JP5041265B2 - Robot seam welding device having welding electrode shaping mechanism and welding electrode shaping method - Google Patents

Description

  The present invention relates to a seam welding apparatus using a robot, and more particularly, to a robot seam welding apparatus provided with a mechanism for shaping a welding electrode, and a method for shaping a seam welding electrode using the apparatus.

  In seam welding, a workpiece (hereinafter referred to as a workpiece) is pressed with a pair of disk-shaped welding electrodes, and the welding electrode is rotated while moving along the workpiece, and is continuously energized for welding. . Seam welding is suitable for joining containers that require airtightness, and is used, for example, in the manufacture of fuel tanks for automobiles.

In recent years, seam welding has been automated in combination with robots.
In this case, in order to perform seam welding on a large workpiece such as a car body of an automobile, it is very difficult for the robot to grip the workpiece from the viewpoint of the size and weight of the workpiece. In such a situation, it is necessary to mount a seam welder on the robot and cause the seam welder itself to follow the workpiece. As an example, an apparatus for performing wire seam welding by connecting a welding machine to a robot has been proposed (see Patent Document 1).
JP-A-9-234666

By the way, when such seam welding is repeated many times, the welding surfaces of both electrodes are worn and irregularities are generated, and the welding quality is deteriorated. Therefore, it is necessary to periodically shape the welding surface of the electrode by grinding or the like. Conventionally, the shaping work has been performed manually, but the finish varies from worker to worker and requires a great number of man-hours.
Therefore, a seam welding apparatus that automatically shapes an electrode has been proposed (see, for example, Patent Document 2). This is to attach a dressing mechanism equipped with a cutting tool for shaping, a means for moving the tool, a knurled driving roller that contacts the outer peripheral surface of the welding electrode and rotates at a constant peripheral speed to the welding machine. is there.
JP-A-11-309585

As described above, when a seam welder is mounted on a robot, the operator must enter the robot movement range in order to manually shape the electrodes. For this reason, in addition to the above-described problems, an electric circuit that performs safety measures unnecessary for welding work, such as cutting off the power of the robot during electrode shaping work, is required.
In addition, if the above-mentioned device that automatically shapes the electrodes is installed in the robot alongside the seam welder, the robot will become larger as the mass increases due to the installation of the device. The robot's movement will be restricted. Further, as the number of electrode shaping devices is increased, the number of wirings required for the movable part increases, and there is a problem that the possibility of disconnection increases and the cost increases due to the use of wiring with high bending performance.

An object of the present invention is to provide a robot seam welding apparatus that can safely shape an electrode of a seam welder mounted on a robot without enlarging the robot or restricting the operation.
Another object of the present invention is to provide a method capable of automatically shaping a welding electrode using the robot seam welding apparatus.

  Therefore, the present invention is equipped with a seam welding machine equipped with a pair of disk-shaped welding electrodes in an industrial robot, and moves the robot under the control of the robot control unit to sandwich the welding part of the workpiece with the welding electrodes, The electrode shaping mechanism is installed separately from the robot for a robot seam welding apparatus that rotates these welding electrodes and energizes them while moving along the welding trajectory of the workpiece to perform seam welding on the workpiece. This electrode shaping mechanism includes a shaping bit and a pressing means for pressing the shaping bit against the welding surface of the welding electrode. When shaping the welding electrode, the electrode is brought into contact with the shaping tool by the operation of the robot.

The shaping tool is preferably movably attached so as to protrude from the electrode shaping mechanism, and the pressing means is preferably a coil spring that presses the shaping tool. By adopting this configuration, by keeping the position of the welding electrode with respect to the electrode shaping mechanism constant, a constant pressing force is always applied to the shaping bite, and the welding surface of the welding electrode can be shaped accurately.
Also, it is necessary to change the rotation speed of the welding electrode during welding work and during electrode shaping, and the robot control unit operates with two speed command systems that differ in the welding electrode rotation speed during welding work and during electrode shaping. It is preferable to include a program.

The method of shaping a welding electrode according to the present invention automatically performs good electrode shaping using the above-described robot seam welding apparatus in consideration of wear of the welding electrode.
This method measures the amount of wear of the welding surface of the welding electrode to be shaped, and based on the measured amount of wear, the pressing means can apply a predetermined pressing force to the shaping bite with respect to the electrode shaping mechanism. Calculate the position, move the welding electrode to the calculated position by operating the robot, press the shaping tool against the welding surface of the welding electrode with a predetermined pressing force, rotate the welding electrode, This includes grinding and shaping the weld surface.

