Multi-point uniform filling gate structure of thin-wall part injection mold

Abstract

The application discloses a multi-point uniform filling gate structure of a thin-wall part injection mold, which comprises an annular distribution cavity, a main runner assembly, at least four gate assemblies and a cavity; a spiral flow guide groove is formed in the inner wall of the annular distribution cavity, an inlet is arranged on the top wall, and a tangential outlet is arranged on the side wall; the main runner assembly is communicated with the inlet; the gate assembly comprises a variable cross-section gate insert and a short pipe channel, which can be replaced independently; a three-section flow channel structure is arranged in the gate insert, the inlet of the three-section flow channel structure is sealingly connected with the tangential outlet, the outlet of the three-section flow channel structure is connected with the cavity, and a micro pressure sensor is integrated at the tangential outlet. The application has the beneficial effects that: the melt is uniformly pressurized, stabilized and temperatureed, the tangential outlet uniformly distributes the melt, the gate insert, which can be replaced independently, is suitable for different specifications of thin-wall parts; the spiral cooling water channel and the micro pressure sensor are matched to realize accurate temperature control of the gate area and real-time monitoring of the melt pressure, and the purpose of uniform filling and good versatility is achieved.

Description

Technical Field

[0001] This invention relates to the field of injection mold technology, and more specifically to a multi-point uniform filling gate structure for a thin-walled injection mold. Background Technology

[0002] With the increasing demands for lightweight and precision products in industries such as electronic equipment, automotive parts, and medical devices, the application of thin-walled parts (typically less than 1 mm thick) is becoming increasingly widespread. The injection molding process for thin-walled parts faces technical challenges such as high melt flow resistance, difficulty in filling, rapid cooling, and susceptibility to warping. To address these issues, multi-point gating technology is widely adopted, which involves injecting melt into the mold cavity simultaneously or in a specific sequence through multiple gates to shorten the flow path, reduce injection pressure, and improve filling efficiency.

[0003] Thin-walled parts are widely used in electronics, automobiles, and home appliances due to their advantages such as light weight, compact structure, and low cost. However, during the injection molding process of thin-walled parts, due to the thin wall thickness (usually less than 2mm), the melt filling distance is long and the resistance is high, which easily leads to molding defects such as uneven filling, shrinkage marks, weld lines, and material shortages, seriously affecting product quality and service life.

[0004] Currently, most injection molds for thin-walled parts employ single-point or multi-point in-line gate designs. Single-point gates suffer from long filling distances, significant melt pressure losses, and uneven filling, making them particularly suitable for small thin-walled parts. However, they struggle to achieve uniform filling for large or complex thin-walled parts. While multi-point in-line gates can shorten the filling distance, they are prone to generating eddies during melt flow, resulting in uneven pressure distribution. Furthermore, the gate components are often integral, making it impossible to adjust flow resistance according to product specifications, leading to poor versatility. In addition, existing gate structures lack real-time monitoring of melt pressure and precise temperature control in the gate area, making it difficult to accurately adjust injection parameters and further exacerbating molding defects. Moreover, high mold maintenance costs and short service life fail to meet the demands of mass production. Summary of the Invention

[0005] The present invention aims to solve the problems of uneven filling and poor versatility mentioned in the background art, and provides a multi-point uniform filling gate structure for thin-walled injection molds with uniform filling and good versatility.

[0006] A multi-point uniform filling gate structure for a thin-walled injection mold includes an annular distribution cavity, a main runner assembly, at least four gate assemblies, and a cavity. The inner wall of the annular distribution cavity has a spiral guide groove, the top wall of the annular distribution cavity has a feed inlet, and the periphery of the annular distribution cavity has multiple tangential outlets. The main runner assembly is installed on the top of the annular distribution cavity, and its outlet is coaxially connected to the feed inlet. The gate assembly includes an independently replaceable variable cross-section gate insert and a short pipe channel, and the gate insert and the short pipe channel are detachably sealed. The inlet end of the gate assembly is arranged along the circumference of the annular distribution cavity, the inlet end of the gate assembly is sealed to the tangential outlets, and the outlet end of the gate assembly is connected to the cavity.

