A device specially used for automatic welding of a square groove weld

Abstract

This invention relates to the field of welding automation technology, and more particularly to a device specifically designed for automatic welding of U-shaped welds. The device includes a work platform, a welding torch movement adjustment mechanism, a welding torch posture adjustment unit, a welding system, and a control system. The control system integrates an inflection point steering control module, which, through software-set trajectory settings, controls the welding torch posture, current, voltage, and welding speed during welding. This allows the invention to achieve smooth, continuous, and automatic welding at the inflection points of U-shaped welds without requiring pauses, adjustments, or repeated arc striking. This invention significantly increases welding efficiency, reduces welding difficulty, and improves welding quality.

Description

Technical Field

[0001] This invention relates to the field of welding automation technology, and in particular to a device specifically designed for automatic welding of U-shaped weld seams. Background Technology

[0002] In industries such as automotive parts, machinery manufacturing, and pressure vessels, there are numerous closed weld seam structures characterized by a "U" shape, such as automobile bodies, electrical distribution box housings, motor end covers, and square flanges. These types of weld seams typically require high welding strength, aesthetically pleasing finish, and consistent welding quality across all four sides and at all four inflection points.

[0003] In existing technologies, the welding of U-shaped welds mainly relies on the following methods:

[0004] 1. Manual welding: Operators move along the weld seam with a hand-held welding torch. This method is labor-intensive, inefficient, and the quality of the weld seam fluctuates greatly due to skill level. Defects such as undercut, lack of fusion, and weld beads are prone to occur at inflection points.

[0005] 2. General Robotic Welding: This method uses a six-axis industrial robot equipped with a welding torch, achieving automated welding through teach programming. However, the robots are expensive, the programming is complex, and for small batches of multi-specification U-shaped welds, the teach-in cycle is long and the flexibility is insufficient.

[0006] 3. Dedicated welding machines: Some companies use customized rectangular coordinate welding machines, but traditional dedicated machines often use "right-angle hard turns" or "stop and turn" in the handling of inflection points, which leads to sudden speed changes, unstable arcs, and poor weld formation at the inflection points. At the same time, the welding torch posture is fixed and cannot adapt to the welding needs of inflection points with different plate thicknesses and bevel forms.

[0007] Therefore, developing a low-cost, high-efficiency welding device for U-shaped welds that can precisely control the turning point is key to solving the above problems. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by providing a device specifically designed for automatic welding of U-shaped weld seams. Its core objective is to achieve smooth and high-precision turning of the welding torch at the inflection point, thereby ensuring overall welding quality and efficiency.

[0009] The technical solution adopted by this invention to solve its technical problem is: a device specifically for automatic welding of U-shaped welds, comprising:

[0010] Operating platform: Provides overall support;

[0011] Workpiece positioning and clamping mechanism: set on the working platform, used to position and clamp the workpiece to be welded;

[0012] Welding torch movement adjustment mechanism: includes an X-axis movement component, a Y-axis movement component and a welding torch posture adjustment mechanism. The X-axis movement component and the Y-axis movement component are orthogonally arranged. The welding torch posture adjustment mechanism is mounted on the Y-axis movement component and is used to drive the welding torch to achieve in-plane movement and posture adjustment.

[0013] Welding system: includes welding power source, wire feeding mechanism (gas shielded welding also includes gas supply mechanism) and welding torch, wherein the welding torch is connected to the welding torch posture adjustment mechanism;

[0014] Control system: electrically connected to the workpiece positioning and clamping mechanism, the welding torch movement and adjustment mechanism, and the welding system respectively;

[0015] Inflection point steering control module: Integrated into the control system, it is used to plan the movement trajectory of the welding torch at the inflection point of the U-shaped weld seam and control the welding torch movement adjustment mechanism to achieve smooth steering.

[0016] Preferably, the inflection point steering control module includes:

[0017] The trajectory planning unit pre-stores at least one standard trajectory model for a U-shaped weld, supports user-defined input of weld size parameters (length L, width W, inflection point transition radius R), and generates a continuous welding trajectory containing straight line segments and circular arc transition segments based on the parameters.

[0018] The motion control unit receives instructions from the trajectory planning unit and controls the movement of the welding torch through the linkage interpolation (linear interpolation and circular interpolation) of the X-axis and Y-axis servo motors.

[0019] The welding torch posture adjustment unit adjusts the spatial posture of the welding torch according to the current welding position (straight line segment or inflection point) and preset process parameters (such as welding speed v, welding torch tilt angle θ, height h).

[0020] Preferably, the trajectory planning unit adopts a three-segment transition trajectory of "straight line-circular arc-straight line" at the inflection point. The radius R of the circular arc transition segment can be set through the human-computer interaction interface, with a value range of 5mm to 50mm, and satisfies R ≥ v² / (2a), where a is the maximum acceleration of the X-axis and Y-axis.

