JP7558498B2 - Method for reinforcing layers in the stacking direction in an additive 3D printer - Google Patents

Description

The present invention relates to a method for interlayer reinforcement in the stacking direction in an additive 3D printer.

In recent years, additive 3D printers, a construction method that uses 3D printing technology to build structures by layering them up, have been developed in the construction industry both domestically and overseas. The materials used in additive 3D printers are basically cement-based, and mortar mixed in a mixer is pumped and supplied to the 3D modeling device. Construction using additive 3D printers makes it possible to layer structures without formwork, and is expected to have significant advantages over conventional concrete construction in terms of labor savings, design freedom, and safety.

Concrete structures created using additive 3D printers are created by layering cementitious materials, resulting in discontinuous layers such as cold joints between layers. The presence of these discontinuous layers can cause a decrease in strength due to brittleness between layers compared to typical concrete structures. Conventional technology has addressed this issue by inserting metallic fibers in the layering direction to reinforce the mechanical strength between layers (see, for example, Patent Documents 1 to 3).

The technology described in Patent Document 1 relates to an interlayer reinforced 3D printed concrete structure and a method for constructing the same. The construction method includes the following steps: Printing a first layer of printing material; Arranging the horizontal bars section by section along a first direction of the first layer of printed printing material for a plurality of sections of the horizontal bars; Printing a second layer of printing material gradually along the first direction as the horizontal bars are arranged, and injecting the short bars into the short bar injection positions before printing at the pre-set short bar injection positions. In this step, the horizontal bars are injected into the first layer of printing material, and the tops of the short bars are exposed from the top surface of the first layer of printing material. According to this construction method, the horizontal bars are arranged between the layers of 3D printing material and the short bars are injected, thereby effectively strengthening the adhesive properties between the layers of the printing material.

The technology described in Patent Document 2 involves inserting multiple steel fibers vertically into a concrete material with a lamellar structure.

The technology described in Patent Document 3 relates to a method for manufacturing a component from a curable material. This component manufacturing method includes the following steps: Printing at least one layer of material by a 3D printing process; Introducing a plurality of similar reinforcing elements into the layer; and Repeating the above two steps cyclically until the component is completed.

China Patent Application Publication No. 109680954 China Utility Model Application Publication No. 206233586 International Publication No. 2019/092162

Conventional techniques, including the above-mentioned patent documents, do not disclose how to insert fibers to reinforce a structure when building up a structure using 3D printing technology. For example, depending on how the fibers emerge in the stacking direction, they may impede the movement of the stacking nozzle. In other words, if the heads of the fibers protrude from an already formed stacked structure, the fibers may get in the way when the next stacked structure is formed, causing damage to the stacked structure, failing to form the stacked structure, or causing the fibers to fall out.

However, the prior art documents do not provide sufficient evidence that the interlayer portion is a mechanically weak point. Furthermore, no comparison of strength between cases where there is fiber between layers and cases where there is no fiber between layers is disclosed.

The present invention has been proposed in light of the above-mentioned circumstances, and aims to provide a method for interlayer reinforcement in the stacking direction in an additive 3D printer that can create high-quality structures by appropriately reinforcing the interlayers of the stacked structure when building structures by stacking construction materials ejected from the material ejection nozzle of the additive 3D printer.

The method for reinforcing interlayers in the stacking direction in an additive 3D printer according to the present invention has the following features in order to achieve the above-mentioned object. That is, the method for reinforcing interlayers in the stacking direction in an additive 3D printer according to the present invention is a method for building a structure by stacking construction material discharged from a material discharge nozzle of an additive 3D printer, and includes a stacking structure forming process and a reinforcing material inserting process, and is characterized in that the stacking structure forming process and the reinforcing material inserting process are repeatedly performed to build a structure.

The laminated structure forming process is a process of forming a laminated structure by discharging construction materials from a material discharge nozzle. The reinforcing material inserting process is a process of inserting a reinforcing material through the layer boundary of construction materials stacked vertically, and embedding the reinforcing material in the construction material so that the head of the reinforcing material does not protrude from the construction material located in the top layer and is completely embedded in the construction material . Note that the reinforcing material does not include those with a shape or structure having a plate-fixed member at the upper end of the shaft.

In addition, the reinforcing material insertion process can insert reinforcing material into a multi-layered laminate structure after the multi-layered laminate structure has been formed.

In addition, during the reinforcing material insertion process, it is preferable to keep the insertion angle of each reinforcing material constant when inserting the reinforcing material into the construction material.

