An ultrasonic welding method

Abstract

This invention relates to the field of material welding technology, specifically to an ultrasonic welding method, comprising the following steps: Step 1, parameter preset; Step 2, pre-pressure positioning; Step 3, segmented welding, starting the ultrasonic generator and employing a three-stage segmented welding process, including: First stage: triggering stage, using a first amplitude and a first pressure for a first preset time; Second stage: melting and expansion stage, using a second amplitude and a second pressure for a second preset time, where the second amplitude is greater than the first amplitude and the second pressure is greater than the first pressure; Third stage: pressure holding and solidification stage, stopping ultrasonic output and maintaining a third pressure for a third preset time; Step 4, real-time monitoring and feedback; Fifth stage: post-weld inspection. This invention, employing a three-stage segmented welding process, solves problems such as difficulty in initial melting of materials, uneven expansion of the molten area, and internal stress caused by cooling contraction in traditional constant parameter welding.

Description

Technical Field

[0001] This invention relates to the field of material welding technology, and specifically to an ultrasonic welding method. Background Technology

[0002] Ultrasonic welding is a solid-state welding technology that uses high-frequency mechanical vibration energy to join similar or dissimilar materials. It is widely used in automotive parts, consumer electronics, medical devices, and other fields. Its core principle is to generate localized heat energy through high-frequency vibration friction, which softens or melts the materials and achieves molecular-level bonding under pressure.

[0003] Existing ultrasonic welding methods typically employ constant amplitude, pressure, and welding time, which presents the following technical problems: First, for workpieces made of different materials (such as ABS, PC, nylon, etc.) or with different thicknesses and shapes, constant parameters cannot adapt to the differences in material properties, easily leading to insufficient welding strength or over-welding. Second, during the welding process, factors such as contaminants on the workpiece surface, batch differences in materials, and changes in ambient temperature can affect energy absorption efficiency, and traditional open-loop control cannot adjust in real time, resulting in unstable welding quality. Third, for workpieces with complex geometries (such as those with reinforcing ribs, thin-walled structures, or multiple weld points), a single welding head cannot achieve uniform energy distribution, easily resulting in localized incomplete welds or over-melting. Fourth, existing methods lack real-time monitoring and feedback control of the welding melting state, making closed-loop adjustment impossible and leading to a high defect rate. Fifth, when welding different material combinations (such as metal and plastic), existing methods result in poor interfacial bonding strength, making them prone to peeling. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an ultrasonic welding method that addresses the shortcomings of existing ultrasonic welding techniques, such as fixed parameters, poor adaptability, and unstable welding quality. This method achieves consistency and improved reliability of welding strength through multi-stage segmented welding, real-time energy monitoring and feedback control, adaptive frequency tuning, and intelligent parameter matching.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: An ultrasonic welding method, comprising the following steps: Step 1: Parameter preset. Based on the material type, thickness and geometry of the workpiece to be welded, the initial welding parameters are retrieved from the process database. The initial welding parameters include initial amplitude, initial pressure, initial welding time and initial frequency. Step 2, pre-pressure positioning: The first and second workpieces are stacked in the welding fixture, and the welding head presses the workpieces with pre-pressure, which is 50%-80% of the set welding pressure; Step 3, segmented welding: Start the ultrasonic generator and perform welding using a three-segment segmented welding process, including: Phase 1: Triggering phase, using the first amplitude and the first pressure, lasting for the first preset time; Second stage: Melt expansion stage, using a second amplitude and a second pressure for a second preset time, where the second amplitude is greater than the first amplitude and the second pressure is greater than the first pressure; Third stage: Pressure holding and curing stage, stop ultrasonic output, maintain the third pressure for the third preset time; Step 4: Real-time monitoring and feedback. During the segmented welding process, the amplitude, frequency, power of the welding head and the displacement of the workpiece are collected in real time. The collected data are compared with the preset threshold of the initial welding parameters in Step 1. When the deviation exceeds the set range, the controller automatically adjusts the amplitude or welding time of the current stage. Step 5: Post-weld inspection. After welding is completed, the weld points are judged online. If the welds are judged to be unqualified, they will be automatically marked or an alarm will be triggered.

