JPS62240167A - Weld line profiling method in automatic welding - Google Patents

Abstract

PURPOSE:To save a labor in welding by performing the correction in the width direction of a weaving with the variation in the welding current at both ends of the weaving as the factor in weaving control to cope with the variation in the size of a groove. CONSTITUTION:In case of confirming the reach of a weaving end, the instantaneous current value IA is taken up, the mean value of the detection value for a certain cycles portion is calculated and this mean value IB and reference value (set value) IO are compared. If the mean value IB is smaller than the reference value IO, the torch is approached to a base metal and if larger, separated from the base metal. The control is thus performed so that the deviation of the mean distance of the torch from the reference distance becomes zero. The control is then performed by making the weaving width larger by a certain amount at the detection side if the instantaneous current value IA is found smaller than the value adding the prescribed constant (alpha) to the current mean value IB, and by making the weaving width smaller by a certain amount at the detection side, if larger, by comparing the instantaneous current value IA at the weaving end part with the current mean value IB for several cycles portion of the weaving. In this way the thickness in welding is made constant.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is particularly applicable to automatic welding of thick plates, in which the welding torch follows the welding line while controlling the weaving width according to fluctuations in the groove width. Regarding the method.

[Conventional technology]

In recent years, many automatic welding machines such as welding robots and microcomputer-controlled welding machines have come into use. One of the factors that determines the performance of this automatic welding machine is what kind of weld line copying device is used. Therefore, various proposals have been made in order to further enhance the functions of the copying device.

For example, there is a device in which a special sensor such as a magnetic sensor is attached to a welding torch, and the sensor performs welding while checking the position and orientation of the welding torch.
It is disclosed in Japanese Patent No. 27479.

The automatic welding machine has a magnetic sensor rotatably disposed on the coaxial circumference of a welding torch, and identifies a welding line based on a detection signal from the magnetic sensor.

Further, a method of using the welding arc itself as a sensation is proposed in Japanese Patent Laid-Open No. 181147/1983. This method detects welding current, welding voltage, wire supply speed, etc., calculates the sum of arc length and wire protrusion length from these detected values, and controls welding conditions to keep this value constant. 1. While weaving two welding torches, the detected or calculated values at the left and right ends, right half, and left half are compared, and the weaving center is controlled so that they are equal.

[Problem that the invention seeks to solve]

However, when a special sensor such as a magnetic sensor is attached to a welding torch, the area around the welding torch becomes large and heavy, and due to the performance of the sensor, the applicability is limited to bevels, grooves, etc. Ru.

On the other hand, the method of using the welding arc itself as a sensor detects the center of the groove and attempts to align the center of the weaving amplitude with this center. but,
With this method, the amplitude of weaving is constant, so when the width of the groove changes, such as when welding thick plates, the arc rides on the groove wall in the narrow part of the groove, causing undercuts 1 to 1. becomes. On the other hand, in a wide part of the groove, the arc does not reach the groove wall, and defects such as poor welding and slag entrainment are likely to occur.

In this way, conventional automatic welding methods perform welding while keeping the distance between the electrode and the workpiece (hereinafter referred to as arc length) constant, or follow the welding line along the horizontal direction (hereinafter referred to as arc length). (This is called weld line copying). For this reason, conventional automatic welding methods require welding in which the groove shape is approximately constant, such as one-pass welding, or two to three passes in which the groove is machined to maintain a uniform shape. It could only be applied to multi-layer welding.

However, when joining thick materials, it is necessary to perform multilayer welding using multiple passes. In this multi-layer welding, groove cutting accuracy is important.

The shape and size of the groove differs from place to place due to groove assembly accuracy, welding heat deformation, etc. Therefore, when using the conventional simple weld line tracing method, it is unavoidable that the groove wall is melted too much, resulting in undercuts and weld dripping, or conversely, poor weld penetration on the groove wall. Ta.

In order to solve this problem, which occurs especially when welding thick plates, it is necessary to detect changes in the shape and size of the groove.
There is a need for a device to control the welding torch in response to these changes, but a control device that satisfies this need has not yet been realized.

In view of these problems in the prior art, the present invention detects changes in groove shape and size such as groove width caused by groove cutting errors, groove assembly errors, welding thermal deformation, etc., and corrects the changes. Provides a groove tracing method that can be controlled accordingly,
The purpose is to fully automate welding work.

[Means for solving problems]

In order to achieve the object, the present invention uses a welding machine such as a welding robot that can arbitrarily control the position of the welding torch and welding conditions by a computer, and controls the arc length by weaving the welding torch in a direction across the welding line. While keeping the distance between the electrode attached to the tip of the welding torch and the workpiece constant, and controlling the weaving amplitude and welding speed according to the groove width, welding can be performed in the horizontal direction, such as in a horizontally downward position or in an upwardly moving position. When performing multi-layer welding on a joint that has groove walls on both sides, each layer is welded in one pass by weaving the welding torch in the horizontal direction without changing the welding torch angle with respect to the cross section of the groove, and each layer is welded for each predetermined number of times. One or both of the welding current and welding voltage during that time is detected, the average value is calculated, and the deviation amount between the average value and the preset reference value approaches zero (welding 1--chi position is controlled). The distance H1 between the electrode and the workpiece is kept constant, and the welding current at both ends of the weaving is maintained constant.

