A multi-machine collaborative welding system and method

Abstract

This invention provides a multi-robot collaborative welding system and method. The system enables multiple robots to collaboratively complete welding at locations such as circumferential welds and end-to-end welds. The optimized arc initiation and termination method solves quality problems in bogie frame tube-plate corner weld joints, such as incomplete fusion and appearance issues like hump and groove. Improved residual temperature control during collaborative welding replaces flame preheating, effectively suppressing arc-initiation welding defects at cold joints. This enables large-scale multi-robot collaborative welding, reduced manual rework, shorter product production cycles, and improved production efficiency in the bogie frame welding process.

Description

Technical Field

[0001] This invention relates to a multi-machine collaborative welding system and method, specifically disclosing a multi-machine collaborative welding system and method based on component ring surfacing welding. Background Technology

[0002] Existing technologies contain various components that require welding, and many of these components require circumferential welding on both the inner and outer sides to meet usage requirements. For example, most bogie components in existing rail vehicles require welding of both the outer and inner rings. However, in current welding processes, robots can only weld the outer ring weld of the tube-plate, resulting in insufficient accessibility for welding the inner ring of the bogie. This leads to low equipment utilization and overall automation of the process. Furthermore, multi-layer welded joints are prone to quality defects such as internal lack of fusion and external hump and groove, increasing manual rework time. These problems seriously affect the production cycle and efficiency of bogie frames. Summary of the Invention

[0003] In order to solve the technical problems existing in the prior art, the present invention discloses a multi-machine collaborative welding system and method based on frame ring surfacing welding.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] In a first aspect, the present invention provides a multi-machine collaborative welding system based on frame-based annular surfacing welding, comprising a first truss welding robot, a second truss welding robot, a first positioner, a second positioner, and a collaborative welding robot; the first truss welding robot is installed on one side of the first positioner, the second truss welding robot is installed on one side of the second positioner, and the collaborative welding robot is located on the other side of the first and second positioners, and is mounted on a guide rail, capable of moving along the guide rail to the first or second positioner to cooperate with the first and second truss welding robots to achieve welding; the first and second truss welding robots are capable of moving in the XYZ three-axis directions.

[0006] The first truss welding robot and the second truss welding robot mentioned above are used to weld the outer ring and one half of the inner ring of the component to be welded, while the collaborative welding robot is used to weld the other half of the inner ring of the component to be welded.

[0007] As a further technical solution, an aerial conveying device is also provided above the first positioner and the second positioner.

[0008] Secondly, based on the aforementioned multi-machine collaborative welding system for frame-based annular surfacing welding, the present invention also provides a welding method, as follows:

[0009] The first frame to be welded is transported to the first workstation and fixed. The first truss robot welds the outer ring weld of the first frame to be welded. After completion, it sends a signal to the collaborative welding robot to complete the inner ring overlay weld.

[0010] Due to production cycle intervals, the second frame to be welded arrives at the second workstation later than the first frame to be welded. The second gantry robot welds the outer ring weld of the second frame to be welded. After completion, it sends a signal to call the outer collaborative welding robot. If the outer collaborative welding robot has completed the welding task at the first workstation and returned to the zero position, the call is successful and the inner ring collaborative welding at the second workstation begins. If the welding task at the first workstation has not been completed, it continues to wait until it is completed before starting the welding at the second workstation. The order of the two sides can also be reversed.

[0011] As a further technical solution, after the first truss robot or the second truss robot successfully calls the collaborative welding robot, it begins welding the inner ring. The first truss robot or the second truss robot first welds one side of the inner ring semicircle, and after completion, sends an instruction to the outer collaborative welding robot. The outer collaborative welding robot receives the instruction and welds the other side of the inner ring semicircle of that layer, connecting the two ends. After completion, it sends a completion instruction to the first truss robot or the second truss robot, and after confirmation, continues welding the next layer.

[0012] As a further technical solution, after welding 3-4 layers, the collaborative welding robot returns to the zero position, the positioner reverses ±90°, and the two devices communicate with each other to continue welding until the inner ring weld filling layer and the cover layer of the structure to be welded are completed.