[0021] Preferably, the motion control unit performs the following steps during the inflection point turning process:

[0022] S1. Uniform motion on a straight line: Control the welding torch to move along the current straight line at a set speed v, and monitor the position information fed back by the encoder in real time;

[0023] S2. Deceleration before the inflection point: When the welding torch is S = v² / (2a) away from the starting point of the inflection point, the deceleration program is started to make the welding torch speed decrease uniformly from v to v1 (v1 = 0.3v~0.6v).

[0024] S3. Circular transition segment motion: Control the X-axis and Y-axis motors to move in a circular interpolation manner, so that the welding torch moves along a circular arc trajectory with radius R at a speed v1, completing a 90° turn;

[0025] S4. Acceleration after the inflection point: After the arc segment ends, control the welding torch to accelerate uniformly to the set speed v, and enter the next linear segment.

[0026] Preferably, the welding torch posture adjustment unit includes:

[0027] The rotating axis (A-axis) drives the welding torch to rotate around it, changing the tilt direction of the welding torch;

[0028] The tilting axis (B-axis) drives the welding torch to tilt within the welding plane, and adjusts the angle θ (-20°~20°) between the welding torch and the rotation axis; the welding plane is defined as the plane formed by the weld and the rotation axis, and the angle θ between the welding torch and the rotation axis is the travel angle;

[0029] The skew axis (C-axis) drives the welding torch to skew relative to the vertical surface of the weld (flat welding), adjusting the angle β (0°~45°) between the welding torch and the vertical surface of the weld. The skew axis is mainly used for T-shaped welding of two plates, where one plate is horizontal and the other is vertical. In this case, because the vertical plate is blocking the way, the welding torch needs to skew relative to the vertical plate. The angle β is the angle between the welding torch (or welding plane) and the vertical plate. The angle β is also called the working angle.

[0030] The height adjustment axis (Z-axis) drives the welding torch to rise and fall, adjusting the distance h (5mm~20mm) between the nozzle and the workpiece surface.

[0031] Preferably, the welding torch posture adjustment mechanism includes:

[0032] Welding torch height adjustment mechanism: includes a base plate, the base plate is provided with a linear rail, the linear rail is slidably connected to a connecting plate via a slider, the base plate is rotatably connected to a lead screw, and a height adjustment motor is provided to drive the lead screw to rotate, the lead screw and the connecting plate are connected by a lead screw nut;

[0033] Rotary shaft mechanism (A-axis): includes a rotary table disposed at the bottom end of the connecting plate, and a vertical rotary shaft is fixed at the center of the rotary table; the welding torch rotates 360° around the rotary shaft, and the rotary table is driven by a stepper motor, rotating 90° each time it turns an angle;

[0034] Inclined shaft mechanism (B-axis): The rotary shaft is fitted with a sliding sleeve, which is fixed to the rotary shaft by screws. A hinge plate is provided on each opposite side of the sliding sleeve. One hinge plate is rotatably connected to a hinge shaft, which is fixed with a mounting sleeve for clamping a welding torch. The sliding sleeve is also equipped with an inclination motor, the output shaft of which is fixedly connected to the hinge shaft. The angle between the axis of the mounting sleeve and the rotary shaft is the aforementioned angle θ.

[0035] The skew shaft mechanism (C-axis) includes a rotary flange, and the base plate is connected to the Y-axis moving assembly through the rotary flange. When welding a T-shaped weld, the skew shaft mechanism drives the base plate to rotate, thereby causing the welding torch to be skewed relative to the vertical plate.

[0036] Guiding device: On the other side of the sliding sleeve, the hinge plate is hinged to a second hinge shaft. A mounting plate is fixed to the second hinge shaft. A guiding unit, a laser sensor, is mounted on the mounting plate through an elongated hole. A guiding motor is fixed to the sliding sleeve. The output shaft of the guiding motor is fixedly connected to the second hinge shaft. The detection point of the guiding unit is located in front of the welding point. The mounting plate installs the guiding unit through an elongated hole, which allows adjustment of the left and right positions of the guiding unit, ensuring that the guiding unit and the welding torch are collinear and their movement trajectories coincide. The guiding motor controls the tilt angle of the laser sensor, thereby adjusting the distance between the laser's landing point and the welding point.

[0037] Anti-collision switch: On the other side of the sliding sleeve, the hinge plate is also fixed with a second mounting plate, and the second mounting plate is fixed with an anti-collision switch; the anti-collision switch is an infrared sensor, which can detect obstacles in advance, and then control the X and Y axis walking mechanism to stop after feeding back a signal, thereby protecting the guide unit;

[0038] Feedback Unit: The mounting sleeve is equipped with a feedback unit that follows the welding torch. The feedback unit is an encoder to provide real-time feedback on the X, Y, Z positions and θ and β angles of the welding torch.