In addition, in the reinforcing material insertion process, it is preferable that the positions of the reinforcing material to be inserted 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 are mutually different in the horizontal direction.

It is also preferable that the cross section of the reinforcing material be uniform (the cross-sectional shape and thickness do not change in the length direction) and be linear.

According to the method for reinforcing interlayers in the stacking direction in an additive 3D printer of the present invention, after construction material is discharged from a material discharge nozzle to form a stacked structure, a reinforcing material is inserted through the layer boundaries of the construction materials stacked above and below.

In this way, when building structures by stacking construction materials ejected from the material ejection nozzle of an additive 3D printer, it is possible to build high-quality structures by appropriately reinforcing the interlayers of the laminated structure.

1 is a schematic diagram of a layered 3D printer according to an embodiment of the present invention. 1 is a flowchart showing a method for reinforcing interlayers in the stacking direction in an additive 3D printer according to an embodiment of the present invention. 13 is a flowchart of a reinforcing material insertion process. Schematic diagram of a test specimen for mechanical testing. FIG. 13 is an explanatory diagram showing bending test results (comparison between the presence and absence of reinforcement material). FIG. 13 is an explanatory diagram showing bending test results (comparison between hammering and lamination).

The following describes an interlayer reinforcement method in the stacking direction in a layer-by-layer 3D printer according to an embodiment of the present invention (hereinafter, sometimes abbreviated as interlayer reinforcement method) with reference to the drawings. Figures 1 to 6 explain the interlayer reinforcement method in the stacking direction in a layer-by-layer 3D printer according to an embodiment of the present invention, with Figure 1 being a schematic diagram of a layer-by-layer 3D printer, Figures 2 and 3 being flowcharts of the interlayer reinforcement method, Figure 4 being a schematic diagram of a test specimen for mechanical testing, Figure 5 being an explanatory diagram showing bending test results (comparison between the presence and absence of reinforcement material), and Figure 6 being an explanatory diagram showing bending test results (comparison between hammering and stacking).

<Outline of interlayer reinforcement method>
An interlayer reinforcement method according to an embodiment of the present invention relates to a method for constructing a structure by stacking construction materials (e.g., cement-based materials) discharged from a material discharge nozzle 20 of an additive 3D printer 10, as shown in Fig. 1. This interlayer reinforcement method includes a stacked structure formation step (S10) and a reinforcing material insertion step (S20), as shown in Fig. 2, and is configured to construct a structure by repeatedly performing the stacked structure formation step (S10) and the reinforcing material insertion step (S20).

<Apparatus used in the interlayer reinforcement method>
As shown in Fig. 1, the layer-by-layer 3D printer 10 used in the interlayer reinforcement method according to the embodiment of the present invention mainly includes a material discharge nozzle 20 that discharges construction material, a robot arm 30 that moves the material discharge nozzle 20 to a desired position, a material supply pump 40 that supplies construction material to the material discharge nozzle 20, and a control device 50 that controls the operation of each device. The control device 50 may be a device that controls each device comprehensively, or may be a device that controls the robot arm 30, the material discharge nozzle 20, the material supply pump 40, etc. individually. Furthermore, the layer-by-layer 3D printer 10 of this embodiment is equipped with a reinforcing material insertion device 70 that inserts a reinforcing material 80 between layers of a layered structure 90 formed from a construction material.

The additive 3D printer 10 shown in FIG. 1 is a device in which the components are mounted on a mobile cart 60, but the additive 3D printer 10 used in the interlayer reinforcement method 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 building to be constructed.

<Construction materials>
The construction material is a material for constructing a structure using a 3D printer, and may be any material such as a cement-based material or a synthetic resin material, as long as the material can be discharged from the material discharge nozzle 20 and layered to construct a structure. In this embodiment, a cement-based material is used. In this embodiment, a layered structure 90 is formed by the construction material discharged from the material discharge nozzle 20, and the layered structure 90 is assembled to construct a structure.

<Reinforcing material>
The reinforcing material 80 is a material for interlayer reinforcement by being inserted between layers of the laminated structure 90 formed from construction materials, and is made of a fiber having rigidity, such as a metal or carbon-based (CFRP) fiber. The fiber used as the reinforcing material 80 in this embodiment preferably has a uniform and linear cross section so that it can be inserted straight through the layer boundary of the laminated material. Therefore, fibers with hook-shaped ends or anchors formed at the ends are not suitable. The term "uniform cross section" refers to a state in which the shape and thickness of the cross section do not change in the length direction, and refers to cylindrical or prismatic fibers with approximately the same thickness.

