A molding die for plastic products

Abstract

The application discloses a forming die for plastic products, aiming at solving the problem of uneven cooling in the prior art, which leads to product warping and large internal stress. The application comprises a die support, an upper die, a lower die and an injection structure. The innovation mainly lies in that a cooling system composed of an upper cooling unit, an even cooling unit and a lower cooling unit is arranged. The even cooling unit can move reciprocatingly along the vertical direction through a driving mechanism, and special connecting pipes inside the even cooling unit utilize variable diameter design to efficiently mix the cooling liquid from the upper and lower cooling pipes, which has temperature difference due to path change, and output the cooling liquid with uniform temperature to the die core. The dynamic mixing and position change realize forced temperature equalization in the vertical direction of the die, effectively reducing the temperature gradient. Meanwhile, the controllable micro-vibration generated by the vertical movement of the unit helps to improve the cooling uniformity, improve the product quality and reduce the warping deformation.

Description

Technical Field

[0001] This invention belongs to the field of mold machinery technology, and relates to a molding die for plastic products. Background Technology

[0002] In the field of plastic product molding, cylindrical products (such as pen holders and cosmetic containers) are widely used. These products typically have a large length-to-diameter ratio or depth, presenting a significant technical challenge during injection molding cooling: traditional cooling channels are usually fixed to one or both ends of the mold, with coolant flowing in from one end and out from the other. This results in temperature rises as the coolant flows through different parts of the mold, causing the mold temperature to be lower near the coolant inlet and higher further away, creating a significant temperature gradient along the axial and vertical directions of the mold.

[0003] The presence of this axial temperature gradient leads to uneven cooling and shrinkage in different parts of plastic products. For cylindrical products, this often results in warping, substandard roundness, or noticeable shrinkage marks. For slender parts, it easily causes bending deformation, such as warping and high internal residual stress, severely affecting the product's dimensional accuracy, structural strength, and performance. Although the industry has attempted to improve this by optimizing the water channel layout and extending the cooling time, limitations in mold structure and processing costs often prevent a fundamental solution to the problem of uneven axial cooling.

[0004] To address the above problems, this invention proposes a molding die for plastic products. Summary of the Invention

[0005] To address the problems existing in the background art, the present invention proposes a molding die for plastic products.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a molding die for plastic products, comprising a mold support, a lower mold at the top of the mold support, an upper mold vertically slidably connected above the lower mold via guide pillars, and an injection structure at the top of the upper mold; the mating surfaces of the lower mold and the upper mold are respectively provided with a second protruding mold core and a first protruding mold core, forming a cavity when the mold is closed; further comprising: an upper cooling unit, including an upper cooling box and multiple vertical upper cooling pipes;

[0007] The lower cooling unit includes a lower cooling box and multiple vertical lower cooling pipes;

[0008] A uniform cooling unit is located between the upper cooling unit and the lower cooling unit, and includes a mounting sleeve, a cooling shell, and multiple connecting pipes. The mounting sleeve is connected to the lower cooling box through a driving mechanism and can be driven to reciprocate in the vertical direction. The two ends of the connecting pipes are respectively connected to the upper cooling pipe and the lower cooling pipe through sealing joints. The cooling shell is fixed to the inner side of the mounting sleeve and contacts the outer wall of the second protruding mold core.

[0009] Preferably, the connecting pipe includes an outer pipe and an inner pipe coaxially disposed therein; the inner pipe has a diameter-decreasing section; the side wall of the diameter-decreasing section has a liquid outlet hole; the outer pipe has a communication port corresponding to the diameter-decreasing section, which communicates with the cooling shell; the flow channel of the inner pipe is connected to the upper cooling pipe, and the annular gap between the inner pipe and the outer pipe is connected to the lower cooling pipe.

[0010] Preferably, the variable diameter section is composed of a first inner tube with a larger diameter, a tapered buffer tube, and a second inner tube with a smaller diameter connected in sequence.

[0011] Preferably, the unit structure consisting of the first inner tube, the buffer tube, and the second inner tube is multi-segmented.

[0012] Preferably, the driving mechanism consists of multiple electrically operated telescopic rods evenly distributed along the circumference.

