A method for controlling the stability of droplet transfer state during oscillating arc welding

Abstract

This invention discloses a method for stabilizing the droplet transition state during oscillating arc welding. This method analyzes the oscillation function equation of the welding wire tip's trajectory and the spatial position of the substrate to obtain a time-varying function of the minimum distance between the welding wire tip and the substrate. Based on the characteristics of different droplet transition states during welding, a system optimization method is proposed to maintain a stable droplet transition state during welding, avoiding unstable droplet transition modes. The key point of the optimization scheme is that the distance from the welding wire tip to the two substrates is related to the welding torch oscillation at different positions. By adjusting the wire feed speed and the welding torch spatial position at different oscillation positions, the minimum distance between the welding wire tip and the two substrates remains relatively stable at any oscillation position, i.e., maintaining the peak distance for efficient droplet transition. By adjusting the minimum distance in real time, the droplet transition frequency is kept within a high range, preventing the generation of large droplets, reducing particle spatter, and improving the forming quality.

Description

Technical Field

[0001] This invention relates to a method for controlling the stability of the droplet transition state during oscillating arc welding, belonging to the field of welding automation technology. Background Technology

[0002] Oscillating arc welding is a highly efficient and high-quality automated welding method widely used in the production of large structural components such as ships, gantry cranes, railways, pressure vessels, and containers. However, arc welding consumes a significant amount of energy, and due to careless operation, it can lead to various problems such as inadequate weld filling, welding defects, and porosity, significantly reducing production and welding efficiency. Controlling the droplet transfer mode during welding can effectively reduce spatter, improve weld quality, save materials, and reduce production steps. Methods for changing the droplet transfer mode include altering parameters such as wire feed speed and the spatial position of the welding torch.

[0003] Automated welding reduces the impact of human factors on welding quality and improves the consistency of production quality. Currently, domestic research on reducing losses in automated welding mainly focuses on welding processes and the thermodynamic properties of materials. There is relatively little research on the control of droplet transfer state changes in oscillating arc welding. However, the droplet transfer state directly determines welding quality, production efficiency, and energy conversion. Controlling the stability of the droplet transfer mode is particularly important in oscillating arc welding. Summary of the Invention

[0004] The purpose of this invention is to provide a method for controlling the stable droplet transfer state during oscillating arc welding, which reduces particle spatter, improves weld formation quality, saves materials, and has a wide range of applications.

[0005] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0006] The method is characterized by: obtaining the motion trajectory function of the welding wire tip through parameters such as the spatial coordinates of the substrate and the oscillating head, the frequency and speed of the arc oscillation, and the extension of the welding torch and the welding wire. Based on this, the theoretical value of the minimum distance between the welding wire tip and the substrate when the welding torch oscillates can be calculated, and then the time-varying function of the minimum distance between the welding wire tip and the substrate can be obtained, and the numerical value of the droplet transfer mode at this time can be established. At the same time, image information of the welding torch oscillating to different positions is captured by a vision sensor, and after image processing, another set of captured values ​​of the minimum distance and the droplet transfer mode is obtained. The two sets of data, theoretical value and captured value, are compared and analyzed to obtain the initial distance and a more accurate minimum distance between the welding wire tip and the substrate, and to determine the variation law of the minimum distance value between the welding wire tip and the substrate. The method includes the following steps: S1 Based on the motion trajectory function of the welding wire tip, the minimum distance value between the welding wire tip and the substrate when the welding torch oscillates and the variation law of the minimum distance value are calculated and determined, the time-varying function of the minimum distance between the welding wire tip and the substrate is obtained, and the mapping relationship between the minimum distance value and the droplet transfer mode is established. S2 The optimal droplet transfer mode and the optimal minimum distance value are determined. During S3 welding, the minimum distance between the welding wire tip and the substrate is changed during the oscillation of the welding torch, thereby altering the droplet transfer mode. This maintains a stable and efficient optimal droplet transfer mode, reducing metal particle spatter, improving weld formation, and saving materials.