The fibers used as the reinforcing material 80 are inserted perpendicularly through the layer boundaries of the laminated structure 90 so as to minimize gaps between the cementitious material and the fibers when inserted into the laminated structure 90. When inserting the reinforcing material 80 into the laminated structure 90, it is preferable to insert the reinforcing material 80 so that it penetrates vertically between the layers, but it is acceptable for the reinforcing material 80 to be slightly tilted as long as no gaps are created between the laminated structure 90 and the reinforcing material 80. The reinforcing material 80 only needs to have a degree of rigidity that allows it to be inserted straight into the laminated structure 90, and may have elasticity and flexibility.

<Reinforcement material insertion device>
The reinforcing material inserting device 70 is, for example, a device such as a rice planting machine, and is capable of inserting the reinforcing material 80 straight into the laminated structure 90. That is, the reinforcing material charging device 70 may be any device as long as it can insert the reinforcing material 80 straight into the laminated structure 90, and may be appropriately changed according to various factors such as the size and shape of the construction to be constructed. The reinforcing material inserting device 70 shown in FIG. 1 is attached to the robot arm 30 and moves together with the robot arm 30, but the reinforcing material inserting device 70 and the robot arm 30 may be moved separately. The reinforcing material inserting device 70 shown in FIG. 1 inserts the reinforcing material 80 into the laminated structure 90 immediately after discharging the cement-based material (construction material) constituting the laminated structure 90. The "immediately after discharging the cement-based material (construction material) constituting the laminated structure 90" refers to a state before the cement-based material (construction material) hardens and the reinforcing material 80 cannot be inserted into the laminated structure 90.

<Laminated Structure Forming Process>
The laminated structure forming process is a process of discharging a construction material from the material discharge nozzle 20 to form a laminated structure 90. In this laminated structure forming process, the laminated 3D printer 10 is used to manufacture a laminated structure 90 of a desired shape by operating the robot arm 30 under the control of the control device 50 and discharging a cement-based material (construction material) from the material discharge nozzle 20. At this time, the construction material to be laminated is a plurality of layers, but the number of layers can be appropriately changed depending on the shape of the laminated structure 90 to be produced, the type of construction material, and the like.

<Reinforcing material insertion process>
As shown in Fig. 3, the reinforcing material insertion step is a step of inserting a reinforcing material 80 through the layer boundary between the upper and lower stacked construction materials, and embedding the head of the reinforcing material 80 into the construction material located in the uppermost layer. Note that the flowchart shown in Fig. 3 shows an example of the reinforcing material insertion step, and in the interlayer reinforcement method according to the present invention, it is not necessary to carry out the steps so as to satisfy all requirements. In this reinforcing material insertion step, once a stacked structure 90 consisting of multiple layers is produced using a reinforcing material insertion device 70 (S11), a reinforcing material 80 is inserted between the layers present in the multiple stacked structure 90.

In addition, in the reinforcing material insertion process, when inserting the reinforcing material 80 into the construction material, it is preferable to keep the insertion angle of each reinforcing material 80 constant (S12). Keeping the insertion angle of each reinforcing material 80 constant means that the insertion angles of the multiple reinforcing materials 80 inserted between the layers of the laminated structure 90 are the same for each other.

In addition, in the reinforcing material insertion step, it is preferable that the positions of the reinforcing material 80 inserted in the unit of the laminated structure 90 located in the upper layer and the unit of the laminated structure 90 located in the layer immediately below the unit of the laminated structure 90 located in the upper layer are mutually different in the horizontal direction (S13). As described above, the angle at which the reinforcing material 80 is inserted into the laminated structure 90 is preferably such that the reinforcing material 80 penetrates the interlayer portion vertically, but as long as no gap is created between the laminated structure 90 and the reinforcing material 80, the reinforcing material 80 may be slightly inclined with respect to the laminated structure 90.

The reinforcing material 80 is inserted into the laminated structure 90 at approximately the same time as the cementitious material is ejected from the material ejection nozzle 20 of the additive 3D printer 10 to form the laminated structure 90. In other words, by immediately inserting the reinforcing material 80 into a predetermined position of the formed laminated structure 90 using the reinforcing material insertion device 70 attached as an attachment to the additive 3D printer 10, the fibers can be inserted before the cementitious material hardens. This makes it difficult for the insertion position of the reinforcing material 80 to shift between the layers of the reinforcing material 80. In addition, since the reinforcing material 80 is inserted after the formation of the laminated structure 90, the operation of the material ejection nozzle 20 is not hindered.