The detected value of one or both of the welding voltages is compared with a value obtained by adding a preset value to the average value, and the weaving amplitude and weaving center position are controlled so that the deviation amount approaches zero, and the weaving amplitude is adjusted. Detect, calculate and control the welding speed so that the welded lamination thickness per layer is constant, and calculate and control the weaving period from the welding speed and weaving amplitude so that the weaving pinotge is constant. It is characterized by

[Effect]

The current flowing between the welding torch tip and the surface of the base metal is affected by the resistance therebetween. For example, in the vicinity of the groove wall surface where the distance between the welding torch tip and the base metal surface in a downward position, that is, the arc length is short, the resistance decreases, and the resistance decreases due to the distance between the IJ welding torch tip and the base metal surface. The current flowing between the two increases. Furthermore, at the center of the groove, the distance between the welding torch tip and the surface of the base metal increases, and the current flowing between the welding torch tip and the base metal surface decreases accordingly. In this way, the amount of current flowing is different between the central part and the peripheral part of the groove. Furthermore, on the surface side of the groove in horizontal welding, the distance between the welding torch tip and the surface of the base metal becomes extremely large, so the current flowing there becomes small.

In the present invention, this change in current is used as a weaving control factor to correct weaving in the width direction.

FIG. 3 fal shows the relationship between the welding torch 1 and the groove 2 in a horizontal downward orientation when welding a groove whose both sides are wall surfaces. The welding torch 1 advances along the welding cotton while weaving. At this time, the current flowing between the welding torch 1 and the base metal is as shown in FIG.
At the ends, the arc length becomes shorter, so the number increases, and at the center of the groove 2, the arc length becomes longer, so it becomes smaller.

The welding device on which the present invention is based uses a computer-controlled robot or one with equivalent functionality. The welding method will be gas shield welding or non-gas welding, and if non-consumable electrodes are used, filler metal will be supplied separately. The weaving device may be of the simple vibration type, but it can be used as long as the angle of the torch does not change during weaving, the amplitude of the weaving per cycle, the stopping time at both ends, the weaving center position, etc. can be freely controlled during welding. .

Regulation? It is assumed that the a'Il device has the following three functions.

That is, firstly, welding current, welding voltage, and welding speed.

Weaving condition setting control ff11 function and function to detect both or one of welding current and welding voltage and calculate the average value for each weaving cycle.Secondly, the detected values at both ends of weaving and the average value for each weaving are A function to memorize a predetermined addend, calculate an average value, compare each value with a set value, and issue a signal depending on the magnitude, and thirdly, a function to control the center value and amplitude of weaving using this signal. It is to have.

Next, the groove to which the present invention is applied is a groove as shown in FIG.
Some butt joints, T-joints, inset joints, etc. in the groove in the upward and intermediate positions, and between each position and the horizontal position, and weaving in the horizontal direction with the welding torch. This is a groove that touches the groove wall surface on both sides along the extension line.

The detection signals of the present invention are welding current and welding voltage,
In order to sensitively detect changes in arc length, the welding current is mainly detected when a welding power source with constant voltage characteristics is used, and the welding voltage is mainly detected when a welding power source with constant current characteristics or drooping characteristics is used. However, the other one is either used as an auxiliary one or is not detected.

Weaving is performed horizontally so that changes in the groove shape can be clearly seen as changes in arc length, and at a constant angle with respect to the cross section of the groove. In the commonly seen uniaxial vibration, the arc length changes due to weaving, making it impossible to accurately detect the groove shape.

Lamination assumes that one layer is built up in one pass,
If the groove width is too wide than the maximum value of weaving amplitude,
Alternatively, when it is desired to limit the weaving width per pass to a small value in order to suppress welding heat input, one layer is divided into multiple passes.

In the present invention, since the main purpose is to control the weaving amplitude in accordance with fluctuations in the groove width, if the torch moves up and down within the weaving cycle, the groove wall cannot be detected as a fluctuation in the arc length.

Therefore, correction in the arc length direction is performed at the weaving end by calculating the average value for a plurality of weaving cycles at the weaving end. This makes the torch position control in the arc length direction somewhat insensitive and does not change during one cycle of weaving, making it possible to increase the detection accuracy of the groove wall surface.

Note that when the movement in the weaving direction is stopped for a certain period of time at both ends of the weaving, the arc length is at its shortest, and the time during which the detected value shows the peak value becomes longer.Therefore, the detection during this period is stopped, It is best not to include it in the average value calculation.

The method of detecting the groove wall surface, which is the most distinctive feature of the present invention, is based on weaving with a constant torch height in the horizontal direction.
This method takes advantage of the fact that the arc length changes according to the shape of the groove by moving the torch in the epping direction.