[0007] By setting up an annular distribution cavity with spiral guide channels, the melt flowing in from the central inlet is forced to flow along a spiral path within the annular cavity. In traditional multi-point casting, after the melt enters the annular cavity from the central inlet, it often flows preferentially to the outlet closest to the inlet due to inertia and the shortest path principle, resulting in insufficient pressure at the far outlet (i.e., the "preferential effect"). The spiral guide channels run through the entire inner wall of the annular cavity, forming an active conveying channel. This ensures that every part of the melt in the cavity moves forward slowly but continuously, achieving pressure equalization and stabilization. The uniform temperature distribution reduces shear heat generation and promotes uniform pressure transmission. The tangential outlets are arranged circumferentially to achieve uniform flow of melt to each gate component, avoiding local overfilling or underfilling caused by single-point feeding. The independently replaceable gate inserts can adapt to the production needs of thin-walled parts of different specifications, improving the versatility and maintenance convenience of the mold. The overall structure is reliably sealed, and the components fit tightly together, effectively improving the molding quality of thin-walled parts, reducing the probability of defects such as shrinkage marks and weld lines, and improving injection molding production efficiency, achieving the goal of uniform filling and good versatility.

[0008] Preferably, the annular distribution cavity is a hollow, circumferentially closed annular pressure device with a circular or elliptical cross-section. The volume of the annular distribution cavity is designed to be 15% to 20% of the single injection volume. As the buffer and distribution core of the melt, the annular distribution cavity adopts a hollow, closed structure, communicating with the outside only through the inlet and tangential outlet, ensuring the sealing and flow stability of the melt within the cavity. The circular or elliptical cross-section design reduces resistance during melt flow and avoids melt stagnation caused by local dead zones. The volume design of 15% to 20% of the single injection volume allows the melt to quickly fill the cavity and establish stable pressure after entering the annular distribution cavity, and then evenly distribute to each gating assembly through the tangential outlet. This ensures both uniform distribution and prevents the melt from staying in the cavity for too long and cooling and solidifying, ensuring the continuity and stability of the injection molding process.

[0009] Preferably, the annular distribution cavity is an integral structure, the feed inlet is a through hole opened at the center of the top wall of the annular distribution cavity, and the tangential outlet is a plurality of through holes evenly opened along the circumference on the outer side wall of the annular distribution cavity. The top feed inlet and the tangential outlet are the only external openings of the annular distribution cavity. The annular distribution cavity is an integral structure, which improves its structural strength and sealing performance, avoids melt leakage problems caused by split structures, and reduces processing and assembly errors, ensuring the accuracy of melt distribution. On the other hand, the inlet is located at the center of the top wall and is coaxially connected to the outlet of the main runner component, ensuring that the melt enters the annular distribution cavity vertically, reducing pressure loss at the inlet. The tangential outlets are evenly distributed circumferentially and are the only external outlets of the annular distribution cavity (other than the inlet). This allows the melt to be evenly distributed tangentially to each gate component after being guided by the spiral guide groove in the annular distribution cavity, avoiding filling defects caused by uneven melt distribution. At the same time, the integral structure facilitates mold processing, assembly, and subsequent maintenance, reducing the mold failure rate.

[0010] Preferably, the main runner assembly includes a replaceable main runner sprue sleeve, which is fitted into the inlet and connected by a sealing ring. The inner hole of the sprue sleeve forms the main runner channel, and its shape is conical. The sprue sleeve of the main runner assembly is fitted into the inlet of the annular distribution chamber. The sealing ring fills the gap between the sprue sleeve and the inlet to achieve a sealed connection and prevent melt leakage. The conical design of the inner hole of the sprue sleeve adapts to the structure of the injection molding machine nozzle, facilitating the smooth entry of the melt from the injection molding machine nozzle into the main runner channel. At the same time, the conical structure reduces the resistance during melt flow and avoids pressure loss. When it is necessary to change the injection molding material or product specifications, the sprue sleeve can be directly disassembled and replaced without disassembling the entire main runner assembly, improving mold adjustment efficiency and reducing maintenance costs.

