JP5090760B2 - Arc start method for welding torch and robot arc welding - Google Patents

Description

  In the present invention, after the welding wire is brought close to the workpiece and once contacted, the welding wire is pulled away from the workpiece to generate an initial arc, and the welding wire is brought closer to the workpiece again to make a transition to a steady arc. The present invention relates to an arc start control method for robot arc welding.

  Conventionally, in the consumable electrode type robot arc welding, the following arc start control method has been proposed as a method for reliably generating an arc between the wire tip and the workpiece and reducing the occurrence of spatter. That is, in consumable electrode type robot arc welding, the wire feed motor is rotated forward to feed the welding wire forward to the workpiece. When it is determined that the welding wire is short-circuited with the workpiece, the wire feeding motor is reversely rotated to feed the welding wire backward, and at the same time, an initial current having a small current value is energized. When the initial arc is generated by the backward feeding, the welding wire is fed forward again at a steady feeding speed, and at the same time, a steady welding current is applied to start the arc (see, for example, Patent Document 1). . Hereinafter, the arc start control method of this prior art will be described with reference to FIGS.

  FIG. 6 is a schematic diagram showing a welding wire feed system for explaining a conventional arc start control method for robot arc welding. In the figure, a welding torch 4 and a wire feeding motor WM are mounted on a manipulator (not shown), and the welding wire 1 is connected to the wire feeding motor WM by a feeding roll 5 directly connected to the welding torch 4. Sent through. When the wire feed motor WM is rotated forward, the welding wire 1 is fed forward to the workpiece 2 and when it is rotated reversely, the welding wire 1 is fed backward from the workpiece 2. The welding power source device PS feeds the welding voltage Vw to the welding wire 1 by a contact tip 6 attached to the tip of the welding torch 4.

  FIG. 7 is a diagram for explaining a conventional arc start control method for robot arc welding. When the welding start signal is input from the outside to the welding power source PS (see FIG. 6), the welding wire 1 is fed forward to the workpiece 2 at the initial feeding speed as shown in FIG. 7 (A). . At the same time, a no-load voltage is applied as the welding voltage Vw between the welding wire 1 and the workpiece 2. And the distance Lw between a wire front-end | tip and to-be-welded object becomes short gradually by said advance feed.

  Next, as shown in FIG. 7B, when it is determined that the wire tip 1 a is short-circuited to the workpiece 2 by forward feeding, the welding wire 1 is fed backward from the workpiece 2. At the same time, an initial current having a small current value is energized.

  Next, as shown in FIG. 7C, when the wire tip 1a and the work piece 2 are separated from each other by backward feeding, an initial arc 3a in which the initial current is applied is generated. It is determined that the initial arc 3a has been generated, and during the predetermined time, as shown in FIG. 4D, the backward feeding is continued while the initial arc generation state is maintained. Accordingly, the distance Lw between the wire tip and the workpiece is gradually increased.

Next, after the predetermined time has elapsed, the welding wire 1 is fed forward again to the workpiece 2 at a steady feeding speed. At the same time, a steady welding current having a large current corresponding to the steady feeding speed is energized. Accordingly, the initial arc generation state shown in FIG. 7D shifts to the steady arc generation state where the steady arc 3b shown in FIG. 7E is generated.
JP 2002-205169 A

  In the arc start control method of the robot arc welding of the prior art described above, when it is determined that the wire tip 1a is short-circuited with the workpiece 2 by forward feeding as shown in FIG. The wire 1 is fed backward from the workpiece 2. At the same time, an initial current having a small current value is energized. Then, as shown in FIG. 5C, when the wire tip 1a and the workpiece 2 are separated by backward feeding, an initial arc 3a in which the above-described initial current is applied is generated. After the wire tip 1a is short-circuited with the workpiece 2 by this forward feeding, when the welding wire 1 is fed backward from the workpiece 2, the feeding performance of the wire feeding device requires high responsiveness. Is done. For this reason, a servomotor is usually used for the wire feeding device, but the servomotor and the servo driver are expensive.