According to the present invention, the electrode shaping mechanism can be provided separately from the robot, and the seam welding electrode can be moved by the robot and brought into contact with the electrode shaping mechanism to perform the electrode shaping.
Therefore, it is not necessary to mount the electrode shaping mechanism on the robot, and the robot-mounted device is only a seam welding machine, which is lightweight and has a small capacity. As a result, electrode shaping can be performed safely, and the robot's seam welding device itself has good performance by suppressing the increase in the required payload of the robot and the restrictions on welding operations due to the size of the mounted equipment. Is possible.

Next, the present invention will be described based on the embodiments shown in the accompanying drawings.
FIG. 1 shows a robot seam welding apparatus according to an embodiment of the present invention. The apparatus includes an industrial robot 1, a seam welder 2, an electrode shaping mechanism 4, and a robot control unit 7 that controls the operation of the robot, the welding machine, and the electrode shaping mechanism.
The robot 1 is an articulated type, and a seam welder 2 is attached to the tip thereof.

  The seam welder 2 includes a pair of disk-shaped welding electrodes 3a and 3b arranged to face each other. The welding electrode 3a on the pressure side is movably attached and is provided with a pressure mechanism (not shown) composed of an air cylinder or the like. The welding electrode 3a is moved by the action of the pressurizing mechanism and presses against the welding electrode 3b on the receiving side. The welding electrodes 3a and 3b are further connected to separate motors, and rotate in opposite directions by driving the motors.

  The electrode shaping mechanism 4 includes a support stand standing on a reference floor common to the robot 1, and a pressing device 6 is mounted on the support stand. Furthermore, it has the shaping tool 5 movably attached to the pressing device 6. The pressing device 6 contains a coil spring, and the shaping tool 5 protrudes from the pressing device 6 by the pressing of the coil spring.

  As shown in FIG. 1, the robot control unit 7 includes an interface with a CPU for calculating the robot command position, the rotation speed of the seam welder electrode, etc., and a welder timer 8 for controlling the welding current when performing seam welding. I / O, RAM, nonvolatile memory, a robot body axis servo driver that drives the robot 1, an electrode axis servo driver that drives the electrodes 3a and 3b, and the like.

This robot control unit controls the operation of the robot 1, the seam welder 2, and the electrode shaping mechanism 4 as follows based on an operation program stored in advance.
In the welding operation, first, the robot 1 moves the seam welder 2 on the workpiece (not shown) on the workpiece gripping device installed on the above-described reference floor, and the welding portion of the workpiece is welded to the welding electrodes 3a and 3b. Position between. Next, the welding electrode 3a on the movable side is moved by the pressurizing mechanism, and the welding part of the workpiece is sandwiched between the welding electrodes 3a and 3b. In this state, the robot 1 moves the seam welder 2 along the welding trajectory of the workpiece, and the welding electrodes 3a and 3b rotate in accordance with the movement. At the same time, the workpieces are seam welded by energizing the welding electrodes 3a and 3b.
The configuration and operation of the above-described robot seam welding apparatus may be the same as the conventional one except for the improved portion according to the present invention, and further description thereof is omitted herein.

Next, welding electrode shaping work performed using the electrode shaping mechanism 4 will be described.
After the welding operation is completed, the seam welder 2 is disengaged from the workpiece. In this state, the robot 1 is operated under the control of the robot control unit 7, and the electrode 3 (electrode 3a or 3b) is moved toward the shaping tool 5 as shown in FIG. Press against. Next, the electrode 3 is rotated by driving the motor, and the welding surface is cut and shaped.
At this time, the force for pressing the shaping tool 5 against the welding electrode 3 is generated by the coil spring of the pressing device 6. By using the coil spring, the force for pressing the shaping tool 5 is determined by the position of the pressing device 6 with respect to the welding electrode. For this reason, it is possible to always perform shaping with the same force by keeping the position of the welding surface of the welding electrode and the pressing device 6 constant.

  FIG. 3 shows the shaping position of the electrode 3 in a state 9 where the welding electrode is new and a state 10 where the welding electrode is worn. The shaping position of the welding electrode 3 recorded in the operation program of the robot control unit is the position when the welding electrode on the upper side of FIG. In the state 10 in which the welding electrode is worn by an amount A with reference to this recording position, the position of the electrode 3 is moved to the pressing device 6 side by a distance B corresponding to the friction amount A, and the welding electrode is shaped.

The operation program of the robot control unit is set so that when the wear amount A of the welding electrode 3 is input, the position of the electrode during electrode shaping is automatically moved by the distance B.
Instead of this, for example, a known measuring device disclosed in Japanese Patent Laid-Open No. 11-28578 is provided, and robot seam welding is performed so that the wear amount of the welding electrode is detected and inputted in advance before the shaping operation is started. An apparatus may be configured. According to such a configuration, the welding electrode 3 can be automatically positioned with respect to the pressing device 6 during the shaping operation, and an accurate pressing force of the shaping bite 5 can always be obtained.