[0039] The hinge shaft and the second hinge shaft are both three shafts that are integrally machined and coaxial, with the middle section being a round shaft and the two ends being symmetrical hexagonal prism shafts.

[0040] The principle of the aforementioned guidance unit guiding the welding torch is as follows: First, the relative position of the welding torch and the laser sensor is one of the core factors determining welding accuracy, and their spatial arrangement directly affects the collaborative efficiency of laser detection and welding operations. As the "eye" for weld seam positioning, the laser sensor, limited by optical principles and detection range, has its effective sensing area strictly confined to a specific spatial interval in the middle. That is, the sensor can only output a high-precision position signal when the weld seam is within this interval; if it exceeds this range, not only will the detection data show significant errors, but it may even lose the signal due to abnormal light spot reflection angles. Therefore, the position of the welding torch tip should be fixed directly behind the laser detection center, forming a continuous operational sequence of "detection first, welding later": the laser sensor captures the weld seam position before the welding torch, feeding back data to the control system in real time. By the time the welding torch reaches the corresponding position, trajectory correction has been completed, ensuring that each welding point accurately falls on the center of the weld seam, achieving collaboration between detection and welding actions.

[0041] Preferably, the control logic of the welding torch posture adjustment unit at the inflection point is as follows:

[0042] Straight line segment: θ = θ0 (preset fixed tilt angle), h = h0 (preset fixed height);

[0043] Circular transition section: θ is linearly adjusted from θ0 to θ1 (θ1 = θ0 ± Δθ, Δθ ≤ 10°), and h is compensated from h0 to h1 (h1 = h0 - Δh, Δh is corrected in real time by arc voltage feedback, with a correction range of ±2mm).

[0044] Preferably, the workpiece positioning and clamping mechanism includes positioning reference blocks (at least two in the X direction and at least two in the Y direction), pneumatic clamping cylinders (at least four, distributed at the four corners of the workpiece), and elastic pressure heads. The elastic pressure heads are made of polyurethane material to avoid damaging the workpiece surface.

[0045] Preferably, the X-axis moving component of the welding torch moving adjustment mechanism adopts a roller with gear and rack transmission, the Y-axis moving component adopts a linear guide with gear and rack transmission, driven by a servo motor, with a repeatability of positioning accuracy ≤ ±0.2mm and a maximum moving speed ≤ 1000mm / min.

[0046] Preferably, the control system further includes:

[0047] The human-machine interface unit (touch screen) is used for parameter setting (weld size, welding process, motion parameters), status display and fault alarm;

[0048] The sensor module includes travel limit switches (positive and negative limits of X-axis and Y-axis), origin switch, arc voltage sensor and temperature sensor;

[0049] The storage unit is used to store at least 100 sets of welding programs and process parameters.

[0050] Preferably, the automatic welding device provided by the present invention includes the following steps during operation:

[0051] (1) Parameter input and trajectory generation: The user inputs the length L, width W, inflection point transition radius R and welding process parameters of the U-shaped weld, and the trajectory planning unit automatically generates a complete welding trajectory;

[0052] (2) Workpiece clamping and zeroing: Place the workpiece on the positioning reference block, start the workpiece positioning and clamping mechanism to complete the clamping, and control the welding torch to move to the origin position.

[0053] (3) Welding process execution: Start the welding program, the welding torch moves along the planned trajectory, and the straight segment is welded at a constant speed v;

[0054] (4) Inflection point steering control: When the welding torch moves to the inflection point area, the motion control unit switches to the circular interpolation mode, and synchronously adjusts the speed of the X-axis and Y-axis, and the welding torch attitude adjustment unit corrects the welding torch tilt angle and height in real time;

[0055] (5) Welding ends: After completing one cycle of welding, the welding torch returns to the origin, the workpiece positioning and clamping mechanism is released, and the welding process ends.

[0056] The beneficial effects of this invention are as follows: This invention provides a device specifically for the automatic welding of U-shaped weld seams, and compared with the prior art, it has the following advantages:

[0057] Significantly improved quality at inflection points: By adopting a circular arc transition trajectory and adaptive posture adjustment, the weld formation at inflection points is smooth, and the defect rate such as undercut and lack of fusion is reduced by more than 90%. Moreover, compared with the existing semi-automatic welding equipment that can only weld in straight lines, the welding quality at inflection points is further improved because there is no need to stop and correct or repeat the arc striking at the inflection points.

[0058] High welding efficiency: The welding cycle for a single workpiece is shortened by 60% compared to manual welding, and continuous operation can be achieved 24 hours a day;

[0059] Simple to operate: By replacing complex teaching with parameter input, ordinary workers can start working after 1 hour of training;

[0060] High compatibility: Supports welding of U-shaped welds of different sizes (plate length and width range ≥200mm) and plate thickness (≥2mm). When changing workpieces, only the positioning reference block and parameters need to be adjusted.

