JP2011073004A - Arc welding method and arc welding system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an arc welding method and an arc welding system, capable of forming more beautiful flaky beads. <P>SOLUTION: The arc welding method includes a first step of executing the droplet transfer while generating an arc a by causing the welding current Iw to flow between a welding wire 15 and a welding base metal W so that the mean value of the absolute value of the welding current is the current value iw1, and a second step of continuing the state where the arc a is generated by causing the welding current Iw to flow so that the mean value of the absolute value is the current value is1 smaller than the current value iw1, and repeats the first step and the second step, and further includes a step of maintaining the state where the arc a is extinguished until the time t3 when starting the first step next to the second step if the arc a is extinguished at the time tv1 in the second step. In this constitution, the arc need not be generated again until the time t3. Thus, degradation of the bead appearance which can occur if the arc a is re-generated until the time t3 can be avoided, and a more beautiful bead can be formed thereby. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an arc welding method and an arc welding system.

  FIG. 6 is a diagram illustrating an example of a conventional welding system. The welding system 91 in the figure performs welding using a so-called stitch pulse welding method. The stitch pulse welding method is a welding method in which the heat effect on the base metal is easily suppressed by controlling the heat input and cooling during welding. When this stitch pulse welding method is used, it is said that the welding appearance can be improved and the amount of welding distortion can be reduced as compared with conventional thin plate welding (see, for example, Patent Document 1).

  The manipulator 9M automatically performs arc welding on the workpiece 9W, and includes an upper arm 93, a lower arm 94, a wrist portion 95, and a plurality of servo motors (not shown) for rotationally driving them. It is configured.

  The arc welding torch 9T is attached to the tip of the wrist portion 95 of the manipulator 9M, and is used to guide the welding wire 97 having a diameter of about 1 mm wound around the wire reel 96 to the teaching welding position of the workpiece 9W. It is. The welding power source 9WP supplies a welding voltage between the arc welding torch 9T and the workpiece 9W. When welding the workpiece 9W, the welding wire 97 is protruded from the tip of the arc welding torch 9T by a desired protruding length.

  The conduit cable 92 includes a coil liner (not shown) for guiding the welding wire 97 therein, and is connected to the arc welding torch 9T. Further, the conduit cable 92 supplies the electric power from the welding power source 9WP and the shield gas from the gas cylinder 98 to the arc welding torch 9T.

  The teach pendant 9TP as an operation means is a so-called portable operation panel, and is used to set conditions necessary for performing the operation of the manipulator 9M, stitch pulse welding, and the like.

  The robot controller 9RC is for causing the manipulator 9M to control the welding operation, and includes a main controller, an operation controller, a servo driver (all not shown), and the like. Then, based on a work program taught by the teach pendant 9TP, an operation control signal is output from the servo driver to each servo motor of the manipulator 9M, and a plurality of axes of the manipulator 9M are rotated. Since the robot controller 9RC recognizes the current position based on an output from an encoder (not shown) provided in the servo motor of the manipulator 9M, the robot controller 9RC can control the tip position of the arc welding torch 9T. In the welded portion, stitch pulse welding is performed while repeating the welding, movement, and cooling described below.

  FIG. 7 is a diagram for explaining a state when stitch pulse welding is performed. The welding wire 97 protrudes from the tip of the arc welding torch 9T. The shield gas G is always blown from the arc welding torch 9T at a constant flow rate from the start of welding to the end of welding. Hereinafter, each state at the time of stitch pulse welding will be described.

  FIG. 4A shows a state when an arc is generated. Based on the set welding current and welding voltage, an arc a is generated between the tip of the welding wire 97 and the workpiece 9W, and the welding wire 97 melts to form a molten pool Y in the workpiece 9W. After the arc a is generated, the arc a is stopped after the taught welding time has elapsed.

  FIG. 2B shows a state after the arc is stopped. After the arc is stopped, the state after welding is maintained until the set cooling time has elapsed. That is, since the manipulator 9M and the arc welding torch 9T are stopped in the same manner as the welding state, only the shielding gas G is blown out from the arc welding torch 9T. It cools and solidifies.

  FIG. 5C shows a state where the arc welding torch 9T is moved to the next welding position. After the elapse of the cooling time, the arc welding torch 9T is moved to an arc restart point that is a position separated by a preset movement pitch Mp in the welding progress direction. The moving speed at this time is the set moving speed. The movement pitch Mp is a distance adjusted so that the welding wire 97 is positioned on the outer peripheral side of the welding mark Y ′ after the molten pool Y is solidified as shown in FIG.

  FIG. 4D shows how the arc a is regenerated at the arc restart point. The weld pool Y is newly formed at the front end portion of the welding mark Y ', and welding is performed. As described above, in the stitch pulse welding system 91, the state in which welding is performed by generating an arc and the state in which cooling and movement are performed are alternately repeated. And a welding bead is formed so that the scale which is a welding trace may overlap.

