JP2006082089A - Method and apparatus for robot seam welding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for so called robot seam welding, by which method and apparatus, automatic seam welding can be carried out for a workpiece having large mass and volume. <P>SOLUTION: The robot seam welding apparatus includes an articulated robot 1, and a pair of rotary electrode rings 3a, 3b mounted on the robot 1. The seam welding for the workpiece is carried out by supplying the welding current to the electrode rings while gripping the workpiece 7 or 17 by means of the electrode rings and moving the electrode rings 3a, 3b by the robot 1 along a preliminarily indicated welding line 9 of the workpiece. Movable workpiece supporting tables 5, 6 are provided to move the workpieces 7 or 17 such that the welding line comes within the range of the welding operation of the electrode rings 3a, 3b. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method and an apparatus (hereinafter referred to as a robot seam welding method and apparatus) for performing seam welding on an object to be welded (hereinafter referred to as a workpiece) using an articulated robot, and is particularly too large to be gripped by a robot. The present invention relates to a robot seam welding method and apparatus suitable for mass and volume workpieces.

In seam welding, welding is performed by continuously applying a welding current between the electrode wheels while pressing the workpiece with a pair of rotating electrode wheels and moving the workpiece in accordance with the rotation of the electrode wheels. Such seam welding is suitable for joining containers that require airtightness, and is used, for example, in the manufacture of fuel tanks for automobiles.
As a means for automating the seam welding, there is a seam welding apparatus in which a stationary seam welder is provided with a robot for gripping a workpiece (see, for example, Patent Document 1).
JP 07-241684 A

  However, the robot cannot be applied to a workpiece having a mass exceeding the robot's transportable range or a workpiece having a length longer than the robot's arm, and a dedicated copying apparatus is required. For this reason, a workpiece fixing jig and a copying jig must be manufactured every time the shape of the workpiece is different. In particular, for the copying jig, a great amount of cost and time are required for manufacturing.

On the other hand, there is a wire seam welding apparatus in which a welding head including a pair of opposed rotating welding rollers is attached to a robot for the purpose of performing seam welding on the body of an automobile (see, for example, Patent Document 2). However, even with such a configuration, depending on the size of the workpiece, the arm of the robot cannot make the welding head take an appropriate posture.
As described above, in the conventional apparatus, it is difficult to weld all the welding lines of a large workpiece using one robot.
Japanese Patent Laid-Open No. 09-234466

  An object of the present invention is to provide a robot seam welding method and apparatus capable of performing automated seam welding even on a workpiece having a large mass or volume.

  In the robot seam welding method according to the present invention, a robot is configured such that a workpiece is sandwiched between a pair of rotating electrode wheels mounted on an articulated robot, and these electrode wheels are moved along a welding line of the workpiece to be taught in advance. While moving, seam welding of the work piece is performed by passing a welding current through the electrode ring. This method is characterized in that the workpiece is moved so that the welding line falls within the welding operation range of the electrode wheel.

  The robot seam welding apparatus according to the present invention includes an articulated robot and a pair of rotating electrode wheels mounted on the robot, and the electrode wheel is previously taught by sandwiching an object to be welded by these electrode wheels. While moving the robot so as to move along the welding line of the welded object, seam welding of the workpiece is performed by passing a welding current through the electrode ring. This apparatus is characterized in that a movable workpiece support table is provided for moving the workpiece so that the welding line enters the welding operation range of the electrode wheel.

  It is preferable that the workpiece is moved in synchronism with the movement of the robot during welding. By carrying out like this, the welding site | part of a to-be-welded object can be continuously put in the welding operation | movement range of an electrode wheel, and it can carry out continuously, without interrupting.

According to these methods and devices, the work piece is moved so that the welding line enters the welding operation range of the electrode ring by the articulated robot, so that the workpiece having a mass exceeding the robot's transportable mass or the length of the robot arm Automatic seam welding can be performed on a workpiece having the above length without using a dedicated copying apparatus required conventionally. Therefore, the welding work efficiency of this kind of work can be greatly improved.
Further, according to the present invention, various types of large and small workpieces can be set as work targets, so that a general-purpose robot / seam welding apparatus can be provided at a relatively low cost.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
FIG. 1 shows a robot seam welding apparatus according to an embodiment of the present invention. This apparatus has an articulated robot 1, a table 5 for supporting a workpiece 7, and a robot control unit 8 that controls the operation of this apparatus.

