Design method of shape control supporting structure and shape control supporting structure

Abstract

The invention discloses a shape control supporting structure design method and a shape control supporting structure.The method is suitable for 3D printing of large-size frame parts and comprises the steps that a main supporting plate is arranged in a to-be-supported area of the large-size frame parts, and the height direction of the main supporting plate is the 3D printing forming direction; determining whether to add an auxiliary support structure according to the size of the main support plate; if it is determined that the auxiliary supporting structure is additionally arranged, a plurality of auxiliary supporting frames are arranged on the side face, facing the large-size frame part, of the main supporting plate at intervals in the length direction, so that the auxiliary supporting frames and the main supporting plate are combined to form a supporting unit with the trapezoidal cross section, and auxiliary supporting plates are arranged in the supporting unit; the plurality of auxiliary supporting frames and the plurality of auxiliary supporting plates form an auxiliary supporting structure; a cylindrical reinforcing structure is arranged on one or two of the supporting units located in the middle, and the reinforcing structure, the main supporting plate and the auxiliary supporting structure form a shape control supporting structure. The deformation condition is effectively improved and the cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of 3D printing technology, specifically to a shape-controlled support structure design method and a shape-controlled support structure. Background Technology

[0002] 3D printing technology belongs to additive manufacturing technology, which uses a layer-by-layer manufacturing concept to achieve rapid production of parts. Among the additive manufacturing technologies for metal parts, the most widely used is selective laser melting (SLM). This technology involves pre-laying a layer of metal powder of a certain thickness on the horizontal surface of a metal substrate, then using a laser source to melt and sinter the powder in a selected area, forming a two-dimensional cross-sectional structure. This process is repeated to ultimately create a three-dimensional structure composed of many stacked two-dimensional cross-sectional structures. Using 3D printing technology, it is possible to manufacture metal parts with complex structures, large sizes, and superior performance characteristics quickly and economically.

[0003] There is a strong demand for 3D printing technology to replace traditional casting for large-sized frame-like structural parts due to the long production cycle and high mold costs associated with traditional casting. During the 3D printing process of large-sized frame-like parts, support structures are needed to assist in forming and control structural deformation. However, an inappropriate support structure design can lead to manufacturing defects and increased costs. Serious manufacturing defects include 3D printing failures and significant dimensional deviations in the printed results. Cost impacts include increased time costs and material waste. Summary of the Invention

[0004] The main objective of this invention is to propose a shape-controlled support structure design method and a shape-controlled support structure, aiming to solve the above-mentioned problems.

[0005] To achieve the above objectives, this invention proposes a shape-controlled support structure design method, applicable to 3D printing large-size frame-like parts. The shape-controlled support structure design method includes: Step S100: Set a main support plate in the area to be supported of the large-size frame-like component, wherein the height direction of the main support plate is the 3D printing forming direction of the large-size frame-like component. Step S200: Determine whether to add an auxiliary support structure based on the dimensions of the main support plate; Step S300: If it is determined that the auxiliary support structure is to be added, then multiple auxiliary support frames are spaced apart along the length of the main support plate on the side of the main support plate facing the large frame-like component, so that each auxiliary support frame and the main support plate are combined to form a support unit with a trapezoidal cross-section, and an auxiliary support plate is set in each support unit, so that the support unit is divided into two small support frames distributed sequentially along the length of the main support plate, and the multiple auxiliary support frames and the multiple auxiliary support plates together constitute the auxiliary support structure; Step S400: On one or two of the middle support units among the plurality of support units, a cylindrical reinforcing structure is provided with the side rib of the auxiliary support frame in the support unit away from the main support plate as the axis. The reinforcing structure, the main support plate, and the auxiliary support structure together constitute a shape-controlling support structure.

[0006] Furthermore, step S100 specifically includes: Step S110: Analyze the model of the large-size frame-like parts to determine the 3D printing forming direction of the large-size frame-like parts; Step S120: Set a main support plate in the area to be supported of the large frame-like component, and the height direction of the main support plate is the 3D printing forming direction.

