JPS6133773A - Method for following up welding groove - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Field of Application of the Invention) This invention detects and integrates a welding current during arc welding, which is performed while swinging a welding torch supplying a consumable electrode in the groove width direction. The present invention relates to an improvement of a welding groove tracking method in which the welding torch is caused to follow the groove by comparing the integral values over a desired period.

(Prior art) When performing arc welding while swinging the welding torch that supplies the consumable electrode in the width direction of the groove, the width of the groove may be completely uniform depending on the workpiece finish. Due to the deformation of the workpiece due to heat as welding progresses, the groove width will fluctuate and become non-uniform even if forced by tacking or the like.

The welding current is detected while the welding torch is swinging in the groove width direction,
Even in the welding groove tracking method, which compares the desired oscillation period and makes the welding torch follow the groove, it is necessary to deal with the actual conditions of welding as described above. A technique for controlling the oscillation width of the welding torch with respect to fluctuations in
It has been published in Publication No. 8-176076, Japanese Unexamined Patent Publication No. 192681/1981, and the like.

However, it is also necessary to control the progressing speed in the groove direction, that is, the welding speed, including the groove width as described above, and it is necessary to control the wire protrusion from the output of the welding current detector and the output of the wire (consumable type Ti) feed speed detector. A device for calculating the length and detecting the groove width from its change pattern, and controlling the swing width and welding speed according to the change in the groove width was invented in JP-A-59-85.
It is published in Publication No. 375. Furthermore, when controlling the swing width and welding speed, the electrical work between the tip of the welding torch and the workpiece was also taken into consideration, as disclosed in Japanese Patent Laid-Open No. 59/1983.
-85376.

(Problem to be solved) By the way, in the above-mentioned arc welding, for example,
When welding from one end of the groove to the other end, the welding current setting is usually constant during this time, and therefore the wire feed speed is also constant, so detection of the wire feed speed is not necessarily necessary. . Therefore, it is desirable to control the swing width and welding speed in response to fluctuations in the groove width without detecting the wire feeding speed. The present invention focuses on these points, and provides a simple configuration that allows the swing width of the welding torch and the welding speed to be controlled in response to fluctuations in the groove width, without detecting the wire feeding speed. The present invention aims to provide a welding groove tracking method based on the following methods.

(Means for Solving the Problem) In the present invention, the integrated value of the welding current detection value of the 1/4 period from one end of the welding torch to the center of the oscillation is equal to the previous 1 of the oscillation on the same side. From the integral value of the welding current detection value of /4 period, it is calculated whether this integral value increases or decreases. That is, when arc welding like the second reverse is performed with the groove shape and swing path as shown in FIG. 3, the welding current detection value is as shown in FIG. 5,
For example, the integral value AND of the welding current detection value of 1/4 period Na in the N-th oscillation and the previous 1/4 period (N-1
) d welding current 11 Is it an increase from the integral value of the welding current detected value from the center of oscillation to the other end of the motion and the integral value of the welding current detected value of the previous 1/4 cycle on the same side? Calculate whether there is a decrease. Then, if each increases, it decreases so as to expand its amplitude. If so, calculate the amplitude to reduce the amplitude to find the swing width of the next swing. That is, the swing width lN+1 in FIG. 3 is calculated.

Next, when starting welding, a predetermined oscillation width according to the groove width of the workpiece to be welded is determined by instruction or a program, and the oscillation width is calculated by combining this predetermined oscillation width and the calculation. The welding speed at the next oscillation is calculated by comparing the values and increasing the welding speed when the oscillation width determined by the calculation is small, and decreasing it when the oscillation width is large.

Then, the welding torch is controlled using the swing width and welding speed thus obtained. The following steps are illustrated in Figure 1.

(Example) While swinging the welding torch T by the articulated robot R on the workpiece W having a horizontal V-groove G as shown in Fig. 2,
By comparing the integral values of the welding current detection values for 1/4 period of the oscillation on both sides of the oscillation center O8C, the welding torch T groove G
An example of a welding groove tracking method will be described in which welding is performed following the welding groove Bd to form a weld bead Bd.

In this embodiment, as shown in FIG.
．． Kei□□5.1. Ith (7) m 07 (D, 2° swing ■, 3rd swing ■... While swinging to Nth swing UJ■, welding speed VN every groove G D I will weld along with it.

Here, for the Nth swing, Na1 is the 1/4 period from the left end of the figure to the center of swing O8C, and Nb is the 1/4 cycle from the center of swing O8C to the right end of the figure.

NO for 1/4 cycle from the right end to the swing center O8C.

