JPH0371983A - Method of detecting wear in back bar electrode - Google Patents

Abstract

PURPOSE:To improve accuracy of wear detection of an electrode and to shorten the working time by abutting contacting detector fitted to a welding robot arm on the reference position setting part to execute the reference value correction and comparing with contact position detected value of the back bar electrode. CONSTITUTION:In the welding method, which executes welding by holding a material to be welded between the back bar electrodes 15,..., 21 and the robot arm welding electrode, the contacting detector 41 fitted to the robot arm part 33 is abutted on upper face part 22a of the reference block 22 in the reference position setting part to execute correction of the reference value. On the other hand, by shifting the arm part 33 to moving course, the contact position detected value abutted on the back bar electrodes 15,..., 21 is recorded to execute comparison with the reference detected value. By this method, the wear condition of each electrode in the back bar electrodes 15,..., 21 can be detected with high accuracy under shortening the working time.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention provides the following features: when welding is performed by a welding robot,
The present invention relates to a back bar electrode wear detection method for detecting the wear state of a back bar electrode in which welding electrodes supported by a welding robot are opposed to each other with a workpiece to be welded between them.

(Prior Art) In an automobile body manufacturing line, various tasks are performed by industrial robots to mechanize or automate the body assembly process. As shown in JP-A-62-114778, welding work is carried out by a welding robot that supports a welding electrode and positions it at each welding site on the object to be welded. has been proposed.

When the welding robot performs welding work, the welding robot is taught in advance so that the movement path of the welding electrode supported by the welding robot is stored in the control unit for the welding robot. The welding robot is operated to move the welding electrode along a movement path stored in advance in the control section, and at this time, the welding electrode moves to each welding site on the body component of the welded object. Welding to the body constituent members is performed each time the body is positioned. The body components to be welded with the welding electrode supported by the welding robot in this way are held by, for example, a holder provided on the welding work base, and
Each welding site therein is brought into contact with a plurality of back bar electrodes disposed on the welding base. Then, the welding electrode supported by the welding robot faces the back bar electrode across the welding part of the body component, and a voltage is applied between the welding electrode and the back bar electrode, and Spot welding is performed on the welding site on the component.

(Problem B to be Solved by the Invention) As described above, welding electrodes sandwich the welding site on the body structural member and are opposed to the back bar electrode, and the spot is applied to the welding site on the body structural member. When welding is repeated, wear occurs on the back bar electrode, but when the back bar electrode becomes noticeably worn, there is a gap between it and the welding part of the body component member held by the holder provided on the welding work base. It will give rise to Then, when a gap is created between the welding site of the body component and the back bar electrode, the welding electrode supported by the welding robot is made to face the back bar electrode, and spot welding is performed on the welding site of the body component. If this is done, there is a possibility that a good spot welding state in the body constituent members may not be obtained.

Therefore, wear on each of the multiple back bar electrodes placed on the welding work base is detected, and for back bar electrodes with significant wear, the abutting surface part is repaired and then returned to normal condition. Adjustment is required to ensure proper position.

Detection of wear in each of the plurality of backbar electrodes required for such backbar electrode correction has conventionally been performed using a reference gauge corresponding to the normal height of each of the plurality of backbar electrodes on the welding base. is prepared in advance, and using such a reference gauge, the height of each back bar electrode on the welding work base is measured, and it is determined whether or not it has a height corresponding to the reference gauge. It is carried out by

However, when the back bar electrode wear detection method is performed by measuring the height of each back bar electrode on the welding work base using a reference gauge, it is difficult to detect the wear of each individual back bar electrode. The problem is that it requires a cumbersome height measurement work and a considerable amount of time, and therefore, when a large number of back bar electrodes are arranged on the welding work base, a large amount of work man-hours and time are consumed. Furthermore, there is a problem that variations occur in wear detection among a plurality of back bar electrodes.

In view of the above, the present invention has been developed to eliminate the troublesome task of detecting the wear state of each of a plurality of back bar electrodes, in which welding electrodes supported by a welding robot face each other with a workpiece to be welded between them. It is possible to easily and accurately carry out the detection without requiring any process and in a manner that avoids variations, and further to significantly shorten the time required to detect the wear state of all of the plurality of back bar electrodes. It is an object of the present invention to provide a method for detecting wear of a back bar electrode, which is capable of detecting wear of a back bar electrode.