[0007] Furthermore, step S200 specifically includes: Step S210: Determine the dimensions of the main support plate; Step S220: If the length of the main support plate is greater than or equal to 300mm and the height of the main support plate is greater than or equal to 650mm and less than or equal to 1200mm, then it is determined that the auxiliary support frame will be added.

[0008] Furthermore, step S400 specifically includes: Step S410: Determine the number of auxiliary support frames; Step S420: If the number of auxiliary support frames is odd, then on the middle support unit among the multiple support units, a cylindrical reinforcing structure is set with the two side edges of the auxiliary support frame in the support unit that are far from the main support plate as axes. If the number of auxiliary support frames is even, then on the two middle support units among the multiple support units, a cylindrical reinforcing structure is set with the two side edges of the two auxiliary support frames in the two support units that are far from the main support plate and adjacent to each other as axes.

[0009] Furthermore, the diameter of the reinforcing structure is greater than or equal to 14 mm and less than or equal to 16 mm, and the height of the reinforcing structure is the same as the height of the supporting unit.

[0010] Furthermore, there are n support units, and the distance between any two adjacent support units among the n support units is set to l; The upper base of the cross-section of each support unit is denoted as 'a', and the two interior angles are denoted as 'α' and 'β'. The length of the line connecting the midpoint of the upper base of the cross-section to the midpoint of the lower base of the cross-section is denoted as 'h', and 25mm≤h≤35mm, α=β, 45°≤α≤55°. , 20mm≤l≤30mm, and Where K and b are both constants. , .

[0011] Furthermore, the thickness of the auxiliary support frame and the thickness of the auxiliary support plate are greater than or equal to 2mm and less than or equal to 3mm, respectively.

[0012] The present invention also provides a shape-controlled support structure, which is designed using a shape-controlled support structure design method. The shape-controlled support structure includes a main support plate, which is used to be placed in the area to be supported of a large-size frame-like component, and the height direction of the main support plate is the 3D printing forming direction of the large-size frame-like component.

[0013] Furthermore, the length of the main support plate is greater than or equal to 300mm, and the height of the main support plate is greater than or equal to 650mm and less than or equal to 1200mm. The shape-controlling support structure also includes: An auxiliary support structure is provided on one side of the main support plate facing the large-sized frame-like component. It includes multiple auxiliary support frames and multiple auxiliary support plates. The auxiliary support frames are spaced apart along the length of the main support plate, and each auxiliary support frame and the main support plate combine to form a support unit with a trapezoidal cross-section. Each support unit is provided with an auxiliary support plate, such that the support unit is divided into two smaller support frames sequentially distributed along the length of the main support plate. Two reinforcing structures are inserted into the auxiliary support frame of one or two of the multiple support units located in the middle. The two reinforcing structures are symmetrically arranged, each reinforcing structure is cylindrical, and the axis of each reinforcing structure coincides with the side ridge of its corresponding auxiliary support frame that is away from the main support plate.

[0014] Furthermore, the number of auxiliary support frames is even, with two reinforcing structures inserted one-to-one into the auxiliary support frames of the two middle support units among the plurality of support units, and the axes of the two reinforcing structures coinciding one-to-one with the two adjacent side ribs within the two auxiliary support frames that are far from the main support plate; or, The number of auxiliary support frames is odd. Two reinforcing structures are inserted into the auxiliary support frame of the middle support unit among the multiple support units, and the axes of the two reinforcing structures correspond one-to-one with the two side ribs of the auxiliary support frame that are away from the main support plate.

