Concrete 3D printer end extrusion head, 3D printer and printing method

Abstract

The application belongs to the technical field of building 3D printing, and relates to a concrete 3D printer end extrusion head, a 3D printer and a printing method. The concrete 3D printer end extrusion head comprises a supporting cylinder and a low-resistance conveying mechanism. The supporting cylinder is a hollow cylindrical structure as a whole. The low-resistance conveying mechanism is arranged on the inner wall of the supporting cylinder in the axial direction of the supporting cylinder. The low-resistance conveying mechanism forms a material conveying channel. The application provides a concrete 3D printer end extrusion head, a 3D printer and a printing method, which can greatly reduce the resistance during material extrusion, can realize convenient extrusion of high-viscous plastic material, and have high universality and practicability.

Description

Technical Field

[0001] This invention belongs to the field of architectural 3D printing technology, and relates to a concrete 3D printer end extrusion head, 3D printer, and printing method, particularly to a concrete 3D printer end extrusion head, 3D printer, and printing method suitable for low-resistance extrusion of high-viscosity plastic materials. Background Technology

[0002] 3D printing technology has become a core technology for intelligent construction. 3D printed buildings offer advantages such as personalized customization, design freedom, and savings in labor, time, materials, and costs. Conventional 3D printing equipment is compatible with materials such as concrete, mortar, and geopolymers. Due to the specific nature of construction methods, these materials require high fluidity to ensure smooth extrusion and stable stacking, thus achieving printability and constructability. Through proper formulation or the addition of admixtures, materials like concrete, mortar, and geopolymers can achieve a certain degree of printability and constructability, enabling successful printing. However, for some highly viscous materials (such as raw soil and solidified soil), conventional 3D printing equipment often struggles to achieve smooth extrusion. This is because highly viscous materials have high viscosity, causing them to adhere to the inner wall of the extruder head during extrusion. Furthermore, the materials themselves have poor fluidity, high consistency, and high shear yield stress, resulting in significant resistance during extrusion. Existing 3D printing devices primarily use hollow tubes with circular or rectangular cross-sections as extruder heads. 3D printing materials typically undergo final mixing within the 3D printing head before being extruded by the screw. The material needs to pass through an extruder head of a certain length to achieve extrusion. Extruder heads are smaller and longer than 3D printing heads, allowing them to reach into confined spaces for material extrusion, thus making their existence necessary. However, the extrusion force provided by the screw in a 3D printing head is relatively limited, and the frictional resistance experienced by highly viscoplastic materials within the extruder head hinders their smooth extrusion.

[0003] On the other hand, since printability and constructability are contradictory properties, materials with low printability often have high constructability. In practical engineering, it is usually more necessary to improve the constructability of materials. To this end, it is necessary to solve the problem of the difficulty in smoothly printing such conventional materials with low printability (e.g., concrete, mortar, and geopolymers with low water-cement ratio (liquid-solid ratio) and insufficient water-reducing agent content). Similar to the aforementioned high viscoplasticity materials, reducing the resistance encountered by the material at the extrusion head at the end of the 3D printer is an important approach.

[0004] Most existing 3D printers for construction are concrete or mortar printers. These printers are not well-suited for highly viscoplastic materials. For example, printing on raw soil / stabilized soil requires formula adjustments or additives to achieve a stable extrusion effect, which reduces constructability. In contrast, patent number ZL202110489735.5 discloses a 3D printing machine for earthen walls and a stepping-type 3D printing machine for earthen walls, which is suitable for rammed earth construction processes. The printing process is more complex, the printing path has less freedom, and it is designed for semi-moist soil materials, which differs significantly from conventional 3D printers. Summary of the Invention

[0005] Purpose of the invention: In order to solve the above-mentioned technical problems in the background art, the purpose of the present invention is to provide a concrete 3D printer end extrusion head, 3D printer and printing method that can significantly reduce the resistance during material extrusion, enable convenient extrusion of highly viscous plastic materials and have high universality and practicality.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A concrete 3D printer end extruder includes a support cylinder and a low-resistance transmission mechanism; the support cylinder is a hollow cylindrical structure; the low-resistance transmission mechanism is arranged on the inner wall of the support cylinder along the axial direction; the low-resistance transmission mechanism forms a material transmission channel.

[0008] Preferably, the inner wall of the support cylinder used in this invention has a polygonal cross-section, and the number of sides of the polygon is M; the number of the low-resistance transmission mechanisms is N; N≤M; preferably, when N<M, the low-resistance transmission mechanisms and the inner wall of the support cylinder form a material transmission channel; when N=M, multiple low-resistance transmission mechanisms are joined together adjacently to form a material transmission channel.

[0009] Preferably, the width of the low-resistance transmission mechanism used in this invention is L1; the side length of the polygon is L2; ​​and L1 = L2.

[0010] Preferably, the concrete 3D printer end extrusion head used in this invention further includes brackets respectively disposed at the top and bottom ends of the support cylinder; the top and bottom ends of the support cylinder are respectively provided with bracket reserved holes; the axial direction of the bracket reserved holes is parallel to the axial direction of the support cylinder; the brackets are disposed on the support cylinder through the bracket reserved holes; the low resistance transmission mechanism is disposed on the bracket at the top end of the support cylinder and the bracket at the bottom end of the support cylinder.

[0011] Preferably, the low-resistance transmission mechanism used in this invention includes a conveyor belt, a first rolling shaft, and a second rolling shaft; the first rolling shaft is mounted on a bracket at the top of the support cylinder; the second rolling shaft is mounted on a bracket at the bottom of the support cylinder; the conveyor belt is wound around the first rolling shaft and the second rolling shaft; the conveyor belt passes sequentially through the first rolling shaft, the inner wall of the support cylinder, the second rolling shaft, and the outer wall of the support cylinder before returning to the first rolling shaft and repeating this cycle; when N < M, the conveyor belt and the inner wall of the support cylinder without a conveyor belt form a material transmission channel; when N = M, multiple conveyor belts are joined end-to-end along the width of the conveyor belt to form a material transmission channel.

[0012] Preferably, the low-resistance transmission mechanism used in this invention further includes a roller array disposed on the inner wall of the support cylinder; the conveyor belt passes sequentially through the first rolling shaft, the roller array, the second rolling shaft, and the outer wall of the support cylinder before returning to the first rolling shaft and thus forming a cycle; preferably, the roller array includes multiple parallel rollers; the axial direction of the rollers is perpendicular to the axial direction of the support cylinder.

[0013] Preferably, the concrete 3D printer end extrusion head used in this invention further includes a material separation device disposed at the bottom end of the support cylinder; preferably, the material separation device includes steel wire positioning components and steel wires; the steel wire positioning components are in multiple sets; the multiple sets of steel wire positioning components are evenly distributed on the bracket at the bottom end of the support cylinder; the steel wires are suspended on two adjacent sets of steel wire positioning components and are at the same height as the axis of the second rolling shaft; the steel wires are in close contact with the conveyor belt.