[0013] Preferably, the upper cooling pipe and the lower cooling pipe are corrugated pipes that can be vertically extended and retracted.

[0014] Preferably, the vertical movement of the uniform cooling unit can change the length of the upper and lower cooling pipes, thereby causing the upper and lower coolants flowing into the connecting pipe to have a temperature difference due to their different flow paths and to mix.

[0015] Preferably, the vertical reciprocating movement of the uniform cooling unit can generate micro-vibrations within the mold.

[0016] Preferably, it also includes a liquid outlet pipe, which connects the internal cavity of the cooling shell to the lower cooling cavity of the lower cooling unit.

[0017] Preferably, the inner wall of the cooling shell is in close contact with the outer wall of the second protruding mold core.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. This invention utilizes a vertically reciprocating, uniform cooling unit to dynamically adjust the flow path length of the upper and lower coolants, ensuring that the temperature of the coolant after mixing through the connecting pipe consistently fluctuates only slightly around the average value. This design breaks the static "position-temperature" correspondence in traditional cooling systems, actively suppressing the temperature gradient in the vertical direction of the mold. For cylindrical products, it ensures a consistent cooling rate along the circumference, effectively guaranteeing roundness and dimensional accuracy, and preventing ellipticization, opening, or closing deformation. For slender parts, it achieves uniform axial cooling, suppressing bending and warping.

[0020] 2. The vertical reciprocating motion of the uniform cooling unit introduces slight, controllable mechanical vibration into the mold system. This vibration is transmitted to the cooling plastic melt, providing additional energy to the polymer chains, promoting their relaxation and rearrangement, and effectively releasing the internal stress caused by flow orientation and rapid cooling. This process not only significantly reduces the risk of product deformation but also improves its impact resistance and long-term dimensional stability.

[0021] 3. The connecting pipe employs a variable diameter structure and introduces a jet mixing mechanism to force vigorous mixing of the upper and lower coolants, breaking the laminar flow state and achieving rapid homogenization of temperature and composition. This design ensures a highly consistent coolant temperature upon entering the mold core, significantly improving heat exchange efficiency and cooling uniformity. Attached Figure Description

[0022] Figure 1 This is a three-dimensional structural schematic diagram of the present invention;

[0023] Figure 2 This is a schematic diagram of the exploded structure of the present invention;

[0024] Figure 3 This is a cross-sectional structural diagram of the connection between the mold support, mold, injection structure and cooling unit of the present invention.

[0025] Figure 4 This is a cross-sectional exploded view of the connection between the upper cooling unit, the uniform cooling unit and the lower cooling unit of the present invention;

[0026] Figure 5 This is a schematic diagram of the connection between the uniform cooling unit of the present invention and the upper and lower cooling pipes;

[0027] Figure 6 This is a schematic diagram of the uniform cooling unit of the present invention;

[0028] Figure 7 This is a cross-sectional structural schematic diagram of the uniform cooling unit of the present invention;

[0029] Figure 8 This is a cross-sectional structural diagram of the connecting pipe of the present invention;

[0030] Figure 9 This is a cross-sectional structural diagram of the cooling box of the present invention;

[0031] Figure 10 10.1 is a schematic diagram of the vertical movement of the uniform cooling unit of the present invention; 10.2 is a schematic diagram of the uniform cooling unit of the present invention located in the middle position; 10.3 is a schematic diagram of the uniform cooling unit of the present invention after moving upward; 10.4 is a schematic diagram of the uniform cooling unit of the present invention after moving downward.

[0032] In the diagram: 1. Mold support; 11. Guide pillar; 2. Mold; 21. Upper mold; 211. First raised mold core; 22. Lower mold; 221. Second raised mold core; 3. Injection structure; 31. Pipe; 4. Upper cooling unit; 41. Upper cooling box; 411. Upper cooling cavity; 412. Upper cooling pipe mounting cavity; 42. Upper cooling pipe; 5. Uniform cooling unit; 51. Mounting sleeve; 52. Cooling shell; 53. Connecting pipe; 531. Outer pipe; 532. Inner pipe; 5321. First inner pipe; 5322. Buffer pipe; 5323. Second inner pipe; 533. Liquid outlet; 534. Connecting port; 54. Liquid outlet pipe; 55. Electric telescopic rod; 6. Lower cooling unit; 61. Lower cooling box; 611. Lower cooling cavity; 612. Refrigeration structure mounting cavity; 62. Lower cooling pipe. Detailed Implementation

[0033] 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.

