JPH0698491B2 - Rotational Position Control Method of Rotating Arc in Grid Fillet Welding - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for controlling a rotary position of a rotary arc when performing fillet welding of a grid-shaped member by a grid welding robot, and more specifically, a rotary arc welding method. The present invention relates to a rotation control method of a specific arc rotation position (here, referred to as C _f point) that serves as a reference of an arc sensor when welding a corner portion of a square-shaped member using.

[Prior Art] A grid welding robot for automatically performing fillet welding of grid-shaped members is known (Japanese Patent Laid-Open No. 64-15287), and the publication also describes grid fillet welding and rotary arc welding. A method of using the same and under the control of the groove copying by the arc sensor is described.

The groove profile control method by this arc sensor, as described in the above-mentioned publication or JP-A-62-248571, performs fillet welding while rotating the arc at a high speed, and at that time, the arc voltage. Or the welding current is detected, and the area for the same phase angle φ on the left and right centering on the forward point C _f of the arc rotation position from the detected arc voltage or welding current waveform
By integrating and comparing S _L and S _R , this is a method of correcting the position of the arc rotation axis on the welding line so that the difference becomes zero (see Fig. 8).

[Problems to be Solved by the Invention] However, since the conventional groove tracking control method using an arc sensor is based on the above-mentioned C _f point, if this control method is directly applied to a square welding robot, It was found that the C _f point deviated from the welding line during the turning motion at the corner of the die member, and accurate control could not be performed.

The present invention has been made in order to solve the above problems, and a method for controlling the rotational position of a rotating arc in square fillet welding, in which the C _f point at the corner of the square type member is controlled so as to always coincide with the welding line. The purpose is to provide.

[Means for Solving the Problems] In order to achieve the above object, a method of controlling the rotational position of a rotary arc in square fillet welding according to the present invention is performed by a square welding robot to which the rotary arc welding method is applied and an arc sensor is used. In fillet fillet welding, in which fillet welding of square type members is performed under groove profile control, while the square welding robot is performing a turning motion at the corners of the grid type members, turning is performed while detecting the turning angle. According to the angle, the front point C _f of the arc rotation position is rotated in the welding line direction, and the correction is performed so that the C _f point coincides with the welding line.

[Operation] The operation of the present invention will be described with reference to FIG. FIG. 1 is an explanatory diagram at the time of a turning operation of a square welding robot in a corner portion of a square type member. In the figure, 1 is a grid welding robot (hereinafter referred to as a robot), 2 is a welding carriage, 3 is a welding torch, 4 is a welding wire, 5 is a welding line, and 10 is a grid-shaped member that surrounds the horizontal plate 11 and its periphery. Stands arranged like 1
It is composed of 2,13. In addition, the upright plates corresponding to the other two sides of the horizontal plate 11 are not shown.

The robot 1 is installed on a horizontal plate 11 and continuously welds the fillets of the square-shaped member 10. The welding by the robot 1 is performed under the groove-following control by the arc sensor using the rotary arc welding method as described above.

Now, when the robot 1 moves, for example, from below in FIG. 1 and reaches the turning position A of one corner of the square type member 10, the welding carriage 2 stops moving and moves to the turning motion at that position. However, immediately before the start of the turning operation, the welding torch 3 faces the direction of the point B, and at this time, the forward point C _f of the arc rotation position is aligned with the welding line 5. However, pivoting in this state, since the C _f point comes off the weld line 5, in response to the turning angle theta (theta is detected by a rotary encoder or the like provided in the robot 1), rotating the C _f point Then, the welding line 5 is made to coincide with the correction. this
As is clear from FIG. 1, the correction of the rotation angle α at the C _f point is as follows.
When 0 ≦ θ <45 °, the arc may be rotated by −θ in a direction opposite to the arc rotation direction (negative direction). If 45 ° <θ ≤ 90 °, rotate by + (π / 2-θ). However, at corner position C (θ = 45 °) α = 90 °
And

Figure 2 shows the rotation angle α (correction amount) of the C _f point corresponding to the turning angle θ.
The control diagram of is shown. Therefore, the corner portion (BC-
In D), since the C _f point always coincides with the welding line 5, the groove profile control by the arc sensor at the corner is accurately performed,
Improves welding quality such as bead shape and leg length. Since the welding torch 3 controls the torch height so that the arc length is constant, the welding torch 3 expands and contracts with the turning motion. Also, the welding speed is controlled to be constant.

[Embodiment] FIG. 3 is a plan view showing an embodiment of a robot used in the present invention, and FIG. 4 is a front view thereof. Further, FIG. 5 is a sectional front view of the welding carriage portion, and FIG. 6 is a bottom view thereof. In these figures, the same symbols are used for the same elements as in FIG.

The robot 1 is provided with a welding carriage 2 and a welding torch 3 installed thereon, and by rotating the welding torch 3 by a rotating mechanism 16, a circular motion is given to the tip of the welding wire 4 to rotate the arc. ing. The rotational position of the arc with respect to the welding direction (C _f , R, C _r , L, see FIG. 8) is detected by an encoder 18 provided on a rotary motor 17 of the welding torch 3. The welding torch 3 is a Y-axis moving mechanism in the torch height direction.
The target position is controlled by 20 and the X-axis moving mechanism 24 in the groove width direction. 21 is a Y-axis motor, 22 is a Y-axis ball screw, and 23 is Y
The welding torch 3 is supported by the slide block 23 by a shaft slide block. 25 is an X-axis motor, 26 is an X-axis ball screw, 27 is an X-axis slide block, and the Y-axis moving mechanism 20 is supported by this slide block 27.