[0006] The beneficial effects of this invention are as follows: It employs a three-stage segmented welding process (trigger-melt propagation-pressure holding and solidification), solving problems such as difficulty in initial material melting, uneven expansion of the molten region, and internal stress caused by cooling contraction in traditional constant-parameter welding. The trigger stage initiates surface micro-melting with small amplitude and low pressure, avoiding excessive initial energy that could cause spatter; the melt propagation stage achieves full fusion with large amplitude and high pressure; and the pressure holding and solidification stage maintains pressure without ultrasound, ensuring full orientation of the molecular chains and eliminating internal stress. Simultaneously, real-time monitoring and feedback control are introduced, transforming the welding process from an open-loop to a closed-loop system, significantly improving welding consistency and reliability.

[0007] Based on the above technical solution, the present invention can be further improved as follows.

[0008] Furthermore, in step three, in the segmented welding process, an energy adjustment stage is set between the second stage and the third stage. This stage adopts a third amplitude and a third pressure. The third amplitude is between the first amplitude and the second amplitude, and the third pressure is between the first pressure and the second pressure, lasting for a fourth preset time.

[0009] The beneficial effects of adopting the above-mentioned further scheme are: adding an energy dressing stage and using intermediate amplitude and pressure to perform secondary treatment on the molten layer can effectively eliminate the micro-pores that may be generated during the melting process, making the weld more dense.

[0010] Furthermore, in step four, the parameters collected in real time also include the resonant frequency offset of the welding head. When the resonant frequency offset exceeds the preset threshold of the initial frequency in the initial welding parameters of step one, the controller automatically tracks the frequency by adjusting the output frequency of the ultrasonic generator, so that the welding head always works in a resonant state.

[0011] The beneficial effects of adopting the above-mentioned further solution are: real-time frequency tracking solves the problem of resonant frequency drift caused by factors such as load changes, temperature rise, and welding head wear during ultrasonic welding. When the welding head deviates from the resonant frequency, the energy conversion efficiency drops sharply, and the generator may even be damaged. This solution ensures that the welding head always works at the optimal resonant point by detecting the frequency deviation in real time and tracking it automatically, thereby improving energy utilization and extending the life of the welding head and generator.

[0012] Furthermore, between step two and step three, a material identification step is also included: transmitting detection pulses to the workpiece through an ultrasonic probe, automatically identifying the workpiece material type based on the characteristics of the echo signal, and matching the corresponding welding parameters from the process database.

[0013] The beneficial effects of adopting the above-mentioned further solution are: the automatic material identification function enables the equipment to have "intelligent" characteristics. Different materials (such as ABS, PC, and nylon) have significantly different absorption characteristics of ultrasonic waves. Existing methods require manual input of material types. This solution automatically identifies materials and calls up optimal parameters by emitting detection pulses and analyzing echoes (such as sound velocity, attenuation coefficient, and other characteristics), avoiding human error. It is especially suitable for multi-variety mixed production line scenarios and shortens changeover time.

[0014] Furthermore, the welding fixture is equipped with a temperature sensor and a pressure sensor. The temperature sensor is used to monitor the real-time temperature of the welding area, and the pressure sensor is used to monitor the real-time contact pressure between the welding head and the workpiece.

[0015] The advantages of adopting the above-mentioned further solution are: integrating temperature and pressure sensors into the fixture enables multi-physical quantity monitoring of the welding process. Excessive temperature can lead to material thermal degradation or overflow, while pressure fluctuations can affect the consistency of the molten layer thickness. This solution, through real-time monitoring, automatically reduces amplitude or pauses welding when the temperature exceeds the limit, and automatically replenishes pressure when it is insufficient, effectively preventing overheating, scorching, and incomplete weld defects, thus improving the product qualification rate.

[0016] Furthermore, the ultrasonic welding method is applicable to the welding of dissimilar materials, including combinations of metals and plastics, wherein a microstructure is prefabricated or a coupling agent layer is coated on the metal surface before welding.

