Extrusion 3D Printing Robot for Repairing Early Cracks and Minor Potholes in Asphalt Pavements

Abstract

This invention provides a design concept for an extrusion-type 3D printing robot for repairing early-stage cracks and minor potholes in asphalt pavements. It proposes a highly automated, high-precision, and controllable repair solution that can be widely applied to the repair and maintenance of damaged asphalt. It overcomes the limitations of existing gantry-type three-axis 3D printing robots in in-situ repair and maintenance of early-stage cracks and minor potholes in asphalt pavements, which lack mobility and flexibility and are restricted by the size of the three axes. Compared to traditional molten asphalt, the solid asphalt particles used in this device have lower requirements for storage and transportation conditions, melting immediately upon use, reducing aging during asphalt storage and transportation, and ensuring the quality of the asphalt material. The device treats the flue gas generated from asphalt heating through a waste gas purification component mainly composed of a plate absorption tower and an activated carbon box, reducing its impact on the environment and the health of construction workers.

Description

Technical Field

[0001] This invention relates to the field of road maintenance technology, and in particular to an extrusion-type 3D printing robot for repairing early cracks and minor potholes in asphalt pavements. Background Technology

[0002] Asphalt pavement performance degrades under vehicle loads and water temperature cycles, leading to pavement defects such as cracks and potholes. These defects not only severely impact road performance but also, if not repaired promptly, rapidly progress under load, further complicating maintenance. With the rapid development of highway transportation and the increase in the number of motor vehicles in my country, highway maintenance tasks are becoming increasingly heavy. Common methods for treating asphalt pavement cracks include joint sealing, crack filling, and strip patching. Pothole repair is mainly accomplished through milling, cleaning, filling, and compaction. These traditional methods are labor-intensive, requiring workers to perform long hours of on-site work at scattered maintenance locations. This is not only constrained by the environment, but also poses significant safety risks to workers, as pavement defects often occur in areas with heavy traffic. Traditional pavement maintenance measures are prone to material waste and inadequate filling, leading to increased costs and incomplete repairs. Considering the cost-effectiveness of manpower and equipment investment in maintenance projects, repairs are often only carried out in the middle to late stages of asphalt pavement cracks and potholes, making it difficult to achieve preventative maintenance that addresses problems early and in their initial stages. Currently, there is a lack of a highly automated, high-precision, and controllable repair solution that can be widely applied to the repair of early-stage cracks and minor potholes in asphalt pavements.

[0003] 3D printing technology is a rapid prototyping technology that builds spatial entities by creating digital spatial models and using various materials in fluid, powder, filament, or sheet states through a layer-by-layer printing process. It differs from subtractive manufacturing, which involves shearing, planing, and grinding raw materials. Its focus is on the layer-by-layer stacking of materials along the forming direction. According to ISO / ASTM 52900-2015, more than 50 commonly used 3D printing technologies are divided into seven categories: binder jetting, directional energy deposition, material extrusion, photopolymerization, powder bed fusion, and sheet lamination. Material extrusion technology involves extruding plastic materials as filaments onto a printing platform, where they solidify layer by layer to form the component. It is low-cost and offers a wide variety of materials. Besides common thermoplastic materials such as ABS, PLA, and TPU, this technology has also achieved good results in printing cement mortar, liquid metal, ceramics, and pharmaceuticals. Asphalt is a viscoelastic-plastic material whose rheological properties change with temperature. As temperature rises, asphalt gradually transforms from a solid state to a viscous flow state, and may even exhibit a Newtonian fluid state; conversely, its state is reversible. Due to its ability to be extruded layer by layer, asphalt can be used as a 3D printing material.

[0004] Applying 3D printing technology to the repair of early-stage cracks and minor potholes in asphalt pavements can improve the automation level of the project, reduce reliance on manual labor, increase construction safety, and reduce environmental constraints. By inserting the 3D printing head deep into the damaged area of ​​the asphalt pavement and filling it layer by layer from bottom to top, asphalt can be completely filled into the damaged area, resulting in good repair effects and high material utilization. It can effectively reduce labor costs and the transportation and use of traditional equipment, and can be widely used in preventive maintenance projects to specifically repair cracks and minor potholes in asphalt pavements, slow down the process of road damage, maintain or improve pavement function, and extend the service life of roads. Therefore, 3D printing technology based on asphalt materials has broad application prospects in the repair and maintenance of early-stage cracks and minor potholes in asphalt pavements.

