Robot control device and spot welding system

Abstract

The present invention provides a robot control device and a spot welding system that are capable of roughening the surfaces of electrodes without requiring additional special devices or effort. The robot control device controls the operation of a robot that comprises a spot welding gun having a pair of electrodes positioned facing each other. The robot control device has a robot operation control unit that moves the pair of electrodes of the spot welding gun to a blade polishing position so that the surfaces of the pair of electrodes are polished by a rotating blade of an electrode polishing device. The robot control device changed the position of the pair of electrodes in contact with the blade from the polishing position so as to scratch the surfaces of the pair of electrodes after the polishing by the blade.

Description

Technical Field

[0001] The present invention relates to a robot control device and a spot welding system.

Background Art

[0002] Conventionally, it has been known to perform spot welding (resistance welding) by a robot equipped with a spot welding gun at the tip of an arm. The spot welding gun sandwiches a workpiece, which is an object to be welded made of a metal plate or the like, between a pair of electrodes, and performs spot welding at a predetermined dot by passing an electric current through the electrodes.

[0003] In recent years, aluminum alloys have been used as materials for weight reduction of automobiles. Since the surface of the aluminum alloy is covered with a film, it is known that a larger electric current is required during spot welding compared to a steel plate. When spot welding an aluminum alloy by passing a large electric current through the electrodes, the molten aluminum alloy adheres to the electrode surface and reduces the electrode life. In order to extend the electrode life, it is necessary to frequently polish the electrode surface. However, when polishing the electrode, it takes time to move the electrode to the position of the electrode polishing device and to perform the polishing, so frequent electrode polishing is a problem in shortening the welding operation.

[0004] Conventionally, as methods for extending the electrode life, a method of roughening the electrode surface (see, for example, Patent Documents 1 and 2), a method of forming concentric ridges on the electrode surface (see, for example, Patent Document 3), and the like are known. According to these methods, the molten aluminum alloy is less likely to adhere to the electrode surface, and frequent polishing of the electrode surface can be avoided.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

[0006] However, the above conventional method requires special equipment and labor because it uses a dedicated cutter or a file to roughen the surface of the electrode. Therefore, there is a need to roughen the surface of the electrode without adding special equipment or labor. MEANS FOR SOLVING THE PROBLEM

[0007] One aspect of the robot control device of the present disclosure is a robot control device that controls the operation of a robot including a spot welding gun having a pair of electrodes arranged opposite to each other, and moves the pair of electrodes of the spot welding gun to a polishing position by a rotating blade portion of an electrode polishing device so as to polish the surfaces of the pair of electrodes. The robot operation control unit has a robot operation control unit that changes the positions of the pair of electrodes in contact with the blade portion from the polishing position so as to damage the surfaces of the pair of electrodes after polishing by the blade portion.

[0008] One aspect of the spot welding system of the present disclosure includes a spot welding gun having a pair of electrodes arranged opposite to each other, a robot that moves the spot welding gun, an electrode polishing device that polishes the surfaces of the pair of electrodes with a rotating blade portion, and a robot control device that controls the operations of the robot and the electrode polishing device. The robot control device has a robot operation control unit that moves the pair of electrodes of the spot welding gun to a polishing position by a rotating blade portion of the electrode polishing device so as to polish the surfaces of the pair of electrodes. The robot operation control unit changes the positions of the pair of electrodes in contact with the blade portion from the polishing position so as to damage the surfaces of the pair of electrodes after polishing by the blade portion. EFFECTS OF THE INVENTION

[0009] According to one aspect, it is possible to provide a robot control device and a spot welding system that can roughen the surface of an electrode without the need to add special devices or labor.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

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Figure 8

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Figure 12

Modes for Carrying Out the Invention

[0011] Hereinafter, a robot control device and a spot welding system according to an embodiment will be described in detail with reference to the drawings. FIG. 1 shows a schematic configuration diagram of a spot welding system according to an embodiment. FIG. 2 shows a block diagram of a spot welding system according to an embodiment.

