grooves on the parting surface or the gaps between mold parts for venting. However, for thin-walled products with fast filling speed, the venting efficiency of the above venting methods is limited and it is difficult to meet the fast venting requirements under high-speed filling conditions. It is still easy to cause local air entrapment and scorching. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a molding apparatus that can improve the problems of trapped gas, scorching, insufficient glue and poor welding caused by the difficulty of timely discharge of gas in the mold cavity during the injection molding process of thin-walled products, thereby improving the molding quality and molding stability of thin-walled products.

[0006] This invention provides a molding apparatus for injection molding of thin-walled products, including a mold, a cooling component for controlling the temperature of the mold, a casting component for injecting molten plastic into the mold, and an ejection component for ejecting the molded thin-walled product from the mold. The mold includes a fixed mold and a moving mold that cooperate with each other. After the fixed mold and the moving mold are closed, they together form a mold cavity for molding the thin-walled product. Multiple inserts are installed on the fixed mold and / or the moving mold. The insert is provided with an exhaust structure, which includes a first exhaust section communicating with the mold cavity, a second exhaust section communicating with the first exhaust section, and an air guide section communicating with the outside atmosphere. The first exhaust section, the second exhaust section, and the air guide section are arranged sequentially along the thickness direction of the insert, forming an exhaust channel that connects the mold cavity with the outside environment.

[0007] In one embodiment, the outer peripheral surface of the first exhaust section is provided with a plurality of spaced first exhaust grooves, the outer peripheral surface of the second exhaust section is recessed inward to form a surrounding second exhaust groove, and the outer peripheral surface of the air guide section is provided with an air guide groove communicating with the second exhaust groove.

[0008] In one embodiment, the plurality of first exhaust grooves extend along the thickness direction of the first exhaust section, and the plurality of first exhaust grooves are distributed at intervals along the circumference of the first exhaust section and are independently arranged with respect to each other.

[0009] In one embodiment, a connecting groove is provided at one end of the first exhaust section near the second exhaust section. The connecting groove is connected to the second exhaust groove, but is not directly connected to the plurality of first exhaust grooves. The end of the connecting groove near the first exhaust section is arched.

[0010] In one embodiment, the moving mold has a plurality of gates communicating with the mold cavity, the plurality of gates being spaced apart along the length of the mold, and the casting assembly includes a glue inlet and a plurality of glue outlets communicating with the glue inlet, the glue outlet ends of the plurality of glue outlets being respectively connected to the plurality of gates.

[0011] In one embodiment, the number of gates is six, including two first gates, two second gates and two third gates. The two first gates and the two second gates are symmetrically arranged at both ends of the mold and away from the geometric center of the mold, and the two third gates are symmetrically arranged in the middle of the mold and close to the geometric center of the mold.

[0012] In one embodiment, the mold further includes a plurality of forming ejector pins movably disposed on the fixed mold, one end of the plurality of forming ejector pins extending into the mold cavity and flush with the cavity surface of the mold cavity, the plurality of forming ejector pins being spaced apart along the periphery of the mold cavity.

[0013] In one embodiment, the ejection assembly includes an ejection cylinder and a plurality of ejector components disposed at the output end of the ejection cylinder. The plurality of ejector components correspond one-to-one with the plurality of forming ejector pins. The ejector components can move along the thickness direction of the mold under the drive of the ejection cylinder, pushing the corresponding forming ejector pin to eject the formed thin-walled product.

[0014] In one embodiment, the cooling assembly includes a plurality of spaced-apart cooling pipes that are at least partially attached to the mold. The plurality of cooling pipes are independently arranged, and each cooling pipe has an independent inlet and outlet.

[0015] The present invention also provides a method for preparing a thin-walled product, characterized in that injection molding is performed using the molding apparatus described in the above embodiments, and the preparation method includes the following steps: The molding apparatus is provided such that the fixed mold and the moving mold, after being closed, together form a mold cavity for molding thin-walled products; Activate the cooling system to pre-cool the mold and control its temperature; Molten plastic is injected into the mold cavity, and during the filling process, the gas in the mold cavity is gradually discharged through the first venting section, the second venting section and the third venting section. The molten plastic in the mold cavity is held under pressure and cooled to solidify, forming a thin-walled product; After the mold is opened, the thin-walled product is ejected through the ejector assembly.