[0015] In the technical solution of the present invention, a reasonable shape control support structure can be obtained through the shape control support structure design method, which ensures the stability of the 3D printing process of large-size frame-like parts. At the same time, it can effectively improve the deformation of large-size frame-like parts, and the design of the shape control support structure is simplified, which can avoid excessive waste of raw materials caused by redundant design, reduce costs, and help improve forming efficiency. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0017] Figure 1 A flowchart of the shape-controlled support structure design method provided by the present invention; Figure 2 for Figure 1 Flowchart of step S400; Figure 3 This is a schematic diagram of an embodiment of the shape-controlling support structure provided by the present invention; Figure 4 for Figure 3 Exploded view of the central control support structure; Figure 5 for Figure 3 A top view of part of the central control support structure; Figure 6 This is a structural schematic diagram of a large-size frame-like component; Figure 7 A schematic diagram of a form control support structure for large frame-type components; Figure 8 for Figure 7 A sectional view; Figure 9This is a finite element simulation diagram of the form control effect of an existing form control support structure. Figure 10 A finite element simulation diagram of the shape control effect of the shape control support structure designed by the shape control support structure design method provided by the present invention.

[0018] Explanation of icon numbers:

[0019] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0022] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0023] There is a strong demand for 3D printing technology to replace traditional casting for large-sized frame-like structural parts due to the long production cycle and high mold costs associated with traditional casting. During the 3D printing process of large-sized frame-like parts, support structures are needed to assist in forming and control structural deformation. However, an inappropriate support structure design can lead to manufacturing defects and increased costs. Serious manufacturing defects include 3D printing failures and significant dimensional deviations in the printed results. Cost impacts include increased time costs and material waste.

[0024] Therefore, this invention provides a shape-controlled support structure design method, applicable to 3D printing large-size frame-like parts. Figure 1 A flowchart of the shape-controlled support structure design method provided by the present invention.

[0025] Please see Figure 1 The shape-controlled support structure design method includes the following steps: Step S100: Set a main support plate 1 in the support area 210 of the large frame component 200, wherein the height direction of the main support plate 1 is the 3D printing forming direction of the large frame component 200.

[0026] Furthermore, step S100 specifically includes: Step S110: Analyze the model of the large-size frame component 200 to determine the 3D printing forming direction of the large-size frame component 200.

[0027] Step S120: A main support plate 1 is set in the support area 210 of the large frame-type component 200, and the height direction of the main support plate 1 is the 3D printing forming direction.

[0028] Step S200: Determine whether to add an auxiliary support structure based on the dimensions of the main support plate 1.

[0029] Thus, the dimensions of frame components can be analyzed by the dimensions of the main support plate 1. When the dimensions of the main support plate 1 are large, the dimensions of the frame components are also large. The auxiliary support structure can be added to further support the frame components and help the main support plate 1 improve the shape control effect.

[0030] Furthermore, step S200 specifically includes: Step S210: Determine the dimensions of the main support plate 1.

[0031] Specifically, the dimensions of the main support plate 1 include its length L, height H, and thickness W. More specifically, the thickness W of the main support plate 1 is greater than or equal to 2.5 mm and less than or equal to 4 mm.

[0032] Step S220: If the length of the main support plate 1 is greater than or equal to 300mm and the height of the main support plate 1 is greater than or equal to 650mm and less than or equal to 1200mm, then it is determined that the auxiliary support frame 2 will be added.

[0033] Step S300: If it is determined that the auxiliary support structure is to be added, then multiple auxiliary support frames 2 are arranged at intervals along the length direction of the main support plate 1 on the side of the main support plate 1 facing the large-size frame component 200, so that each auxiliary support frame 2 and the main support plate 1 are combined to form a support unit with a trapezoidal cross-section, and an auxiliary support plate 3 is arranged in each support unit, so that the support unit is divided into two small support frames distributed sequentially along the length direction of the main support plate 1, and the multiple auxiliary support frames 2 and the multiple auxiliary support plates 3 together constitute the auxiliary support structure.

[0034] It should be noted that in this invention, the bottom end of the main support plate 1 may abut against the 3D printed substrate or there may be a gap. However, the bottom end of the auxiliary support structure abuts against the 3D printed substrate. Thus, the height of the auxiliary support structure is greater than or equal to the height H of the main support plate 1.