  FIG. 8 is a view for explaining a weld bead formed after welding. As shown in the figure, a welding mark Sc is formed at the first arc starting point P1, and a similar welding mark Sc is also formed at a re-arc starting point P2 that is separated by a moving pitch Mp toward the welding traveling direction Dr. . Further welding marks Sc are sequentially formed after the re-arc start point P3. As described above, the scale-shaped weld beads B are formed as a result of the scales being the welding marks Sc being overlapped.

  In the method described above, as shown in FIGS. 7B, 7C, etc., the process of stopping the arc a and then regenerating the arc a is repeated. It takes time to regenerate arc a. Therefore, the above-described method has a problem that the welding time becomes long. Therefore, as shown in FIG. 9, a welding method has been proposed in which the arc a is not stopped and the re-generation of the arc a is unnecessary (for example, see Patent Document 2).

  As clearly shown in FIGS. 9B and 9C, unlike the case shown in FIGS. 7B and 7C, the arc a is stopped when the molten pool Y is cooled. The state where the arc a is generated is maintained. Thereby, shortening of welding time is achieved.

  However, as shown in FIGS. 9B and 9C, when the molten pool Y is cooled, it is necessary to make the welding current extremely small in order to prevent droplet transfer. If the welding current is reduced, arc breakage may occur when the weld pool Y is being cooled. When an arc break occurs, the arc a is usually regenerated immediately when the arc break occurs. When the arc a is regenerated, spatter is generated, which may deteriorate the appearance of the scale-shaped bead.

JP-A-6-55268 Japanese Patent Laid-Open No. 11-267839

  The present invention has been conceived under the circumstances described above, and an object of the present invention is to provide an arc welding method and an arc welding apparatus capable of forming a cleaner scale-like bead.

  The arc welding method provided by the first aspect of the present invention generates an arc by flowing a welding current between a consumable electrode and a base material so that an average value of absolute values is a first value. The first step of transferring the droplet while causing the welding current to flow and the welding current to flow so that the average value of the absolute values is a second value smaller than the first value, and the state where the arc is generated is continued. An arc welding method in which the first step and the second step are repeated, and when the arc disappears in the second step, the first step subsequent to the second step. The method further includes the step of maintaining the arc extinguished state until the start of the arc.

  According to such a configuration, it is not necessary to regenerate the arc before the start of the next first step. Therefore, it is possible to avoid the deterioration of the bead appearance that may occur when the arc is regenerated before the start of the next first step. Thereby, a more beautiful scale-like bead can be formed.

  In a preferred embodiment of the present invention, the method further includes a step of detecting the disappearance of the arc by detecting that the welding current is stopped. When the arc disappears in a state where the consumable electrode and the base material are separated from each other, energization of the welding current is stopped. Therefore, this configuration is suitable for detecting that the arc has disappeared.

  In a preferred embodiment of the present invention, in the step of maintaining the extinguished state of the arc, the consumable electrode is always attached to the base material in the welding progress direction in the in-plane direction of the base material. Move relative. In such a configuration, the consumable electrode is not moved or stopped in the direction opposite to the welding progress direction in the step of maintaining the arc extinguished state. Therefore, the consumable electrode can be moved earlier to a position where the next first step is started. Thereby, the time required for the arc welding can be shortened.

  In a preferred embodiment of the present invention, in the step of feeding the consumable electrode toward the base material at a predetermined feeding speed and maintaining the state where the arc disappears, the feeding speed is reduced. The method further includes a step.

  In a preferred embodiment of the present invention, in the step of maintaining the arc extinguished state, the output of the current control means for causing the welding current to flow between the consumable electrode and the base material is reduced.

  In a preferred embodiment of the present invention, the first step subsequent to the step of maintaining the arc extinguished state is performed by retracting the consumable electrode from the base material after the consumable electrode is brought into contact with the base material. Start by using the start method. According to such a configuration, it is possible to suppress the occurrence of sputtering at the start of the next first step.

  In a preferred embodiment of the present invention, when the arc is extinguished in the second step, the method further includes a step of changing the second value to a value larger than the previous value when the arc is extinguished. According to such a configuration, after the step of changing is performed, the arc is less likely to disappear in the second step. This reduces the need to regenerate the arc. Therefore, the generation of spatter can be further suppressed. As a result, the appearance of the bead formed on the base material can be made cleaner.

  An arc welding system provided by the second aspect of the present invention is an arc welding system for performing welding by generating an arc by flowing a welding current between a consumable electrode and a base material. A first period in which the average value of the absolute values is set to a first value, and a second period in which the average value of the absolute values of the welding currents is set to a second value smaller than the first value When the detection means determines that the arc has disappeared in the second period, the second current control means for repeatedly generating the current and the detection means for detecting that the arc has disappeared, The arc is extinguished until the first period following the period is started.

  Such an arc welding system is suitable for using the arc welding method provided by the first aspect of the present invention.

  In a preferred embodiment of the present invention, the detecting means detects that the arc has disappeared by detecting that the welding current has been stopped.