[0007] The working principle of this method is as follows: During the automatic welding process of an oscillating arc, the changing trend of the droplet transfer frequency is opposite to the changing trend of the minimum distance between the welding wire tip and the substrate. A higher droplet transfer frequency corresponds to a smaller minimum distance between the welding wire tip and the substrate, resulting in a more stable droplet transfer state. Furthermore, when the minimum distances between the welding wire tip and the substrate are similar, the droplet transfer frequencies are also similar. See details... Figure 3 During oscillating welding, as the welding wire tip oscillates from point A to point C, the minimum distance between the wire tip and the substrate continuously changes, increasing from d2 to d3, then equalizing with d4, and finally decreasing from d3 to d5. The droplet transfer frequency first decreases and then increases, and the droplet transfer state changes accordingly. When the welding torch oscillates to its maximum angle, i.e., at points A and C, the minimum distances d2 and d5 between the welding wire tip and the two substrates reach their minimum values. At this point, the droplet transfer frequency is highest, and the droplet state is stable. Conversely, when the welding torch oscillates to the angle bisector, i.e., at point B, the minimum distance d3 between the welding wire tip and the substrate reaches its maximum peak value, the droplet transfer frequency is lowest, and the droplet state is unstable, exhibiting large droplet transfer. Therefore, the difference between the initial distance and the optimal minimum distance between the welding wire tip and the substrate can be calculated to obtain the optimal adjustment amount for the distance between the welding wire tip and the substrate. This minimum distance maintains the efficient droplet transfer state and ensures a stable droplet transfer mode.

[0008] See Figure 2It can be seen that the distances between the welding wire tip and the two substrates at the angle bisector are d1 and d2, respectively, while the distances at the maximum oscillation angle are d3 and d4. The minimum distance d4 between the welding wire tip and the substrate at the maximum oscillation angle is the optimal minimum distance, where the droplet transition is optimal, the droplet diameter is small, and no spatter occurs. See details. Figure 1 During welding, the spatial position O(x, y, z) of the oscillating head is determined using the substrate as the spatial coordinate axis. After determining the spatial positions of the substrate and the oscillating head, the oscillation function of the welding torch is obtained based on the length L of the welding torch, the oscillation speed v, and the frequency f. To ensure that the welding wire tip maintains the optimal minimum distance from the substrate, the controller needs to determine the wire feed speed achieved at different oscillation positions based on known data during the welding process. The welding speed is adjusted during the welding torch oscillation to maintain the distance between the welding wire tip and the substrate at d4. At this point, the droplet transition remains stable and efficient during welding, metal spatter is reduced, and the droplet diameter remains at an appropriate size, preventing the formation of large droplets.

[0009] The control method, based on the relationship between the frequency and mode of droplet transfer and the distance from the welding wire tip to the two substrates, and the different positions of the welding torch oscillation, creatively employs the following approach after obtaining the optimal adjustment parameters: While the welding torch oscillates, the wire feed speed and the forward / backward movement of the welding torch are simultaneously adjusted to ensure that the minimum distance between the welding wire tip and the substrate is always at the optimal minimum distance difference, thus avoiding large droplet transfer. By adjusting the wire feed speed and the spatial position of the welding torch during welding, the minimum distance between the welding wire tip and the substrate is kept constant, thereby obtaining a stable droplet transfer mode. When controlling the droplet transfer mode and frequency of the oscillating arc automatic welding, modifying the wire feed speed according to the minimum distance ensures a stable and efficient droplet transfer mode. By changing the wire feed speed as the welding torch oscillates to different positions to keep the minimum distance constant, the droplet transfer remains stable and at a high frequency throughout the welding process, reducing particle spatter. The adjustment method is to reduce the minimum distance between the end of the welding wire and the substrate by increasing the wire feed speed and moving the welding gun forward during the process of swinging the welding gun from the maximum height to the angle bisector. When swinging from the angle bisector to the maximum angle, the wire feed speed should be reduced to prevent the end of the welding wire from directly contacting the substrate.

