Automobile sheet metal, threshold and door sheet metal connecting structure and threshold assembly injection molding process

Abstract

The present application relates to the field of automobile, especially to automobile body sheet metal assembly, door sill assembly and door sheet metal assembly and connecting structure thereof, the door sill assembly adopts the combined installation mode of plastic buckle + screw structure, can quickly realize the installation and replacement of door sill assembly, is convenient for later maintenance, and can be repeatedly disassembled and used. The door sill assembly is an injection molded part, which meets the length and modeling requirements of large size vehicles, the connection between the door sheet metal assembly and the door sill assembly is arranged in a V-shaped shielding mode, avoiding the problem of exposed parting line, the bottom of the door sill assembly is provided with a plurality of easy-to-bend turnover lugs, the easy-to-bend turnover lugs are fixed in the inner side of the automobile body sheet metal assembly through screws, solving the problem that the bottom of the door sill assembly exceeds the automobile body sheet metal assembly and cannot be fixed, and the energy absorption structure is designed in the door sill assembly to improve the rigidity of the bottom of the door and the collision safety.

Description

Technical Field

[0001] This invention relates to the automotive field, and more particularly to automotive sheet metal, door sills and door sheet metal connection structures, and door sill assembly injection molding process. Background Technology

[0002] As the market share of new energy vehicles increases year by year, the automotive industry is constantly raising its requirements for the appearance and structural performance of vehicle body exterior products. As an exterior decorative part and door protection part of the car body, the door sill assembly is widely used in various types of vehicles, especially in large-sized vehicles such as SUVs and MPVs. In order to improve the appearance, the overall length of the door sill assembly is constantly increasing and the exposed surface is also continuously enlarging.

[0003] However, the existing connection structure between automotive sheet metal and door sill assemblies has many technical defects: First, the installation of door sill assemblies often requires the disassembly of door or chassis components, and the fixing method is simple, cumbersome, and inconvenient for later maintenance; Second, the screw fixing points are poorly designed, and when people step on the door sill when getting in or out of the car, the door sill assembly is prone to flipping or falling off, affecting safety; Third, the parting line at the joint between the door sill assembly and the door sheet metal is directly exposed, which not only affects the appearance of the car body, but also leads to poor parting line processing quality and a lower product qualification rate; Fourth, the bottom of the large door sill assembly is exposed beyond the boundary of the internal sheet metal of the car body, making it impossible to achieve effective fixing and resulting in loose connections; Fifth, there is no special energy-absorbing structure on the inside of the door sill assembly, so the door sill is prone to breakage and intrusion into the passenger compartment in the event of a collision, resulting in poor passive safety, while using metal brackets to improve rigidity and energy absorption would increase costs and vehicle weight; Sixth, the lower part of the door sill assembly has insufficient rigidity, and it is prone to loosening and denting when pressed, resulting in a poor user experience. Seventh, for long-threshold parts, the following issues arise during the injection molding process: uneven filling, temperature difference during cooling, and warping during demolding.

[0004] Therefore, it is necessary to provide automotive sheet metal, door sill and door sheet metal connection structure and door sill assembly injection molding process to solve the above technical problems. Summary of the Invention

[0005] To solve the above-mentioned technical problems, the present invention provides automotive sheet metal, door sill and door sheet metal connection structure and door sill assembly injection molding process.

[0006] The present invention provides an automotive sheet metal, sill, and door sheet metal connection structure, including an automotive body sheet metal component, a sill assembly, and a door sheet metal component. The sill assembly is installed on the outside of the automotive body sheet metal component by a plurality of screws. The sill assembly is an injection molded part, adapted to the length and styling requirements of large-size vehicles. The bottom of the sill assembly is provided with a plurality of easily bendable and flip-up brackets, which are fixed to the inside of the automotive body sheet metal component by screws, solving the problem that the bottom of the sill assembly cannot be fixed if it exceeds the body sheet metal. The connection between the door sheet metal component and the sill assembly is arranged in a V-shape to avoid the problem of exposed parting lines.