  On the other hand, instead of feeding the welding wire 1 forward or backward to bring the welding wire 1 close to or away from the workpiece 2, the welding torch 4 is attached to the tip of the robot manipulator, and the manipulator is attached. There is also an example of operating. However, in this method, the operation of pulling the welding wire 1 away from the workpiece 2 greatly depends on the responsiveness of the manipulator.

  An object of the present invention is to provide an arc start method for robot arc welding and a welding torch that can realize a good arc start at a low cost and not affected by the responsiveness of a manipulator.

The first invention is
A welding torch having a welding torch to which a welding wire is fed and a welding torch moving mechanism,
A moving mechanism body attached to the manipulator of the welding robot by the welding torch moving mechanism;
A solenoid shaft to which the welding torch is attached;
A solenoid coil;
Formed with a spring that pushes up the solenoid shaft,
When power is supplied to the solenoid coil, the solenoid shaft moves downward to compress the spring,
Using a welding torch in which the solenoid shaft is pushed up by the spring when the power supplied to the solenoid coil is stopped,
At the start of welding, the manipulator is moved to move the welding torch to a pre-taught welding start position where the distance between the tip of the welding wire and the workpiece is larger than the moving distance of the solenoid shaft. Let
After reaching the welding start position, power is supplied to the solenoid coil to move the solenoid shaft downward,
Thereafter, the welding wire is forwardly fed from the welding torch to the workpiece,
When it is determined that the tip of the welding wire is short-circuited with the workpiece, the forward feeding of the welding wire is continued or stopped, and the power supplied to the solenoid coil is stopped to stop the solenoid shaft. The welding torch is moved upward by the spring, the tip of the welding wire is moved away from the work piece to generate an initial arc, and then the welding wire is constantly fed and steady. This is an arc start method for robot arc welding that shifts to an arc.

  According to the arc start method of the welding torch and robot arc welding of the present invention, after the wire tip is short-circuited with the workpiece, the welding wire is separated from the workpiece by the operation of the solenoid shaft having high responsiveness of the welding torch moving mechanism. Therefore, there is no problem that the initial arc does not occur.

[Embodiment 1]
Embodiment 1 of the present invention will be described based on an example with reference to the drawings. FIG. 1 is a configuration diagram of an arc start method for robot arc welding according to Embodiment 1 of the present invention. In the figure, when a welding start signal St is input from the outside, the robot controller RC outputs an operation control signal Mc for controlling the operation of the manipulator RM. At the same time, an interface signal If formed by the voltage setting signal Vs, the steady feeding speed setting signal Ws and the output start signal On is transmitted to the welding power source PS. The manipulator RM is equipped with a wire feed motor WM, and a welding torch moving mechanism 11 is attached to the tip of the manipulator RM. The welding torch moving mechanism 11 includes a moving mechanism main body 12 attached to the manipulator RM, a solenoid shaft 13 to which the welding torch 4 is attached, a solenoid coil 14 for moving the solenoid shaft 13, and a spring 15 for pushing up the solenoid shaft 13. It is formed with.

  When the welding torch moving mechanism 11 supplies power to the solenoid coil 14, the solenoid shaft 13 moves downward from the position shown in FIG. 2A as shown in FIG. Compress. FIG. 2 is a diagram for explaining the operation of the welding torch moving mechanism according to the first embodiment of the present invention. When the power supplied to the solenoid coil 14 is stopped, the solenoid shaft 13 is pushed up by the spring 15 as shown in FIG.

  In FIG. 1, the manipulator RM moves the tip position (TCP) of the welding torch 4 along the motion locus taught in advance according to the motion control signal Mc. The welding wire 1 is fed through a coil liner having a length of about 1.5 m that connects between the wire feeding motor WM and the main body of the welding torch 4.

