JPH079141A - Arc welding method by robot - Google Patents

Abstract

PURPOSE:To surely generate an arc without failure at the time of starting welding by executing teaching in such a manner that the parts exclusive of the bottom part in the gravity direction of a globule faces welding base metals at the time of starting the next welding. CONSTITUTION:The teaching is so executed that the part exclusive of the bottom part in the gravity direction of the globule 3b formed at the front end of a welding wire 3 at the ending time of welding faces the welding base metals 2 at the time of starting the next welding. The teaching is executed in order of, for example, vertical welding giving 20 deg. elevation angle to the welding torch 1, inclined position welding of 4 deg. torch angle with the base metals 2 inclined to about 30 deg., arc spot welding at 60 deg. torch angle with the base metals 2 inclined to about 45 deg., lap joint welding at 50 deg. torch angle, flat welding at 15 deg. torch angle, arm arc spot welding in a three o'clock position and flat welding. As a result, a series of the programmed welding operations are smoothly executed without interrupting the welding operations.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding method used by an arc welding robot to continuously weld a large number of welding spots in a memorized order in a manufacturing process such as an automobile. The present invention relates to an arc welding method capable of reliably performing an arc start at each welding location without failure and smoothly performing a series of welding operations without interruption.

[0002]

2. Description of the Related Art In the automobile manufacturing process, carbon dioxide arc welding is mainly used for arc welding in terms of adaptability to automation and the price of shielding gas, and is composed of a relatively thick plate. It is applied to the welding of front suspension members, rear axle housings, truck chassis frames, etc., and in many cases is fully automated by welding robots.

In carbon dioxide arc welding, since carbon dioxide forms a considerably strong oxidizing atmosphere in a high temperature arc, deoxidizing agents such as Si and Mn are added to the welding wire. It reacts with oxygen during welding to form SiO ₂ and MnO. These deoxidized products remain as slag on the surface of the weld bead or on the surface of the so-called molten ball that remains in the tip of the welding wire and solidifies without moving to the side of the object to be welded, which was melted by arc heat. become. Since these deoxidation products become insulating substances in the solidified state, when such deoxidation products are generated on the contact surface with the welding base metal at the tip of the welding wire at the start of the next welding, Since the arc between the welding wire and the base metal is obstructed, arcing does not occur, welding becomes impossible, and a series of welding operations are interrupted, which is extremely inconvenient for automatic welding on an automatic transfer line. Becomes

Therefore, conventionally, a scratch routine is provided to cope with such a situation, and when the arc start cannot be performed at a predetermined welding location, the welding torch is moved to a temporary welding location set separately, and the welding wire is moved. When the welding is carried out by rubbing the tip of the wire onto the temporary welding spot, and when arc start is still not possible, the tip of the wire is rubbed again and the deoxidized product is rubbed off from the surface of the molten ball formed on the wire tip. After that, the welding was resumed by returning to the welding location.

[0005]

However, in the scratch routine in the conventional welding method, the adhered portion of the deoxidized product of the molten ball formed at the tip of the wire and the scraped surface do not always match, If the welding is restarted without sufficiently removing the deoxidized products, the arc does not occur again, which causes a problem that the robot abnormally stops. Further, in order to completely remove the deoxidized product by matching the adhered portion of the deoxidized product with the scraping surface, it is necessary to change the angle of the welding torch or to sufficiently lengthen the rubbing distance. Not only that, if such a scratch routine is set for all welding spots of an automobile having many comparatively short welding spots, there is a problem that the working time becomes extremely long. Resolving the problems has been an issue in the arc welding process.

[0006]

SUMMARY OF THE INVENTION The present invention has been made by paying attention to the above problems in conventional arc welding using a welding robot, and without scratching the welding wire,
Provided is an arc welding method capable of reliably generating an arc at the start of welding at each welding point without failure and capable of smoothly executing a programmed series of welding operations without interruption. Is intended.