[0014] Preferably, the concrete 3D printer end extrusion head used in this invention further includes a print head connector disposed at the top of the support cylinder; the print head connector is an integrally hollow frame structure; the hollow structure of the print head connector matches the structure of the material transport channel; the hollow structure of the print head connector includes an extension section extending into and connecting with the material transport channel; preferably, the upper surface of the print head connector is provided with screw holes.

[0015] A concrete 3D printer including a concrete 3D printer end extrusion head as described above.

[0016] A concrete printing method based on a concrete 3D printer as described above, the printing method comprising the following steps: 1) Put the prepared materials into the material hopper of the concrete 3D printer as described above and mix them to obtain a uniformly mixed high-viscosity plastic material. 2) Move the extrusion head to make it directly contact the ground or printing platform, keep the conveyor belt stationary, start the extrusion program of the 3D printing head, and squeeze the well-mixed high-viscosity plastic material through the print head connector of the concrete 3D printer as described into the material transmission channel formed by the low-resistance transmission mechanism, continuously extruding the high-viscosity plastic material to fill the material transmission channel. 3) Raise the extruder head and continue extruding. At this time, the conveyor belt rotates freely. Observe the characteristics of the extruded strip until the shape of the extruded strip is stable and can be extruded stably and continuously. 4) Move the extruder head to the designated position and start the 3D printing process. The 3D printing head will continuously feed the highly viscous plastic material into the material transfer channel. 5) After the highly viscous plastic material gradually enters the material conveying channel, it comes into contact with the conveyor belt and drives the conveyor belt to move synchronously. 6) When the highly viscous plastic material moves to the second rolling shaft with the conveyor belt, it is cut by the steel wire placed at the bottom end of the support cylinder and close to the conveyor belt. The highly viscous plastic material adhering to the conveyor belt is discharged through the bottom end of the support cylinder. 7) Repeat steps 5) and 6) until all high-viscosity plastic materials have been extruded.

[0017] Beneficial effects: Compared with the prior art, the advantages of the present invention are:

[0018] This invention provides a concrete 3D printer end extrusion head, a 3D printer, and a printing method. The concrete 3D printer end extrusion head includes a support cylinder and a low-resistance transmission mechanism. The support cylinder is a hollow cylindrical structure. The low-resistance transmission mechanism is arranged along the axial direction of the support cylinder on its inner wall, forming a material transmission channel. The low-resistance transmission mechanism includes a non-powered rolling shaft connected to a support and a conveyor belt in direct contact with the highly viscous material. The conveyor belt serves as the inner wall of the extrusion head, and four conveyor belts form a rectangular material transmission channel. The material can move synchronously with the inner wall, preventing relative sliding between the material and the inner wall during extrusion, significantly reducing sliding friction resistance and making the extrusion of the highly viscous material smoother. Simultaneously, the inner wall of the support cylinder is an array of rollers, providing support for the conveyor belt while significantly reducing sliding friction with the inner wall of the support cylinder. A material separation device is installed at the outlet of the extrusion head. By cutting the material with a steel wire and scraping the surface of the conveyor belt, the conveyor belt is smoothly separated from the highly viscous material, allowing the highly viscous material to be extruded intact without the conveyor belt adhering to the material. This extruder head is suitable for 3D printing extrusion of highly viscous plastic materials (such as clay, raw soil, solidified soil, and low-flowability concrete / mortar). It significantly reduces the resistance generated by material movement within the extruder head and the adhesion to the extruder outlet, improving printing smoothness and quality, and solving the problem of difficult smooth printing of highly viscous plastic materials. Clearly, this invention, through a simple replacement of the extruder head component, can significantly reduce the resistance during material extrusion without changing the structure of a conventional concrete / mortar 3D printer, enabling the extrusion of highly viscous plastic materials, and possesses high versatility and practicality. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of the end extrusion head of the concrete 3D printer provided by the present invention;

[0020] Figure 2 This is a schematic diagram of the support cylinder used in the end extrusion head of the concrete 3D printer provided by the present invention;

[0021] Figure 3 This is a disassembly diagram of the remaining structure of the end extrusion head of the concrete 3D printer provided by the present invention, excluding the support cylinder.

[0022] Figure 4 This invention provides a schematic diagram and multi-angle cross-sectional views of the concrete 3D printer's end extrusion head.

[0023] Figure 5 This is a schematic diagram of the material separation device used in this invention;

[0024] Figure 6This is a 3 / 4 anatomical diagram of the internal structure of the extrusion head at the end of the concrete 3D printer used in this invention;

[0025] Figure 7 This is a schematic diagram of the longitudinal cross-sectional structure of the extrusion head at the end of the concrete 3D printer provided by the present invention;

[0026] Figure 8 This is a schematic diagram comparing the material extrusion effect of the concrete 3D printer end extruder provided by this invention with that of a traditional extruder;

[0027] Figure 9 It is a simple test method for the total resistance of the extruder head when extruding material;

[0028] in:

[0029] 1-Support cylinder; 2-Conveyor belt; 3-Bracket; 4-Print head connector; 5-Rolling shaft; 6-Material transfer channel; 7-Screw hole; 8-Bracket reserved hole; 9-Roller array; 10-Wire positioning component; 11-Wire. Detailed Implementation

[0030] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0031] The principle of this invention is as follows: During 3D printing, highly viscous plastic material comes into direct contact with the inner wall of the extruder head. This material easily adheres tightly to the inner wall, forming a thin film. Because the film is tightly bonded to the inner wall, it cannot move. Therefore, extrusion requires continuous shearing between the material in the center and the film at the edges. However, highly viscous plastic material has a high shear yield strength, resulting in significant resistance when passing through a slender extruder head during 3D printing. Based on this, this invention proposes a novel extruder head that reduces extrusion resistance and improves extrusion efficiency by preventing relative sliding between the highly viscous plastic material and the inner wall of the extruder head. Specifically, see [link to specific details]. Figure 1This invention provides a concrete 3D printer end extruder, comprising a support cylinder 1 and a low-resistance transmission mechanism. The support cylinder 1 is a hollow cylindrical structure. The low-resistance transmission mechanism is arranged along the axial direction of the support cylinder 1 on its inner wall, forming a material transmission channel 6. In practical use, the high-viscosity plastic material gradually enters the material transmission channel 6, contacts the low-resistance transmission mechanism, and moves synchronously with it, significantly reducing the resistance generated by the material in the extruder. It should be noted that this invention differs from existing methods that regulate material rheological properties through formulation design or additives. This invention addresses the problem of excessive resistance experienced by high-viscosity plastic materials at the 3D printing end extruder by designing an end extruder that avoids the resistance experienced by the high-viscosity plastic material on the inner wall of the support cylinder 1 by allowing the low-resistance transmission mechanism to move together with the material. For example, the high viscoplasticity material mentioned in this invention has low flowability, and the flowability measured by the strip table method should be below 140 mm. Therefore, it will not flow downwards due to gravity inside a conventional fixed extrusion head. The moisture content of the high viscoplasticity material should not be too high, and bleeding should not occur.