Note that the rotational drive of the welding electrode by the motor needs to have different speeds during the welding operation and the shaping operation.
Therefore, the robot control unit according to the present embodiment incorporates the program shown in FIG. 4 and changes the welding electrode rotation drive command method during welding and shaping operation. As shown in FIG. 4, when a welding operation is performed by providing two command systems of a robot synchronization speed and a designated speed for welding electrode shaping, the switch S <b> 1 is moved to the robot synchronization speed side, At the time of welding electrode shaping, the rotation speed of the welding electrode is switched by swinging to the specified speed side.

Specifically, four commands for welding start, welding end, shaping start, and shaping end are prepared as instructions for the robot operation program, and further a designated speed setting command is prepared.
The operation program executes the welding start command during the welding operation, thereby setting the switch S1 to the robot synchronous speed side and setting the switch S2 to the connected state. Using the robot synchronization speed of the robot controller as a command peripheral speed, it performs rotational speed calculated from the diameter of the current of a welding electrode in consideration of the wear amount and the speed, the welding electrode and inputs the result to the electrode control unit Rotate. At the end of welding, rotation of the welding electrode is stopped by executing a welding end command and opening the switch S2.

  At the time of shaping the welding electrode, the designated speed is stored in the designated speed storage unit by the designated speed setting command before the shaping is started. Subsequently, a shaping start command is executed, the switch S1 is set to the designated speed side, and the switch S2 is connected. Thus, the specified speed is used as the command peripheral speed, and the rotational speed is calculated in the same manner as during welding. At the end of shaping, an instruction to finish shaping is executed, and the rotation of the electrode is stopped by opening the switch S2.

As described above, since the speed stored in the designated speed storage unit is used during the shaping operation, the welding electrode can be rotated at a constant speed regardless of the operation of the robot. At the same time, as described above, the shaping tool 5 is pressed against the welding surface of the welding electrode 3a, thereby realizing a shaping operation at a constant speed and a constant pressure.
A similar operation is performed on the welding electrode 3b. With the above operation, the shaping of the welding surface can be completed for both welding electrodes.

  The present invention has been described based on the embodiments shown in the drawings. However, the present invention is not limited to this specific form, and various forms shown in the drawings can be made within the scope defined by the appended claims. It can be changed, or can take other forms.

The figure which shows the whole structure of the robot seam welding apparatus by embodiment of this invention. Schematic which expands and shows the motion of the welding electrode at the time of shaping work. Schematic which shows the positional relationship with the shaping tool at the time of shaping the worn-out welding electrode. The block diagram which shows the command system for switching the rotational speed of a welding electrode in the apparatus of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Robot 2 Seam welding apparatus 3a Pressurizing side welding electrode 3b Receiving side welding electrode 4 Electrode shaping mechanism 5 Shaping tool 6 Pressing device 7 Robot control unit A Electrode wear amount B (of welding electrode shaping position) moving distance

Claims (2)

A seam welding machine equipped with a pair of disc-shaped welding electrodes is mounted on an industrial robot, and the robot is moved under the control of the robot controller to sandwich the welded part of the workpiece with the welding electrodes and rotate these welding electrodes. , a robotic seam welding apparatus is energized while moving along the weld path of the workpiece performing seam welding the workpiece,
An electrode shaping device including a shaping tool and a pressing means for pressing the shaping tool against the welding surface of the welding electrode is installed separately from the robot, and the welding electrode is brought into contact with the shaping tool by the operation of the robot, The robot control device includes an operation program for instructing a rotation speed of a welding electrode, and has an operation program having two speed command systems for different welding electrode rotation speeds during welding work and electrode shaping. In the method of shaping the welding electrode with the robot seam welding device ,
Measure the wear amount of the welding surface of the welding electrode to be shaped,
Based on the measured amount of wear, calculate the position of the welding electrode relative to the electrode shaping device, where the pressing means can give the shaping tool a predetermined pressing force,
Operate the robot to move the welding electrode to the calculated position, press the shaping tool against the welding surface of the welding electrode with a predetermined pressing force,
A welding electrode shaping method comprising rotating a welding electrode and grinding and shaping a welding surface with a shaping bite . The method according to claim 1, wherein the shaping bytes attached to the movable to project from the electrode shaping device, the pressing means is a coil spring pressing the shaping bytes, shaping method of welding electrodes.

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