[0005] Currently, the equipment used for 3D printing of asphalt materials is mainly gantry-type three-axis robots used in laboratories. These devices have poor mobility and flexibility, and the printing range is limited by the three-axis dimensions, making them unsuitable for on-site repair of early cracks and minor potholes in asphalt pavements. Their hoppers mainly store molten asphalt, which requires stringent storage conditions. This not only exacerbates asphalt aging and affects asphalt quality, but also consumes a large amount of energy to heat and maintain the molten asphalt. In addition, due to the lack of asphalt exhaust gas treatment components, existing equipment cannot treat the toxic and harmful fumes generated during the asphalt heating process, which may pose a threat to the health of users and the environment. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the technical problem this invention aims to solve is to propose an extrusion-type 3D printing robot for repairing early cracks and minor potholes in asphalt pavements.

[0007] The technical solution adopted by the present invention to solve the aforementioned technical problem is as follows:

[0008] A 3D printing extrusion robot for repairing early cracks and minor potholes in asphalt pavement includes a tracked chassis and a robotic arm. The robot further comprises a road condition detection component, a material discharge component, an exhaust gas purification component, and a control system. The tracked chassis carries the hardware components and allows for flexible movement during the maintenance of early cracks and minor potholes in asphalt pavement. The road condition detection component collects information on early cracks and minor potholes in asphalt pavement to provide a basis for establishing a 3D digital model. The material discharge component heats and stores solid asphalt particles and precisely extrudes them according to the 3D printing path and required quantity. The exhaust gas purification component purifies the fumes generated during asphalt heating. The control system ensures the coordinated operation of all robot components during the 3D printing maintenance and repair of early cracks and minor potholes in asphalt pavement.

[0009] The tracked vehicle chassis is a lithium battery tracked vehicle, used to carry hardware devices such as a robotic arm, road condition detection components, material discharge components, exhaust gas purification components, and control system. The first motor of the robotic arm is located on the top of the tracked vehicle chassis, controlling the robotic arm chassis to rotate 180 degrees in the horizontal direction. The second motor is located on the upper part of the robotic arm chassis, controlling the robotic arm's upper arm to rotate 90 degrees in the vertical direction. The third motor is located at the end of the robotic arm's upper arm, controlling the robotic arm's lower arm to rotate 180 degrees in the vertical direction.

[0010] The road condition detection component includes three 3D laser scanners located at different positions, which can perform 3D laser scanning at different angles and cooperate with the control system to construct 3D digital models of early cracks and minor potholes in asphalt pavement.

[0011] The discharge assembly includes a hopper, a solid-state pump, a feed pipe, a telescopic section of the feed pipe, a cylinder, a No. 4 motor, an auger, a heating element, a switching valve, an extrusion port, and a temperature sensor. The solid-state pump on the side of the hopper is connected to the feed inlet at the top of the cylinder via the feed pipe. The cylinder is fixed to the end of the robotic arm's forearm via a bracket on the long end of a right-angle steel plate. The bracket has two semi-circular rings bolted together. The No. 4 motor is mounted on the top of the short end of the right-angle steel plate. The output shaft of the No. 4 motor penetrates the top of the cylinder and extends into the cylinder. The auger is fixed to the end of the No. 4 motor's output shaft. The heating element is mounted on the inner wall of the cylinder. The temperature sensor is located at the end of the extrusion port.

[0012] The exhaust gas purification assembly includes a purification connecting pipe, an exhaust pipe, an exhaust pipe extension section, a plate absorption tower, and an activated carbon box; the exhaust port at the top of the material cylinder is connected to the exhaust port at the bottom of the plate absorption tower through the exhaust pipe, and the exhaust port at the top of the plate absorption tower is connected to the input end at the bottom of the activated carbon box through the purification connecting pipe.