[0013] As a further technical solution, when the first truss robot or the second truss robot welds the outer ring of the frame separately, a welding torch nozzle coordinate system is established at the arc initiation point, with the TCP movement direction as the X-axis and the welding wire direction as the Z-axis; the welding torch nozzle at the arc initiation point rotates along the Y-axis at a certain angle θy to initiate the arc in a pulling welding posture, and after the arc initiation, the welding edge changes the angle along the Y-axis until θy≈0°, and 85%-90% of the entire weld is welded at θy≈0°. When the arc initiation point is 10-15mm away from the arc initiation point, the welding torch nozzle θy gradually changes to a negative angle for welding, and the arc termination point is 5-10mm past the arc initiation point. After reaching the arc termination point, the arc is terminated and the torch is lifted after a delay.

[0014] As a further technical solution, the TCP moving direction is either the direction of a straight weld or the tangent direction of a circular weld. The maximum value of the nozzle's arc θy is 20° to 25°, and the TCP moving distance is approximately 10-15 mm during the process of changing to θy≈0°.

[0015] As a further technical solution, the minimum arc termination θy of the welding torch nozzle is -10° to -5°. The arc termination completely remelts the metal at the root of the arc-starting joint. Under the dual action of gravity and protective gas blowing force, the molten metal is spread out flat, making it more even and aesthetically pleasing.

[0016] As a further technical solution, when the first truss robot or the second truss robot cooperates with the collaborative welding robot for welding, the first truss robot or the second truss robot establishes a welding torch nozzle coordinate system at the arc initiation point, with the TCP movement direction as the X-axis and the welding wire direction as the Z-axis. The welding torch nozzle at the arc initiation point rotates along the Y-axis at a certain angle θy to initiate the arc in a pulling welding posture. After the arc is initiated, the welding edge changes the angle along the Y-axis until θy≈0°. 85%-90% of the semi-circular weld seam is welded at θy≈0°. Before the arc termination point, the welding torch nozzle θy gradually changes to a negative angle for welding at a set position. After reaching the arc termination point, the arc is terminated and the torch is lifted after a delay.

[0017] After the first or second gantry robot completes its welding, the collaborative welding robot begins welding the semi-circular weld on the other side of the layer. Starting from the arc-ending point of the first or second gantry robot, the nozzle rotates at a certain angle θy along the Y-axis to initiate an arc in a pulling welding posture. After arc initiation, the welding process changes the angle along the Y-axis until θy≈0°. Welding 85%-90% of the semi-circular weld in this layer at θy≈0°, the welding torch nozzle gradually changes to a negative angle when it reaches the set position before the arc-starting point of the gantry robot. The arc-ending point crosses the set distance from the arc-starting point of the gantry robot, and the arc-ending point is delayed and the torch is lifted after reaching the arc-ending point.

[0018] As a further technical solution, the minimum arc termination θy of the welding torch nozzle is -10° to -5°.

[0019] The beneficial effects of this invention are as follows:

[0020] This invention achieves the welding of the inner and outer rings of a workpiece through the cooperation and coordination of a first truss welding robot, a second truss welding robot, and a collaborative welding robot. Specifically, the first and second truss welding robots are used to weld the outer ring and one half of the inner ring of the component to be welded, while the collaborative welding robot is used to weld the other half of the inner ring of the component. Furthermore, the first and second truss welding robots move in coordination with each other in the XYZ three-axis directions to achieve the welding of the component, thus expanding the automatic welding capability of the bogie frame ring welding.

[0021] Furthermore, when the first or second truss robot of the present invention welds the outer ring of the frame alone or cooperates with a collaborative welding machine to complete the inner ring welding, a welding torch nozzle coordinate system is established at the arc starting point, with the TCP movement direction as the X-axis and the welding wire direction as the Z-axis; the welding torch nozzle at the arc starting point rotates a certain angle θy along the Y-axis to initiate the arc in a pulling welding posture, and after arc initiation, the welding edge changes the angle along the Y-axis until θy≈0°, welding 85%-90% of the entire weld seam at θy≈0°, and the welding torch nozzle θy gradually changes to a negative angle 10-15mm before the arc starting point, welding, and the arc ending point is 5-10mm past the arc starting point, and the arc ending and torch lifting are delayed after reaching the arc ending point. This solves the problem of incomplete fusion defects that are prone to occur at the arc starting and ending joints of the pipe-plate corner joint ring weld, reduces manual operation and manual rework, and improves the automation rate and production efficiency of the frame production line. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the multi-machine collaborative welding system based on frame ring surfacing proposed in this invention;

[0023] Figure 2 This is a schematic diagram of the internal non-fusion and external hump of the arc convergence point in the existing technology;

[0024] Figure 3 This is a schematic diagram of the outer ring of the welding frame proposed in this invention;

