JP7527584B2 - Method for introducing reinforcing members in the direction of material stacking in a stacking 3D printer and method for manufacturing stacked objects - Google Patents

Description

The present invention relates to a method for introducing a reinforcing member in the material stacking direction in an additive 3D printer and a method for manufacturing an additive object, and more specifically, to a method for introducing a reinforcing member in the stacking direction of the ejected laminate material (the up-down direction for laminate materials stacked above and below) when the laminate material is ejected from the material ejection nozzle of an additive 3D printer and stacked, and a method for manufacturing an additive object using the method.

Additive 3D printers have been developed that can print FRP containing reinforcing materials such as carbon fiber, making it possible to print high-strength components. Concrete structures such as buildings are reinforced with rebar to increase the bending strength of the concrete, which is weak against tensile forces, so that they can withstand vertical loads such as their own weight and horizontal loads such as earthquake loads.

The rebars in reinforced concrete are structured to transmit force via lap joints, and strength can be ensured by lining up short rebars with lap joints instead of using a single long rebar. In addition, the development of layered 3D printers that use concrete as a layering material has made it possible to create layered objects using concrete.

Conventional additive 3D printers have not had an appropriate method for introducing reinforcing members in the layering direction of the laminated material (see, for example, Patent Documents 1 to 3). Patent Documents 1 and 2 disclose a technique for forming an additive object by incorporating reinforcing fibers into a thermoplastic material and ejecting it from a print head. Patent Document 3 discloses a technique for using a mixture of short and long fibers made of synthetic resin fibers such as polypropylene fibers, polyvinyl alcohol fibers, polyester fibers, and aramid fibers molded into needle shapes, and inorganic fibers such as steel fibers, glass fibers, silica fibers, ceramic fibers, and carbon fibers, as reinforcing materials for printing raw materials such as cement-based materials.

Patent No. 6061261 Patent No. 6483113 JP 2019-147338 A

However, as with the conventional technology described above, in layered objects created using an additive 3D printer, reinforcing fibers can be introduced in the printing direction (horizontal direction), but reinforcing members such as fibers connected in the stacking direction (vertical direction) cannot be introduced. Furthermore, due to the principles of the additive 3D printer, it is not possible to connect multiple fibers, even short fibers, between stacked layers to create reinforcing members along the stacking direction.

Concrete structures cannot be recognized as buildings or structures (Building Standards Act) if they are not reinforced with rebars that can adequately resist bending loads caused by horizontal loads such as earthquakes. Therefore, there is a need to develop technology that introduces reinforcing members that can adequately resist bending loads caused by horizontal loads such as earthquakes, even in additive 3D printer-produced objects.

The present invention has been proposed in consideration of the above-mentioned circumstances, and aims to provide a method for introducing a reinforcing member in the material stacking direction in an additive 3D printer, and a method for manufacturing an additively molded object, which can easily and reliably introduce a reinforcing member into a stacked structure so that it can sufficiently resist bending loads due to horizontal loads.

In order to achieve the above-mentioned object, the method for introducing a reinforcing member in the material stacking direction in an additive 3D printer and the method for manufacturing an additively shaped object according to the present invention have the following features: That is, the method for introducing a reinforcing member in the material stacking direction in an additive 3D printer according to the present invention relates to a method for introducing a reinforcing member in the stacking direction of the ejected laminate material (a direction penetrating multiple layers of the laminate material) when the laminate material is ejected from a material ejection nozzle of the additive 3D printer and stacked.

The method of introducing a reinforcing member in the material stacking direction in this additive 3D printer includes a space forming process for forming a continuous space in the vertical direction inside the laminated structure when the laminated material is discharged from the material discharge nozzle, a reinforcing member inserting process for inserting a reinforcing member into the space, and a space filling process for filling a filler into the space into which the reinforcing member has been inserted.The method is characterized in that the reinforcing member is introduced in the stacking direction of the laminated material by repeatedly performing the space forming process, the reinforcing member inserting process, and the space filling process.

