Ultrasonic welder welding method

Abstract

This invention provides an ultrasonic welding method, comprising the following steps: S1: placing welding material on a bottom mold assembly; when the second drive assembly drives the bottom mold assembly to rise to the welding position, the equivalent stiffness of the bottom mold assembly is k; S2: the first drive assembly drives the welding head assembly downward until the welding head assembly contacts the welding material; the equivalent mass of the welding head assembly is m, the downward movement speed is v, and the target deformation and compression value of the bottom mold assembly is s; S3: performing ultrasonic welding; the upward driving force of the bottom mold assembly is F, provided by the second drive assembly, F=(m×v²) / (2×s)-(k×s) / 2; S4: the first drive assembly drives the welding head assembly upward; S5: the second drive assembly drives the bottom mold assembly downward. This ultrasonic welding method effectively avoids the tensile cracking of the welded material due to bottom mold retraction, significantly improving the stability and reliability of the welding quality.

Description

Technical Field

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

[0002] Conventional ultrasonic welding machines only have the upper welding head driven to descend, pressing down onto the workpiece and the bottom mold. If the bottom mold needs to avoid the conveyor line on the production line, the entire ultrasonic welding machine needs to be raised and lowered, resulting in a complex structure and higher cost.

[0003] Therefore, in existing high-speed ultrasonic welding, the upper welding head and the lower bottom mold are driven to rise and fall separately. In the high-speed machine structure, the bottom mold is driven by a cylinder and has a self-locking structure. The self-locking structure will wear under high-frequency vibration, affecting the welding quality, and the cylinder action speed is slow during long strokes.

[0004] If a servo-driven bottom mold is used, the existing technology uses a position mode to determine the working position of the bottom mold. Due to the gaps in the structure and the impact force that causes the bottom mold to retract downwards when the welding head is pressed down, the material between the welding head and the bottom mold, such as metal foil, will be stretched and cracked, or abnormalities may occur during the welding process due to the unstable position of the bottom mold.

[0005] In view of this, it is necessary to improve the existing ultrasonic welding methods to solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to provide an ultrasonic welding method to solve the problems that existing high-speed ultrasonic welding machines are prone to causing material to be stretched or the bottom mold position to be unstable during welding.

[0007] To achieve the above objectives, the present invention provides an ultrasonic welding method, which uses an ultrasonic welding machine for welding. The ultrasonic welding machine includes a welding head assembly, a first driving assembly for driving the welding head assembly to move up and down, a bottom mold assembly disposed below the welding head assembly, and a second driving assembly for driving the bottom mold assembly to move up and down. The ultrasonic welding method includes the following steps:

[0008] S1: When welding materials are placed on the bottom mold assembly and the second drive assembly drives the bottom mold assembly to rise to the welding position, the equivalent stiffness of the bottom mold assembly is k.

[0009] S2: The first driving component drives the welding head assembly to move downward until the welding head assembly contacts the welding material. The equivalent mass of the welding head assembly is m, the downward speed is v, and the target value of the deformation and compression of the bottom mold assembly is s.

[0010] S3: Perform ultrasonic welding. The upward driving force of the bottom mold assembly is F, which is provided by the second driving assembly. F=(m×v²) / (2×s)-(k×s) / 2;

[0011] S4: The first drive component drives the welding head assembly to move upward;

[0012] S5: The second drive component drives the bottom mold component to descend.

[0013] As a further improvement of the present invention, the second driving component is a linear servo motor, which is connected to the bottom mold component.

[0014] As a further improvement of the present invention, the second drive component is a rotary servo motor and a transmission mechanism connecting the rotary servo motor and the bottom mold component.

[0015] As a further improvement of the present invention, the torque of the rotary servo motor is 80%-100% of the rated torque.

[0016] As a further improvement of the present invention, in step S1, when the second drive component drives the bottom mold component to rise to the welding position, the torque of the rotary servo motor is 150%-250% of the rated torque, and in step S3, when welding, the torque of the rotary servo motor is 60%-100% of the rated torque.

[0017] As a further improvement of the present invention, in step S1, the bottom mold assembly has an intermediate position 1-5mm lower than the welding position during the rising process, the second driving assembly drives the bottom mold assembly to rise to the intermediate position at a speed of 200-300mm / s, and the second driving assembly drives the bottom mold assembly to rise from the intermediate position to the welding position at a speed of 20-100mm / s.