[0013] After the road condition detection component constructs a 3D digital model of the damaged asphalt pavement, the control system imports it into the 3D printing slicing software. Based on the slicing and path planning results, the system controls the movement of the robotic arm, activates the heating element on the inner wall of the material cylinder, controls the solid pump to pump solid asphalt particles into the material cylinder, opens the switch valve, and as the No. 4 motor drives the auger to rotate, molten asphalt is extruded from the extrusion port.

[0014] The robot has a screw-type extrusion port and is equipped with discharge pipes of different specifications. The extrusion head of the discharge pipe includes a round head, a square head, or a flat head.

[0015] The material conveying pipe is adjacent to a portion of the material cylinder, which is a material conveying pipe extension section, and the exhaust pipe is adjacent to a portion of the material cylinder, which is an exhaust pipe extension section.

[0016] The electricity used by the robot is sourced from the lithium battery carried on the crawler vehicle. Solar panels are installed on the storage bin on top of the crawler vehicle, the plate-type absorption tower, and the upper part of the activated carbon box, which can convert solar energy into electricity to charge the lithium battery.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] The present invention provides a design concept for an extrusion-type 3D printing robot for repairing early cracks and minor potholes on asphalt pavements, and proposes a highly automated, high-precision, and strongly controllable repair solution that can be widely applied to the repair and maintenance of damaged asphalt pavements; it overcomes the problems of lack of mobility, flexibility, and being restricted by the three-axis size in the in-situ repair and maintenance projects of early cracks and minor potholes on asphalt pavements by the existing gantry-type three-axis 3D printing robot; compared with traditional molten asphalt, the solid asphalt particles used in this device have lower requirements for storage and transportation conditions, that is, they are melted immediately when used, reducing the aging phenomenon during the storage and transportation of asphalt and ensuring the quality of asphalt materials; this device processes the flue gas generated by heating asphalt through an exhaust gas purification component mainly composed of a plate-type absorption tower and an activated carbon box, reducing its impact on the environment and the life and health of construction workers. Brief Description of the Drawings

[0019] Figure 1 It is a schematic diagram of the overall structure of the present invention from the left side view of the robot;

[0020] Figure 2 It is a schematic diagram of the overall structure of the present invention from the right side view of the robot;

[0021] Figure 3 It is a schematic diagram of the overall structure of the present invention from the top view of the robot;

[0022] Figure 4 It is a schematic diagram of the barrel and material extrusion structure of the present invention;

[0023] Figure 5 It is a schematic diagram of the structures of different models of discharge pipes provided in a supporting manner for the present invention;

[0024] In the figure, 1 is a 3D laser scanner; 2 is a storage bin; 3 is a solid-state pump; 4 is a feed pipe; 5 is a telescopic section of the feed pipe; 6 is a barrel; 7 is a No. 4 motor; 8 is a spiral conveyor; 9 is a heating element; 10 is a switching valve; 11 is an extrusion outlet; 12 is a temperature sensor; 13 is a right-angle steel plate; 14 is a bracket; 15 is a bolt; 16 is a purification connection pipe; 17 is an exhaust pipe; 18 is a telescopic section of the exhaust pipe; 19 is a plate-type absorption tower; 20 is an activated carbon box; 21 is a No. Ⅰ motor; 22 is a robotic arm chassis; 23 is a No. Ⅱ motor; 24 is a large robotic arm; 25 is a No. Ⅲ motor; 26 is a small robotic arm; 27 is a discharge pipe; 28 is a solar panel; 29 is a crawler vehicle chassis. Detailed Embodiments

[0025] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments, but it is not intended to limit the scope of protection of this application.

[0026] This invention relates to an extrusion-type 3D printing robot for repairing early-stage cracks and minor potholes in asphalt pavements (hereinafter referred to as the robot, see below). Figure 1-5 ), including tracked chassis 29, robotic arm, road condition detection components, material discharge components, exhaust gas purification components and control system;

[0027] The tracked vehicle chassis 29 is a lithium battery tracked vehicle used to carry hardware devices such as a robotic arm, road condition detection components, material discharge components, exhaust gas purification components, and control system. The first motor 21 of the robotic arm is located on the top of the tracked vehicle chassis 29 and controls the robotic arm chassis 22 to rotate within a 180-degree range in the horizontal direction. The second motor 23 is located on the upper part of the robotic arm chassis 22 and controls the robotic arm upper arm 24 to rotate within a 90-degree range in the vertical direction. The third motor 25 is located at the end of the robotic arm upper arm 24 and controls the robotic arm lower arm 26 to rotate within a 180-degree range in the vertical direction.