[0025] Figure 4 This is a schematic diagram of the arc initiation angle of the welding wire disclosed in this invention;

[0026] Figure 5 This is a schematic diagram of the arc start and end joint of the welding method disclosed in this invention;

[0027] Figure 6 This is a schematic diagram of the post-weld effect of a component using this method. Figure 1 ;

[0028] Figure 7 This is a schematic diagram of the post-weld effect of a component using this method. Figure 2 ;

[0029] In the diagram: 1 First truss welding robot, 2 Second truss welding robot, 3 First positioner, 4 Second positioner, 5 Collaborative welding robot, 6 Track. Detailed Implementation

[0030] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0031] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, unless otherwise expressly indicated by the invention, the singular form is also intended to include the plural form. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0032] For ease of description, the words "up," "down," "left," and "right" appearing in this invention only indicate that they are consistent with the up, down, left, and right directions of the accompanying drawings themselves, and do not limit the structure. They are merely for the purpose of facilitating the description of this invention and simplifying the description, and do not indicate or imply that the device or component 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.

[0033] Terminology Explanation: In this embodiment, "inner ring" refers to the inner fillet weld of the crossbeam steel pipe and the side beam plate after they are inserted into each other.

[0034] In this embodiment, "outer ring" refers to the fillet weld on the outer side after the crossbeam steel pipe of the frame is inserted into the side beam plate;

[0035] In this embodiment, "TCP" refers to the robot's tool center point.

[0036] As described in the background section, the present invention addresses the shortcomings of existing technologies and proposes a multi-machine collaborative welding system and method based on frame ring welding to solve the aforementioned technical problems. This system expands the automatic welding capability of bogie frame ring welding, solves the problem of incomplete fusion defects that easily occur at the start and end joints of pipe-plate corner ring welds, reduces manual operations and rework, and improves the automation rate and production efficiency of the frame production line.

[0037] In a typical embodiment of the present invention, such as Figure 1As shown, this invention provides a multi-machine collaborative welding system based on frame-based annular surfacing welding, including two truss welding robots, a positioner, and a collaborative welding robot 5. The two truss welding robots include a first truss welding robot 1 and a second truss welding robot 2. The first truss welding robot 1 is installed above a first workstation, and the second truss welding robot 2 is installed above a second workstation. The collaborative welding robot 5 is positioned outside the first and second workstations, and is mounted on a track 6, allowing it to move along the track 6 to either the first or second workstation. It cooperates with the first and second truss welding robots to complete the welding work. A first positioner 3 is installed at the first workstation, and a second positioner 4 is installed at the second workstation. The component to be welded is hoisted onto the first and second positioners 3 and 4 via a high-altitude conveyor, and the first and second positioners 3 and 4 control the orientation change of the component to be welded. The first truss welding robot 1 can move in the XYZ three-axis directions, and the second truss welding robot 2 can also move in the XYZ three-axis directions.

[0038] The first truss welding robot 1 and the second truss welding robot mentioned above are used to weld the outer ring and one half of the inner ring of the component to be welded, while the collaborative welding robot 5 is used to weld the other half of the inner ring of the component to be welded.

[0039] Furthermore, an aerial conveying device is also provided above the first positioner 3 and the second positioner 4. In this embodiment, the aerial conveying device is an overhead crane, mainly used for hoisting the frame to be welded.

[0040] Furthermore, the frame to be welded is hoisted onto the first positioner 3 and the second positioner 4 by an overhead crane. Two gantry robots are installed on the gantry supported by their respective positioner columns and weld the outer ring of the frame, the north semicircle of the inner ring of the frame, and some accessories by moving in three directions (XYZ). A collaborative welding robot 5 and its guide rail are installed outside the first positioner 3 and the second positioner 4 and can move to weld the south semicircle of the inner ring of the frame above the first positioner 3 and the second positioner 4 respectively, and work together with the two gantry robots to complete the inner ring welding.