[0018] As a further improvement of the present invention, the ultrasonic welding machine further includes a current feedback loop for detecting the output current of the second driving component. In step S3, the current feedback loop feeds back the output current of the second driving component.

[0019] As a further improvement of the present invention, the ultrasonic welding machine includes a drive motor, a connecting guide rail connecting the drive motor and the bottom mold assembly, and a locking mechanism for locking the connecting guide rail. In step S1, when the second drive assembly drives the bottom mold assembly to rise to the welding position, the locking mechanism locks the connecting guide rail.

[0020] As a further improvement of the present invention, there is a step S41 between step S4 and step S5, in which the locking mechanism releases the connecting guide rail.

[0021] As a further improvement of the present invention, in steps S1 and S3, the lifting force provided by the drive motor is F1, the locking force provided by the locking mechanism is F2, and the upward driving force of the bottom mold assembly is F=F1+F2.

[0022] The beneficial effects of this invention are as follows: The ultrasonic welding method provided by this invention optimizes the welding process by introducing a precise physical model based on the law of conservation of energy. Its core beneficial effect is to transform the traditional passive support into active and adaptive force control, ensuring that the sinking height of the bottom mold after impact and the height change during welding are small, thereby effectively avoiding the tensile cracking of the welded material due to the shrinkage of the bottom mold, and significantly improving the stability and reliability of the welding quality. Attached Figure Description

[0023] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0024] Figure 1 This is a structural diagram of an ultrasonic welding machine;

[0025] Figure 2 This is a flowchart of the ultrasonic welding method of the present invention. Detailed Implementation

[0026] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., 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 the invention and for 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 limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0028] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; 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; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Furthermore, the technical features involved in the different embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0029] like Figure 1 As shown, the ultrasonic welding method of the present invention uses an ultrasonic welding machine 100 for welding. The ultrasonic welding machine 100 includes a welding head assembly 1, a first driving assembly 2 for driving the welding head assembly 1 to move up and down, a bottom mold assembly 3 disposed below the welding head assembly 1, and a second driving assembly 4 for driving the bottom mold assembly 3 to move up and down.

[0030] like Figure 2 As shown, the ultrasonic welding method includes the following steps:

[0031] S1: When welding material is placed on the bottom mold assembly 3 and the second drive assembly 4 drives the bottom mold assembly 3 to rise to the welding position, the equivalent stiffness of the bottom mold assembly 3 is k.

[0032] S2: The first driving component 2 drives the welding head component 1 to move downward until the welding head component 1 contacts the welding material. The equivalent mass of the welding head component is m, the downward speed is v, and the deformation and compression target value of the bottom mold component 3 is s.

[0033] S3: Perform ultrasonic welding. The upward driving force of the bottom mold assembly 3 is F, which is provided by the second driving assembly 4. F=(m×v²) / (2×s)-(k×s) / 2;

[0034] S4: The first driving component 2 drives the welding head component 1 to move upward;

[0035] S5: The second drive component 4 drives the bottom mold component 3 to descend.

[0036] The calculation method of F is as follows: the energy of the welding head assembly 1 is conserved at the moment of impact, which conforms to Ek=F×s+Ep, where Ek is the kinetic energy carried by the welding head assembly 1. The bottom mold assembly 3 is compressed to a certain extent. Assuming that the bottom mold assembly 3 is a spring with stiffness k, the potential energy of the bottom mold assembly 3 after compression is Ep. The kinetic energy Ek carried by the welding head assembly 1 is equal to the work done by the second driving assembly 4 plus the elastic potential energy stored in the bottom mold assembly 3.

[0037] Ep = 0.5 × k × s², Ek = 0.5 × m × v², 0.5 × m × v² = F × s + 0.5 × k × s², therefore F = (m × v²) / (2 × s) - (k × s) / 2.

[0038] k is the equivalent stiffness, a key performance indicator of the entire mechanical system. High stiffness k can significantly reduce the requirements for the output force F of the second drive component 4 and improve system stability. In this embodiment, an additional margin is needed to ensure that the sinking height of the bottom mold component 3 after impact is less than 0.02mm, and the height change of the bottom mold component 3 during welding is less than 0.005mm. Therefore, the target value for deformation compression of the bottom mold component 3 can be set to 0.02mm.