[0012] The spot welding system 1 includes a robot 2 having a spot welding gun 3, an electrode grinding device 4, a robot control device 5, and a teaching operation panel 6.

[0013] The robot 2 is a vertically articulated robot having a plurality of joint parts. The robot 2 has a base 21 installed on the floor surface and a turntable 22 rotatable around an axis extending in the vertical direction. The robot 2 has a lower arm 23 supported by the turntable 22 and rotatable, an upper arm 24 supported at the tip of the lower arm 23 and rotatable, and a wrist part 25 rotatably supported at the tip of the upper arm 24. The robot 2 has a plurality of robot drive motors 26 that individually drive the turntable 22, the lower arm 23, the upper arm 24, and the wrist part 25. When the robot drive motors 26 are driven respectively, the position and posture of the robot 2 change.

[0014] Note that the robot is not limited to the above form. The robot may be any robot capable of changing the position and posture of the spot welding gun 3.

[0015] The spot welding gun 3 is attached to the wrist part 25 of the robot 2. The position and posture of the spot welding gun 3 are changed as the position and posture of the robot 2 change. The spot welding gun 3 includes a pair of electrodes including a movable electrode 31 and a counter electrode 32 arranged to face the movable electrode 31, and an electrode drive motor 33 that drives the movable electrode 31.

[0016] The movable electrode 31 and the counter electrode 32 of the present embodiment are substantially cylindrical. As shown in FIG. 5, the tips of the movable electrode 31 and the counter electrode 32 have R portions 31a and 32a with rounded outer peripheral corners and tip surfaces 31b and 32b formed of flat surfaces. The central axes Y of the movable electrode 31 and the counter electrode 32 coincide. The movable electrode 31 moves in directions approaching and separating from the counter electrode 32 by driving of an electrode drive motor 33. The spot welding gun 3 applies a voltage between the movable electrode 31 and the counter electrode 32 in a state where a workpiece (not shown), which is an object to be welded, is sandwiched between the movable electrode 31 and the counter electrode 32 to perform spot welding. As the workpiece, an aluminum alloy or a metal containing an aluminum alloy can be preferably used.

[0017] The electrode grinding device 4 is generally called a tip dresser. In the electrode grinding device 4, "grinding" is interpreted broadly and includes, for example, grinding (removing process) by a cutter (blade portion 42) within the range treated as "grinding" in the electrode grinding device 4. The electrode grinding device 4 is installed on the floor surface where the robot 2 is installed and within the movable range of the robot 2. The electrode grinding device 4 has a main body portion 41 provided with a blade portion 42 for grinding the movable electrode 31 and the counter electrode 32 of the spot welding gun 3, and a support member 43 erected in the vertical direction. The support member 43 supports the main body portion 41 at a predetermined position. A bracket 44 is fixed to the support member 43. Springs 45 are respectively arranged above and below the main body portion 41. The springs 45 are provided so as to extend and contract in the vertical direction. The main body portion 41 is supported by the bracket 44 via the springs 45. The main body portion 41 is movable freely in the vertical direction by the elastic force of the springs 45.

[0018] The main body portion 41 of the electrode grinding device 4 is provided so as to project laterally from the bracket 44 toward the support member 43. The blade portion 42 is arranged at an end of the main body portion 41 far from the bracket 44. The blade portion 42 is a cutter for grinding the surfaces of the movable electrode 31 and the counter electrode 32 of the spot welding gun 3. As shown in FIGS. 3 to 5, the blade portion 42 is supported by a cutter holder 420. The cutter holder 420 having the blade portion 42 is arranged inside a through hole penetrating the main body portion 41 in the vertical direction.