[0041] The first truss welding robot 1, the second truss welding robot 2, and the collaborative welding robot 5 mentioned above all use existing welding robots, therefore, they will not be described in detail here; and the first truss welding robot 1, the second truss welding robot 2, and the collaborative welding robot 5 are uniformly controlled by the control system to perform their respective actions. The specific implementation steps are as follows:

[0042] The first frame to be welded is transported to the first workstation and fixed. The first truss robot welds the outer ring weld of the first frame to be welded. After completion, the control system sends a signal to the collaborative welding robot 5 to complete the inner ring weld. (In this process, the first truss robot 1 mainly completes the welding of the outer ring and half of the inner ring, while the collaborative welding robot 5 completes the welding of the other half of the inner ring. The first truss robot 1 completes the outer ring welding first, and then the first truss robot and the collaborative welding robot 5 work together to complete the inner ring welding. The first truss robot 1 and the collaborative welding robot 5 do not weld simultaneously; instead, after the first truss robot 1 finishes welding half of the ring, the collaborative welding robot 5 then welds the other half.) Due to the production cycle interval, the second frame to be welded is transported to the second workstation and fixed later than the first frame to be welded. The second truss robot welds the outer ring weld of the second frame to be welded. After completion, the control system... The system sends a signal to call the outer collaborative welding robot 5. If the outer collaborative welding robot 5 completes the welding task at the first station and returns to the zero position, the call is successful and the inner ring collaborative welding at the second station begins. If the welding task at the first station is not completed, it continues to wait until it is completed before starting the welding of the second frame to be welded at the second station. The order of the two sides can be reversed. (In this process, the second truss robot 2 mainly completes the welding of half of the outer ring and the inner ring, while the collaborative welding robot 5 completes the welding of the other half of the inner ring. The second truss robot 2 completes the welding of the outer ring first, and then the second truss robot 2 and the collaborative welding robot 5 work together to complete the welding of the inner ring. During the inner ring welding process, the first truss robot and the collaborative welding robot 5 do not weld at the same time. Instead, after the first truss robot finishes welding half of the ring, the collaborative welding robot 5 then welds the other half of the ring.)

[0043] Furthermore, after the first truss robot 1 or the second truss robot 2 successfully calls the collaborative welding robot 5, the inner ring welding begins. The first truss robot 1 or the second truss robot 2 first welds the northern semicircle of the inner ring, and after completion, sends an instruction to the outer collaborative welding robot 5. Upon receiving the instruction, the outer collaborative welding robot 5 welds the remaining southern semicircle of the inner ring of that layer. The two are then joined end to end, and after completion, a completion instruction is sent to the first truss robot 1 or the second truss robot 2. After confirmation, the welding of the next layer continues.

[0044] Furthermore, after every 3-4 layers are welded, the collaborative welding robot returns to the zero position, and the first positioner 3 or the second positioner 4 reverses ±90°. After the two devices communicate with each other, welding continues until all the weld filling layers and cover layers of the inner ring of the frame are completed.

[0045] Furthermore, such as Figure 3 , Figure 4As shown, when the first gantry robot 1 or the second gantry robot 2 welds the outer ring of the frame alone, a welding torch nozzle coordinate system is established at the arc initiation point, with the TCP movement direction as the X-axis and the welding wire direction as the Z-axis. The welding torch nozzle at the arc initiation point rotates a certain angle θy along the Y-axis to assume a pulling welding posture (as shown in the attached figure). Figure 4 (As shown in the diagram, start the arc with left-hand welding). After starting the arc, change the angle along the Y-axis while welding until θy≈0°, and then (as shown in the attached diagram) maintain θy≈0°. Figure 4 (As shown without push-pull angle) Weld 85%-90% of the entire weld seam, and when reaching 10-15mm before the arc initiation point, the welding torch nozzle θy gradually changes to a negative angle (in a push welding posture, as shown in the attached figure). Figure 4 (As shown in the right weld), the arc termination point is 5-10mm beyond the arc termination point, and the arc termination torch is lifted after a 0.1s delay after reaching the arc termination point.

[0046] Furthermore, the first truss robot 1, the second truss robot 2, and the outer collaborative welding robot 5 collaboratively weld the inner ring of the frame, connecting the end-to-end welds of different passes on the same layer (as shown in the attached image). Figure 5 (The process of starting the arc again for different welds is shown above.) The arc-welding-arc termination process refers to the outer ring welding steps mentioned above. The "different passes in the same layer" mentioned here refers to the inner ring weld welded by the inner and outer robots in collaboration. Multiple layers need to be welded. For each layer, the truss robot welds the north half (1 pass), and the collaborative robot welds the south half (1 pass). This is explained as different passes, which is equivalent to two passes per layer.