[0039] The bottom mold assembly 3 may include the bottom mold and the support structure connecting the bottom mold, or it may include the lower welding head assembly.

[0040] The ultrasonic welding method provided by this invention, by introducing an active control strategy based on a physical model, greatly improves the positional stability of the bottom mold during the welding process compared with traditional welding methods, thereby directly improving welding quality and production efficiency.

[0041] During the welding stage, the second drive component 4 actively provides a precisely calculated upward force F, enabling the bottom mold component 3 to form a dynamic and highly rigid support system. This effectively resists the impact of the welding head component 1 pressing down, effectively compensates for the retraction of the bottom mold component 3 under impact, and effectively avoids the problem of the welding material being stretched, torn, or cracked due to the displacement of the bottom mold, greatly reducing the product defect rate.

[0042] The ultrasonic welding method of the present invention comprehensively considers the impact kinetic energy of the welding head assembly 1 and the mechanical stiffness (k) and target deformation (s) of the bottom mold system, so that the upper force can accurately offset the impact and maintain the system deformation within the expected range. The present invention provides an active and continuous force control that can automatically eliminate transmission chain gaps, adapt to different impact energies, and ensure that the height change of the bottom mold assembly 3 during the welding process is minimal and the position is extremely stable.

[0043] The ultrasonic welding machine 100 also includes a limiting block 5, which abuts against the limiting block 5 when the bottom mold assembly 3 rises to the welding position in step S1. When the bottom mold assembly 3 rises to the welding position, the second drive assembly 4 provides a continuous upward driving force to eliminate mechanical clearance.

[0044] As an embodiment of the present invention, the second drive component 4 is a linear servo motor, which is connected to the bottom mold component 3. This direct drive structure eliminates the intermediate transmission mechanisms such as ball screws and synchronous belts required by traditional rotary servo motors, achieving zero transmission connection between the power source and the bottom mold component 3. This design fundamentally eliminates the inherent defects such as backlash and elastic deformation caused by intermediate transmission links, greatly improving the equivalent stiffness of the bottom mold component 3, making it less deformed and more stable in position when subjected to the impact of the welding head component 1. Secondly, the linear servo motor has the natural advantages of high response and high acceleration, which can drive the bottom mold component 3 to complete the rising and falling movements at extremely high speeds, significantly improving the equipment cycle time. During the welding stage, the linear servo motor can output precise and continuous upward force (F) without delay, forming a gapless and highly rigid dynamic support system, thereby ensuring that the impact kinetic energy of the downward pressure of the welding head component 1 is actively and effectively offset, ultimately perfectly solving the core technical problem of cracking of the welded material due to bottom mold displacement, while taking into account the requirements of high speed and high stability.

[0045] In another embodiment of the present invention, the second drive component 4 is a rotary servo motor and a transmission mechanism connecting the rotary servo motor and the bottom mold component 3. This embodiment makes full use of the mature, cost-effective, and widely available rotary servo motor, which helps control the overall machine cost and improve maintenance convenience. Secondly, through the deceleration and force amplification effect of the transmission mechanism, a standard servo motor with relatively small torque and high speed can be used to output a large thrust that meets welding requirements, achieving the best cost performance of the system. Although the introduction of the transmission mechanism may introduce a small mechanical backlash, the core control method of the present invention, which involves running the servo motor in torque mode during the welding stage and applying constant force to the hard limit, can actively eliminate this backlash, keeping the entire transmission chain taut at all times, thereby transforming the potential disadvantage into a stable and reliable rigid support. This solution is particularly suitable for production line environments where the overall machine installation height is limited, demonstrating excellent engineering adaptability and comprehensive advantages.