[0019] The cutting edge 42 of this embodiment is arranged from the upper shoulder 421 and the lower shoulder 422 of the cutter holder 420 to the rotation axis X. The cutting edge 42 is provided one by one on the cutter holder 420 corresponding to the movable electrode 31 and the counter electrode 32. The cutting edge 42 has a curved shape following the tip shapes of the movable electrode 31 and the counter electrode 32. As shown in FIG. 5, when the cutting edge 42 contacts the surfaces of the movable electrode 31 and the counter electrode 32 for polishing, it extends radially from the central axis Y of the movable electrode 31 and the counter electrode 32 along the tip surfaces 31b, 32b and the R portion 31a. The cutter holder 420 rotates about the rotation axis X extending in the vertical direction by the drive of the cutting edge drive motor 46 provided in the main body 41. The central axis Y of the movable electrode 31 and the counter electrode 32 during polishing coincides with the rotation axis X. As shown in FIG. 5, the cutting edge 42 simultaneously polishes the respective surfaces of the movable electrode 31 and the counter electrode 32 arranged opposite to each other by the rotation of the cutter holder 420.

[0020] The robot control device 5 controls the operations of the robot 2, the spot welding gun 3 provided on the robot 2, and the electrode polishing device 4, respectively. The robot control device 5 is composed of an arithmetic processing device having a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), etc., which are connected to each other via a bus. The robot 2, the spot welding gun 3, and the electrode polishing device 4 are electrically connected to the robot control device 5 via a communication device.

[0021] As shown in FIG. 2, the robot control device 5 has a storage unit 51 that stores information regarding the control of the robot 2, the spot welding gun 3, and the electrode polishing device 4, respectively. The operation programs regarding the operations of the robot 2, the spot welding gun 3, and the electrode polishing device 4 are stored in the storage unit 51. The operations of the robot 2, the spot welding gun 3, and the electrode polishing device 4 include the operations of electrode polishing and electrode roughening, which will be described later.

[0022] The robot control device 5 has a robot control unit 52 that controls the robot 2. The robot control unit 52 has a robot motion control unit 521 that controls a plurality of robot drive motors 26 of the robot 2 respectively. The robot motion control unit 521 sends an operation command based on an operation program to the robot drive circuit 53. The robot drive circuit 53 supplies a drive current based on the operation command to each of the robot drive motors 26.

[0023] The robot 2 has a robot position detector 27 for detecting the position and orientation of the robot 2. The robot position detector 27 of the present embodiment has a rotation position detector (not shown) attached to each of the robot drive motors 26. The robot control unit 52 receives a signal regarding the rotation position output from the robot position detector 27. Thereby, the robot control unit 52 can detect the position and orientation of the spot welding gun 3 based on the position and orientation of the robot 2.

[0024] The robot control device 5 has a welding gun control unit 54 that controls the spot welding gun 3. The welding gun control unit 54 has a welding gun motion control unit 541 that controls the electrode drive motor 33 of the spot welding gun 3 and controls the voltage applied to the electrodes (the movable electrode 31 and the opposing electrode 32). The welding gun motion control unit 541 sends an operation command based on an operation program to the electrode drive circuit 55 and the voltage supply circuit 56. The electrode drive circuit 55 supplies a drive current based on the operation command for moving the movable electrode 31 to the electrode drive motor 33. The voltage supply circuit 56 supplies a voltage based on the operation command for spot welding to the movable electrode 31 and the opposing electrode 32.

[0025] The welding gun control unit 54 has a position detection unit 542 that detects the position of the movable electrode 31 with respect to the opposing electrode 32. The spot welding gun 3 has an electrode position detector 34 for detecting the position of the movable electrode 31. The electrode position detector 34 of the present embodiment has a rotation position detector (not shown) attached to the electrode drive motor 33. The position detection unit 542 detects the position of the movable electrode 31 with respect to the opposing electrode 32 based on the output of the electrode position detector 34.

[0026] The welding gun control unit 54 has a torque detection unit 543 that detects the torque output by the electrode drive motor 33. The torque detection unit 543 can detect the torque output by the electrode drive motor 33 based on, for example, an operation command for controlling the electrode drive motor 33. Alternatively, a current detector for detecting the current value supplied to the electrode drive motor 33 can be arranged in the spot welding gun 3. The torque detection unit 543 may detect the torque based on the current value detected by the current detector. Thereby, the torque detection unit 543 can detect the pressing force of the movable electrode 31 toward the opposing electrode 32.