  The welding power supply device PS receives the interface signal If and supplies a welding voltage Vw to the welding wire 1 via a contact tip attached to the tip of the welding torch 4. Then, an arc 3 is generated between the welding wire 1 and the workpiece 2 and the welding current Iw is applied. Similarly, the welding power source device PS outputs a feed control signal Fc to the wire feed motor WM and controls the rotation speed of the wire feed motor WM. The distance between the wire tip 1a and the workpiece 2 is the distance Lw between the wire tip and the workpiece, and the distance Lw between the wire tip and the workpiece is the same as the arc length during arc generation.

The voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd. Short circuit /
The arc discrimination circuit SA receives the voltage detection signal Vd as described above, and outputs a short circuit signal (High level) when the wire tip 1a and the work piece 2 are short circuited, and an arc generation signal when the arc is generated. (Low level) is output as a short circuit / arc discrimination signal Sa. The delay circuit DT has a predetermined delay time Td from the time when the short circuit / arc determination signal Sa changes from the short circuit signal to the arc generation signal in order to delay the timing of performing forward feeding again after the initial arc occurs. A delay signal Dt that is at a high level only during this period is output.

  The operation will be described below with reference to FIG. FIG. 3 is a timing chart of each signal of the arc start control method for robot arc welding according to the first embodiment of the present invention. FIG. 4A shows the time change of the welding start signal St, FIG. 4B shows the time change of the operation control signal Mc, and FIG. 4C shows the time change of the output start signal On. (D) shows the time change of the welding voltage Vw, (E) shows the time change of the electric power Pc supplied to the solenoid coil, and (F) shows the feeding. FIG. 4G shows the time change of the control signal Fc, FIG. 4G shows the time change of the wire tip / workpiece distance Lw, and FIG. 4H shows the time change of the short circuit / arc discrimination signal Sa. (I) shows the time change of the welding current Iw, (J) shows the time change of the delay signal Dt, and (K1) to (K5) in FIG. The feeding state of the welding wire 1 is shown.

[Period from time t1 to t2]
At time t1, as shown in FIG. 3A, when the welding start signal St is externally input (high level) to the robot controller RC, as shown in FIG. 3B, the robot controller RC The operation control signal Mc for moving the welding torch 4 attached to the manipulator RM is output to the manipulator RM. At time t2, the welding torch 4 arrives at the welding start position taught in advance and stops as shown in FIG.

[Period from time t2 to t3]
When the welding torch 4 arrives at the welding start position at time t2, as shown in FIG. 3C, an output start signal On is output (High level) from the robot controller RC. Accordingly, as shown in FIG. 2E, electric power Pc is supplied from the welding power source device PS to the solenoid coil 14 of the welding torch moving mechanism 11, and the solenoid shaft 13 is moved from the position shown in FIG. As shown in FIG. 5B, the spring 15 is moved downward to compress the spring 15 and stop. At this time, the welding torch 4 attached to the solenoid shaft 13 moves in the direction of the workpiece 2 and the distance Lw between the wire tip and the workpiece is shortened as shown in FIG.

  At the same time, as described above with reference to FIG. 1, the output control circuit in the welding power source device PS forms and outputs a constant current characteristic or a drooping characteristic. However, during the period from time t2 to t3, since the welding wire 1 and the work piece 2 are separated and are in a no-load state, the no-load voltage is applied as the welding voltage Vw as shown in FIG. Is done.

[Period from time t3 to t4]
After the solenoid shaft 13 moves downward at time t3, the feed control signal Fc becomes the initial feed speed setting value Wi, and the welding wire 1 is fed forward to the workpiece 2 at the initial feed speed Wfi. . Moreover, as shown in FIG.3 (D), the no-load voltage is applied as the welding voltage Vw also during the period of time t3-t4. Further, during this period, as shown in FIG. 5G, the distance Lw between the wire tip and the workpiece is gradually shortened by the above-described forward feeding.