[0061] Significant cost advantage: The total cost of the equipment is about 1 / 3 to 1 / 2 of that of a six-axis robotic welding workstation, making it suitable for small to medium batch production. Attached Figure Description

[0062] Figure 1 This is a perspective view of a device for automatic welding of a U-shaped weld seam according to the present invention;

[0063] Figure 2 This is a front view of a device specifically designed for automatic welding of U-shaped weld seams according to the present invention;

[0064] Figure 3 yes Figure 2 The left view;

[0065] Figure 4 This is a perspective view of the welding torch posture adjustment mechanism;

[0066] Figure 5 This is a front view of the welding torch posture adjustment mechanism;

[0067] Figure 6 yes Figure 5 The right view.

[0068] Explanation of reference numerals in the attached figures:

[0069] 1 – Welding torch height adjustment mechanism; 11 – Base plate; 12 – Linear rail; 13 – Connecting plate; 14 – Lead screw; 15 – Height adjustment motor; 2 – Rotary shaft mechanism; 21 – Turntable; 22 – Rotary shaft; 3 – Tilting shaft mechanism; 31 – Sliding sleeve; 32 – Hinge plate; 33 – Hinge shaft; 34 – Mounting sleeve; 35 – Tilting motor; 4 – Skew shaft mechanism; 41 – Rotary flange; 5 – Guide device; 51 – Hinge shaft II; 52 – Mounting plate I; 53 – Guide unit; 54 – Guide motor; 55 – Mounting plate II; 56 – Anti-collision switch; 6 – Feedback unit; 7 – Welding torch movement adjustment mechanism; 8 – Control system; 9 – Welding system. Detailed Implementation

[0070] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0071] Example 1: Trailer floor panel splicing and welding.

[0072] Workpiece parameters: Q235 steel plate, length 10000mm × width 3000mm, plate thickness 12mm, four butt joints forming a U-shaped weld.

[0073] To achieve the above objectives, this embodiment designs a device specifically for automatic welding of U-shaped weld seams, such as... Figures 1-6 As shown, the specific technical solution is as follows:

[0074] Operating Platform

[0075] The work platform adopts a profile welding structure, which is subjected to aging treatment to eliminate internal stress, and is equipped with adjustable feet at the bottom to ensure the levelness of the equipment.

[0076] Workpiece positioning and clamping mechanism

[0077] Positioning component: It consists of at least 4 X-axis positioning reference blocks and at least 4 Y-axis positioning reference blocks to form a rectangular coordinate system for positioning with a positioning accuracy of ≤ ±0.1mm. The X-axis positioning reference blocks and the Y-axis positioning reference blocks are evenly distributed on opposite sides of the working platform. The X-axis positioning reference blocks and the Y-axis positioning reference blocks are fixedly connected to the horizontally arranged screw rods that are threaded to the working platform.

[0078] Clamping assembly: at least 4 pneumatic clamping units (including cylinders, piston rods, and elastic pressure heads) are distributed at the four corners of the workpiece, with clamping force adjustable from 0 to 500 N and response time ≤ 0.5 s;

[0079] Auxiliary support: A liftable support platform is provided under the workpiece to accommodate workpieces of different heights (adjustment range 0~200mm).

[0080] The workpiece is horizontal after clamping.

[0081] Welding torch movement adjustment mechanism 7

[0082] The welding torch movement adjustment mechanism 7 adopts a five-degree-of-freedom design of "XYZ-θ-β".

[0083] The X-axis moving component has tracks on both sides of the work platform along its length. The X-axis moving component is connected to the tracks via rollers, which are equipped with rims to prevent derailment. The tracks are equipped with racks on the sides. A servo motor (400W power, 1000 lines encoder resolution) drives the gears to mesh with the racks at a speed of 0~1000mm / min.

[0084] The Y-axis moving component spans across the top of the work platform, and its two ends are connected to the X-axis moving component in a U-shape. It is equipped with linear guides, racks, and gears driven by a servo motor (400W power, encoder resolution 1000 lines), with a speed of 0~1000mm / min.

[0085] Welding torch posture adjustment mechanism: mounted on the Y-axis slide, including Z-axis lifting module (stroke 0~300mm), rotation axis A (to change the tilt direction of the welding torch, so that it gradually rotates 90° at the inflection point to follow the welding trajectory), tilt axis B (to adjust the tilt angle of the welding torch relative to the rotation axis 15°→20°→15°), and skew axis C, all driven by stepper motors, with a positioning accuracy of ±0.1°.