The robot 1 has a welding head 2 mounted on the arm tip. The welding head 2 includes a movable electrode wheel 3a, a stationary electrode wheel 3b that receives the movable electrode wheel, motors 4a and 4b that drive the electrode wheels, and a deceleration that connects these motors to the electrode wheel. And a drive shaft (not shown). In addition, the welding head 2 is provided with a pressurizing mechanism such as an air cylinder for performing a pressurizing operation for pressing the electrode ring 3a against the electrode ring 3b and sandwiching the welded portion of the workpiece 7, and the electrode ring 3a. Is connected to this pressure mechanism.
The welding head 2 is also provided with a welding transformer (not shown) for passing a welding current through the electrode ring, but this welding transformer may be provided outside the welding head. A welding machine (not shown) for controlling the welding current is stationary.

The table 5 is installed on the same base floor as the robot 1 and is rotatable under servo control. On the table 5 is mounted an XY table 6 that can be moved in the horizontal direction by servo control. The XY table 6 includes a fixture, and holds a workpiece 7 placed on the table.
In the present embodiment, two tables 5 and 6 are provided for supporting the workpiece 7. However, if it is not necessary for performing the welding operation, either the rotary table 5 or the XY table 6 may be omitted. Good. In addition, a table configured to tilt the workpiece 7 by rotating around an axis parallel to the foundation floor can be provided as a part of the support table.

  The robot control unit 8 incorporates an operation program taught in advance to the robot 1 and including welding conditions such as the movement path necessary for welding the workpiece 7, the positions of the tables 5 and 6, the welding portion of the workpiece 7, and the speed. The program is reproduced, and operation control is performed by issuing an operation command to the robot 1 and the tables 5 and 6.

Subsequently, the seam welding operation by the apparatus of this example will be described.
In this operation, the work 7 is moved by the rotary table 5 and the XY table 6 to a position where welding can be performed only by moving the arm of the robot 1, and welding is performed. For example, when the workpiece 7 is a quadrangle and the four sides are welded one by one, the robot control unit 8 first moves the robot 1 to a position for welding the first one side and starts welding on one side of the workpiece 7. Is positioned between the electrode wheels 3 a and 3 b of the welding head 2 mounted on the robot 1. Next, the electrode wheel 3a is pressed toward the electrode wheel 3b, and the welded portion of the workpiece 7 is sandwiched between these electrode wheels.

  When the clamping of the workpiece is completed, the control unit 8 starts to move the robot 1 so that the electrode wheels 3a and 3b move along the welding line on one side of the workpiece 7, and simultaneously starts to rotate the electrode wheels 3a and 3b. Simultaneously with the start of the operation of the robot and the electrode wheel, a welding signal and a welding condition signal are output to the seam welding machine to perform seam welding on one side of the workpiece 7.

When the electrode wheels 3a and 3b reach the welding end position, the robot control unit 8 turns off the welding signal and the welding condition signal, and stops the robot 1 and the electrode wheels 3a and 3b. Thereafter, the pressurization of the electrode wheel 3 a is stopped, the work 7 is released, the robot 1 is moved, and is retracted to a position that does not interfere with the operations of the rotary table 5 and the XY table 6. When the retraction of the robot 1 is completed, the control unit 8 turns the rotary table 5 by 90 degrees, and further moves the work 7 to a position within the operation range of the robot 1 by driving the XY table 6.
In this way, the workpiece 7 can be welded on the next side, and the apparatus resumes welding through the positioning operation of the electrode wheels 3a and 3b described above. Thereafter, the same work is performed on the remaining two sides of the work 7 to complete the seam welding of the work 7.

Next, a modified example of the above-described robot seam welding apparatus will be described.
In this modified example, the workpiece support table is also moved during the welding operation so that all the welded portions of the workpiece can be continuously seam welded. In this example, such a change is performed by the operation program of the robot control unit, and the components of the apparatus may be the same as those in the embodiment of FIG.
In the following description, only changes are extended, and the same reference numerals are used for the same components, and detailed description and illustration are omitted.

