JPH09253856A - Controller for profiling welding line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the profiling precision by emitting a signal when a welding torch is positioned at swinging both ends or the center of swinging, lowering or raising a welding voltage following to the signal and holding an arc length constant. SOLUTION: Welding is executed while swinging a welding torch. When the welding torch is passed through a center A of swinging, a compensating command voltage is added to a standard command voltage and the welding command voltage is raised. When the welding torch is passed through swinging both ends B, the welding command voltage is returned to the reference command voltage. When the welding torch is positioned at the swinging both ends, because the voltage is raised, an arc length is made constant. Because the arc length is constant, the current bias and the voltage bias of the welding torch are influenced only by the change of projecting length of a wire. This bias is detected and the locus of welding torch is corrected. The short-circuit at the swinging both ends is decreased and the occurred of spatter is reduced. The under-cut of a welding bead can be restricted and the quality of the welding bead is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding line tracing device which swings a welding torch in a groove width direction and follows a welding line by a current difference between both ends of the swing.

[0002]

2. Description of the Related Art Conventionally, as a welding line copying device, a method of swinging a welding torch in a groove width direction and utilizing a current deviation or a voltage deviation at both ends of the swing to make a trajectory correction is widely known. There is. This basic principle is based on the assumption that the arc length is constant at both ends of the swing and at the center of the swing, as shown in FIG. That is, the electrical change due to the change in the wire protrusion length is used as the information for correcting the locus of the arc sensor. This will be described with reference to FIG. As described above, as a correction method of the trajectory in the groove width direction, the deviation between the currents IL and IR at both ends of the swing, that is, IL-IR is used as the correction information source. As shown in FIG. 3C, when the welding torch is displaced to the right with respect to the welding line, I
The value of R becomes large. That is, IL-IR <0,
When this is detected, a correction signal is output to the left. On the contrary, as shown in FIG. 3B, when the welding torch is displaced leftward with respect to the welding line direction, the value of IL becomes large. That is, IL-IR> 0, and when this is detected, a correction signal is output to the right. As a correction method in the groove height direction, when the detected current value IC at the center of the swing or the average value (IL + IR) / 2 of the detected current values at both ends of the swing is larger than the set current value, the groove height is increased in the upward direction. Output a correction signal to.
Conversely, when the detected current value IC at the center of the swing or the average value (IL + IR) / 2 of the detected current values at both ends of the swing is smaller than the set current value, the correction signal is output downward in the groove height. It is to be noted that FIG. 3A shows a case where it is not displaced.

[0003]

However, in the conventional detection method, if the phenomenon of the arc length being constant is not established, the amount of change in current with respect to the amount of positional deviation is extremely reduced, resulting in erroneous detection or fluctuation. Since a short circuit is likely to occur at both ends, the detected current value includes a change amount of the short circuit current that is larger than the current change amount with respect to the original displacement amount, and correct correction information cannot be obtained. Generally, the arc length becomes constant when the oscillation frequency of the welding torch is low and is due to the self-control characteristic of the welding machine. The control action does not work and the arc length is not constant. As shown in FIG. 5, when the welding torch is swung at a high speed, the principle of constant arc length is no longer established, and the wire protrusion length is constant. For this reason, a short circuit is likely to occur at both ends of the swing, and therefore IL, which is a trajectory correction information source in the groove width direction, is generated.
Since the value of −IR fluctuates, the number of erroneous corrections increases.
Therefore, it is an object of the present invention to provide a device that can be controlled so as to reliably follow the welding line even when the oscillation frequency becomes high.

[0004]

In order to solve the above-mentioned problems, the present invention detects the electric change caused by the change of the arc length and the wire protrusion length by swinging the welding torch in the groove width direction. In a welding line tracing control device for causing the welding torch to follow the welding line by the detection signal, means for outputting a signal when the welding torch is located at both swing ends and swing center,
Means for receiving the output signal and changing the welding voltage.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of the present invention. At the start of welding, the voltage set by the command voltage setting device 14 is output from the command voltage output device 9 to the welding machine 1. At the same time, the command current set by the command current setting device 15 is output from the command current output device 10 to the welding machine 1. Welding is started under the above conditions, and an arc is generated between the welding torch 3 and the base material 4. The welding line copying device performs welding while swinging the welding torch 3 as shown in FIG. Further, the welding line copying apparatus removes the high-frequency component of the data detected by the current detector 5 by the low-pass filter 6, fetches it into the arithmetic unit 8 in the robot controller 2 through the A / D converter 7, and based on the data. The welding line. FIG. 2 shows the movement of the tip of the welding torch and the temporal change of the welding command voltage at that time. When the welding torch 3 approaches the swing center, a signal is output from the swing signal generator 11. In response to the signal,
When the welding torch 3 passes through the point A, the correction command voltage value set by the correction command voltage setting device 13 in advance is increased by the adder 12 in addition to the reference command voltage. After the welding torch 3 passes through both swing ends, the welding voltage command value is returned to the reference command voltage value at point B in FIG. With this control method, control with a constant arc length as shown in FIG. 4 can be performed, and stable and highly accurate welding line tracing can be performed.

[0006]

As described above, according to the present invention, the arc length becomes constant by increasing the voltage across the swing, and the welding line copying with high copying accuracy can be realized. Further, since the occurrence of short circuits at both ends of the swing is reduced, the occurrence of spatter is reduced, the undercut of the welding bead can be suppressed, and the quality of the welding bead is improved.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention.

FIG. 2 is an explanatory view of the operation of the present invention.

FIG. 3 is a diagram showing a correction principle of an arc sensor.

FIG. 4 is a diagram showing a welding state (arc length is constant) when the oscillation frequency is low.

FIG. 5 is a diagram showing a welding state when the oscillation frequency is high.

[Explanation of symbols]

1: Welder, 2: Robot controller, 3: Welding torch,
4: base material, 5: current detector, 6: low-pass filter,
7: A / D converter, 8: arithmetic unit, 9: command voltage output device,
10: Command current output device, 11: Oscillation signal generator, 12:
Adder, 13: Correction command voltage setting device, 14: Command voltage setting device, 15: Command current setting device

Claims (2)

[Claims] 1. A welding line tracing system in which a welding torch is swung in a groove width direction to detect an electrical change caused by a change in arc length and wire protrusion length, and the welding torch is made to follow a welding line by the detection signal. In the control device, the welding line is provided with means for outputting a signal when the welding torch is positioned at both ends of swing or at the center of swing, and means for receiving the output signal and increasing the welding voltage. Copy control device. 2. The welding line copying control device according to claim 1, wherein the increase of the welding voltage is such that, when the welding torch is located near both ends of the swing, the welding voltage is increased above a reference voltage for a set time. .