Microwave welding method and welding device

Abstract

The invention discloses a microwave welding method and a welding device, and relates to the technical field of microwave welding, the welding method comprises the following steps: coating a wave absorbing material on a welding area of two plates needing to be welded, and placing the two plates on a substrate of a workbench; the running direction and speed of the three-dimensional moving frame are planned according to the shape needing to be welded; the antenna array welding module is connected with a microwave source to start welding; the microwave power is adjusted according to the temperature and the welding condition of the two plates, so that the areas, with the wave-absorbing materials, of the two plates are heated to a molten state, and welding is completed; and the microwave source and the workbench are closed, and the two welded plates are taken out. The device is reasonable in design, welding of large-size and complex-structure workpieces is achieved through microwave radiation of the antenna array welding module, the energy focusing place can be changed by moving the position of the antenna array welding module, and local directional welding of the large-size workpieces is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of microwave welding, more particularly to the technical field of a microwave welding method and a welding device. BACKGROUND

[0002] Microwave heating technology is based on the principle that the absorption of microwave energy by materials is the result of the interaction between polar molecules in the materials and the microwave electromagnetic field. Under the action of an external alternating electromagnetic field, the polar molecules in the materials polarize and change their orientation with the external alternating electromagnetic field. As a result of the frequent mutual friction of a large number of polar molecules, electromagnetic energy is converted into heat energy and other forms of energy to heat the materials.

[0003] Traditional welding technologies (hot plate welding / ultrasonic welding) have high energy consumption, the material is prone to deformation, and the interface is prone to the generation of bubbles and cracks. The long heating time leads to deformation, and overall heating causes the material to bend as a whole.

[0004] Microwave welding, on the other hand, uses dielectric loss to directly convert electromagnetic energy into heat energy, has the advantages of non-contact, high efficiency, and deep heating, and can avoid the generation of cracks and bubbles at the interface caused by mechanical contact. In addition, microwaves have the characteristic of selective heating, allowing for directional heating of local areas. However, high molecular polymers are generally transparent to microwaves, i.e., they have poor microwave absorption ability, and therefore require the addition of microwave absorbers to convert electromagnetic energy into heat energy. The traditional microwave welding process is as follows: first, apply CNTs, carbon black, or other wave-absorbing materials to the welding area on the welding plate, align the welding area of the second plate with the wave-absorbing material on the first plate, and press the two plates together using a presser on a horizontal base plate; then place the preprocessed plates in a cavity and introduce microwaves for heating and welding; finally, remove the workpiece from the cavity, and the welding area with the pressed wave-absorbing material has completed the welding. Traditional microwave welding is performed in a closed waveguide, which has the following technical problems: 1. Due to the limited space of the traditional welding cavity, the size and shape of the workpiece are constrained by the waveguide structure, making it difficult to adapt to the welding needs of complex shapes or large-sized components.

[0005] 2. The electromagnetic field in the traditional closed waveguide is a standing wave distribution, and the energy changes periodically, which cannot be effectively concentrated in the welding area, resulting in low heating efficiency and inability to effectively concentrate energy in the welding area for local welding. 3. The microwave energy distribution in the closed waveguide is uneven, which can cause large temperature gradient distribution at the welding interface of the workpiece, leading to uneven welding, local deformation of the material, and even false welding or unstable welding quality. SUMMARY

[0006] The purpose of this invention is to solve the above-mentioned technical problems by providing a microwave welding method and apparatus that enables precise local welding of large-sized or complex curved workpieces, thereby improving welding uniformity and energy utilization efficiency.

[0007] To achieve the above objectives, the present invention specifically adopts the following technical solution: The first aspect of the present invention provides a microwave welding method, comprising the following steps: S1. Determine the workpiece area to be welded on the first and second plates. Apply microwave absorbing material to the welding area of ​​the two plates to be welded. Fix the two plates and place them parallel to each other on the base plate of the workbench. S2. Fix the antenna array welding module on the three-dimensional moving frame of the workbench, and adjust the position of the antenna array welding module on the three-dimensional moving frame so that it is aligned with the area to be welded and at a set distance above the welding area. S3. Plan the running direction and speed of the three-dimensional moving frame according to the shape of the area to be welded; S4. Connect the antenna array welding module to the microwave source and begin the welding operation; S5. Adjust the microwave power according to the temperature and welding condition of the two plates to heat up the areas with microwave absorbing material on the two plates to a molten state and complete the local welding. S6. The three-dimensional moving frame moves along the planned path and direction with the antenna array welding module to weld other areas to be welded until the welding of the entire welding area is completed. S7. Turn off the microwave source and the worktable, and remove the soldered board.