[Period from time t4 to t5]
At time t4, as shown in FIG. 3 (K2), when the welding wire 1 comes into contact with the workpiece 2 by forward feeding, as shown in FIG. 3 (H), the short-circuit / arc discrimination signal Sa is a short-circuit signal ( High level). In response to this, as shown in FIG. 5F, the feed control signal Fc becomes Low level, and feeding of the welding wire is stopped. At the same time, as shown in FIG. 2E, the electric power Pc supplied to the solenoid coil 14 is stopped, and the solenoid shaft 13 is pushed up from the position shown in FIG. Then, as shown in FIG. 2A, the moving mechanism main body 12 is contacted and stopped. Thereby, the wire tip 1a and the workpiece 2 are separated.

  At the same time, as shown in FIG. 3 (I), the initial current Is having a small current value is applied by the constant current characteristic or the drooping characteristic from the output control circuit in the welding power source apparatus PS described above. The value of the initial current Is is set to a small current value of several A to several tens A. The reason is that the welding wire 1 is melted by the initial current Is and is not welded to the workpiece 2.

[Period from time t5 to t6]
At time t5, as shown in FIG. 3 (K3), when the wire tip 1a and the workpiece 2 are separated from each other, an initial arc 3a in which the initial current Is is applied is generated. At this time, the short / arc discriminating circuit SA discriminates that the initial arc 3a has been generated, and the short / arc discriminating signal Sa changes from the short circuit signal (High level) to the arc generation signal as shown in FIG. It changes to (Low level). Using this change as a trigger, the delay circuit DT outputs (High level) the delay signal Dt for a predetermined delay time Td (time t5 to t6), as shown in FIG.

[Period from time t6 to t7]
At time t6, when the delay signal Dt changes from the High level to the Low level as shown in FIG. 3 (J), the feed control signal Fc is a positive value steady feed as shown in FIG. The speed setting signal Ws is obtained, and the welding wire 1 is fed forward again to the workpiece 2 at the steady feeding speed Wfs. At the same time, the output control circuit in the above-described welding power source device PS forms a constant voltage characteristic corresponding to the voltage setting signal Vs, so that the welding voltage Vw is equal to the voltage setting signal Vs as shown in FIG. As shown in FIG. 1I, a large steady welding current Ic corresponding to the steady feeding speed Wfs is applied. At the same time, as shown in FIG. 5B, the robot controller RC outputs an operation control signal Mc for moving the welding torch 4 to the manipulator RM, and moves the welding torch 4 from the stopped state to the welding direction taught in advance. Move.

  At time t7, as shown in FIG. 3G, the wire tip-to-be-welded object distance Lw is calculated from the wire tip-to-be-welded object distance Lwt at the time of re-forward feeding at time t6. At time t7 after the convergence time Tc1 has elapsed due to the energization of the welding current Ic, it converges to a steady arc length (steady wire tip-to-be-welded distance) Lwc. Therefore, during this period, a transition is made from the initial arc generation state in which the initial arc 3a shown in FIG. 4 (K4) is generated to the steady arc generation state in which the steady arc 3b shown in FIG.

  As a result, in the arc start method for robot arc welding according to the first embodiment of the present invention, the welding torch 4 arrives at the welding start position and stops, power is supplied to the solenoid coil 14, and the solenoid shaft 13 is lowered. The spring 15 is compressed by moving in the direction. When it is determined that the welding wire 1 is fed forward to the workpiece 2 and the wire tip 1a is short-circuited with the workpiece 2, the power supplied to the solenoid coil 14 is stopped, and the solenoid shaft 13 is pushed up by the spring 15 and comes into contact with the moving mechanism main body 12 to stop. For this reason, the welding wire 1 is separated from the workpiece 2 and at the same time, an initial current having a small current value is applied. When the wire tip 1a and the workpiece 2 are separated from each other, an initial arc 3a in which the initial current is applied is generated. Thereafter, the welding wire 1 is fed forward again, and the state shifts to a steady arc generation state in which the steady arc 3b is generated.