When detecting the welding current at both ends of the weaving, the detected value is compared with the average value plus a constant value, and when detecting the welding voltage, the detected value is compared with the average value plus a constant value. The relative position between the torch (arc point) and the groove wall is detected based on the magnitude of the comparison, and the amplitude of the weaving of the torch is controlled.

This makes it possible to respond not only to the conventional welding pattern but also to variations in the groove size, making it possible to greatly contribute to labor savings in welding.

However, the amount of correction of the weaving amplitude per time is set to a constant value that is not so large, and the amount of correction of the weaving center is set to 2 of the amount of weaving amplitude correction. by this,
Even if there are temporary fluctuations such as spatter adhesion or gas cutting notches on the groove wall, there will be no sudden change in the weaving conditions, so a stable bead can be obtained.

In addition, for areas where it is known in advance that the groove changes, such as points where the plate thickness changes, this point should be taught at the time of teaching the weld line, and this point will be recognized as a discontinuous point. Otherwise, there will be no inconvenience.

〔Example〕

The above will be explained in detail with reference to the drawings.

FIG. 1 shows a flowchart of the main routine of the welding program of the present invention, and FIG. 2 shows a flowchart of the subroutine. In the main routine shown in Fig. 1, first, prior to welding, weaving conditions such as welding current, welding voltage, welding speed, weaving amplitude, weaving period, and weaving both end stop time are set, then welding is started, and from this point Start detecting one or both of the welding current and welding voltage. This detection signal is converted into a digital signal and stored. Note that while weaving is stopped at both ends, it is better to stop detecting one or both of the welding current and welding voltage.

In the arc length control and weaving width control shown in the subroutine of Fig. 2, when it is confirmed that the weaving end has been reached,
Take in the instantaneous current value IA, calculate the average value of the detected values for a certain cycle, and calculate this average value ■8 and the reference value (set value)■
. Compare with. And the average value ill is the reference value ■. If it is smaller, the torch will be brought closer to the base material, and if it is larger, the torch will be pulled away from the base material. In this way, the deviation between the average torch distance and the reference distance is controlled to be zero. Next, the instantaneous current value rA at the weaving end and the average current value 1 for several cycles of weaving. If the instantaneous current value IA is smaller than the current average value I6 plus a predetermined constant α, the weaving width is increased by a certain amount on the detection side, and if it is larger, the weaving width is reduced by a certain amount on the detection side. Take control.

Thereby, even if the size of the groove changes, by controlling the weaving width accordingly, the weld thickness can be kept constant. In the subroutine of FIG. 2, the current reference value r is used when comparing the currents. Or constant α
By giving a width to the range, it is possible to suppress the hunting operation of the control.

〔Effect of the invention〕

As explained above, the present invention focuses on the fact that the welding current or welding voltage changes greatly between the center and the periphery of the groove, and uses this change in welding current as a factor for weaving control. The weaving will be corrected in the width direction. This eliminates the need to provide a device that detects changes in the shape and size of the groove, and a device that controls the welding torch in response to the changes. Furthermore, groove cutting accuracy is required when performing multi-layer build-up welding using multiple passes when joining thick materials.

Even if the shape and size of the groove differs from place to place due to groove assembly accuracy, welding thermal deformation, etc., excessive melting or undercutting of the groove wall or poor weld penetration of the groove wall may occur. Never. Therefore, it is possible not only to follow the conventional weld line but also to cope with variations in the size of the groove, which can greatly contribute to labor saving in welding.

[Brief explanation of drawings]

Fig. 1 is a flowchart 1-1 of the main routine of the welding control program of the present invention, Fig. 2 is a flowchart of the subroutine of the program, and Fig. 3 is an explanatory diagram showing the relationship between the welding torch and the groove in a horizontally downward position. It is.

Claims (1)

[Claims] 1. Using a welding machine such as a welding robot whose welding torch position and welding conditions can be arbitrarily controlled by a computer,
Weave the welding torch in the direction across the welding line,
While maintaining a constant distance between the electrode attached to the tip of the welding torch and the workpiece using arc length control, we control the weaving amplitude and welding speed according to the groove width, while maintaining a horizontally downward position and an upwardly moving position. When welding multiple layers of a joint that has groove walls on both sides in the equal horizontal direction, each layer is welded in one pass by weaving the welding torch in the horizontal direction without changing the welding torch angle with respect to the cross section of the groove. Detects one or both of the welding current and welding voltage for each weaving cycle, calculates the average value, and controls the welding torch position so that the deviation between the average value and a preset reference value approaches zero. The distance between the electrode and the workpiece is kept constant, and the detected value of one or both of the welding current and welding voltage at each end of the weaving is compared with the average value plus the preset value. The amplitude of the weaving and the center position of the weaving are controlled so that the amount of deviation approaches zero, the amplitude of the weaving is detected, and the welding speed is calculated and controlled so that the welding lamination thickness per layer is constant. , A weld line tracing method for automatic welding, characterized by calculating and controlling the weaving period so that the weaving pitch is constant from the welding speed and the weaving amplitude.