Method for manufacturing structural member

Abstract

To provide a manufacturing method of a structural member capable of excellently fixing a material such as a concrete material and a reinforcing material and molding the surface of the structural member in a desired shape when the structural member such as a concrete member is manufactured.SOLUTION: The method includes a reinforcing material installation step of installing the tubular reinforcing material 32, a core portion shaping step of shaping the core portion 3 by injecting and filling the concrete material 311 (material) inside the reinforcing material 32 with the additive manufacturing apparatus 1, and a surface layer portion shaping step of shaping the surface layer portion 4 surrounding the core portion 3 by injecting the concrete material (material) around the core portion 3 with the additive manufacturing apparatus 1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a structural member. [Background technology]

[0002] Traditionally, the production of concrete components involves multiple steps performed by skilled workers, such as assembling formwork, installing reinforcing materials such as rebar, and pouring concrete. In recent years, due to concerns about a labor shortage of skilled workers, automated production of concrete components using additive manufacturing devices such as 3D printers has been put into practical use (see, for example, Patent Document 1). Material extrusion-type additive manufacturing devices that extrude concrete material are primarily used to manufacture unreinforced concrete components such as buried formwork, as they build up layers of extruded concrete material one by one. Material jetting-type additive manufacturing devices that jet concrete material are capable of jetting concrete material around reinforcing materials such as rebar, and are therefore used to manufacture concrete components with reinforcing materials placed inside.

[0003] When manufacturing concrete components with reinforcing material using a material injection type additive manufacturing device, concrete material is injected and stacked up to a predetermined height, and a worker places the reinforcing material so that the lower side is embedded in the stacked concrete material, and concrete material is then injected onto the reinforcing material from the side, or a pre-assembled reinforcing bar cage is placed on a turntable and rotated, and concrete material is injected onto the rotating reinforcing bar cage from the side. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-137992 Summary of the Invention [Problem to be solved by the invention]

[0005] When manufacturing concrete components using a material jetting additive manufacturing device, it is desirable to be able to firmly fix the reinforcing material and concrete material together, and to be able to shape the surface of the concrete component into the desired shape.

[0006] Therefore, an object of the present invention is to provide a method for manufacturing structural members such as concrete members, which can satisfactorily fix materials such as concrete materials to reinforcing materials and can also shape the surface of the structural member into a desired shape when manufacturing structural members such as concrete members. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the manufacturing method of a structural member according to the present invention includes a reinforcing material installation process in which a cylindrical reinforcing material is installed, a core forming process in which material is sprayed into the inside of the reinforcing material using an additive manufacturing device to fill it and form a core, and a surface forming process in which material is sprayed around the core using an additive manufacturing device to form a surface that surrounds the core.

[0008] In this invention, the additive manufacturing device sprays material onto the inside of the reinforcement during the core molding process, and then sprays material onto the outside of the core, which will become the exterior of the reinforcement, during the subsequent surface molding process. This ensures that the material is reliably filled inside the reinforcement, resulting in better adhesion between the reinforcement and the material, compared to methods in which the additive manufacturing device simultaneously sprays material onto both the inside and outside of the reinforcement. Because the surface of the structural component is molded in a different process than the core, the additive manufacturing device settings and materials can be changed during the surface molding process compared to the core molding process, allowing the surface to be molded into the desired shape. For example, by changing the type of material used for the core and surface, it becomes possible to design and manufacture rational, advanced structural components in terms of design, structural performance, durability, cost, and other factors.

[0009] The method for manufacturing a structural member according to the present invention may further include a surface finishing step of finishing an outer peripheral surface of the surface layer portion shaped in the surface layer portion shaping step.

[0010] This configuration allows for a good finish to be achieved on the surface of the surface layer of a structural component. For example, it is possible to smooth the surface and improve the accuracy of the finished product, which is difficult to achieve by simply spraying material in the surface layer shaping process. It can also be applied to structural components with curved shapes. By also using a tool to cut the surface of the surface layer after the surface layer shaping process in the surface finishing process, it is possible to create carved patterns on the surface of the concrete component or to drill holes for piping and wiring, thereby expanding the potential uses of structural components.