[0016] This invention provides a molding apparatus that, by incorporating an exhaust structure on an insert and employing a configuration of a first exhaust section, a second exhaust section, and a guide section arranged sequentially along the thickness of the insert, allows gas within the mold cavity to be discharged step-by-step to the external environment via the exhaust channels. Specifically, the first exhaust section discharges gas near the mold cavity area, the second exhaust section further collects and guides the discharged gas, and the guide section directs the gas to the outside atmosphere, thus forming a continuous, low-resistance exhaust path. This apparatus is particularly suitable for injection molding of thin-walled products with fast filling speeds and small wall thicknesses, effectively improving gas trapping within the mold cavity, reducing molding defects such as scorching, insufficient glue, and poor welding, and enhancing product molding quality and mass production stability. Attached Figure Description

[0017] 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.

[0018] Figure 1 An exploded view of a mold provided for a preferred embodiment of the present invention.

[0019] Figure 2 for Figure 1 The middle mold is viewed from another angle in an exploded view.

[0020] Figure 3This is a schematic diagram of the exhaust structure provided in a preferred embodiment of the present invention.

[0021] Figure 4 A schematic diagram of the mold provided in a preferred embodiment of the present invention.

[0022] Figure 5 This is a schematic diagram of the casting component provided in a preferred embodiment of the present invention.

[0023] Figure 6 for Figure 4 A schematic diagram of the middle mold from another perspective.

[0024] Figure 7 This is a schematic diagram of the cooling assembly provided in a preferred embodiment of the present invention.

[0025] Figure 8 This is a schematic diagram of the ejection assembly provided in a preferred embodiment of the present invention.

[0026] Figure 9 for Figure 8 A schematic diagram of the structure in which the ejector component ejects the thin-walled product.

[0027] Figure label: 10. Mold; 20. Casting assembly; 30. Cooling assembly; 40. Ejection assembly; 11. Fixed mold; 12. Moving mold; 13. Mold cavity; 14. Venting structure; 21. Inlet; 22. Outlet pipe; 31. Cooling pipe; 32. Liquid inlet; 33. Liquid outlet; 41. Ejection cylinder; 42. Ejector; 111. Molding ejector pin; 121. Gate; 122. First gate; 123. Second gate; 124. Third gate; 141. First venting section; 142. Second venting section; 143. Air guide section; 144. First venting groove; 145. Second venting groove; 146. Air guide groove; 147. Connecting groove. Detailed Implementation

[0028] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. Based on the description of the present invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of the present invention.

[0029] In the description of this invention, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," etc., 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. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0030] The terms “upper,” “lower,” “left,” “right,” “front,” “back,” “top,” “bottom,” “inner,” and “outer,” etc., 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 of the invention is in use. They are 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 the present invention.

[0031] The terms “first,” “second,” “third,” etc., are used merely to distinguish elements with similar properties, not to indicate or imply relative importance or a specific order.

[0032] The terms “include,” “comprising,” or any other variation thereof are intended to cover non-exclusive inclusion, which includes not only the elements listed but also other elements not expressly listed.

[0033] Please refer to Figures 1 to 2 This invention provides a molding apparatus for injection molding thin-walled products. The apparatus includes a mold 10, a cooling assembly 30, and an ejection assembly. The mold 10 includes a fixed mold 11 and a moving mold 12 that cooperate with each other. After the fixed mold 11 and the moving mold 12 are closed, they together form a mold cavity 13 for molding thin-walled products. Molten plastic is injected into the mold cavity 13 and cooled and solidified to form the corresponding thin-walled product. The cooling assembly 30 is used to cool and control the temperature of the mold 10, and the ejection assembly is used to eject the molded thin-walled product from the mold cavity 13.