[0011] Preferably, the gate insert is cylindrical in shape, with a three-section flow channel structure running through it along the axial direction. In order of melt flow direction, the three sections are: an inlet conical section, a middle cylindrical section, and an outlet conical section. The large-diameter end of the inlet conical section faces the annular distribution cavity, and the small-diameter end faces the middle cylindrical section, with a taper of 5° to 15°, used to smoothly introduce the melt from the tangential outlet. The middle cylindrical section is a damping section with a smooth cylindrical inner wall, a diameter of 0.5mm to 3.0mm, and a length of 2.0mm to 10.0mm. Its diameter and length are adjusted to precisely control the flow resistance of the gate assembly. The large-diameter end of the outlet conical section faces the mold cavity, and the small-diameter end faces the middle cylindrical section, with a taper of 10° to 30°, used to accelerate the injection of the melt into the mold cavity. The gate insert has a cylindrical structure with three internal flow channels running along the axis. After the melt enters the gate assembly from the tangential outlet of the annular distribution cavity, it first passes through the inlet conical section (with the large diameter end facing the annular distribution cavity) to achieve a smooth transition and guide the melt, reducing pressure loss and eddies at the inlet. The melt then enters the middle cylindrical section, which has a smooth cylindrical surface. By adjusting its diameter and length, the melt flow resistance is changed to ensure that the melt flow rate and pressure of each gate assembly are consistent, achieving uniform flow distribution. Finally, the melt passes through the outlet conical section (with the large diameter end facing the cavity), where the flow channel cross-section gradually expands, achieving accelerated melt injection and rapid filling of the cavity, meeting the requirements of thin-walled parts for filling speed and uniformity. When it is necessary to adjust the flow resistance to adapt to different products, the gate insert can be directly replaced without adjusting the entire gate assembly.

[0012] Preferably, the end of the short pipe channel furthest from the gate insert is sealed to the tangential outlet, and its central axis coincides with or forms an angle of 0° to 10° with the circumferential tangent of the annular distribution cavity at the connection point. When the melt flows out of the tangential outlet of the annular distribution cavity, it can flow smoothly along the axial direction of the short pipe channel, avoiding pressure loss and eddies caused by sudden changes in the melt flow direction; the sealed connection design ensures that the melt will not leak from the connection point, ensuring stable pressure of the melt in the short pipe channel, and thus ensuring that the melt can be injected into the cavity with stable pressure and flow rate after passing through the gate insert, achieving uniform filling of thin-walled parts.

[0013] Preferably, a spiral cooling channel is arranged around the outer circular surface of the gate insert, near the exit conical section. This spiral cooling channel is a spiral groove directly machined onto the outer circular surface of the insert, forming a closed cooling circuit with the external water-cooling sleeve of the gate insert. This allows for independent and rapid temperature control of the gate area. The spiral groove on the outer circular surface of the gate insert, when installed, forms a closed spiral cooling channel with the external water-cooling sleeve. During injection molding, cooling water enters the spiral cooling channel through the water-cooling sleeve, flows along the spiral groove, and exchanges heat with the gate insert, quickly removing heat from the gate area and achieving temperature control. By adjusting the flow rate and temperature of the cooling water, the temperature of the gate area can be precisely controlled, ensuring the melt maintains appropriate fluidity at the gate, avoiding gate blockage due to excessively rapid melt cooling or molding defects caused by uneven cooling. Furthermore, after injection molding, the gate can be quickly cooled, facilitating product demolding and improving production efficiency.

[0014] Preferably, a micro-guide ridge is provided at the junction of the main wall of the cavity and the rib structure, and the extension direction of the micro-guide ridge forms a 45° angle with the main flow direction of the melt. When the melt is injected into the cavity from the gating assembly, it flows rapidly along the main wall of the cavity. When it reaches the junction of the main wall of the cavity and the rib structure, the melt flow is easily obstructed due to the small cross-section of the rib structure, resulting in insufficient filling. The 45° angle between the extension direction of the micro-guide ridge and the main flow direction of the melt can guide the flowing melt, smoothly introduce the melt into the rib area, avoid the melt from generating eddies or stagnation at the junction, ensure that the rib area can be fully and uniformly filled, reduce the pressure loss of the melt at the junction, ensure the uniformity of the overall filling of the cavity, and improve the product molding quality.