The welding carriage 2 includes a plurality of traveling wheels 28a and 28b and a plurality of ball casters 30, and the traveling wheels 28a and 28b are rotated by drive motors 32a and 32b, respectively, to travel. At the center of the welding carriage 2, an electromagnetic magnet 34 and a solenoid 35 for fixing and rotating the welding carriage 2 at the turning position A are provided. At the turning position A, the electromagnetic magnet 34 is lowered by the solenoid 35, and then the solenoid 35. Is excited to fix the welding carriage 2 with the electromagnetic magnet 34, and then the drive motor 32a,
32b are respectively driven to rotate in the opposite directions at the same speed, and the welding carriage 2 is rotated around the electromagnetic magnet 34 as the center of rotation.
The turning angle θ of the welding carriage 2 is detected by a turning angle detection sensor 36 by an encoder. The turning position A is detected by the turning position detecting sensor 38, which is a non-contact type distance sensor provided in the front portion of the welding carriage 2 in the traveling direction, and is a square-shaped member.
Rough copying of the straight line portion excluding the corner portion of 10 is performed by detecting the distance from the upright plate 12 by the laser sensors 40a and 40b provided in front of and behind the side portion of the welding carriage 2. Therefore, the welding carriage 2 itself moves somewhat zigzag in this straight line portion, but since the groove profile control is performed by the arc sensor as described above, there is no problem in terms of control of fillet welding. . In the figure, 42 is a control device, 43 is a welding power source, and 44 is a welding bead.

Next, FIG. 7 is a control block diagram applied to the method of the present invention. When a turning position signal is input from the turning position detection sensor 38 to the CPU 45 in the control device 42, the CPU 45 causes the left driving driver 46a and the right driving to operate. A stop signal is simultaneously output to the driver 46b to stop the left drive motor 32a and the right drive motor 32b at the same time. The CPU 45 also outputs an excitation signal to each 35, and lowers the electromagnetic magnet 34 to fix the welding carriage 2 at the turning position A. After that, the left drive motor 32a and the right drive motor 32b are rotationally driven in the opposite directions at the same speed. When the welding carriage 2 starts to turn around the electromagnetic magnet 34, the turning angle θ is detected by the turning angle detection sensor 36, and the signal is input to the CPU 45.

On the other hand, since the arc rotation position signal is input to the CPU 45 from the encoder 18 and the arc voltage and welding current waveform signals are input from the arc sensor 48, first, the turning angle determiner 49 determines whether the turning angle θ is smaller than 45 °. , Or is equal to this, and based on the result of the determination, the C _f point rotation compensator 50 corrects the rotation angle α of the C _f point as shown in FIG. In other words, the rotational position signal from the encoder 18 is relatively changed according to the turning angle θ, and when 0 ° ≦ θ <45 °, it is −θ minutes in the direction opposite to the arc rotation direction, and when θ = 45 °. When the arc rotation direction is 90 ° and 45 ° <θ ≦ 90 °, the rotation direction is corrected by + (π / 2−θ). Since the corrected C _f point coincides with the welding line 5 by this correction, the arc voltage integrator 51 and the welding current integrator 52 are respectively used for the predetermined phase angle φ with the corrected C _f point as a reference. The areas of the arc voltage waveform and the welding current waveform are integrated, and the groove tracing control is performed by comparing with the set values by the comparators 53 and 54, respectively.

When the turning operation of the welding carriage 2 is completed, the CPU 45 returns the solenoid 35 and the electromagnetic magnet 34 to the original positions by the operation opposite to the above by the input of the end signal, and also returns the turning angle detection sensor 36 to the zero point. At this time, since the C _f point coincides with the welding line 5 on the adjacent side, the welding line 5 can be made to follow the conventional manner by rotationally driving the drive motors 32a and 32b in the same direction at the same speed.

[Advantages of the Invention] As described above, according to the present invention, when the welding robot is turned in the corner portion of the square-shaped member, the reference C _f point of the arc sensor is always made to coincide with the welding line. Since the groove contour control of the corner portion is accurately performed by the arc sensor, the effect of significantly improving the welding quality can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory view showing the operation of the method of the present invention, FIG. 2 is a control diagram of a point C _f in the present invention, FIG. 3 is a plan view of a square welding robot for carrying out the method of the present invention, and FIG. FIG. 3 is a front view, FIG. 5 is a sectional front view of the welding carriage portion of FIG. 3, and FIG.
5 is a bottom view of FIG. 5, FIG. 7 is a control block diagram applied to the method of the present invention, and FIG. 8 is a principle diagram of a conventional arc sensor. 1 ... Grid welding robot 2 ... Welding trolley 3 ... Welding torch 4 ... Welding wire 5 ... Welding line 10 ... Grid-shaped member 16 ... Rotation mechanism 18 ... Encoder 36 ... Swing angle detection sensor 38 ... … Swivel position detection sensor 42 …… Control device 45 …… CPU 48 …… Arc sensor 49 …… Swivel angle determiner 50 …… C _f point rotation compensator 51 …… Arc voltage integrator 52 …… Welding current integrator 53 , 54 …… Comparator

Claims (1)

[Claims] 1. A square type fillet welding robot that applies a rotary arc welding method to fillet fillet a square type member under the control of a groove profile by an arc sensor, wherein the square type welding robot is a square type weld robot. While turning at the corner of the member, while detecting the turning angle, the forward point C _f of the arc rotation position is rotated in the welding line direction according to the turning angle, and the C _f point coincides with the welding line. A method for controlling the rotational position of a rotating arc in square fillet welding, which is characterized in that: