Rectangular box frame roll-pressing integrated forming process

Abstract

The present application relates to a kind of rectangular box frame roll forming integrated process.Processing technology field belongs to box frame, the process uses SPCC cold-rolled steel coil as raw material, by coil unwinding, plate straightening, multiple progressive roll forming, on-line punching, fixed-length cutting and end beveling processing etc., continuously form the rectangular box frame section with predetermined cross-sectional structure, and can further carry out surface protection treatment and box assembly.The present application replaces traditional aluminum alloy extrusion and sheet metal bending and welding process by continuous roll forming mode, realizes the integrated continuous production of box frame, reduces processing procedure, improves production efficiency and dimensional consistency, while reducing material and manufacturing cost, suitable for large quantities of manufacturing of rectangular frame structure such as LED display screen box.

Description

Technical Field

[0001] This invention belongs to the field of box frame processing technology, specifically relating to a roll forming process for rectangular box frames. Background Technology

[0002] LED display cabinets, serving as the foundation for LED modules and drivers, are widely used in indoor commercial displays, outdoor advertising screens, and stage rental screens. Currently, mainstream LED cabinets are generally made from 6063 aluminum alloy extruded profiles, cut and assembled to form multi-cavity frame profiles, which are then combined with corner brackets and latches to form standard cabinet units. Aluminum alloy extruded profile cabinets offer advantages such as lightweight design, excellent thermal conductivity and heat dissipation, and high dimensional accuracy, long dominating the high-end display market. However, the price of aluminum alloy raw materials continues to fluctuate and rise, and the numerous extrusion molding, CNC milling, and anodizing processes result in high unit production costs, leading to persistently high overall manufacturing costs for mass production of standardized cabinets. Furthermore, the aluminum alloy extrusion process suffers from capacity bottlenecks, with slow extrusion production lines making it difficult to meet the large-scale, low-price supply demands of low-end standardized storefront screens and fixed floor-standing advertising screens.

[0003] Existing Technology 1: LED cabinets assembled from all-aluminum alloy extruded profiles utilize multi-cavity frame profiles formed by high-temperature extrusion of aluminum rods. After being cut to a fixed length, lock holes and wiring grooves are milled, and the cabinets are assembled at the four corners using corner brackets. Existing technology drawbacks: ① Although aluminum has a low density, the unit price of aluminum raw materials is high, and the extrusion, machining, and surface treatment processes are cumbersome, resulting in high material and processing costs for mass production; ② Each profile section requires a separate extrusion mold, leading to high mold opening costs for new specifications and poor economic viability for small-batch orders; ③ The length of a single extruded profile is limited, requiring long frames to be spliced ​​in sections, increasing the number of splicing seams, waterproofing sealing points, and the risk of water leakage; ④ The extrusion equipment has low capacity, resulting in slow extrusion speeds for single profiles and long delivery cycles for orders of tens of thousands of standardized cabinets. Existing Technology 2: Traditional split sheet metal bending LED cabinets use a single SPCC steel plate, bent into four edges, and then welded together by spot welding / full welding to form the cabinet frame. Each cabinet requires four independent bending processes, resulting in significant manual handling during loading and unloading. The shortcomings of this existing technology are: ① Poor consistency in single-piece bending, with large fluctuations in the dimensional tolerance of each edge, leading to poor rectangularity of the four sides of the cabinet after welding, and unevenness and black seams appearing when splicing the entire screen; ② Numerous welding points after segmented bending result in a large number of welds, with prominent issues such as weld pinholes, welding deformation, and stress rebound. Outdoor use makes the welds highly susceptible to rust and water seepage; ③ The lack of a continuous forming process results in extremely low efficiency for manual bending and welding, high labor costs, and an inability to achieve cost reduction through economies of scale; ④ The bent section can only be used to create simple single-layer cavities, making it impossible to integrally form wiring channels and installation positioning steps. Subsequent module assembly requires additional limiting accessories.