[0028] The road condition detection component includes three 3D laser scanners 1 located at different positions, which can perform 3D laser scanning at different angles to obtain the elevation information of each point at the early cracks and minor potholes of the asphalt pavement. These points collectively represent the shape of the damaged surface. By connecting these points to each other, tens of thousands of triangular surfaces are generated, which can construct a highly accurate 3D digital model. After the model is transmitted to the 3D printing slicing software, slicing and path planning will be performed automatically. The robotic arm moves according to the path planning results under the action of the control system.

[0029] The discharge assembly includes a hopper 2, a solid pump 3, a conveying pipe 4, a conveying pipe extension section 5, a material cylinder 6, a No. 4 motor 7, an auger 8, a heating element 9, a switching valve 10, an extrusion port 11, and a temperature sensor 12.

[0030] The hopper 2 is installed on the top of the tracked vehicle chassis 29, away from the road condition detection component, and is used to store solid asphalt particles. The input end of the solid pump 3 is connected to the outlet on the side of the hopper 2, and the output end of the solid pump 3 is connected to the feed inlet at the upper end of the cylinder 6 through the conveying pipe 4. The cylinder 6 is fixed to the end of the robotic arm forearm 26 by a bracket 14 on the long end of the right-angle steel plate 13. The ring of the bracket 14 consists of two semi-circular rings fixedly connected by bolts 15. A switch valve 10 is installed at the extrusion port 11 of the cylinder 6 to control the opening and closing of the extrusion port 11. The extrusion port 11 has external threads to facilitate the installation of the discharge pipe 27. Disassembly; Motor 7 is mounted on the top of the short end of the right-angle steel plate 13. The output shaft of Motor 7 penetrates the top of the material cylinder 6 and extends into the material cylinder 6. The auger 8 is fixed to the end of the output shaft of Motor 7 and is used to stir, transport and extrude asphalt. The extrusion speed of asphalt at the extrusion port 11 can be changed by controlling the rotation speed of Motor 7; Heating plate 9 is installed on the inner wall of the material cylinder 6 and is used to heat the molten asphalt particles; Temperature sensor 12 is located at the end of the extrusion port 11 and is used to detect the liquid level during asphalt material spraying 3D printing repair and maintenance of cracks with small surface crack area but large deep crack area.

[0031] The exhaust gas purification assembly is installed on the top of the tracked vehicle chassis 29 near the road condition detection assembly. It includes a purification connecting pipe 16, an exhaust pipe 17, an exhaust pipe extension section 18, a plate absorption tower 19, and an activated carbon box 20. The air inlet at the bottom of the plate absorption tower 19 is connected to the air outlet at the top of the material cylinder 6 via the exhaust pipe 17, and the air outlet at the top of the plate absorption tower 19 is connected to the input end at the bottom of the activated carbon box 20 via the purification connecting pipe 16. Asphalt fumes generated by the melting of asphalt particles are irritating to the skin and mucous membranes, have phototoxic effects, and may even be carcinogenic. Therefore, asphalt fumes need to be purified. The main task of asphalt fumes treatment is to reduce the emission of fine tar particles. Common methods include washing, adsorption, filtration, combustion, condensation, and mechanical separation, often using a combination of several methods. In this application, the amount of asphalt fumes generated is limited. Considering cost and portability, a treatment method combining washing and adsorption is adopted, suitable for treating small amounts of fumes. This method has advantages such as low cost, simple structure, and good purification effect. The plate absorption tower 19 is filled with water. Asphalt fumes enter the plate absorption tower 19 through the exhaust pipe 17. The fine tar particles in the asphalt fumes are absorbed by the water and float to the surface. The waste liquid is discharged from the drain port at the bottom of the plate absorption tower 19. The gas passing through the plate absorption tower 19 then enters the activated carbon box 20 for secondary adsorption. Finally, it is discharged into the atmosphere from the exhaust port of the activated carbon box 20, which can play a role in detoxification and deodorization. The plate absorption tower 19 is a prior art technology. Its size can be customized according to actual needs. The length and width of the plate absorption tower 19 are both 0.5m, and its height is 0.3m.

[0032] After the road condition detection component constructs a 3D digital model, the control system imports it into the 3D printing slicing software. Based on the slicing and path planning results, it controls the movement of the robotic arm, simultaneously turns on the heating element 9 on the inner wall of the material cylinder 6, opens the switch valve 10, and controls the solid pump 3 to pump solid asphalt particles into the material cylinder 6. As the fourth motor 7 drives the auger 8 to rotate, molten asphalt is extruded through the extrusion port 11, precisely filling early cracks and minor potholes in the asphalt pavement.

[0033] The robot is equipped with discharge pipes 27 of different specifications. The extrusion heads of the discharge pipes 27 have different shapes, including round heads, square heads and flat heads, which are suitable for different cracks and pits.

[0034] The portion of the conveying pipe 4 adjacent to the material cylinder 6 is a conveying pipe telescopic section 5. The conveying pipe telescopic section 5 has a telescopic function, ensuring that the material cylinder 6 can move to an area far away from the tracked vehicle while the conveying pipe 4 can still meet the usage requirements. Similarly, the exhaust pipe 17 is provided with an exhaust pipe telescopic section 18.

[0035] The robot is powered by lithium batteries mounted on the tracked vehicle. Solar panels 28 are installed on the top of the hopper 2, plate absorption tower 19, and activated carbon box 20 on the tracked vehicle chassis 29 to convert solar energy into electrical energy to charge the lithium batteries.

[0036] This robot primarily performs in-situ repair of early-stage cracks and minor potholes in asphalt pavements using material extrusion 3D printing. For potholes and open cracks, i.e., cracks with the largest surface area, it performs layer-by-layer extrusion repair based on 3D digital model slices and path planning results, achieving maximum high-precision maintenance and full filling of damaged areas. For cracks with a small surface crack area but a large area deep within the crack, asphalt material jetting 3D printing technology can be used for repair. Material jetting 3D printing is a technology that uses layer-by-layer spraying and deposition of printing materials to form components. First, the heating element 9 is controlled to raise the temperature of the material cylinder 6 to increase the fluidity of the asphalt material. The needle-shaped discharge tube 27 penetrates deep into the crack, extruding liquid asphalt and lifting it vertically, allowing the asphalt to self-level layer by layer deep within the crack, achieving a more precise and thorough crack filling operation. The temperature sensor 12 can detect the liquid level information when the molten asphalt fills the damaged area of ​​the pavement, so as to close the switch valve 10 in time to complete the crack filling.

[0037] The working principle and workflow of this invention are as follows:

[0038] The tracked vehicle moves to the location of early cracks and minor potholes in the asphalt pavement. A 3D laser scanner 1 scans the area from different angles to obtain elevation information of various points at the cracks and potholes. The collected point cloud data of the damaged asphalt pavement is interconnected to generate tens of thousands of triangular surfaces, which are used to construct a highly accurate 3D digital model. After the data is transmitted to the 3D printing slicing software, slicing and path planning are automatically performed. The robotic arm moves the material cylinder 6 above the cracks or potholes. The solid pump 3 pumps asphalt particles into the material cylinder 6. The heating element 9 heats the asphalt particles. The switch valve 10 is opened, and the auger 8 is driven by the fourth motor 7 to stir, transport, and extrude the asphalt. At the same time, the robotic arm moves the material cylinder 6 along the planned path, causing the asphalt to be stacked layer by layer, completing the precise filling of the cracks or potholes, and thus repairing the asphalt pavement. For cracks with a small surface area but a large depth, a 3D printing repair method using material jetting is employed. The heating element 9 is controlled to raise the temperature of the material cylinder 6, increasing the fluidity of the asphalt material. The liquid asphalt is then extruded through the needle-shaped discharge pipe 27 into the crack and lifted vertically, allowing the asphalt to self-level layer by layer deep within the crack, achieving a more precise and thorough repair. A temperature sensor 12 detects the liquid level information as the molten asphalt fills the damaged area of ​​the road surface, and the switch valve 10 is closed in time to complete the repair. The asphalt fumes generated by the heating element 9 enter the plate absorption tower 19. The tar particles in the asphalt fumes are absorbed by water and float to the surface. The waste liquid is discharged from the drain port at the bottom of the plate absorption tower 19. The gas passing through the plate absorption tower 19 then enters the activated carbon box 20 through the purification connection pipe 16 for secondary adsorption, and finally is discharged into the atmosphere from the exhaust port of the activated carbon box 20.