When inserting the reinforcing material 80 into the laminated structure 90, the reinforcing material 80 is inserted so as to be completely embedded in the cement-based material layer so as not to impede the operation of the material discharge nozzle 20 when forming the next layer (upper layer) of the laminated structure 90. The reinforcing material insertion device 70 is shaped so that the reinforcing material 80 can be inserted immediately after the cement-based material is discharged from the material discharge nozzle 20. For example, a method can be adopted in which the reinforcing material 80 is inserted in a shape like a roller, as if planting rice. The reinforcing material insertion device 70 needs to be positioned so as to follow the laminated 3D printer 10. The reinforcing material insertion device 70 controls the insertion speed of the reinforcing material 80 in accordance with the movement speed of the material discharge nozzle 20.

<Evaluation of interlayer reinforcement methods>
Next, the strength evaluation of the laminated structure 90 (construction) produced using the interlayer reinforcement method of the present invention will be described. In the strength evaluation of the laminated structure 90 (construction), as shown in FIG. 4, a test specimen having dimensions of 40 mm×40 mm×160 mm was produced. In addition, steel fibers having diameters of 0.55 mm, 0.7 mm, and 1.2 mm were used as the reinforcement material 80. Then, test specimens having steel fibers with each diameter inserted inside the test specimen (referred to as S55, S70, and S120, respectively) and a test specimen without steel fibers inserted (referred to as N0) were prepared, and a three-point bending test was performed. Each test specimen was produced by inserting steel fibers between layers of cement-based materials laminated by a portal 3D printer.

The test results are shown in Figure 5. As shown in Figure 5, all test specimens with inserted steel fibers had increased strength compared to the specimens without inserted steel fibers, which shows that the strength between layers is increased by inserting steel fibers.

Figure 6 shows a comparison of the strength of a laminated test specimen created with the additive 3D printer 10 and a cast-in test specimen cast into a formwork. Both specimens have the same dimensions as the specimen shown in Figure 5, and no fibers are mixed in. As shown in Figure 6, the strength of the laminated test specimen was approximately 36% lower than that of the cast-in test specimen. This indicates that the interlayer spaces are mechanically weak points.

The mechanical data mentioned above is for the test specimen used in the experiment. However, it is reasonable to assume that the trends in the mechanical data will be apparent even if the machine (each device that makes up the 3D printer), construction materials, and various other conditions are changed.

REFERENCE SIGNS LIST 10 Layer-type 3D printer 20 Material discharge nozzle 30 Robot arm 40 Material supply pump 50 Control device 60 Mobile cart 70 Reinforcement material insertion device 80 Reinforcement material 90 Layer structure

Claims (5)

A method for constructing a structure by stacking construction materials discharged from a material discharge nozzle of an additive 3D printer, comprising:
a laminated structure forming step of discharging a construction material from a material discharge nozzle to form a laminated structure;
a reinforcement inserting process in which a reinforcement (excluding those having a shape or structure with a plate-fixed member at the upper end of the shaft) is inserted through the layer boundary of vertically stacked construction materials, and the head of the reinforcement is embedded in the construction material so as to be completely embedded in the construction material without protruding from the construction material located in the top layer ;
Including,
A method for reinforcing layers in the stacking direction in an additive 3D printer, characterized in that a construction is created by repeatedly performing the laminate structure formation process and the reinforcement material insertion process. The method for interlayer reinforcement in the stacking direction in an additive 3D printer according to claim 1, characterized in that the reinforcing material insertion process inserts the reinforcing material into the multi-layer stacked structure after the multi-layer stacked structure is formed. The method for interlayer reinforcement in the stacking direction in an additive 3D printer according to claim 1 or 2, characterized in that, in the reinforcing material insertion process, the insertion angle of each reinforcing material is kept constant when inserting the reinforcing material into the construction material. The method for interlayer reinforcement in the stacking direction in a stacking type 3D printer according to any one of claims 1 to 3, characterized in that in the reinforcing material insertion process, the positions of the reinforcing material inserted in the stacking structure unit located in the upper layer and the stacking structure unit located in the layer immediately below the stacking structure unit located in the upper layer are mutually different in the horizontal direction. The method for interlayer reinforcement in the stacking direction in a stacking type 3D printer according to any one of claims 1 to 4, characterized in that the reinforcing material has a uniform cross section and is linear.

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