(Means for Solving the Problems) In order to achieve the above-mentioned object, a back bar electrode wear detection method according to the present invention supports and moves a welding electrode that is opposed to the back bar electrode with a workpiece to be welded sandwiched between the back bar electrodes. A contact detector of a contact position detector attached to the arm of a robot equipped with an arm that is capable of contacting the reference position setting part is brought into contact with the reference position setting part, and the detection output value of the contact position detector at that time is determined. a step of revising the reference value for;
The robot moves the arm part according to a preset movement path, causes the contact detector of the contact position detector attached to the robot to sequentially contact each of the plurality of back bar electrodes, and determines the contact position. A step of recording a detection output value of a contact position detector obtained when a contact detector of the detector is brought into contact with each of a plurality of back bar electrodes, and a plurality of recorded back bar electrodes. The wear state of each of the plurality of back bar electrodes is detected by comparing the detection output value of the contact position detector for each of the electrodes with a reference detection output value for each of the plurality of puncture bar electrodes prepared in advance. It consists of steps.

(Function) In the back bar electrode wear detection method according to the present invention as described above, one specific task is, for example, to operate the control section of the robot to cause the robot to contact the contact point attached to the arm section of the robot. Performing an operation of bringing the contact detector of the position detector into contact with the reference position setting part, and correcting the reference value such as zero point setting for the detection output value of the contact position detector at that time, and controlling the robot controller. Operate the robot to move the arm according to a preset movement path, and prepare in advance the detection output value of the contact position detector for each of the plurality of recorded back bar electrodes. It is sufficient to compare the reference detection output value for each of the plurality of back bar electrodes, and the operation of sequentially bringing the contact detector of the contact position detector into contact with each of the plurality of back bar electrodes can be performed by the robot. For example, recording of the detection output value of the contact position detector obtained when the contact detector of the contact position detector is brought into contact with each of a plurality of back bar electrodes is also performed automatically. This is done automatically by the detector's auxiliary equipment.

Therefore, the wear state of each of the plurality of back bar electrodes can be easily and accurately detected in a manner that avoids variations. This will significantly reduce the time required.

(Example) FIG. 1 shows an example of a back bar electrode wear detection method installed in an automobile body production line, in which an example of the back bar electrode wear detection method according to the present invention is applied to detect the wear state of the back bar electrode. , shows a welding work station where spot welding to body components is performed.

In the welding work station shown in FIG. 1, a welding work base for assembling an underbody portion of an automobile body is arranged so as to be movable up and down. Eight support members 12a to 12h are provided on the welding work base 11 to support the underbody portion, which is the object to be welded, and the underbody portion is welded by these support members 12a to 12h. It is supported at a distance above the upper surface of the work base 11. In addition, in the center part on the welding work base 11,
A central back bar electrode placement stand 13 is provided, which is positioned below the underbody portion supported by the support members 12a to 12h, and has an outer surface portion that follows the shape of the central portion of the underbody portion, and further includes: A pair of side back bar electrode arrangement stands 14a and 14b are provided on both sides of the central back bar electrode arrangement stand 13, each having an outer surface that conforms to the shape of the left and right sides of the underbody portion.

A plurality of front back bar electrodes 15, 16. A middle back bar electrode 17 and rear back bar electrodes 18 and 19 are arranged.

These back bar electrodes 15.16, 17.18 and 1
9, the protruding length from the central back bar electrode placement table 13 can be adjusted, and when the protruding length is set to the normal value, the underbody portion supported by the supporting members 12a to 12h The welding member is brought into contact with a plurality of parts to be welded in the central part of the member from the lower surface side thereof. In addition, a pair of side back bar electrode placement tables 1
A pair of inclined back bar electrodes 20 and a pair of inclined back bar electrodes 21 are arranged on 4a and 14b, respectively, and these back bar electrodes 20 and 21 are also arranged on side back bar electrode arrangement stands 14a and 14b, respectively. The protrusion length from the underbody part 14b can be adjusted, and when the protrusion length is set to the normal value, the parts to be welded are placed on the left and right side parts of the underbody part supported by the support members 12a to 12h. It is assumed that the contact is made from the bottom side.