[0004] In view of this, this solution was developed. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is to provide a rectangular box frame roll forming process with low production cost and high efficiency.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is: a rectangular box frame roll forming process, comprising the following steps: S1. Coil feeding: SPCC cold-rolled steel coils are selected as raw materials. SPCC cold-rolled steel coils are installed on the unwinding mechanism and the steel strip is fed to the forming production line through continuous unwinding. S2. Plate leveling: The SPCC cold-rolled steel coils are leveled and straightened to eliminate bending deformations that occur during storage and transportation, so that the steel strip remains stable and straight. S3. Continuous roll forming: The leveled SPCC cold-rolled steel coil is passed through multiple sets of progressive roll forming mechanisms. Through multiple cold bending and roll forming processes, the steel strip gradually undergoes plastic deformation to continuously form a long strip-shaped integrated frame profile with the cross-section of the LED display cabinet frame. S4. Online punching; S5. Fixed-length cutting; S6. End processing: Perform a 45° bevel cut on the ends of the cut box frame.

[0007] Furthermore, it also includes step S7, surface protection treatment: the frame of the box after the molding process is carried out in sequence with degreasing and phosphating treatment and anti-corrosion powder coating treatment to improve the corrosion resistance of the frame of the box.

[0008] Furthermore, the anti-corrosion powder coating treatment in step S7 includes the application of at least two layers of anti-corrosion coating.

[0009] Furthermore, it also includes step S8, S8, cabinet assembly: assembling the cabinet frame after surface treatment, and completing the installation of module brackets, sealing strips and accessories to form an LED display cabinet.

[0010] Furthermore, step S4 is specifically operated as follows: during the continuous roll forming process of the frame profile, mounting holes, locking holes or fixing holes are processed simultaneously through an online punching mechanism, so that the frame profile completes the processing of functional holes during the continuous forming process.

[0011] Furthermore, step S5 is specifically operated as follows: according to the size requirements of the LED display cabinet, the continuously output frame profile is cut to a fixed length by a servo cutting mechanism to obtain a cabinet frame of a predetermined length.

[0012] Furthermore, the box frame produced in step S6 includes a frame body and a first connecting edge. The frame body includes a first L-shaped plate, a first horizontal plate, a second L-shaped plate, and a first vertical plate. The upper end of the first L-shaped plate is connected to the first horizontal plate, the first horizontal plate is connected to the upper end of the second L-shaped plate, the upper end of the first vertical plate is connected to the lower end of the second L-shaped plate, and the first vertical plate is erected above the lower end of the first L-shaped plate. The first connecting edge includes a first bent plate and a first extension plate. The first extension plate is connected to the lower end of the first vertical plate and extends inward. One end of the first bent plate is connected to the lower end of the first L-shaped plate and the other end wraps around the end of the first extension plate and fits against the upper surface of the first extension plate.

[0013] Furthermore, the box frame produced in step S6 includes a frame body, which includes a first horizontal plate, a second horizontal plate, a first vertical plate, a third horizontal plate, a fourth horizontal plate, a second vertical plate, a fifth horizontal plate, a third vertical plate, and a sixth horizontal plate. The first and second horizontal plates are arranged vertically and connected at their outward ends. The second horizontal plate is connected to the lower end of the first vertical plate. The upper end of the first vertical plate is connected to the third horizontal plate. The fourth horizontal plate is attached to the upper surface of the third horizontal plate, and their near ends are connected. The other end of the fourth horizontal plate is connected to the upper end of the second vertical plate. The second vertical plate and the first vertical plate are attached to each other. The lower end of the second vertical plate is connected to the upper end of the fifth horizontal plate. The other end of the fifth horizontal plate is connected to the upper end of the third vertical plate. The lower end of the third vertical plate is connected to the sixth horizontal plate. The sixth horizontal plate extends between the first and second horizontal plates, and its upper and lower surfaces are respectively attached to the first and second horizontal plates.

[0014] Furthermore, the box frame produced in step S6 includes a frame body, which includes a first horizontal plate, a second horizontal plate, a first vertical plate, a second vertical plate, a third horizontal plate, a third vertical plate, and a fourth horizontal plate. The first horizontal plate and the second horizontal plate are arranged vertically and connected at their outward ends. The second horizontal plate is connected to the lower end of the first vertical plate. The upper ends of the first vertical plate and the second vertical plate are connected and fitted together. The lower end of the second vertical plate is connected to the third horizontal plate. The other end of the third horizontal plate is connected to the upper end of the third vertical plate. The fourth horizontal plate is connected to the lower end of the third vertical plate. The fourth horizontal plate is located between the first horizontal plate and the second horizontal plate, and the upper and lower surfaces of the fourth horizontal plate are respectively fitted to the first horizontal plate and the second horizontal plate.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. In terms of price, the materials used in this process are inexpensive, and the unit price of SPCC cold-rolled steel raw materials has a significant cost advantage that is far lower than that of aluminum alloys.

[0016] 2. Eliminate high-cost processes such as aluminum alloy extrusion, anodizing, and CNC milling.

[0017] 3. Continuous roller pressing automated production reduces labor input and lowers the overall manufacturing cost of the same size box by 30% to 45%, making it suitable for large-scale mass production of standardized outdoor storefront screens and fixed floor-standing advertising screens. 4. Significantly improved production efficiency: The roll forming production line can continuously and automatically form 24 hours a day, with uninterrupted output of coil material. Compared with single-roll output of aluminum extrusion and single-piece bending of sheet metal, the production efficiency of a single piece is increased by 4 to 6 times, and the delivery cycle of large-volume orders of tens of thousands of units is shortened by 60%, without the capacity limitation of extrusion molds. 5. High forming precision and good splicing effect: The cross-sectional dimensional tolerance of the continuous roll forming of the roll material is ≤0.2mm, and the straightness of the edge is uniform.

[0018] 6. High degree of integration and simplified assembly process: Roll forming of load-bearing steps, wiring grooves, rubber strip grooves and locking grooves in one step, eliminating the need for subsequent milling and additional accessories. LED modules, power supplies and quick locks can be directly assembled, reducing the overall assembly time by 40%.

[0019] 7. Low mold investment: Only one set of rolling mold is needed for the same standard cross section, which can be continuously produced indefinitely. There is no single batch mold loss in aluminum alloy extrusion, no high cost of opening molds for new specifications, and the long-term amortization cost of standardized and universal box is extremely low. Attached Figure Description

[0020] Figure 1 This is a three-dimensional structural diagram of the box in Application Example 1 of the present invention; Figure 2 This is a three-dimensional structural diagram of a single box frame and plastic connector in Application Example 1 of the present invention; Figure 3 This is a schematic diagram of the cross-sectional structure of the box frame in Application Example 1 of the present invention; Figure 4 This is a three-dimensional structural diagram of the box in Application Example 2 of the present invention; Figure 5 This is a three-dimensional structural diagram of a single box frame and plastic connector in Application Example 2 of the present invention; Figure 6 This is a schematic diagram of the cross-sectional structure of the box frame in Application Example 2 of the present invention; Figure 7 This is a three-dimensional structural diagram of the box in Application Example 3 of the present invention; Figure 8This is a three-dimensional structural diagram of a single box frame and plastic connector in Application Example 3 of the present invention; Figure 9 This is a schematic diagram of the cross-sectional structure of the box frame in Application Example 3 of the present invention; Figure 10 This is a front view schematic diagram of the box structure formed by splicing multiple box frames together to form one side in this invention.

[0021] The markings in the diagram are: 1. Box frame; 11. First horizontal plate; 12. Second horizontal plate; 13. First vertical plate; 14. Third horizontal plate; 15. Fourth horizontal plate; 16. Second vertical plate; 17. Fifth horizontal plate; 18. Third vertical plate; 19. Sixth horizontal plate; 21. First L-shaped plate; 22. Second L-shaped plate; 23. First bent plate; 24. First extension plate; 26. Edge; 27. Arc-shaped protrusion; 2. Plastic connector; 3. Plastic part. Detailed Implementation

[0022] To make the above features and advantages of the present invention more apparent and understandable, specific embodiments are described below in conjunction with the accompanying drawings for detailed explanation.