[0046] In embodiments where the second drive component 4 includes a rotary servo motor, the operating torque of the rotary servo motor is 80%-100% of its rated torque. Because the rotary servo motor needs to maintain torque output during welding to avoid overheating, it should not exceed its rated torque, but should be as high as possible. This design, on the one hand, sets the torque within a high percentage range of the rated value, ensuring that the servo motor can provide sufficiently strong upward force to effectively eliminate transmission backlash and resist the downward impact of the welding head assembly 1, which is the foundation for achieving high rigidity and stable welding. On the other hand, deliberately avoiding the aggressive strategy of exceeding the rated torque is to prevent the motor from overheating due to prolonged overload during continuous welding cycles, thereby ensuring the motor's service life and operational reliability, and avoiding production stoppages or equipment damage caused by overheat protection.

[0047] In the embodiment where the second drive component 4 includes a rotary servo motor, in step S1, when the second drive component 4 drives the bottom mold component 3 to rise to the welding position, the torque of the rotary servo motor is 150%-250% of the rated torque. In step S3, during welding, the torque of the rotary servo motor is 60%-100% of the rated torque. This embodiment further employs a phased dynamic torque control strategy. During the rising phase, a powerful torque far exceeding the rated value is applied briefly, generating a huge instantaneous thrust. This causes the bottom mold component 3 and its limiting block 5 to rapidly impact and press against the hard limit with extremely high acceleration and force. This action can instantly overcome the static friction and inertia of the entire transmission mechanism, completely eliminating all mechanical gaps in the most drastic way, and establishing an extremely stable initial reference for welding. Subsequently, by adjusting the torque back to a safe range below the rated value during the welding stage, it is ensured that the servo motor will not overheat or be damaged due to prolonged overload during the entire welding cycle, which requires continuous torque output. This balances the two key requirements of "instantaneous maximum output to establish rigidity" and "long-term stable operation to ensure reliability," thereby achieving optimal welding position stability without sacrificing equipment lifespan and stability.

[0048] In one embodiment of the present invention, during step S1, the bottom mold assembly 3 has an intermediate position 1-5mm lower than the welding position during its ascent. The second drive assembly 4 drives the bottom mold assembly 3 to rise to the intermediate position at a speed of 200-300mm / s, and drives the bottom mold assembly 3 from the intermediate position to the welding position at a speed of 20-100mm / s. In this embodiment, the ascent process of the bottom mold assembly 3 in step S1 is precisely divided into two stages, cleverly balancing the pursuit of high production cycle time with the need to protect the mechanical structure of the equipment. The high-speed stage minimizes the idle travel time of the bottom mold, directly improving the overall operating efficiency and cycle time of the equipment; while switching to the low-speed stage near the end point greatly reduces the impact force generated by the bottom mold assembly 3 when it contacts the mechanical hard limit, effectively preventing the limit block 5 or related mechanical structures from breaking, deforming, or prematurely wearing due to severe impact, thus improving the equipment's lifespan and reliability.

[0049] The ultrasonic welding machine 100 also includes a current feedback loop for detecting the output current of the second drive component 4. In step S3, the current feedback loop provides feedback on the output current of the second drive component 4. The feedback signal from the current feedback loop serves as the control basis for the second drive component 4, ensuring that the upward force can accurately follow the set value, thereby reliably transforming the theoretical force control model into physical reality. This direct electrical signal feedback and adjustment has an extremely fast response speed, suppressing the position fluctuation of the bottom mold component 3 within a very small range.

[0050] The ultrasonic welding machine 100 includes a drive motor, a connecting rail connecting the drive motor and the bottom mold assembly 3, and a locking mechanism for locking the connecting rail. In step S1, when the second drive assembly 4 drives the bottom mold assembly 3 to rise to the welding position, the locking mechanism locks the connecting rail.

[0051] Between steps S4 and S5, there is step S41, where the locking mechanism releases the connecting guide rail.

[0052] In steps S1 and S3, the lifting force provided by the drive motor is F1, the locking force provided by the locking mechanism is F2, and the upward driving force of the bottom mold assembly 3 is F = F1 + F2.

[0053] In a preferred embodiment of the present invention, the ultrasonic welding machine 100 further integrates a mechanical locking scheme to enhance rigidity. The core mechanical relationship of this scheme is as follows: during the welding stage, the lifting force F1 provided by the drive motor and the locking force F2 provided by the clamping mechanism work together to form a total resistance force F to resist the impact of the welding head assembly 1. The intervention of the clamping mechanism partially diverts the impact load that was originally borne solely by the drive motor to the robust mechanical structure, thereby greatly enhancing the rigidity of the entire bottom mold system at the moment of welding and effectively suppressing minor retraction. At the same time, this design reduces the requirement for the continuous output limit torque of the drive motor, which helps prevent motor overheating and improves system reliability. The clear locking and releasing sequence ensures the safety and smoothness of the operation process, avoids mechanical interference, and guarantees the efficient cycle time of the equipment while pursuing ultimate stability.