[0015] Preferably, at least one micro-sump is provided at the predicted boundary of the melt filling area affected by two adjacent gate assemblies within the cavity. The micro-sump is located directly below the melt convergence area of ​​the flow channel formed by two adjacent micro-guide ridges. During injection molding, the melt injected by the two adjacent gate assemblies flows in their respective directions within the cavity and eventually meets at the predicted boundary. The micro-sump is located at this boundary to collect excess melt and weld waste generated when the melts from the two directions meet, preventing these wastes from forming obvious weld lines on the product surface. At the same time, the micro-sump acts as a buffer, alleviating the pressure impact when the melts from the two directions meet, reducing melt backflow, ensuring that the melt can fully fill the cavity, and avoiding defects such as shrinkage marks and bubbles caused by pressure impact. After injection molding, the waste in the micro-sump is integrally formed with the product and can be removed by simple trimming after demolding without affecting the normal use of the product.

[0016] Preferably, a sensor mounting blind hole is provided on the wall surface of the tangential outlet, and a miniature pressure sensor is embedded in the sensor mounting blind hole. The miniature pressure sensor is a piezoresistive or capacitive sensor based on MEMS technology, with a diameter ≤2.0mm and a measurement range of 0-50MPa. Its pressure sensing surface is flush with the inner wall surface of the tangential outlet, and it is used to monitor the melt pressure fluctuation at the inlet of the gating assembly in real time and in situ. A blind hole for sensor mounting is created on the wall of the tangential outlet. A miniature pressure sensor (piezoresistive or capacitive) is embedded in the blind hole, with its sensing surface flush with the inner wall of the tangential outlet. This ensures that the melt flows directly onto the sensing surface, enabling in-situ pressure monitoring. During injection molding, the melt flows through the tangential outlet, generating pressure on the sensor's sensing surface. The sensor converts the pressure signal into an electrical signal, which is transmitted to the control system in real time. The control system determines whether the feed pressure of each gate component is uniform based on the fluctuation of the pressure signal. If abnormal pressure occurs, the injection parameters (such as injection speed and melt temperature) can be adjusted in time to ensure stable melt pressure, thereby achieving uniform filling of thin-walled parts. This also facilitates timely detection of mold leaks, runner blockages, and other faults by operators, reducing production losses.

[0017] The beneficial effects of this invention are as follows: the spiral guide groove of the annular distribution cavity optimizes the melt flow state, reduces eddies and pressure loss, and the tangential outlet is evenly distributed along the circumference to achieve uniform distribution of melt to each gate component; the independently replaceable gate insert, through the three-section flow channel structure, achieves smooth melt introduction, resistance control and accelerated spraying, adapting to the molding needs of thin-walled parts of different specifications and materials, improving mold versatility and reducing maintenance costs; the spiral cooling water channel in the gate area achieves independent and rapid temperature control, ensuring melt fluidity and cooling uniformity; the micro pressure sensor enables real-time, in-situ monitoring of melt pressure, allowing for timely adjustment of injection parameters and improving molding stability; and it achieves the goal of uniform filling and good versatility. Attached Figure Description

[0018] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic diagram of a spiral guide channel; Figure 3 Installation sectional view of the main channel assembly and annular distribution cavity Figure 4 This is a sectional view of the gate insert; Figure 5 This is a schematic diagram of the micro-guide ridges and micro-storage pits inside the mold cavity; Figure 6 Schematic diagram of sensor installation location.

[0019] Among them, 1. Annular distribution cavity, 11. Spiral guide groove, 12. Inlet, 13. Tangential outlet, 14. Mounting blind hole, 15. Pressure sensor, 2. Main runner assembly, 21. Sprue sleeve, 22. Sealing ring, 3. Sprue assembly, 31. Sprue insert, 311. Inlet conical section, 312. Intermediate cylindrical section, 313. Outlet conical section, 314. Spiral cooling water channel, 32. Short pipe channel, 4. Cavity, 41. Micro-guide ridge, 42. Micro-storage pit. Detailed Implementation

[0020] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to the embodiments.

[0021] In the description of this invention, it should be noted that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer" and "vertical" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and 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 limiting this invention.

[0022] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" 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 direct connection or an indirect connection through an intermediate medium; or they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0023] Furthermore, in the description of this invention, unless otherwise stated, "multiple", "multiple groups", and "multiple roots" mean two or more.

[0024] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments; Example 1: Eight-point casting system like Figure 1 As shown, a multi-point uniform filling gate structure for a thin-walled injection mold includes an annular distribution cavity 1, a main runner assembly 2, eight gate assemblies 3 (not evenly distributed around the entire circumference) and a cavity 4.