[0027] The robot control device 5 has a polishing control unit 57 that controls the electrode polishing device 4. The polishing control unit 57 has a polishing operation control unit 571 for controlling the blade drive motor 46 of the electrode polishing device 4. The polishing operation control unit 571 sends an operation command based on an operation program for the polishing operation to the blade drive circuit 572. The blade drive circuit 572 supplies a drive current based on the operation command to the blade drive motor 46.

[0028] As shown in FIGS. 1 and 2, the robot control device 5 has a teaching operation panel 6 connected via a communication device. The teaching operation panel 6 has an input unit 61 for inputting information regarding the robot 2, the spot welding gun 3, and the electrode polishing device 4. An operator can input, to the robot control device 5 via the input unit 61, an operation program regarding the position and posture of the spot welding gun 3 based on the taught position and posture of the robot 2, an operation program regarding the operation of the electrode polishing device 4, and the like. The input unit 61 is composed of a keyboard, a dial, or the like. The teaching operation panel 6 has a display unit 62 for displaying information regarding the robot 2, the spot welding gun 3, and the electrode polishing device 4.

[0029] Next, the polishing operation of the movable electrode 31 and the counter electrode 32 of the spot welding gun 3 in this spot welding system 1 will be described using the flowchart shown in FIG. 6. The spot welding system 1 of the present embodiment polishes the surfaces of the movable electrode 31 and the counter electrode 32 of the spot welding gun 3 using the blade portion 42, and then roughens the surfaces of the movable electrode 31 and the counter electrode 32. The spot welding system 1 performs roughening processing on the surfaces of the movable electrode 31 and the counter electrode 32 using the same blade portion 42 as when polishing the movable electrode 31 and the counter electrode 32.

[0030] During appropriate timing in a predetermined welding operation by the spot welding gun 3, the robot control device 5 changes the position and posture of the robot 2 from the welding position under the control of the robot motion control unit 521, and moves the spot welding gun 3 to the position of the electrode polishing device 4 determined in advance by the operation program (step S1).

[0031] After the spot welding gun 3 moves to a predetermined position of the electrode polishing device 4, the robot control device 5 drives the electrode drive motor 33 under the control of the welding gun operation control unit 541, and moves the movable electrode 31 and the counter electrode 32 to a predetermined polishing position where the blade portion 42 is sandwiched as shown in FIG. 5. Thereafter, the robot control device 5 drives the blade drive motor 46 under the control of the polishing operation control unit 571 to rotate the cutter holder 420, and starts polishing the surfaces of the movable electrode 31 and the counter electrode 32 with the blade portion 42 rotating around the rotation axis X (step S2). The molten metal adhering to the surfaces of the movable electrode 31 and the counter electrode 32 is ground and removed by the rotating blade portion 42.

[0032] The polishing of the electrodes is performed by sandwiching the rotating blade portion 42 with a predetermined pressing force between the movable electrode 31 and the counter electrode 32. The robot control device 5 controls the driving of the electrode drive motor 33 by the welding gun control unit 54 so that the pressing force of the movable electrode 31 toward the counter electrode 32 detected by the torque detection unit 543 of the welding gun control unit 54 becomes a predetermined pressing force required for polishing based on the operation program.

[0033] The polishing of the movable electrode 31 and the counter electrode 32 by the rotating blade portion 42 is continuously executed for a predetermined time based on the operation program. The robot control device 5 monitors whether the polishing has been completed based on the operation program (step S3). If it is determined that the polishing has not been completed (NO in step S3), the polishing is continued.

[0034] When the robot control device 5 determines that the polishing has been completed (YES in step S3), it changes the position and posture of the robot 2 under the control of the robot motion control unit 521, and moves the movable electrode 31 and the counter electrode 32 of the spot welding gun 3 to the roughening position determined in advance by the operation program to start the roughening process (step S4).