[0034] The fixed mold 11 and / or the moving mold 12 are detachably equipped with multiple inserts. By setting the inserts, it is not only convenient for the processing and manufacturing of the mold 10 and its subsequent maintenance and replacement, but also to meet the molding requirements of complex local structures of thin-walled products. The position where the fixed mold 11 and the moving mold 12 are in contact with each other forms a parting surface, which is used to realize the opening and closing of the mold 10.

[0035] Because thin-walled products have smaller wall thicknesses, the molten plastic fills the mold cavity 13 faster. During the filling process, air in the mold cavity 13 tends to accumulate at the end of the parting surface, around the insert, and in structural transition areas, resulting in trapped air. Therefore, in this embodiment, a venting structure 14 is provided on the insert to allow the gas in the mold cavity 13 to be discharged to the outside of the mold 10, thereby improving the venting efficiency of the mold cavity 13 and reducing molding defects such as product burning, insufficient glue, and poor welding.

[0036] like Figure 3As shown, in this embodiment, the exhaust structure 14 includes a first exhaust section 141 communicating with the mold cavity 13, a second exhaust section 142 communicating with the first exhaust section 141, and a guide section 143 communicating with the outside atmosphere. The first exhaust section 141, the second exhaust section 142, and the guide section 143 are arranged sequentially along the thickness direction of the insert, forming an exhaust channel that connects the mold cavity 13 with the outside environment.

[0037] Specifically, the first venting section 141 is located on the side near the mold cavity 13. Multiple spaced first venting grooves 144 are formed on the outer circumferential surface of the first venting section 141, extending along the thickness direction of the insert. Preferably, the multiple first venting grooves 144 are evenly distributed circumferentially along the first venting section 141 and are independently arranged, thus forming multiple shallow venting channels circumferentially in the first venting section 141. When molten plastic fills the mold cavity 13 at high speed, the gas accumulated in the mold cavity 13 can be quickly discharged through the multiple first venting grooves 144 to achieve shallow venting. Because the multiple first venting grooves 144 are independently arranged, while ensuring venting efficiency, it also prevents the molten plastic from overflowing along the venting channels, thus balancing venting performance and sealing performance.

[0038] The second venting section 142 is located on the side of the first venting section 141 away from the mold cavity 13. The outer periphery of the second venting section 142 is recessed inward to form a second venting groove 145 that is arranged around it. The second venting groove 145 extends continuously along the circumference of the second venting section 142, thereby forming an annular venting space.

[0039] Furthermore, a connecting groove 147 is provided at one end of the first exhaust section 141 near the second exhaust section 142. The connecting groove 147 communicates with the second exhaust groove 145, but is not directly connected to the plurality of first exhaust grooves 144. Preferably, the connecting groove 147 is arranged in an arched structure. After the gas is discharged through the first exhaust groove 144, it enters the connecting groove 147 along the gap between the first exhaust groove 144 and the mold 10, and flows into the second exhaust groove 145 under the guidance of the arched structure, thereby realizing a smooth transition of gas from the first exhaust section 141 to the second exhaust section 142.

[0040] With the above structure, after the gas is discharged through multiple first exhaust channels 144, it can be further collected into the connecting channel 147 and then enter the second exhaust channel 145 through the connecting channel 147. Since the second exhaust channel 145 has a continuous annular space, it can provide a larger flow cross-sectional area for the gas, thereby reducing exhaust resistance and achieving deep exhaust. At the same time, the arched structure can also collect the returning gas, causing the returning gas to gather in the arched area and finally enter the second exhaust channel 145 for discharge under the impetus of the subsequently discharged gas, thereby avoiding gas stagnation and improving overall exhaust efficiency.

[0041] The air guide section 143 is located on the side of the second exhaust section 142 away from the first exhaust section 141. An air guide groove 146 is formed on the outer peripheral surface of the air guide section 143. The air guide groove 146 extends along the thickness direction of the insert and communicates with the second exhaust groove 145. Preferably, the air guide groove 146 is formed by a chamfer located at the outer peripheral edge of the air guide section 143, and the cross-section of the air guide groove 146 is triangular. Specifically, the chamfer extends along the thickness direction of the insert, thereby forming an air guide space between the air guide section 143 and the mounting hole of the mold 10.