[0025] The annular distribution cavity 1 is a hollow, circumferentially closed annular pressure device with a circular cross-section, an outer diameter of 80 mm, an inner diameter of 60 mm, and a height of 30 mm. The volume of the annular distribution cavity 1 is 18% of the single injection volume, used to smooth pressure fluctuations and ensure that the melt pressure at each gate assembly 3 is basically consistent.

[0026] like Figure 2 As shown, the inner wall of the annular distribution cavity 1 is provided with a spiral guide groove 11. The spiral guide groove 11 has a depth of 1.5 mm, a width of 3 mm, a pitch of 10 mm, and a spiral helix angle of 18°. The function of the spiral guide groove 11 is to generate swirling flow when the melt flows along the annular distribution cavity 1, promoting melt mixing and pressure equalization. A feed inlet 12 with a diameter of 20 mm is provided at the center of the top wall of the annular distribution cavity 1. Eight tangential outlets 13 (non-circumferentially distributed) are provided on the periphery of the annular distribution cavity 1, with the center of the annular distribution cavity 1 as the origin: Y-axis: Front-back direction → No outlet; X-axis: Left-right direction → Four tangential outlets 13 are arranged on each side. The angles of the four outlets on the right are: +22.5°, +67.5°, -22.5°, and -67.5°; the angles of the four outlets on the left are: 180°±22.5° and 180°±67.5°, i.e., 157.5°, 112.5°, 202.5°, and 247.5°. No outlets are arranged in the front-back direction (near the Y-axis). The diameter of the tangential outlets 13 is 8mm, and the included angle between adjacent outlets is 45°. All eight outlets are tangentially oriented, with the direction consistent with the tangent of the annular cavity circumference. The melt on both sides swirls in the same direction, preventing collisions and resulting in more balanced pressure.

[0027] like Figure 3 As shown, the main runner assembly 2 is installed on top of the annular distribution cavity 1, and includes a main runner sprue sleeve 21 and a sealing ring 22. The main runner sprue sleeve 21 is fitted into the inlet 12, and the two are sealed together by the sealing ring 22. The inner hole of the main runner sprue sleeve 21 forms the main runner channel, which is conical in shape with an inlet diameter of 12mm, an outlet diameter of 8mm, and a taper of 3°. The main runner sprue sleeve 21 is designed to be replaceable for easy maintenance and replacement.

[0028] The gate assembly 3 includes a replaceable gate insert 31 and a short pipe channel 32, which are detachably and sealed together. The end of the short pipe channel 32 furthest from the gate insert 31 is sealed to the tangential outlet 13, and its central axis coincides with the circumferential tangent of the annular distribution cavity 1 at the connection point. The short pipe channel 32 has a length of 15 mm, an inner diameter of 6 mm, and an outer diameter of 10 mm.

[0029] like Figure 4 As shown, the gate insert 31 is cylindrical in shape, with a diameter of 12 mm and a length of 25 mm. Its interior is provided with a three-section flow channel structure along the axial direction, which are arranged in the following order according to the melt flow direction: inlet conical section 311, middle cylindrical section 312 and outlet conical section 313.

[0030] The large-diameter end of the inlet conical section 311 faces the annular distribution cavity 1. The large diameter is 6 mm, the small diameter is 2 mm, the taper is 10°, and the length is 8 mm. It is used to smoothly introduce the melt from the tangential outlet 13 and reduce flow disturbance.

[0031] The intermediate cylindrical section 312 is a damping section with a smooth cylindrical inner wall, a diameter of 1.5 mm, and a length of 5 mm. All eight sections are identical to ensure that the flow rates on the left and right sides are strictly equal. By adjusting the diameter and length of the intermediate cylindrical section 312, the flow resistance of the gating assembly 3 can be precisely controlled, achieving flow balance among the gating assemblies 3.

[0032] The large-diameter end of the outlet tapered section 313 faces the cavity 4. The large diameter is 2mm, the small diameter is 0.8mm, the taper is 20°, and the length is 12mm. It is used to accelerate the injection of melt into the mold cavity 4 and improve the filling efficiency.