[0007] As a further improvement of the present invention, the door sill assembly is provided with a mating part near the bottom of the door sheet metal component. The mating part is adapted to the bottom contour of the door sheet metal component, thereby improving the sealing performance and structural fit of the two.

[0008] As a further improvement of the present invention, a foam pad is fixed to the inner side of the door sill assembly at the connection between the easily bendable flip-up bracket and the door sill assembly by a metal clip. The foam pad is an elastic energy-absorbing component that can effectively absorb collision energy when the door is involved in a collision, thus preventing the door sill assembly from breaking directly or intruding into the passenger compartment.

[0009] As a further improvement of the present invention, the rigidity of the foam pad near the automotive body sheet metal component is increased. Specifically, a support protrusion can be added to the side of the foam pad facing the body sheet metal, so that the foam pad can effectively contact and support the interior of the body sheet metal, preventing the lower part of the door sill assembly from loosening or sinking when pressed. At the same time, the foam pad replaces the traditional metal bracket, effectively reducing the cost of parts and the weight of the vehicle body.

[0010] As a further improvement of the present invention, the door sill assembly is provided with a connecting part, the screw structure is located on the connecting part, and a plastic buckle is installed on the connecting part. The plastic buckle is engaged with the automotive body sheet metal component. The plastic buckle and the screw structure form a combined fixing structure, and both are installed from the front, without the need to disassemble the door or chassis components, thus realizing quick disassembly and assembly of the door sill assembly.

[0011] As a further improvement of the present invention, a plug is embedded in the connecting part opposite the screw structure. The plug can cover the screw structure to prevent the screw from being exposed and affecting the appearance of the vehicle body. In addition, all plugs are designed with the same structure, which effectively avoids the problem of incorrect installation of multiple plugs.

[0012] As a further improvement of the present invention, the screw structure is set at the position where people are likely to step on the threshold when getting on and off the vehicle. This position is the main stress point of the threshold assembly. Setting the screw structure here can effectively improve the fixing strength and prevent the threshold assembly from flipping or falling off due to the force of stepping.

[0013] This is an injection molding process for automotive door sill assemblies, suitable for molding 2m long automotive door sill assemblies. The process includes the following steps: S1, Mold preparation: An injection mold with four sequential valve-controlled gates and three independent temperature-controlled cooling units is used. The four sequential valve-controlled gates are distributed along the length of the door sill assembly, and the three temperature-controlled cooling units are set along the length of the door sill assembly in left, middle, and right sections; S2, Raw material preparation and melting: After drying, the automotive modified polymer composite material is added to the injection molding machine barrel, and melting is completed using a segmented temperature control method; S3, Gradient filling injection: Three-stage pressure-speed gradient injection is performed into the mold cavity through the injection molding machine, in conjunction with the timed opening of the sequential valve-controlled gates. S4. Segmented pressure holding + dynamic shrinkage compensation: After the cavity is filled, a three-stage pressure holding operation is performed in sequence: high pressure compensation, pressure holding and maintenance, and linear pressure release to achieve dynamic shrinkage of the melt; S5. Zoned temperature-controlled cooling: The mold is cooled by zoned temperature control through 3 independent temperature-controlled cooling units to compensate for the heat loss of the melt flow; S6. Demolding and post-processing: After the mold is cooled, it is demolded by a multi-point uniform ejection mechanism, and then post-processed by gate treatment, stress annealing, dimensional and appearance inspection; The overall warpage deformation of the automotive door sill assembly injection molded by the above process is ≤0.25mm / m, the shrinkage depth in the thick wall area is ≤0.02mm, and the internal porosity is ≤1%.

[0014] The parameters for the segmented temperature-controlled melt flow in step S2 are: 205°C for the front section of the barrel, 215°C for the middle section of the barrel, and 225°C for the rear section of the barrel; and 230°C for the nozzle temperature. The parameters for the three-stage pressure-speed gradient injection in step S3 are: 70MPa injection pressure and 25mm / s injection speed for 0-30% cavity filling; 140MPa injection pressure and 65mm / s injection speed for 30%-80% cavity filling; and 95MPa injection pressure and 18mm / s injection speed for 80%-100% cavity filling. The parameters for the three-stage holding pressure operation in step S4 are: 110MPa holding pressure for 0-4s; 85MPa holding pressure for 4-9s; and 45MPa holding pressure for 9-14s.