[0054] The ultrasonic welding method provided by this invention optimizes the welding process by introducing a precise physical model based on the law of conservation of energy. Its core advantage lies in transforming traditional passive support into active, adaptive force control. In the workflow, after the bottom mold rises to the welding position, the second drive component 4 does not stop but continues to push upwards with a calculated, precise force F. This crucial step actively eliminates mechanical backlash in the transmission chain, forming a dynamic, high-rigidity system. This method effectively resists the downward impact of the welding head component 1, ensuring minimal changes in the bottom mold's height after impact and during welding. This effectively prevents the welded material from tearing due to bottom mold retraction, significantly improving the stability and reliability of the welding quality.

[0055] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0056] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. An ultrasonic welding method, wherein welding is performed using an ultrasonic welding machine, the ultrasonic welding machine comprising a welding head assembly, a first driving assembly for driving the welding head assembly to move up and down, a bottom mold assembly disposed below the welding head assembly, and a second driving assembly for driving the bottom mold assembly to move up and down, characterized in that: The ultrasonic welding method includes the following steps: S1: When welding materials are placed on the bottom mold assembly and the second drive assembly drives the bottom mold assembly to rise to the welding position, the equivalent stiffness of the bottom mold assembly is k. S2: The first drive component drives the welding head component to move downward until the welding head component contacts the welding material. The equivalent mass of the welding head component is m, the downward movement speed is v, and the deformation and compression target value of the bottom mold component is s. S3: Perform ultrasonic welding. The upward driving force of the bottom mold assembly is F, which is provided by the second driving assembly. F=(m×v²) / (2×s)-(k×s) / 2; S4: The first drive component drives the welding head assembly to move upward; S5: The second drive component drives the bottom mold component to descend.

2. The ultrasonic welding method according to claim 1, characterized in that: The second drive component is a linear servo motor, which is connected to the bottom mold component.

3. The ultrasonic welding method according to claim 1, characterized in that: The second drive component is a rotary servo motor and a transmission mechanism connecting the rotary servo motor and the bottom mold component.

4. The ultrasonic welding method according to claim 3, characterized in that: The rotary servo motor operates at 80%-100% of its rated torque.

5. The ultrasonic welding method according to claim 3, characterized in that: In step S1, when the second drive component drives the bottom mold component to rise to the welding position, the torque of the rotary servo motor is 150%-250% of the rated torque. In step S3, when welding, the torque of the rotary servo motor is 60%-100% of the rated torque.

6. The ultrasonic welding method according to claim 1, characterized in that: In step S1, the bottom mold assembly has an intermediate position 1-5mm below the welding position during the rising process. The second drive assembly drives the bottom mold assembly to rise to the intermediate position at a speed of 200-300mm / s, and the second drive assembly drives the bottom mold assembly to rise from the intermediate position to the welding position at a speed of 20-100mm / s.

7. The ultrasonic welding method according to claim 1, characterized in that: The ultrasonic welding machine also includes a current feedback loop for detecting the output current of the second drive component. In step S3, the current feedback loop feeds back the output current of the second drive component.

8. The ultrasonic welding method according to claim 1, characterized in that: The ultrasonic welding machine includes a drive motor, a connecting guide rail connecting the drive motor and the bottom mold assembly, and a locking mechanism for locking the connecting guide rail. In step S1, when the second drive assembly drives the bottom mold assembly to rise to the welding position, the locking mechanism locks the connecting guide rail.

9. The ultrasonic welding method according to claim 8, characterized in that: Between steps S4 and S5, there is step S41, where the locking mechanism releases the connecting guide rail.

10. The ultrasonic welding method according to claim 8, characterized in that: In steps S1 and S3, the lifting force provided by the drive motor is F1, the locking force provided by the locking mechanism is F2, and the upward driving force of the bottom mold assembly is F = F1 + F2.

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