[0032] The inner wall of the support cylinder 1 used in this invention has a polygonal cross-section with M sides; the number of low-resistance transmission mechanisms is N; N≤M; preferably, when N<M, the low-resistance transmission mechanisms and the inner wall of the support cylinder 1 form a material transmission channel 6. For example, N=1, M=4. In this case, the highly viscous plastic material is in contact with one low-resistance transmission mechanism and simultaneously with the other three inner walls of the support cylinder 1. Although this method uses only one low-resistance transmission mechanism, since the low-resistance transmission mechanism moves together with the highly viscous plastic material (there is continuous shearing between it and the other three inner walls), the resistance experienced by the highly viscous plastic material on the inner wall of the support cylinder 1 is reduced. To further reduce the resistance experienced by the highly viscous plastic material on the inner wall of the support cylinder 1, this invention adopts the N=M mode, and the N=M mode will be used in the following detailed description. When N=M, multiple low-resistance transmission mechanisms are joined together to form the material transmission channel 6. The highly viscous plastic material comes into contact with all the low-resistance transmission mechanisms and moves together with them, directly avoiding the resistance encountered by the highly viscous plastic material on the inner wall of the support cylinder 1. For example, depending on the specific forming requirements, the cross-section of the inner wall of the support cylinder 1 can be triangular, rectangular, or hexagonal. For ease of explanation of the technical solution provided by this invention, in subsequent experiments and embodiments, a rectangular cross-section will be used for illustration. Figure 1 as well as Figure 2 As shown. Of course, other cross-sections disclosed in this invention can also be used.

[0033] To ensure that highly viscous plastic materials can be extruded normally and without omission, the width of the low-resistance transmission mechanism used in this invention is L1; the side length of the polygon is L2; ​​L1=L2.

[0034] See Figure 1 , Figure 3 , Figure 4 as well as Figure 6 The concrete 3D printer extruder head provided by this invention also includes brackets 3 respectively disposed at the top and bottom ends of the support cylinder 1; bracket pre-drilled holes 8 are respectively provided at the top and bottom ends of the support cylinder 1; the axial direction of the bracket pre-drilled holes 8 is parallel to the axial direction of the support cylinder 1; the brackets 3 are disposed on the support cylinder 1 through the bracket pre-drilled holes 8; a low-resistance transmission mechanism is disposed on the brackets 3 at the top and bottom ends of the support cylinder 1. For example, the brackets 3 used in this invention are made of hollow metal (alloy, round tube) material, which has high strength and deformation resistance to ensure the stability and strength of the overall structure of the extruder head. The brackets are detachable to facilitate the installation and removal of the support cylinder, conveyor belt, and rolling shaft on the brackets 3. For example, bracket pre-drilled holes 8 are provided at the four corners of the support cylinder 1, allowing the vertical uprights of the brackets 3 to pass through the support cylinder 1, forming a stable structure.

[0035] See Figure 1 , Figure 3 , Figure 6 as well as Figure 7The low-resistance transmission mechanism used in this invention includes a conveyor belt 2 and a rolling shaft 5. The rolling shaft 5 includes a first rolling shaft and a second rolling shaft. The first rolling shaft is mounted on a bracket 3 at the top of the support cylinder 1, and the second rolling shaft is mounted on a bracket 3 at the bottom of the support cylinder 1. The conveyor belt 2 is wound around the first rolling shaft and the second rolling shaft. The conveyor belt 2 passes sequentially through the first rolling shaft, the inner wall of the support cylinder 1, the second rolling shaft, and the outer wall of the support cylinder 1 before returning to the first rolling shaft and repeating this cycle. For example, the rolling shaft 5 used in this invention is made of plastic and is connected to the bracket 3 via a bearing. The diameter of the rolling shaft 5 is determined based on the flexibility of the conveyor belt 2 and the overall size of the extruder head, and should not be too large or too small. The length of the rolling shaft 5 is determined by the inner diameter of the extruder head, which is the design width of the 3D printed extruded strip. The outer surface of the rolling shaft 5 is designed with rough, granular protrusions to increase friction with the conveyor belt 2, preventing slippage between the rolling shaft and the conveyor belt. For example, the support 3 used in this invention includes four columns, two sets of upper and lower crossbeams, and a top printhead connector. Each set of crossbeams consists of four round tubes for fixing the rolling shafts 5. Four steel wire positioning pieces 10 are fixed at the four corners of the bottom of the support 3. The connector at the top of the support 3 is the connector between the extrusion head and the 3D printing head (the front end device of this invention), and also the converter between the conventional fixed channel and the conveyor belt channel of this invention. The connector has four screw holes for bolt connection with a conventional 3D printing head. Eight upper and lower rolling shafts 5, set on the four side walls of the support cylinder 1, are fixed on the upper and lower sets of crossbeams of the support 3. Bearings are installed inside the rolling shafts to allow them to rotate freely. The conveyor belts 2 are arranged on the upper and lower rolling shafts 5. The four sets of conveyor belts 2 surround each other to form a rectangular transmission channel, i.e., the material transmission channel 6, in which highly viscous plastic materials are extruded.