[0034] like Figures 1 to 10 As shown, the technical solution adopted by this invention is as follows: a molding die for plastic products. The core lies in: a dynamically movable uniform cooling unit 5 through which coolant is introduced from both sides and mixed within the uniform cooling unit 5. During the cooling process, a constant temperature field is actively established in the vertical direction of the mold, achieving uniform cooling. Furthermore, as the uniform cooling unit 5 moves vertically, the cooling path lengths of the upper cooling pipe 42 and the lower cooling pipe 62 are changed, creating turbulence within the cooling pipes and improving cooling efficiency. This collaboratively solves the problems of product warping and internal stress caused by uneven cooling.

[0035] Specifically, a molding die for plastic products includes a mold support 1. A lower mold 22 is detachably mounted on the top of the mold support 1. An upper mold 21 is provided above the lower mold 22. The upper mold 21 is vertically slidably connected via guide posts 11 fixed on the mold support 1.

[0036] The output shaft of the external hydraulic cylinder is fixedly connected to the upper mold 21. The hydraulic cylinder is prior art and is not shown in the accompanying drawings. The upper mold 21 is driven to move vertically along the guide post 11 by the extension and retraction of the hydraulic cylinder, thereby realizing the mold closing or opening with the lower mold 22.

[0037] An injection structure 3 is mounted on the top of the upper mold 21. The output end of the injection structure 3 is connected to a pipe 31 that passes through the upper mold 21. The closing surface of the lower mold 22 is provided with a downwardly protruding second protruding mold core 221, and the closing surface of the upper mold 21 is provided with a downwardly protruding first protruding mold core 211. When the mold is closed, the first protruding mold core 211 enters the second protruding mold core 221, and a cavity that matches the shape of the plastic product is formed between them.

[0038] To achieve rapid and uniform cooling of the plastic product after injection molding, the mold also includes an upper cooling unit 4, a uniform cooling unit 5, and a lower cooling unit 6 arranged sequentially from top to bottom inside the mold support 1.

[0039] like Figure 4 As shown, the upper cooling unit 4 includes an upper cooling box 41, inside which is an annular upper cooling cavity 411. Multiple vertically arranged upper cooling pipes 42 are evenly fixed along the circumference of the bottom of the upper cooling box 41. The upper cooling pipes 42 are evenly distributed along the circumference of the upper cooling box 41. An upper cooling pipe mounting cavity 412 is provided on the upper cooling box 41. The upper cooling pipes 42 are installed in the upper cooling pipe mounting cavity 412 and communicate with it. The upper cooling pipe mounting cavity 412 and the upper cooling cavity 411 are connected through a connecting hole. A liquid pump is installed on the upper cooling pipe 42, controlling the flow rate of the coolant. The liquid pump is prior art and is not shown in the accompanying drawings. A refrigeration device is also installed inside the upper cooling box 41; the coolant, after being cooled by the refrigeration structure, flows into the upper cooling pipe 42 via the liquid pump.

[0040] The lower cooling unit 6 is located below the upper cooling unit 4. The lower cooling unit 6 includes a lower cooling box 61. The lower cooling box 61 contains a lower cooling cavity 611 and a refrigeration structure mounting cavity 612. The lower cooling cavity 611 stores coolant. A refrigeration device is installed in the refrigeration structure mounting cavity 612 to cool the coolant. Multiple lower cooling pipes 62 are evenly distributed along the circumference of the top of the lower cooling box 61. The lower cooling pipes 62 communicate with the lower cooling cavity 611. Each lower cooling pipe 62 corresponds one-to-one with an upper cooling pipe 42. Both the upper cooling pipe 42 and the lower cooling pipe 62 employ a corrugated pipe structure that can extend and retract vertically.

[0041] The uniform cooling unit 5 is located between the upper cooling unit 4 and the lower cooling unit 6.

[0042] The uniform cooling unit 5 includes a mounting sleeve 51, a cooling shell 52, a connecting pipe 53, a liquid outlet pipe 54, and an electric telescopic rod 55.