[0033] On the outer circumferential surface of the gate insert 31, near the outlet conical section 313, a spiral cooling channel 314 is arranged around it. The spiral cooling channel 314 is a spiral groove directly machined on the outer circumferential surface of the gate insert 31, with a depth of 1.2 mm, a width of 2 mm, a pitch of 4 mm, and a helix angle of 15°. The spiral cooling channel 314 cooperates with the water-cooling sleeve outside the gate insert 31 to form a closed cooling circuit. The cooling medium is water, with a flow rate of 2 L / min, used to achieve independent and rapid temperature control of the gate area. By precisely controlling the temperature of the gate area, the viscosity and fluidity of the melt can be effectively controlled, improving the filling quality.

[0034] like Figure 5 As shown, at the junction of the main wall of cavity 4 and the rib structure, a micro-guide rib 41 is provided. The height of the micro-guide rib 41 is 0.15mm, the width is 0.3mm, and the extension direction is at a 45° angle with the main flow direction of the melt. The function of the micro-guide rib 41 is to guide the flow of the melt, reduce eddies and stagnation, and improve the filling effect.

[0035] At least one micro-sump pit 42 is provided at the predicted boundary of the melt filling area affected by two adjacent gating assemblies 3 within the cavity 4, and is located directly below the melt confluence area of ​​the flow channel formed by two adjacent micro-guide ridges 41. The micro-sump pit 42 has a diameter of 2 mm and a depth of 0.5 mm. The function of the micro-sump pit 42 is to provide additional melt reserve at the melt front confluence, avoid weld line defects caused by direct collision of melt fronts, and improve weld line strength.

[0036] like Figure 6As shown, a sensor mounting blind hole 14 is provided on the wall of the tangential outlet 13. A miniature pressure sensor 15 is embedded within the sensor mounting blind hole 14. The miniature pressure sensor 15 is a piezoresistive sensor based on MEMS technology, with a diameter of 1.8 mm, a measurement range of 0-50 MPa, a measurement accuracy of ±0.1 MPa, and a response time of 1 ms. The pressure-sensing surface of the miniature pressure sensor 15 is flush with the inner wall of the tangential outlet 13, and is used for real-time, in-situ monitoring of melt pressure fluctuations at the inlet of the gating assembly 3. Through pressure monitoring data, closed-loop control of process parameters can be achieved, improving the stability of molding quality.

[0037] The working process of this invention is as follows: The injection molding machine screw pushes the molten plastic through the main runner sprue sleeve 21 into the annular distribution chamber 1. The melt first impacts the top wall of the annular chamber and spreads circumferentially, then is forced into the spiral guide channel 11. Guided by the spiral guide channel 11, the melt rotates and flows circumferentially along the annular chamber. During this process, melts from different flows and directions are fully mixed, and the pressure and temperature tend to be uniform. After homogenization by the spiral path, the melt flows out from the tangential outlets 13 that are symmetrically distributed circumferentially on both sides.

[0038] The melt enters the gate assembly 3. First, the melt passes through the short pipe channel 32 and enters the inlet conical section 311 (10° taper) of the gate insert 31, where it is smoothly introduced. Then, the melt passes through the intermediate cylindrical section 312, which serves as a damping section. Its diameter and length have been precisely calculated and verified through trial molding to balance the additional flow resistance caused by the complex structure at the far end of the cavity 4. Finally, the melt is accelerated and sprayed into the cavity 4 through the outlet conical section 313 (20° taper). The shear heat causes the temperature of the melt at the leading edge to rise slightly, ensuring perfect filling of the ultra-thin wall area.

[0039] Throughout the injection molding process, a miniature pressure sensor 15 (MEMS piezoresistive type, 1.5mm in diameter) installed on the wall of the tangential outlet 13 monitors the pressure fluctuations at the inlet of each gate assembly 3 in real time. When an abnormal pressure curve of a certain gate assembly 3 is detected (such as rising too fast or too slow), the engineer can replace the gate insert 31 with the corresponding damping section size in the next production run until all sensors display pressure curves with consistent heights during the filling stage, thereby achieving true uniform filling.

[0040] Injection Molding Preparation: Based on the specifications of the thin-walled shell, select the appropriate main runner sprue bushing 21 and variable cross-section sprue insert 31. After installation, check the sealing performance of each component, and debug the miniature pressure sensor 15 and cooling system to ensure normal operation of the equipment. Heat the injection molding material (ABS plastic) to 220°C and melt it into a molten body.