  Therefore, after the wire tip 1a is short-circuited to the work piece 2, the welding wire 1 is separated from the work piece 2 by the above-described operation of the solenoid shaft 13 having high responsiveness, so that the initial arc is not generated. It does not occur.

  In addition, at the time t4 described above, the feeding of the welding wire 1 is stopped. However, instead of stopping the feeding of the welding wire 1, the welding wire 1 is continuously fed forward at the initial feeding speed Wfi. At time t6, the welding wire 1 may be fed forward to the workpiece 2 at the steady feeding speed Wfs.

[Embodiment 2]
A second embodiment of the present invention will be described based on an example with reference to the drawings. The configuration of the arc start method for robot arc welding according to the second embodiment of the present invention is different from the configuration of the first embodiment of the present invention shown in FIG. 1 only in the welding torch moving mechanism, and other functions are the same as those in FIG. Since it is the same as the function shown, description is abbreviate | omitted. In the welding torch moving mechanism 16 according to the second embodiment of the present invention, when power is supplied to the solenoid coil 14, the solenoid shaft 13 moves upward from the position shown in FIG. As shown in FIG. 5B, the movement mechanism main body 12 is brought into contact with and stopped. When the power supplied to the solenoid coil 14 is stopped, the solenoid shaft 13 is pulled downward by the spring 15 from the position shown in FIG. 5B, and the solenoid shaft 13 moves downward. Then, as shown in FIG. 5A, the spring 15 is compressed and the solenoid shaft 13 stops. FIG. 4 is a diagram for explaining the operation of the welding torch moving mechanism according to the second embodiment of the present invention.

  The operation will be described below with reference to FIG. FIG. 5 is a timing chart of each signal in the arc start control method for robot arc welding according to the second embodiment of the present invention. FIG. 4A shows the time change of the welding start signal St, FIG. 4B shows the time change of the operation control signal Mc, and FIG. 4C shows the time change of the output start signal On. (D) shows the time change of the welding voltage Vw, (E) shows the time change of the electric power Pc supplied to the solenoid coil, and (F) shows the feeding. FIG. 4G shows the time change of the control signal Fc, FIG. 4G shows the time change of the wire tip / workpiece distance Lw, and FIG. 4H shows the time change of the short circuit / arc discrimination signal Sa. (I) shows the time change of the welding current Iw, (J) shows the time change of the delay signal Dt, and (K1) to (K5) in FIG. The feeding state of the welding wire 1 is shown.

[Period from time t1 to t2]
At time t1, as shown in FIG. 5A, when the welding start signal St is externally input (high level) to the robot control device RC, as shown in FIG. 5B, the robot control device RC The operation control signal Mc for moving the welding torch 4 attached to the manipulator RM is output to the manipulator RM. At time t2, the welding torch 4 arrives at the welding start position taught in advance and stops as shown in FIG.

[Period from time t2 to t3]
When the welding torch 4 arrives at the welding start position at time t2, as shown in FIG. 5C, an output start signal On is output (High level) from the robot controller RC. In response to this, as shown in FIG. 5F, the feed control signal Fc becomes a positive initial feed speed set value Wi, and the welding wire 1 advances to the work piece 2 at the initial feed speed Wfi. Be sent. Further, during the period from the time t2 to the time t3, as shown in FIG. 5G, the distance Lw between the wire tip and the workpiece is gradually shortened by the above-described forward feeding.

  At the same time, as described above with reference to FIG. 1, the output control circuit in the welding power source device PS forms and outputs a constant current characteristic or a drooping characteristic. However, during the period from time t2 to t3, since the welding wire 1 and the work piece 2 are separated and are in an unloaded state, the no-load voltage is applied as the welding voltage Vw as shown in FIG. Is done.