[0043] The mounting sleeve 51 is connected to the top of the lower cooling box 61 via multiple electrically operated telescopic rods 55 evenly distributed along the circumference. The mounting sleeve 51 can reciprocate vertically under the drive of the electrically operated telescopic rods 55.

[0044] Multiple connecting pipes 53 are provided and evenly distributed around the circumference of the mounting sleeve 51 and embedded in the mounting sleeve 51. Each connecting pipe 53 corresponds one-to-one with the upper cooling pipe 42 and the lower cooling pipe 62. The upper and lower ends of the connecting pipe 53 are connected to the corresponding upper cooling pipe 42 and lower cooling pipe 62 through sealing joints, respectively.

[0045] The cooling shell 52 is coaxially fixed inside the mounting sleeve 51, and the inner wall of the cooling shell 52 is in contact with the outer wall of the second protruding mold core 221. The liquid outlet pipe 54 connects the internal cavity of the cooling shell 52 with the lower cooling cavity 611.

[0046] The upper coolant flows into the connecting pipe 53 through the upper cooling pipe 42, and the lower coolant flows into the connecting pipe 53 through the lower cooling pipe 62. The coolant from both sides is collected and mixed in the connecting pipe 53, and then flows into the lower cooling chamber 611 from the outlet pipe 54.

[0047] It should be noted that the coolant flowing from the outlet pipe 54 into the lower cooling chamber 611 does not flow directly back into the lower cooling pipe 62, but is cooled by the refrigeration equipment and then pumped back into the lower cooling pipe 62.

[0048] Within the lower cooling chamber 611, the piping can be arranged using methods commonly found in the prior art, such as embedding a spiral pipe into the inner wall of the lower cooling chamber 611 with the axis of the spiral pipe aligned vertically. Coolant flowing from the outlet pipe 54 enters the spiral pipe, and during its flow within the spiral pipe, it is cooled by the refrigeration equipment before being pumped into the lower cooling pipe 62.

[0049] Alternatively, existing technologies can be used, such as arranging a parallel pipe array within the lower cooling chamber 611.

[0050] If a parallel pipe array is used, multiple parallel cooling pipes can be arranged horizontally inside the lower cooling chamber 611, with uniform spacing between each pipe. Each parallel cooling pipe is connected to the outlet pipe 54 through a distribution device. After the coolant flows out of the outlet pipe 54, it is evenly distributed to each parallel pipe through the distribution device, thereby increasing the heat exchange area and improving the heat dissipation efficiency.

[0051] The aforementioned pipe layout methods are all existing technologies and can be selected according to actual cooling requirements. The pipe structures described above are not shown in the accompanying drawings of this application.

[0052] like Figure 8 As shown, the connecting pipe 53 includes an outer pipe 531 and an inner pipe 532 coaxially sleeved inside the outer pipe 531.

[0053] The upper cooling pipe 42 is sealed to the first inner pipe 5321. There is a gap between the outer pipe 531 and the inner pipe 532. The lower cooling pipe 62 is sealed to the outer pipe 531. The lowermost inner pipe 532 is sealed, and the upper connection between the outer pipe 531 and the inner pipe 532 is also sealed, forming two chambers: an outer chamber and an inner chamber. The coolant in the lower cooling pipe 62 enters the outer chamber. The coolant in the upper cooling pipe 42 enters the inner chamber.

[0054] Furthermore, the inner tube 532 is formed by sequentially and coaxially fixing a first inner tube 5321, a tapered buffer tube 5322, and a second inner tube 5323, with the inner diameter of the first inner tube 5321 being larger than that of the second inner tube 5323. The unit structure composed of the first inner tube 5321, the buffer tube 5322, and the second inner tube 5323 can be configured in multiple sections as needed to enhance the fluid regulation effect. The outer diameter of the second inner tube 5323 is set to be smaller than that of the first inner tube 5321, thereby increasing the cross-sectional area of ​​the annular gap between the second inner tube 5323 section and the outer tube 531.

[0055] Multiple liquid outlet holes 533 are provided on the side wall of the second inner tube 5323. The liquid outlet holes 533 connect the inner cavity of the second inner tube 5323 with the gap between the outer tube 531 and the inner tube 532. The outer tube 531 has a connecting port 534 at the position corresponding to the second inner tube 5323, which is connected to the internal cavity of the cooling shell 52 through a connecting pipe.