[0035] When the roughening process is started, the robot control device 5 moves the movable electrode 31 in a direction away from the counter electrode 32 and separates the movable electrode 31 and the counter electrode 32 from the blade portion 42 respectively to release the clamping of the blade portion 42 under the control of the welding gun motion control unit 541 and the robot motion control unit 521 as shown in FIG. 7. Further, the robot control device 5 changes the position and posture of the robot 2 under the control of the robot motion control unit 521, and changes the position and posture of the spot welding gun 3 so that the tip surfaces 31b and 32b of the movable electrode 31 and the counter electrode 32 contact the corner portions 42a of the blade portion 42. The corner portions 42a of the blade portion 42 are the corner portions respectively arranged at the outermost ends (upper end portion and lower end portion) of the blade portion 42 along the rotation axis X. The corner portions 42a are arranged at the end portions of the blade portion 42 adjacent to the upper side shoulder portion 421 and the lower side shoulder portion 422 of the cutter holder 420 respectively. Note that the blade portion 42 continues to rotate even after the start of the roughening process.

[0036] In the present embodiment, as shown in FIG. 7, the movable electrode 31 and the counter electrode 32 on which the roughening process is performed are arranged at positions separated from each other by a distance corresponding to the height of the cutter holder 420 along the rotation axis X (the separation distance between the upper shoulder 421 and the lower shoulder 422). The movable electrode 31 and the counter electrode 32 separated from each other move parallel to each other such that the central axis Y is displaced from the rotation axis X, and the tip surfaces 31b and 32b are brought into contact with the corner portion 42a of the blade portion 42. At this time, the movable electrode 31 and the counter electrode 32 apply only a pressing force smaller than the pressing force during polishing to the blade portion 42. Alternatively, the movable electrode 31 and the counter electrode 32 do not substantially apply a pressing force to the blade portion 42. The tip surfaces 31b and 32b of the movable electrode 31 and the counter electrode 32 only lightly contact the corner portion 42a of the blade portion 42.

[0037] The tip surfaces 31b and 32b of the movable electrode 31 and the counter electrode 32 in contact with the corner portion 42a of the blade portion 42 are linearly damaged by the rotation of the blade portion 42. As a result, fine linear grooves are formed on the tip surfaces 31b and 32b. The robot control device 5, under the control of the robot operation control unit 521, as shown in FIG. 8, changes the positions of the movable electrode 31 and the counter electrode 32 with respect to the corner portion 42a of the blade portion 42 in various directions within a plane parallel to the tip surfaces 31b and 32b. As a result, as shown in FIG. 9, a plurality of fine linear grooves G extending in a plurality of directions are formed on the tip surfaces 31b and 32b of the movable electrode 31 and the counter electrode 32 by the corner portion 42a of the blade portion 42, and the surfaces of the movable electrode 31 and the counter electrode 32 are roughened.

[0038] The pitch of the adjacent grooves G is adjusted by appropriately adjusting the rotation speed of the blade portion 42 and the moving speeds of the movable electrode 31 and the counter electrode 32. The crossing angle of the grooves G intersecting each other is adjusted by appropriately adjusting the plurality of moving directions of the movable electrode 31 and the counter electrode 32. The movement of the movable electrode 31 and the counter electrode 32 when forming the plurality of grooves G by the corner portion 42a of the blade portion 42 is not limited to linear movement and may be curvilinear movement.

[0039] When performing a process of making linear scratches on the tip surfaces 31b and 32b of the movable electrode 31 and the counter electrode 32, the robot control device 5 may move the movable electrode 31 and the counter electrode 32 in the axial direction (vertical direction in FIGS. 7 and 8) and in a direction orthogonal to the axial direction (left - right direction in FIGS. 7 and 8) by the robot motion control unit 521. According to this, on curved surfaces such as the R parts 31a and 32a of the movable electrode 31 and the counter electrode 32, a plurality of linear grooves G can be formed by the corner part 42a of the rotating blade part 42.