[0017] The beneficial effects of adopting the above-mentioned further solutions are as follows: In response to the technical challenge of welding dissimilar materials (especially metals and plastics), this solution significantly improves the bonding strength of dissimilar materials by prefabricating microstructures (such as micropores, grooves, and protrusions) or coating a coupling agent layer on the metal surface. The microstructures provide mechanical interlocking anchor points, and the coupling agent layer forms chemical bond bridges between the metal and the plastic, thereby improving the interfacial peel strength and meeting the needs of the automotive, electronics and other industries for joining dissimilar materials.

[0018] Furthermore, the welding head in step two is a multi-contact array welding head, which contains multiple independently controlled welding units, each of which can independently adjust the amplitude and pressure.

[0019] The beneficial effects of adopting the above-mentioned further solution are as follows: the multi-contact array welding head solves the problem of uniformity in welding multiple welding points of complex workpieces. Traditional single welding heads need to weld multiple welding points in multiple stages, which is inefficient and the consistency of each welding point is poor. The array welding head of this solution can independently control the amplitude and pressure of each welding unit, realize synchronous welding of all welding points, and compensate for the uneven energy distribution caused by different positions through differentiated parameters, so that the strength deviation of each welding point is less than 5%, which greatly improves production efficiency and product consistency.

[0020] Furthermore, in step three, during the segmented welding process, the welding collapse amount is calculated in real time based on the displacement of the workpiece. When the collapse amount reaches the preset target value, the controller automatically terminates the ultrasonic output of the current stage and enters the next stage.

[0021] The beneficial effects of adopting the above-mentioned further solution are: the welding endpoint judgment method based on displacement (collapse) is more scientific than the traditional timed control. During ultrasonic welding, the melting of the material will cause the workpiece height to drop (collapse). The collapse directly reflects the degree of melting. This solution automatically terminates welding when the preset collapse target is reached by real-time monitoring of the displacement, eliminating the problem of over-welding or under-welding caused by factors such as material thickness tolerance and changes in ambient temperature, and improving the control accuracy of welding quality.

[0022] Furthermore, it also includes an online cleaning step for the welding head: after each preset number of welding operations, a self-cleaning pulse is emitted to the welding head via an ultrasonic generator, causing high-frequency micro-vibrations on the surface of the welding head to remove residues.

[0023] The beneficial effects of adopting the above-mentioned further solution are: the online cleaning function of the welding head solves the long-standing problem of material adhesion to the welding head in ultrasonic welding production lines. During plastic welding, a small amount of molten material adheres to the surface of the welding head, affecting energy transfer and welding quality. Existing methods require manual cleaning by stopping the machine. This solution, however, periodically emits self-cleaning pulses to cause the welding head to generate high-frequency micro-vibrations that dislodge the residue. No machine shutdown or solvents are required. The cleaning frequency can be set to automatically execute once every 50-200 welding cycles, effectively maintaining the cleanliness of the welding head and extending continuous production time.

[0024] Furthermore, in step three, during the segmented welding process, the resonant impedance value of the welding head is collected in real time, and the contact state of the workpiece is determined based on the real-time collected resonant impedance value of the welding head. When the impedance value is lower than the first threshold, it is determined to be a false contact, and the controller increases the pre-pressure; when the impedance value is higher than the second threshold, it is determined to be an overly tight contact, and the controller reduces the pre-pressure; the second threshold is greater than the first threshold.

[0025] The beneficial effects of adopting the above-mentioned further solution are as follows: The resonant impedance of the welding head is an important physical quantity reflecting the contact state between the welding head and the workpiece. When the workpiece surface is uneven, the fixture positioning is off, or debris is present, there may be incomplete contact (low impedance) or excessive contact (high impedance) between the welding head and the workpiece. Incomplete contact leads to a decrease in energy transfer efficiency and insufficient frictional heat, resulting in incomplete welding; excessive contact may lead to workpiece deformation or over-welding. This solution monitors the resonant impedance value in real time and compares it with a preset first threshold (lower limit for incomplete contact) and a second threshold (upper limit for excessive contact), dynamically adjusting the pre-pressure. When the impedance is lower than the first threshold, the controller increases the pre-pressure to ensure a tight fit between the welding head and the workpiece; when the impedance is higher than the second threshold, the pre-pressure is reduced to avoid excessive compression. This closed-loop adjustment mechanism achieves adaptive optimization of the contact state, fundamentally solving the problem of unstable welding quality caused by workpiece tolerances or positioning deviations. Experiments show that adding this feature reduces the rate of incomplete welding defects caused by poor contact. Attached Figure Description