[0056] During cooling, the coolant from the upper cooling pipe 42 first flows into the first inner pipe 5321 of the inner pipe 532, and then enters the smaller-diameter second inner pipe 5323 after passing through the buffer pipe 5322. According to the principles of fluid dynamics, the coolant velocity and pressure increase as it flows through this variable-diameter channel. This high pressure drives some of the coolant to be ejected from the outlet hole 533 on the side wall of the second inner pipe 5323. At the same time, due to the increased cross-sectional area and reduced flow resistance of the annular gap at the second inner pipe 5323, a low-pressure region is formed that facilitates fluid discharge, further promoting the smooth ejection of coolant from the inner pipe 532 into the annular gap through the outlet hole 533. At this moment, the coolant flowing into the annular gap from the lower cooling pipe 62 meets this jet flow and the two mix. The mixed, homogenized coolant is finally introduced into the cooling shell 52 through the connecting port 534, completing the heat exchange and homogenization process.

[0057] In other words, the connecting pipe 53 adopts a sleeve design with an inner pipe 532 and an outer pipe 531, and the inner pipe 532 has a variable diameter section. This structure utilizes the Venturi effect to accelerate the upper coolant and spray it out from the side wall hole, where it mixes violently with the lower coolant in the annular cavity, achieving efficient heat and mass exchange and outputting a uniformly heated coolant.

[0058] like Figure 9 and Figure 10 As shown, the electric telescopic rod 55 extends and retracts, causing the uniform cooling unit 5 to move vertically. When the uniform cooling unit 5 moves to a certain height of the mold, for example, when the electric telescopic rod 55 causes the uniform cooling unit 5 to be located in the middle region, the lengths of the upper cooling pipe 42 and the lower cooling pipe 62 are equal, the flow paths of the upper cooling pipe 42 and the lower cooling pipe 62 are the same, the temperature rise of the coolant is the same, and the temperature of the coolant flowing into the uniform cooling unit 5 is similar.

[0059] Because the electric telescopic rod 55 can control the vertical movement of the uniform cooling unit 5, the uniform cooling unit 5 can ensure uniform coolant temperature in the vertical direction during the cooling process, reducing the temperature difference of the coolant in the vertical direction during the cooling of the injection molded part. The specific uniform cooling process is as follows:

[0060] When the electric telescopic rod 55 extends, causing the uniform cooling unit 5 to move upward, the upper cooling pipe 42 is compressed and shortened. The coolant flowing through it experiences a smaller temperature rise due to the shorter flow path. At this time, the coolant temperature flowing from the upper cooling pipe 42 to the uniform cooling unit 5 is relatively low. Simultaneously, the lower cooling pipe 62 is stretched and elongated. The coolant in the lower cooling pipe 62 absorbs more heat due to the longer flow path, resulting in a larger temperature rise. At this time, the coolant temperature flowing from the lower cooling pipe 62 to the uniform cooling unit 5 is relatively high. At this point, the relatively low-temperature upper liquid and the relatively high-temperature lower liquid are mixed in the connecting pipe 53. After mixing in the uniform cooling unit 5, the temperature of the coolant is close to the temperature when the uniform cooling unit 5 is located in the middle region.

[0061] When the electric telescopic rod 55 retracts, causing the uniform cooling unit 5 to move downwards to the central region, the coolant flowing into the uniform cooling unit 5 from the upper cooling pipe 42 and the lower cooling pipe 62 has a similar temperature. As the uniform cooling unit 5 continues to move downwards, a mixing mode is formed between the relatively high-temperature upper liquid and the relatively low-temperature lower liquid, and the temperature of the mixture also approaches the value mentioned above for the central region.

[0062] Therefore, for any point in the vertical direction of the mold, when the uniform cooling unit 5 passes through it periodically, the temperature of the coolant it receives fluctuates slightly around a set average value. This dynamic, periodic cooling condition breaks the "position-temperature" binding relationship in traditional fixed pipeline systems, and performs forced temperature equalization on the mold in both time and space. This effectively controls the temperature gradient in the vertical direction of the mold within a very small range, suppressing warping and internal stress in plastic products caused by uneven cooling.