[0040] During the roughening process, the robot control device 5 may control the position and posture of the spot - welding gun 3 so that the central axis Y of the movable electrode 31 and the counter electrode 32 is inclined with respect to the rotation axis X, as shown in FIGS. 10 and 11, by the robot motion control unit 521. In this case, the corner part 42a of the blade part 42 contacts either the tip surface 31b or 32b of the movable electrode 31 and the counter electrode 32. The robot control device 5 changes the position of the movable electrode 31 or the counter electrode 32 with respect to the corner part 42a of the blade part 42 in various directions within a plane parallel to the tip surfaces 31b and 32b to roughen the tip surfaces 31b or 32b, as shown in FIG. 11, under the control of the robot motion control unit 521.

[0041] In this method, it is necessary to perform the roughening process individually on the movable electrode 31 and the counter electrode 32. However, since the corner part 42a of the blade part 42 can be sharply contacted with the tip surfaces 31b and 32b, distinct grooves G can be formed on the tip surfaces 31b and 32b.

[0042] The robot control device 5 monitors whether the roughening process has ended based on the operation program (step S5). If it is determined that the roughening process has not ended (NO in step S5), the roughening process is continued.

[0043] When the robot control device 5 determines that the roughening process has ended (YES in step S5), the robot operation control unit 521 changes the position and orientation of the robot 2, moves the spot welding gun 3 to the welding operation position determined in advance by the operation program, and starts the next welding operation (step S6). As a result, the polishing operations of the movable electrode 31 and the counter electrode 32 are completed.

[0044] According to the robot control device 5 of the present embodiment, the following effects are obtained. The robot control device 5 controls the operation of the robot 2 including the spot welding gun 3 having a pair of movable electrode 31 and counter electrode 32 arranged opposite to each other. The robot control device 5 has a robot operation control unit 521 that moves the movable electrode 31 and the counter electrode 32 of the spot welding gun 3 to the polishing position by the blade portion 42 so as to polish the surfaces of the movable electrode 31 and the counter electrode 32 by the rotating blade portion 42 of the electrode polishing device 4. The robot operation control unit 521 changes the positions of the movable electrode 31 and the counter electrode 32 in contact with the blade portion 42 from the polishing position so as to damage the tip surfaces 31b and 32b of the movable electrode 31 and the counter electrode 32 after polishing by the blade portion 42. As a result, the surfaces of the movable electrode 31 and the counter electrode 32 polished by the rotating blade portion 42 can be roughened using the same blade portion 42. There is no need to add a special device or labor for roughening the surfaces of the movable electrode 31 and the counter electrode 32, and it is possible to roughen the surfaces of the movable electrode 31 and the counter electrode 32.

[0045] In the present embodiment, the robot operation control unit 521 moves the movable electrode 31 and the counter electrode 32 while changing the positions of the movable electrode 31 and the counter electrode 32 in contact with the blade portion 42 so as to damage the surfaces of the movable electrode 31 and the counter electrode 32. As a result, a plurality of fine linear grooves extending in a plurality of directions are formed in the movable electrode 31 and the counter electrode 32. Therefore, the surfaces of the movable electrode 31 and the counter electrode 32 can be easily roughened.

[0046] In this embodiment, when scratching the surfaces of the movable electrode 31 and the counter electrode 32, the robot motion control unit 521 can move the movable electrode 31 and the counter electrode 32 in the axial direction and in a direction orthogonal to the axial direction. Thereby, linear grooves G can be formed on curved surfaces such as the R portions 31a and 32a of the movable electrode 31 and the counter electrode 32 to roughen the surfaces.

[0047] In this embodiment, when scratching the surfaces of the movable electrode 31 and the counter electrode 32, the robot motion control unit 521 moves the movable electrode 31 and the counter electrode 32 so that the surfaces of the movable electrode 31 and the counter electrode 32 come into contact with the corner portion 42a of the blade portion 42. According to this, the surfaces of the movable electrode 31 and the counter electrode 32 can be easily roughened using the blade portion 42 without modifying the blade portion 42 used for polishing.