[0042] By providing the air guide groove 146, the gas, after being collected by the second exhaust groove 145, can be further guided to the external environment of the mold 10 for discharge. Since the air guide groove 146 is formed by a chamfered structure, it provides a stable discharge channel for the gas while ensuring the structural strength of the insert. After flowing along the air guide groove 146 to the end of the air guide section 143, the gas can directly connect with the external environment, thereby preventing gas accumulation at the exhaust end and improving overall exhaust efficiency.

[0043] In summary, the first venting section 141, the second venting section 142, and the air guiding section 143 together constitute a three-stage venting structure 14, from shallow venting and deep venting to atmospheric venting. Multiple first venting channels 144 are responsible for rapidly venting gas near the mold cavity 13, the second venting channels 145 are responsible for collecting and expanding the vented gas, and the air guiding channels 146 are responsible for guiding the gas to the external environment, thus forming a continuous, low-resistance, and highly efficient venting path. This is particularly suitable for thin-walled product molds 10 with thin walls and high filling speeds, effectively improving molding defects such as trapped air, scorching, insufficient glue, and poor welding.

[0044] like Figure 4 As shown, the moving mold 12 has multiple gates 121 communicating with the mold cavity 13. The multiple gates 121 are spaced apart along the length of the mold 10 to achieve multi-point injection. In this embodiment, there are six gates 121, which are divided into two groups and symmetrically distributed.

[0045] Specifically, the six gates 121 include two first gates 122, two second gates 123, and two third gates 124. The two first gates 122 are symmetrically arranged at one end of the mold 10, and the two second gates 123 are symmetrically arranged at the other end of the mold 10. The two first gates 122 and the two second gates 123 are all located away from the geometric center of the mold 10. The two third gates 124 are symmetrically arranged in the middle of the mold 10 and close to the geometric center of the mold 10.

[0046] With the above arrangement, multiple gates 121 are distributed along the length of the mold 10 and form a symmetrical injection layout on the overall structure of the mold 10, so that the molten plastic can enter the mold cavity 13 from multiple directions at the same time, thereby shortening the flow path corresponding to a single gate 121, reducing the flow length ratio, and reducing the pressure loss of the molten plastic during the filling process.

[0047] like Figure 5 As shown, the molding apparatus also includes a casting assembly 20, which is used to transport molten plastic into the mold cavity 13. The casting assembly 20 includes a sprue 21 and six outlet pipes 22 connected to the sprue 21. The outlet ends of the six outlet pipes 22 are respectively connected to six gates 121 to transport molten plastic to the corresponding gates 121. Among them, the outlet pipes 22 are hot runners, and the gates 121 and the mold cavity 13 form a cold runner, thus constituting a sprue structure that combines hot and cold runners.

[0048] During operation, molten plastic enters the casting component 20 through the inlet 21 and first flows into six outlet pipes 22. Under the diversion effect of the outlet pipes 22, it is delivered to the corresponding gates 121, and then injected into the mold cavity 13 through each gate 121. Because the outlet pipes 22 adopt a hot runner structure, they can effectively maintain the temperature stability of the molten plastic during the conveying process, preventing premature cooling and solidification. Simultaneously, the symmetrical arrangement of multiple gates 121 allows the molten plastic to enter the mold cavity 13 simultaneously from multiple directions with a shorter flow path, achieving symmetrical filling.

[0049] Since the wall thickness of thin-walled products is typically no more than 0.8 mm, the temperature of the molten plastic decays rapidly during the flow process, and the thin-walled structure is more sensitive to injection pressure loss. If a single-point injection method is used, problems such as insufficient pressure, incomplete filling, and obvious weld lines at the end of the mold cavity 13 are likely to occur. However, this embodiment, by setting multiple gates 121 and adopting a multi-point injection method that converts hot runners to cold runners, can effectively shorten the flow distance of the molten plastic, reduce the flow length ratio, and lower the pressure drop at the gates 121. This allows for more balanced filling pressure in all areas of the mold cavity 13, resulting in more uniform product shrinkage.