[0015] The four sequential valve-controlled gates mentioned in step S1 are submarine gates, with a spacing of 500mm between adjacent gates, avoiding the appearance and assembly surfaces of the sill assembly. The gates are controlled by electromagnetic servo valves, with the opening logic being that the two middle gates open first, followed by the two end gates after 0.3s. The two middle gates are closed when the cavity is filled to 85%. The injection mold is equipped with φ9mm conformal cooling channels, with a distance of ≤10mm between the channels and the cavity surface. The dimensions of the three temperature-controlled cooling units are 600mm for the left section, 800mm for the middle section, and 600mm for the right section. The cooling water temperature for the left and right sections is 45-50℃, and for the middle section it is 50-55℃. The cooling temperature difference along the entire length of the mold is ≤3℃. The mold is also equipped with a special molding insert for the 1mm thick weakened area of ​​the easily bent and flipped support lugs at the bottom of the sill assembly. The ejection speed of the multi-point uniform ejection mechanism mentioned in step S6 is 5-8mm / s, and the stress annealing process involves holding at 60-70℃ for 1-2 hours followed by natural cooling.

[0016] Compared with related technologies, the present invention provides the following beneficial effects: This invention adopts a combination of plastic clips and screws for installation, and both are installed and fastened from the front. There is no need to disassemble the door or chassis components, which can quickly realize the installation and replacement of the door sill assembly, facilitate later maintenance, and can be repeatedly disassembled and used. By placing screws at the main stress points of the door sill and designing easily bendable and flip-up brackets at the bottom of the door sill assembly to achieve secondary fixation on the inside, a double-fixation structure is formed, which effectively ensures the firmness of the connection between the door sill assembly and the vehicle body and completely solves the problem of flipping and falling off caused by stepping. The door sheet metal components and sill assembly adopt a V-shaped shielding design, which can hide the sill assembly parting line inside the body, avoiding the appearance defects caused by visible parting line and poor parting line quality, and improving the overall aesthetics of the body. The foam pad inside the door sill assembly serves the dual purpose of absorbing impact energy and increasing bottom rigidity. It can effectively absorb energy during a door collision, improving passive safety. At the same time, the support structure of the foam pad can prevent the lower part of the door sill from loosening when pressed. Furthermore, the foam component replaces the traditional metal bracket, significantly reducing parts costs and lightening the vehicle's weight. The bendable and flip-up support has a weakened area, which can achieve normal demolding and flexible bending during assembly. It solves the technical problem that the bottom of the large door sill assembly cannot be effectively fixed because it exceeds the body sheet metal boundary. The structure is ingeniously designed and adaptable to the use needs of large-size vehicles. The embedded cap at the screw structure conceals the screw's appearance, and the uniform cap structure avoids incorrect assembly, thus improving assembly efficiency.

[0017] This solution addresses issues such as uneven filling, temperature difference during cooling, and warping during the injection molding process for 2mm long threshold parts. Attached Figure Description

[0018] Figure 1 This is one of the main views of the overall structure of the present invention; Figure 2 For the present invention Figure 1 Cross-sectional schematic diagram of BB; Figure 3 This is the second main view of the overall structure of the present invention; Figure 4 For the present invention Figure 3 A cross-sectional schematic diagram of DD; Figure 5 This is a schematic diagram of the door sill assembly structure of the present invention; Figure 6 This is a schematic diagram of the screw structure installation position according to the present invention; Figure 7 For the present invention Figure 6 Enlarged view of region A in the middle; Figure 8 This is a schematic diagram of the easily bendable and flip-up support ear of the present invention during demolding; Figure 9 This is a schematic diagram of the easily bendable flip-up support lug of the present invention after bending; Figure 10 This is a schematic diagram of the plug relative to the car door sheet metal assembly of the present invention; Figure 11 This is a schematic diagram showing the position of the door sill assembly relative to the automotive body sheet metal components according to the present invention; Figure 12 This is a schematic diagram of the plug structure of the present invention.