[0048] In this embodiment, the process of scratching the surfaces of the movable electrode 31 and the counter electrode 32 is a roughening process. According to this, by using the blade portion 42 for polishing to scratch the surfaces of the movable electrode 31 and the counter electrode 32, the surfaces of the movable electrode 31 and the counter electrode 32 can be easily roughened.

[0049] The spot welding system 1 of the present embodiment includes a spot welding gun 3 having a pair of movable electrodes 31 and a counter electrode 32 arranged to face each other, a robot 2 that moves the spot welding gun 3, an electrode polishing device 4 that polishes the surfaces of the pair of movable electrodes 31 and the counter electrode 32 with a rotating blade portion 42, and a robot control device 5 that controls the operations of the robot 2 and the electrode polishing device 4. The robot control device 5 has a robot motion control unit 521 that moves the pair of movable electrodes 31 and the counter electrode 32 of the spot welding gun 3 to a polishing position by the blade portion 42 so that the surfaces of the movable electrodes 31 and the counter electrode 32 are polished by the rotating blade portion 42 of the electrode polishing device 4. The robot motion control unit 521 changes the positions of the movable electrodes 31 and the counter electrode 32 in contact with the blade portion 42 from the polishing position so as to damage the surfaces of the movable electrodes 31 and the counter electrode 32 after polishing by the blade portion 42. As a result, the surfaces of the movable electrodes 31 and the counter electrode 32 that have been polished by the rotating blade portion 42 can be roughened using the same blade portion 42. It is not necessary to add a special device or labor for roughening the surfaces of the movable electrodes 31 and the counter electrode 32, and the surfaces of the movable electrodes 31 and the counter electrode 32 can be roughened.

[0050] The movable electrodes 31 and the counter electrode 32 of the present embodiment have R portions 31a and 32a with rounded outer peripheral corners, but are not limited to such a form. The movable electrodes 31 and the counter electrode 32 may have chamfered portions 31c and 32c with obliquely formed outer peripheral corners, for example, as shown in FIG. 12.

[0051] In the spot welding gun 3 of the present embodiment, the movable electrode 31 is provided so as to be movable in a direction approaching and separating from the counter electrode 32, but is not limited to such a form. Both of the pair of electrodes of the spot welding gun may be provided so as to be movable.

[0052] The electrode polishing device 4 of the present embodiment is configured to be able to polish and roughen both the movable electrode 31 and the counter electrode 32 simultaneously, but is not limited to such a form. The electrode polishing device may be configured to polish and roughen the pair of electrodes one by one.

[0053] The spot welding system 1 of this embodiment is configured to be controlled by a single robot control device 5 for a robot 2, a spot welding gun 3, and an electrode grinding device 4, but is not limited to such a form. The electrode grinding device 4 may be configured to be controlled by a dedicated control device separate from the robot control device 5.

Explanation of Reference Numerals

[0054] 1 Spot welding system 2 Robot 3 Spot welding gun 31 Movable electrode 32 Opposing electrode 4 Electrode grinding device 42 Blade part 42a Corner part 5 Robot control device 521 Robot operation control unit

Claims

1. A robot control device for controlling the operation of a robot equipped with a spot welding gun having a pair of electrodes arranged opposite to each other, the robot control device having a robot motion control unit that moves the pair of electrodes of the spot welding gun to a polishing position by a rotating blade portion of an electrode polishing device so as to polish the surfaces of the pair of electrodes, wherein the robot motion control unit changes the positions of the pair of electrodes in contact with the blade portion from the polishing position to a roughening position so as to roughen the surfaces of the pair of electrodes after polishing by the blade portion by scratching the surfaces of the pair of electrodes using the same blade portion as during polishing.

2. The robot control device according to claim 1, wherein the robot motion control unit moves the pair of electrodes arranged at the roughening position so as to scratch the surfaces of the pair of electrodes while changing the positions of the pair of electrodes in contact with the blade portion.