[0050] Therefore, the structural design combining hot runner and multi-point gate 121 can not only improve the filling integrity of thin-walled products, but also effectively reduce molding defects such as end-point missing glue, poor welding and warping caused by pressure decay, thereby improving the dimensional stability and molding quality of the products.

[0051] like Figure 6As shown, the mold 10 also includes a plurality of forming ejector pins 111 movably disposed on the fixed mold 11 and / or the moving mold 12. One end of the plurality of forming ejector pins 111 extends into the mold cavity 13 and is flush with the cavity surface of the mold cavity 13, thereby forming part of the forming surface of the mold cavity 13. The plurality of forming ejector pins 111 are distributed at intervals along the periphery of the mold cavity 13.

[0052] When molten plastic is injected into the mold cavity 13, multiple molding ejector pins 111 participate in product molding. After the product cools and the mold is opened, the multiple molding ejector pins 111 move along the height direction of the mold cavity 13, thereby ejecting the product from the mold cavity 13. Since the multiple molding ejector pins 111 are distributed at intervals along the periphery of the mold cavity 13, the ejection force can be evenly applied to all areas of the product, reducing problems such as whitening, punching through, and deformation caused by excessive local force.

[0053] Because thin-walled products have smaller wall thicknesses and relatively weaker overall strength, it is usually necessary to increase the number of ejector pins 111 to ensure uniform ejection force. However, as the number of ejector pins 111 increases, the contact area between the product and the mold 10 increases accordingly. During demolding, the product is prone to greater clamping force and frictional resistance, which affects the ejection effect.

[0054] like Figure 8-9 As shown, in this embodiment, the molding apparatus further includes an ejection assembly 40, which includes an ejection cylinder 41 and an ejector 42 disposed at the output end of the ejection cylinder 41. The ejector 42 is located inside the area enclosed by the molding ejector pins 111. The outer contour of the ejector 42 is adapted to the shape of the corresponding area of ​​the product. Preferably, the ejection surface of the ejector 42 is adapted to the inner surface of the product. After the product is molded, the ejection cylinder 41 drives the ejector 42 to move toward the product, so that the ejector 42 directly acts on the multiple molding ejector pins 111 to push the product away from the wall of the mold cavity 13. Subsequently, the multiple molding ejector pins 111 continue to assist in ejecting the product, thereby achieving smooth demolding of the product.

[0055] By setting up an ejector assembly, auxiliary driving force can be provided to multiple molding ejector pins 111 while ensuring that the molding ejector pins 111 are evenly distributed. Specifically, the ejector cylinder drives the ejector to move, and the ejector directly acts on multiple molding ejector pins 111 to drive them to move synchronously in the ejection direction. This increases the ejection speed and force of the molding ejector pins 111, reduces the clamping force between the product and the mold cavity 13, and avoids the problem of poor ejection caused by an increase in the number of molding ejector pins 111. At the same time, by centrally driving multiple molding ejector pins 111 through the ejector, the force on each molding ejector pin 111 can be more even, thereby effectively improving phenomena such as whitening, punching, deformation, and sticking to the mold in thin-walled products.

[0056] like Figure 7 As shown, the cooling assembly 30 includes a plurality of spaced-apart cooling pipes 31, which are at least partially attached to the mold 10 to allow the cooling medium to exchange heat with the mold 10, thereby removing the heat generated by the mold 10 during the molding process. Preferably, the plurality of cooling pipes 31 are distributed along the contour of the mold cavity 13 and correspond to different areas of the mold 10 to improve the cooling uniformity of each area of ​​the mold 10.