[0036] It should be noted that, according to the aforementioned description, when N < M, the conveyor belt 2 and the inner wall of the support cylinder 1 (where no conveyor belt 2 is installed) form the material transfer channel 6; when N = M, multiple conveyor belts 2 are joined end-to-end along the width of the conveyor belt 2 to form the material transfer channel 6. It should also be noted that both the first and second rolling shafts are unpowered rolling shafts, while the conveyor belt 2 directly contacts the highly viscous plastic material. That is, as the highly viscous plastic material falls freely, the conveyor belt 2 moves synchronously, thus preventing relative sliding between the highly viscous plastic material and the inner wall of the support cylinder 1 during extrusion. The conveyor belts are not connected to each other and can move freely and smoothly on their own. This prevents relative sliding between the highly viscous plastic material and the inner wall during extrusion, significantly reducing sliding friction resistance and making the extrusion of the highly viscous plastic material smoother. That is, the present invention uses a freely rotating conveyor belt 2. Therefore, when the highly viscous plastic material passes through the extrusion head of the present invention, the highly viscous plastic material does not slide relative to the inner wall of the support cylinder 1, which greatly reduces the resistance during material extrusion and allows the material to move smoothly downward under the action of extrusion force and its own weight, thereby greatly improving the extrusion efficiency of the highly viscous plastic material. It should be noted that the preferred embodiment of the present invention is formed by four independent conveyor belts 2 arranged on the inner wall (rectangular cross-section) of the support cylinder 1, with no connection between adjacent conveyor belts 2 and gaps existing between them. Due to the support cylinder 1, the conveyor belts 2 do not bend or deform under the support of the support cylinder 1. Therefore, the inner wall of the extrusion head can maintain a prismatic space without deformation, preventing side leakage of the highly viscous plastic material, and the leakage amount of the material is controllable. The conveyor belt 2 can be made of rubber, which has good deformability and wear resistance. The outer surface of the conveyor belt 2 used in the present invention, especially the edges, can be treated with wear resistance to resist the wear caused by long-term contact and friction between the conveyor belt and the steel wire 11. A wear-resistant granular layer is formed by hot-pressing and vulcanizing a polymer material on the rubber surface. Alternatively, polymer wear-resistant strips can be added to the edge of the conveyor belt as a sacrificial layer to reduce direct friction between the belt and the steel wires 11. Exemplarily, the outer surface of the conveyor belt 2 used in this invention may have a texture to enhance the adhesion between the conveyor belt and the material, preventing relative slippage. The texture of the conveyor belt 2 is concave to avoid conflict between the convex texture and the steel wires 11. The texture can consist of dots and curves, such as a dense dot matrix or wavy lines. The texture is distributed along the length of the conveyor belt and should remain smooth at the edges to prevent the conveyor belt from engaging with the steel wires 11, thus hindering the movement of the conveyor belt. After installation, the conveyor belt 2 should be taut and not loose.

[0037] See Figure 2 , Figure 6 as well as Figure 7The low-resistance transmission mechanism employed in this invention further includes a roller array 9 disposed on the inner wall of the support cylinder 1; the conveyor belt 2 sequentially passes through the first rolling shaft, the roller array 9, the second rolling shaft, and the outer wall of the support cylinder 1 before returning to the first rolling shaft, thus forming a cycle. For example, the roller array 9 includes multiple parallel rollers; the axial direction of the rollers is perpendicular to the axial direction of the support cylinder 1. The roller array 9 is arranged on the four inner walls of the support cylinder 1, each side consisting of several small-diameter rollers densely arranged. The length of the small-diameter rollers is consistent with the width of the conveyor belt 2 on that side, and a small gap is reserved between adjacent upper and lower rollers so that the small rollers do not obstruct each other when rotating. The smaller the diameter of the small rollers, the more uniform the lateral support force provided. The axis of the small-diameter rollers is connected to the support cylinder 1, allowing the small-diameter rollers to roll freely and smoothly, providing lateral support force to the conveyor belt without sliding friction with it, enabling the conveyor belt to move with low resistance and without large deformation when transporting materials. Clearly, the purpose of the roller array 9 is to provide support for the conveyor belt 2 while significantly reducing sliding friction with the inner wall of the support cylinder. At the same time, the conveyor belt 2 itself has a certain degree of rigidity, so that it does not undergo large deformation in the gaps where the roller array 9 provides support.

[0038] In 3D printing technology, the material ultimately needs to separate from the extruder. Traditional extruders rely on the continuous movement of the material, which naturally separates from the extruder outlet. However, this separation method can generate tearing forces on the material, easily leading to uneven material surfaces and affecting print quality. See also Figure 4 , Figure 5 , Figure 6 as well as Figure 7The concrete 3D printer extruder head provided by this invention also includes a material separation device disposed at the bottom end of the support cylinder 1; preferably, the material separation device includes steel wire positioning elements 10 and steel wires 11; there are multiple sets of steel wire positioning elements 10; multiple sets of steel wire positioning elements 10 are evenly distributed on the bracket 3 at the bottom end of the support cylinder 1; the steel wires 11 are suspended on two adjacent sets of steel wire positioning elements 10 and are at the same height as the axis of the second rolling shaft; the steel wires 11 are in close contact with the conveyor belt 2. By cutting the highly viscous plastic material and scraping the surface of the conveyor belt 2, which plays a role in conveying, the conveyor belt 2 is smoothly separated from the highly viscous plastic material, the highly viscous plastic material is extruded in an intact state, and the conveyor belt 2 does not stick to the highly viscous plastic material. It should be noted that the conveyor belt 2 significantly reduces sliding friction resistance during movement through roller transmission. The high-viscosity plastic material separation device at the end efficiently separates the material from the surface of the conveyor belt 2 by cutting with steel wire 11, allowing the high-viscosity plastic material to be completely extruded without any residue adhering to the conveyor belt 2. The conveyor belt 2 then turns along the rollers, leaving the high-viscosity plastic material behind. For example, the steel wire 11 passes through the steel wire positioning member 10. In the horizontal direction, the steel wire 11 is arranged close to the conveyor belt 2, and after being pulled, the steel wire 11 intersects each other to form a "U" shape. In the vertical direction, the steel wire 11 is arranged at the same height as the axis of the lower rolling shaft, that is, at the point where the inner wall plane on one side of the extrusion head is tangent to the roller on that side. The steel wire positioning parts 10 are welded to the four corners of the lower side of the bracket 3. The height of the center of the hole in the steel wire positioning part 10 is the same as the height of the axis of the lower rolling shaft. The steel wire 11 is positioned at this height, which allows the highly viscous plastic material to be cut as it leaves the extruder outlet, and then separated from the conveyor belt 2. The tension of the steel wire 11 is adjustable. By tensioning and fixing the end of the steel wire 11, the steel wire 11 can be tightened to maintain a good cutting effect. This invention uses a thin steel wire at the end to physically separate the highly viscous plastic material from the extruder surface by cutting, avoiding tearing and cracking of the highly viscous plastic material. The cut surface is smoother, ensuring the quality of 3D printing.

[0039] See Figure 1 , Figure 3 , Figure 4 , Figure 6 as well as Figure 7The concrete 3D printer end extrusion head provided by this invention also includes a print head connector 4 disposed at the top end of the support cylinder 1. This print head connector 4 is used for fixed connection with a general 3D print head. The print head connector 4 is an integrally hollow frame structure; the hollow structure of the print head connector 4 matches the structure of the material transfer channel 6; the hollow structure of the print head connector 4 includes extension sections extending towards and connecting with the material transfer channel 6. It should be noted that each extension section directly forms the inner wall of the extrusion head, serving as a transitional inner wall between the inner wall of the 3D print head and the rolling inner wall of the extrusion head. A gap exists between the fixed inner wall and the rolling inner wall, with a gap width not exceeding 1mm, to prevent material leakage without affecting the transmission of the conveyor belt 2. The height of the fixed extrusion head inner wall included in the print head connector 4 is related to the roller diameter, ensuring that the gap between the fixed inner wall and the rolling inner wall is controllable, allowing material to be smoothly transferred from the fixed inner wall to the rolling inner wall without material leakage. In addition, the upper surface of the printhead connector 4 used in this invention is provided with screw holes 7, which can be bolted (exemplarily by no less than four bolts) to the printhead of a general 3D printer.