[0019] The following are the labels in the diagram: 1. Automotive body sheet metal components; 2. Door sill assembly; 3. Door sheet metal components; 4. Screw structure; 5. Flexible flip-up bracket; 6. Screw; 7. Mating part; 8. Foam pad; 9. Connecting part; 10. Plastic clip; 11. End cap. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] Please refer to the following: Figures 1 to 12 This automotive sheet metal, sill, and door sheet metal connection structure is suitable for the body structure of various new energy vehicles, SUVs, and MPVs, achieving a firm connection between the sill assembly and the body sheet metal and door sheet metal. It features convenient installation, beautiful appearance, and high safety. The structure consists of three core parts: automotive body sheet metal component 1, sill assembly 2, and door sheet metal component 3. The components work together to achieve stable connection and performance improvement.

[0022] The door sill assembly 2 is an integrated injection molded part, designed as a long strip structure of about 2m according to the vehicle size. Its injection mold adopts a 4-point sequential valve-controlled gate and a zoned temperature-controlled cooling structure, which solves the problems of uneven filling, cooling temperature difference, and demolding warping of long injection molded parts, ensuring the molding accuracy of door sill assembly 2, with warping deformation ≤0.25mm / m and shrinkage depth in thick-walled areas ≤0.02mm.

[0023] The door sill assembly 2 is provided with a connecting part 9, which integrates a screw structure 4 and a plastic buckle 10. In this embodiment, there are 9 plastic buckles 10, which are evenly distributed along the length of the door sill assembly 2. There are 3 screw structures 4, which are located at the middle position below the front door and the two middle positions below the rear door. These are all force points where people are likely to step on the door sill when getting on and off the vehicle. The plastic buckles 10 are pushed directly into the slots of the car body sheet metal component 1 from the front to achieve pre-fixation. The screw structures 4 are tightened from the front to achieve secondary fixation. The two work together to form a combined fixing structure. The entire installation process does not require disassembling the door or chassis components. The operation is simple and can be completed quickly. It is also convenient for later maintenance.

[0024] The connecting part 9 is embedded with a plug 11 at the position opposite to the screw structure 4. All plugs 11 adopt the same structural design to avoid misinstallation during assembly and improve assembly efficiency. At the same time, the plug 11 can completely cover the screw structure 4 to prevent the screw from being exposed and affecting the appearance of the vehicle body, thus achieving the effect of concealing the unsightly appearance.

[0025] The bottom of the door sill assembly 2 is provided with several bendable and flip-up brackets 5. In this embodiment, there are 5 such brackets. The connection between the bendable and flip-up brackets 5 and the door sill assembly 2 is designed with a weakened area. The material thickness of the weakened area is 1mm, which has good flexibility and can achieve normal demolding. It can also be flexibly bent during assembly. The height difference between the bottom boundary of the door sill assembly 2 and the inner bottom boundary of the car body sheet metal component 1 is 82mm, which makes it impossible to directly arrange a fixing structure. During assembly, the bendable and flip-up brackets 5 are bent towards the inside of the car body so that they fit against the inside of the car body sheet metal component 1. Then, they are fastened with screws 6 to achieve effective fixing of the bottom of the door sill assembly 2. This solves the technical problem that the bottom of the large door sill assembly cannot be fixed to the car body sheet metal.

[0026] The door sill assembly 2 has an integrally formed mating part 7 near the bottom of the door sheet metal component 3. The outline of the mating part 7 matches the bottom edge of the door sheet metal component 3, so that the two fit tightly and improve the sealing performance. At the same time, the connection between the door sheet metal component 3 and the door sill assembly 2 adopts a V-shaped shielding design. The mating part of the door sheet metal component 3 is recessed a certain distance inward to the body. The parting line of the door sill assembly 2 cooperates with this recessed structure to form a V-shaped structure, hiding the parting line of the door sill assembly inside the body. This effectively avoids the appearance defects caused by the visibility of the parting line and poor parting line processing quality, and improves the overall aesthetics of the body.