[0057] In this embodiment, multiple cooling pipes 31 are independently configured, each with an independent inlet end 32 and outlet end 33, thus forming multiple independent cooling circuits. Adjacent cooling pipes 31 are not connected to avoid forming series flow channels between multiple cooling areas. Through this configuration, the cooling medium entering each cooling pipe 31 can independently cool the corresponding area, allowing for zoned temperature control of different areas of the mold 10. Compared to traditional series cooling structures, the independent cooling circuits in this embodiment reduce the temperature decay of the cooling medium during flow, avoiding uneven temperature distribution in the mold 10 due to differences in cooling capacity between front and rear areas. Furthermore, when local deformation occurs in the product, the mold temperature of the corresponding area can be fine-tuned by individually adjusting the flow rate, velocity, or cooling temperature of the corresponding cooling pipe 31, thereby improving product dimensional stability and mitigating product deformation issues.

[0058] In some embodiments, multiple cooling pipes 31 correspond to different molding areas and are equipped with independent temperature control units. The temperature control units are used to adjust the temperature of the cooling medium in the corresponding cooling pipes 31 to achieve differentiated temperature control in different areas.

[0059] For example, when a thin-walled product includes both glossy and matte areas, a two-shot molding process can be used. In this process, a first cooling circuit is installed in the first molding area corresponding to the glossy area, and a second cooling circuit is installed in the second molding area corresponding to the matte area. During molding, the mold temperature of the first cooling circuit is controlled at approximately 100°C, and the mold temperature of the second cooling circuit is controlled at approximately 80°C, ensuring that different areas achieve molding temperatures that match their surface finish.

[0060] By employing the aforementioned zoned temperature control method, the surface quality and appearance consistency of the product can be improved. Simultaneously, during the two-shot molding process, the molten plastic formed in the high-temperature zone can cover the position of the preceding gate 121, thereby reducing the impact of gate 121 residue on the product's appearance. Preferably, the residual height of the gate 121 after molding is no greater than 0.3mm, further enhancing the product's appearance quality.

[0061] In this embodiment, the cavity surfaces of the moving mold 12 and the fixed mold 11, which are positioned opposite each other, are both polished to improve the smoothness of the cavity surface of the mold 10. Preferably, different areas of the mold 10 adopt differentiated polishing methods according to the product structural characteristics. Specifically, functional surfaces and deep rib areas are treated with high-gloss polishing, while ordinary ribs are treated with conventional polishing, so as to balance the product appearance quality and demolding performance.

[0062] Because thin-walled products typically have smaller wall thicknesses, the molten plastic flows for a shorter time and cools faster within the mold cavity 13, making it more sensitive to the surface roughness of the mold cavity 13. If tool marks, pits, or machining marks exist on the surface of the mold 10, they can easily create corresponding defects on the plastic part surface, increasing the flow resistance of the molten plastic and thus affecting the filling effect. Therefore, polishing the cavity surfaces of the moving mold 12 and the fixed mold 11 can effectively reduce microscopic protrusions and machining marks on the cavity surface, improving the smoothness and finish of the mold 10 surface. Furthermore, the polished surface of the mold cavity 13 is smoother, reducing the interfacial frictional resistance experienced by the molten plastic as it flows within the mold cavity 13, thereby reducing the flow resistance of the molten plastic and improving its filling capacity in thin-walled and deep-rib areas.

[0063] Meanwhile, polishing also facilitates product demolding. As the surface roughness of mold 10 decreases, the friction and clamping force between the product and the mold cavity 13 wall decrease accordingly, thus alleviating the problem of increased ejection resistance caused by excessive local clamping force. Especially when multiple ejector pins 111 work together to eject, it can effectively reduce phenomena such as whitening, punching, deformation, and sticking to the mold, improving the product's demolding stability.

[0064] In some embodiments, the deep rib areas and functional surfaces in thin-walled products may be treated with a higher polishing grade than ordinary areas. For example, ordinary ribs may be polished to B1 grade, while functional surfaces and deep rib areas may be polished to A3 grade. This reduces the whitening problem caused by the greater demolding resistance in the deep rib areas and improves the surface quality of the functional surfaces. After enhanced polishing, the ejection effect of the product can be significantly improved, and the whitening phenomenon in the deep rib areas is significantly reduced, thereby further improving product yield and appearance quality.