The 1/4 period from the swing center O8C to the left end is called Nd. Similarly, for the N-1st oscillation ΦEE) and the N+1Nth oscillation (EEE), each movement in the 1/4 period direction GD is performed by placing the welding torch T at the end of the final arm as shown in Fig. 4. This is done by controlling the joint angles α1 to α5 of the attached robot R.A consumable electrode E is fed to the welding torch T by a consumable electrode feeder R driven by a motor (not shown), and the consumable electrode EKI- 1: A welding current (2) is supplied from a welding power source 1 through a not-shown tip of a welding torch T.

A current sensor 2 is provided on the electrical wiring from the welding power source 1 to the welding torch T, and is connected to the bus 7 through the output cover of the current sensor 2, a low-pass filter 3, a sample hold circuit 4, an A/D converter 5, and a port 6. connected to. Connected to the bus 7 is a computer 8 which is composed of a known CPU, ROM, and RAM (not shown), and which contains a program related to this welding groove tracking, performs calculations, and stores the data. In addition, the bus 7 is connected to the servo circuits 10 to 1 for each joint axis of the robot R through the interface 9.
4 is connected. The current sensor 2 to the servo circuit 14 constitute a control device 15. The servo circuits 10 to 14 are connected to each joint angle α1 to α5 of robot R.
are connected to the α1-axis motor 16 to α5-axis motor 20, which control the α1-axis motor 16 to α5-axis motor 20, respectively.

This control device 15 samples the welding current value an appropriate number of times during each period (not shown) in which the oscillation period is appropriately divided during the oscillation, and calculates the average value. and input it into the microcomputer a as the welding current detection value Int for that period. By the way, when the welding torch T comes to one end of the oscillation, for example, the 1/4 period Na and 1/4 period Nb of the oscillation have ended, and A n & and 13nb obtained by integrating each with respect to time t are As shown in Figure 5. Then, subtract Bnb from Ana, calculate the position control amount of the swing center of the welding torch T as a function of the difference C, and use this result to calculate the drive amount of each joint axis of Robon) ReI Kai (1! The calculation is performed and output, and the interruption jY- ends.Then, the next swing starts, but this output causes the welding torch T to follow the groove G instead of swinging. During this time, welding is performed and the welding current is detected as described above. The procedure for this control is shown in FIG.

By the way, if an interrupt (2) occurs when calculating the oscillation width and welding speed of the N+1st oscillation EEE), as shown in FIG.
! 1!4 cycles (N-1) of the N-1st oscillation (EE) from the integral value ANa of the welding current detection value in the 4 cycles Na
], the integral values A(n-1) and d of the detected welding current values are subtracted to find the difference. When the difference is positive, the swing amplitude is calculated so as to expand the swing amplitude on the A side by a certain amount. When the above-mentioned difference is negative, the amplitude is calculated so as to reduce the amplitude on the A side by a certain amount.

Next, from the integral value BNC of the welding current detection value in the 1!4 cycles NO of the Nth oscillation ■, the same 1!4 cycles N T)
The integral value BNb of the welding current detection value at is subtracted, the difference is taken, and the amplitude on the B side is calculated as described above. Then, from the amplitude of each side, the next swing width lN+ is increased or decreased by a certain amount, that is, the N+1st swing EEEI)
] is calculated.

Then, it is compared with the predetermined oscillation IJ @ cleaning determined when programming the welding for this workpiece W, and on the other hand, the predetermined welding speed V determined when programming the welding.
Welding speed VN in case of N+1 oscillation from O to N+1
+1=VOX4N+]/lO is calculated.

The microcomputer 8 has these swing widths lN.
+1 and welding speed VN+1 as command values, these command values are used in the microcomputer 8 together with the position control amount C of the swing center of the welding torch T to control the robot R.
The drive uJ amount of each joint axis - ChiT is the N+1st swing EEI
), the motors 16 to 20 for each axis of the robot R are driven, and the welding torch T moves while following the groove G with a swing width and welding speed that takes into account variations in the width of the groove G, thereby creating an arc. By performing welding and repeating these calculations and controls, a weld bead BD with a uniform bulge height can be obtained even if the groove width varies.

(Other Examples) As another example, in calculating the above-mentioned swing width lN+1, the integral of the welding current detection value of 1!4 cycles before being compared with the integral value ANa or BNO of the welding current detection value The values may be limited to A, (n-1) (1,, Bn 1), respectively, and may be even earlier values, or may be the average value of the previous values.