In the space forming process, each time a predetermined number of laminated materials are stacked to form a unit of laminated structure, a unit of space is formed, and the spaces of each unit are connected vertically in multiple vertically consecutive laminated units.

Furthermore, in the reinforcing member insertion process, the positions of the reinforcing members to be inserted are made different horizontally in the laminated structure unit located in the upper layer and the laminated structure unit located in the layer immediately below the laminated structure unit located in the upper layer, and the reinforcing members to be inserted are partially overlapped in the vertical direction, thereby making the reinforcing members into a lap joint shape.

In the above-mentioned method of introducing a reinforcing member in the material stacking direction in an additive 3D printer, in the space filling process, a non-filled portion in which no filler is filled is formed in the upper part of the space, and the reinforcing member can be made to protrude into the space.

The method for manufacturing a layered object according to the present invention relates to a method for manufacturing a layered object by introducing a reinforcing member in the layering direction of the layered material discharged from a material discharge nozzle of a layer-type 3D printer when the layered material is discharged from the material discharge nozzle to form a layered structure. When the layered material is discharged from the material discharge nozzle to form a layered structure, a space forming process for forming a space that is continuous in the vertical direction inside the layered structure, a reinforcing member inserting process for inserting a reinforcing member into the space, and a space filling process for filling a filler into the space into which the reinforcing member has been inserted are repeatedly performed to introduce a reinforcing member in the layering direction of the layered material to manufacture the layered object. In this case, in the space forming process, each time a predetermined number of layers of the layered material are stacked to form one unit of layered structure, one unit of space is formed, and the space of each unit is vertically connected in a plurality of vertically continuous stacked units. In addition, the reinforcing member insertion process is characterized in that the positions of the reinforcing members to be inserted are made different horizontally in the laminated structure unit located in the upper layer and the laminated structure unit located in the layer immediately below the laminated structure unit located in the upper layer, and the reinforcing members to be inserted are partially overlapped in the vertical direction, thereby making the reinforcing members into a lap joint shape.

In the manufacturing method of the layered object described above, in the space filling process, a non-filled portion is formed in the upper part of the space where no filler is filled, and the reinforcing member can be made to protrude into the space.

In the method of introducing a reinforcing member in the material stacking direction in an additive 3D printer according to the present invention, when the laminate material is discharged and stacked, a space is formed in the stacking direction of the laminate material (the direction penetrating the multiple layers of the laminate material), a reinforcing member is introduced (inserted) into the space, and the space is filled with a filler to fix the reinforcing member in place.

Therefore, according to the method of introducing a reinforcing member in the material stacking direction in an additive 3D printer of the present invention, it is possible to easily and reliably introduce a reinforcing member that can adequately resist bending loads caused by horizontal loads. Furthermore, an additive object produced by such a method can adequately resist bending loads caused by horizontal loads.

FIG. 1 is a schematic diagram of a layered 3D printer used in the present invention. 1A to 1C are explanatory diagrams showing the steps of a method for introducing a reinforcing member in the material stacking direction in an additive 3D printer according to the present invention. Schematic diagram of an additive object produced by a method for introducing a reinforcing member in the material stacking direction in an additive 3D printer according to the present invention. FIG. 11 is an explanatory diagram showing test results regarding the relationship between tensile strength and fiber volume content in a layered object. Schematic diagram of a test piece in which the reinforcing member is a lap joint. FIG. 13 is an explanatory diagram of the results of a tensile test on a test piece in which the reinforcing member is a lap joint.

The following describes a method for introducing a reinforcing member in the material stacking direction in an additive 3D printer according to an embodiment of the present invention (hereinafter, sometimes abbreviated as the reinforcing member introduction method) with reference to the drawings. Figures 1 to 6 explain the reinforcing member introduction method according to an embodiment of the present invention, with Figure 1 being a schematic diagram of an additive 3D printer, Figure 2 being an explanatory diagram showing the steps of the reinforcing member introduction method, Figure 3 being a schematic diagram of an additive model produced by the reinforcing member introduction method, Figure 4 being an explanatory diagram of test results regarding the relationship between tensile strength and fiber volume content, Figure 5 being a schematic diagram of a test piece with a reinforcing member as a lap joint, and Figure 6 being an explanatory diagram of tensile test results for a test piece with a reinforcing member as a lap joint.

