Double-robot collaborative square tube K-TIG butt welding track planning method

Abstract

The invention relates to a double-robot collaborative square tube K-TIG butt welding track planning method, and belongs to the field of welding processes. The double robots are the welding robot and the carrying robot which can work cooperatively, the tail end of a flange of the welding robot is connected with the K-TIG welding gun, the tail end of the carrying robot is connected with the square pipe structural part, and butt joint circumferential welding seams of the square pipe structural part are welded through double-robot cooperative work and the K-TIG welding system. According to the method, the movement tracks of the welding robot and the carrying robot are planned according to the constraint conditions of the position and the speed, so that the K-TIG welding gun is always located above the welding seam by a constant distance and is centered with the welding seam in the welding process, meanwhile, the to-be-welded spot is always in an ideal posture, and it is guaranteed that a molten pool of the welding spot is in a horizontal state as far as possible. And the influence of gravity on a molten pool in the K-TIG welding process is reduced, and it is guaranteed that weld joints of different local areas of a welded component are formed consistently.

Description

Technical Field

[0001] The invention relates to the field of welding technology, in particular to a welding technology combining a K-TIG welding technology and dual-machine collaboration, and more particularly to a dual-robot collaborative square tube K-TIG butt welding welding trajectory planning method. Background Art

[0002] K-TIG is a deep-melting keyhole type non-melting inert gas shielded welding method, which belongs to high-current TIG welding technology. The arc pressure formed by the high current maintains a dynamic balance with the gravity and surface tension of the liquid metal to form a small hole with stable geometric shape, which can realize single-sided welding and double-sided forming of medium and thick plates. K-TIG does not require wire filling or groove opening for materials with a thickness of less than 16 mm (such as ferritic stainless steel, austenitic stainless steel, duplex stainless steel, titanium alloy, zirconium alloy, etc.), but it can be a hundred times more efficient than traditional TIG welding. However, this welding method is more suitable for flat welding. Therefore, when the workpiece has a curved surface (such as pipeline welding), the pipeline needs to be rotated to keep the relative position of the welding gun and the welding track in a flat welding state. Otherwise, vertical welding or overhead welding is more likely to form dripping or welding defects such as melting caused by the collapse of the welding pool. In response to this phenomenon, the existing solutions are pulse welding capping and external axial magnetic field control, but these two methods are very inefficient and require a lot of manpower and material resources for experimental evaluation.

[0003] Due to the complexity of the welding workpiece structure and welding process combination, traditional industrial control systems and production equipment based on a single robot have been unable to meet the needs of production tasks. The multi-robot collaborative system has greatly improved the flexibility and load capacity of the industrial robot system, and can quickly solve the problems caused by the complexity of the welding workpiece structure and welding process combination. Summary of the invention

[0004] The purpose of the present invention is to provide a dual-robot collaborative square tube K-TIG butt welding welding trajectory planning method, which solves the problem of welding defects such as melting caused by the collapse of the K-TIG welding molten pool when the workpiece has a curved surface. The present invention plans the motion trajectory of the welding robot and the handling robot through the constraints of position and speed, so that the K-TIG welding gun is always located at a constant distance above the weld and aligned with the weld during the welding process. At the same time, the relative motion control of the welding robot and the handling robot keeps the K-TIG welding gun in a flat welding state relative to the welding trajectory and the welding speed remains unchanged. The influence of gravity on the molten pool during K-TIG welding is reduced, ensuring that the weld formation of different local areas of the welded component is consistent.