[0011] In the manufacturing method of a structural member according to the present invention, in the reinforcing material installation process, the reinforcing material is installed on an installation surface, and in the core forming process, the material is sprayed onto the area inside the reinforcing material on the installation surface, and the material is layered on top of the sprayed material.

[0012] With this configuration, the installation surface, such as the top surface of the workbench, can be used to receive the sprayed material when forming the lower end of the core, and thereafter the upper surface of the sprayed material can be used as a receiver. Therefore, there is no need to provide a dedicated member inside the reinforcing material for receiving the sprayed material when forming the lower end of the core, which simplifies the process. [Effects of the Invention]

[0013] According to the present invention, the reinforcing material and the material can be well fixed, and the surface can be shaped into a desired shape. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 10 is a perspective view of a core forming step in the manufacturing method of a structural member according to the present embodiment. [Figure 2] This is the cross-sectional shape of a concrete member. [Figure 3] FIG. 10 is a plan view illustrating the injection of concrete material in the core forming process. [Figure 4] FIG. 10 is a diagram showing the depression angle of the injection vector. [Figure 5]FIG. 10 is a diagram showing the azimuth angle of a jet vector. [Figure 6] FIG. 10 is a diagram illustrating how to determine an azimuth angle. [Figure 7] FIG. 10 is a diagram illustrating how to determine an azimuth angle when there is a bending point. [Figure 8] 10A to 10C are diagrams illustrating the progress of a core forming process. [Figure 9] FIG. 10 is a plan view illustrating the injection of concrete material in the surface layer forming process. [Figure 10] FIG. 10 is a diagram showing the depression angle of the injection vector. [Figure 11] FIG. 10 is a diagram showing the azimuth angle of a jet vector. [Figure 12] FIG. 10 is a diagram illustrating a surface finishing process. [Figure 13] 10A and 10B are diagrams showing an example of a smoothing procedure in a surface finishing process when the outer peripheral surface of the surface layer portion has a curve. DETAILED DESCRIPTION OF THE INVENTION

[0015] A method for manufacturing a structural member according to an embodiment of the present invention will be described below with reference to FIGS. As shown in Figure 1, the method for manufacturing a structural member according to this embodiment is a method for manufacturing a concrete member 2 (structural member) using an additive manufacturing device 1 that sprays a concrete material (material). In this embodiment, a long, rectangular parallelepiped concrete member 2 is manufactured. The direction in which the concrete member 2 extends is referred to as the axial direction. As shown in Figure 2, the central portion of the concrete member 2 as viewed from the axial direction is referred to as the core portion 3, and the surrounding portion is referred to as the surface layer portion 4. The concrete member 2 is manufactured with the axial direction extending in the vertical direction. The core portion 3 is in the shape of a rectangular pillar. The surface layer portion 4 is in the shape of a square tube that surrounds the core portion 3.

[0016] The core 3 has core concrete 31 and reinforcing material 32. The reinforcing material 32 has axial reinforcing bars 33 and tie bars 34. The axial reinforcing bars 33 are reinforcing bars that extend in the axial direction. A plurality of the axial reinforcing bars 33 are provided at intervals in the circumferential direction around the entire outer periphery of the core 3. The tie bars 34 are reinforcing bars that surround the axial reinforcing bars 33. A plurality of the tie bars 34 are provided at intervals in the axial direction around the entire axial direction of the core 3. The reinforcing material 32 is a cylindrical arrangement of a plurality of axial reinforcing bars 33 and tie bars 34. The core concrete 31 is concrete filled inside the reinforcing material 32, i.e., in the area surrounded by the reinforcing material 32. The core concrete 31 is formed using a concrete material 311 (material) sprayed by the additive manufacturing apparatus 1.

[0017] The surface layer 4 has a surface concrete layer 41. The surface concrete layer 41 is concrete that surrounds the outer periphery of the core 3. The surface concrete layer 41 is formed by a concrete material 411 (material) sprayed by the additive manufacturing device 1. The outer peripheral surface of the surface layer 4 corresponds to the finished surface of the concrete member 2. No reinforcing bars (reinforcement materials) are provided in the surface layer 4.