  In a preferred embodiment of the present invention, during the period in which the arc is kept extinguished, the consumable electrode is always attached to the base material in the welding progress direction in the in-plane direction of the base material. Consumable electrode moving means for relative movement is further provided.

  In a preferred embodiment of the present invention, the apparatus further comprises a feeding control means for feeding the consumable electrode toward the base material at a predetermined feeding speed, wherein the feeding control means is in a state where the arc is extinguished. In the period for maintaining the above, the feeding speed is reduced.

  In a preferred embodiment of the present invention, the current control means reduces an output for allowing the welding current to flow between the consumable electrode and the base material during a period in which the arc is maintained extinguished.

  In a preferred embodiment of the present invention, the first period subsequent to maintaining the extinguished state of the arc is separated from the base material after the consumable electrode is brought into contact with the base material. Start by using the retract start method.

  In a preferred embodiment of the present invention, when the arc disappears in the first period, the detecting means determines that the arc has disappeared after a first delay time has elapsed since the arc disappeared. In addition, when the arc disappears in the second period, it is determined that the arc has disappeared after a second delay time shorter than the first delay time has elapsed since the arc disappeared.

  In a preferred embodiment of the present invention, when the detecting means determines that the arc has disappeared in the second period, the current control means sets the second value before the time when the arc has disappeared. Change to a value greater than the value.

  Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

It is a figure showing composition of an example of a welding system concerning a 1st embodiment of the present invention. It is a figure which shows the internal structure of the welding system shown in FIG. It is a figure which shows timing charts, such as each signal of the welding system concerning 1st Embodiment. It is a figure which shows the change of the welding current in a droplet transfer period. It is a figure which shows timing charts, such as each signal of the welding system concerning 2nd Embodiment. It is a figure which shows the structure of an example of the conventional welding system. It is a figure explaining a state when performing stitch pulse welding. It is a figure for demonstrating the weld bead formed after welding construction. It is a figure for demonstrating a state when performing stitch pulse welding.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration of an example of a welding system according to a first embodiment of the present invention.

  A welding system A shown in FIG. 1 includes a welding robot 1, a robot control device 2, and a welding power source device 3. The welding robot 1 automatically performs, for example, arc welding on the welding base material W. The welding robot 1 includes a base member 11, a plurality of arms 12, a plurality of motors 13, a welding torch 14, a wire feeding device 16, and a coil liner 19.

  The base member 11 is fixed to an appropriate location such as a floor. Each arm 12 is connected to the base member 11 via a shaft.

  The welding torch 14 is provided at the distal end portion of the wrist portion 12 a provided on the most distal end side of the welding robot 1. The welding torch 14 guides a welding wire 15 having a diameter of, for example, about 1 mm as a consumable electrode to a predetermined position in the vicinity of the welding base material W. The welding torch 14 is provided with a shield gas nozzle (not shown) for supplying a shield gas such as Ar. The motor 13 is provided at both ends or one end of the arm 12 (partially omitted from illustration). The motor 13 is rotationally driven by the robot control device 2. By this rotational drive, the movement of the plurality of arms 12 is controlled, and the welding torch 14 can move freely up and down, front and rear, and left and right.

  The motor 13 is provided with an encoder (not shown). The output of this encoder is given to the robot controller 2. Based on this output value, the robot controller 2 recognizes the current position of the welding torch 14.

  The wire feeding device 16 is provided in the upper part of the welding robot 1. The wire feeding device 16 is for feeding the welding wire 15 to the welding torch 14. The wire feeding device 16 includes a feeding motor 161, a wire reel (not shown), and wire push means (not shown). Using the feed motor 161 as a drive source, the wire push means feeds the welding wire 15 wound around the wire reel to the welding torch 14.

  One end of the coil liner 19 is connected to the wire feeder 16 and the other end is connected to the welding torch 14. The coil liner 19 is formed in a tube shape, and a welding wire 15 is inserted through the coil liner 19. The coil liner 19 guides the welding wire 15 delivered from the wire feeding device 16 to the welding torch 14. The fed welding wire 15 protrudes outside from the welding torch 14 and functions as a consumable electrode.

  FIG. 2 is a diagram showing an internal configuration of welding system A shown in FIG.

  The robot control device 2 shown in FIGS. 1 and 2 is for controlling the operation of the welding robot 1. As shown in FIG. 2, the robot control device 2 includes an operation control circuit 21 and an interface circuit 22.

  The operation control circuit 21 has a microcomputer and a memory (not shown). The memory stores a work program in which various operations of the welding robot 1 are set. Further, the operation control circuit 21 sets a robot moving speed VR described later. The operation control circuit 21 gives an operation control signal Mc to the welding robot 1 based on the work program, the coordinate information from the encoder, the robot moving speed VR, and the like. By this operation control signal Mc, each motor 13 is rotationally driven, and the welding torch 14 is moved to a predetermined welding start position of the welding base material W or moved along the in-plane direction of the welding base material W.