[0047] Specifically, taking the welding of the first gantry robot 1 and the collaborative welding robot 5 as an example, the following is a detailed explanation: The first gantry robot 1 establishes a welding torch nozzle coordinate system at the arc initiation point, with the TCP movement direction as the X-axis and the welding wire direction as the Z-axis. At the arc initiation point, the welding torch nozzle rotates a certain angle θy along the Y-axis to initiate the arc in a pulling welding posture. After arc initiation, the welding edge changes the angle along the Y-axis until θy≈0° (e.g., ...). Figure 5 (Diagram of arc initiation for circumferential weld) Welding 85%-90% of the semicircular weld (located on the north side) with θy≈0°. 10-15mm before the arc termination point, the welding torch nozzle θy gradually changes to a negative angle (pushing welding posture). After a 0.1s delay at the arc termination point, the torch is lifted to terminate the weld. After the first gantry robot 1 completes welding, a welding command is sent to the collaborative welding robot 5. Upon receiving the command, welding begins on the other side of the semicircular weld. The nozzle rotates a certain angle θy along the Y-axis from the arc termination point of the gantry robot to initiate the arc in a pulling welding posture (e.g., ...). Figure 5 (Diagram of different weld seams restarting arc) After arc restarting, the welding edge changes the angle along the Y-axis until θy≈0°. Weld 85%-90% of the semi-circular weld seam (located on the south side) at θy≈0°. When the arc restarting point of the gantry robot is 10-15mm away, the welding torch nozzle θy gradually changes to a negative angle (in a pushing welding posture). The arc termination point is 5-10mm past the arc restarting point of the gantry robot. After reaching the arc termination point, delay for 0.1s and lift the torch (e.g., Figure 5(Diagram of arc termination of circumferential weld). At this point, the two robots jointly completed the welding of the circumferential weld in the inner layer of the frame. This process is repeated for multiple layers of welding.

[0048] Furthermore, the two gantry robots mentioned above do not have a primary or secondary logic; the order in which the outer robots are called is the determining factor. Once one side of the robots is successfully called, the two robots on that side form a whole, isolated from the other side, and their operational status does not affect each other.

[0049] Furthermore, the gantry robot can only proceed to the next layer of welding after the outer layer of welding is completed. The PLC logic has prohibited uninterrupted welding between the two devices without communication, and a strict sequence is required.

[0050] Furthermore, after every 3-4 layers are welded, the positioner is flipped over before welding again to reduce welding deformation of the frame. The prerequisite for the positioner to flip over is that both robots return to a safe position, which has been achieved using PLC control.

[0051] Furthermore, the TCP movement direction is generally the direction of the straight weld or the tangent direction of the circular weld. The initial arc θy max of the nozzle is generally 20° to 25°. During the process of changing to θy≈0°, the TCP movement distance is about 10-15mm.

[0052] Furthermore, the above-mentioned arc-initiating method is less likely to produce the grooves commonly found at the root of cold-arc-initiated joints (as shown in the attached image). Figure 3 Appendix Figure 6 As shown in the figure, it is well fused with the base material.

[0053] Furthermore, the aforementioned nozzles are welded without push-pull angles, ensuring high heat input to the molten pool and allowing inclusions such as flux to precipitate rapidly with the heat, thus reducing welding defects.

[0054] Furthermore, the arc termination angle θy min of the aforementioned welding torch nozzle is generally -10° to -5°. The terminating arc completely remelts the metal at the root of the arc-starting joint. Under the combined action of gravity and the shielding gas blowing force, the molten metal spreads out evenly, resulting in a smoother and more aesthetically pleasing finish (see attached image for post-weld effect). Figure 6 , Figure 7 );

[0055] Furthermore, the aforementioned 0.1s delay at the arc termination point is to eliminate the influence of robot oscillation welding.

[0056] This invention provides a multi-robot collaborative welding system and method. The welding system enables multiple robots to collaboratively complete welding of circumferential welds, end-to-end welds, and other positions. The optimized arc initiation and termination method solves quality problems such as incomplete fusion and humps and grooves in the pipe-to-plate corner weld joints of the bogie frame.