[0041] Melt distribution: The injection molding machine nozzle injects the melt into the sprue sleeve 21 of the main runner assembly 2, and smoothly enters the feed port 12 of the annular distribution cavity 1 through the conical main runner channel; under the guidance of the spiral guide groove 11 of the annular distribution cavity 1, the melt flows smoothly along the inner wall of the annular cavity to achieve pressure buffering and uniform distribution, and then enters the corresponding sprue assembly 3 through 8 tangential outlets 13.

[0042] Melt flow guidance and acceleration: After entering the gate assembly 3, the melt is smoothly introduced through the inlet conical section 311, then through the intermediate cylindrical section 312 (with precise control of flow resistance), and finally accelerated and sprayed through the outlet conical section 313, injecting into the cavity 4 with a stable flow rate and pressure; the short pipe channel 32 coincides with the tangential direction of the tangential outlet 13 to ensure smooth melt flow without pressure changes.

[0043] Cavity 4 filling and temperature control: After the melt is injected into cavity 4, it smoothly fills the rib area under the guidance of the micro-guide rib 41 to avoid material shortage; the melt of two adjacent gate components 3 meets at the predicted junction, and excess melt and welding waste are collected by the micro storage pit 42; at the same time, the cooling water in the spiral cooling channel 314 flows continuously to perform real-time temperature control on the gate area to ensure uniform cooling of the melt and avoid gate marks and product deformation.

[0044] Pressure monitoring and parameter adjustment: The miniature pressure sensor 15 monitors the melt pressure at the inlet of each gate component 3 in real time and transmits the pressure signal to the control system. If pressure fluctuations occur (such as excessively high or low pressure at a certain gate), the control system adjusts the injection speed (currently set to 50 mm / s) and injection pressure (currently set to 30 MPa) in a timely manner to ensure consistent pressure at each gate and achieve uniform filling.

[0045] Demolding and post-processing: After injection molding, the cooling system continues to work for 5 seconds to ensure that the product is fully cooled; then the mold is opened, and the product and the waste in the micro storage pit 42 are demolded together. After trimming the waste, a qualified thin-walled shell product is obtained. Implementation effect

[0046] Using the technical solution of this embodiment, injection molding experiments were conducted on rectangular thin-walled parts made of ABS material. The experimental results show that: (1) The uniformity of filling is significantly improved, and the filling time difference between different areas is controlled within 4%, which is far better than the 18% of the traditional technology. The position and shape of the weld line are effectively controlled, and the weld line strength is increased by 25%.

[0047] (2) The injection pressure is reduced. Under the premise of ensuring the filling quality, the injection pressure is reduced from the traditional 120MPa to 95MPa, a reduction of 20.8%, and the energy consumption is reduced accordingly.

[0048] (3) Improved molding quality, with a 50% reduction in warpage and a significant improvement in dimensional accuracy. Improved surface quality, with no obvious flow marks or bubbles.

[0049] (4) Improved process stability: Closed-loop control is achieved through pressure monitoring data, reducing the fluctuation range of process parameters by 60% and increasing the product qualification rate from 92% to 98%.

[0050] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications and equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A multi-point uniform filling gate structure for a thin-walled injection mold, comprising an annular distribution cavity (1), a main runner assembly (2), at least four gate assemblies (3), and a cavity (4), characterized in that, The inner wall of the annular distribution cavity (1) is provided with a spiral guide groove (11), the top wall of the annular distribution cavity (1) is provided with a feed inlet (12), and the periphery of the annular distribution cavity (1) is provided with multiple tangential outlets (13). The main channel assembly (2) is installed on the top of the annular distribution cavity (1), and its outlet is coaxially connected with the inlet (12). The gate assembly (3) includes a replaceable variable cross-section gate insert (31) and a short pipe channel (32). The gate insert (31) and the short pipe channel (32) are detachably sealed. The inlet end of the gating assembly (3) is arranged along the circumference of the annular distribution cavity (1), the inlet end of the gating assembly (3) is sealed to the tangential outlet (13), and the outlet end of the gating assembly (3) is connected to the cavity (4).