  An operation setting device (not shown) is connected to the operation control circuit 21. This operation setting device is for setting various operations by the user.

  The interface circuit 22 is for exchanging various signals with the welding power source device 3. The interface circuit 22 is supplied with a current setting signal Is, an output start signal On, and a feed speed setting signal Ws from the operation control circuit 21. An arc extinction signal Sa is sent from the interface circuit 22 to the operation control circuit 21.

  The welding power supply device 3 is a device for applying a welding voltage Vw between the welding wire 15 and the welding base material W and flowing a welding current Iw, and for feeding the welding wire 15. is there. As shown in FIG. 2, the welding power source device 3 includes an output control circuit 31, a current detection circuit 32, an arc extinction detection circuit 33, a feed control circuit 34, an interface circuit 35, and a voltage detection circuit 36.

  The interface circuit 35 is for exchanging various signals with the robot control device 2. Specifically, the current setting signal Is, the output start signal On, and the feed speed setting signal Ws are sent from the interface circuit 22 to the interface circuit 35. Further, an arc extinction signal Sa is sent from the interface circuit 35 to the interface circuit 22.

  The output control circuit 31 has an inverter control circuit composed of a plurality of transistor elements. The output control circuit 31 performs precise welding current waveform control with a high-speed response to a commercial power source (for example, three-phase 200 V) input from the outside by an inverter control circuit.

  The output of the output control circuit 31 has one end connected to the welding torch 14 and the other end connected to the welding base material W. The output control circuit 31 applies a welding voltage Vw between the welding wire 15 and the welding base material W via a contact tip provided at the tip of the welding torch 14 and causes a welding current Iw to flow. Thereby, an arc a is generated between the tip of the welding wire 15 and the welding base material W. The welding wire 15 is melted by the heat generated by the arc a. The welding base material W is welded.

  The output control circuit 31 is supplied with the current setting signal Is and the output start signal On from the operation control circuit 21 via the interface circuits 35 and 22.

  The current detection circuit 32 is for detecting the welding current Iw flowing through the welding wire 15. The current detection circuit 32 outputs a current detection signal Id corresponding to the welding current Iw.

  The arc extinction detection circuit 33 is a circuit that detects that the arc a has disappeared. A current detection signal Id is input to the arc extinction detection circuit 33. The arc extinction detection circuit 33 determines that the arc a has disappeared when it is determined that the welding current Iw is 0 based on the input current detection signal Id. At this time, the arc extinction detection circuit 33 outputs an arc extinction signal Sa to the output control circuit 31. The arc extinction detection circuit 33 also outputs an arc extinction signal Sa to the operation control circuit 21 via the interface circuits 35 and 22.

  The arc extinction detection circuit 33 does not immediately determine that the arc a has disappeared upon receiving the current detection signal Id that the welding current Iw is zero. The arc extinction detection circuit 33 receives the current detection signal Id that the welding current Iw is 0 even after a predetermined delay time has elapsed since the input of the current detection signal Id that the welding current Iw is 0. If it is, it is determined that arc a has disappeared. Note that the current detection circuit 32 may be provided with a determination function using this delay time.

  The voltage detection circuit 36 is for detecting a welding voltage Vw that is a voltage at the output terminal of the output control circuit 31. The voltage detection circuit 36 outputs a voltage detection signal Vd corresponding to the welding voltage Vw to the output control circuit 31.

  The feed control circuit 34 outputs a feed control signal Fc for feeding the welding wire 15 to the feed motor 161. The feed control signal Fc is a signal indicating the feed speed Fw of the welding wire 15. In addition, an output start signal On and a feed speed setting signal Ws from the operation control circuit 21 are sent to the feed control circuit 34 via the interface circuits 35 and 22.

  Next, an example of the arc welding method according to the present embodiment will be described with reference to FIG.

  FIG. 4A shows a change state of the robot moving speed VR, FIG. 5B shows a change state of the current setting signal Is, FIG. 5C shows a change state of the welding current Iw, and FIG. The change state of Fw is shown. The robot moving speed VR is a moving speed of the welding torch 14 along a predetermined welding progress direction (corresponding to the welding progress direction Dr of the prior art shown in FIG. 8) in the in-plane direction of the weld base material W. .

  First, a transition welding start process is generally performed by inputting a welding start signal St (see FIG. 2) from the outside. In the welding start process, the operation control circuit 21 outputs an output start signal On to the output control circuit 31 and the feed control circuit 34. The output control circuit 31 applies a welding voltage Vw between the welding wire 15 and the welding base material W. Thereby, the arc a is ignited. And as shown in FIG. 3, welding is performed by repeating the droplet transfer period T1 and the arc continuation period T2. In the droplet transfer period T1, the droplet transfer is performed by flowing the welding current Iw1, and a molten pool is formed. On the other hand, in the arc continuation period T2, the welding torch 14 is moved while flowing the welding current Iw2 with almost no droplet transfer and while maintaining the arc a. This will be specifically described below.