[0035] More specifically, in one embodiment of the present invention, the cross-sectional shape of the support unit is an isosceles trapezoid and is symmetrically arranged along the auxiliary support plate 3, that is, the two support frames are symmetrically arranged.

[0036] Step S400: On one or two of the middle support units among the plurality of support units, a cylindrical reinforcing structure 4 is provided with the side edge of the auxiliary support frame 2 in the support unit away from the main support plate 1 as the axis. The reinforcing structure 4, together with the main support plate 1 and the auxiliary support structure, constitute a shape-controlling support structure.

[0037] In this step, by adding the reinforcing structure 4, the support stability of the auxiliary support structure is improved, thereby further improving the shape control support effect of the large-size frame component 200.

[0038] For further details, please refer to Figure 2 Step S400 specifically includes: Step S410: Determine the number of auxiliary support frames 2.

[0039] Step S420: If the number of auxiliary support frames 2 is odd, then on the middle support unit among the multiple support units, a cylindrical reinforcing structure 4 is set on the two side edges of the auxiliary support frame 2 in the support unit that are far away from the main support plate 1, respectively, as the axis. If the number of auxiliary support frames 2 is even, then on the two middle support units among the multiple support units, a cylindrical reinforcing structure 4 is set on the two side edges of the two auxiliary support frames 2 in the two support units that are far away from the main support plate 1 and adjacent to each other, respectively, as the axis.

[0040] In this step, the positions of the two reinforcing structures 4 are determined according to the number of auxiliary support frames 2, so that the auxiliary support structure is subjected to uniform force, thereby improving the support stability of the auxiliary support structure.

[0041] It should be noted that the reinforcing structure 4 is inserted into the auxiliary support frame 2.

[0042] Specifically, the diameter of the reinforcing structure 4 is greater than or equal to 14 mm and less than or equal to 16 mm, and the height of the reinforcing structure 4 is the same as the height of the supporting unit.

[0043] For details, please refer to Figure 5 The support unit comprises n units, and the distance between any two adjacent support units is set to l; the upper base of the cross-section of each support unit is set to 'a', the two interior angles are set to 'α' and 'β', and the length of the line connecting the midpoint of the upper base of the cross-section to the midpoint of the lower base of the cross-section is set to 'h', where 25mm≤h≤35mm, α=β, and 45°≤α≤55°. , 20mm≤l≤30mm, and Where K and b are both constants. , Thus, the structure of the designed support unit can efficiently support the large-size frame-like components 200, achieving good shape control while avoiding redundant design.

[0044] It should be noted that the length h of the line connecting the midpoint of the upper base of the cross-section to the midpoint of the lower base of the cross-section is the height of the trapezoidal cross-section. Furthermore, in the embodiment described above where "the cross-section of the support unit is an isosceles trapezoid and symmetrically arranged along the auxiliary support plate 3," the length of the auxiliary support plate 3 is the length h of the line connecting the midpoint of the upper base of the cross-section to the midpoint of the lower base of the cross-section.

[0045] Specifically, the thickness of the auxiliary support frame 2 and the thickness of the auxiliary support plate 3 are greater than or equal to 2mm and less than or equal to 3mm, respectively.

[0046] In the technical solution of this invention, the shape control support structure design method can obtain a reasonable shape control support structure, ensuring the stability of the 3D printing process of large-size frame-type parts 200. At the same time, it can effectively improve the deformation of large-size frame-type parts 200, and the design of the shape control support structure is simplified, avoiding excessive waste of raw materials caused by redundant design, reducing costs, and improving forming efficiency.

[0047] Furthermore, for the large-size frame-like component 200 that is supported by the shape-controlled support structure designed using the shape-controlled support structure design method provided by this invention, the deformation during its forming process is analyzed and calculated using finite element simulation (e.g., Figure 8 and Figure 9 As shown in the figure, it was found that the deformation of local areas of large frame-type parts 200 was significantly improved, with the maximum deformation reduced by 56%, which can meet the needs of printing and manufacturing the part blank structure.

