JP2002239732A - Weld line profile control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide such a weld line profile control method as exactly copies a weld line even if a weaving frequency is increased, and prevents an undercut from being caused on a base metal. SOLUTION: The weld line profiling control method which comprises a weaving position detecting means for detecting a weaving position of a welding torch, a feeding speed control means for variably controlling a feeding speed of a welding wire, and a feeding speed instruction output means for outputting a feeding speed instruction of the welding wire, in which positional information of the welding torch within a weaving section is obtained from the weaving position detecting means and thereby the feeding speed control means outputs a feeding speed instruction lower than an average wire feeding speed to the feeding speed instruction output means for a preset time when the torch is moving from the weaving center to the weaving edge, and in which the feeding speed control means outputs a feeding speed instruction higher than the average wire feeding speed to the feeding speed instruction output means for a preset time when the welding torch is moving from the weaving edge to the weaving center, is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding line tracking control method for following a welding line by weaving a welding torch in a groove width direction and detecting an electrical change.

[0002]

2. Description of the Related Art As a conventional welding line tracking control method, a method is known in which a welding torch is weaved in a groove width direction and a locus is corrected using a welding current deviation or a welding voltage deviation at both ends of the weaving. . Such a sensor that detects changes in welding current and welding voltage during welding and performs welding line tracking control is generally called an arc sensor.

[0003] The basic principle is limited to a method for detecting a welding line deviation in a groove width direction and a method for correcting a locus, as shown in FIG. The weld line deviation information of the groove width direction, the deviation of the welding current I _L and I _R of the weaving ends, i.e. I _L -
I am using the I _R. As shown in FIG. 2 (a), in the case where the welding torch is displaced in the left direction with respect to the weld line direction, the value of I _L increases. In other _words, I L _-I R> 0
Is detected and corrected rightward.

[0004] Also, as shown in FIG. 2 (c), if the welding torch is displaced in the right direction with respect to the weld line, I _R
Increases. _That, I L _-I R <0, and the
This is detected and corrected to the left.

The detection of the welding line deviation and the correction of the trajectory are performed every weaving cycle using the above-described basic principle. Therefore, if the weaving frequency of the welding torch is large, the number of times of detection and correction of the welding line deviation per unit time increases, and the ability to follow the welding line deviation is also improved. When the weaving frequency of the welding torch is low, as shown in FIG. 3, the arc length is secured at both ends of the weaving, and a short circuit hardly occurs. However, when the weaving frequency of the welding torch increases, as shown in FIG. 4, the arc length at both ends of the weaving becomes extremely short, so that the welding wire itself collides with the base material, and short-circuiting easily occurs.

[0006] short circuit weaving across smell occurs, the value of a weld line deviation information of the groove width direction I _L -I _R varies, the more the number of erroneous trajectory modification,
There is a problem that welding line scanning becomes unstable.

There is also a problem that the base material is liable to undercut, and when the undercut occurs, there is a high possibility that the base material does not cause serious defects such as a decrease in strength and cracks.

Therefore, when the weaving frequency is high, it is necessary to suppress the occurrence of short-circuits at both ends of the weaving in order to stabilize the welding line tracing and to prevent the occurrence of undercut of the base material. As a conventional technique for solving this problem, there is one disclosed in Japanese Patent Application Laid-Open No. 9-253856. In the technique disclosed in this publication, when the welding torch is positioned at both ends of the weaving, control is performed to raise the welding voltage above the reference voltage for a certain set time. In other words, by increasing the welding voltage at both ends of the weaving, the melting of the welding wire is promoted to thereby suppress a short circuit at both ends of the weaving.

[0009]

However, in the above-mentioned invention, if the welding conditions (welding current, welding voltage, etc.) are different, the amount of melting of the wire also changes. It has been difficult to find conditions for maintaining the protrusion length (arc length).

In order to maintain an appropriate arc length,
It was necessary to accurately grasp the amount of heat required to melt the welding wire by a predetermined amount and control the welding voltage. That is, if an appropriate welding voltage command value is not given, the welding wire is excessively melted and the protrusion length of the welding wire becomes too short, or the welding wire collides with the base metal because the amount of welding wire is insufficient. In some cases, the welding state becomes unstable, so that there is a problem that the profiling of the welding line becomes unstable.

Further, when the amount of fusion of the welding wire is insufficient, the problem that undercut occurs in the base material as described above has not been solved.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a welding line tracing control method that reliably follows a welding line even when the weaving frequency increases, and prevents the base material from being undercut.

[0013]

In order to solve the above problems, in the present invention, a welding torch is weaved in a groove width direction to detect an electric change accompanying a change in an arc length and a wire protrusion length. A welding line following control method for causing a welding torch to follow a welding line according to a detection signal, a weaving position detecting means for detecting a weaving position of the welding torch, a feeding speed control means for variably controlling a feeding speed of a welding wire, and welding. Feeding speed command output means for outputting a wire feeding speed command, and from the weaving position detecting means, obtaining position information in the weaving section of the welding torch, thereby moving the welding torch from the weaving center to the weaving end. Time, for a preset time, the feed speed control means controls the feed speed to be lower than the average wire feed speed. Is output to the feed speed command output means, and when moving from the weaving end to the weaving center, for a preset time, the feed speed control means causes the feed speed command to be higher than the average wire feed speed. The output is provided to the feed speed command output means.