(1) Droplet transfer period T1 (time t1 to t2)
In the droplet transfer period T1, the process for forming the molten pool Y shown in FIGS. 7A and 9A in the description of the prior art is performed. In the droplet transfer period T1, the robot moving speed VR is set to 0 as shown in FIG. Therefore, the welding torch 14 is stopped with respect to the welding base material W. As shown in FIG. 6C, an AC pulse welding current Iw1 having an average absolute value of the current value iw1 flows as the welding current Iw. In the droplet transfer period T1, constant voltage control is performed. In the constant voltage control, the welding current Iw can be supplied to the welding wire 15 shown in FIG. 4D if the welding conditions such as the material, diameter, protruding length of the welding wire 15 and electrode polarity are determined. It is determined by the feeding speed Fw. That is, the welding current Iw1 is determined by the feed speed setting signal Ws that sets the feed speed Fw. In the droplet transfer period T1, the welding wire 15 is fed at a feeding speed Fw of fw1. fw1 is, for example, 650 to 1000 cm / min. Moreover, the droplet transfer period T1 is, for example, 0.4 to 0.5 sec.

  FIG. 4 is a diagram showing in detail the time change of the welding current Iw1. In FIG. 3, the welding current Iw1 is shown in a simplified manner for the sake of understanding, but actually, the welding current Iw1 is an alternating pulse current as shown in FIG. The current value iw1 in FIG. 4 matches the current value iw1 in FIG. The time scale in FIG. 4 is very small compared to the time scale in FIG. In FIG. 4, the vertical axis indicating the welding current Iw is positive for the current that flows when the welding wire 15 becomes the anode.

  As understood from this figure, the welding current Iw1 takes the electrode positive polarity current Iep and the electrode negative polarity current Ien once in the period Te. The period Te is, for example, about 20 msec. The electrode positive polarity current Iep is a current that flows when the welding wire 15 is an anode and the welding base material W is a cathode. The electrode positive polarity current Iep includes a positive polarity peak current Ipp and a positive polarity base current Ipb. The positive polarity peak current Ipp flows during the electrode positive polarity period Tpp. The electrode positive polarity period Tpp is, for example, 2 msec. The absolute value Iepp of the positive polarity peak current Ipp is, for example, 300 to 350A. On the other hand, the positive polarity base current Ipb flows during the electrode positive polarity period Tpb. The electrode positive polarity period Tpb is, for example, 14 msec. The absolute value Iepb of the positive polarity base current Ipb is, for example, 50 to 100A.

  The electrode negative polarity current Ien is a current that flows when the welding wire 15 is a cathode and the welding base material W is an anode. The electrode negative polarity current Ien flows during the electrode negative polarity period Ten. The electrode negative polarity period Ten is, for example, 3.0 to 4.0 msec. The absolute value Ienp of the electrode negative polarity current Ien is, for example, 50 to 100A.

  The positive polarity peak current Ipp, the positive polarity base current Ipp, the electrode negative polarity current Ien, the electrode positive polarity period Tpp, and the electrode negative polarity period Ten are set to predetermined values. The electrode positive polarity period Tpb is feedback controlled so that the average value of the welding voltage becomes equal to a predetermined welding voltage set value. By this control, the length of the arc a is controlled to an appropriate value. A value obtained by averaging the absolute values of the positive polarity peak current Ipp, the positive polarity base current Ipb, and the electrode negative polarity current Ien coincides with the current value iw1. The current value iw1 is, for example, 90A.

(2) Arc duration T2 (time t2 to t3)
In the arc continuation period T2 shown in FIG. 3, the process of cooling the molten pool Y shown in FIGS. 9B and 9C in the description of the prior art is performed while the arc a is continued. The arc duration T2 is, for example, 0.2 to 0.3 sec.

(I) Period from start of arc continuation period T2 to extinction of arc a (time t2 to tv1)
As shown in FIG. 3A, the robot moving speed VR is set to V2 at time t2 when the arc continuation period T2 starts. As a result, the welding torch 14 starts to move along a predetermined welding direction. V2 is, for example, 100 cm / min. In the arc continuation period T2, unlike the droplet transfer period T1, constant current control is performed. As shown in FIG. 5B, the current setting signal Is is set so that a constant current having the current value is1 (that is, the average value of the absolute values is the current value is1) flows as the welding current Iw. . Therefore, as shown in FIG. 5C, a constant welding current Iw2 flows at the current value is1 as the welding current Iw. The current value is1 is, for example, about 15 to 20A. The current value is1 is a small value that is difficult to cause droplet transfer. The welding current Iw2 is a so-called electrode positive polarity current that flows in a state where the welding wire 15 is an anode and the welding base material W is a cathode. As shown in FIG. 4D, the welding wire 15 is fed at a feeding speed Fw of fw2. fw2 is smaller than fw1, for example, 70 cm / min.