[0023] This embodiment provides a roll forming process for a rectangular box frame 1, characterized by the following steps: S1. Coil feeding: SPCC cold-rolled steel coils are selected as raw materials. SPCC cold-rolled steel coils are installed on the unwinding mechanism and the steel strip is fed to the forming production line through continuous unwinding. S2. Plate leveling: The SPCC cold-rolled steel coils are leveled and straightened to eliminate bending deformations that occur during storage and transportation, so that the steel strip remains stable and straight. S3. Continuous roll forming: The leveled SPCC cold-rolled steel coil is passed through multiple sets of progressive roll forming mechanisms. Through multiple cold bending and roll forming processes, the steel strip gradually undergoes plastic deformation to continuously form a long strip-shaped integrated frame profile with the cross-section of the LED display cabinet frame. S4. Online punching: During the continuous roll forming process of the frame profile, the mounting holes, lock holes or fixing holes are processed simultaneously through the online punching mechanism, so that the functional hole processing is completed in the continuous forming process of the frame profile.

[0024] S5. Fixed-length cutting: According to the size requirements of the LED display cabinet, the continuously output frame profile is cut to a fixed length by a servo cutting mechanism to obtain the cabinet frame of a predetermined length.

[0025] S6. End processing: Perform a 45° bevel cut on the ends of the cut box frame; S7. Surface protection treatment: The frame of the box after the molding process is degreased and phosphated and then coated with anti-corrosion powder to improve the corrosion resistance of the frame. S8, S8, Cabinet Assembly: Assemble the surface-treated cabinet frame, and complete the installation of module brackets, sealing strips and accessories to form the LED display cabinet.

[0026] The following box frame 1 can be manufactured using this process: Application Example 1 Normally used square tubular box: such as Figures 1-3 As shown, the box body includes four box body frames 1 and four plastic connectors 2. The four box body frames 1 are arranged in a rectangular shape and connected end to end. The plastic connectors 2 are set between two adjacent box body frames 1.

[0027] The box frame 1 is formed by bending continuous steel plates. The box frame 1 includes a frame body and a first connecting edge. The frame body includes a first L-shaped plate 21, a first horizontal plate 11, a second L-shaped plate 22 and a first vertical plate 13. The upper end of the first L-shaped plate 21 is connected to the first horizontal plate 11. The first horizontal plate 11 is connected to the upper end of the second L-shaped plate 22. The upper end of the first vertical plate 13 is connected to the lower end of the second L-shaped plate 22. The first vertical plate 13 is erected above the lower end of the first L-shaped plate 21. The first connecting edge includes a first bent plate 23 and a first extension plate 24. The first extension plate 24 is connected to the lower end of the first vertical plate 13 and extends inward. One end of the first bent plate 23 is connected to the lower end of the first L-shaped plate 21 and the other end wraps around the end of the first extension plate 24 and fits against the upper surface of the first extension plate 24.

[0028] In this embodiment, a first connecting hole is provided on the first connecting edge, and the first connecting hole passes through the first bent plate 23 and the first L-shaped plate 21. The first connecting hole is used for fixing to the wall.

[0029] In this embodiment, a flange 26 is stamped on the first vertical plate 13. The flange 26 is parallel to the first extension plate 24. A second connecting hole is formed on the flange 26. The presence of the flange 26 allows a dovetail plate to be installed between the two opposing box frames 1. The opening of the dovetail plate faces inward, and both sides of the dovetail plate are used to connect the display screen. The second connecting hole on the flange 26 is used to connect the dovetail plate.

[0030] In this application example, a third connecting hole is provided on the transverse region of the second L-shaped plate 22. The third connecting hole is used to fix the plastic connector 2.

[0031] In this application example, the box frame 1 has beveled notches at both ends. The beveled notches are for splicing the four box frames 1 into a rectangle.

