A device for 3d printing of steel fiber reinforced concrete with in-situ magnetically oriented steel fibers

Abstract

The application provides a 3D printing steel fiber concrete device for in-situ magnetization and orientation of steel fibers. The device comprises a three-dimensional movement module, a 3D printing concrete module installed on the three-dimensional movement module, and a magnetization and orientation module installed on the 3D printing concrete module; the three-dimensional movement module is used for moving the 3D printing concrete module; the 3D printing concrete module comprises a spray head; the magnetization and orientation module comprises a magnetic shielding disc for preventing leakage of a magnetic field generated by the magnetization and orientation module and a permanent magnet for generating a magnetic field inside the spray head, and the steel fibers in the steel fiber concrete material can be in-situ magnetized and oriented inside the spray head without affecting the orientation of the steel fibers in the printed concrete section. The application provides an excellent development space for 3D printing steel fiber concrete structure design and provides great help for improving the mechanical properties of 3D printing concrete in engineering practice.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of steel fiber reinforced concrete component preparation, and particularly relates to a 3D printing steel fiber reinforced concrete device for in-situ magnetized and oriented steel fibers. BACKGROUND

[0002] Plain concrete has been widely used in engineering field due to its strong load-bearing capacity, strong durability and strong plasticity. However, as a brittle material, the concrete has the defects of easy cracking and brittle failure. Although the introduction of steel fibers is proposed to strengthen the mechanical properties of the concrete in the current engineering, the orientation and distribution of the steel fibers in the concrete are difficult to control because the introduced steel fibers are usually steel wires with a length of 10mm-50mm and a diameter of 0.05mm-1mm. The randomness of the orientation and distribution of the steel fibers reduces the efficiency of the mechanical property enhancement. If the orientation of the steel fibers is perpendicular to the externally applied pressure, the steel fibers will interact with the matrix from the beginning of the micro-crack formation in the concrete. In this case, the steel fiber reinforced concrete as a whole is called a reinforcement system. Compared with the discontinuous steel fibers with random orientation and distribution, the steel fibers in the reinforcement system can greatly improve the mechanical properties and crack bridging capacity of the concrete, and further delay the occurrence of catastrophic failure. At present, the steel fibers in the oriented concrete are mainly oriented through special molding equipment, vibration compaction table, 3D printing and external magnetic field application. Compared with the external magnetic field orientation method, the former three methods have the defects of difficult orientation control, difficult orientation prediction and incomplete orientation. By utilizing the characteristics of the ferromagnetic material and the needle-bar structure of the steel fiber, the magnetization process of the fiber axis parallel to the magnetic induction direction can be completed by exposing the steel fiber to a magnetic field.

[0003] Currently, the magnetization and orientation technology of steel fibers is mainly applied in the process of mold casting concrete, which mainly uses large electromagnetic coils to generate a uniform magnetic field to magnetize and orient the steel fibers in the poured concrete. With the potential advantages of no formwork construction, high automation and high degree of freedom in construction, 3D printing concrete based on extrusion has gradually become an important development direction of the future construction industry. During the printing process, the orientation of steel fibers needs to be precisely controlled to improve the efficiency of steel fibers and the mechanical properties of 3D printing concrete building components. Considering the large and complex construction scene of 3D printing concrete and the difficulty of obtaining a large-scale strong magnetic field, although the existing steel fiber magnetization and orientation equipment for concrete can effectively complete the precise orientation of steel fibers, the magnetization system is complex, occupies a large area, and can only realize the magnetization of limited size and shape of the components, which is difficult to realize the magnetization and orientation of steel fibers in large 3D printing concrete components. In addition, compared with mold casting concrete, 3D printing concrete has higher early strength and lower fluidity due to higher constructability requirements, which means that magnetizing the fiber concrete components after 3D printing can easily cause incomplete orientation of steel fibers and may cause the generation of micro-cracks in the components, resulting in the deterioration of the mechanical properties of the concrete components. At the same time, during the magnetization process, the entire magnetization system needs to be kept in operation for a long time to maintain a uniform magnetic field, which can easily cause unnecessary energy waste. In addition, a large-scale strong magnetic field may not be compatible with other magnetic facilities on site, which not only cannot guarantee the expected steel fiber magnetization and orientation effect and thus leads to task failure, but also can endanger the safety of on-site construction personnel. SUMMARY

[0004] To solve the problems in the prior art, the present application provides a 3D printing steel fiber concrete device for in-situ magnetization and orientation of steel fibers.