In addition, when calculating the swing width lN+1, it is not only calculated by increasing it by a certain amount, but also the above-mentioned Ana −A (n
-1,), d, BNc, and -f3nb.

Also) divide Ana by A(n-11d, BNc4-Bnb, and when these ratios are 1 or more, increase the amplitude by a certain amount,
It is also possible to calculate the oscillation width as a function of these ratios.

In addition, when calculating the welding speed VN+1, IN+1/lO
It can also be found as a function of

In addition, groove tracking is not limited to the method of performing groove tracking by comparing the integral values of the welding current detection values of 1!4 periods on both sides of the center of oscillation. The groove tracking method that compares values can be widely used for groove tracking of grooves.

In addition, in the case of multi-layer arc welding, it can also be used for calculations during the welding of the first layer, and as a result, it becomes easy to make the final bead in the multi-layer welding a uniform height.

(Effects of the Invention) As described above, the present invention performs animate welding while swinging the welding torch that supplies the consumable electrode in the width direction of the groove, detects and integrates the welding current during the swing, and calculates the desired value by detecting and integrating the welding current. In this method, the welding torch is made to follow the welding groove by comparing these integral values for the period of This has the remarkable effect of controlling the welding speed and producing a weld bead of uniform height.

[BRIEF DESCRIPTION OF THE DRAWINGS] The drawings show an embodiment of the present invention, in which Fig. 1 is a schematic flow diagram, Fig. 2 is a schematic diagram, Fig. 3 is a schematic diagram, and Fig. 4 is a schematic diagram.
The figure is a block diagram, FIG. 5 is a schematic diagram, and FIGS. 6 and 7 are flow diagrams. In these drawings, E is a consumable electrode, T is a welding torch, G is a groove, W is a workpiece, O8 is a swing direction, IN+1 is a swing width, and VN+1 is a welding speed. Also, S1 to S3
2 is the step number.

Claims (7)

[Claims] (1) Arc welding is performed while the welding torch that supplies the consumable electrode is oscillated in the width direction of the groove, the welding current during the oscillation is detected and integrated, and these integrated values are compared for a desired period. In the welding groove tracking method, the welding torch is caused to follow the groove by, From the integral value of the welding current detection value of the previous 1/4 period of the oscillation from the oscillation center to the one end, this 1/4 is calculated for the next oscillation.
Calculate the amplitude of the oscillation to the same side as the oscillation of the period, and calculate the integral value of the welding current detection value of the 1/4 period oscillation from the oscillation center of the oscillation to the other end and the oscillation center. From the integral value of the welding current detection value of the previous 1/4 period of the oscillation on the side from The amplitude of the oscillation is calculated to calculate the oscillation width of the welding torch, and the oscillation width is compared with a predetermined oscillation width to calculate the welding speed at the next oscillation. The welding groove tracking method described above is intended to control the swing width of the torch in the groove width direction and the welding speed. (2) The oscillation width is calculated from the integral value of the welding current detection value of the 1/4 period of oscillation, and the integral of the welding current detection value of the previously performed 1/4 period of oscillation. When the difference is positive, the amplitude of the oscillation is increased by a certain amount, and when the difference is negative, the amplitude of the oscillation is decreased by a certain amount. A welding groove tracking method according to claim 1. (3) The oscillation width is calculated from the integral value of the welding current detection value of the 1/4 period of oscillation, which was performed previously, from the integral of the welding current detection value of the 1/4 period of oscillation. 2. The welding groove tracking method according to claim 1, wherein the welding groove tracking method is performed by subtracting values and calculating a function of the difference. (4) The calculation of the oscillation width is performed by integrating the welding current detection value of the 1/4 period oscillation and the previously performed welding current detection value of the 1/4 period oscillation. divide by the value,
A patent claim in which the amplitude of the oscillation is increased by a certain amount when the ratio is greater than 1, and the amplitude of the oscillation is decreased by a certain amount when the difference is less than 1. The welding groove tracking method according to item 1. (5) The calculation of the oscillation width is performed by integrating the welding current detection value of the 1/4 period oscillation and the previously performed welding current detection value of the 1/4 period oscillation. divide by the value,
The welding groove tracking method according to claim 1, wherein the welding groove tracking method is performed as a function of each ratio. (6) The welding groove tracking method according to claim 1, wherein the welding speed is calculated by dividing the calculated swing width by the predetermined swing width and multiplying by a predetermined welding speed. . (7) The welding speed is calculated by dividing the calculated oscillation width by the predetermined oscillation width and multiplying a function of the ratio by the predetermined welding speed. Welding groove tracking method.