[0032] In this application example, an inwardly curved protrusion 27 is formed between one end of the first bent plate 23 and the first L-shaped plate 21, so that the space formed by the frame body is isolated from the outside.

[0033] The plastic connector 2 includes a corner piece, which is rectangular in shape. The corner piece is used to fill the gap between adjacent box frames 1. The corner piece has an insert frame on two adjacent sides, which extends into the hole formed by the frame body for fixation.

[0034] like Figure 10 As shown, preferably, the box frames 1 on the same side can be spliced ​​together, and adjacent box frames 1 on the same side are connected by embedded plastic parts 3, which can seal the gap between adjacent frames 1.

[0035] Application Example 2 like Figures 4-6 As shown, the embedded box includes four box frames 1 and four plastic connectors 2. The four box frames 1 are arranged in a rectangular shape and connected end to end. The plastic connectors 2 are set between two adjacent box frames 1. The box frame 1 is formed by bending continuous steel plates. The box frame 1 includes a frame body, which includes a first horizontal plate 11, a second horizontal plate 12, a first vertical plate 13, a third horizontal plate 14, a fourth horizontal plate 15, a second vertical plate 16, a fifth horizontal plate 17, a third vertical plate 18, and a sixth horizontal plate 19. The first horizontal plate 11 and the second horizontal plate 12 are arranged vertically and connected at their outward ends. The second horizontal plate 12 is connected to the lower end of the first vertical plate 13, and the upper end of the first vertical plate 13 is connected to the third horizontal plate 14. The fourth horizontal plate 15 is fitted onto the third horizontal plate. The upper surfaces of the two are connected at their closest ends. The other end of the fourth horizontal plate 15 is connected to the upper end of the second vertical plate 16. The second vertical plate 16 and the first vertical plate 13 are in contact. The lower end of the second vertical plate 16 is connected to the upper end of the fifth horizontal plate 17. The other end of the fifth horizontal plate 17 is connected to the upper end of the third vertical plate 18. The lower end of the third vertical plate 18 is connected to the sixth horizontal plate 19. The sixth horizontal plate 19 extends between the first horizontal plate 11 and the second horizontal plate 12, and the upper and lower surfaces of the sixth horizontal plate 19 are in contact with the first horizontal plate 11 and the second horizontal plate 12, respectively.

[0036] The first horizontal plate 11, the second horizontal plate 12, and the sixth horizontal plate 19 are provided with a first connecting hole. The first connecting hole is used for fixing to the wall.

[0037] The third vertical plate 18 has a stamped edge 26, which is parallel to the first horizontal plate 11. A second connecting hole is formed on the edge 26. The edge 26 allows for the installation of a dovetail plate between two opposing housing frames 1. The dovetail plate has an inward-facing opening, and both sides are used to connect to the display screen. The second connecting hole on the edge 26 is used to connect the dovetail plate.

[0038] The fifth horizontal plate 17 has a third connecting hole, which is used to fix the plastic connector 2.

[0039] The plastic connector 2 includes a corner piece, which is used to fill the gap between adjacent box frames 1. The corner piece has an insert frame on two adjacent sides, which extends into the hole formed by the frame body for fixation. The upper end of the corner piece has an arc plate, which is used to be flush with the fourth horizontal plate 15 of the two adjacent frame bodies and fill the gap formed between them.

[0040] In this application example, the second horizontal plate 12 has an inwardly curved protrusion 27 at a position corresponding to the second vertical plate 16, so that the space formed by the second horizontal plate 12, the first vertical plate 13, the third horizontal plate 14, the fourth horizontal plate 15 and the second vertical plate 16 is isolated from the outside.

[0041] like Figure 10 As shown, preferably, the box frames 1 on the same side can be spliced ​​together, and adjacent box frames 1 on the same side are connected by embedded plastic parts 3, which can seal the gap between adjacent frames 1.