[0005] The present application is realized by the following technical solutions:

[0006] A 3D printing steel fiber concrete device for in-situ magnetization and orientation of steel fibers, comprising a three-dimensional motion module, a 3D printing concrete module is installed on the three-dimensional motion module, and the three-dimensional motion module is used to move the 3D printing concrete module to a predetermined position; the 3D printing concrete module comprises a nozzle installed vertically downward, the magnetization and orientation module comprises a magnetic shielding disc installed at the lower end of the nozzle and a permanent magnet installed in the magnetic shielding disc, the magnetic shielding disc comprises a disc bottom plate and a disc side wall, and the plane of the disc bottom plate is perpendicular to the axis of the nozzle; the permanent magnets are arranged in pairs on both sides of the nozzle to generate a magnetic field with a single direction inside the nozzle, and the magnetic shielding disc is used to prevent the magnetic field generated by the permanent magnets from leaking to the lower side of the nozzle.

[0007] Further, the 3D printing concrete module further comprises a stepping motor, a motor support seat, a rigid coupling, a hopper, a spiral extrusion rod and a barrel wall scraping rod, the hopper is used for containing steel fiber concrete material, the stepping motor is installed above the hopper through the motor support seat, the output shaft of the stepping motor is connected with the spiral extrusion rod through the rigid coupling vertically downward, the spiral extrusion rod is vertically located in the hopper, the hopper side is obliquely upward to form a feeding port, the lower end of the hopper is gradually tapered to form a hopper outlet, and the nozzle is threadedly connected at the hopper outlet; the barrel wall scraping rod is welded on the spiral extrusion rod and used for scraping the concrete accumulated on the barrel wall in the 3D printing process.

[0008] Further, the magnetic shielding disc is provided with a center hole in a disc bottom plate, the nozzle is discharged downward through the hole of the disc bottom plate, a disc side wall of the magnetic shielding disc is surrounded around the edge of the disc bottom plate, and the disc side wall is higher than the top end of the permanent magnet.

[0009] Further, the permanent magnet is provided with two circular plates, and the magnetic poles of the permanent magnet are located at the two end faces of the circular plates; the two permanent magnets are arranged on the two sides of the nozzle, and the opposite poles are arranged oppositely, so that a magnetic field perpendicular to the axis direction of the nozzle is generated in the nozzle.

[0010] Compared with the prior art, the present application has the following beneficial effects:

[0011] (1) The present application integrates the magnetization module on the 3D printing concrete nozzle, discards the mode of using a large electromagnetic coil to magnetize the steel fibers in the concrete, realizes in-situ magnetization and orientation, and avoids the internal micro-cracks and mechanical property deterioration of the concrete caused by post-magnetization.

[0012] (2) The present application realizes the magnetization and orientation of the steel fibers in the concrete by means of the permanent magnet, solves the problems of uneven condensation and energy loss in the concrete caused by coil heating, improves the mechanical reliability of the component, and realizes energy saving.

[0013] (3) The magnetization and orientation module of the present application can magnetize the steel fibers in the concrete in-situ, which helps to avoid the crossing and even winding of the steel fibers in the nozzle, and further forms an overlapping mesh distribution to cause printing failure. This in-situ magnetization method provides the possibility of using the longest fibers in the small nozzle.

[0014] (4) The in-situ magnetization and orientation of the steel fibers in the 3D printing steel fiber concrete process helps to solve the problems of anchoring structure deterioration and limitation of the freedom degree of concrete shape construction caused by the introduction of steel bars to strengthen the mechanical properties of the concrete component in traditional construction.

[0015] (5) The application has good expansibility, can realize quick disassembly and quick replacement of magnetized components, is convenient for in-situ magnetization and orientation of different types of steel fibers in different viscosity 3D printing concrete, and has good application scenarios in optimization of fiber use efficiency and mechanical property regulation of 3D printing steel fiber concrete.

[0016] In summary, the application has great application potential in realizing diversified structure design and high reliability mechanical properties of components in the construction process. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a device overall structure diagram of an embodiment of the application;

[0018] Figure 2 is a structure diagram of a three-dimensional motion module of an embodiment of the application;

[0019] Figure 3 is a structure diagram of a 3D printing concrete module and a magnetization orientation module of an embodiment of the application;

[0020] Figure 4 is a sectional view of a 3D printing concrete module and a magnetization orientation module of an embodiment of the application;

[0021] Figure 5 is an exploded view of a 3D printing concrete module and a magnetization orientation module of an embodiment of the application. DETAILED DESCRIPTION

[0022] The application will be further described and illustrated in conjunction with the specific embodiments. The embodiments are only exemplary and do not define the limit range. The technical features of each embodiment in the application can be combined correspondingly without conflict.