[0008] A second aspect of the invention provides a welding apparatus applicable to the microwave welding method described above, comprising a worktable, a fixing assembly provided on the worktable for fixing two plates to be welded, a three-dimensional moving frame disposed on the worktable, and an antenna array welding module mounted on the three-dimensional moving frame.

[0009] In one embodiment, the three-dimensional moving frame includes a portal frame capable of moving longitudinally along the worktable and a mover capable of moving laterally along the top crossbeam of the portal frame. The antenna array welding module is installed below the mover. The portal frame includes two vertical guide rails provided on both sides of the worktable. The two ends of the crossbeam are respectively provided with lifting guide holes that allow the corresponding vertical guide rails to pass through. The two sides of the worktable are provided with longitudinal slide rails that allow the corresponding vertical guide rails to slide longitudinally. In one embodiment, a lifting drive mechanism for raising and lowering the crossbeam is provided on the vertical guide rail, a lateral drive mechanism for driving the mover to move laterally is provided on the crossbeam, and a longitudinal drive mechanism for driving the vertical guide rail to move longitudinally is provided on the longitudinal slide rail.

[0010] In one embodiment, the lifting drive mechanism, the lateral drive mechanism, and the longitudinal drive mechanism are electric lead screws, cylinders, or hydraulic cylinders.

[0011] In one embodiment, the antenna array welding module includes a dielectric plate fixed to a mover via a connecting rod. At least two rows of horizontally arranged patch antenna assemblies are disposed on the dielectric plate. Each row of patch antenna assemblies includes multiple patch units arranged at intervals. The patch units of adjacent rows of patch antenna assemblies are staggered, and the projection edges of all patch units on adjacent rows of patch antenna assemblies partially overlap in the longitudinal direction.

[0012] In one embodiment, each patch unit includes a metal ground layer disposed above the dielectric substrate and a metal patch layer disposed below the dielectric substrate corresponding to the position of the metal ground layer. The metal ground layer is provided with a coaxial feed port, and each coaxial feed port is connected to a microwave source through a coaxial feed line. The outer conductor of the coaxial feed port is soldered onto the metal grounding layer; The inner conductor of the coaxial feed port passes through the dielectric substrate and is soldered onto the metal patch layer.

[0013] In one embodiment, two rows of horizontally arranged patch antenna assemblies are disposed on the dielectric substrate, and each row of patch antenna assemblies includes a plurality of patch units arranged horizontally at equal intervals.

[0014] In one embodiment, the system further includes a temperature control system, which includes a temperature sensor array or infrared imager array for detecting the temperature of the plate to be welded on the workbench, a main control unit, and a data display interface. The temperature sensor array or infrared imager array is signal-connected to the main control unit, and the main control unit is signal-connected to the microwave source and the data display interface.

[0015] In one embodiment, the two plates are a first plate and a second plate, respectively. A microwave absorbing material layer is coated on the area of ​​the first plate and / or the second plate that needs to be welded. The microwave absorbing material layer is made of carbon nanotube microwave absorbing material. The carbon nanotube microwave absorbing material is coated on the first plate and / or the second plate to form a spherical shell composite structure. Under the action of microwaves, the spherical shell composite structure realizes the rapid heating of the microwave absorbing material layer and melts the surface of the particles.

[0016] The beneficial effects of this invention are as follows: 1. This invention is rationally designed. Its purpose is to utilize microwave radiation to weld large and complex workpieces in an open space, overcoming the limitations of traditional microwave welding which is performed within a cavity. By shifting the position of the moving antenna array welding module, the energy focusing point is altered, enabling localized directional welding of large workpieces.

[0017] 2. By adjusting the position and distance of the antenna array welding module through a three-dimensional movable worktable, welding of complex structures such as curved surfaces and gaps can be completed, while simultaneously achieving programmable and automated control of the welding path. Microwave energy is concentrated in the welding area, achieving precise energy focusing and improving energy utilization.