[0007]

In order to achieve the above-mentioned object, the present inventor diligently studied the generation site of the deoxidation product which hinders arc start, and as a result, it was formed at the tip of the welding wire at the end of welding. Paying attention to the fact that the deoxidation product generated on the surface of the molten ball has regularity in the place where the deoxidation product does not adhere to the welding robot at the start of welding. It has been found that by teaching so as to face the base metal, the arc start can be surely performed without failure.

That is, in carbon dioxide arc welding, a solid wire is used as a welding wire, and the deoxidizing agent such as Si, Mn, Al and Ti is contained in the welding wire as described above.

In a high-temperature arc, carbon dioxide partially decomposes into carbon monoxide and oxygen to form an oxidizing atmosphere for molten iron, so that the molten steel is oxidized in the arc to produce FeO. When it is produced and reacts with the deoxidizer, for example, SiO ₂ or MnO is expressed by the following formula.
A deoxidized product consisting of Si + 2FeO → (SiO ₂ ) + 2Fe Mn + FeO → (MnO) + Fe These deoxidized products float on the weld metal and remain as slag, while they are also formed on the surface of the molten mass at the tip of the welding wire. .

On the other hand, the arc column receives the maximum pressure at the discharge point (hereinafter referred to as the pole point) of the welding wire due to the pinch effect, a plasma airflow is generated, and the liquid deoxidation product formed on the surface of the molten mass is While being sucked toward the pole, the deoxidized product is likely to be formed around the pole because the temperature of the pole becomes the highest, and in any case, the deoxidized product is concentrated around the pole.

During welding, the molten mass is attracted to the base metal side by the arc force, and the pole point is also formed at the tip of the molten mass closest to the base metal. When the arc disappears, it solidifies while moving in the direction of gravity. As a result, the traces of poles and the deoxidized product move in the direction of gravity along with this, so that the deoxidized product does not depend on the welding torch angle at that time. Will always be formed at the bottom of the. Therefore, at the time of welding at the next welding point, if the robot is taught so that the peripheral portion of the pole mark does not come into contact with the base metal, an arc is surely generated and the welding can be smoothly started. .

The arc welding method by the robot according to the present invention is based on the above-mentioned knowledge, and a portion other than the bottom in the gravity direction of the molten ball formed at the tip of the welding wire at the end of welding is welded at the start of the next welding. The structure is such that teaching is performed so as to face the material, and such a structure of the arc welding method is used as means for solving the above-mentioned conventional problems. Further, as a concrete embodiment of the arc welding method by the robot according to the present invention, a configuration for determining the welding torch angle at the next welding according to the welding torch angle at the end of welding, depending on the welding torch angle at the end of welding Configuration that determines the welding sequence of each welding point,
Further, it is also possible to displace the forming position of the molten ball by rotating the welding torch in an appropriate direction immediately after the completion of welding or by performing dummy welding unrelated to a predetermined welding location after completion of welding. , Respectively as desired.

That is, in the arc welding method by the robot according to the present invention, depending on the welding torch angle at the end of welding, for example, the next welding after welding at the advancing angle may be performed at the receding angle, or the torch angle may be welded. After welding at 50 °, set the torch angle to -50 ° (tilt in the opposite direction)
By teaching like welding
Contact between the deoxidation product and the base material can be avoided.

Further, for example, after the horizontal welding or vertical welding with the welding torch in a horizontal or slightly upward position, a welding sequence is selected such that downward welding is performed with the welding torch in a downward position. By this, contact between the deoxidized product and the base material can be avoided and a good arc start can be obtained.

Further, in the case where the welding torch angle and the welding sequence cannot be freely set from the viewpoint of space and welding distortion prevention, for example, when downward welding continues,
Immediately after the end of welding, the robot's wrist is taught to swing up by 90 °, and the formation position of the molten ball is displaced by 90 ° with respect to the tip direction of the welding wire, thereby deoxidizing the product at the start of the next downward welding. It is possible to avoid contact with the base material.

Further, after the welding is completed, dummy welding is performed in a welding posture different from the welding posture,
The forming position of the molten ball can be displaced in a direction convenient for the next welding.