[0005] The above-mentioned object of the present invention is achieved by the following technical solutions: The dual-robot collaborative square tube K-TIG butt welding welding trajectory planning method is to install a K-TIG welding gun and a square tube structure on a collaborative welding robot and a handling robot respectively, and to achieve welding of the butt ring weld of the square tube structure by the collaborative operation of the welding robot and the handling robot and the K-TIG welding system, including the following steps: Step 1: Determine the K-TIG welding process parameters according to the material and thickness of the square tube structure; Step 2: Determine the welding trajectory according to the structure of the square tube structure and the position requirements of the welding point. The welding robot clamps the K-TIG welding gun and starts arcing from the arc starting point P0. After arcing, the K-TIG welding gun moves forward until it reaches the starting point P1 of the arc segment of the square tube structure. The movement speed of the K-TIG welding gun slowly decreases to 0. At this time, the handling robot grabs the square tube structure and rotates it around the center P2 of the arc segment to be welded. When the end point P3 of the arc segment of the square tube structure is used as the welding point, the K-TIG welding gun continues to move forward. To perform the welding task of the straight section of the square tube structure, when it reaches the next arc starting point, the K-TIG welding gun stops moving, and the square tube structure rotates to perform the arc section welding task of the square tube structure; this process is repeated until the K-TIG welding gun completes the welding task of the square tube structure's circumferential weld and reaches the arc extinguishing point P4 to extinguish the arc; the motion trajectory of the dual robots during the welding process is constrained by the welding point to be welded, the posture requirements of the K-TIG welding gun, the height from the tungsten electrode to the workpiece surface in the K-TIG welding process parameters, and the welding speed; Step 3: Divide the welding task into a straight segment welding task module and an arc segment welding task module of the square tube structure according to the structural dimensions of the square tube structure; in different welding task modules, plan the K-TIG welding gun movement speed v and the angular velocity w of the square tube structure rotation according to the size parameters of the square tube structure and the K-TIG welding process parameters.

[0006] The K-TIG welding process parameters are determined according to the material and thickness δ of the square tube structure, including the height d from the tungsten electrode to the workpiece surface, the welding speed v, and the welding current I. The value range of the welding current I is 300~1000A.

[0007] When performing the straight section welding task of the square tube structure, the welding robot clamps the K-TIG welding gun to make linear motion, and the handling robot remains stationary; when performing the arc section welding task of the square tube structure, the welding robot clamps the K-TIG welding gun to remain stationary, and the handling robot grabs the square tube structure and makes a rotational motion with the center of the arc section of the square tube structure as the center.

[0008] When performing the straight segment welding task of the square tube structure, the welding speed v is equal to the movement speed of the K-TIG welding gun; when performing the arc segment welding task of the square tube structure, the welding speed v is equal to the product of the angular velocity w of the square tube structure and the distance r from the node to be welded to the rotation center.

[0009] When performing the straight section welding task of the square tube structure, the total displacement of the K-TIG welding gun is 4a. When performing the arc section welding task of the square tube structure, the total length of the motion trajectory of the center of the square tube structure is Πb; when performing the arc section welding task of the square tube structure, the center of the arc section of the square tube structure is located 45° above the center of the square tube structure and the distance is b; the angular velocity of the square tube structure is w=v / c, and the angle of rotation of the square tube structure is 90°. a, b, and c are the shape parameters of the square tube structure, that is, a is the distance length of a straight section of the square tube structure, b is the distance from the center of the square tube structure to the rotation center, and c is the radius length of the arc section of the square tube structure.

[0010] The beneficial effects of the present invention are: 1. The present invention uses K-TIG welding technology, which does not require beveling before welding, does not require wire filling during welding, and can weld on one side and on both sides, making the welding process 100 times faster than traditional TIG welding technology. This saves costs and greatly improves welding efficiency.

[0011] 2. The dual-machine collaborative welding trajectory planning method proposed in the present invention plans the motion trajectory of the welding robot and the handling robot through the constraints of position and speed, so that the K-TIG welding gun is always located at a constant distance above the weld and aligned with the weld during the welding process, and the weld point is always in an ideal position, that is, the molten pool of the weld point is kept as horizontal as possible. The influence of gravity on the molten pool during K-TIG welding is reduced, ensuring the consistent formation of different local welds of the square tube structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The drawings described herein are used to provide further understanding of the present invention and constitute a part of this application. The illustrative examples of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0013] Figure 1 It is a schematic diagram of an embodiment of a square tube K-TIG butt welding operation coordinated by two robots of the present invention; Figure 2 It is a schematic diagram of the cross-sectional shape of a square tube of the present invention; Figure 3 A welding task flow chart of the welding process of the present invention (the dotted lines represent three welding tasks that need to be performed during the welding process); Figure 4Schematic diagram of the relative motion trajectory of the tungsten electrode tip and the center of the workpiece of the present invention (the red dotted line represents the motion trajectory of the tungsten electrode tip of the K-TIG welding gun, and the blue dotted line represents the motion trajectory of the center of the square tube structure).