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

[0011] 1) This invention enables the molten droplet transfer state to remain stable during oscillating arc welding. It mainly controls the minimum distance between the welding wire tip and the workpiece by changing the real-time wire feed speed. This is more convenient and easier to operate than directly changing the welding torch position. It can ensure that the threshold of the welding wire tip extension is the same as the threshold of the wire feed speed. Moreover, compared with changing other conditions to achieve this purpose, it is more suitable for the actual production of automated oscillating arc welding in terms of conditions and ease of operation.

[0012] 2) This invention plays a significant role in improving production efficiency in automated welding. This method maintains the droplet transition in a jet-like state, reducing large droplet splashing during the droplet process, appropriately enhancing the stability of sidewall welding, and facilitating sidewall fusion. Simultaneously, this method can improve the weld formation rate, maximize the utilization of welding materials, maintain better welding results, improve energy efficiency, and save costs. Attached Figure Description

[0013] Figure 1 This is a parameter diagram of the device of the present invention.

[0014] Figure 2 This is a diagram illustrating the operation of the device of the present invention.

[0015] Figure 3 This is a schematic diagram of the working principle of the present invention.

[0016] Figure 4 This is a schematic diagram of the system optimization design of the present invention.

[0017] Figure 5 This is a comparison diagram of the optimization of the present invention. Detailed Implementation

[0018] To better illustrate the technical solution and beneficial effects of the invention, the invention will be further described in detail below with reference to the accompanying drawings and implementation examples.

[0019] See Figure 4 This is a schematic diagram of the system optimization design of the present invention. Before welding the workpiece, image information of the welding torch swinging to different positions is first obtained by taking pictures. After image processing, the minimum distance D1 and the droplet transfer mode M1 at this time are obtained. At the same time, the theoretical values ​​of the minimum distance D2 and the droplet transfer mode M2 ​​are calculated based on the motion trajectory function and welding parameters. The pictures and theoretical values ​​are analyzed and compared to obtain the initial distance between the welding wire tip and the substrate and the time-varying function of the minimum distance between the welding wire tip and the substrate. The difference between the initial distance and the optimal minimum distance value is calculated, and then the optimal adjustment amount of the distance between the welding wire tip and the substrate is obtained. After obtaining the optimal adjustment value, a wire feeding adjustment function is obtained by establishing the relationship between the droplet transfer mode and the wire feed speed. The computer calculates the wire feed speed when the welding torch oscillates to different position parameters based on this function. The wire feed speed parameters are then sent to the controller. After the welding torch is adjusted to the required wire feed speed, the wire tip is ensured not to directly contact the workpiece. This ensures that the optimal minimum distance between the wire tip and the substrate—that is, the peak distance for efficient droplet transfer—remains constant, thus maintaining the efficient droplet transfer mode, reducing particle spatter, improving forming quality, and achieving optimized welding. For a detailed comparison of the optimization of the wire tip movement trajectory of the oscillating welding torch in this invention, please refer to [link to relevant documentation]. Figure 5 The welding torch oscillation is an arc motion with the center (swing head) as the fixed point. The distance between the welding torch and the sidewalls of the two plates is related to the arc motion function of the oscillation. By adjusting the minimum distance between the end of the welding wire and the substrate, and by changing the wire feed speed, the maximum peak value of the distance between the end of the welding wire and the two substrates when the welding torch oscillates at the angle bisector is the same as the minimum value of the distance between the end of the welding wire and the two substrates when the oscillation angle of the welding torch reaches its maximum. In this way, the droplet transfer frequency can be maximized, and the droplet transfer state during welding can be changed from large droplet transfer with spatter to small droplet transfer with no spatter.

[0020] Because this invention can adjust the minimum distance between the end of the welding wire and the workpiece by changing the wire feeding speed, thereby controlling the stable droplet transfer state during oscillating arc welding, it has a wide range of applications.

[0021] Implementation Case 1: Reduce metal spatter during welding and save materials.