[0040] For example, based on the extrusion head of the concrete 3D printer provided by the present invention, a gear can be installed on the side of each rolling shaft 5. The gear shaft is on the same straight line as the support shaft. The gear is fixedly connected to the rolling shaft and rotates synchronously with the rolling shaft. The gears of adjacent rolling shafts mesh with each other. Under the transmission action of the gear, all rolling shafts can rotate at the same speed, thereby realizing the synchronous movement of the four conveyor belts and improving the uniformity of material extrusion. At the same time, based on this mechanism, a motor can be installed on the support. The motor extends a drive gear, which meshes with the gear of a certain rolling shaft. In this way, the rotation of the rolling shaft and the conveyor belt can be actively controlled by the motor drive, including forward rotation, stop and reverse rotation, as well as active adjustment of the rotation speed, thereby realizing active control of the material transmission speed and state.

[0041] In the actual extrusion process, the print head needs to be moved to the ground (or directly contact the printing platform) first, using friction to keep the conveyor belt stationary. Then, the 3D print head is run, allowing material to be continuously extruded without contact for a period of time, filling the material transport space. When material continuously seeps out from the bottom, it indicates that the material transport space has essentially filled the entire space. At this point, the extrusion head is raised, and the no-load extrusion operation continues, observing the characteristics of the extruded strip for issues such as large air pockets or extrusion interruptions. This helps to eliminate defects from the previous operation. During this process, the extrusion speed of the print head needs to be adjusted until the characteristics of the extruded strip stabilize, ensuring that the material extrusion speed and flow rate of the print head are equal to those of the extruder head. Then, the extrusion head can be moved to the designated position to begin the actual extrusion. The above pre-printing preparations are crucial steps to ensure print quality.

[0042] It is important to note that this step is also present in traditional concrete 3D printing extrusion heads, as it is a necessary step to ensure printing quality.

[0043] The principle is that, on the one hand, highly viscoplastic materials have high viscosity, which allows them to adhere tightly to the conveyor belt without relative slippage; on the other hand, due to their poor flowability and deformability, highly viscoplastic materials naturally act as a regulator of the conveyor belt's speed. Especially when the material conveying space is full, the material passing through the narrow conveyor channel ensures that the conveyor belt moves at a constant speed.

[0044] Additionally, it's important to note that material leakage or spontaneous detachment is virtually nonexistent during the printhead's movement (when the 3D printhead is not performing extrusion). This is because the material targeted by this invention is highly viscous and highly plastic; therefore, extrusion relies not only on the material's own gravity but also on the printhead's thrust. When this type of material fills the material transport channel, it remains bonded to the unextruded material within the printhead. Consequently, the material does not automatically detach during printhead movement but is extruded under the combined effect of gravity and thrust as the printhead continues to extrude.

[0045] Obviously, the concrete 3D printer extruder head provided by this invention is suitable for 3D printing extrusion of highly viscoplastic materials (such as clay, solidified soil, geopolymers, low-flowability concrete, and mortar). These materials have poor flowability (flow rate below 140mm) and easily adhere to the inner wall of the extruder head, making extrusion difficult and resulting in poor printing quality. This invention, by transforming the fixed inner wall into a movable conveyor belt-type inner wall, allows the material to move synchronously with the inner wall, significantly reducing the resistance generated by the material in the extruder head. Simultaneously, a separation device is incorporated to cut and separate the material from the conveyor belt upon successful extrusion, greatly reducing material adhesion to the extruder head outlet. This improves printing smoothness and quality, solving the problem of difficult smooth printing of highly viscoplastic materials.

[0046] In addition to providing the concrete 3D printer end extruder as described above, this invention also provides a concrete 3D printer including the concrete 3D printer end extruder as described above. The concrete 3D printer is used in the following manner: 1) Put the prepared material into the material hopper of the concrete 3D printer (it should be noted that the material hopper is a component of the 3D printer, and the structure and connection method of the material hopper are all existing technologies, which will not be described in detail here) and mix it to obtain a uniformly mixed high-viscosity plastic material. 2) Move the extrusion head to make it directly contact the ground or printing platform, keep the conveyor belt 2 stationary, start the extrusion program of the 3D printing head, and squeeze the well-mixed high-viscosity plastic material through the print head connector 4 of the concrete 3D printer as described above into the material transmission channel 6 formed by the low-resistance transmission mechanism, continuously extruding the high-viscosity plastic material to fill the material transmission channel. 3) Raise the extruder head and continue extruding. At this time, the conveyor belt rotates freely. Observe the characteristics of the extruded strip until the strip shape is stable and can be extruded continuously. 4) Move the print head to the designated position and start the 3D printing process. The 3D print head will continuously feed the highly viscous plastic material into the material transfer channel 6. 5) After the highly viscous plastic material gradually enters the material conveying channel 6, it comes into contact with the conveyor belt 2 and drives the conveyor belt 2 to move synchronously. 6) When the highly viscous plastic material moves with the conveyor belt 2 to the second rolling shaft, it is cut by the steel wire 11 placed at the bottom end of the support cylinder 1 and closely attached to the conveyor belt 2. The highly viscous plastic material attached to the conveyor belt 2 is discharged through the bottom end of the support cylinder 1. 7) Repeat steps 5) and 6) until all high-viscosity plastic materials have been extruded.

[0047] To demonstrate that the technical solution provided by this invention has the preferred effect, the following experiment was conducted: 1) Structure of the extruder head (hereinafter referred to as the extruder head) of the concrete 3D printer. The printing extrusion nozzle is a rectangular square hole with dimensions of 40mm × 40mm, meaning the width of the printing strip is 40mm, and the cross-sectional dimensions of the material transport channel 6 are 40mm × 40mm. To facilitate the extruder head's insertion into narrow spaces for printing, the length of this extruder head is 150mm, meaning the straight section length of the conveyor belt 2 (equal to the axial distance between the two upper and lower rolling shafts 5) is 150mm. The support 3 is made of hollow metal tubing with an outer diameter of 6mm and a thickness of 2mm. The rolling shaft 5 has an outer diameter of 16mm, a length of 40mm, and is made of plastic, with the metal tubing of the support 3 connected internally. The conveyor belt 2 is made of rubber with a thickness of 2mm, a width of 40mm, and a circumference of approximately 555mm, allowing it to be tightly arranged between the two rolling shafts 5. The support cylinder 1 is made of plastic, with a height of 130mm, an outer diameter of 74mm×74mm, and an inner diameter of 40mm×40mm. Four pre-drilled holes 8 with an inner diameter of 6mm are provided at the four corners. Four sets of roller arrays 9 are arranged inside the support cylinder 1. Each roller array consists of 32 small rollers with a diameter of 4mm and a length of 40mm. The axis of each small roller is fixed to the support cylinder 1. The print head connector 4 and the bracket 3 are both made of metal and are fixedly connected. The top of the print head connector 4 is 3mm thick, with four 2mm diameter screw holes 7 pre-drilled at the top for bolt connection to the 3D printing head. The inner side plate of the print head connector 4 is 1mm thick and 13mm high, with a gap of less than 1mm between the side plate and the conveyor belt. The steel wire positioning component 10 is welded and fixed to the four corner points on the lower side of the bracket 3. The height of the center of the hole of the steel wire positioning component 10 is at the same height as the axis of the lower rolling shaft 5, and the arrangement height of the steel wire 11 is positioned at this height.