[0014] In the figure: 10, welding robot; 11, handling robot; 12, K-TIG welding gun; 13, square tube structural part; 14, butt ring weld of square tube structural part. DETAILED DESCRIPTION

[0015] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0016] See also Figures 1 to 4 As shown, the dual-robot collaborative square tube K-TIG butt welding welding trajectory planning method of the present invention, the robots that can work collaboratively are a welding robot 10 and a handling robot 11, wherein the flange end of the welding robot is connected to a K-TIG welding gun 12, and the end of the handling robot is connected to a square tube structure 13, and the dual-robot collaborative operation and K-TIG welding system are used to achieve high-quality welding of the square tube structure 13 and the square tube structure butt ring weld 14. This method plans the motion trajectory of the welding robot 10 and the handling robot 11 through position and speed constraints, so that during the welding process, the K-TIG welding gun is always located at a constant distance above the weld and aligned with the weld, and the weld point is always in an ideal posture, that is, the molten pool of the weld point is ensured to be as horizontal as possible. Reduce the influence of gravity on the molten pool during K-TIG welding, and ensure that the weld formation of different local areas of the welded component is consistent. Specifically comprising the following steps: Step 1: Determine reasonable K-TIG welding process parameters according to the material and thickness of the square tube structural parts.

[0017] Step 2: Determine the welding trajectory according to the special structure of the square tube structure and the position requirements of the welding point. The welding robot clamps the K-TIG welding gun and starts the arc from the arc starting point P0. After the arc is started, the K-TIG welding gun moves forward a certain distance until it reaches the starting point P1 of the arc segment of the square tube structure. The movement speed of the K-TIG welding gun slowly decreases to 0. At this time, the handling robot grabs the square tube structure and performs a rotation movement with the center P2 of the arc segment to be welded as the center. When the end point P3 of the arc segment of the square tube structure is used as the welding point, the K-TIG welding gun continues to move forward to perform the welding task of the straight segment of the square tube structure. When it reaches the next arc starting point, the K-TIG welding gun stops moving. At this time, the square tube structure rotates to perform the arc segment welding task of the square tube structure. This process is repeated until the K-TIG welding gun completes the welding task of the square tube structure's circumferential weld and reaches the arc extinguishing point P4 to extinguish the arc. The motion trajectory of the dual robots during the welding process is constrained by the posture requirements of the welding point and the K-TIG welding gun, and the height from the tungsten electrode to the workpiece surface and the welding speed in the K-TIG welding process parameters.

[0018] Step 3: According to the structural dimensions of the square tube structure, the welding task is divided into a square tube straight segment welding task module and a square tube arc segment welding task module. In different modules, the K-TIG welding gun movement speed is adjusted according to the size parameters of the square tube structure and the K-TIG welding process parameters, and the angular velocity of the square tube structure rotation is planned.

[0019] Furthermore, in step 1, to ensure the quality of K-TIG welding, the K-TIG welding process parameters need to be determined according to the material and thickness δ of the workpiece to be welded. They include the height d from the tungsten electrode to the workpiece surface, the welding speed v, and the welding current I. The welding current ranges from 300 to 1000A.

[0020] Furthermore, step 2 determines that the welding arc starting position P0 is located at the center line of the straight line segment of the square tube structure, and the welding arc extinction point is P4 near the arc starting point P0, as well as the welding trajectory. The motion trajectory of the dual robots during welding is constrained by the posture requirements of the weld point and the height from the tungsten electrode to the workpiece surface and the welding speed in the K-TIG welding process parameters.

[0021] The posture requirement of the weld point is to ensure that the molten pool of the weld point is as horizontal as possible, and the posture requirement of the K-TIG welding gun is that the K-TIG welding gun is always located at a constant distance above the weld and aligned with the weld.