Further, a reference block 22 having a flat upper surface 22a is fixed at a position on the welding work base 11 behind the side back bar electrode arrangement stand 14a. The upper surface portion 22a of this reference block 22 is
The reference height position on the upper surface of the welding work base 11 is determined, and therefore, the reference block 22 is used as a reference position setting section.

A welding robot 30 is installed at a position adjacent to such a welding work base 11, with its body portion 31 fixed on a base 32. Body part 31
is rotatable about its vertical axis and also swings by its upper end.

It supports an arm portion 33 that is rotatable and extendable. A control device 34 is attached to the welding robot 30, and controls the rotation of the body portion 31 and the swinging of the arm portion 33 of the welding robot 30.

The rotation and expansion/contraction movements are controlled by operating the operating section 35 of the control device 34.

In FIG. 1, an electronic contact position detector 40 is attached instead to the tip of the arm 33 of the welding robot 30, but originally a welding electrode is attached. As the arm 33 moves, the welding electrode attached to the tip of the arm 33 is brought into contact with the welded part of the underbody supported by the support members 12a to 12h on the welding work base 11, and Place the back bar electrodes 15 to 2 between the parts to be welded.
It is assumed that the position is opposite to either one. Then, a welding voltage is applied between the welding electrode and any of the back bar electrodes 15 to 21 with the welding electrode sandwiching the part to be welded in the underbody portion and facing any of the back bar electrodes 15 to 21. Then, spot welding is performed on the welded portion in the underbody portion. When such spot welding is performed, the welding robot 30
The welding electrode supported by the arm member 33 is moved in a predetermined order to sequentially contact each of the plurality of welded parts in the underbody part supported by the support members 12a to 12h. A path is set, and a control program for the welding robot 30 for sequentially moving the welding electrode along the movement path is stored in a memory within the control device 34. Thereafter, the welding robot 30 is controlled by the control device 34 in accordance with the control program stored in the memory.
The welding electrode supported by the arm member 33 is brought into contact with each of the plurality of welded parts in the underbody part supported by the support members 12a to 12h in a preset order. shall be carried out.

As shown in FIG. 1, an electronic contact position detector 40 attached to the tip of the arm 33 of the welding robot 30 in place of the welding electrode has a contact detector 41 that is extendable and retractable. When the tip of the contact detector 41 is brought into contact with the object to be measured, the contact detector 4
For example, a digital signal is generated depending on the displacement of 1. The digital signal from the contact position detector 40 is
It is supplied to an output processing device 42 connected to the contact position detector 40, and in the output processing device 42, the contact position detector 4 is output based on the digital signal from the contact position detector 40.
A detection output of 0 is generated, and the value is displayed on the display section 43 and recorded on the recording paper 44. Further, the output processing device 42 is provided with a zero point adjustment operation section 45 for performing zero point adjustment of the detected output value of the contact position detector 40.

In order to detect the wear state of each of the back bar electrodes 15 to 21 according to an example of the present invention, first, the operating unit 35 in the control device 34 is operated to operate the welding robot 30. As shown in FIG. 2A, the tip of the contact detector 41 of the contact position detector 40 attached to the tip of the arm 33 is placed on the reference block 22 fixed to the welding work base 1. It is brought into contact with the upper surface portion 22a. Under such circumstances, the zero point adjustment operation unit 45 of the output processing device 42 connected to the contact position detector 40 is operated to adjust the value of the contact position detector 40 displayed on the display unit 43 of the output processing device 42. By setting the detection output value to zero, the contact position detector 4
The reference value for the detected output value of 0 is corrected.