In the robot control unit 8 of this example, in order to register the physical positional relationship of the robot 1, the rotary table 5 and the XY table 6 in advance and maintain the welding locus taught to perform continuous seam welding. It is possible to calculate how the robot 1, the rotary table 5, and the XY table 6 should operate.
In this example, the weld line 9 on the peripheral flange of the workpiece 17 shown in FIG. 2 is seam welded. At this time, it is assumed that the welding operation possible range of the robot 1 is inside the dotted line 10.

In FIG. 3, the operation | movement condition at the time of welding work of the robot 1 of this example and the tables 5 and 6 is shown. Reference numeral 11 in the drawing indicates the position of the welding head 2 (the contact point between the electrode wheels 3a and 3b and the workpiece 17).
First, seam welding is started from the position of the work 17 at the upper left of FIG. 3, the robot 1 is operated, and the welding head 2 is moved in the X direction. Simultaneously with the movement of the robot 1, the XY table 6 is moved in the -X direction. As a result, the welding operation possible range 10 of the robot 1 moves along the welding site of the workpiece 17 as the welding progresses.
At this time, the welding speed is the movement speed of the robot 1 + the movement speed of the XY table 6. Since the robot control unit 8 also controls the XY table 6, only the welding speed is recorded when teaching the robot operation program. The moving speed of the robot 1 + the moving speed of the XY table 6 automatically becomes the welding speed.

When the first side of the workpiece 17 has been welded, the control unit 8 moves the welding head 2 in the Y direction while moving the robot arm as it is to change the posture of the welding head 2, and continues welding. Similarly to the welding in the X direction described above, when operating in the Y direction, the robot arm moves the welding head 2 in the Y direction and simultaneously moves the XY table 6 in the -Y direction. Thereafter, the same operation is performed on the remaining two sides of the workpiece 17, whereby the peripheral flange surfaces of the workpiece 17 can all be continuously welded at once.
In this example, only the XY table 6 is operated, but the rotary table 5 may be operated as appropriate according to the posture of the workpiece.

Thus, in addition to mounting a welding head on an articulated robot, by making the work support table movable, the mass and volume are large, making it difficult to apply conventional robot seam welding equipment. However, it is possible to automate seam welding.
The present invention has been described based on the embodiments. However, the present invention is not limited to these specific forms, and various modifications may be made to the described forms within the definitions described in the appended claims. Or the present invention can take other forms.

BRIEF DESCRIPTION OF THE DRAWINGS The figure which shows schematically the whole robot seam welding apparatus by the Example of this invention. The figure which shows the relationship between the welding operation range and the workpiece | work in the example of a change of the apparatus of FIG. The figure for demonstrating the operation | movement of the example of a change of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Articulated robot 2 Welding head 3a, 3b Electrode wheel 5 Rotating table 6 XY table 7, 17 Workpiece (workpiece to be welded)
8 Robot control unit 9 Welding line 10 Welding operation range 11 Welding head position

Claims (4)

The workpiece is sandwiched between a pair of rotating electrode wheels mounted on an articulated robot, and the welding current is passed through the electrode wheels while moving the robot so that these electrode wheels move along the weld line of the workpiece to be taught in advance. In the robot seam welding method for seam welding of workpieces,
A robot seam welding method characterized by moving an object to be welded so that a welding line falls within a welding operation range of an electrode ring.   The robot seam welding method according to claim 1, wherein during welding, a workpiece is moved in synchronism with the movement of the robot to perform continuous welding. It includes an articulated robot and a pair of rotating electrode wheels mounted on the robot, and the electrode wheel is moved along the weld line of the workpiece to be welded in advance by sandwiching the workpiece by these electrode wheels. In robot seam welding equipment that performs seam welding of workpieces through welding current through electrode wheels while moving the robot,
A robot seam welding apparatus comprising a movable workpiece support table for moving a workpiece so that a welding line falls within a welding operation range of an electrode ring. The apparatus according to claim 3, further comprising a control unit for controlling the operation of the robot and the support table, wherein the control unit moves the support table in synchronism with the movement of the robot during welding. apparatus.

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