[0018] A method for manufacturing the concrete member 2 (a method for manufacturing a structural member) will now be described. First, the core 3 is formed (core forming step). In the core forming process, first, the reinforcing material 32 of the core 3 is placed on an installation surface 11 such as the top surface of a workbench (reinforcing material installation process). The reinforcing material 32 is installed in a position where the axial reinforcing bars 33 extend vertically. The installation surface 11 on which the reinforcing material 32 is installed is a horizontal plane. The concrete material 311 of the core concrete 31 is sprayed to form the core 3 (core material spraying process). The additive manufacturing device 1 sprays the concrete material 311 so that it is layered from the bottom to the top inside the reinforcing material 32. As shown in FIG. 3, the concrete material 311 is sprayed from all around the reinforcing material 32 toward the inside of the reinforcing material 32 in the direction of the arrows shown in the figure. The spray nozzle of the additive manufacturing device 1 moves in a circle around the reinforcing material 32 with its tip facing the outer periphery of the reinforcing material 32. The injection of the concrete material 311 at the bottom end of the core concrete 31 is carried out by spraying the concrete material 311 diagonally downward from the outside of the reinforcement 32 onto the area inside the installation surface 11, so as to completely fill this area with the concrete material 311. The injection of the concrete material 311 for the core concrete 31 is carried out in stages at predetermined heights. The height of the concrete material 311 injected and deposited in each stage is made approximately constant. The surface of the already layered concrete material 311 onto which the concrete material 311 is further injected is referred to as the injection surface 12.

[0019] As shown in Figures 4 to 7, the direction in which the concrete material 311 of the core concrete 31 is sprayed is preferably as follows. Hereinafter, the direction in which the concrete material 311 of the core concrete 31 is sprayed will be referred to as the spray vector A1. The angle of inclination of the spray vector A1 with respect to the horizontal plane H will be referred to as the depression angle θ1 (see Figure 4). The spray vector A1 projected onto the horizontal plane will be referred to as the spray vector horizontal component A2. An arbitrary vector with a fixed orientation on the horizontal plane will be referred to as the reference vector A3. The angle between the spray vector horizontal component A2 and the reference vector A3 will be referred to as the azimuth angle θ2. For the spray vector A1 and the depression angle θ1, see Figure 4. For the spray vector horizontal component A2, the reference vector A3, and the azimuth angle θ2, see Figure 5.

[0020] The depression angle θ1 is maintained at a constant angle. As shown in Figure 6, the azimuth angle θ2 is adjusted so that the horizontal component A2 of the jet vector maintains a constant angle with respect to the boundary line 36 of the area 35 surrounded by the reinforcement material 32. Essentially, the horizontal component A2 of the jet vector is adjusted so that it is perpendicular to the boundary line 36 of the area 35 surrounded by the reinforcement material 32. Note that, as shown in Figure 7, if the boundary line 36 of the area 35 surrounded by the reinforcement material 32 has a bend 361, a curve 362 is assumed that smoothly connects the inside of the bend 361, and the horizontal component A2 of the jet vector is adjusted to maintain a constant angle with respect to this curve 362.

[0021] At this time, it is desirable to keep constant the linear distance (injection distance) from the tip of the nozzle that injects the concrete material 311 to the point where the injection vector A1 intersects with the injection surface 12. When the concrete material 311 has accumulated to a roughly constant height on the injection surface 12, the average height is regarded as the next injection surface 12, and similar injection is carried out to further pile up the concrete material 311. In other words, as shown in Figure 8, the concrete material 311 is piled up one layer 311a at a time. The concrete material 311 of the core concrete 31 can be selected depending on the purpose. In the core material injection process, the concrete material 311 is filled at least inside the reinforcing material 32. In the core material injection process, the concrete material 311 may be added to the outside of the reinforcing material 32 as well.

[0022] Next, a surface layer forming process is carried out to form the surface layer 4. As shown in Figure 9, concrete material 411 of the surface layer concrete 41 is sprayed from the entire periphery of the core 3 toward the side of the core 3 in the direction of the arrows shown in the figure. The spray nozzle of the additive manufacturing device 1 moves in a circular motion around the core 3 with its tip facing the outer periphery of the core 3.