[0018] 3. This invention incorporates carbon nanotubes (CNTs) as microwave-absorbing material at the welding interface. This allows the CNTs to achieve efficient electromagnetic energy to thermal energy conversion through the synergistic effect of dielectric and ohmic losses in a microwave field. Significant microwave absorption is achieved even when the CNT content is below 1%, thereby significantly improving energy utilization. Furthermore, the spherical shell composite structure formed by CNT-coated material particles enables rapid heating of the CNT layer and melting of the particle surface under microwave irradiation, promoting the formation of localized welds at the interface. By introducing microwave-absorbing materials such as CNTs into areas requiring welding, selective heating of the interface can be achieved, avoiding thermal damage caused by overall heating. Simultaneously, the rapid microwave heating rate effectively prevents structural deformation in the welded area caused by prolonged heating. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a flowchart of a microwave welding method; Figure 2 This is a structural diagram of the welding equipment; Figure 3 This is a structural schematic diagram of the antenna array welding module; Figure 4 This is a schematic diagram of the welding plates and the welding area; Figure 5 From left to right, the diagrams show the radiated electric field distribution, radiated magnetic field distribution, and surface current distribution of a single radiating antenna element.

[0021] Figure 6 Schematic diagram of the antenna array welding module and the plate material; Figure 7 yes Figure 6 Simulation diagram of heating process; Figure 8 This is a diagram showing the heating effect in the overlapping area of ​​the boards; Figure 9 This is the logical framework diagram of the temperature control system; Figure 10 This is a schematic diagram of the surface mount unit structure; Reference numerals: 1. Workbench; 2. Antenna array welding module; 3. First plate; 4. Second plate; 5. Vertical guide rail; 6. Coaxial feed line; 7. Microwave source; 8. Crossbeam; 9. Movers; 21. Medium substrate; 22. Surface mount unit; 221. Coaxial feed port; 222. Metal patch layer; 223. Metal grounding layer. Detailed Implementation

[0022] To make the technical problems, technical solutions, and technical effects of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0023] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0024] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0025] In the description of the embodiments of the present invention, it should be noted that the terms "inner", "outer", "upper", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the present invention.

[0026] Example 1 like Figure 1 As shown, the first aspect of the present invention provides a microwave welding method, comprising the following steps: S1. Determine the workpiece area to be welded on the first plate 3 and the second plate 4. Apply microwave absorbing material to the welding area of ​​the two plates to be welded. Fix the two plates and place them parallel to each other on the base plate of the workbench 1. S2. Fix the antenna array welding module on the three-dimensional moving frame of the workbench 1. Adjust the position of the antenna array welding module on the three-dimensional moving frame so that it is aligned with the area to be welded and at a preset distance above the welding area. S3. Plan the running direction and speed of the three-dimensional moving frame according to the shape of the area to be welded; S4. Connect the antenna array welding module to microwave source 7 and begin the welding operation; S5. Adjust the microwave power according to the temperature and welding condition of the two plates to heat up the areas with microwave absorbing material on the two plates to a molten state to complete the local welding. S6. The three-dimensional moving frame moves along the planned path and direction with the antenna array welding module to weld other areas to be welded until the welding of the entire welding area is completed. S7. Turn off microwave source 7 and workbench 1, and remove the soldered plate.

[0027] Figure 5 From left to right, the diagrams show the radiated electric field distribution, radiated magnetic field distribution, and surface current distribution of a single radiating antenna element. It can be seen that a uniform strong electric field is distributed along the corresponding areas on both sides of the long side of the patch, and a uniform strong magnetic field is distributed along the corresponding areas on both sides of the wide side of the patch, consistent with the surface current distribution areas. The welding of the absorbing material is completed under the strong electric field region.

[0028] Figure 8 This is a heating effect diagram of the overlapping area of ​​the board. When heated for 30 seconds at 150W microwave power, the overlapping area of ​​the board (the microwave absorbing material area) rises to 312℃.

[0029] Example 2 like Figures 2-4 and Figure 10 This embodiment provides a welding apparatus applicable to the microwave welding method described above, including a worktable 1, a fixing assembly for fixing two plates to be welded on the worktable 1, a three-dimensional moving frame set on the worktable 1, and an antenna array welding module installed on the three-dimensional moving frame.

[0030] The three-dimensional moving frame includes a gantry frame that can move longitudinally along the worktable 1 and a mover 9 that can move laterally along the top beam 8 of the gantry frame. The antenna array welding module is installed below the mover 9. The gantry frame includes two vertical guide rails 5 set on both sides of the worktable 1. The beam 8 has lifting guide holes at both ends that allow the corresponding vertical guide rails 5 to pass through. The worktable 1 has longitudinal slide rails on both sides that allow the corresponding vertical guide rails 5 to slide longitudinally. The vertical guide rail 5 is equipped with a lifting drive mechanism that drives the crossbeam 8 to rise and fall. The crossbeam 8 is equipped with a lateral drive mechanism that drives the mover 9 to move laterally. The longitudinal slide rail is equipped with a longitudinal drive mechanism that drives the vertical guide rail 5 to move longitudinally.