[0048] 2) Extruded Material. The high-viscosity plastic material used in this printing was clay. 3D printing clay is a new type of building technology that combines earthen architecture with intelligent construction. The clay was excavated from a depth of less than 1 meter underground, with an organic matter content of less than 2%, a clay content of 55%, a plastic limit of 31%, a liquid limit of 52%, and a plasticity index of 21. It belongs to high liquid limit clay. The water content at the time of printing was 45%, and the fluidity was only 135mm. The clay in this state has high buildability, but extremely poor printability.

[0049] 3) Extrusion Method. At the start of printing, the prepared material is fed into the material chamber of the 3D printer and stirred. The material is then extruded through a screw. The extrusion head of this invention is pre-connected to the print head of the 3D printer with bolts to ensure the conveyor belt is securely fixed. During the actual extrusion operation, the print head is initially brought to the ground, and friction is used to keep the conveyor belt stationary. At this point, the extrusion head functions no differently from a traditional extrusion head. Empty extrusion is then performed for a period to allow the material to fill the entire material transport space. The material contacts the surfaces of the four conveyor belts, thus regulating their synchronous operation. Then, the extrusion head is raised, and empty extrusion continues, observing the characteristics of the extruded strip until its shape is stable and it can be continuously extruded. Then, 3D printing is started.

[0050] At the start of 3D printing, the material is extruded from the 3D printing head, passes through the print head connector 4, and further reaches the material transport channel 6 formed by the conveyor belts 2. Upon contact with the conveyor belts 2, the highly viscous material immediately drives them to move. At this point, the shear resistance experienced by the material initially in contact with the conveyor belts 2 is significantly reduced, with gravity being the primary force. Due to the viscosity of the highly viscous material, the cohesive force of the material above cancels out the force of gravity, thus preventing the material initially in contact with the conveyor belts 2 from falling rapidly. As more material enters the material transport channel 6, the force of gravity becomes more pronounced. However, because the extrusion head of this invention significantly reduces resistance, the material accelerates its descent under gravity and, through cohesive force, accelerates the extrusion of the material above. Throughout the process, the material moves synchronously with the inner wall of the conveyor belts 2. Because the material does not slide relative to the inner wall during extrusion, the resistance during extrusion is significantly reduced. During extrusion, the material exerts lateral pressure on the conveyor belt 2, while the roller array 9 on the inner wall of the support cylinder 1 provides lateral support. The rolling of the small rollers eliminates the sliding friction resistance between the conveyor belt 2 and the support cylinder 1, thus ensuring that the material transport channel 6 remains undeformed during operation and that the conveyor belt 2 operates with low resistance. When the material reaches the outlet of the extruder head, it contacts the steel wire 11 for cutting. The material continues to be extruded vertically downwards, exiting the extruder head and smoothly reaching the designated location for deposition and stacking. The conveyor belt 2 then rotates along the rolling shaft 5 into the next cycle, continuing to contact new material. At this point, the extruder head of the present invention enters a continuous working state, and the conveyor belt 2 begins to rotate continuously, continuously contacting new material and delivering it to the outlet of the extruder head to complete the cutting of the steel wire 11. Due to the neat cutting by the steel wire 11, the highly viscous material is extruded in a complete state, and the conveyor belt 2 does not adhere to the material.

[0051] 4) Experimental results. Figure 8 The schematic diagram shows a comparison of the extrusion effect using the low-resistance extruder head of this invention and a conventional fixed extruder head. Figure 8The two extrusion heads shown are compared across various performance parameters to analyze the advantages of the extrusion head of the present invention in reducing resistance and improving extrusion quality. See also Figure 8 On the right, printing using a traditional screw extrusion 3D printer results in insufficient extrusion force and high resistance in typical extrusion heads, leading to difficult extrusion, poor continuity, and poor quality of the extruded ribbon, with numerous edge tears. (See also...) Figure 8 On the left, the extrusion head provided by this invention has low resistance after extruding the material, and the extruded strip does not tear, resulting in very good quality.

[0052] The testing methods for extrusion force and total resistance are as follows: Figure 9 The simple device shown was used for testing.

[0053] The test principle is as follows: In the actual printing process, the 3D printing head gives the extrusion force of the material, denoted as F. The total resistance of the material includes the friction force and viscosity force between the material and the side wall of the extrusion head, and the total resistance is denoted as f. This force is opposite to the direction of material movement. The total mass of the material in the extrusion head is M, and its total gravity is G. Then there is the force balance relationship of equation (1).

[0054] exist Figure 9 In the simplified testing apparatus, the extruder head is inverted and bolted to the ground. Material is loaded into the extruder head, filling it completely. To prevent material from leaking out from the bottom under gravity, a base plate is placed at the bottom of the material. A tension line is used to push the material upwards; the line is taut and embedded in the material, with one end connected to the base plate and the other end connected to a tension gauge. The tension gauge records the tension on the line in real time during the test, denoted as T.

[0055] The base plate is made of wood, plastic, or iron, with a bottom area slightly smaller than the internal channel area of ​​the extruder head, measuring 30mm x 30mm, leaving a gap of approximately 5mm between the base plate and the inner wall of the extruder head. The drawstring is made of plastic, steel wire, fishing line, etc., and is required to have high tensile strength and modulus of elasticity.

[0056] After the experiment begins, the tension wire is lifted vertically at a speed of 1 cm / s to 5 cm / s. This speed should be equivalent to the material extrusion speed during actual 3D printing. Record the reading T on the tension gauge and plot the relationship curve between time t and tension T. Wherein, tension T, total material weight G, and the weight of the tension wire and the base plate are G1, and the total resistance is f. Then, the force balance relationship shown in equation (2) is obtained.