(Ii) Period from the extinction of the arc a to the start of the next droplet transfer period T1 (time tv1 to t3)
At time tv1, arc a disappears due to an unintended cause. Then, the welding current Iw becomes 0 as shown in FIG. The current detection circuit 32 of FIG. 2 outputs a current detection signal Id that the welding current Iw is 0 to the arc extinction detection circuit 33. The arc extinction detection circuit 33 determines that the welding current Iw is 0 from the input current detection signal Id. Then, the arc extinction detection circuit 33 determines that the arc a has disappeared. Then, the arc extinction detection circuit 33 outputs an arc extinction signal Sa to the output control circuit 31 and the operation control circuit 21.

  As described above, the arc extinction detection circuit 33 does not immediately determine that the arc a has disappeared upon receiving the current detection signal Id that the welding current Iw is zero. The arc extinction detection circuit 33 receives the current detection signal Id that the welding current Iw is 0 even after a predetermined delay time has elapsed since the input of the current detection signal Id that the welding current Iw is 0. If it is, it is determined that arc a has disappeared. The delay time dt2 in the arc continuation period T2 is preferably shorter than the delay time dt1 in the droplet transfer period T1. The delay time dt2 may be set to 20 to 50 ms, for example, and the delay time dt1 may be set to 100 ms, for example.

  When the operation control circuit 21 receives the arc extinction detection signal Sa, the operation control circuit 21 changes the feed speed setting signal Ws so that the feed speed Fw is zero. As a result, the feeding speed Fw becomes 0 as shown in FIG. 4D, and feeding of the welding wire 15 is stopped. On the other hand, when receiving the arc extinction signal Sa, the output control circuit 31 changes the output to the off state. The process of stopping the feeding of the welding wire 15 or changing the output of the output control circuit 31 to the OFF state is performed to maintain the state where the arc a has disappeared. In order to maintain the state in which the arc a has disappeared, it is not always necessary to completely stop the feeding of the welding wire 15 and to change the output of the output control circuit 31 to the OFF state. The feeding of the welding wire 15 may be continued to such an extent that the arc a can be maintained, and the output of the output control circuit 31 may be maintained in the on state. As shown in FIG. 9A, the robot moving speed VR is maintained at V2 from time tv1 to time t3. Therefore, also from time tv1 to time t3, the welding torch 14 moves along a predetermined welding progress direction without stopping.

(Iii) Next droplet transfer period T1 (time t3 to t4)
As shown in FIG. 4A, at time t3, the robot moving speed VR is set to 0, and the movement of the welding torch 14 is stopped. Further, as shown in FIG. 4D, feeding of the welding wire 15 is started with the feeding speed Fw set to fw3 smaller than fw1. Then, by turning on the output of the output control circuit 31, the arc a is regenerated. In order to regenerate the arc a, various arc start methods can be used. As such an arc start method, for example, a retract start method in which the welding wire 15 is brought into contact with the welding base material W and then the welding wire 15 is separated from the welding base material W can be used. The arc start condition for regenerating arc a may be different from the arc start condition for generating arc a in arc welding performed before time tv1 when arc a disappeared. Such arc start conditions include the magnitude of the start current and the time during which the start current is applied. Then, after the arc a is generated, the feeding speed Fw is changed to fw1 as shown in FIG. Then, arc welding is performed again.

  Next, the operation of this embodiment will be described.

  According to this embodiment, when the droplet transfer period T1 and the arc transfer period T2 are smoothly repeated without the arc a disappearing, a clean scale-shaped bead can be formed. Furthermore, according to the present embodiment, even if the arc a disappears accidentally at the time tv1 of the arc transition period T2, the arc a is regenerated from the time tv1 to the time t3 when the droplet transition period T1 is resumed. It is not necessary to let them. Therefore, it is possible to avoid the deterioration of the bead appearance that may occur when arc a is regenerated from time tv1 to time t3. Thereby, a more beautiful scale-like bead can be formed.

  According to the present embodiment, as shown in FIG. 3A, in the droplet transfer period T1, the welding torch 14 is stopped with respect to the welding base material W, and only in the arc continuation period T2, the welding torch 14 is stopped. The welding base material W is moved. This is suitable for forming a bead with a cleaner appearance.

  Also, at time tv1 to time t3, the welding torch 14 moves along a predetermined welding progress direction without stopping. Therefore, the welding torch 14 can be moved faster to a position where the droplet transfer period T1 starts. Thereby, the time which welding requires can be shortened.

  As shown in FIG. 5C, the arc a disappears in a state where the welding wire 15 and the welding base material W are separated from each other at time tv1, the welding current Iw becomes 0, and the welding current Iw becomes 0. Is detected by the current detection circuit 33. Such a configuration is suitable for detecting that the arc a has disappeared.