[0022] Furthermore, in step 3, the welding task is divided into a square tube structural member straight segment welding task module and a square tube structural member arc segment welding task module according to the structural dimensions of the square tube structural member. In different modules, the speed v of the K-TIG welding gun movement and the angular velocity w of the square tube structural member rotation are planned according to the size parameters of the square tube structural member and the K-TIG welding process parameters.

[0023] When performing the task of welding the straight section of a square tube structure, the welding robot clamps the K-TIG welding gun and moves in a straight line, and the handling robot remains stationary. When performing the task of welding the circular section of a square tube structure, the welding robot clamps the K-TIG welding gun and remains stationary, and the handling robot grabs the square tube structure and performs a rotational movement with the center of the circular section of the square tube structure as the center.

[0024] When performing the straight section welding task of the square tube structure, the welding speed v is equal to the movement speed of the welding gun. When performing the arc section welding task of the square tube structure, the welding speed v is equal to the product of the angular velocity w of the square tube structure rotation and the distance r from the node to be welded to the rotation center.

[0025] When performing the straight segment welding task of the square tube structure, the total displacement of the K-TIG welding gun is 4a, and when performing the arc segment welding task of the square tube structure, the total length of the motion trajectory of the center of the square tube structure is Πb.

[0026] When performing the arc segment welding task of the square tube structural member, the center of the arc segment of the square tube structural member is located 45° obliquely above the center of the square tube structural member and the distance is b.

[0027] When performing arc segment welding of a square tube structural member, the angular velocity of the square tube structural member is w=v / c, and the rotation angle θ is 90°.

[0028] a, b, and c are shape parameters of the square tube structure, that is, a is the distance length of a straight line segment of the square tube structure, b is the distance from the center of the square tube structure to the rotation center, and c is the radius length of the arc segment of the square tube structure.

[0029] The K-TIG welding system includes: K-TIG welding gun, K-TIG welding power source, K-TIG second generation control panel, cooling water tank and square tube structural parts. Example

[0030] Taking the butt weld of square tube structural parts as an example, the structural dimensions of square tube structural parts divide the welding task into square tube structural parts straight segment welding task module and square tube structural parts arc segment welding task module. In different modules, the K-TIG welding gun movement speed is adjusted according to the size parameters of the square tube structural parts and the K-TIG welding process parameters, and the angular velocity of the square tube structural parts is planned. The specific implementation steps are as follows: The K-TIG welding gun and square tube structure are connected to the collaborative welding robot and handling robot respectively and the K-TIG welding system is integrated. The base material of the square tube structure is 14mm thick TC4 titanium alloy. The K-TIG welding process is used for welding. The welding current I is 600A, the welding speed is 220mm / min, the shielding gas is 25L / min pure Ar gas, the tungsten electrode extends 12.5mm, the tip angle is 60 degrees, and the distance to the workpiece surface is 1.5mm. The square tube structure is pre-polished and assembled without gaps.

[0031] like Figure 3 As shown, the K-TIG welding gun first strikes an arc at the midpoint P0 of the straight segment of the square tube structure, and the current climbs for 5 seconds to allow the workpiece to be stably perforated. After 5 seconds, the K-TIG welding gun starts to perform the welding task of the straight segment of the square tube structure at a walking speed of 220 mm / min until it reaches the starting point P1 of the circular arc segment of the square tube structure. The movement speed of the K-TIG welding gun slowly decreases to 0. At this time, the handling robot grabs the square tube structure and performs a rotational motion with the center P2 of the circular arc segment to be welded as the center of the circle. After the center of the square tube structure rotates counterclockwise for 90 degrees at a rotation angular velocity w=220 / c, that is, when the end point P3 of the circular arc segment of the square tube structure is used as the welding point, the K-TIG welding gun continues to move forward to perform the welding task of the straight segment of the square tube structure. When it reaches the next starting point of the arc, the K-TIG welding gun stops moving. At this time, the square tube structure rotates to perform the circular arc segment welding task of the square tube structure. This process is repeated until the K-TIG gun completes the welding task of the square tube structural part's circumferential weld and reaches the top of P4 to extinguish the arc. The current drop time during arc extinguishing is 5 seconds. The welding task is completed.