[0057] In the T-t relationship curve, T initially rises rapidly to its maximum value, then decreases slightly and fluctuates within a constant range. This maximum value is recorded as the maximum tension value, and the average value within the constant fluctuation range is the dynamic tension value. This simplified test selects the dynamic tension value as the tension T for calculating the total resistance.

[0058] F+G=f (1)

[0059] T = G + G1 + f (2)

[0060] After the test is completed, the extruder head is removed and weighed to obtain the total mass M1 of the extruder head and the residual material. After deducting the total mass M0 of the extruder head itself, the mass of the residual material can be obtained. The material residue rate R can be calculated according to formula (3).

[0061] (3)

[0062] In actual 3D printing, a straight strip is continuously extruded using different extrusion heads. To evaluate the extrusion effect of different extrusion heads, the strip is divided into six equal parts, and the strip width d at five of the six division points is measured. i The extrusion effect evaluation parameter K, i.e., the width non-uniformity coefficient of the extruded strip, is obtained by calculating the strip width d (generally the width of the extruder head) according to Equation (4). The smaller K is, the better the extrusion effect, the more uniform the thickness of the printed strip, and the closer it is to the design width. In this embodiment, n is 5 and d is 40mm in Equation (4).

[0063] (4)

[0064] This embodiment tests the extruder of the present invention and a traditional extruder (both with an inner diameter of 40mm×40mm and a height of 150mm) using soil, cement-stabilized soil, and mortar. The test results for the four parameters are shown in Table 1.

[0065] The soil was excavated from a depth of 1 meter or more underground. It is classified as high liquid limit clay, with an organic matter content of less than 2%, a clay content of 55%, a plastic limit of 31%, a liquid limit of 52%, a plasticity index of 21, a water content of 45%, a flowability of 135 mm, and a density of 1892 kg / m³. 3 .

[0066] Cement-stabilized soil is prepared using the aforementioned soil. Dry soil, cement, and water are mixed in a mass ratio of 1:0.15:0.5 to produce cement-stabilized soil with a fluidity of 138 mm and a density of 1934 kg / m³ in its fresh state. 3 .

[0067] The mortar is a standard cement mortar suitable for 3D printing. The formula has been modified based on existing literature to reduce its fluidity and improve its buildability. The mortar is prepared by mixing 1000 parts natural sand, 1000 parts cement, 1.3 parts HPMC, 6 parts nano-clay, 0.5 parts polycarboxylate superplasticizer, 0.7 parts sodium gluconate, and 300 parts water by mass ratio. The natural sand particle size ranges from 0.075mm to 4.75mm. The measured fluidity is 132mm, and the density in its fresh state is 2109 kg / m³. 3 .

[0068] The cement is commercially available ordinary Portland cement with a strength grade of 42.5 MPa and a particle size of 0–0.075 mm; the water is ordinary tap water; HPMC is hydroxypropyl methylcellulose ether, used as a thickener with an apparent viscosity of 40,000 mPa·s; nano clay is used as a thickener with a particle size of 0–0.045 mm; the polycarboxylate superplasticizer has a water reduction rate of 30% and a solid content of 25.2%; sodium gluconate is used as a concrete retarder.

[0069] Table 1 Evaluation of total resistance, material residue rate and extrusion effect of different extrusion heads for different materials

[0070]

[0071] As shown in Table 1, when the conventional extruder head (it should be noted that the conventional extruder head is a component of the 3D printer, and its structure and connection method are existing technologies, which will not be described in detail here) is replaced with the extruder head of the present invention, the total resistance for soil, cement-stabilized soil, and mortar is reduced by 86.8%, 89.9%, and 82.4%, respectively, and the extrusion force is reduced by 89.3%, 93.3%, and 97.3%, respectively, all of which are very significant. Among them, mortar has a relatively small total resistance due to its heavy weight, low viscosity, weak adhesion to the inner wall, and the lubricating effect of the water film. However, after being replaced with the extruder head of the present invention, the extrusion force is reduced to 0.75N, which can basically achieve automatic extrusion under its own weight.

[0072] Regarding material residue rates, when the conventional extruder head was replaced with the extruder head of this invention, the material residue rates for soil, cement-stabilized soil, and mortar were reduced by 89.6%, 89.4%, and 87.6%, respectively, demonstrating a significant effect on material residue removal. Observations show that highly viscous plastic materials were essentially removed under the scraping action of the steel wire, with the remaining residue consisting of a thin layer adhering to the surface of the conveyor belt.

[0073] Regarding extrusion performance, it is evident that replacing the conventional extrusion head with the extrusion head of this invention significantly improves printing quality, resulting in higher uniformity of the printed strip width and a closer approximation to the designed width. For soil, cement-stabilized soil, and mortar, the uniformity coefficient K of the extruded strip width is reduced by 67.0%, 68.9%, and 72.9%, respectively, demonstrating a significant improvement.

[0074] Based on this, the smooth conveyor belt of the present invention was replaced with a textured conveyor belt. The texture type is wavy stripes, the stripe width is 2mm, the stripes are concave inward, and distributed along the longitudinal direction of the conveyor belt. The stripes only exist in the middle of the conveyor belt, so the edges of the conveyor belt remain smooth surfaces to avoid the grooves from engaging with the steel wires and hindering the operation of the conveyor belt. Table 2 shows the results of the total resistance, material residue rate, and extrusion effect of the extruder head of the present invention after replacing the conveyor belt. It can be seen that when the smooth conveyor belt is replaced with a textured conveyor belt, the total resistance, extrusion force, and material residue rate of the extruder head of the present invention for soil, cement-stabilized soil, and mortar are slightly improved. Among them, the total resistance f increases by 7.9% to 15.8%, and the material residue rate R increases by 15.0% to 18.3%. However, the extrusion effect K remains basically unchanged. This is because the textured conveyor belt creates an additional mechanical interlocking force between the conveyor belt and the material, in addition to the adhesive force. This results in greater resistance when the steel wires separate the conveyor belt from the material. The remaining material, besides the portion adhering to the conveyor belt surface, also fills the grooves, leading to a higher residue rate (R). However, the advantage of textured conveyor belts is that they significantly enhance the adhesion between the material and the belt, making relative slippage less likely. This is particularly effective for materials with higher flowability and lower viscosity.

[0075] Table 2 Evaluation of total resistance, material residue rate and extrusion effect of textured conveyor belts for different materials

[0076]

[0077] The material transport channel 6 of the extruder head of this invention has the same dimensions as the channel formed by the four conveyor belts 2. This embodiment shows the case when the channel is square (40mm × 40mm). The technology disclosed in this invention can be applied to other situations, that is, the material transport channel 6 can be switched to a rectangle, parallelogram, triangle, polygon, etc. After changing the channel shape, the dimensions and positions of the support cylinder 1, conveyor belt 2, bracket 3, print head connector 4, roller shaft 5, material transport channel 6, screw hole 7, bracket reserved hole 8, roller array 9, wire positioning part 10, and wire 11 are redesigned according to the channel size. This is called a new low-resistance 3D printing end extruder head suitable for extruding high viscoplastic materials.