<Outline of how to introduce reinforcing members>
The method of introducing the reinforcing member is to perform additive manufacturing using an additive 3D printer so that an approximately vertical hole (space) is opened in the laminated structure for introducing the reinforcing member so that reinforcing bars (reinforcing members) such as FRP members or steel bars can be introduced later.

When additive manufacturing has progressed to a predetermined number of layers, a device attached to the additive 3D printer is used to drop a reinforcing member (FRP rod or rebar) into a roughly vertical hole (space), and a filler material such as resin or concrete is injected so that the top end of the reinforcing member protrudes to a length that will allow the lap joint to be effective. When the injected filler material has hardened to a certain extent, the next reinforcing member is dropped into the hole, and the filler is injected so that the top end of this reinforcing member protrudes to a length that will allow the lap joint to be effective.

By repeating the above steps, it is possible to introduce a roughly vertical reinforcing member that is sufficiently capable of transmitting force through a lap joint into the interior of an additive model created using an additive 3D printer.

The above-mentioned method of introducing reinforcing members makes it possible to introduce reinforcing members such as fibers and reinforcing bars that can fully transmit force (especially tensile force) in the stacking direction, which could only be achieved with adhesive forces such as resin in conventional additive 3D printers, at the same time as the additive 3D printer is creating the additive object. This makes it possible to create an object that is significantly stronger against bending loads associated with tensile forces in the stacking direction and horizontal forces than additive objects created with conventional additive 3D printers.

As for the reinforcing bar joints, experiments have confirmed that sufficient strength can be obtained by joining CFRP inside resin, and they are as effective as steel bar joints in concrete, and can be used in the layering direction of objects created with an additive 3D printer.

<Layered 3D Printer>
As shown in FIG. 1, the main components of an additive 3D printer 10 used in the method of introducing a reinforcing member according to an embodiment of the present invention are a material discharge nozzle 11 that discharges a laminate material 21, a robot arm 12 that moves the material discharge nozzle 11 to a desired position, a material supply pump 13 that supplies the laminate material 21 to the material discharge nozzle 11, and a control device 14 that controls the operation of each device.

The control device 14 may be a device that controls each device overall, or may be a device that individually controls the robot arm 12, the material discharge nozzle 11, the material supply pump 13, etc. Furthermore, the layered 3D printer 10 of this embodiment is equipped with a reinforcing member introduction device 15 for introducing (inserting) a reinforcing member 23 into the space 22 formed in the layered structure 20, and a filling device 16 for filling the space 22 with a filler 24.

The additive 3D printer 10 shown in FIG. 1 is just one example, and the method of introducing the reinforcing member 23 according to the embodiment of the present invention can be modified as appropriate to suit various factors, such as the size and shape of the additive structure 20 (additive object) to be manufactured.

<Reinforcing member introduction device>
The reinforcing member introducing device 15 is a device for introducing (inserting) reinforcing members 23 into spaces 22 formed in the layered structure 20, and is configured to introduce (insert) the reinforcing members 23 one by one into the spaces 22 when a predetermined number of layered structures 20 and spaces 22 are formed. The structure of the reinforcing member introducing device 15 is not particularly limited, and can be appropriately changed according to various factors such as the scale and shape of the layered structure 20 (laminate object) to be formed, and the thickness, length, and material of the reinforcing members 23 to be introduced (inserted).

The method of introducing (inserting) the reinforcing member 23 into the space 22 can be changed as appropriate to suit various factors, such as the size and shape of the laminated structure 20 (laminated object) to be manufactured, the thickness, length, and material of the reinforcing member 23 to be introduced (inserted), and the like, such as dropping the reinforcing member 23 from above the space 22, or filling the space 22 with the filler 24 and then pushing the reinforcing member 23 into the filler 24.