[0086] The welding torch posture adjustment mechanism includes:

[0087] Welding torch height adjustment mechanism 1: includes a base plate 11, the base plate 11 is provided with a linear guide 12, the linear guide 12 is slidably connected to a connecting plate 13 via a slider, the base plate 11 is rotatably connected to a lead screw 14, and a height adjustment motor 15 is provided to drive the lead screw 14 to rotate, the lead screw 14 and the connecting plate 13 are connected by a lead screw nut;

[0088] Rotary shaft mechanism (A-axis) 2: includes a rotary disk 21 disposed at the bottom end of the connecting plate 13, and a vertical rotary shaft 22 is fixed at the center of the rotary disk 21;

[0089] Inclined shaft mechanism (B-axis) 3: The rotary shaft 22 is sleeved with a sliding sleeve 31, which is fixed to the rotary shaft 22 by screws. A hinge plate 32 is provided on each of the opposite sides of the sliding sleeve 31. One side of the hinge plate 32 is rotatably connected to a hinge shaft 33. The hinge shaft 33 is fixed with a mounting sleeve 34 for clamping the welding gun. The sliding sleeve 31 is also provided with an inclination motor 35, and the output shaft of the inclination motor 35 is fixedly connected to the hinge shaft 33.

[0090] The skew shaft mechanism (C-axis) 4 includes a rotary flange 41, and the base plate 11 is connected to the Y-axis moving assembly through the rotary flange 41;

[0091] Guiding device 5: On the other side of the sliding sleeve 31, the hinge plate 32 is hinged to a second hinge shaft 51. The second hinge shaft 51 is fixed to a first mounting plate 52. The first mounting plate 52 is equipped with a guiding unit 53 through an elongated hole. The guiding unit 53 is a laser sensor. The sliding sleeve 31 is fixed to a guiding motor 54. The output shaft of the guiding motor 54 is fixedly connected to the second hinge shaft 51. The detection point of the guiding unit 53 is located in front of the welding point.

[0092] Anti-collision switch 56: On the other side of the sliding sleeve 31, the hinge plate 32 is also fixed with a second mounting plate 55, and the second mounting plate 55 is fixed with an anti-collision switch 56; the anti-collision switch 56 is an infrared sensor;

[0093] Feedback unit 6: The mounting sleeve 34 is provided with a feedback unit 6 that follows the welding torch. The feedback unit 6 is an encoder to provide real-time feedback on the X, Y, Z positions and θ and β angles of the welding torch.

[0094] Welding System 9

[0095] The process employs gas metal arc welding (MIG welding), including:

[0096] Welding power supply: Digital inverter power supply, output current 50A~500A, voltage 15V~40V, supports single-mode adjustment;

[0097] Wire feeding mechanism: push-type wire feeder, wire feeding speed 1~15m / min, welding wire diameter 0.8mm~1.2mm;

[0098] Gas delivery mechanism: The gas cylinder is connected to the welding torch via a hose;

[0099] Welding torch: Gooseneck air-cooled welding torch, equipped with a conductive nozzle and a protective sleeve, and installed on the mounting sleeve 34 of the welding torch attitude adjustment mechanism.

[0100] Control System 8

[0101] Based on a PLC (model: Siemens S7-1214C), and equipped with a touch screen (Kunlun Tongtai TPC1061Ti) as the human-machine interface, it includes:

[0102] Main control module: responsible for logical operations, program execution, and coordination among units;

[0103] Motion control module: Uses Siemens V90 servo driver to realize closed-loop position control and interpolation calculation of X and Y axes;

[0104] Inflection point steering control module: This is the core of the invention. Its hardware is based on a high-speed counting module (1MHz) extended from a PLC and an analog output module, while its software integrates trajectory planning, motion control and attitude adjustment algorithms.

[0105] Inflection point steering control module (core innovation)

[0106] This module achieves precise steering at inflection points through the following techniques:

[0107] (1) Trajectory planning method

[0108] Traditional right-angle turns can easily lead to sudden speed changes. This invention uses a smooth transition trajectory of "straight line-circular arc-straight line":

[0109] Let the length of the square weld be L, the width be W, and the radius of the transition arc at the inflection point be R. Then the complete trajectory consists of 4 straight line segments (lengths L-2R, W-2R, L-2R, W-2R respectively) and 4 circular arc segments (radius R, central angle 90°).

[0110] The starting / ending point of the circular arc segment is tangent to the straight line segment to ensure the continuity of the trajectory (continuity of the first derivative).

[0111] The radius of the arc R can be dynamically adjusted according to the welding speed v and the equipment acceleration a. By default, R ≥ v² / (2a) is satisfied to avoid trajectory distortion due to insufficient acceleration.

[0112] (2) Motion control strategies

[0113] To achieve smooth steering, the motion control unit performs "speed look-ahead control":

[0114] Deceleration zone setting: Start deceleration at S = v² / (2a) before the inflection point (e.g., v = 600 mm / min, a = 10 mm / s², then S ≈ 5 mm) to ensure that the welding torch enters the arc segment at a low speed v1 (v1 = 0.3v~0.6v) to reduce inertial impact;

[0115] Dual-axis linkage interpolation: During circular arc motion, the X-axis and Y-axis motors output speeds according to sine and cosine laws respectively, and the composite trajectory is a circular arc. For example, for the upper right corner inflection point, the X-axis speed changes from v1 to 0, and the Y-axis speed changes from 0 to v1. The sum of the squares of the two axis speeds is v1², ensuring a constant circular arc speed.