[0042] Application Example 3 like Figures 7-9 As shown, the external enclosure includes four enclosure frames 1 and four plastic connectors 2. The four enclosure frames 1 are arranged in a rectangular pattern and connected end to end. The plastic connectors 2 are set between two adjacent enclosure frames 1.

[0043] The box frame 1 is formed by bending continuous steel plates. The box frame 1 includes a frame body, which includes a first horizontal plate 11, a second horizontal plate 12, a first vertical plate 13, a second vertical plate 16, a third horizontal plate 14, a third vertical plate 18, and a fourth horizontal plate 15. The first horizontal plate 11 and the second horizontal plate 12 are arranged vertically and connected at their outward ends. The second horizontal plate 12 is connected to the lower end of the first vertical plate 13. The upper end of the first vertical plate 13 is connected to the upper end of the second vertical plate 16. The first vertical plate 13 and the second vertical plate 16 are in contact with each other. The lower end of the second vertical plate 16 is connected to the third horizontal plate 14. The other end of the third horizontal plate 14 is connected to the upper end of the third vertical plate 18. The fourth horizontal plate 15 is connected to the lower end of the third vertical plate 18. The fourth horizontal plate 15 is located between the first horizontal plate 11 and the second horizontal plate 12, and the upper and lower surfaces of the fourth horizontal plate 15 are in contact with the first horizontal plate 11 and the second horizontal plate 12, respectively.

[0044] The first horizontal plate 11, the second horizontal plate 12, and the fourth horizontal plate 15 are provided with a first connecting hole. The first connecting hole is used for fixing to the wall.

[0045] The third vertical plate 18 has a stamped edge 26, which is parallel to the first horizontal plate 11. A second connecting hole is formed on the edge 26. The edge 26 allows for the installation of a dovetail plate between two opposing housing frames 1. The dovetail plate has an inward-facing opening, and both sides are used to connect to the display screen. The second connecting hole on the edge 26 is used to connect the dovetail plate.

[0046] The third horizontal plate 14 has a third connecting hole, which is used to fix the plastic connector 2.

[0047] The plastic connector 2 includes corner pieces, which are used to fill the gap between adjacent box frames 1. The corner pieces have extension frames on two adjacent sides, which extend into the holes formed by the frame body for fixation.

[0048] In this application example, the second horizontal plate 12 has an inwardly curved protrusion 27 at a position corresponding to the third vertical plate 18, so that the space formed by the second horizontal plate 12, the first vertical plate 13, the second vertical plate 16, the third horizontal plate 14 and the third vertical plate 18 is isolated from the outside.

[0049] like Figure 10 As shown, preferably, the box frames 1 on the same side can be spliced ​​together, and adjacent box frames 1 on the same side are connected by embedded plastic parts 3, which can seal the gap between adjacent frames 1.

[0050] The foregoing has shown and described the basic principles and main features of the present invention, as well as its advantages. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope. All such changes and modifications fall within the scope of the present invention as claimed, which is defined by the appended claims and their equivalents.

Claims

1. A roll forming process for a rectangular box frame, characterized in that: Includes the following steps: S1. Coil feeding: SPCC cold-rolled steel coils are selected as raw materials. SPCC cold-rolled steel coils are installed on the unwinding mechanism and the steel strip is fed to the forming production line through continuous unwinding. S2. Plate leveling: The SPCC cold-rolled steel coils are leveled and straightened to eliminate bending deformations that occur during storage and transportation, so that the steel strip remains stable and straight. S3. Continuous roll forming: The leveled SPCC cold-rolled steel coil is passed through multiple sets of progressive roll forming mechanisms. Through multiple cold bending and roll forming processes, the steel strip gradually undergoes plastic deformation to continuously form a long strip-shaped integrated frame profile with the cross-section of the LED display cabinet frame. S4. In-line punching; S5. Fixed-length cutting; S6. End processing: Perform a 45° bevel cut on the ends of the cut box frame.

2. The roll forming process for a rectangular box frame according to claim 1, characterized in that: It also includes step S7, surface protection treatment: the box frame after the molding process is carried out in sequence with degreasing and phosphating treatment and anti-corrosion powder coating treatment to improve the corrosion resistance of the box frame.