[0027] Two foam pads 8 are fixed to the inner side of the door sill assembly 2 at the connection between the easily bendable and flip-up bracket 5 and the door sill assembly 2 by metal clips. The foam pads 8 are arranged facing the lower part of the door and are elastic energy-absorbing components. When the front and rear doors collide, the foam pads 8 can effectively absorb the collision energy, preventing the door sill assembly 2 from breaking directly or intruding into the passenger compartment, thus greatly improving the passive safety of the vehicle body. A support boss is added to the side of the foam pads 8 near the car body sheet metal component 1 to increase rigidity. The support boss is in effective contact with the interior of the car body sheet metal component 1 to form a stable support structure, preventing the lower part of the door sill assembly 2 from loosening or denting when pressed. At the same time, the foam pads 8 replace the traditional metal bracket structure, effectively reducing the cost of parts and the weight of the vehicle body while ensuring structural performance.

[0028] The specific assembly process of this invention is as follows: Preliminary preparation: Place the door sill assembly 2 in the vehicle body installation position and confirm that the positions of the plastic clips 10, screw structure 4, and easy-to-bend flip brackets 5 correspond to the matching positions of the car body sheet metal components 1. Front pre-fixing: Push the 9 plastic clips 10 on the door sill assembly 2 one by one into the corresponding slots of the car body sheet metal component 1 from the front to achieve pre-fixing of the door sill assembly 2 to the car body and ensure accurate installation position; Front fastening: Screw the three screw structures 4 into the threaded holes of the car body sheet metal component 1 from the front to complete the fastening of the outside of the door sill assembly 2. The screw positions are all the door sill step force points to ensure the fixation strength. Bottom inner side fixation: Bend the 5 easily bendable flip brackets 5 at the bottom of the door sill assembly 2 towards the inside of the vehicle body so that the brackets fit against the inside of the body sheet metal. Use screws 6 to fasten the flip brackets to the mounting holes on the inside of the body sheet metal to complete the effective fixation of the bottom of the door sill assembly 2. Foam pads: Two foam pads 8 are accurately fixed at designated positions inside the door sill assembly 2 to ensure that the support bosses of the foam pads 8 are in close contact with the interior of the automotive body sheet metal component 1. End cap installation: Insert three identical end caps 11 into the connecting part 9 from the front, opposite the screw structure 4, to cover up the unsightly parts. This completes the entire assembly process.

[0029] During use, when a person steps on the door sill, the screw structure 4 provides effective fixation at the stress point, and together with the inner side fixation of the bottom flip-out bracket, it prevents the door sill assembly 2 from flipping or falling off. When the door is involved in a collision, the foam pad 8 effectively absorbs the collision energy, improving passive safety. When the lower part of the door sill is pressed, the support boss of the foam pad 8 provides rigid support, preventing loosening or denting. At the same time, the V-shaped shielding structure hides the parting line and covers the screws, ensuring the aesthetic appearance of the vehicle body.

[0030] This is an injection molding process for automotive door sill assemblies, suitable for molding 2m long automotive door sill assemblies. The process includes the following steps: S1, Mold preparation: An injection mold with four sequential valve-controlled gates and three independent temperature-controlled cooling units is used. The four sequential valve-controlled gates are distributed along the length of the door sill assembly, and the three temperature-controlled cooling units are set along the length of the door sill assembly in left, middle, and right sections; S2, Raw material preparation and melting: After drying, the automotive modified polymer composite material is added to the injection molding machine barrel, and melting is completed using a segmented temperature control method; S3, Gradient filling injection: Three-stage pressure-speed gradient injection is performed into the mold cavity through the injection molding machine, in conjunction with the timed opening of the sequential valve-controlled gates. S4. Segmented pressure holding + dynamic shrinkage compensation: After the cavity is filled, a three-stage pressure holding operation is performed in sequence: high pressure compensation, pressure holding and maintenance, and linear pressure release to achieve dynamic shrinkage of the melt; S5. Zoned temperature-controlled cooling: The mold is cooled by zoned temperature control through 3 independent temperature-controlled cooling units to compensate for the heat loss of the melt flow; S6. Demolding and post-processing: After the mold is cooled, it is demolded by a multi-point uniform ejection mechanism, and then post-processed by gate treatment, stress annealing, dimensional and appearance inspection; The overall warpage deformation of the automotive door sill assembly injection molded by the above process is ≤0.25mm / m, the shrinkage depth in the thick wall area is ≤0.02mm, and the internal porosity is ≤1%.