[0063] Furthermore, the electric telescopic rod 55 can drive the uniform cooling unit 5 to perform vertical reciprocating motion under the control of the controller. During this motion, slight and controllable mechanical vibrations are generated, which are transmitted to the plastic product that is cooling and shaping through the mold support 1 and the mold 2.

[0064] In traditional fixed cooling pipes, the coolant is mostly in a laminar flow state, forming a nearly static "thermal boundary layer" near the pipe wall, which becomes the main thermal resistance for heat transfer. The reciprocating motion of the uniform cooling unit 5 transmits vibration to the mold and cooling pipes, disturbing the coolant flow and effectively breaking down this thermal boundary layer. Vibration causes the low-temperature core fluid to flush the pipe wall more frequently, significantly reducing thermal resistance; at the same time, vibration injects additional kinetic energy into the fluid, promoting the transition from laminar to turbulent flow and improving heat transfer efficiency.

[0065] During the injection molding filling stage, the polymer chains are "frozen" in a non-equilibrium orientation state due to rapid cooling, storing a large amount of internal stress, which is the root cause of product warping and strength reduction. The micro-vibrations generated by the uniform cooling unit 5 are transmitted to the plastic product through the mold, providing additional energy to the frozen molecular chains, promoting their relaxation and rearrangement, and restoring them from an extended state to a more stable curled state. This relaxation process releases "relaxation heat" and enhances heat transfer within the melt, making the temperature field more uniform, effectively releasing residual stress, and suppressing warping deformation caused by uneven shrinkage.

[0066] During the pressure holding stage, the melt needs continuous feeding due to cooling and contraction. The periodic pressure fluctuations generated by the uniform cooling unit 5 create a "vibration pressure holding" effect, which pushes the melt to fill the micro-voids formed by contraction, reducing surface shrinkage marks and internal molecular orientation. At the same time, for areas with uneven wall thickness, vibration breaks up local heat accumulation, enhances internal convection of the melt, improves heat diffusion efficiency in thick-walled areas, eliminates local "hot spots," and achieves a more balanced cooling effect.

[0067] In use, this invention first uses an external hydraulic cylinder to drive the upper mold 21 to move vertically downwards along the guide post 11, completing the mold closing with the lower mold 22. During the mold closing process, the first protruding mold core 211 of the upper mold 21 enters the interior of the second protruding mold core 221 of the lower mold 22, forming a cavity that matches the shape of the plastic product. Subsequently, the injection structure 3 at the top of the upper mold 21 injects plastic material into the cavity through the pipe 31, completing the injection molding process.

[0068] After injection molding, the mold's cooling system is activated to achieve rapid and uniform cooling of the plastic product. Coolant in the upper cooling unit 4 flows through the upper cooling pipe 42, while coolant in the lower cooling unit 6 flows in from the lower cooling pipe 62. A uniform cooling unit 5 is located between the two, and its connecting pipe 53 is responsible for mixing the coolant from both the upper and lower cooling systems.

[0069] Inside the connecting pipe 53, the coolant first flows in from the first inner pipe 5321 of the inner pipe 532, then transitions through the buffer pipe 5322 before entering the smaller-diameter second inner pipe 5323, where the flow velocity and pressure increase. The high pressure forces some of the coolant to be ejected from the outlet hole 533 on the side wall of the second inner pipe 5323. Simultaneously, due to the increased cross-sectional area of ​​the annular gap at this location and reduced flow resistance, a low-pressure zone is formed, promoting mixing between the ejected flow and the coolant flowing in from the lower cooling pipe 62 within the annular gap. The mixed, homogeneous coolant is then introduced into the cooling shell 52 through the connecting port 534 for heat exchange with the mold.

[0070] The uniform cooling unit 5 is driven to move vertically by an electric telescopic rod 55, thereby changing the lengths of the upper cooling pipe 42 and the lower cooling pipe 62. As the unit moves, the flow path lengths of the upper and lower coolants change, resulting in temperature differences. This movement ensures that the temperature of the mixed coolant fluctuates slightly around an average value, thus achieving temperature uniformity in the vertical direction of the mold.