<Specific example of how to introduce reinforcing members>
The method for introducing the reinforcing member 23 according to the embodiment of the present invention is a method for introducing the reinforcing member 23 in the stacking direction (direction along the stacked material 21 stacked in the vertical direction) of the stacked material 21 when the stacked material 21 is discharged from the material discharge nozzle 11 of the stacking type 3D printer 10 and stacked, as shown in FIG. 2. This method for introducing the reinforcing member 23 includes a space forming process, a reinforcing member inserting process, and a space filling process, and by repeatedly performing these processes, the reinforcing member 23 is introduced in the stacking direction of the stacked material 21. Hereinafter, each process of the method for introducing the reinforcing member will be described with reference to FIG. 2. The method for introducing the reinforcing member according to the embodiment of the present invention is performed in the order of (a) to (f) in FIG. 2.

<Space forming process>
The space forming process is a process for forming a continuous space 22 in the vertical direction inside the laminated structure 20 when the laminate material 21 is discharged from the material discharge nozzle 11 to form the laminated structure 20 (FIGS. 2(a), 2(c), and 2(e)). In this space forming process, the laminated structure 20 having the space 22 is molded.

To form the space 22 in the laminated structure 20, for example, when designing the laminated object using a CAD system, the parts of the laminated object where the strength is to be increased can be specified. The control device 14 of the additive 3D printer 10 controls the robot arm 12, material discharge nozzle 11, material supply pump 13, etc. based on the design information created using the CAD system to create a laminated object having the space 22 at the designed position.

In the space forming process of this embodiment, a predetermined number of laminated materials 21 are laminated (for example, in the case of a three-layer/lowest layer, one base layer and four laminated layers are laminated), and each time one unit of laminated structure 20 is formed, one unit of space 22 is formed, and the space 22 of each unit is vertically connected in multiple vertically consecutive laminated units. Specifically, the thickness of one layer is about 20 mm, and the diameter of the space 22 is about 5 to 8 mm. When a three-layer laminated structure 20 having the above-mentioned thickness is considered as one unit, the depth (vertical height) of one unit of space 22 is about 60 mm. Note that in the base layer located immediately above the lowest layer, a four-layer laminated structure 20 is formed, so the depth of the space 22 is about 80 mm.

<Laminated materials>
The laminate material 21 used in this embodiment is, for example, a cement-based material or a thermoplastic synthetic resin material . Note that the laminate material 21 may be any material as long as it can be solidified after being discharged from the material discharge nozzle 11, and can be appropriately changed according to various factors such as the scale and shape of the laminate structure 20 (laminate object) to be manufactured.

<Reinforcing member>
The reinforcing member 23 is a member that is inserted into the space 22 formed in the laminated structure 20 in the lamination direction (direction along the laminated materials 21 laminated in the vertical direction) of the laminated material 21 discharged from the material discharge nozzle 11 to enable the laminated structure 20 to sufficiently resist bending loads due to horizontal loads, and is made of, for example, FRP members or reinforcing bars. In this embodiment, CFRP (carbon fiber reinforced plastic) is used as the reinforcing member 23 because it is easy to obtain and process and can provide sufficient strength. Specifically, the reinforcing member 23 has a thickness of about 2 mm and a length of about 80 mm.

<Reinforcing member insertion process>
The reinforcing member inserting step is a step of inserting the reinforcing member 23 into the space 22. In this embodiment, the reinforcing member 23 is introduced (inserted) into the space 22 by the reinforcing member introducing device 15 (FIGS. 2(b) to (f)). As described above, the diameter of the space 22 is about 5 mm, and the thickness of the reinforcing member 23 is about 2 mm. Therefore, by adjusting the insertion method of the reinforcing member 23, the reinforcing members 23 positioned above and below can be positioned differently in the horizontal direction, and can be partially overlapped to form a lap joint (FIGS. 2(d) to (f)). In the example shown in FIG. 2, the reinforcing member 23 has a length equivalent to four layers, and the reinforcing members 23 arranged in the vertical direction, except for the bottom and top layers, are overlapped at the bottom and top to form a lap joint.

