JP3117374B2 - Automatic control of bead shape - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to automatic control of a bead shape which is suitable for controlling a finished bead shape of gas shielded arc welding and TIG welding and for controlling welding conditions adapted to a welding state. It is about the method.

[0002]

2. Description of the Related Art Conventionally, in the case of automatic welding, welding is performed in accordance with welding conditions set in advance, for example, welding conditions registered in a memory (floppy disk or memory card) for each pass / posture. As a result, if the set welding conditions match the welding conditions, the shape of the bead will be as desired.

[0003]

However, in general, when the groove shape is inaccurate on the gas cut surface, there is a setting error between the work and the device, or there is a distortion during welding, etc.
It is difficult to provide high quality welding under the same welding conditions. Therefore, a method of controlling the position of the welding torch along the groove line by using an arc sensor or image processing has been adopted. In addition to this, there is an example in which a groove width is sensed to control a weaving width and a welding speed to perform control corresponding to a change in the groove width. However, this alone did not sufficiently control the penetration of the bead into the groove surface, and could not completely prevent poor welding or blowholes. Accordingly, the present invention provides an automatic bead shape control method capable of performing high-quality welding without causing poor welding and blowholes, and aims to solve the conventional problems.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a gas shielded arc welding or TIG welding method in which a laser slit beam is irradiated immediately after welding and is imaged by an ITV camera provided with an interference filter of the same wavelength on the front surface. Then, obtain the inner shape of the groove immediately after welding by the optical cutting method, or scan across the groove with a laser displacement meter and similarly obtain the inner shape of the groove immediately after welding from the scanning position and depth data. The bead corner radius r with respect to the groove surface and the deviation angle θ between the bead surface and the tangent of the bead at the contact point (or break point) of the bead are determined as judgment variables (r, θ) as the wettability of the bead. The bead shape is controlled by changing the welding conditions such as the weaving width based on this, the weaving stop time at the groove wall, the current, and the welding speed. What to do It is.

[0005]

According to the present invention, a laser slit light having a wavelength of 600 to 800 nm emitted from a semiconductor which is small, lightweight, inexpensive and excellent in handleability is irradiated immediately after welding, and an interference filter of the same wavelength is arranged on the front surface. Using an image processing device to obtain the “inner groove shape immediately after welding” obtained by using an ITV camera or a laser displacement gauge and a scanning mechanism that scans across the groove, the cross-sectional shape inside the groove is a two-dimensional numerical value From the obtained information, the bead corner radius to the groove surface and the tangent of the bead at the contact point (or break point) between the groove surface and the bead are determined as the bead wettability. Welding conditions such as weaving stop time, current, welding speed, and the like at the part are changed so that high-quality welding that does not cause poor welding or blow holes can be obtained. In the same manner as described above, a laser slit light and an ITV camera or a laser displacement meter are arranged immediately before the welded portion, an image is taken immediately before the welded portion, and a standard welding condition set in advance is corrected from the shape thereof to obtain high quality. Welding is made available.

According to the present invention, it is possible to numerically determine the wet state of the bead on the groove surface.
That is, the radius of the bead corner with respect to the groove surface or the tangent of the bead at the contact point (or bend point) between the groove surface and the bead (hereinafter referred to as bead fold line), for example, the bead fold line has the same fold line direction as the groove surface Is determined as normal, and the welding conditions are left as they are. If the bead fold line enters the inside of the groove surface (the member meat side of the groove), it can be judged as undercut, and the current is reduced. On the other hand, if the bead tangent faces outward with a considerable angle compared to the value of the database with respect to the groove surface, it is regarded as insufficient wetting and the weaving width is widened or weaving on the wall surface of the groove Increase the current to increase the downtime. In addition, if the bead corner radius is small, it can be determined that the wettability of the bead is poor, and the current can be increased, the weaving width can be narrowed, or the weaving stop time can be lengthened. As described above, the present invention can numerically determine the wetting state of the bead with respect to the groove surface, change the welding conditions thereby, and provide high-quality welding that does not cause poor welding or blow holes. .

[0007]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a control apparatus for carrying out the present invention. In the figure, the visual sensor for gas shielded arc welding has a laser slit light source 2 and an ITV camera 3 before and after a welding torch 1.
The laser slit light 4 emitted from the laser slit light source 2 onto the welding member 7 can be imaged from obliquely above. The image from the ITV camera 3 is sent to the image processing device 8 and the cross-sectional shape of the groove such as the bead 12 in the groove surface 5 as shown in FIG. This image can be viewed through the TV monitor 9 (this is installed for confirmation and is not necessarily required for welding). Further, based on this data, the controller 10 controls welding conditions such as welding conditions of the welding power source 11 and weaving conditions of the weaving control shaft 6.