[0023] The direction in which the concrete material 411 of the surface concrete 41 is sprayed is referred to as the spray vector A4. See FIG. 10 for the spray vector A4. The angle of inclination of the spray vector A4 with respect to the horizontal plane H is referred to as the depression angle θ3. The spray vector A4 projected onto the horizontal plane is referred to as the spray vector horizontal component A5. See FIG. 9 for the spray vector horizontal component A5. As shown in FIG. 11, an arbitrary vector whose orientation on the horizontal plane is fixed is referred to as the reference vector A6. The angle between the spray vector horizontal component A5 and the reference vector A6 is referred to as the azimuth angle θ4.

[0024] The injection vector A4 is preferably set as follows: The depression angle θ3 is maintained so that the incident angle θ5 of the injection vector A4 with respect to the side of the core 3 is constant. If the incident angle θ5 is set to 90°, the core 3 and the surface layer 4 can be integrated, and the surface of the surface layer 4 can be smoothed. If the side of the core 3 is vertical, it is preferable to inject horizontally. The azimuth angle θ4 is set so that the horizontal component A5 of the injection vector is maintained at a constant angle with respect to the side 37 of the core 3. As with the core forming process described above, the horizontal component A5 of the injection vector and the side 37 of the core 3 are basically set to be perpendicular to each other.

[0025] At this time, it is desirable to keep constant the linear distance (spray distance) from the tip of the spray nozzle of the concrete material 411 of the surface concrete 41 to the point where the spray vector A4 intersects with the side surface 37 of the core 3. After spraying the same cross section (same height) for one or more times, shift the position up or down and spray again for one or more times in the same way.

[0026] As described above, the concrete material 311 of the core concrete 31 is filled from bottom to top, but the concrete material 411 of the surface concrete 41 can be poured in any direction, such as from top to bottom, bottom to top, right to left, left to right, or diagonally, to adhere to the concrete material 411 on the side surface 37 of the core 3. Furthermore, once the concrete material 411 of the surface concrete 41 has been sprayed onto the side surface 37 of the core 3, the same spraying of the concrete material 411 onto the side surface 37 of the core 3 can be repeated. In this case, the parameters related to the spraying of the concrete material 411 of the surface concrete 41 can be changed. The concrete material 411 of the surface layer concrete 41 can be selected depending on the purpose. That is, the concrete material 311 of the core concrete 31 and the concrete material 411 of the surface layer concrete 41 may be different materials. For example, the concrete material 411 of the surface layer concrete 41 may be a material colored with a pigment for design purposes, a material that is easy to mold such as plastering mortar for finishing, a material with high tensile strength and toughness for structural performance, or a material with high mass transfer resistance for durability.

[0027] Next, the outer peripheral surface of the surface layer 4 is finished (surface finishing process). Using a finishing tool such as a trowel, the robot performs shaping operations such as cutting and surface smoothing on the outer peripheral surface 421 of the surface layer 4 formed in the surface layer forming process shown in Figure 12. Finishing tools include trowels, trowels with rotational functions, drills, spatulas, brushes, and other tools that come into contact with the surface concrete 41 to manipulate its shape. Having the robot simultaneously hold multiple finishing tools broadens the range of shaping operations. For example, a thick, hard trowel can be used to smooth the surface of the component immediately after spraying, and then a thin, flexible trowel can be used to smooth the surface. In addition to smoothing with a trowel or trowel, patterns can be created with a spatula or brush, or holes can be drilled in the component with tools such as an drill bit or rotary drill. When smoothing with a trowel, the following procedure is recommended. First, a shape 422 is carved out that is offset approximately 1 to 2 mm outward from the target shape. While keeping the surface of the trowel in contact with the offset shape, the trowel is moved along the surface of the offset shape, and excess surface concrete 41a is cut off with the edge of the trowel. The carved-out offset shape is pressed against a shape 423 offset inward by 0.5 to 1 mm with the face of a trowel, and smoothed. The face of the trowel is tilted relative to the direction of travel so that the face of the trowel can press against the material. Excess surface concrete 41b is scraped away by the amount of inward offset, while the carved-out surface 424 is pressed with the trowel to make it smooth. This operation is repeated 2 to 3 times until the target shape is achieved.