That is, in the reinforcing member insertion process of this embodiment, the positions of the reinforcing members 23 to be inserted are made different in the horizontal direction between the unit of the laminated structure 20 located in the upper layer and the unit of the laminated structure 20 located directly below the unit of the laminated structure 20 located in the upper layer. Furthermore, the reinforcing members 23 to be inserted are made to overlap in the vertical direction (in the form of a lap joint) between the unit of the laminated structure 20 located in the upper layer and the unit of the laminated structure 20 located directly below the unit of the laminated structure 20 located in the upper layer.

<Space filling process>
The space filling step is a step for filling the space 22 into which the reinforcing member 23 has been inserted with the filler 24 (FIGS. 2(b), (d), and (f)). In this embodiment, when filling the space 22 into which the reinforcing member 23 has been inserted with the filler 24, the filling device 16 is positioned above the space 22, and the filler 24 is injected (filled) to a predetermined height in the space 22 so that the upper portion (head) of the reinforcing member 23 protrudes from the filler 24.

In this way, a non-filled portion is formed that is not filled with the filler 24, and the reinforcing member 23 protrudes into the space 22. When the non-filled portion is formed, the upper portion of the reinforcing member 23 that has already been inserted into the space 22 and fixed by the filler 24 overlaps with the lower portion of the reinforcing member 23 to be inserted in the next reinforcing member insertion step. Then, when the filler 24 is filled into the space 22 in the reinforcing member insertion step, a portion of the reinforcing member 23 located below and the reinforcing member 23 located above overlap, forming a lap joint.

<Filling material>
The filler 24 used in the space filling step needs to be a material that can fix the reinforcing member 23 in the space 22 and generate sufficient strength in the space 22. In this embodiment, epoxy resin is used as the filler 24. Epoxy resin is suitable as the filler 24 because the hardening time and strength can be adjusted by appropriately selecting the mixture of the main agent and the hardener. Note that the filler 24 is not limited to epoxy resin, and any material may be used as long as it can fix the reinforcing member 23 in the space 22 and generate sufficient strength in the space 22.

<Layered objects>
The layered object of this embodiment is an object produced by carrying out each of the steps described above (see FIG. 3). Note that when producing the layered object, the devices and materials used in each step, and the procedure for using the devices may be changed without changing the essence of the present invention.

<Relationship between tensile strength and fiber volume content>
Next, we will explain the test results regarding the relationship between the tensile strength and the fiber volume content of a layered object manufactured using the layered 3D printer 10. Fig. 4 is a graph showing the test results regarding the relationship between the tensile strength and the fiber volume content of a layered object.

The resin was laminated to form the laminated structure 20, and a space 22 was formed in the laminated direction inside the laminated structure 20. A reinforcing member 23 was prepared by arranging CF (carbon fiber) vertically, and the reinforcing member 23 was inserted in the laminated direction of the laminated structure 20 in the space 22 and filled with epoxy resin. The tensile strength was measured using the test specimen thus manufactured and a control test specimen in which the space 22 was not formed (the reinforcing member 23 was not inserted). The carbon fiber content (V _f ) can be expressed by the following formula (1).

As is clear from Figure 4, there is a correlation between tensile strength and fiber volume content, and specimens that exceed a certain fiber volume content have increased tensile strength compared to the control specimen.

<Tensile strength test on test piece with reinforcing member as lap joint>
Next, the test results of the tensile strength test for the test pieces in which the reinforcing member is a lap joint will be described. Fig. 5 is a schematic diagram of the test piece in which the reinforcing member is a lap joint, and Fig. 6 is a graph showing the test results for each test piece.