[0022] Applying this invention to the oscillating arc welding process, a wire feed speed adjustment function is established based on the optimal adjustment of the distance between the welding wire tip and the substrate. The computer calculates the required wire feed speed for different spatial position parameters of the welding torch based on this function, and sends the speed parameters to the controller to adjust the wire feed speed when the welding torch reaches the target spatial position. By adjusting the distance between the welding wire tip and the substrate, the minimum distance between the welding wire tip and the substrate—that is, the peak distance for efficient droplet transition—can be maintained constant, keeping the droplet transition frequency within a high range, maintaining a stable droplet transition state, avoiding large droplet transitions, reducing molten metal particle spatter, further reducing energy consumption, minimizing the occurrence of particulate matter during welding, simplifying the cleaning process, and saving materials.

[0023] Implementation Case 2: Improving the quality of weld formation.

[0024] This invention improves welding precision and thus increases welding speed by controlling the stability of the molten droplet transition state during oscillating arc welding. Under constant conditions, increasing welding speed leads to a decrease in welding heat input, resulting in a reduction in both weld width and depth. Since the amount of weld metal deposited per unit length of weld is inversely proportional to the welding speed, it also leads to a decrease in weld reinforcement. Therefore, the method of controlling the stability of the molten droplet transition state during oscillating arc welding improves the weld formation quality.

[0025] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. For those skilled in the art, the present invention can have various modifications and variations. Any changes or substitutions, modifications, improvements, or combinations that can be conceived within the scope of the technology disclosed in the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for controlling the stability of the droplet transfer state during automatic oscillating arc welding, characterized in that, The process includes the following steps: S1. Based on the motion trajectory function of the welding wire tip, calculate and determine the minimum distance between the welding wire tip and the substrate during the welding torch oscillation, as well as the variation law of the minimum distance, to obtain the time-varying function of the minimum distance between the welding wire tip and the substrate, and establish a mapping relationship between the minimum distance and the droplet transfer mode; S2. Establish the optimal droplet transfer mode and the optimal minimum distance; S3. During welding, by changing the minimum distance between the welding wire tip and the substrate during the welding torch oscillation, the droplet transfer mode is changed to maintain a stable and efficient optimal droplet transfer mode, thereby reducing metal particle spatter, improving weld formation, and saving materials; The minimum distance refers to the vertical distance between the welding wire tip and each of the two substrates during the welding torch oscillation, and the two vertical distances are compared, with the smaller value being the minimum distance between the welding wire tip and the substrate.

2. The method for controlling the stable droplet transition state during automatic welding with an oscillating arc according to claim 1, characterized in that: The motion trajectory function is obtained by the swinging method of the welding torch and the spatial relationship between the substrate and the welding torch.

3. A method for stabilizing the droplet transfer state during automatic welding with an oscillating arc, characterized in that: Image information of the welding torch swinging to different positions is captured by a vision sensor. After image processing, the captured values ​​of the minimum distance D1 and the droplet transfer mode M1 are obtained. At the same time, the theoretical values ​​of the minimum distance D2 and the droplet transfer mode M2 ​​are obtained according to the motion trajectory function and welding parameters. The captured values ​​and theoretical values ​​are analyzed and compared to obtain the time-varying function of the initial distance between the welding wire tip and the substrate and the minimum distance between the welding wire tip and the substrate. The difference between the initial distance and the optimal minimum distance value is calculated to obtain the optimal adjustment amount of the distance between the welding wire tip and the substrate. The minimum distance value refers to the vertical distance between the welding wire tip and each of the two substrates when the welding torch swings. The two vertical distance values ​​are compared, and the smaller value is the minimum distance between the welding wire tip and the substrate.

4. The method for controlling the stability of the droplet transition state during automatic welding with an oscillating arc according to claim 3, characterized in that: When the welding torch swings to different positions, after obtaining the optimal adjustment amount, the minimum distance between the end of the welding wire and the substrate is adjusted by controlling the wire feed speed and the spatial position of the welding torch. This ensures that the maximum peak value of the distance between the end of the welding wire and the two substrates when the welding torch swings to the angle bisector is the same as the minimum value of the distance between the end of the welding wire and the two substrates when the swing angle of the welding torch reaches its maximum, thus maintaining a stable droplet transfer state.

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