3. The robot control device according to claim 1 or 2, wherein the robot motion control unit performs movement in the axial direction of the pair of electrodes and movement in a direction orthogonal to the axial direction when scratching the surfaces of the pair of electrodes arranged at the roughening position.

4. The robot control device according to any one of claims 1 to 3, wherein the robot motion control unit moves the pair of electrodes so that the surfaces of the pair of electrodes come into contact with the corner portions of the blade portion when scratching the surfaces of the pair of electrodes arranged at the roughening position.

5. A spot welding gun having a pair of electrodes arranged opposite to each other, a robot that moves the spot welding gun, an electrode polishing device that polishes the surfaces of the pair of electrodes with a rotating blade portion, and a robot control device that controls the operations of the robot and the electrode polishing device, wherein the robot control device has a robot motion control unit that moves the pair of electrodes of the spot welding gun to a polishing position by a rotating blade portion of the electrode polishing device so as to polish the surfaces of the pair of electrodes, and the robot motion control unit changes the positions of the pair of electrodes in contact with the blade portion from the polishing position to a roughening position so as to roughen the surfaces of the pair of electrodes after polishing by the blade portion by scratching the surfaces of the pair of electrodes using the same blade portion as during polishing.

6. A robot control device for controlling the operation of a robot equipped with a spot welding gun having a pair of electrodes arranged opposite to each other, A robot operation control unit that moves the pair of electrodes of the spot welding gun to a polishing position by a rotating blade portion of an electrode polishing device so as to polish the surfaces of the pair of electrodes. The robot operation control unit is a robot control device that moves the pair of electrodes while changing the positions of the pair of electrodes in contact with the blade portion so as to damage the surfaces of the pair of electrodes after polishing by the blade portion, and changes the positions of the pair of electrodes in contact with the blade portion from the polishing position. **Claim 7**: A robot control device that controls the operation of a robot equipped with a spot welding gun having a pair of opposed electrodes, A robot operation control unit that moves the pair of electrodes of the spot welding gun to a polishing position by a rotating blade portion of an electrode polishing device so as to polish the surfaces of the pair of electrodes. The robot operation control unit is a robot control device that changes the positions of the pair of electrodes in contact with the blade portion from the polishing position so as to damage the surfaces of the pair of electrodes after polishing by the blade portion, and moves the pair of electrodes so that the surfaces of the pair of electrodes contact the corner portions of the blade portion. **Claim 8** A spot welding gun having a pair of opposed electrodes, A robot that moves the spot welding gun, An electrode polishing device that polishes the surfaces of the pair of electrodes with a rotating blade portion, A robot control device that controls the operations of the robot and the electrode polishing device, and The robot control device has A robot operation control unit that moves the pair of electrodes of the spot welding gun to a polishing position by a rotating blade portion of the electrode polishing device so as to polish the surfaces of the pair of electrodes. The robot operation control unit is a spot welding system that moves the pair of electrodes while changing the positions of the pair of electrodes in contact with the blade portion so as to damage the surfaces of the pair of electrodes after polishing by the blade portion, and changes the positions of the pair of electrodes in contact with the blade portion from the polishing position. **Claim 9**: A spot welding gun having a pair of opposed electrodes, A robot that moves the spot welding gun, An electrode polishing device that polishes the surfaces of the pair of electrodes with a rotating blade portion, A robot control device that controls the operations of the robot and the electrode polishing device, and The robot control device has A robot motion control unit that moves the pair of electrodes of the spot welding gun to a polishing position by a rotating blade portion of the electrode polishing device so as to polish the surfaces of the pair of electrodes. The robot motion control unit changes the positions of the pair of electrodes in contact with the blade portion from the polishing position so as to damage the surfaces of the pair of electrodes after polishing by the blade portion, and moves the pair of electrodes so that the surfaces of the pair of electrodes come into contact with the corner portions of the blade portion. A spot welding system.

Images