[0065] This invention also provides a method for preparing a thin-walled product, which involves injection molding using the molding apparatus described above. The method includes the following steps: S1. A molding apparatus according to the above embodiment is provided, and a mold cavity 13 for molding thin-walled products is formed by closing the fixed mold 11 and the moving mold 12 together. At the same time, the surfaces of the cavity that are disposed opposite to the fixed mold 11 and the moving mold 12 are polished to improve the surface smoothness of the cavity, reduce the flow resistance of molten plastic in the mold cavity 13, and improve the demolding performance of the product.

[0066] S2. Start the cooling component 30 to allow the cooling medium to enter multiple independently set cooling pipes 31 to pre-cool and control the mold temperature in different areas of the mold 10.

[0067] Preferably, the temperature of each corresponding area is regulated by multiple independent cooling circuits to achieve a preset temperature distribution in each area of ​​the mold 10. When the thin-walled product includes areas with different surface effects, the temperature of different molding areas can be controlled separately. For example, the mold temperature of the molding area corresponding to the high-gloss area is controlled at around 100°C, and the mold temperature of the molding area corresponding to the matte area is controlled at around 80°C to improve the consistency of the product appearance.

[0068] S3. After heating the plastic raw material to a molten state, it is conveyed to the casting component 20 through the inlet 21. The molten plastic is conveyed to multiple gates 121 under the diversion action of multiple outlet pipes 22, and is simultaneously injected into the mold cavity 13 through each gate 121 to achieve multi-point injection.

[0069] During the process of filling the mold cavity 13 with molten plastic, the gas accumulated in the mold cavity 13 is discharged through the venting structure 14 provided on the insert. Specifically, multiple first venting grooves 144 near the mold cavity 13 perform rapid shallow venting of the gas in the mold cavity 13. The gas further enters the second venting groove 145 through the connecting groove 147 for collection and expansion, and is finally discharged to the external environment through the air guide groove 146, so as to form a continuous venting path from shallow venting, deep venting to introduction into the atmosphere, thereby reducing problems such as trapped gas, scorching and insufficient glue during the high-speed filling of thin-walled products.

[0070] S4. After the mold cavity 13 is filled, the molten plastic inside the mold cavity 13 is held under pressure to compensate for the plastic's cooling shrinkage. Subsequently, the mold 10 is continuously cooled by the cooling assembly 30, allowing the molten plastic to gradually cool and solidify to form a thin-walled product. Since multiple cooling pipes 31 are set independently, the temperature attenuation during the flow of the cooling medium can be reduced, allowing different areas of the mold 10 to obtain a more balanced cooling effect, thereby reducing product warpage and improving dimensional stability.

[0071] S5. After the thin-walled product cools and solidifies, the fixed mold 11 and the moving mold 12 separate from the mold. The ejector cylinder in the ejector assembly drives the ejector to move towards the product, so that the product first separates from the wall of the mold cavity 13. Subsequently, multiple forming ejector pins 111 move synchronously along the ejection direction to assist in ejecting the product, thereby detaching the thin-walled product from the mold cavity 13. Since the multiple forming ejector pins 111 are distributed at intervals along the periphery of the mold cavity 13 and are configured in conjunction with the ejector assembly, the local stress concentration during the product ejection process can be reduced, reducing problems such as ejection whitening, ejection penetration, deformation, and sticking to the mold, and improving the demolding stability of the thin-walled product.

[0072] The above preparation method enables molten plastic to be filled quickly, uniformly and stably in the thin-walled mold cavity 13. Through the combination of multi-stage venting, zoned cooling and auxiliary ejection, the problems that are prone to occur in the injection molding process of thin-walled products, such as trapped air burning, insufficient glue, poor welding, warping and deformation and difficult demolding, are effectively improved, thereby improving the molding quality, dimensional stability and mass production consistency of thin-walled products.