[0031] The parameters for the segmented temperature-controlled melt flow in step S2 are: 205°C for the front section of the barrel, 215°C for the middle section of the barrel, and 225°C for the rear section of the barrel; and 230°C for the nozzle temperature. The parameters for the three-stage pressure-speed gradient injection in step S3 are: 70MPa injection pressure and 25mm / s injection speed for 0-30% cavity filling; 140MPa injection pressure and 65mm / s injection speed for 30%-80% cavity filling; and 95MPa injection pressure and 18mm / s injection speed for 80%-100% cavity filling. The parameters for the three-stage holding pressure operation in step S4 are: 110MPa holding pressure for 0-4s; 85MPa holding pressure for 4-9s; and 45MPa holding pressure for 9-14s.

[0032] The four sequential valve-controlled gates mentioned in step S1 are submarine gates, with a spacing of 500mm between adjacent gates, avoiding the appearance and assembly surfaces of the sill assembly. The gates are controlled by electromagnetic servo valves, with the opening logic being that the two middle gates open first, followed by the two end gates after 0.3s. The two middle gates are closed when the cavity is filled to 85%. The injection mold is equipped with φ9mm conformal cooling channels, with a distance of ≤10mm between the channels and the cavity surface. The dimensions of the three temperature-controlled cooling units are 600mm for the left section, 800mm for the middle section, and 600mm for the right section. The cooling water temperature for the left and right sections is 45-50℃, and for the middle section it is 50-55℃. The cooling temperature difference along the entire length of the mold is ≤3℃. The mold is also equipped with a special molding insert for the 1mm thick weakened area of ​​the easily bent and flipped support lugs at the bottom of the sill assembly. The ejection speed of the multi-point uniform ejection mechanism mentioned in step S6 is 5-8mm / s, and the stress annealing process involves holding at 60-70℃ for 1-2 hours followed by natural cooling.

[0033] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A sheet metal connection structure for automobiles, including door sills and door panels, characterized in that: The system includes a car body sheet metal assembly (1), a door sill assembly (2), and a door sheet metal assembly (3). The door sill assembly (2) is installed on the outside of the car body sheet metal assembly (1) by a number of screw structures (4). The door sill assembly (2) is an injection molded part. The bottom of the door sill assembly (2) is provided with a number of bendable and flip-up brackets (5). The bendable and flip-up brackets (5) are fixed to the inside of the car body sheet metal assembly (1) by screws (6). The connection between the door sheet metal assembly (3) and the door sill assembly (2) is set in a V-shaped shielding manner.

2. The automotive sheet metal, sill, and door sheet metal connection structure according to claim 1, characterized in that, The door sill assembly (2) has a mating part (7) at the bottom of the door sheet metal component (3).

3. The automotive sheet metal, sill, and door sheet metal connection structure according to claim 2, characterized in that, The door sill assembly (2) has a foam pad (8) fixed to the inside of the door sill assembly (2) at the connection between the easily bendable flip-up bracket (5) and the door sill assembly (2) by a metal card.

4. The automotive sheet metal, sill, and door sheet metal connection structure according to claim 3, characterized in that, The foam pad (8) increases rigidity near the car body sheet metal component (1).

5. The automotive sheet metal, sill, and door sheet metal connection structure according to claim 1, characterized in that, The door sill assembly (2) is provided with a connecting part (9), the screw structure (4) is located on the connecting part (9), and a plastic buckle (10) is installed on the connecting part (9), and the plastic buckle (10) is engaged with the car body sheet metal component (1).