[0116] Real-time feedback correction: The position is fed back in real time by X-axis and Y-axis encoders, and the PLC corrects the motor output every 1ms, with a position tracking error of ≤±0.05mm.

[0117] (3) Adaptive adjustment of welding torch posture

[0118] At inflection points, welding heat input tends to concentrate, requiring adjustment of the welding torch posture to optimize molten pool formation. Furthermore, this embodiment is used for base plate splicing welding; therefore, the welding torch is located within the vertical plane where the weld is located. Based on the structural features of the welding torch posture adjustment unit, the rotation axis 22 is perpendicular to the workpiece and coincides with the workpiece normal.

[0119] Rotation axis adjustment: In this embodiment, the welding torch is located within the vertical plane where the weld is located. Before and after entering the inflection point, in order to keep the welding torch within the vertical plane where the weld is located, the rotation axis mechanism 2 needs to drive the rotation axis 22 to rotate 90° gradually to follow the movement trajectory of the welding torch.

[0120] Tilt angle adjustment: The tilt angle, also called the travel angle, refers to the angle θ = 15° (forward tilt) between the welding torch and the rotating axis A. When entering the inflection point, the tilt motor 35 drives the hinge shaft 33 to rotate the mounting sleeve 34, so that θ gradually increases to 15°~20°, and then returns to θ = 15° (forward tilt) to avoid arc overshoot.

[0121] Working angle adjustment: The working angle is the angle between the welding torch and the vertical plane where the weld is located. The working angle is adjusted before welding begins and remains unchanged during the welding process, including at inflection points. In this embodiment, the welding torch is located within the vertical plane where the weld is located, and the working angle β = 0°.

[0122] Height adjustment: The arc length is monitored in real time by an arc voltage sensor (voltage is proportional to arc length). When a voltage fluctuation is detected to exceed ±2V, the Z-axis module is driven to fine-tune the welding torch height (adjustment amount ±0.5mm / time) to ensure arc length stability.

[0123] Welding parameter matching: Reduce speed at the inflection point and simultaneously reduce welding current (I1 ≈ I0×v1 / v, where I0 is the current in the straight segment) to avoid weld beads.

[0124] Workflow

[0125] (1) Workpiece clamping: Place the workpiece on the work platform, rotate the screw to drive the positioning reference block to fine-tune the workpiece, step on the foot switch, and the pneumatic clamping unit will be activated to complete the workpiece positioning and clamping.

[0126] (2) Parameter settings: Users input parameters such as the size of the U-shaped weld (L=10000mm, W=3000mm), the radius of the inflection point (R=10mm), the diameter of the welding wire (Ф=1.2mm), the welding speed (v=500mm / min), the current (I=260A), and the voltage (U=27V) through the touch screen, and the system automatically generates the welding trajectory;

[0127] (3) Automatic welding: Click the "Start" button to execute the system;

[0128] (4) Move the welding torch to the arc starting point (default is the X-axis weld near the lower right corner), feed the wire, turn on the gas, and start the arc;

[0129] (5) Move along the positive X-axis (straight segment 1: length L-2R-arc reserved segment 80=9900mm), speed 500mm / min;

[0130] (6) Approaching the upper right corner inflection point: decelerate to v1=250mm / min, perform circular interpolation on the X and Y axes (R=10mm), while simultaneously increasing the welding torch tilt angle from 15° to 20°, reducing the current to 160A, and reducing the voltage to 22V;

[0131] (7) Complete the welding of the remaining three sides and the inflection point in sequence, and finally extinguish the arc near the arc starting point (overlap 5mm~10mm).

[0132] (8) End process: The welding torch returns to the origin, the clamping unit is released, and the workpiece is taken out.

[0133] Example 2: Welding of the distribution box housing.

[0134] Workpiece parameters: Q235 steel plate, length 600mm × width 400mm × height 200mm, plate thickness 2mm, four longitudinal seams forming a square weld.

[0135] Welding parameters: ER50-6 welding wire (0.8mm diameter), shielding gas 80%Ar+20%CO2, welding speed 450mm / min, current 160A, voltage 22V, inflection point radius R=5mm;

[0136] Welding results: The welding time for a single workpiece is 5.5 minutes, the weld reinforcement is 0.5mm~1.0mm, the undercut depth is ≤0.1mm, and the pass rate of non-destructive testing (MT) is 100%.

[0137] Example 3: Welding of square flanges.

[0138] Workpiece parameters: 304 stainless steel, side length 500mm×500mm, plate thickness 5mm, bevel type V-shaped (angle 60°, blunt edge 1mm).