[0028] There is no restriction on the direction in which the finishing tool can move, but when finishing a component whose cross section includes a curve, it is desirable to divide the surface layer 4 into multiple stages 43, 43... in the vertical direction, as shown in Figure 13, and for each stage, move the trowel horizontally along the outer surface of the surface layer 4 as shown by the arrow in the figure to shape the outer surface, and once the entire circumference of one stage has been smoothed, shift the trowel either vertically or horizontally and repeat the same operation.

[0029] Next, the functions and effects of the method for manufacturing a structural member according to this embodiment will be described. In the manufacturing method for a structural member according to this embodiment, in the core forming process, the additive manufacturing apparatus 1 sprays concrete material 311 onto the inside of the reinforcing member 32, and then in the subsequent surface forming process, the additive manufacturing apparatus 1 sprays concrete material 411 onto the outside of the core 3, which is the outside of the reinforcing member 32. Therefore, compared to a method in which the additive manufacturing apparatus 1 sprays material simultaneously onto the inside and outside of the reinforcing member 32, the concrete materials 311, 411 can be reliably filled onto the inside and outside of the reinforcing member 32, and the reinforcing member 32 and the concrete materials 311, 411 can be well fixed together. This makes it less likely that voids will form inside the concrete member 2, improving the quality of the concrete member 2.

[0030] Because the surface layer 4 of the concrete member 2 is formed in a different process from the core 3, the settings of the additive manufacturing device 1 and the concrete material 411 can be changed in the surface layer forming process compared to the core forming process, allowing the surface to be formed into a desired shape. For example, by changing the type of concrete material 311 for the core 3 and the concrete material 411 for the surface layer 4, it becomes possible to design and manufacture rational, advanced concrete members in terms of design, structural performance, durability, cost, etc.

[0031] The manufacturing method for a structural member according to this embodiment includes a surface finishing step for finishing the outer peripheral surface of the surface layer formed in the surface layer forming step. This configuration allows for a satisfactory finish to the surface of the surface layer 4 of the concrete member 2. For example, it is possible to smooth the outer peripheral surface of the surface layer 4 and improve the accuracy of the finished product, which is difficult to achieve by simply spraying the concrete material 411 in the surface layer forming step. This method is also applicable to forming curved surfaces on the surface of the concrete member 2. By using a tool for cutting the outer peripheral surface 421 of the surface layer 4 after the surface layer forming step in the surface finishing step, it is possible to create carved patterns on the surface of the concrete member 2 or drill holes for piping and wiring, thereby expanding the potential uses of the concrete member 2.

[0032] In the manufacturing method of the structural member of this embodiment, in the reinforcement installation step, a reinforcement 32 is installed on the installation surface 11, and in the core formation step, concrete material 311 is sprayed onto an area 35 inside the reinforcement 32 on the installation surface 11, and further concrete material 311 is layered on top of the sprayed concrete material 311. With this configuration, the installation surface 11 can be used to receive the concrete material 311 sprayed when forming the lower end of the core 3, and thereafter, the upper surface of the sprayed concrete material 311 can be used as a receiver. Therefore, there is no need to provide a dedicated member inside the reinforcement 32 to receive the concrete material 311 sprayed when forming the lower end of the core 3, which simplifies the work.

[0033] The method for manufacturing a structural member according to this embodiment is versatile because it can be applied to any concrete member whose core and surface layers can be positioned within the cross section, regardless of the shape of the concrete member. This eliminates the need to create a manufacturing method from scratch for each concrete member to be manufactured. Since concrete members with reinforcement can be manufactured automatically, the amount of work on site can be reduced, leading to labor savings. For example, when considering the construction of RC columns, if a material extrusion additive manufacturing device is used, it is necessary to place an embedded formwork of the laminate in a predetermined position and then arrange and pour reinforcement inside, but if RC columns are manufactured using the concrete member manufacturing method of this embodiment, it is only necessary to transport them to the site and install them in the predetermined position.