[0031] The lifting drive mechanism, the lateral drive mechanism, and the longitudinal drive mechanism are electric lead screws, pneumatic cylinders, or hydraulic cylinders.

[0032] The antenna array welding module 2 includes a dielectric plate 21 fixed to the mover 9 by a connecting rod. At least two rows of patch antenna assemblies are arranged laterally on the dielectric plate 21. Each row of patch antenna assemblies includes multiple patch units 22 arranged at intervals. The patch units 22 of adjacent rows of patch antenna assemblies are arranged in an alternating manner, and the projection edges of all patch units 22 on adjacent rows of patch antenna assemblies partially overlap in the longitudinal direction.

[0033] Each patch unit 22 includes a metal ground layer 223 disposed above the dielectric substrate 21 and a metal patch layer 222 disposed below the dielectric substrate 21 corresponding to the position of the metal ground layer 223. The metal ground layer 223 is provided with a coaxial feed port 221, and each coaxial feed port 221 is connected to a microwave source 7 through a coaxial feed line 6. The outer conductor of the coaxial feed port 221 is welded to the metal grounding layer 223; The inner conductor of the coaxial feed port 221 passes through the dielectric substrate and is soldered onto the metal patch layer 222.

[0034] The two plates are the first plate 3 and the second plate 4. The areas of the first plate 3 and / or the second plate 4 that need to be welded are coated with a microwave absorbing material layer. The microwave absorbing material layer is made of carbon nanotube microwave absorbing material. The carbon nanotube microwave absorbing material is coated on the first plate 3 and / or the second plate 4 to form a spherical shell composite structure. Under the action of microwaves, the spherical shell composite structure can achieve rapid heating of the microwave absorbing material layer and melt the surface of the particles.

[0035] In this embodiment, when the antenna array welding module is working, the microwave source feeds electromagnetic energy into each patch unit via a coaxial feeder. Each patch unit generates a resonant electromagnetic field at a specific frequency, and the resonant field generates a strong electric field in the near-field region. Because adjacent patch units are arranged in a staggered "W" shape, complementary high electric field bands are formed in the welding area, achieving localized and efficient heating of the welding interface.

[0036] When the surface of the welding area is coated with microwave absorbing materials such as carbon nanotubes (CNTs) or carbon black, the material generates significant dielectric and ohmic losses under the action of a high-intensity electric field, rapidly converting microwave energy into heat energy. This causes the welding interface temperature to rise rapidly to the melting temperature of the thermoplastic polymer. Due to the concentrated energy and controlled heating area, heat can be transferred to the interface layer within seconds, causing melting and molecular chain diffusion at the interface of the two plates, thereby achieving a strong weld.

[0037] Example 3 This embodiment is a further optimization based on embodiment 2, specifically: Two rows of horizontally arranged patch antenna assemblies are provided on the dielectric substrate 21, and each row of patch antenna assemblies includes several patch units 22 arranged horizontally at equal intervals.

[0038] Example 4 This embodiment is a further optimization based on embodiment 3, specifically: It also includes a temperature control system, which includes a temperature sensor array or infrared imager array for detecting the temperature of the plate to be welded on the workbench 1, a main control unit, and a data display interface. The temperature sensor array or infrared imager array is connected to the main control unit, and the main control unit is connected to the microwave source 7 and the data display interface.

[0039] Specifically, the main control unit acquires the temperature signal of the welding area in real time and uses a proportional-integral-derivative (PID) control algorithm to adjust the input power of the antenna array welding module. When the detected temperature is lower than the target temperature, the main control unit maintains the microwave source output power at approximately 150 W to maintain the heating rate; when the temperature approaches or exceeds the set target temperature, it automatically reduces the input power to prevent local overheating or material ablation.

[0040] The target temperature is set based on the melting temperature of the polymer material being welded, and is typically about 10-20°C higher than the material's melting temperature. For example, for polyamide (PA) or polybutylene terephthalate (PBT) materials, the target welding temperature is approximately 230°C, with a control accuracy of ±5°C.

[0041] This temperature control system allows the temperature of the welding area to stabilize at the set value within a short time, enabling rapid melting of the interface layer and diffusion of molecular chains, thus ensuring welding uniformity and strength. Compared to traditional open-loop microwave heating, this embodiment significantly improves the temperature control accuracy and repeatability of the welding process, preventing overheating, incomplete welding, or uneven interface.