[0078] The material transfer channel 6 is aligned with the outlet of the 3D printing head. When their shapes and sizes are different, they need to be connected by the printing head connector 4. Through the lofting transformation of the two shapes, the outlet shape of the 3D printing head is smoothly transitioned to the channel shape of the extrusion head to achieve seamless material connection.

[0079] The cross-sectional dimensions of the material transport channel 6 of the extruder are generally 60mm at its thickest point and 20mm at its thinnest point, in order to avoid poor printing results caused by the channel being too thin or too thick.

[0080] The total length of the extruder head is adjustable, and can be adjusted by changing the circumference of the conveyor belt 2, the height of the bracket 3, and the height of the support cylinder 1. The longer the extruder head, the longer the material transport channel 6, and the more obvious the low-resistance extrusion advantage of this invention.

Claims

1. A concrete 3D printer end extruder, characterized in that, The concrete 3D printer end extrusion head includes a support cylinder (1) and a low-resistance transmission mechanism. The support cylinder (1) is a hollow cylindrical structure. The low-resistance transmission mechanism is arranged on the inner wall of the support cylinder (1) along the axial direction of the support cylinder (1). The low-resistance transmission mechanism forms a material transmission channel (6).

2. The concrete 3D printer end extruder according to claim 1, characterized in that, The inner wall of the support cylinder (1) has a polygonal cross-section, the number of sides of the polygon is M, and the number of low-resistance transmission mechanisms is N; when N≤M; when N<M, the low-resistance transmission mechanisms and the inner wall of the support cylinder (1) form a material transmission channel (6); when N=M, multiple low-resistance transmission mechanisms are joined together to form a material transmission channel (6).

3. The concrete 3D printer end extruder according to claim 2, characterized in that, The width of the low-resistance transmission mechanism is L1, the side length of the polygon is L2, and L1 = L2.

4. The concrete 3D printer end extruder according to claim 3, characterized in that, The concrete 3D printer end extrusion head also includes brackets (3) respectively set at the top and bottom of the support cylinder (1). The top and bottom of the support cylinder (1) are respectively provided with bracket reserved holes (8). The axial direction of the bracket reserved holes (8) is parallel to the axial direction of the support cylinder (1). The brackets (3) are set on the support cylinder (1) through the bracket reserved holes (8). The low resistance transmission mechanism is set on the bracket (3) at the top of the support cylinder (1) and on the bracket (3) at the bottom of the support cylinder (1).

5. The concrete 3D printer end extruder according to claim 4, characterized in that, The low-resistance transmission mechanism includes a conveyor belt (2), a first rolling shaft, and a second rolling shaft; the first rolling shaft is mounted on a bracket (3) at the top of the support cylinder (1); the second rolling shaft is mounted on a bracket (3) at the bottom of the support cylinder (1); the conveyor belt (2) is wound around the first rolling shaft and the second rolling shaft; the conveyor belt (2) passes through the first rolling shaft, the inner wall of the support cylinder (1), the second rolling shaft, and the outer wall of the support cylinder (1) in sequence and then returns to the first rolling shaft and repeats in this manner; when N < M, the conveyor belt (2) and the inner wall of the support cylinder (1) without the conveyor belt (2) form a material transmission channel (6); when N = M, multiple conveyor belts (2) are spliced ​​together end to end along the width of the conveyor belt (2) to form a material transmission channel (6).

6. The concrete 3D printer end extruder according to claim 5, characterized in that, The low-resistance transmission mechanism also includes a roller array (9) disposed on the inner wall of the support cylinder (1); the conveyor belt (2) passes through the first roller shaft, the roller array (9), the second roller shaft and the outer wall of the support cylinder (1) in sequence and returns to the first roller shaft and forms a cycle thereafter; the roller array (9) includes multiple parallel rollers; the axial direction of the rollers is perpendicular to the axial direction of the support cylinder (1).

7. The concrete 3D printer end extruder according to claim 6, characterized in that, The concrete 3D printer's end extrusion head also includes a material separation device disposed at the bottom end of the support cylinder (1); the material separation device includes a wire positioning component (10) and a wire (11); the wire positioning component (10) is in multiple sets; multiple sets of wire positioning components (10) are evenly distributed on the bracket (3) at the bottom end of the support cylinder (1); the wire (11) is suspended on two adjacent sets of wire positioning components (10) and is at the same height as the axis of the second rolling shaft; the wire (11) is close to the conveyor belt (2).

8. The concrete 3D printer end extruder according to claim 7, characterized in that, The concrete 3D printer's end extrusion head also includes a print head connector (4) located at the top of the support cylinder (1); the print head connector (4) is an integrally hollow frame structure; the hollow structure of the print head connector (4) matches the structure of the material transmission channel (6); the hollow structure of the print head connector (4) includes an extension section that extends toward and connects with the material transmission channel (6); the upper surface of the print head connector (4) is provided with screw holes (7).

9. A concrete 3D printer comprising a concrete 3D printer end extrusion head as described in any one of claims 1-8.

10. A concrete printing method based on the concrete 3D printer as described in claim 9, characterized in that, Includes the following steps: 1) The prepared material is put into the material hopper of the concrete 3D printer as described in claim 9 and stirred to obtain a uniformly stirred high-viscosity plastic material; 2) Move the extrusion head to make it directly contact the ground or printing platform, fix the conveyor belt (2) and start the extrusion program of the 3D printing head. The well-mixed high-viscosity plastic material is squeezed into the material transmission channel (6) formed by the low-resistance transmission mechanism through the print head connector (4) of the concrete 3D printer as described in claim 9. The high-viscosity plastic material is continuously extruded so that the high-viscosity plastic material fills the material transmission channel. 3) Raise the extruder head and continue extruding. At this time, the conveyor belt (2) rotates freely. Observe the characteristics of the extruded strip until the shape of the extruded strip is stable and can be continuously extruded. 4) Move the print head to the designated position and start the 3D printing process. The 3D print head will continuously feed the high-viscosity plastic material into the material transfer channel (6). 5) After the highly viscous plastic material gradually enters the material conveying channel (6), it comes into contact with the conveyor belt (2) and drives the conveyor belt (2) to move synchronously; 6) When the highly viscous plastic material moves to the second rolling shaft along the conveyor belt (2), it is cut by the steel wire (11) placed at the bottom end of the support cylinder (1) and closely attached to the conveyor belt (2). The highly viscous plastic material attached to the conveyor belt (2) is discharged through the bottom end of the support cylinder (1). 7) Repeat steps 5) and 6) until all high-viscosity plastic materials have been extruded.

Images