[0039] Any aspects not covered in this invention are applicable to existing technologies.

Claims

1. A 3D printing extrusion robot for repairing early-stage cracks and minor potholes in asphalt pavement, comprising a tracked chassis and a robotic arm; characterized in that, The robot also includes a road condition detection component, a material discharge component, an exhaust gas purification component, and a control system. The tracked chassis is used to carry the hardware devices of each component and move flexibly during the maintenance of early cracks and minor potholes in asphalt pavement. The road condition detection component is used to collect information on early cracks and minor potholes in asphalt pavement to provide a basis for building a 3D digital model. The material discharge component is used to heat and store solid asphalt particles and extrude them precisely according to the 3D printing path planning and the required amount. The exhaust gas purification component is used to purify the fumes generated during the asphalt heating process. The control system ensures the coordinated operation of the robot's components in the 3D printing maintenance and repair of early cracks and minor potholes in asphalt pavement. The tracked vehicle chassis is a lithium battery tracked vehicle, used to carry hardware devices such as a robotic arm, road condition detection components, material discharge components, exhaust gas purification components, and control system. The first motor of the robotic arm is located on the top of the tracked vehicle chassis, controlling the robotic arm chassis to rotate 180 degrees in the horizontal direction. The second motor is located on the upper part of the robotic arm chassis, controlling the robotic arm's upper arm to rotate 90 degrees in the vertical direction. The third motor is located at the end of the robotic arm's upper arm, controlling the robotic arm's lower arm to rotate 180 degrees in the vertical direction. The road condition detection component includes three 3D laser scanners located at different positions, which can perform 3D laser scanning at different angles and cooperate with the control system to construct 3D digital models of early cracks and minor potholes in asphalt pavement. The discharge assembly includes a hopper, a solid-state pump, a feed pipe, a telescopic section of the feed pipe, a cylinder, a No. 4 motor, an auger, a heating element, a switching valve, an extrusion port, and a temperature sensor. The solid-state pump on the side of the hopper is connected to the feed inlet at the top of the cylinder via the feed pipe. The cylinder is fixed to the end of the robotic arm's forearm via a bracket on the long end of a right-angle steel plate. The bracket has two semi-circular rings bolted together. The No. 4 motor is mounted on the top of the short end of the right-angle steel plate. The output shaft of the No. 4 motor penetrates the top of the cylinder and extends into the cylinder. The auger is fixed to the end of the No. 4 motor's output shaft. The heating element is mounted on the inner wall of the cylinder. The temperature sensor is located at the end of the extrusion port. The exhaust gas purification assembly includes a purification connecting pipe, an exhaust pipe, an exhaust pipe extension section, a plate absorption tower, and an activated carbon box; the exhaust port at the top of the material cylinder is connected to the exhaust port at the bottom of the plate absorption tower through the exhaust pipe, and the exhaust port at the top of the plate absorption tower is connected to the input end at the bottom of the activated carbon box through the purification connecting pipe. After the road condition detection component constructs a 3D digital model of the asphalt pavement damage, the control system imports it into the 3D printing slicing software. Based on the slicing and path planning results, it controls the movement of the robotic arm, turns on the heating plate on the inner wall of the material cylinder, controls the solid pump to pump solid asphalt particles into the material cylinder, opens the switch valve, and as the No. 4 motor drives the auger to rotate, molten asphalt is extruded from the extrusion port. The extrusion port is in the form of a screw thread and is equipped with discharge pipes of different specifications. The extrusion head of the discharge pipe includes a round head, a square head, or a flat head. The material conveying pipe is adjacent to a portion of the material cylinder, which is a material conveying pipe extension section, and the exhaust pipe is adjacent to a portion of the material cylinder, which is an exhaust pipe extension section.

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