Further, in the welding line scanning control method according to the present invention, the wire feed speed command is a control pattern of a rectangular wave or a sine wave.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a welding line scanning control method according to the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing an embodiment of a welding line scanning control method according to the present invention. 1 is a robot controller and 2 is a welding machine. The welding torch 3 is attached to a welding robot (not shown) and performs a weaving operation.
The base material 10 is welded. During welding, a welding current value and a welding voltage value are detected by a current detector 4 and a voltage detector 5, and high-frequency components are removed by low-pass filters 6 and 7, respectively, and digital values are removed by A / D converters 8 and 9. And the data is given to the calculation unit 11 in the robot control device 1.

The given data is subjected to various calculations in the calculation unit 11, and based on the results, the welding line scanning control is performed so that the center of the welding torch 3 coincides with the center of the welding line.

The feed amount of the welding wire to the base material 10 is controlled by the feed speed control unit 14 and the feed speed command output unit 1
2 outputs a wire feeding speed command to the wire feeding device 20. The present invention is characterized in that the weaving position is detected by the weaving position detector 13 and the wire feed speed is controlled by the feed speed controller 14 in synchronization with the weaving operation.

That is, when the welding torch 3 moves from the weaving center to the weaving end, a feeding speed command lower than the average wire feeding speed is output for a certain set time, and the welding torch 3 moves from the weaving end to the weaving center. At this time, a feed speed command higher than the average wire feed speed is output for a certain set time.

FIG. 5 shows an example of wire feed control which is a feature of the present invention.

FIG. 5 (a) shows the movement of the tip of the welding torch,
That is, it shows the weaving locus,
FIG. 5B shows the time change of the wire feed speed command at that time, and FIG. 5C shows the arc generation position.

When the welding torch 3 moves from the weaving center to the weaving end, as shown in FIG. 5 (b), the wire feed speed command outputs a value lower than the average feed speed command. The amount of the welding wire fed to the base material 10 decreases, the arc generating point increases from the point O to the point A, and the arc length increases, as shown in FIG. 5 (c). When the welding torch 3 moves from the weaving end to the center of the weaving, as shown in FIG. 5 (b), the wire feed speed command outputs a value higher than the average feed speed command. Then, the amount of the welding wire fed to the base material 10 increases, and as shown in FIG. 5 (c), the arc generating point falls from the point A to the point O, the arc length decreases, and the original arc length decreases. Return to arc length.

As described above, by controlling the wire feeding in synchronization with the weaving operation, the welding state shown in FIG. 3, that is, the welding state in which the arc length is secured at both ends of the weaving is maintained. In addition, a short circuit does not occur at both ends of the weaving, and stable and high-precision welding line profiling can be performed.

Further, since the arc length at both ends of the weaving is substantially equal to the arc length at the center of the weaving, the heat input to the base material becomes uniform and the penetration becomes uniform. That is, at both ends of the weaving, the base material is not dug down by the welding wire, and no undercut occurs in the base material.

FIG. 6 shows another embodiment of the wire feed control of the welding line scanning control method of the present invention. As shown in FIG. 6 (b), the wire feed speed command is changed in a sine wave shape. Even in this case, as described above, FIG.
As a result, a short circuit does not occur at both ends of the weaving, stable and high-precision welding line profiling can be performed, and no undercut occurs in the base material.

[0026]

As described above, according to the welding line scanning control method of the present invention, the wire feeding speed is controlled in synchronization with the weaving operation, so that no short circuit occurs at both ends of the weaving. . Thereby, welding profiling with high profiling accuracy can be realized.

Further, since the generation of spatter is reduced and the undercut of the weld bead can be suppressed, the quality of the weld bead can be improved.

[Brief description of the drawings]

FIG. 1 shows a schematic diagram of a welding line scanning control method of the present invention.

FIG. 2 shows a principle diagram of an arc sensor.

FIG. 3 shows a welding state when the weaving frequency is low.

FIG. 4 shows a welding state when the weaving frequency is high.

FIG. 5 shows an embodiment of a wire feed control method of the welding line scanning control method of the present invention.

FIG. 6 shows another embodiment of the wire feeding control method of the welding line scanning control method of the present invention.

[Explanation of symbols]

 1: Robot controller 2: Welding machine 3: Welding torch 4: Current detector 5: Voltage detector 6: Low pass filter 7: Low pass filter 8: A / D converter 9: A / D converter 10: Base material 11 : Operation unit 12: Feeding speed command output unit 13: Weaving position detecting unit 14: Feeding speed control unit 20: Wire feeding device

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yasuhiro Koga 2-1 Kurosaki Castle Stone, Yawatanishi-ku, Kitakyushu City, Fukuoka Prefecture Inside Yaskawa Electric Corporation (72) Inventor Haruki Nakajima 2-1 Kurosaki Castle Stone, Yawatanishi-ku, Kitakyushu City, Fukuoka Prefecture Yaskawa Electric Corporation

Claims (3)

[Claims] 1. A welding line tracing control in which a welding torch is weaved in a groove width direction to detect an electric change accompanying a change in an arc length and a wire protrusion length, and a welding signal is used to follow the welding torch to a welding line. In the method, weaving position detecting means for detecting a weaving position of the welding torch, feeding speed control means for variably controlling the feeding speed of the welding wire, and feeding speed command output means for outputting a feeding speed command for the welding wire. Has, from the weaving position detection means, by obtaining the position information in the weaving section of the welding torch, when moving from the weaving center to the weaving end, a preset time, by the feeding speed control means, Outputting a feed speed command lower than the average wire feed speed to the feed speed command output means; When moving from the end to the weaving center, for a preset time, the feeding speed control means outputs a feeding speed command higher than an average wire feeding speed to the feeding speed command output means. Welding line profiling control method. 2. The method according to claim 1, wherein the wire feed speed command is a control pattern of a rectangular wave. 3. The method according to claim 1, wherein the wire feed speed command is a sine wave control pattern.