[0026] Figure 1 This is a flowchart of the present invention; Detailed Implementation

[0027] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0028] Example 1 like Figure 1 As shown, this embodiment discloses an ultrasonic welding method, including the following steps: Step 1: Parameter preset. Based on the material type, thickness and geometry of the workpiece to be welded, the initial welding parameters are retrieved from the process database. The initial welding parameters include initial amplitude, initial pressure, initial welding time and initial frequency. Step 2, pre-pressure positioning: The first and second workpieces are stacked in the welding fixture, and the welding head presses the workpieces with pre-pressure, which is 50%-80% of the set welding pressure; Step 3, segmented welding: Start the ultrasonic generator and perform welding using a three-segment segmented welding process, including: Phase 1: Triggering phase, using the first amplitude and the first pressure, lasting for the first preset time; Second stage: Melt expansion stage, using a second amplitude and a second pressure for a second preset time, where the second amplitude is greater than the first amplitude and the second pressure is greater than the first pressure; Third stage: Pressure holding and curing stage, stop ultrasonic output, maintain the third pressure for the third preset time; Step 4: Real-time monitoring and feedback. During the segmented welding process, the amplitude, frequency, power of the welding head and the displacement of the workpiece are collected in real time. The collected data are compared with the preset threshold of the initial welding parameters in Step 1. When the deviation exceeds the set range, the controller automatically adjusts the amplitude or welding time of the current stage. Step 5: Post-weld inspection. After welding is completed, the weld points are judged online. If the welds are judged to be unqualified, they will be automatically marked or an alarm will be triggered.

[0029] In step three, the segmented welding process includes an energy trimming stage between the second and third stages. This stage employs a third amplitude and a third pressure, where the third amplitude is between the first and second amplitudes, and the third pressure is between the first and second pressures, lasting for a fourth preset time. Adding an energy trimming stage, using intermediate amplitude and pressure to perform secondary treatment on the molten layer, effectively eliminates micropores that may arise during the melting process, resulting in a denser weld.

[0030] In step four, the parameters acquired in real time also include the resonant frequency offset of the welding head. When the resonant frequency offset exceeds the preset threshold of the initial frequency in the initial welding parameters of step one, the controller automatically tracks the frequency by adjusting the output frequency of the ultrasonic generator, ensuring that the welding head always operates in a resonant state. Real-time frequency tracking solves the problem of resonant frequency drift caused by factors such as load changes, temperature rise, and welding head wear during ultrasonic welding. When the welding head deviates from the resonant frequency, the energy conversion efficiency drops sharply, and the generator may even be damaged. This solution ensures that the welding head always operates at the optimal resonant point by detecting the frequency offset in real time and automatically tracking it, thereby improving energy utilization and extending the lifespan of the welding head and generator.

[0031] Between steps two and three, a material identification step is included: a detection pulse is emitted to the workpiece via an ultrasonic probe, and the workpiece material type is automatically identified based on the echo signal characteristics. Corresponding welding parameters are then matched from the process database. This automatic material identification function endows the equipment with "intelligent" characteristics. Different materials (such as ABS, PC, and nylon) have significantly different ultrasonic absorption characteristics. Existing methods require manual input of the material type. This solution automatically identifies the material and calls up the optimal parameters by emitting detection pulses and analyzing the echo (such as sound velocity, attenuation coefficient, etc.), avoiding human error. It is particularly suitable for multi-variety mixed-line production scenarios, shortening changeover time.

[0032] The welding fixture is equipped with temperature and pressure sensors. The temperature sensor monitors the real-time temperature of the welding area, and the pressure sensor monitors the real-time contact pressure between the welding head and the workpiece. Integrating these sensors into the fixture enables multi-physical monitoring of the welding process. Excessive temperature can lead to material degradation or overflow, while pressure fluctuations can affect the consistency of the molten layer thickness. This solution, through real-time monitoring, automatically reduces amplitude or pauses welding when the temperature exceeds the limit, and automatically replenishes pressure when it is insufficient, effectively preventing overheating, scorching, and incomplete weld defects, thus improving product yield.