[Period from time t3 to t4]
At time t3, as shown in FIG. 5 (K2), when the welding wire 1 comes into contact with the workpiece 2 by forward feeding, as shown in FIG. 5 (H), the short-circuit / arc discrimination signal Sa is a short-circuit signal ( High level). In response to this, as shown in FIG. 4F, the feed control signal Fc becomes zero, and the feed of the welding wire 1 is stopped. Further, as shown in FIG. 4E, electric power Pc is supplied to the solenoid coil 14, and the solenoid shaft 13 is pulled up with high responsiveness from the position shown in FIG. As shown in FIG. 4B, the solenoid shaft 13 comes into contact with the moving mechanism body 12 and stops. Thereby, as shown to the same figure (G), the wire front-end | tip 1a and the to-be-welded object 2 leave | separate.

  At the same time, as shown in FIG. 5 (I), the initial current Is having a small current value is applied by the constant current characteristic or the drooping characteristic from the output control circuit in the welding power source apparatus PS described above. The value of the initial current Is is set to a small current value of several A to several tens A. The reason is that the welding wire 1 is melted by the initial current Is and is not welded to the workpiece 2.

[Period from time t4 to t5]
At time t4, as shown in the figure (K3), when the wire tip 1a and the workpiece 2 are separated from each other, an initial arc 3a to which the initial current Is is energized is generated. At this time, the short / arc discriminating circuit SA discriminates that the initial arc 3a has been generated, and the short / arc discriminating signal Sa changes from the short circuit signal (High level) to the arc generation signal as shown in FIG. It changes to (Low level). Using this change as a trigger, the delay circuit DT outputs (High level) the delay signal Dt for a predetermined delay time Td (time t4 to t5), as shown in FIG.

[Period from time t5 to t6]
At time t5, as shown in FIG. 5 (J), the delay signal Dt changes from High level to Low level. Then, as shown in FIG. 9F, the feed control signal Fc becomes a steady feed speed setting signal Ws, and the welding wire 1 is fed forward again to the workpiece 2 at the steady feed speed Wfs. At the same time, the output control circuit in the above-described welding power source device PS forms a constant voltage characteristic corresponding to the voltage setting signal Vs, so that the welding voltage Vw is equal to the voltage setting signal Vs as shown in FIG. As shown in FIG. 1I, a large steady welding current Ic corresponding to the steady feeding speed Wfs is applied. At the same time, as shown in FIG. 5B, the robot controller RC outputs an operation control signal Mc for moving the welding torch 4 to the manipulator RM, and moves the welding torch 4 from the stopped state to the welding direction taught in advance. Move.

  At time t6, as shown in FIG. 5G, the wire tip-to-be-welded object distance Lw is calculated from the wire tip-to-be-welded object distance Lwt at the time of re-advancing feeding at time t5. At time t6 after the convergence time Tc1 has elapsed due to energization of the welding current Ic, it converges to a steady arc length (steady wire tip / workpiece distance) Lwc. Therefore, during this period, a transition is made from the initial arc generation state in which the initial arc 3a shown in FIG. 4 (K4) is generated to the steady arc generation state in which the steady arc 3b shown in FIG.

  As a result, in the arc start method for robot arc welding according to the second embodiment of the present invention, the welding torch 4 arrives at the welding start position and stops, and the welding wire 1 is fed forward. When it is determined that the wire tip 1a is short-circuited with the workpiece 2, the forward feeding of the welding wire is stopped, power is supplied to the solenoid coil 14, and the solenoid shaft 13 moves upward. The spring 15 is extended and the solenoid shaft 13 comes into contact with the moving mechanism body 12 and stops. For this reason, the welding wire 1 is separated from the workpiece 2 and at the same time, an initial current having a small current value is applied. When the wire tip 1a and the workpiece 2 are separated from each other, an initial arc 3a in which the initial current is applied is generated. Thereafter, the electric power supplied to the solenoid coil 14 is stopped, the solenoid shaft 13 is pulled by the spring 15, the spring 15 is compressed, the solenoid shaft 13 stops, and the welding wire 1 is fed forward again. By this re-forward feed, the state shifts to a steady arc generation state in which the steady arc 3b is generated.