6. The automotive sheet metal, sill, and door sheet metal connection structure according to claim 1, characterized in that, A plug (11) is embedded in the connecting part (9) opposite the screw structure (4).

7. The automotive sheet metal, sill, and door sheet metal connection structure according to claim 6, characterized in that, The screw structure (4) is located at a position where people are likely to step on the threshold when getting on or off the vehicle.

8. Injection molding process for automotive door sill assembly, characterized in that, This process is applicable to the molding of 2m long automotive door sill assemblies. The process includes the following steps: S1, Mold Preparation: An injection mold with four sequential valve-controlled gates and three independent temperature-controlled cooling units is used. The four sequential valve-controlled gates are distributed along the length of the door sill assembly, and the three temperature-controlled cooling units are arranged in left, middle, and right sections along the length of the door sill assembly; S2, Raw Material Preparation and Melting: After drying, the automotive modified polymer composite material is added to the injection molding machine barrel, and melting is completed using a segmented temperature control method; S3, Gradient Injection: A three-stage pressure-speed gradient injection is performed into the mold cavity using the injection molding machine, coordinated with the timed opening and closing of the sequential valve-controlled gates. Cavity filling; S4, Segmented pressure holding + dynamic shrinkage compensation: After cavity filling, a three-stage pressure holding operation is performed sequentially, consisting of high-pressure shrinkage compensation, pressure holding maintenance, and linear pressure release, to achieve dynamic shrinkage of the melt; S5, Zoned temperature-controlled cooling: The mold is zoned for temperature-controlled cooling through three independent temperature-controlled cooling units to compensate for heat loss from melt flow; S6, Demolding and post-processing: After the mold has cooled, it is demolded through a multi-point uniform ejection mechanism, followed by gate treatment, stress annealing, dimensional and appearance inspection, and post-processing; The overall warpage deformation of the automotive door sill assembly injection molded by the above process is ≤0.25mm / m, the shrinkage depth in the thick-walled area is ≤0.02mm, and the internal porosity is ≤1%.

9. The injection molding process for the automotive door sill assembly according to claim 8, characterized in that, The parameters for the segmented temperature-controlled melt flow in step S2 are: 205°C for the front section of the barrel, 215°C for the middle section of the barrel, and 225°C for the rear section of the barrel; and 230°C for the nozzle temperature. The parameters for the three-stage pressure-speed gradient injection in step S3 are: 70MPa injection pressure and 25mm / s injection speed for 0-30% cavity filling; 140MPa injection pressure and 65mm / s injection speed for 30%-80% cavity filling; and 95MPa injection pressure and 18mm / s injection speed for 80%-100% cavity filling. The parameters for the three-stage holding pressure operation in step S4 are: 110MPa holding pressure for 0-4s; 85MPa holding pressure for 4-9s; and 45MPa holding pressure for 9-14s.

10. The injection molding process for the automotive door sill assembly according to claim 8 or 9, characterized in that, The four sequential valve-controlled gates mentioned in step S1 are submarine gates, with a spacing of 500mm between adjacent gates, avoiding the appearance and assembly surfaces of the sill assembly. The gates are controlled by electromagnetic servo valves, with the opening logic being that the two middle gates open first, followed by the two end gates after 0.3s. The two middle gates are closed when the cavity is filled to 85%. The injection mold is equipped with φ9mm conformal cooling channels, with a distance of ≤10mm between the channels and the cavity surface. The dimensions of the three temperature-controlled cooling units are 600mm for the left section, 800mm for the middle section, and 600mm for the right section. The cooling water temperature for the left and right sections is 45-50℃, and for the middle section it is 50-55℃. The cooling temperature difference along the entire length of the mold is ≤3℃. The mold is also equipped with a special molding insert for the 1mm thick weakened area of ​​the easily bent and flipped support lugs at the bottom of the sill assembly. The ejection speed of the multi-point uniform ejection mechanism mentioned in step S6 is 5-8mm / s, and the stress annealing process involves holding at 60-70℃ for 1-2 hours followed by natural cooling.

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