[0048] This invention also provides a shape-controlled support structure 100, designed using the shape-controlled support structure design method described above. Please refer to [link to relevant documentation]. Figure 3 , Figure 4 ,as well as Figures 5-7 The shape control support structure 100 includes a main support plate 1, which is used to be placed in the support area 210 of the large-size frame-like component 200, and the height direction of the main support plate 1 is the 3D printing forming direction of the large-size frame-like component 200.

[0049] For further details, please refer to Figures 3-5 ,as well as Figure 8The main support plate 1 has a length greater than or equal to 300 mm and a height greater than or equal to 650 mm and less than or equal to 1200 mm. The shape control support structure 100 also includes an auxiliary support structure and two reinforcing structures 4. The auxiliary support structure is located on the side of the main support plate 1 facing the large-size frame component 200, and includes multiple auxiliary support frames 2 and multiple auxiliary support plates 3. The multiple auxiliary support frames 2 are spaced apart along the length direction of the main support plate 1, and each auxiliary support frame 2 and the main support plate 1 are combined to form a support unit with a trapezoidal cross-section. Each support unit is provided with the auxiliary support plate 3, so that the support unit is divided into two small support frames distributed sequentially along the length direction of the main support plate 1. The two reinforcing structures 4 are inserted into the auxiliary support frame 2 of one or two of the multiple support units located in the middle. The two reinforcing structures 4 are symmetrically arranged, each reinforcing structure 4 is cylindrical, and the axis of each reinforcing structure 4 coincides with the side edge of its corresponding auxiliary support frame 2 away from the main support plate 1.

[0050] Furthermore, the placement positions of the two reinforcing structures 4 are determined based on the number of auxiliary support frames 2.

[0051] For more details, please see Figure 8 In one embodiment of the present invention, the number of auxiliary support frames 2 is even, and the two reinforcing structures 4 are inserted one-to-one on the auxiliary support frames 2 of the two middle support units among the plurality of support units, and the axes of the two reinforcing structures 4 coincide one-to-one with the two side ribs of the two auxiliary support frames 2 that are far away from the main support plate 1 and are adjacent to each other.

[0052] The number of auxiliary support frames 2 is odd. Two reinforcing structures 4 are inserted into the auxiliary support frame 2 of the middle support unit among the multiple support units, and the axes of the two reinforcing structures 4 correspond one-to-one with the two side ribs of the auxiliary support frame 2 that are away from the main support plate 1.

[0053] The improved shape control support structure 100 of this invention is suitable for shape control support of large-size frame-type parts 200. It has good shape control support effect, simple structure and low production cost.

[0054] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for designing a shape-controlled support structure, applicable to 3D printing large-size frame-like parts, characterized in that, The shape-controlled support structure design method includes the following steps: Step S100: Set a main support plate in the area to be supported of the large-size frame-like component, wherein the height direction of the main support plate is the 3D printing forming direction of the large-size frame-like component. Step S200: Determine whether to add an auxiliary support structure based on the dimensions of the main support plate; Step S300: If it is determined that the auxiliary support structure is to be added, then multiple auxiliary support frames are spaced apart along the length of the main support plate on the side of the main support plate facing the large frame-like component, so that each auxiliary support frame and the main support plate are combined to form a support unit with a trapezoidal cross-section, and an auxiliary support plate is set in each support unit, so that the support unit is divided into two small support frames distributed sequentially along the length of the main support plate, and the multiple auxiliary support frames and the multiple auxiliary support plates together constitute the auxiliary support structure; Step S400: On one or two of the middle support units among the plurality of support units, a cylindrical reinforcing structure is provided with the side rib of the auxiliary support frame in the support unit away from the main support plate as the axis. The reinforcing structure, the main support plate, and the auxiliary support structure together constitute a shape-controlling support structure.

2. The shape-controlled support structure design method as described in claim 1, characterized in that, Step S100 specifically includes: Step S110: Analyze the model of the large-size frame-like parts to determine the 3D printing forming direction of the large-size frame-like parts; Step S120: Set a main support plate in the area to be supported of the large frame-like component, and the height direction of the main support plate is the 3D printing forming direction.