Next, the operation section 35 of the control device 34 is operated again to cause the welding robot 30 to move its arm section 33 in a preset motion according to the motion control program stored in the memory built into the control device 34. The tip of the contact detector 41 of the contact position detector 40 attached to the tip of the arm 33 is moved along the path, for example, as shown in FIG. 2B. , sequentially abut on the upper surface of each of the front back bar electrodes 15 protruding from the central back bar electrode arranging table 13 provided on the welding work base 11, and then the central back bar electrode arranging table 13
The intermediate back bar electrode 17 and the rear back bar electrodes 18 and 19 are brought into contact with the upper surfaces of the intermediate back bar electrodes 17 and rear back bar electrodes 18 and 19, respectively, which protrude from the welding work base 11. A state in which the inclined back bar electrodes 20 and 21 are brought into contact with the upper surfaces of the electrodes 20 and 21 in sequence is automatically obtained. In this case, in the output processing device 42 connected to the contact position detector 40, the contact position obtained each time the contact detector 41 of the contact position detector 40 is brought into contact with each of the back bar electrodes 15 to 21. The detection output values of the detector 40 are sequentially recorded on the recording paper 44.

Subsequently, as shown in FIG. 2C, the output processing device 42 records on the recording paper 44 as described above.
The detection output value of the contact position detector 40 for each of the back bar electrodes 15 to 21 is recorded in advance on a recording paper 50 as shown in FIG. , the reference detection output value is the detection output value of the contact position detector 40 obtained when the contact detector 41 of the contact position detector 40 is brought into contact with them in a state where they are not worn. , thereby detecting the wear state of the back bar for each of the poles 15 to 21.

In this way, after correcting the reference value of the detection output value of the contact position detector 40, the arm section 33 is adjusted in advance according to the operation control program stored in the memory built in the control device 34 of the welding robot 30. Using the movement along the set operation path, the tip of the contact detector 41 of the contact position detector 40 is brought into contact with the upper surface of each of the back bar electrodes 15 to 21 in sequence, and By recording the detected output value of the contact position detector 40 obtained at that time, the wear state of each of the plurality of back bar electrodes 15 to 21 can be detected without requiring troublesome work. This means that it can be done easily without any problems.

(Effects of the Invention) As is clear from the above description, according to the back bar electrode wear detection method according to the present invention, a plurality of welding electrodes supported by a robot are opposed to each other with a workpiece to be welded sandwiched between the welding electrodes. For example, detecting the wear condition of the back bar electrode of
Operate the controller of the robot to cause the robot to bring the contact detector of the contact position detector attached to its arm into contact with the reference position setting part, and detect the detection output of the contact position detector at that time. calibrating the reference value for the value, operating the control unit of the robot to cause the robot to move the arm according to a preset movement path, and checking the recorded back bar electrodes. A mode in which variation can be easily avoided by simply comparing the detection output value of the contact position detector for each with a reference detection output value for each of a plurality of back bar electrodes prepared in advance. This can be carried out with high accuracy under the conditions of .

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a welding work station where the wear state of the back bar electrode is detected by applying an example of the back bar electrode wear detection method according to the present invention;
B and C are process diagrams for explaining an example of a method for detecting wear of a back bar electrode according to the present invention. In the figure, 11 is a welding work base, 15 and 16 are front back bar electrodes, 17 is an intermediate back bar electrode, 18 and 19
is a rear back bar electrode, 20 and 21 are inclined back bar electrodes, 22 is a reference block, 30 is a welding robot, 3
3 is an arm part, 34 is a control device, 40 is a contact position detector, 4 is a contact detector, 42 is an output processing device, 44 and 5
0 is a recording paper, and 45 is a zero point adjustment operation section.

Claims (1)

[Scope of Claims] A contact position detector attached to the arm of a robot is provided with an arm that can move while supporting a welding electrode that faces a welding electrode with a workpiece to be welded between the back bar electrodes. A contact detector having a contact position is brought into contact with a reference position setting section to correct a reference value for the detection output value of the contact position detector, and then the robot is caused to move the arm section along a preset movement path. The contact detector is moved according to the operation of sequentially bringing the contact detector into contact with each of the plurality of back bar electrodes, and the above obtained when the contact detector is brought into contact with each of the plurality of back bar electrodes. The detection output value of the contact position detector is set to be recorded, and then the recorded detection output value of the contact position detector for each of the plurality of back bar electrodes is recorded in the plurality of previously prepared detection output values. A back bar electrode wear detection method that detects the wear state of each of the plurality of back bar electrodes by comparing with a reference detection output value for each of the back bar electrodes.