[0139] Welding parameters: ER308 welding wire (1.0mm diameter), pure Ar shielding, welding speed 300mm / min, current 220A, voltage 25V, inflection point radius R=8mm;

[0140] Welding results: Post-weld deformation ≤0.5mm / m, penetration depth at inflection point ≥2.5mm, meeting the requirements of JB / T 4709-2000 standard.

[0141] This invention solves the core problem of welding the inflection point of a U-shaped weld by using innovative trajectory planning, motion control and attitude adjustment technologies. The device has a compact structure, is easy to operate and has low cost. It can be widely used in the automated production of U-shaped welds in various industries and has significant economic and social benefits.

[0142] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and for the convenience of describing the technical solutions, the front, back, left, right, top, middle, and bottom orientations are based on the accompanying drawings and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A device specifically for automatic welding of U-shaped weld seams, characterized in that: include: Operating platform: Provides overall support; Workpiece positioning and clamping mechanism: set on the working platform, used to position and clamp the workpiece to be welded; Welding torch movement adjustment mechanism: includes an X-axis movement component, a Y-axis movement component and a welding torch posture adjustment mechanism. The X-axis movement component and the Y-axis movement component are orthogonally arranged. The welding torch posture adjustment mechanism is mounted on the Y-axis movement component and is used to drive the welding torch to achieve in-plane movement and posture adjustment. Welding system: includes welding power source, wire feeding mechanism, gas supply mechanism and welding torch, wherein the welding torch is connected to the welding torch posture adjustment mechanism; Control system: electrically connected to the workpiece positioning and clamping mechanism, the welding torch movement and adjustment mechanism, and the welding system respectively; Inflection point steering control module: integrated into the control system, used to plan the movement trajectory of the welding torch at the inflection point of the U-shaped weld seam, and control the welding torch movement adjustment mechanism to achieve smooth steering; The inflection point steering control module includes: The trajectory planning unit pre-stores at least one standard trajectory model for a U-shaped weld, supports user-defined input of weld size parameters, and generates a continuous welding trajectory containing straight line segments and circular arc transition segments based on the parameters. The motion control unit receives instructions from the trajectory planning unit and controls the movement of the welding torch through the interpolation of the X-axis and Y-axis servo motors. The welding torch posture adjustment unit adjusts the spatial posture of the welding torch according to the current welding position and preset process parameters; The welding torch posture adjustment unit includes: The rotating axis (A-axis) drives the welding torch to rotate around it, changing the tilt direction of the welding torch; The tilting axis (B-axis) drives the welding torch to tilt in the welding plane. The angle θ between the welding torch and the rotation axis is adjusted, where the adjustment range of θ is -20° to 20°. The skew axis (C-axis) drives the welding torch to skew relative to the vertical plane where the weld is located, and adjusts the angle β between the welding torch and the vertical plane where the weld is located, where the adjustment range of β is 0°~45°; The height adjustment axis (Z-axis) drives the welding torch to rise and fall, adjusting the distance h between the nozzle and the workpiece surface; The method for adaptive adjustment of welding torch posture is: Rotation axis adjustment: When entering the inflection point and before and after the inflection point, the rotation axis gradually rotates 90° following the movement trajectory of the welding torch; Tilt angle adjustment: The tilt angle, also called the travel angle, refers to the angle θ between the welding torch and the rotation axis. When entering the inflection point, θ is gradually increased to 15°~20°, and then returned to θ=15° to avoid arc overshoot. Working angle adjustment: The working angle is the angle between the welding torch and the vertical plane where the weld is located. The working angle is adjusted before welding begins and remains unchanged during the welding process, including at inflection points. Height adjustment: The arc length is monitored in real time by an arc voltage sensor. When the voltage fluctuation exceeds ±2V, the Z-axis module is driven to fine-tune the welding torch height by ±0.5mm / time to ensure arc length stability. Welding parameter matching: at the inflection point, the speed is reduced, and the welding current I1 ≈ I0×v1 / v is reduced simultaneously to avoid weld beads. Here, I0 is the current in the straight segment, v1 is the moving speed of the welding torch at the inflection point, and v is the moving speed of the welding torch.

2. The device for automatic welding of U-shaped weld seams according to claim 1, characterized in that: The trajectory planning unit adopts a three-segment transition trajectory of "straight line-circular arc-straight line" at the inflection point. The radius R of the circular arc transition segment can be set through the human-computer interaction interface, with a value range of 5mm to 50mm, and satisfies R ≥ v² / (2a), where a is the maximum acceleration of the X-axis and Y-axis.