[0023] The overall diagram of the 3D printing steel fiber concrete device for in-situ magnetization and orientation of steel fibers designed in the application is shown in Figure 1 The device mainly includes an aluminum alloy frame 1, a three-dimensional motion module 2, a fixed mounting plate 3, a 3D printing concrete module 4, a connecting ring 5, a magnetization orientation module 6, a printed concrete 7, and a printing plane 8.

[0024] Three-dimensional motion module 2 is directly connected to aluminum alloy frame 1 by screws, 3D printing concrete module 4 is connected to three-dimensional motion module 2 by means of bolt-nut through the through hole on the fixed mounting plate 3, magnetized orientation module 6 is connected to 3D printing concrete module 4 by smearing welding glue on the two connecting surfaces of connecting ring 5, printing plane 8 is arranged below 3D printing concrete module 4, and printed concrete 7 is printed on printing plane 8. The aluminum alloy frame 1 is used for reducing module deviation and printing error caused by environmental vibration and electromagnetic interference, and effectively ensures the rigidity of the in-situ magnetized orientation steel fiber 3D printing steel fiber concrete device.

[0025] The three-dimensional motion module 2, the 3D printing concrete module 4 and the magnetized orientation module 6 of the device will be described in detail below.

[0026] The structural diagram of the designed three-dimensional motion module 2 is shown in Figure 2 It mainly includes X-axis module 201, Y-axis module 202, Z-axis module 203 and limit switch 204. The three-dimensional motion module is an XYZ three-axis linear motion module, which is mainly used for controlling the moving speed of the in-situ magnetized orientation nozzle on the XYZ three-axis. The two linear slides of X-axis module 201 are fixed on aluminum alloy frame 1 by screws; the two linear slides of Z-axis module 203 are fixed on the sliders of the two X-axis modules respectively; the linear slide of Y-axis module 202 is fixed on the sliders of the two Z-axis modules respectively. The 3D printing concrete module 4 is fixed on the slider of Y-axis module 202. The movement of 3D printing concrete module 4 on the XYZ three-axis relies on the corresponding step-by-step drive motors of the three modules. Limit switch 204 (not shown) is installed on both sides of the slide rails of each X-axis module 201, Y-axis module 202 and Z-axis module 203. When the slider moves to the limit position, limit switch 204 sends a signal to the linear module controller, and the corresponding step-by-step drive motor is stopped by the controller.

[0027] The structural diagram of the designed 3D printing concrete module 4 and magnetized orientation module 6 is shown in Figure 3 The sectional view is shown in Figure 4 The exploded view is shown in Figure 5The 3D printing concrete module 4 mainly includes a stepping motor 401, a motor support seat 402, a rigid coupling 403, a hopper 404, a feeding port 405, a spiral extrusion rod 406, a barrel wall scraping rod 407, and a nozzle 408. The magnetization orientation module 6 mainly includes a magnetic shielding disc 601, a permanent magnet 602, a magnetic induction intensity control gasket 603, and a permanent magnet mounting clamp 604. The 3D printing concrete module is mainly responsible for controlling the rotation speed of the spiral extrusion rod, thereby controlling the extrusion speed of the 3D printing nozzle. The magnetization orientation module is mainly responsible for completing the magnetization orientation of the steel fibers inside the 3D printing nozzle, while preventing the influence of the magnetic field of the permanent magnet on the fiber orientation inside the printed concrete section.

[0028] The stepping motor 401 is connected to the motor support seat 402 through a threaded connection, and the output shaft thereof is vertically downward through the fixed mounting plate 3 and connected to the spiral extrusion rod 406 through the rigid coupling 403. The motor support seat 402, the fixed mounting plate 3, and the hopper 404 are connected through bolts and nuts. The hopper 404 is a cylinder with different diameters, and the side of the hopper is obliquely upward to form the feeding port 405, and the lower end is gradually contracted to form a hopper outlet. The spiral extrusion rod 406 is vertically downward installed in the hopper 404, and the barrel wall scraping rod 407 is connected to the spiral extrusion rod 406 by welding to scrape the concrete accumulated on the barrel wall during the 3D printing process. The nozzle 408 is installed at the hopper outlet through internal and external thread connection.