[0033] The ultrasonic welding method described herein is applicable to the welding of dissimilar materials, including combinations of metals and plastics. Before welding, microstructures are prefabricated on the metal surface or a coupling agent layer is coated. Addressing the technical challenge of welding dissimilar materials (especially metals and plastics), this solution significantly improves the bonding strength of dissimilar materials by prefabricating microstructures (such as micropores, grooves, and protrusions) or coating a coupling agent layer on the metal surface. The microstructures provide mechanical interlocking anchors, while the coupling agent layer forms chemical bond bridges between the metal and plastic, thereby improving interfacial peel strength and meeting the needs of industries such as automotive and electronics for joining dissimilar materials.

[0034] The welding head used in step two is a multi-contact array welding head, which contains multiple independently controlled welding units, each of which can independently adjust its amplitude and pressure. The multi-contact array welding head solves the problem of uniformity in welding multiple weld points on complex workpieces. Traditional single welding heads require multiple welding points to be welded in stages, resulting in low efficiency and poor consistency among weld points. The array welding head in this solution can independently control the amplitude and pressure of each welding unit, achieving synchronous welding of all weld points. Simultaneously, it can compensate for uneven energy distribution caused by different positions through differentiated parameters, ensuring that the strength deviation of each weld point is less than 5%, significantly improving production efficiency and product consistency.

[0035] In step three, during the segmented welding process, the welding collapse amount is calculated in real time based on the workpiece displacement. When the collapse amount reaches the preset target value, the controller automatically terminates the ultrasonic output of the current stage and proceeds to the next stage. The welding endpoint determination method based on displacement (collapse amount) is more scientific than traditional timed control. During ultrasonic welding, material melting causes the workpiece height to drop (collapse), and the collapse amount directly reflects the degree of melting. This solution automatically terminates welding when the preset collapse target is reached by monitoring the displacement amount in real time, eliminating over-welding or under-welding problems caused by factors such as material thickness tolerance and changes in ambient temperature, thus improving the control accuracy of welding quality.

[0036] The system also includes an online welding head cleaning step: after each preset number of welding cycles, an ultrasonic generator emits a self-cleaning pulse to the welding head, causing high-frequency micro-vibrations on the welding head surface to remove residue. This online welding head cleaning function solves the long-standing problem of material adhesion to the welding head in ultrasonic welding production lines. During plastic welding, a small amount of molten material adheres to the welding head surface, affecting energy transfer and welding quality. Existing methods require manual cleaning by stopping the machine. This solution, by periodically emitting self-cleaning pulses, causes the welding head to vibrate at high frequency, dislodging residue without stopping the machine or using solvents. The cleaning frequency can be set to automatically execute once every 50-200 welding cycles, effectively maintaining welding head cleanliness and extending continuous production time.

[0037] In step three, during the segmented welding process, the resonant impedance value of the welding head is collected in real time, and the contact state of the workpiece is determined based on the collected resonant impedance value. When the impedance value is lower than the first threshold, it is determined to be a false contact, and the controller increases the pre-pressure; when the impedance value is higher than the second threshold, it is determined to be an over-tight contact, and the controller decreases the pre-pressure; the second threshold is greater than the first threshold. The resonant impedance of the welding head is an important physical quantity reflecting the contact state between the welding head and the workpiece. When the workpiece surface is uneven, the fixture positioning is off, or there are debris, there may be a false contact (low impedance) or an over-tight contact (high impedance) between the welding head and the workpiece. False contact will lead to a decrease in energy transfer efficiency and insufficient frictional heat, resulting in a poor weld; over-tight contact may lead to workpiece deformation or over-welding. This solution monitors the resonant impedance value in real time and compares it with the preset first threshold (lower limit of false contact) and second threshold (upper limit of over-tight contact) to dynamically adjust the pre-pressure. When the impedance is lower than the first threshold, the controller increases the pre-pressure to make the welding head fit tightly against the workpiece; when the impedance is higher than the second threshold, the pre-pressure is reduced to avoid excessive compression. This closed-loop adjustment mechanism achieves adaptive optimization of the contact state, fundamentally solving the problem of unstable welding quality caused by workpiece tolerances or positioning deviations. Experiments show that adding this feature reduces the rate of incomplete weld defects caused by poor contact.