Claims

1. A microwave welding method, characterized in that, Includes the following steps: S1. Determine the workpiece area to be welded on the first and second plates. Apply microwave absorbing material to the welding area of ​​the two plates to be welded. Fix the two plates and place them parallel to each other on the base plate of the workbench. S2. Fix the antenna array welding module on the three-dimensional moving frame of the workbench, and adjust the position of the antenna array welding module on the three-dimensional moving frame so that it is aligned with the area to be welded and at a set distance above the welding area. S3. Plan the running direction and speed of the three-dimensional moving frame according to the shape of the area to be welded; S4. Connect the antenna array welding module to the microwave source and begin the welding operation; S5. Adjust the microwave power according to the temperature and welding condition of the two plates to heat up the areas with microwave absorbing material on the two plates to a molten state and complete the local welding. S6. The three-dimensional moving frame moves along the planned path and direction with the antenna array welding module to weld other areas to be welded until the welding of the entire welding area is completed. S7. Turn off the microwave source and the worktable, and remove the soldered board.

2. A welding apparatus, suitable for the microwave welding method according to claim 1, characterized in that, The device includes a workbench, a fixing assembly for fixing two plates to be welded on the workbench, a three-dimensional moving frame set on the workbench, and an antenna array welding module mounted on the three-dimensional moving frame. The two plates are placed in the welding area of ​​the workbench.

3. The welding apparatus according to claim 2, characterized in that, The three-dimensional moving frame includes a gantry frame capable of moving longitudinally along the workbench and a mover capable of moving laterally along the top crossbeam of the gantry frame. The antenna array welding module is installed below the mover. The gantry frame includes two vertical guide rails arranged on both sides of the workbench. The two ends of the crossbeam are respectively provided with lifting guide holes that allow the vertical guide rails to pass through. The two sides of the workbench are provided with longitudinal slide rails that allow the vertical guide rails to slide longitudinally.

4. The welding apparatus according to claim 3, characterized in that, The vertical guide rail is equipped with a lifting drive mechanism that drives the crossbeam to rise and fall, the crossbeam is equipped with a lateral drive mechanism that drives the locator to move laterally, and the longitudinal slide rail is equipped with a longitudinal drive mechanism that drives the vertical guide rail to move longitudinally.

5. The welding apparatus according to claim 4, characterized in that, The lifting drive mechanism, the lateral drive mechanism, and the longitudinal drive mechanism are electric lead screws, cylinders, or hydraulic cylinders.

6. The welding apparatus according to claim 4, characterized in that, The antenna array welding module includes a dielectric plate fixed to the mover by a connecting rod. At least two rows of horizontally arranged patch antenna assemblies are provided on the dielectric plate. Each row of patch antenna assemblies includes multiple patch units arranged at intervals. The patch units of adjacent rows of patch antenna assemblies are staggered, and the projection edges of all patch units on adjacent rows of patch antenna assemblies partially overlap in the longitudinal direction.

7. The welding apparatus according to claim 6, characterized in that, Each of the patch units includes a metal ground layer disposed above the dielectric substrate and a metal patch layer disposed below the dielectric substrate corresponding to the position of the metal ground layer. The metal ground layer is provided with a coaxial feed port, and each of the coaxial feed ports is connected to a microwave source through a coaxial feed line. The outer conductor of the coaxial feed port is welded to the metal grounding layer; The inner conductor of the coaxial feed port passes through the dielectric substrate and is soldered onto the metal patch layer.

8. The welding apparatus according to claim 6, characterized in that, The dielectric substrate is provided with two rows of horizontally arranged patch antenna assemblies, and each row of patch antenna assemblies includes several patch units arranged horizontally at equal intervals.

9. The welding apparatus according to claim 6, characterized in that, It also includes a temperature control system, which includes a temperature sensor array or infrared imager array for detecting the temperature of the plate to be welded on the workbench, a main control unit, and a data display interface. The temperature sensor array or the infrared imager array is signal-connected to the main control unit, and the main control unit is signal-connected to the microwave source and the data display interface.

10. The welding apparatus according to claim 2, characterized in that, The two plates are designated as the first plate and the second plate. The areas of the first plate and / or the second plate that need to be welded are coated with a microwave absorbing material layer. The microwave absorbing material layer is made of carbon nanotube microwave absorbing material. The carbon nanotube microwave absorbing material is a spherical shell composite structure formed by coating material particles on the first plate and / or the second plate. Under the action of microwaves, the spherical shell composite structure achieves rapid heating of the microwave absorbing material layer and melts the surface of the particles.

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