[0029] The magnetic shielding disc 601 includes a disc bottom plate and a disc side wall. The disc bottom plate has an opening, and the disc bottom plate is glued to the outer wall of the nozzle 408 through a connecting ring 5, and the disc bottom plate of the magnetic shielding disc 601 is ensured to be perpendicular to the axis of the nozzle 408. The opening on the disc bottom plate is slightly larger than the size of the lower end of the nozzle 408, so that the disc bottom plate is sleeved on the nozzle, and the lower surface of the disc bottom plate is 5 mm away from the lower end of the nozzle. The disc side wall of the magnetic shielding disc 601 is higher than the top end of the permanent magnet; the permanent magnet 602 is installed in the magnetic shielding disc 601, and the magnetic poles thereof are located on the two end faces. The opposite poles of the two permanent magnets are arranged on the two sides of the nozzle 408, so that the material inside the nozzle 408 is in a stable magnetic field perpendicular to the axis of the nozzle, thereby magnetizing the steel fibers in the material, and the orientation of the steel fibers is distributed along the magnetic induction lines. The distance between the permanent magnets 602 is changed by changing the number or thickness of the magnetic induction intensity control gasket 603, thereby changing the magnetic induction intensity of the magnetic field inside the nozzle 408. The permanent magnet mounting clamp 604 is tightly attached to the top end of the permanent magnet 602 and the magnetic induction intensity control gasket 603, and is connected to the disc bottom plate of the magnetic shielding disc 601 through non-magnetic bolts and nuts.

[0030] The printing material of the device is premixed steel fiber concrete material, which is prepared by mixing concrete and steel fibers, wherein the steel fibers are arc-shaped double-hook steel fibers with a length of 10-50 mm. According to the type of steel fibers in the material and the viscosity of the concrete, magnetic induction intensity control pads 603 of different numbers or thicknesses are selected. The steel fiber concrete material is filled from the feeding port 405, the stepping motor is started, and the spiral extrusion rod 406 is rotated under the driving of the stepping motor 401, the rotation speed of which is controlled by inputting signals from the control system to the stepping motor 401, and then the steel fiber concrete material is extruded into the outlet below the hopper 404. The whole hopper 404 is made of non-magnetic material (304 stainless steel) and will not affect the magnetic field line distribution of the permanent magnet. Due to the action of the magnetic field of the permanent magnet, the steel fibers are oriented along the magnetic field lines of the permanent magnet during the 3D printing process. With the rotation of the spiral extrusion rod 406, the concrete mixed with the magnetized and oriented steel fibers is extruded from the nozzle 408. The extruded steel fiber concrete forms a printing filament with the movement of the 3D printed concrete module 4. Since the magnetic shielding disc 601 is made of DT4 electrical pure iron, the magnetic field below it can be ignored, so it will not affect the orientation of the steel fibers in the printed concrete section.

[0031] Through the above device, the in-situ magnetization and orientation of steel fibers can be realized while printing structural components in bridges, tunnels, roads and other major infrastructure projects, which helps to improve the use efficiency of steel fibers and the mechanical strength of concrete components. At the same time, through the above device, the aging concrete structure can also be repaired, such as the reinforcement of bridges and buildings, to improve the structural integrity and prolong the service life. In addition, in earthquake-prone or storm-affected areas, the above device can be used to construct more solid disaster-prevention buildings, such as earthquake-resistant walls and flood-resistant dams. In addition, the accuracy of 3D printing technology and the structural strength of in-situ magnetized and oriented steel fiber concrete can help create unique artistic decorations and complex design elements.

[0032] The present application realizes the in-situ magnetization and orientation of different types of steel fibers in the process of 3D printing different viscosity concrete by arranging permanent magnets at the 3D printing concrete nozzle, which meets the demand of improving the mechanical properties of 3D printed concrete components and the use efficiency of steel fibers. The present application realizes the integrated design of the magnetization module and the printing module by preventing the magnetic field of the permanent magnet from changing the fiber orientation in the printed concrete section through the magnetic shielding disc. In addition, the in-situ magnetization method of the permanent magnet used in the present application does not require external energy input, which greatly reduces the complexity of the magnetization module, solves the problem of uneven condensation in the concrete caused by heating of the magnetization module, and reduces unnecessary energy consumption. At the same time, the present application provides an excellent development space for the design of 3D printed steel fiber concrete structure, which provides great help for improving the mechanical properties of 3D printed concrete in engineering practice.