3. The device for automatic welding of U-shaped weld seams according to claim 1, characterized in that: The motion control unit performs the following steps during the inflection point steering process: S1. Uniform motion on a straight line: Control the welding torch to move along the current straight line at a set speed v, and monitor the position information fed back by the encoder in real time; S2. Deceleration before the inflection point: When the welding torch is S = v² / (2a) away from the starting point of the inflection point, the deceleration program is started to make the welding torch speed uniformly decelerate from v to v1, v1 = 0.3v~0.6v, where a is the acceleration of the welding torch on the X-axis and Y-axis; S3. Circular transition segment motion: Control the X-axis and Y-axis motors to move in a circular interpolation manner, so that the welding torch moves along a circular arc trajectory with radius R at a speed v1, completing a 90° turn; S4. Acceleration after the inflection point: After the arc segment ends, control the welding torch to accelerate uniformly to the set speed v, and enter the next linear segment.

4. The device for automatic welding of U-shaped weld seams according to claim 1, characterized in that: The welding torch posture adjustment unit includes: Welding torch height adjustment mechanism: includes a base plate, the base plate is provided with a linear rail, the linear rail is slidably connected to a connecting plate via a slider, the base plate is rotatably connected to a lead screw, and a height adjustment motor is provided to drive the lead screw to rotate, the lead screw and the connecting plate are connected by a lead screw nut; Rotary shaft mechanism: includes a rotary disk disposed at the bottom end of the connecting plate, and a vertical rotary shaft is fixed at the center of the rotary disk; Inclined shaft mechanism: The rotating shaft is fitted with a sliding sleeve, which is fixed to the rotating shaft by screws. A hinge plate is provided on each of the opposite sides of the sliding sleeve. One of the hinge plates is rotatably connected to a hinge shaft. The hinge shaft is fixed with a mounting sleeve for clamping a welding gun. The sliding sleeve is also provided with an inclination motor, and the output shaft of the inclination motor is fixedly connected to the hinge shaft. The skew shaft mechanism includes a rotary flange, and the base plate is connected to the Y-axis moving assembly through the rotary flange. Guiding device: On the other side of the sliding sleeve, the hinge plate is hinged to the second hinge shaft, the second hinge shaft is fixed to the first mounting plate, the first mounting plate is installed with a guiding unit through the elongated hole, the guiding unit is a laser sensor, the sliding sleeve is fixed to the guiding motor, the output shaft of the guiding motor is fixedly connected to the second hinge shaft, and the detection point of the guiding unit is located in front of the welding point; Anti-collision switch: On the other side of the sliding sleeve, the hinge plate is also fixed with a second mounting plate, and the second mounting plate is fixed with an anti-collision switch; Feedback Unit: The mounting sleeve is equipped with a feedback unit that follows the welding torch. The feedback unit is an encoder to provide real-time feedback on the X, Y, Z positions and θ and β angles of the welding torch.

5. The device for automatic welding of U-shaped weld seams according to claim 1, characterized in that: The control logic of the welding torch posture adjustment unit at the inflection point is as follows: Straight line segment: θ = θ0, where θ0 is a preset fixed angle of inclination, h = h0, where h0 is a preset fixed height; Circular transition section: θ is linearly adjusted from θ0 to θ1, θ1 = θ0 ± Δθ, Δθ ≤ 10°, h is compensated from h0 to h1, h1 = h0 - Δh, Δh is corrected in real time by arc voltage feedback, with a correction range of ±2mm.

6. The device for automatic welding of U-shaped weld seams according to claim 1, characterized in that: The X-axis moving component of the welding torch moving adjustment mechanism adopts rollers with gear and rack transmission, and the Y-axis moving component adopts linear rails with gear and rack transmission. It is driven by a servo motor, with a repeatability of positioning accuracy ≤ ±0.2mm and a maximum moving speed ≤ 1000mm / min.

7. The device for automatic welding of U-shaped weld seams according to claim 1, characterized in that: The control system further includes: The human-machine interface unit is used for parameter setting, status display, and fault alarm. The sensor module includes a travel limit switch, a home switch, an arc voltage sensor, and a temperature sensor; The storage unit is used to store at least 100 sets of welding programs and process parameters.

8. A device specifically for automatic welding of U-shaped weld seams according to any one of claims 1 to 7, characterized in that: The work includes the following steps: (1) Parameter input and trajectory generation: The user inputs the length L, width W, inflection point transition radius R and welding process parameters of the U-shaped weld, and the trajectory planning unit automatically generates a complete welding trajectory; (2) Workpiece clamping and zeroing: Place the workpiece on the positioning reference block, start the workpiece positioning and clamping mechanism to complete the clamping, and control the welding torch to move to the origin position. (3) Welding process execution: Start the welding program, the welding torch moves along the planned trajectory, and the straight segment is welded at a constant speed v; (4) Inflection point steering control: When the welding torch moves to the inflection point area, the motion control unit switches to the circular interpolation mode, and synchronously adjusts the speed of the X-axis and Y-axis, and the welding torch attitude adjustment unit corrects the welding torch tilt angle and height in real time; (5) Welding ends: After completing one cycle of welding, the welding torch returns to the origin, the workpiece positioning and clamping mechanism is released, and the welding process ends.

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