2. The multi-point uniform filling gate structure for a thin-walled injection mold according to claim 1, characterized in that, The annular dispensing cavity (1) is a hollow, circumferentially closed annular pressure device with a circular or elliptical cross-section. The volume of the annular dispensing cavity (1) is designed to be 15% to 20% of the single injection volume.

3. The multi-point uniform filling gate structure for a thin-walled injection mold according to claim 2, characterized in that, The annular distribution cavity (1) is an integral structure. The feed inlet (12) is a through hole opened in the center of the top wall of the annular distribution cavity (1). The tangential outlet (13) is a plurality of through holes evenly opened in the circumferential direction on the outer side wall of the annular distribution cavity (1). The top feed inlet (12) and the tangential outlet (13) are the only external openings of the annular distribution cavity (1).

4. The multi-point uniform filling gate structure for a thin-walled injection mold according to claim 1, characterized in that, The main runner assembly (2) includes a replaceable main runner sprue sleeve (21), which is fitted into the inlet (12) and connected by a sealing ring (22). The inner hole of the sprue sleeve (21) forms the main runner channel, which is conical in shape.

5. The multi-point uniform filling gate structure for a thin-walled injection mold according to claim 1, characterized in that, The gate insert (31) is cylindrical in shape, and a three-section flow channel structure is provided inside along the axial direction. According to the melt flow direction, it is as follows: inlet conical section (311), middle cylindrical section (312) and outlet conical section (313). The large-diameter end of the inlet conical section (311) faces the annular distribution cavity (1), and the small-diameter end faces the middle cylindrical section (312), with a taper of 5° to 15°, for smoothly introducing the melt from the tangential outlet (13); The intermediate cylindrical section (312) is a damping section with a smooth cylindrical surface on its inner wall. Its diameter is 0.5 mm to 3.0 mm and its length is 2.0 mm to 10.0 mm. The flow resistance of the gate assembly (3) can be precisely controlled by adjusting its diameter and length. The large-diameter end of the outlet conical section (313) faces the cavity (4), and the small-diameter end faces the middle cylindrical section (312). The taper is 10° to 30°, which is used to accelerate the injection of melt into the mold cavity (4).

6. The multi-point uniform filling gate structure for a thin-walled injection mold according to claim 1, characterized in that, The end of the short pipe channel (32) away from the gate insert (31) is sealed to the tangential outlet (13), and its central axis coincides with or forms an angle of 0° to 10° with the circumferential tangent direction of the annular distribution cavity (1) at the connection point.

7. The multi-point uniform filling gate structure for a thin-walled injection mold according to claim 5, characterized in that, On the outer circular surface of the gate insert (31), near the outlet conical section (313), a spiral cooling water channel (314) is arranged around it. The spiral cooling water channel (314) is a spiral groove directly machined on the outer circular surface of the insert. It cooperates with the water-cooling sleeve outside the gate insert (31) to form a closed cooling circuit, which is used to achieve independent and rapid temperature control of the gate area.

8. The multi-point uniform filling gate structure for a thin-walled injection mold according to claim 1, characterized in that, At the junction of the main wall of the cavity (4) and the rib structure, a micro-flow guiding ridge (41) is provided, and the extension direction of the micro-flow guiding ridge (41) forms a 45° angle with the main flow direction of the melt.

9. The multi-point uniform filling gate structure for a thin-walled injection mold according to claim 8, characterized in that, At least one micro storage pit (42) is provided at the predicted boundary of the melt filling area affected by two adjacent gate assemblies (3) in the cavity (4). The micro storage pit (42) is located directly below the melt confluence area of ​​the flow channel formed by two adjacent micro guide ridges (41).

10. The multi-point uniform filling gate structure for a thin-walled injection mold according to claim 1, characterized in that, A sensor mounting blind hole (14) is provided on the wall of the tangential outlet (13). A miniature pressure sensor (15) is embedded in the sensor mounting blind hole (14). The miniature pressure sensor (15) is a piezoresistive or capacitive sensor based on MEMS technology. Its diameter is ≤2.0mm and its measurement range is 0-50MPa. Its pressure sensing surface is flush with the inner wall of the tangential outlet (13). It is used to monitor the melt pressure fluctuation at the inlet of the gating assembly (3) in real time and in situ.

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