[0033] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it cannot be understood as a limitation to the patent scope of the present application. For ordinary skilled in the art, several modifications and improvements can be made without departing from the concept of the present application, which shall all fall into the protection scope of the present application.

Claims

1. A 3D-printed steel fiber reinforced concrete device for in-situ magnetized oriented steel fibers, characterized in that, The system includes a three-dimensional motion module on which a 3D-printed concrete module is mounted. The three-dimensional motion module is used to move the 3D-printed concrete module to a preset position. The 3D-printed concrete module includes a vertically downward-mounted nozzle, on which a magnetized orientation module is mounted. The magnetized orientation module includes a magnetic shielding disk mounted at the lower end of the nozzle and permanent magnets mounted inside the magnetic shielding disk. The magnetic shielding disk includes a base plate and side walls. The plane of the base plate is perpendicular to the nozzle axis. The base plate has a central hole through which the nozzle discharges material downwards. The side walls of the magnetic shielding disk surround the edge of the base plate, and the upper edge of the side walls is higher than the top of the permanent magnets. The permanent magnets are arranged in pairs on both sides of the nozzle to generate a unidirectional magnetic field inside the nozzle. The magnetic shielding disk is used to prevent the magnetic field generated by the permanent magnets from leaking below the nozzle. The 3D printing concrete module also includes a stepper motor, a motor support, a rigid coupling, a hopper, a spiral extruder, and a cylinder wall scraper. The hopper is used to hold steel fiber reinforced concrete material. The stepper motor is mounted above the hopper via the motor support, and its output shaft is vertically downward and connected to the spiral extruder via a rigid coupling. The spiral extruder is vertically located inside the hopper. The side of the hopper opens obliquely upward to form a feed inlet, and the lower end of the hopper gradually narrows to form a hopper outlet. The nozzle is threadedly connected to the hopper outlet. The cylinder wall scraper is welded to the spiral extruder and is used to scrape off the concrete accumulated on the cylinder wall during the 3D printing process. The magnetization orientation module also includes a magnetic induction intensity control pad and a permanent magnet mounting fixture. The magnetic induction intensity control pad is placed between the permanent magnet and the nozzle to adjust the distance between the permanent magnets, thereby adjusting the magnetic induction intensity used for magnetizing the orientation steel fibers. The permanent magnet mounting fixture is used to fix the permanent magnet and the magnetic induction intensity control pad inside the magnetic shielding disk.

2. The 3D printing steel fiber reinforced concrete device for in-situ magnetized oriented steel fibers according to claim 1, characterized in that, The three-dimensional motion module includes an X-axis module, a Y-axis module, a Z-axis module, and limit switches. The X-axis module, Y-axis module, and Z-axis module are used to control the movement of the 3D printed concrete module in the X-axis, Y-axis, and Z-axis directions, respectively. Multiple limit switches are provided and are installed at both ends of the X-axis module, Y-axis module, and Z-axis module.

3. The 3D printing steel fiber concrete device for in-situ magnetized oriented steel fibers according to claim 1, characterized in that, The hopper is made of 304 stainless steel.

4. The 3D printing steel fiber concrete device for in-situ magnetized oriented steel fibers according to claim 1, characterized in that, The device also includes a connecting ring disposed between the hole in the magnetic shielding disk and the nozzle, for connecting the nozzle and the magnetic shielding disk.

5. The 3D printing steel fiber concrete device for in-situ magnetized oriented steel fibers according to claim 1, characterized in that, The device has two permanent magnets, both of which are circular discs, with the magnetic poles of the permanent magnets located on both ends of the discs. The two permanent magnets are respectively located on both sides of the nozzle, with opposite magnetic poles facing each other, so that a magnetic field perpendicular to the nozzle axis is generated inside the nozzle.

6. The 3D printing steel fiber concrete device for in-situ magnetized oriented steel fibers according to claim 1, characterized in that, The magnetic shielding disk is made of DT4 electrical pure iron.

7. The 3D printing steel fiber concrete device for in-situ magnetized oriented steel fibers according to claim 1, characterized in that, The device also includes an aluminum alloy frame to enhance the overall stability of the device, and the three-dimensional motion module is connected to the aluminum alloy frame by screws.

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