  Further, when the delay time dt2 in the arc continuation period T2 is set shorter than the delay time dt1 in the droplet transfer period T1, the feeding of the welding wire 15 is stopped earlier, or the output of the output control circuit 31 is changed. It can be changed to an off state. Therefore, by setting the delay time dt2 in the arc continuation period T2 to be shorter than the delay time dt1 in the droplet transfer period T1, it is possible to stop the welding wire 15 from approaching the welding base material W earlier. Thereby, the state in which the arc a is extinguished can be maintained more reliably.

  When the arc a disappears at time tv1, the feeding of the welding wire 15 is completely stopped. Further, when the arc a disappears at time tv1, the output of the output control circuit 31 is changed to the off state. Therefore, it becomes difficult for the welding wire 15 to approach the welding base material W after the arc a disappears. That is, the configuration according to the present embodiment is suitable for maintaining the state where the arc a is extinguished.

  In the present embodiment, the arc a is not regenerated during the arc continuation period T2, but the arc a is regenerated at the start of the droplet transfer period T1. Therefore, various arc start methods can be used to regenerate arc a. Thereby, as an arc start method for regenerating the arc a, a method in which sputtering is less likely to occur, such as a retract start method, can be used.

  As shown in FIG. 4, the welding current Iw1 is an alternating pulse current. Therefore, heat input to the welding base material W in the droplet transfer period T1 can be suppressed. This is suitable when the welding base material W is a thin plate made of, for example, aluminum.

  The welding current Iw2 is a so-called electrode positive polarity current. If the welding current Iw2 is an electrode negative polarity current that flows in a state where the welding wire 15 is a cathode and the welding base material W is an anode, the welding wire 15 has a large amount of melting and droplets are transferred to the welding base material W. Inconveniences such as falling easily occur. However, in this embodiment, since the welding current Iw2 is not an electrode minus polarity current but an electrode plus polarity current, such inconvenience hardly occurs.

  Moreover, you may use the method concerning this embodiment in the state which inclined the welding base material W with respect to the horizontal direction. If it does in this way, a droplet will be hard to fall to welding base material W. As a result, a cleaner bead can be formed.

  FIG. 5 shows a second embodiment of the present invention. In the figure, the same or similar elements as those of the above embodiment are denoted by the same reference numerals as those of the above embodiment. This embodiment is different from the first embodiment in that the current setting signal Is is increased from the current value is1 to the current value is2 at time t4 after the arc a disappears.

  In this step of increasing the current setting signal Is, the operation control circuit 21 in FIG. 2 having input the arc extinction signal Sa at time tv1 increases the current setting signal Is from the current value is1 to the current value is2 at time t4. Do. The operation control circuit 21 outputs to the output control circuit 31 a current setting signal Is that has increased from the current value is1 to the current value is2. When the current setting signal Is increased to the current value is2, the output control circuit 31 causes the welding current Iw2 to flow at the current value is2 as shown in FIG.

  The current value is2 is, for example, about 1 to 10 A larger than the current value is1. Note that when the arc a disappears again after time t4, the current setting signal Is may be further increased.

  According to the present embodiment, the welding current Iw2 flows at the current value is2 during the arc continuation period T2 after time t4. Therefore, the arc a is less likely to disappear during the arc continuation period T2 after time t4. This reduces the need to regenerate arc a after time t4. Therefore, it is possible to suppress the occurrence of spatter in the weld base material W. As a result, according to the present embodiment, the appearance of the scale-shaped bead formed on the weld base material W can be further cleaned.

  In addition, this embodiment has the same advantages as the first embodiment.

  In the present embodiment, an example is shown in which the current setting signal Is is increased with the disappearance of the arc a only once at time tv1, but the current setting signal Is is increased only when the arc a disappears a plurality of times. May be. It is possible to suppress the welding current Iw2 from becoming excessively large by increasing the current setting signal Is only when the arc a disappears a plurality of times. Thereby, it can suppress that the welding wire 15 and the welding preform | base_material W fuse | melt in the arc continuation period T2.

  The current setting signal Is may be increased based on the extinction of the arc a, and it is not always necessary to increase the current setting signal Is at time t4. For example, the current setting signal Is may be raised during the arc continuation period T2. Alternatively, the current setting signal Is may be raised at time t6.

  The scope of the present invention is not limited to the embodiment described above. The specific configuration of the present invention can be modified in various ways. In the above embodiment, it is detected that the arc has disappeared when the welding current becomes 0. For example, by analyzing a change in an image or video of a portion where the arc is generated, the arc disappears. May be detected. Alternatively, when the arc voltage disappears when the welding voltage Vw exceeds a threshold voltage (for example, a value slightly smaller than the no-load voltage) set in the arc continuation period T2 and the welding voltage Vw exceeds the threshold voltage. By determining, the disappearance of the arc may be detected.

  In order to form a cleaner bead appearance, it is preferable to set the robot moving speed VR to 0 in the droplet transfer period T1, but the present invention is not limited to this. For example, the robot movement speed VR in the droplet transfer period T1 may be set to a value smaller than the robot movement speed VR (V2) in the arc continuation period T2 and greater than zero. Then, the droplet transfer period T1 and the arc continuation period T2 may be appropriately adjusted according to the robot moving speed VR.