[0034] Although the embodiment of the manufacturing method of a structural member according to the present invention has been described above, the present invention is not limited to the above embodiment and can be modified as appropriate within the scope of the gist of the present invention. In the above embodiment, a surface finishing step is performed to finish the outer peripheral surface of the surface layer portion 4, but if finishing the outer peripheral surface of the surface layer portion 4 is not necessary, this step may not be performed. The shape of the concrete member 2 is not limited to a long rectangular parallelepiped (rectangular prism or square prism), but may be a triangular prism, a hexagonal prism, a cylindrical prism, or a shape other than a column. For example, it may be a beam or a wall member. The surface of the concrete member 2 may have a complex shape, such as a curved surface or any non-flat surface. The core 3 of the concrete member 2 may have a shape other than a square prism. The surface layer 4 of the concrete member 2 may have a shape other than a rectangular tube, as long as it surrounds the core 3. The shape of the reinforcing member 32 of the core 3 may also be appropriately set as long as it is cylindrical. The concrete member 2 and the core 3 may have a shape that is inclined or curved, in addition to a shape that extends linearly in the vertical direction.

[0035] The materials for forming the core portion 3 and the surface layer portion 4 may be selected as appropriate. For example, hydraulic mixtures are used for the concrete material 311 and the concrete material 411. Hydraulic mixtures include various cementitious materials (e.g., cement paste, mortar, concrete), geopolymer compositions, etc. The composition of the hydraulic mixture is preferably designed according to the intended use of the hardened body. Furthermore, instead of hydraulic mixtures, resins may also be used. Resins may be, for example, thermoplastic binders, resins that harden by drying when exposed to air for a certain period of time, or ultraviolet-curing resins that harden when exposed to ultraviolet light. In other words, the method for manufacturing a structural member according to the present invention may be employed when manufacturing a structural member using materials other than hydraulic mixtures.

[0036] Furthermore, composite materials can be created by adding short fibers to these materials. The short fibers can be either chemically synthesized polymer fibers or inorganic fibers. Examples of the former include polypropylene, polyvinyl alcohol, polyethylene, polyester, and aramid fibers. Examples of the latter include glass, steel, carbon, rock (e.g., basalt), ceramic, and silica fibers. The fibers used do not necessarily have to be of a single type; multiple types of fibers with different diameters, lengths, and types can be used in different mixture ratios. The added fibers can also improve the mechanical properties of the hydraulic mixture after it hardens. Specifically, they can suppress shrinkage cracking and improve compressive strength, toughness, and tensile strength and toughness.

[0037] The material used in the core filling step and the material used in the surface layer building step may be different materials.The additive manufacturing apparatus 1 used in the core filling step and the additive manufacturing apparatus 1 used in the surface layer building step may be different devices. The reinforcing material 32 may be not only conventional steel bars, but also various metal materials, continuous fibers, FRP (fiber reinforced plastic), and the like.

[0038] The Sustainable Development Goals (SDGs) are 17 international goals adopted at the United Nations Summit in September 2015. The manufacturing method for structural components according to this embodiment can contribute to achieving one of the 17 SDGs, for example, goal 9, "Create indispensable infrastructure for industry, innovation and sustainable development." [Explanation of symbols]

[0039] 1. Additive manufacturing equipment 2 Concrete members (structural members) 3 core 4 Surface layer 11 Installation surface 31 Core concrete 32 Reinforcement 311,411 Concrete materials (materials)

Claims

1. a reinforcing material installation process of installing a cylindrical reinforcing material; a core forming process in which a material is injected into the inside of the reinforcing material using an additive manufacturing device to fill the inside and form a core; A method for manufacturing a structural member, comprising: a surface layer forming process in which material is sprayed around the core using an additive manufacturing device to form a surface layer surrounding the core.

2. The method for manufacturing a structural member according to claim 1 , further comprising a surface finishing step of finishing an outer peripheral surface of the surface layer portion shaped in the surface layer portion shaping step.

3. In the reinforcing material installation step, the reinforcing material is installed on an installation surface, The method for manufacturing a structural member according to claim 1 or 2, wherein in the core forming step, the material is sprayed onto an area inside the reinforcing material on the installation surface, and the material is layered on top of the sprayed material.

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