  Therefore, after the wire tip 1a is short-circuited to the work piece 2, the welding wire 1 is separated from the work piece 2 by the above-described operation of the solenoid shaft 13 having high responsiveness, so that the initial arc is not generated. It does not occur.

  In order to save the electric power Pc supplied to the solenoid coil 14, the electric power Pc supplied to the solenoid coil 14 may be stopped during welding.

  Further, at time t3 described above, the feeding of the welding wire 1 is stopped, but instead of stopping the feeding of the welding wire 1, the welding wire 1 is continuously fed forward at the initial feeding speed Wfi. At time t5, the welding wire 1 may be fed forward to the workpiece 2 at the steady feeding speed Wfs.

It is a block diagram of the arc start method of robot arc welding of Embodiment 1 of this invention. It is a figure for demonstrating operation | movement of the welding torch moving mechanism of Embodiment 1 of this invention. It is a timing chart of each signal of the arc start control method of robot arc welding of Embodiment 1 of the present invention. It is a figure for demonstrating operation | movement of the welding torch moving mechanism of Embodiment 2 of this invention. It is a timing chart of each signal of the arc start control method of robot arc welding of Embodiment 2 of the present invention. It is a schematic diagram which shows the feed system of the welding wire for demonstrating the arc start control method of the robot arc welding of a prior art. It is a figure for demonstrating the arc start control method of robot arc welding of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Welding wire 2 Work piece 3 Arc 3a Initial arc 3b Steady arc 4 Welding torch 5 Feeding roll 6 Contact tip 11 Welding torch moving mechanism 12 Moving mechanism main body 13 Solenoid shaft 14 Solenoid coil 15 Spring 16 Welding torch moving mechanism DT Delay circuit Dt Delay signal Fc Feed control signal Ic Steady welding current If Interface signal Is Initial current Iw Welding current Lw Distance between wire tip and workpiece Lwt Wire tip / workpiece distance Mc Operation control signal On Output start signal Pc Power PS Welding power supply RC Robot controller RM Manipulator SA Arc discrimination circuit Sa Arc discrimination signal St Welding start signal Tc1 Convergence time Td Delay time VD Voltage detection circuit Vd Voltage detection signal Vs Voltage setting signal Vw Welding voltage Wfi Initial feed speed Wfs Regular feed Feeding speed Wi first Periodic feed speed setting value WM Wire feed motor Ws Regular feed speed setting signal

Claims (1)

A welding torch having a welding torch to which a welding wire is fed and a welding torch moving mechanism,
A moving mechanism body attached to the manipulator of the welding robot by the welding torch moving mechanism;
A solenoid shaft to which the welding torch is attached;
A solenoid coil;
Formed with a spring that pushes up the solenoid shaft,
When power is supplied to the solenoid coil, the solenoid shaft moves downward to compress the spring,
Using a welding torch in which the solenoid shaft is pushed up by the spring when the power supplied to the solenoid coil is stopped,
At the start of welding, the manipulator is moved to move the welding torch to a pre-taught welding start position where the distance between the tip of the welding wire and the workpiece is larger than the moving distance of the solenoid shaft. Let
After reaching the welding start position, power is supplied to the solenoid coil to move the solenoid shaft downward,
Thereafter, the welding wire is forwardly fed from the welding torch to the workpiece,
When it is determined that the tip of the welding wire is short-circuited with the workpiece, the forward feeding of the welding wire is continued or stopped, and the power supplied to the solenoid coil is stopped to stop the solenoid shaft. The welding torch is moved upward by the spring, the tip of the welding wire is moved away from the work piece to generate an initial arc, and then the welding wire is constantly fed and steady. Arc start method of robot arc welding to shift to arc.

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