[0032] By using the dual-robot collaborative square tube K-TIG butt welding welding trajectory planning method of the present invention, the obtained annular butt weld of the square tube structural part is continuous and has a very uniform width. The weld surface is bright silver or silver-yellow and no obvious defects such as spatter, pores and cracks are observed.

[0033] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made to the present invention shall be included in the protection scope of the present invention.

Claims

1. A dual-robot collaborative square tube K-TIG butt welding welding trajectory planning method, characterized in that: A K-TIG welding gun and a square tube structure are respectively installed on a welding robot and a handling robot that can work in coordination, and the welding robot and the handling robot work in coordination with the K-TIG welding system to weld the butt ring weld of the square tube structure, including the following steps: Step 1: Determine the K-TIG welding process parameters according to the material and thickness of the square tube structure; Step 2: Determine the welding trajectory according to the structure of the square tube structure and the position requirements of the welding point. The welding robot clamps the K-TIG welding gun and starts arcing from the arc starting point P0. After arcing, the K-TIG welding gun moves forward until it reaches the starting point P1 of the arc segment of the square tube structure. The movement speed of the K-TIG welding gun slowly decreases to 0. At this time, the handling robot grabs the square tube structure and rotates it around the center P2 of the arc segment to be welded. When the end point P3 of the arc segment of the square tube structure is used as the welding point, the K-TIG welding gun continues to move forward. To perform the welding task of the straight section of the square tube structure, when it reaches the next arc starting point, the K-TIG welding gun stops moving, and the square tube structure rotates to perform the arc section welding task of the square tube structure; this process is repeated until the K-TIG welding gun completes the welding task of the square tube structure's circumferential weld and reaches the arc extinguishing point P4 to extinguish the arc; the motion trajectory of the dual robots during the welding process is constrained by the welding point to be welded, the posture requirements of the K-TIG welding gun, the height from the tungsten electrode to the workpiece surface in the K-TIG welding process parameters, and the welding speed; Step 3: Divide the welding task into a straight segment welding task module and an arc segment welding task module of the square tube structure according to the structural dimensions of the square tube structure; in different welding task modules, plan the K-TIG welding gun movement speed v and the angular velocity w of the square tube structure rotation according to the size parameters of the square tube structure and the K-TIG welding process parameters.

2. The dual-robot collaborative square tube K-TIG butt welding welding trajectory planning method according to claim 1 is characterized in that: The K-TIG welding process parameters are determined according to the material and thickness δ of the square tube structure, including the height d from the tungsten electrode to the workpiece surface, the welding speed v, and the welding current I.

3. The dual-robot collaborative square tube K-TIG butt welding welding trajectory planning method according to claim 1 is characterized in that: When performing the task of welding the straight section of the square tube structure, the welding robot clamps the K-TIG welding gun to make a linear motion, and the handling robot remains stationary; when performing the task of welding the arc section of the square tube structure, the welding robot clamps the K-TIG welding gun to remain stationary, and the handling robot grabs the square tube structure and makes a rotational motion with the center of the arc section of the square tube structure as the center of the circle; When performing the straight section welding task of the square tube structure, the welding speed v is equal to the movement speed of the K-TIG welding gun; when performing the arc section welding task of the square tube structure, the welding speed v is equal to the product of the angular velocity w of the square tube structure rotation and the distance r from the node to be welded to the rotation center; When performing the straight section welding task of the square tube structure, the total displacement of the K-TIG welding gun is 4a. When performing the arc section welding task of the square tube structure, the total length of the motion trajectory of the center of the square tube structure is Πb. When performing the arc section welding task of the square tube structure, the center of the arc section of the square tube structure is located 45° above the center of the square tube structure and the distance is b. The angular velocity of the square tube structure is w=v / c, and the angle θ of the square tube structure is 90°. a, b, and c are shape parameters of the square tube structure, that is, a is the distance length of a straight line segment of the square tube structure, b is the distance from the center of the square tube structure to the rotation center, and c is the radius length of the arc segment of the square tube structure.

4. The dual-robot collaborative square tube K-TIG butt welding welding trajectory planning method according to claim 2 is characterized in that: The welding current I has a value range of 300~1000A.

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