FIG. 2 is a diagram for explaining image processing contents to be processed by the image processing device 8. That is, FIG.
For example, an image obtained by irradiating a laser bead 4 with a bead below the V groove is shown. The image is obtained on the screen in XY coordinates in this way, and by binarization, a lit portion of the slit, that is, a groove cross-sectional shape is obtained. In this case, coordinate conversion is required, but since the following can be determined as relative, the conversion is not performed in the actual cross-sectional shape, and the description is omitted.) Eventually, thinning is performed,
N tables of one-stroke XY coordinates and P
(1) to P (n). Next, as shown in FIG. 2B, a contact point PL between the groove surface and the bead is obtained. First, the left and right ends BL and BR of the upper groove are detected as positions bent from the upper horizontal line (where the Y coordinate has changed). First, the bead on the left side will be described. A point distant by j from this position BL is defined as a start point P (i).
P (i−) that is separated by j before and after the point P (i)
j) and P (i), and the slope difference θ between the straight lines L1 and L2 connecting P (i) and P (i + j). The value of i is sequentially increased, and a point where the difference θ is larger than a preset value is determined as a bead breakpoint PL. Next, this break point P
P (i), P (i + k), P (p) are obtained from points 2k apart from k, which is slightly shorter than j as shown in FIG.
An arc C1 passing through three points (i + 2k) is obtained. This radius is obtained as a bead corner radius rb. Also, P (i)
Then, a straight line connecting P and i (k), that is, a bend line Lb of the bead is obtained, and θ is obtained from an angle formed by this and L1. In the case of the V groove, the bead corner radius r and the angle θ between the groove surface and the bead folding line Lb are obtained in the same manner for the right bead.

Next, an example of judging the bead shape from the angle difference θb of the bead folding line Lb and the bead corner radius rb will be described with reference to FIG. In FIG. 3A, since the bead corner radius rb is large and the bend line Lb to the groove surface is substantially equal, the wettability of the bead is good, it is determined that the bead is normal, and the welding conditions are not changed. To control. FIG. 3B is an example in which the bend line Lb of the bead enters the groove surface side and the angle becomes −θb. In other words, when θb has penetrated the groove side more than a preset value (a negative value is large), it can be determined that an undercut has occurred. In the data immediately after welding, the current is controlled to be low, the weaving width is reduced, the weaving stop time at the end is reduced, or the welding speed is increased to control the bead to be normal. If this is the data immediately before welding, the current is slightly lowered, the weaving width is slightly widened, or the weaving stop time is slightly lengthened to cover the penetration at the end. In FIG. 3 (c), the fold line Lb of the bead is greatly deviated from the groove surface, and the bead is raised and it can be determined that the bead overlaps. In the case of the data immediately after welding, the current is increased, the weaving width is widened, the weaving stop time at the end is lengthened, or the welding speed is increased to control the overlap so as not to overlap. In the data immediately before welding, the current at the end is increased to improve the penetration at the end, and the weaving stop time is slightly lengthened. FIG.
(D) is an example in which the bead corner radius rb is small. According to the data immediately before welding, if the bead corner radius rb is small, it can be determined that the bead wettability is poor, and the current is increased or the weaving width is widened. The bead corner radius rb with good wettability is controlled by elongating the stop time. In the data just before welding,
Increase the current slightly to cover the penetration at the end.

The welding conditions include a current, a weaving width, a weaving stop time, a welding speed, and other voltages. These are complicatedly involved, and what is controlled in which order and how much is changed. Means that a predetermined procedure is programmed. In particular, when sensors are arranged before and after welding, it is expected that data will be inconsistent before and after welding. In this case, generally, the immediately preceding data is prioritized, and the melting is performed normally first, and the value of the immediately subsequent data is set to a lower ratio.
This control can be controlled relatively easily by performing fuzzy inference. In this way, it is possible to provide high-quality welding that does not cause poor welding or blow holes due to the shape of the corner portion of the bead.

[0011]

As described in detail above, according to the present invention, the bead corner radius and the deviation angle between the groove surface and the bend line of the bead can be obtained from the cross-sectional shape of the bead. Conditions (current, weaving width,
By controlling the weaving stop time, welding speed, and the like, it is possible to provide an excellent effect that it is possible to provide high-quality welding that does not cause poor welding or blow holes.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a control device for implementing a bead shape automatic control method according to the present invention.

FIG. 2 is a diagram illustrating bead-shaped image processing according to the present invention.

FIG. 3 is a diagram illustrating a bead shape determination variable according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 welding torch 2 laser slit light source 3 ITV camera 4 laser slit light 5 groove surface 6 weaving control axis 7 welding member 8 image processing device 9 TV monitor 10 control device 11 welding power source 12 beads

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-176076 (JP, A) JP-A-62-254978 (JP, A) JP-A-60-118382 (JP, A) JP-A Sho 62-549 267071 (JP, A) JP-A-7-47471 (JP, A) JP-A-4-115104 (JP, A) JP-A-57-109575 (JP, A) JP-A-2-1510 (JP, A) JP-A-54-11861 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 9/095

Claims (1)

(57) [Claims] 1. In gas shielded arc welding or TIG welding, a laser slit light is irradiated immediately after welding, and an image of the laser slit light is taken by an ITV camera having an interference filter of the same wavelength arranged on the front side, and the laser light immediately after welding is obtained by a light cutting method. Either obtain the inner shape of the groove, or scan across the groove with a laser displacement meter and similarly obtain the inner shape of the groove immediately after welding from the scanning position and depth data, and then bead corner radius r to the groove surface And the deviation angle θ between the bead surface and the tangent of the bead at the point of contact (or breakpoint) of the bead with the judgment variables (r,
θ), and controlling the bead shape by changing the welding conditions such as weaving width, weaving stop time, current, welding speed, etc. on the groove wall based on this. Automatic control method.