[0038] Example 2 This embodiment discloses a specific welding method for applying the ultrasonic welding method in Embodiment 1 to welding the ABS plastic frame and PVC skin on an automobile door panel.

[0039] Workpiece dimensions: ABS plastic skeleton thickness 2.5mm, PVC skin thickness 0.8mm, weld point diameter 5mm, total 12 weld points.

[0040] S1: Parameter preset, retrieve initial parameters from the process database: initial amplitude 40μm, initial pressure 200N, initial welding time 0.5s, initial frequency 20kHz.

[0041] S2: Pre-pressure positioning, stack the skeleton and skin in the contour jig, and press the welding head with a pre-pressure of 120N (60% of the set welding pressure of 200N).

[0042] S3: Segmented welding, using a four-stage process: Triggering stage: amplitude 30μm, pressure 150N, time 0.1s; Melt propagation stage: amplitude 50μm, pressure 250N, time 0.3s; Energy trimming stage: amplitude 40μm, pressure 200N, time 0.1s; Pressure holding and curing stage: stop ultrasonication, pressure 200N, time 0.3s.

[0043] S4: Real-time monitoring and feedback. During the welding process, if the power sensor detects that the instantaneous power exceeds the preset upper limit by 12%, the controller will automatically reduce the amplitude of the melt expansion stage from 50μm to 45μm, and the power will return to normal.

[0044] S5: Post-weld inspection. The collapse amount is measured by an online displacement sensor and is 0.35mm. If it is within the preset target range of 0.3-0.4mm, it is deemed qualified.

[0045] Results: The peel force test values ​​of all 12 solder joints were between 85-92N, with a range of 7N, a pass rate of 100%, and no poor solder joints or over-melting.

[0046] Example 3 This embodiment is used for welding battery tabs: a nickel tab (0.2 mm thick) and a copper connecting piece (0.3 mm thick). The dissimilar material welding scheme of claim 6 is used, with microgrooves (0.05 mm depth, 0.2 mm spacing) pre-fabricated on the surface of the nickel tab. Welding parameters: trigger amplitude 25 μm, pressure 100 N, time 0.05 s; melt expansion amplitude 35 μm, pressure 150 N, time 0.15 s; holding pressure and curing pressure 120 N, time 0.1 s. Results: The tensile strength of the welded joint reaches 78 N, and the contact resistance is 0.12 mΩ, meeting the standards for power batteries.

[0047] Comparative Example The ABS plastic frame and PVC skin on the car door panel were welded using traditional constant parameters (amplitude 40μm, pressure 200N, time 0.5s, no segmentation, no feedback). Results: The peel force of 12 weld points ranged from 45-95N, with a range of 50N; 3 weak weld points (peel force <50N) were found, resulting in a pass rate of only 75%.

[0048] The beneficial effects of this invention are as follows: It employs a three-stage segmented welding process (trigger-melt propagation-pressure holding and solidification), solving problems such as difficulty in initial material melting, uneven expansion of the molten region, and internal stress caused by cooling contraction in traditional constant-parameter welding. The trigger stage initiates surface micro-melting with small amplitude and low pressure, avoiding excessive initial energy that could cause spatter; the melt propagation stage achieves full fusion with large amplitude and high pressure; and the pressure holding and solidification stage maintains pressure without ultrasound, ensuring full orientation of the molecular chains and eliminating internal stress. Simultaneously, real-time monitoring and feedback control are introduced, transforming the welding process from an open-loop to a closed-loop system, significantly improving welding consistency and reliability.

[0049] In the description of this invention, it should be understood that the terms "center," "length," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "inner," "outer," "circumferential," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the system 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 limitations on this invention.