  In the above, an example in which the welding current Iw1 is an AC pulse current has been shown, but the present invention is not limited to this, and the welding current Iw1 may be a DC constant current or the like. Of course, the same applies to the welding current Iw2.

A welding system 1 welding robot 11 base member 12 arm 12a wrist 13 motor 14 welding torch 15 welding wire (consumable electrode)
16 Wire feeder 161 Feed motor 2 Robot controller 21 Operation control circuit (consumable electrode moving means)
22 Interface circuit 3 Welding power supply 31 Output control circuit (current control means)
32 Current detection circuit 33 Arc extinction detection circuit (detection means)
34 Feed control circuit 35 Interface circuit 36 Voltage detection circuit W Welding base material (base material)
St Welding start signal On Output start signal Sa Arc extinction signal Ws Feeding speed setting signal Mc Operation control signal Fc Feeding control signal VR Robot movement speed Iw, Iw1, Iw2 Welding current iw1 Current value (first value)
Vw welding voltage T1 droplet transfer period (first period)
T2 Arc duration (second period)
Iep electrode plus polarity current Ien electrode minus polarity current Ipp plus polarity peak current Ipb plus polarity base current Te period Tpp, Tpb electrode plus polarity period Ten electrode minus polarity period Is current setting signals is1, is2 current value (second value)
dt1 (first) delay time dt2 (second) delay time Fw Feeding speed

Claims (15)

A first step of transferring a droplet while generating an arc by flowing a welding current between the consumable electrode and the base material so that the average value of the absolute values is the first value;
Passing the welding current such that the average value of the absolute values is a second value smaller than the first value, and continuing the state in which the arc is generated, and
An arc welding method for repeating the first step and the second step,
The arc welding method further comprising a step of maintaining the arc extinguished until the first step after the second step is started when the arc is extinguished in the second step. .   The arc welding method according to claim 1, further comprising a step of detecting that the arc has disappeared by detecting that energization of the welding current is stopped.   In the step of maintaining the extinguished state of the arc, the consumable electrode is always moved relative to the base material in the welding progress direction in the in-plane direction of the base material. The described arc welding method. The consumable electrode is fed toward the base material at a predetermined feeding speed,
The arc welding method according to any one of claims 1 to 3, further comprising a step of reducing the feeding speed in the step of maintaining the extinguished state of the arc.   The arc welding method according to any one of claims 1 to 4, wherein, in the step of maintaining the extinguished state of the arc, the output of current control means for causing the welding current to flow between the consumable electrode and the base material is reduced. .   The first step following the step of maintaining the extinguished state of the arc is started by using a retract start method in which the consumable electrode is brought into contact with the base material and then the consumable electrode is separated from the base material. Item 6. The arc welding method according to any one of Items 1 to 5.   The arc according to any one of claims 1 to 6, further comprising a step of changing the second value to a value larger than a previous value when the arc disappears when the arc disappears in the second step. Welding method. An arc welding system that performs welding by generating an arc by passing a welding current between a consumable electrode and a base material,
A first period in which the average value of the absolute value of the welding current is set to a first value, and an average value of the absolute value of the welding current is set to a second value that is smaller than the first value. Current control means for repeatedly generating the second period;
Detecting means for detecting the disappearance of the arc,
When the detecting means determines that the arc has disappeared in the second period, the arc is maintained extinguished until the first period following the second period is started. And arc welding system.   The arc welding system according to claim 8, wherein the detection means detects that the arc has disappeared by detecting that energization of the welding current is stopped.   In a period for maintaining the arc extinguished state, it further comprises consumable electrode moving means for constantly moving the consumable electrode relative to the base material in the welding progress direction in the in-plane direction of the base material. An arc welding system according to claim 8 or 9. A feeding control means for feeding the consumable electrode toward the base material at a predetermined feeding speed;
The arc welding system according to any one of claims 8 to 10, wherein the feeding control means reduces the feeding speed during a period in which the arc disappears.   The said current control means reduces the output for flowing the said welding current between the said consumable electrode and the said base material in the period which maintains the state which the said arc extinguished. Arc welding system.   The first period subsequent to maintaining the extinguished state of the arc is started by using a retract start method in which the consumable electrode is brought into contact with the base material and then the consumable electrode is separated from the base material. The arc welding system according to any one of claims 8 to 12.   When the arc disappears in the first period, the detection means determines that the arc has disappeared after the first delay time has elapsed since the arc disappeared, and in the second period The arc according to any one of claims 8 to 13, wherein when the arc is extinguished, it is determined that the arc has disappeared after a second delay time shorter than the first delay time from the extinction of the arc. Arc welding system.   The current control means changes the second value to a value larger than the previous value when the arc disappears when the detection means determines that the arc has disappeared in the second period. The arc welding system according to any one of 8 to 14.

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