[0057] Finally, it should be noted that relational terms such as first and second are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A welding process for a multi-machine collaborative welding system, characterized in that, The system includes a first truss welding robot, a second truss welding robot, a first positioner, a second positioner, and a collaborative welding robot. The first truss welding robot is installed on one side of the first positioner, the second truss welding robot is installed on one side of the second positioner, and the collaborative welding robot is located on the other side of the first and second positioners, mounted on a guide rail and capable of moving along the rail to either the first or second positioner. The first and second truss welding robots can move in the XYZ axes. The first frame to be welded is transported to the first station and fixed. The first truss robot welds the outer ring weld of the first frame to be welded. After completion, the control system sends a signal to the collaborative welding robot to collaboratively complete the inner ring weld. According to the production cycle interval, the second frame to be welded is transported to the second station and fixed. The second truss robot welds the outer ring weld of the second frame to be welded. After completion, the control system sends a signal to the collaborative welding robot to collaboratively complete the inner ring weld. The system sends a signal to the outer collaborative welding robot. If the outer collaborative welding robot has completed the welding task at the first station and returned to the zero position, the call is successful, and the inner ring collaborative welding at the second station begins. If the welding task at the first station is not yet completed, it continues to wait until it is completed before starting the welding at the second station. During the inner ring welding, either the first truss robot or the second truss robot welds one side of the inner ring semicircle first, and then sends a command to the outer collaborative welding robot. Upon receiving the command, the outer collaborative welding robot welds the other side of the inner ring semicircle, connecting the two sides. After completion, it sends a completion command to the first truss robot or the second truss robot, and after confirmation, continues welding the next layer. When the first truss robot or the second truss robot welds the outer ring of the structure alone, a welding torch nozzle coordinate system is established at the arc starting point, with the TCP movement direction as the X-axis and the welding wire direction as the Z-axis. The welding torch nozzle at the arc starting point rotates a certain angle θy along the Y-axis. Initiate the arc in a pulling welding posture. After initiating the arc, change the angle along the Y-axis while welding until θy ≈ 0°. Weld 85%-90% of the entire weld seam at θy ≈ 0°. When reaching the set position before the arc initiation point, the welding torch nozzle θy gradually changes to a negative angle for welding. The arc termination point crosses the set distance from the arc initiation point. After reaching the arc termination point, delay the arc termination and lift the torch.

2. The welding process of the multi-machine collaborative welding system as described in claim 1, characterized in that, An aerial conveyor is also installed above the first positioner and the second positioner.

3. The welding process of the multi-machine collaborative welding system as described in claim 1, characterized in that: After each set layer is welded, the collaborative welding robot returns to the zero position, the first positioner and the second positioner reverse ±90°, and the two devices communicate with each other to continue welding until the inner ring weld filling layer and the cover layer of the structure to be welded are completed.

4. The welding process of the multi-machine collaborative welding system as described in claim 1, characterized in that: The TCP movement direction is either the direction of a straight weld or the tangent direction of a circular weld. The maximum value of the nozzle's arc θy is 20°~25°, and the TCP movement distance is 10-15mm during the process of changing to θy ≈0°.

5. The welding process of the multi-machine collaborative welding system as described in claim 1, characterized in that: The minimum arc termination θy of the welding torch nozzle is -10° to -5°.

6. The welding process of the multi-machine collaborative welding system as described in claim 1, characterized in that: When the first truss robot or the second truss robot cooperates with the collaborative welding robot for welding, the first truss robot or the second truss robot establishes a welding torch nozzle coordinate system at the arc initiation point, with the TCP movement direction as the X-axis and the welding wire direction as the Z-axis. At the arc initiation point, the welding torch nozzle rotates along the Y-axis at a certain angle θy to initiate the arc in a pulling welding posture. After the arc is initiated, the welding edge changes the angle along the Y-axis until θy ≈ 0°. Welding 85%-90% of the semi-circular weld layer at θy ≈ 0°, the welding torch nozzle θy gradually changes to a negative angle before the arc termination point. After reaching the arc termination point, the arc is terminated and the torch is lifted after a delay. After the first or second gantry robot completes its welding, the collaborative welding robot begins welding the semi-circular weld on the other side of the layer. Starting from the arc-ending point of the first or second gantry robot, the nozzle rotates along the Y-axis at a certain angle θy to initiate an arc in a pulling welding posture. After arc initiation, the welding process changes the angle along the Y-axis until θy ≈ 0°. Welding 85%-90% of the semi-circular weld in this layer at θy ≈ 0°, the welding torch nozzle gradually changes to a negative angle when it reaches the set position before the arc-starting point of the gantry robot. The arc-ending point crosses the set distance from the arc-starting point of the gantry robot, and the arc-ending and torch-lifting process is delayed after reaching the arc-ending point.

7. The welding process of the multi-machine collaborative welding system as described in claim 6, characterized in that: The minimum arc termination θy of the welding torch nozzle is -10° to -5°.

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