3. The shape-controlled support structure design method as described in claim 2, characterized in that, Step S200 specifically includes: Step S210: Determine the dimensions of the main support plate; Step S220: If the length of the main support plate is greater than or equal to 300mm and the height of the main support plate is greater than or equal to 650mm and less than or equal to 1200mm, then it is determined that the auxiliary support frame will be added.

4. The shape-controlled support structure design method as described in claim 1, characterized in that, Step S400 specifically includes: Step S410: Determine the number of auxiliary support frames; Step S420: If the number of auxiliary support frames is odd, then on the middle support unit among the multiple support units, a cylindrical reinforcing structure is set with the two side edges of the auxiliary support frame in the support unit that are far from the main support plate as axes. If the number of auxiliary support frames is even, then on the two middle support units among the multiple support units, a cylindrical reinforcing structure is set with the two side edges of the two auxiliary support frames in the two support units that are far from the main support plate and adjacent to each other as axes.

5. The shape-controlled support structure design method as described in claim 1, characterized in that, The diameter of the reinforcing structure is greater than or equal to 14 mm and less than or equal to 16 mm, and the height of the reinforcing structure is the same as the height of the supporting unit.

6. The shape-controlled support structure design method as described in claim 1, characterized in that, The support unit is provided in n units, and the distance between any two adjacent support units in the n support units is set to l; The upper base of the cross-section of each support unit is denoted as 'a', and the two interior angles are denoted as 'α' and 'β'. The length of the line connecting the midpoint of the upper base of the cross-section to the midpoint of the lower base of the cross-section is denoted as 'h', and 25mm≤h≤35mm, α=β, 45°≤α≤55°. , 20mm≤l≤30mm, and Where K and b are both constants. , .

7. The shape-controlled support structure design method as described in claim 1, characterized in that, The thickness of the auxiliary support frame and the thickness of the auxiliary support plate are greater than or equal to 2 mm and less than or equal to 3 mm, respectively.

8. A shape-controlled support structure, designed using the shape-controlled support structure design method as described in any one of claims 1-7, characterized in that, The shape control support structure includes a main support plate, which is used to be placed in the area to be supported of the large-size frame-like parts, and the height direction of the main support plate is the 3D printing forming direction of the large-size frame-like parts.

9. The shape-controlling support structure as described in claim 8, characterized in that, The length of the main support plate is greater than or equal to 300 mm, and the height of the main support plate is greater than or equal to 650 mm and less than or equal to 1200 mm. The shape-controlling support structure also includes: An auxiliary support structure is provided on one side of the main support plate facing the large-sized frame-like component. It includes multiple auxiliary support frames and multiple auxiliary support plates. The auxiliary support frames are spaced apart along the length of the main support plate, and each auxiliary support frame and the main support plate combine to form a support unit with a trapezoidal cross-section. Each support unit is provided with an auxiliary support plate, such that the support unit is divided into two smaller support frames sequentially distributed along the length of the main support plate. Two reinforcing structures are inserted into the auxiliary support frame of one or two of the multiple support units located in the middle. The two reinforcing structures are symmetrically arranged, each reinforcing structure is cylindrical, and the axis of each reinforcing structure coincides with the side ridge of its corresponding auxiliary support frame that is away from the main support plate.

10. The shape-controlling support structure as described in claim 9, characterized in that, The number of auxiliary support frames is even. Two reinforcing structures are inserted one-to-one into the auxiliary support frames of the two middle support units among the multiple support units. The axes of the two reinforcing structures coincide one-to-one with two adjacent side ribs within the two auxiliary support frames that are furthest from the main support plate; or... The number of auxiliary support frames is odd. Two reinforcing structures are inserted into the auxiliary support frame of the middle support unit among the multiple support units, and the axes of the two reinforcing structures correspond one-to-one with the two side ribs of the auxiliary support frame that are away from the main support plate.

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