[0017]

In the arc welding method by the robot according to the present invention, a portion other than the bottom portion on the gravity direction side of the molten ball formed at the tip of the welding wire at the end of welding faces the welding base metal at the start of the next welding. By doing so, the contact between the deoxidation product and the base metal is avoided, and the deoxidation product, which is an insulator, does not interfere with the arc generation, and a series of programmed welding operations is performed. Will be executed smoothly without interruption.

[0018]

EXAMPLES The present invention will be specifically described below based on examples.

First, in a carbon dioxide arc welding robot having a 6-axis structure, an elevation angle of 20 ° is set from the horizontal position to the 7 locations shown in FIGS. 1 (a) to 1 (g), that is, the welding torch 1 shown in FIG. 1 (a). Vertical welding with a welding length of 12 mm according to the given posture,
Inclination welding with a welding length of 18 mm at a torch angle of 45 ° to the base material 2 inclined at about 30 ° shown in FIG.
Arc spot welding at a torch angle of 60 ° to the base material 2 inclined at about 45 ° shown in (c), lap joint welding at a torch angle of 50 ° shown in FIG.
The downward welding with a welding length of 8 mm at a torch angle of 15 ° shown in (e), the arc arc spot welding in a horizontal position shown in FIG. 1 (f), and the downward welding with a welding length of 15 mm shown in FIG. Teaching in order. Furthermore, immediately after the end of the downward welding shown in FIG. 1 (e) and immediately after the end of the downward welding shown in FIG. 1 (g), the robot's wrist is rotated in consideration of the welding posture to be performed next. Then, the teaching was performed so that the welding torch 1 was swung up to the horizontal position.

After confirming the normal welding by the test work, it was applied to the actual welding line and the welding of the work was repeatedly executed. As a result, good arc start was performed at any welding point, The desired welding could be performed in sequence without interruption of work.

The details of welding by the robot taught as described above will be described below step by step.

When the first work is loaded, first, as shown in FIG.
The vertical welding shown in (a) is performed. At this time,
As shown in FIG. 2 (a), the molten mass 3 a formed at the tip of the welding wire 3 is attracted to the side of the welding base metal 2 by the arc force, and the pole 4 (discharge point) is also generated during welding. Deoxidized product 5 in the molten state formed on the side closest to the material
Are also concentrated around the pole 4. The pole 4 is slightly concave due to the force in the direction opposite to the base material 2 due to the arc force, and when the molten mass 3a is solidified and becomes a molten ball 3b, as described below. Also in (1), the trace thereof is recognized as the minute recess 4a, and the trace of the pole can be confirmed by this.

When the arc is extinguished after the welding is completed, the molten mass 3a solidifies while drooping downward due to gravity as shown in FIG. 2 (b) to become a molten ball 3b. At this time, the deoxidation product 5 also moves together with the depression 4a which is the trace of the pole point 4, and solidifies at the bottom of the molten ball 3b on the gravity direction side to become an insulator.

Next, welding of the second welding portion shown in FIG. 1 (b) is started. At this time, the molten balls 3b and the deoxidized product 5 formed at the tip of the welding wire 3 are removed. As shown in FIG. 3A, the deoxidation product 5 is moving in a direction deviated by about 110 ° with respect to the tip direction of the wire 3. There is no contact with the material 2 and a good arc start is achieved.
Then, when this second welding is completed, the molten mass 3a similarly hangs down in the direction of gravity to form the molten ball 3b, and the recess 4a and the deoxidized product 5 are formed at the position shown in FIG. 3 (b). .

Then, the third welding point, FIG.
The arc-arc spot welding at a torch angle of 60 ° shown in (c) and the lap joint welding at a torch angle of 50 ° shown in FIG. Even at the start of welding, the deoxidation product 5 formed at the tip of the wire 3 is prevented from coming into contact with the base material 2 by changing the direction of the welding torch. It is not blocked by the object 5.

Next, downward welding, which is the fifth welding point shown in FIG. 1 (e), is started. Even when this welding is started, the deoxidation product 5 is formed at a position which is moved by about 50 ° with respect to the tip direction of the wire 3 by the previous welding, and therefore, as shown in FIG. Energization between the welding wire 2 and the welding wire 3 is not hindered, and a good arc start is achieved.