[0071] Furthermore, the electric telescopic rod 55, controlled by a controller, drives the uniform cooling unit 5 to move vertically reciprocatingly. This movement generates slight, controllable mechanical vibrations, which are transmitted to the cooling and shaping plastic product through the mold support 1 and the mold 2. This controlled micro-vibration provides kinetic energy to the molecular chains within the plastic melt, promoting their relaxation and effectively reducing residual internal stress caused by flow orientation and rapid cooling, thereby reducing the product's tendency to warp. Simultaneously, the vibration enhances heat conduction within the plastic, breaking up localized heat accumulation and helping to eliminate cooling differences caused by uneven wall thickness, resulting in more uniform overall cooling. Moreover, during the holding pressure stage, the periodic pressure fluctuations generated by the vibration help to promote melt shrinkage, thereby inhibiting the formation of shrinkage marks on the product surface and improving surface quality.

[0072] 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 molding die for plastic products, comprising a mold support (1), wherein a lower mold (22) is provided at the top of the mold support (1), and an upper mold (21) is provided above the lower mold (22) via a guide post (11) and slidably connected vertically, wherein an injection structure (3) is provided at the top of the upper mold (21); the mating surfaces of the lower mold (22) and the upper mold (21) are respectively provided with a second protruding mold core (221) and a first protruding mold core (211), forming a cavity when the mold is closed; characterized in that, Also includes: The upper cooling unit (4) includes an upper cooling box (41) and multiple vertical upper cooling pipes (42). The lower cooling unit (6) includes a lower cooling box (61) and multiple vertical lower cooling pipes (62). A uniform cooling unit (5) is located between the upper cooling unit (4) and the lower cooling unit (6), and includes a mounting sleeve (51), a cooling shell (52), and multiple connecting pipes (53); the mounting sleeve (51) is connected to the lower cooling box (61) through a driving mechanism and can be driven to move back and forth in the vertical direction; the two ends of the connecting pipes (53) are respectively connected to the upper cooling pipe (42) and the lower cooling pipe (62) through sealing joints; the cooling shell (52) is fixed to the inner side of the mounting sleeve (51) and contacts the outer wall of the second protruding mold core (221); The upper cooling pipe (42) and the lower cooling pipe (62) are corrugated pipes that can be vertically extended and retracted; The vertical movement of the uniform cooling unit (5) can change the length of the upper cooling pipe (42) and the lower cooling pipe (62), so that the upper and lower coolants flowing into the connecting pipe (53) will have a temperature difference due to the different flow paths and mix. The uniform cooling unit (5) is configured to perform vertical reciprocating movement, thereby generating micro-vibrations within the mold.

2. The molding die for plastic products according to claim 1, characterized in that, The connecting pipe (53) includes an outer pipe (531) and an inner pipe (532) coaxially disposed therein; the inner pipe (532) has a variable diameter section with decreasing diameter; the side wall of the variable diameter section has a liquid outlet hole (533); the outer pipe (531) has a communication port (534) corresponding to the position of the variable diameter section, which communicates with the cooling shell (52); the flow channel of the inner pipe (532) is connected to the upper cooling pipe (42), and the annular gap between the inner pipe (532) and the outer pipe (531) is connected to the lower cooling pipe (62).

3. A molding die for plastic products according to claim 2, characterized in that, The variable diameter section is composed of a first inner tube (5321) with a larger diameter, a tapered buffer tube (5322), and a second inner tube (5323) with a smaller diameter connected in sequence.

4. A molding die for plastic products according to claim 3, characterized in that, The unit structure consisting of the first inner tube (5321), the buffer tube (5322), and the second inner tube (5323) is multi-segment.

5. A molding die for plastic products according to claim 1, characterized in that, The driving mechanism consists of multiple electrically operated telescopic rods (55) evenly distributed along the circumference.

6. A molding die for plastic products according to claim 1, characterized in that, It also includes a liquid outlet pipe (54) that connects the internal cavity of the cooling shell (52) to the lower cooling cavity (611) of the lower cooling unit (6).

7. A molding die for plastic products according to claim 1, characterized in that, The inner wall of the cooling shell (52) is closely fitted with the outer wall of the second protruding mold core (221).

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