For this tensile test, several types of test specimens were prepared, in which two reinforcing members 23 were lap-jointed near the layer boundary surface of the two-layer laminated structure 20, and a test specimen in which one reinforcing member 23 was disposed penetrating the layer boundary surface of the two-layer laminated structure 20. The specifications (carbon fiber content) of the test specimens are shown in Table 1 below. B _L is a test specimen in which the overlapping portion of the reinforcing member 23 has a length of 24 mm, and B _S is a test specimen in which the overlapping portion of the reinforcing member 23 has a length of 10 mm. In addition, in the test results shown in Figure 6, the subscripts attached to the symbols of the test specimens indicate the curing time of the first layer, with "6" indicating approximately 6 hours and "24" indicating approximately 24 hours.

As is clear from Figure 6, when the first layer of filler has reached an appropriate hardening time, if the reinforcing member 23 is embedded in the space 22 in a lap joint shape, the tensile strength is increased compared to when the reinforcing member 23 is not in a lap joint shape (when a single reinforcing member 23 is embedded through the layer boundary).

REFERENCE SIGNS LIST 10 Layer-type 3D printer 11 Material discharge nozzle 12 Robot arm 13 Material supply pump 14 Control device 15 Reinforcing member introduction device 16 Filling device 20 Layer structure 21 Layer material 22 Space portion 23 Reinforcing member 24 Filling material

Claims (4)

A method for introducing a reinforcing member in a stacking direction of a stacking material discharged from a material discharge nozzle of a stacking type 3D printer, comprising:
a space forming process for forming a space portion that is continuous in the vertical direction within the laminated structure when the laminated material is discharged from a material discharge nozzle to form the laminated structure;
a reinforcing member inserting step of inserting a reinforcing member into the space;
a space filling step of filling a filler into the space into which the reinforcing member has been inserted;
Including,
The space forming step, the reinforcing member inserting step, and the space filling step are repeatedly performed to introduce the reinforcing member in the stacking direction of the laminate material,
In the space forming step, each time a predetermined number of laminated materials are laminated to form a unit of laminated structure, a space is formed, and the space of each unit is vertically connected in a plurality of vertically consecutive laminated units,
In the reinforcing member insertion step, the positions of the reinforcing members to be inserted in the upper layer stack unit and the stack unit immediately below the upper layer stack unit are made different from each other in the horizontal direction, and the reinforcing members to be inserted are partially overlapped in the vertical direction, thereby forming the reinforcing members in a lap joint shape.
A method for introducing a reinforcing member in the material stacking direction in an additive 3D printer. In the space filling step, a non-filled portion is formed in an upper portion of the space, and the reinforcing member is made to protrude into the space.
A method for introducing a reinforcing member in a material stacking direction in an additive 3D printer according to claim 1. A method for manufacturing a layered object by introducing a reinforcing member in a layering direction of a layered material discharged from a material discharge nozzle of a layered 3D printer,
When a laminated structure is formed by discharging a laminated material from a material discharge nozzle, a space forming process is performed repeatedly to form a space that is continuous in the vertical direction inside the laminated structure, a reinforcing member inserting process is performed to insert a reinforcing member into the space, and a space filling process is performed to fill the space into which the reinforcing member has been inserted with a filler, thereby introducing a reinforcing member in the stacking direction of the laminated material and manufacturing a laminated object;
In the space forming step, each time a predetermined number of laminated materials are laminated to form a unit of laminated structure, a space is formed, and the space of each unit is vertically connected in a plurality of vertically consecutive laminated units,
In the reinforcing member insertion step, the positions of the reinforcing members to be inserted in the upper layer stack unit and the stack unit immediately below the upper layer stack unit are made different from each other in the horizontal direction, and the reinforcing members to be inserted are partially overlapped in the vertical direction, thereby forming the reinforcing members in a lap joint shape.
A method for manufacturing a layered object, comprising: In the space filling step, a non-filled portion is formed in an upper portion of the space, and the reinforcing member is made to protrude into the space.
The method for manufacturing a layered object according to claim 3 .

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