However, if the welding torch 1 is held at the same angle after completion of the downward welding, FIG.
As shown in FIG.
Is formed, and in the next horizontal arc spot welding shown in FIG. 1 (f), the deoxidized product 5 comes into contact with the base material 2, and it is predicted that the arc start will fail. Therefore, in this embodiment, as described above, the welding torch 1 is rotated and the teaching is performed so as to swing up to the horizontal position before the molten ingot 3a immediately after the end of the downward welding is solidified. Four
As shown in (c), since the molten ball 3b is displaced by about 90 ° with respect to the tip direction of the wire 3, it is removed at the start of the transverse arc spot welding shown in FIG. 1 (f), which is the sixth welding point. Since the acid product 5 does not come into contact with the base material 2, the lateral arc spot welding can be smoothly started.

Then, the seventh welding point is shown in FIG.
After performing the downward welding shown in (g), immediately after the end of welding, in preparation for the vertical welding which is the first welding point of the next work, the same welding as at the end of the downward welding which is the fifth welding point is performed. By rotating the torch 1 and swinging it up to a horizontal position, the molten ball 3b is displaced, welding of the work is completed, and the next work is prepared.

For example, in the case where the inclined welding shown in FIG. 1 (b) is continuous and the welding torch 1 cannot be rotated immediately after the welding is completed due to the space limitation, the preceding welding is performed. After completion, teaching may be performed so as to perform dummy welding in a horizontal or downward posture.

[0030]

As described above, in the arc welding method by the robot according to the present invention, the above-mentioned configuration, that is, the portion other than the bottom portion in the gravity direction of the molten ball formed at the tip of the welding wire at the end of welding is next welded. Since the teaching is performed so as to face the welding base metal at the start, an arc can be reliably generated without fail at the start of welding at each welding point, and a series of programmed welding operations is interrupted. It has an extremely excellent effect that it can be smoothly executed without being carried out.

[Brief description of drawings]

1A to 1G are explanatory views showing a welding sequence in which a robot is taught and a welding posture thereof in an embodiment of an arc welding method by a robot according to the present invention.

2 (a) is an explanatory view showing the shape of the tip of the welding wire during the vertical welding shown in FIG. 1 (a). (B)
It is explanatory drawing which shows the welding wire front-end | tip part shape after the end of the vertical welding shown in FIG.1 (a).

3 (a) is an explanatory view showing the positional relationship between the shape of the tip of the welding wire and the base material at the start of the second welding shown in FIG. 1 (b). (B) It is explanatory drawing which shows the welding wire front-end | tip part shape after completion | finish of the 2nd welding shown in FIG.1 (b).

4 (a) is an explanatory diagram showing the positional relationship between the shape of the tip of the welding wire and the base material at the start of the fifth welding shown in FIG. 1 (e). (B) It is explanatory drawing which shows the welding wire front-end | tip part shape on the assumption that the welding torch was hold | maintained at the same angle after completion | finish of the 5th welding shown in FIG.1 (e).
(C) It is explanatory drawing which shows the welding wire tip-end shape at the time of rotating a welding torch after completion | finish of the 5th welding shown in FIG.1 (e).

[Explanation of symbols]

 1 Welding torch 2 Welding base metal 3 Welding wire 3b Molten ball

Claims (5)

[Claims] 1. Arc welding by a robot, characterized in that teaching is performed such that a portion other than a bottom portion in the gravity direction of a molten ball formed at a tip portion of a welding wire at the end of welding is opposed to a welding base metal at the start of next welding. Method. 2. The arc welding method according to claim 1, wherein the welding torch angle for the next welding is determined according to the welding torch angle at the end of welding. 3. The method of arc welding by a robot according to claim 1, wherein the welding sequence of each welding location is determined according to the welding torch angle at the end of welding. 4. The arc welding method by a robot according to claim 1, wherein the position where the molten ball is formed is displaced by rotating the welding torch in an appropriate direction immediately after the welding is completed. 5. The method of arc welding by a robot according to claim 1, wherein after the welding is completed, the forming position of the molten ball is displaced by performing dummy welding unrelated to a predetermined welding location.