3. The roll forming process for a rectangular box frame according to claim 2, characterized in that: The anti-corrosion powder coating treatment in step S7 includes spraying at least two layers of anti-corrosion coating.

4. The roll forming process for a rectangular box frame according to claim 2, characterized in that: It also includes step S8, S8, cabinet assembly: assembling the cabinet frame after surface treatment, and completing the installation of module brackets, sealing strips and accessories to form the LED display cabinet.

5. The roll forming process for a rectangular box frame according to claim 1, characterized in that: The specific operation of step S4 is as follows: During the continuous roll forming process of the frame profile, the mounting holes, locking holes or fixing holes are processed simultaneously by the online punching mechanism, so that the functional hole processing is completed in the continuous forming process of the frame profile.

6. The roll forming process for a rectangular box frame according to claim 1, characterized in that: The specific operation of step S5 is as follows: According to the size requirements of the LED display cabinet, the continuously output frame profile is cut to a fixed length by a servo cutting mechanism to obtain the cabinet frame of a predetermined length.

7. The roll forming process for a rectangular box frame according to claim 1, characterized in that: The box frame produced in step S6 includes a frame body and a first connecting edge. The frame body includes a first L-shaped plate, a first horizontal plate, a second L-shaped plate and a first vertical plate. The upper end of the first L-shaped plate is connected to the first horizontal plate, the first horizontal plate is connected to the upper end of the second L-shaped plate, the upper end of the first vertical plate is connected to the lower end of the second L-shaped plate, and the first vertical plate is erected above the lower end of the first L-shaped plate. The first connecting edge includes a first bent plate and a first extension plate. The first extension plate is connected to the lower end of the first vertical plate and extends inward. One end of the first bent plate is connected to the lower end of the first L-shaped plate and the other end wraps around the end of the first extension plate and fits against the upper surface of the first extension plate.

8. The roll forming process for a rectangular box frame according to claim 1, characterized in that: The box frame produced in step S6 includes a frame body, which includes a first horizontal plate, a second horizontal plate, a first vertical plate, a third horizontal plate, a fourth horizontal plate, a second vertical plate, a fifth horizontal plate, a third vertical plate, and a sixth horizontal plate. The first and second horizontal plates are arranged vertically and connected at their outward ends. The second horizontal plate is connected to the lower end of the first vertical plate. The upper end of the first vertical plate is connected to the third horizontal plate. The fourth horizontal plate is attached to the upper surface of the third horizontal plate, and the two are connected at their closest ends. The other end of the fourth horizontal plate is connected to the upper end of the second vertical plate. The second vertical plate and the first vertical plate are attached to each other. The lower end of the second vertical plate is connected to the upper end of the fifth horizontal plate. The other end of the fifth horizontal plate is connected to the upper end of the third vertical plate. The lower end of the third vertical plate is connected to the sixth horizontal plate. The sixth horizontal plate extends between the first and second horizontal plates, and the upper and lower surfaces of the sixth horizontal plate are respectively attached to the first and second horizontal plates.

9. The roll forming process for a rectangular box frame according to claim 1, characterized in that: The box frame produced in step S6 includes a frame body, which includes a first horizontal plate, a second horizontal plate, a first vertical plate, a second vertical plate, a third horizontal plate, a third vertical plate, and a fourth horizontal plate. The first horizontal plate and the second horizontal plate are arranged vertically and connected at their outward ends. The second horizontal plate is connected to the lower end of the first vertical plate. The upper ends of the first vertical plate and the second vertical plate are connected and attached to each other. The lower end of the second vertical plate is connected to the third horizontal plate. The other end of the third horizontal plate is connected to the upper end of the third vertical plate. The fourth horizontal plate is connected to the lower end of the third vertical plate. The fourth horizontal plate is located between the first horizontal plate and the second horizontal plate, and its upper and lower surfaces are attached to the first horizontal plate and the second horizontal plate, respectively.

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