[0073] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0074] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A molding apparatus for injection molding of thin-walled products, characterized in that, The device includes a mold, a cooling assembly for controlling the temperature of the mold, a casting assembly for injecting molten plastic into the mold, and an ejection assembly for ejecting the formed thin-walled product from the mold. The mold includes a fixed mold and a moving mold that cooperate with each other. After the fixed mold and the moving mold are closed, they together form a mold cavity for forming the thin-walled product. Multiple inserts are installed on the fixed mold and / or the moving mold. The insert is provided with an exhaust structure, which includes a first exhaust section communicating with the mold cavity, a second exhaust section communicating with the first exhaust section, and an air guide section communicating with the outside atmosphere. The first exhaust section, the second exhaust section, and the air guide section are arranged sequentially along the thickness direction of the insert, forming an exhaust channel that connects the mold cavity with the outside environment. The outer peripheral surface of the first exhaust section is provided with a plurality of spaced first exhaust grooves, the outer peripheral surface of the second exhaust section is recessed inward to form a surrounding second exhaust groove, and the outer peripheral surface of the air guide section is provided with an air guide groove that communicates with the second exhaust groove. The first exhaust section has a connecting groove at one end near the second exhaust section. The connecting groove is connected to the second exhaust groove, but is not directly connected to the plurality of first exhaust grooves. The end of the connecting groove near the first exhaust section is arched.

2. The molding apparatus as described in claim 1, characterized in that, The plurality of first exhaust grooves extend along the thickness direction of the first exhaust section, and the plurality of first exhaust grooves are distributed at intervals along the circumference of the first exhaust section and are independently arranged with each other.

3. The molding apparatus as described in claim 1, characterized in that, The moving mold has multiple gates that communicate with the mold cavity. The multiple gates are spaced apart along the length of the mold. The casting assembly includes a glue inlet and multiple glue outlets that communicate with the glue inlet. The glue outlet ends of the multiple glue outlets are respectively connected to the multiple gates.

4. The molding apparatus as described in claim 3, characterized in that, The number of gates is six, including two first gates, two second gates and two third gates. The two first gates and the two second gates are symmetrically arranged at both ends of the mold and away from the geometric center of the mold. The two third gates are symmetrically arranged in the middle of the mold and close to the geometric center of the mold.

5. The molding apparatus as described in claim 1, characterized in that, The mold also includes a plurality of forming ejector pins movably disposed on the fixed mold, one end of the plurality of forming ejector pins extending into the mold cavity and being flush with the cavity surface of the mold cavity, and the plurality of forming ejector pins being distributed at intervals along the periphery of the mold cavity.

6. The molding apparatus as described in claim 5, characterized in that, The ejection assembly includes an ejection cylinder and a plurality of ejector components disposed at the output end of the ejection cylinder. The plurality of ejector components correspond one-to-one with the plurality of forming ejector pins. The ejector components can move along the thickness direction of the mold under the drive of the ejection cylinder, pushing the corresponding forming ejector pin to eject the formed thin-walled product.

7. The molding apparatus according to any one of claims 1-6, characterized in that, The cooling assembly includes multiple cooling pipes spaced apart, which at least partially fit into the mold. The multiple cooling pipes are independently arranged, and each cooling pipe has an independent inlet and outlet.

8. A method for preparing a thin-walled product, characterized in that, The preparation method, which uses the molding apparatus as described in any one of claims 1-7 for injection molding, includes the following steps: The molding apparatus is provided such that the fixed mold and the moving mold, after being closed, together form a mold cavity for molding thin-walled products; Activate the cooling system to pre-cool the mold and control its temperature; Molten plastic is injected into the mold cavity, and during the filling process, the gas in the mold cavity is gradually discharged through the first venting section, the second venting section, and the air guiding section. The molten plastic in the mold cavity is held under pressure and cooled to solidify, forming a thin-walled product; After the mold is opened, the thin-walled product is ejected through the ejector assembly.

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