[0050] In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0051] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0052] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An ultrasonic welding method, characterized in that, Includes the following steps: Step 1: Parameter preset. Based on the material type, thickness and geometry of the workpiece to be welded, the initial welding parameters are retrieved from the process database. The initial welding parameters include initial amplitude, initial pressure, initial welding time and initial frequency. Step 2, pre-pressure positioning: The first and second workpieces are stacked in the welding fixture, and the welding head presses the workpieces with pre-pressure, which is 50%-80% of the set welding pressure; Step 3, segmented welding: Start the ultrasonic generator and perform welding using a three-segment segmented welding process, including: Phase 1: Triggering phase, using the first amplitude and the first pressure, lasting for the first preset time; Second stage: Melt expansion stage, using a second amplitude and a second pressure for a second preset time, where the second amplitude is greater than the first amplitude and the second pressure is greater than the first pressure; Third stage: Pressure holding and curing stage, stop ultrasonic output, maintain the third pressure for the third preset time; Step 4: Real-time monitoring and feedback. During the segmented welding process, the amplitude, frequency, power of the welding head and the displacement of the workpiece are collected in real time. The collected data are compared with the preset threshold of the initial welding parameters in Step 1. When the deviation exceeds the set range, the controller automatically adjusts the amplitude or welding time of the current stage. Step 5: Post-weld inspection. After welding is completed, the weld points are judged online. If the welds are judged to be unqualified, they will be automatically marked or an alarm will be triggered.

2. The ultrasonic welding method according to claim 1, characterized in that, In step three, the segmented welding process includes an energy adjustment stage between the second and third stages. This stage employs a third amplitude and a third pressure, with the third amplitude between the first and second amplitudes and the third pressure between the first and second pressures, lasting for a fourth preset time.

3. The ultrasonic welding method according to claim 1, characterized in that, In step four, the parameters collected in real time also include the resonant frequency offset of the welding head. When the resonant frequency offset exceeds the preset threshold of the initial frequency in the initial welding parameters of step one, the controller automatically tracks the frequency by adjusting the output frequency of the ultrasonic generator, so that the welding head always works in a resonant state.

4. The ultrasonic welding method according to claim 1, characterized in that, Between step two and step three, there is also a material identification step: an ultrasonic probe is used to emit detection pulses to the workpiece, the material type of the workpiece is automatically identified based on the characteristics of the echo signal, and the corresponding welding parameters are matched from the process database.

5. The ultrasonic welding method according to claim 1, characterized in that, The welding fixture is equipped with a temperature sensor and a pressure sensor. The temperature sensor is used to monitor the real-time temperature of the welding area, and the pressure sensor is used to monitor the real-time contact pressure between the welding head and the workpiece.

6. An ultrasonic welding method according to any one of claims 1 to 5, characterized in that, The ultrasonic welding method is applicable to the welding of dissimilar materials, including combinations of metals and plastics. Before welding, microstructures are prefabricated on the metal surface or a coupling agent layer is coated.

7. An ultrasonic welding method according to any one of claims 1 to 5, characterized in that, The welding head in step two is a multi-contact array welding head, which contains multiple independently controlled welding units, each of which can independently adjust the amplitude and pressure.

8. An ultrasonic welding method according to any one of claims 1 to 5, characterized in that, In step three, during the segmented welding process, the welding collapse amount is calculated in real time based on the displacement of the workpiece. When the collapse amount reaches the preset target value, the controller automatically terminates the ultrasonic output of the current stage and enters the next stage.

9. An ultrasonic welding method according to any one of claims 1 to 5, characterized in that, It also includes an online cleaning step for the welding head: after each preset number of welding operations, a self-cleaning pulse is emitted to the welding head via an ultrasonic generator, causing high-frequency micro-vibrations on the surface of the welding head to remove residues.

10. An ultrasonic welding method according to any one of claims 1 to 5, characterized in that, In step three, during the segmented welding process, the resonant impedance value of the welding head is collected in real time, and the contact state of the workpiece is determined based on the collected resonant impedance value of the welding head. When the impedance value is lower than the first threshold, it is determined to be a false contact, and the controller increases the pre-pressure. When the impedance value is higher than the second threshold, it is determined to be an overly tight contact, and the controller reduces the preload. The second threshold is greater than the first threshold.

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