JP2011073039A - 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 a scale-like bead with a better appearance. <P>SOLUTION: The arc welding method includes: a first step of transferring a molten droplet while generating an arc a by passing a welding current between a consumable electrode 15 and a welding base material W in such a manner that the average value of absolute values is a first value; and a second step of keeping the state in which the arc is generated by passing the welding current in such a manner that the average value of absolute values is a second value smaller than the first value, wherein the first and second steps are alternately repeated. In the second step, a feeding speed Vf of the consumable electrode is increased when an welding voltage Vw between the consumable electrode 15 and the base material W is larger than a predetermined standard welding voltage Vst; and the feeding speed Vf is decreased when the welding voltage Vw is smaller than the standard welding voltage Vst. By the way, the method can suppress confusion in the appearance of the welding bead, which is caused by an excessive welding-voltage, or disappearance of the arc, which is caused by an insufficient welding-voltage. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

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

  FIG. 7 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. 8 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. 9 is a diagram 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 above-described method, as shown in FIGS. 8B and 8C, 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. Further, each time the arc a is regenerated, there is a problem that spatter is generated and the appearance of the weld bead B is deteriorated. Therefore, as shown in FIG. 10, a welding method has been proposed in which the arc a is not stopped and the re-generation of the arc a is not required (see, for example, Patent Document 2).

  As clearly shown in FIGS. 10B and 10C, unlike the cases shown in FIGS. 8B and 8C, 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. Moreover, since it is no longer necessary to regenerate the arc a, it is possible to suppress the occurrence of sputtering.

  However, as shown in FIGS. 10B and 10C, when the molten pool Y is cooled, it is necessary to make the welding current extremely small in order to prevent droplet transfer. When the welding current is reduced, arc breakage frequently occurs when the molten pool Y is cooled. If the arc break frequently occurs, the appearance of the weld bead B is deteriorated. Thus, the method shown in FIG. 10 was not sufficient to prevent the appearance of the weld bead B from deteriorating.

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 system capable of forming a more beautiful 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 that repeats the first step and the second step, wherein a welding voltage between the consumable electrode and the base material is predetermined in the second step. When the welding voltage is higher than the reference welding voltage, the feeding speed of the consumable electrode is increased, and when the welding voltage is lower than the reference welding voltage, the feeding speed is reduced.

  According to such a configuration, for example, when the arc length varies from a desired size due to variation in the distance between the consumable electrode and the base material, the variation is determined as a difference between the welding voltage and the reference welding voltage. Can be detected. Then, the welding voltage can be controlled to become the reference welding voltage by increasing / decreasing the feeding speed of the consumable electrode according to the voltage difference. That the welding voltage is the reference welding voltage means that the arc length is maintained at a desired magnitude. Therefore, it is possible to avoid a situation where an arc break occurs due to the arc length becoming too long, or a short circuit occurs due to the arc length becoming too short.

  In a preferred embodiment of the present invention, when the voltage difference between the welding voltage and the reference welding voltage is smaller than a predetermined voltage difference threshold, the feeding speed is not changed.

  In a preferred embodiment of the present invention, the feeding speed is set stepwise with respect to the voltage difference.

  In a preferred embodiment of the present invention, the welding current in the second step is a direct current.

  In a preferred embodiment of the present invention, constant current control is performed on the welding current in the second step.

  In a preferred embodiment of the present invention, the welding current in the first step is an alternating pulse current.

  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. It repeats the 1st period which sets the average value of an absolute value to the 1st value, and the 2nd period which sets the average value of the absolute value of the above-mentioned welding current to the 2nd value smaller than the 1st value Current control means to be generated; welding voltage detection means for detecting a welding voltage between the consumable electrode and the base material; and when the welding voltage is higher than a predetermined reference welding voltage in the second period. And a feed rate setting means for increasing the feed rate of the consumable electrode and decelerating the feed rate when the welding voltage is lower than the reference welding voltage.

  In a preferred embodiment of the present invention, when the voltage difference between the welding voltage and the reference welding voltage is smaller than a predetermined voltage difference threshold value, the feeding speed setting means sets the feeding speed. It does not change.

  In a preferred embodiment of the present invention, the feed speed setting means sets the feed speed stepwise with respect to the voltage difference.

  In a preferred embodiment of the present invention, the welding current in the second period is a direct current.

  In a preferred embodiment of the present invention, the current control means performs constant current control on the welding current in the second period.

  In a preferred embodiment of the present invention, the welding current in the first period is an AC pulse current.

  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 which shows the structure of an example of the welding system concerning this 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 the relationship between the welding voltage and arc length in an arc continuation period. It is a figure which shows the relationship between the voltage difference and pitching speed difference in a feeding speed setting circuit. 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.

  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, a feed speed setting 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.

  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 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 feed speed setting circuit 33.

  The feed speed setting circuit 33 is a circuit that performs increase / decrease processing based on the voltage detection signal Vd with respect to the feed speed setting signal Ws sent from the interface circuit 35. The feed speed setting signal Ws processed by the feed speed setting circuit 33 is sent to the feed control circuit 34.

  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 Vf of the welding wire 15. In addition, an output start signal On from the operation control circuit 21 and a feed speed setting signal Ws from the feed speed setting circuit 33 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 invention will be described with reference to FIG.

  FIG. 5A shows a change state of the robot moving speed VR, and FIG. 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. 9) 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. 8A and 10A 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. 6B, 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 is determined by the feeding speed Vf of the welding wire 15 if welding conditions such as the material, diameter, protruding length of the welding wire 15 and electrode polarity are determined. That is, the welding current Iw1 is set by the feed speed setting signal Ws. Feeding speed Vf of welding wire 15 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 the welding current Iw1 is an AC 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 Vw becomes equal to a predetermined welding voltage setting 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 t1)
In the arc continuation period T2 shown in FIG. 3, the process for cooling the molten pool Y shown in FIGS. 10B and 10C 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.

  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 welding current Iw is set to flow as a welding current Iw2 having a current value is1. 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. The welding wire 15 is fed toward the welding base material W at a feeding speed Vf that is smaller than the value in the droplet transfer period T1 (not shown). This feed speed Vf is, for example, 70 cm / min.

  FIG. 5 shows the behavior that the welding voltage Vw can take in the arc continuation period T2 when the feed speed setting circuit 33 of this embodiment is not functioning. Constant current control is performed in the arc continuation period T2. That is, the welding current Iw is made constant by controlling the welding current Vw in the output control circuit 31 based on the current detection signal Id from the current detection circuit 32.

  One of the causes for increasing or decreasing the welding voltage Vw for the purpose of realizing a constant current is a variation in the distance D between the welding wire 15 and the welding base material W. Since the distance D is not a physical quantity that is directly measured and controlled, it can vary depending on the welding conditions. For example, the flatness of the welding base material W, the teaching accuracy of the welding robot 1, and the frictional force that acts to hinder the feeding of the welding wire 15 are included. When the distance D becomes smaller, control is performed to reduce the welding voltage Vw in order to maintain a constant current. On the other hand, when the distance D increases, control is performed to increase the welding voltage Vw in order to maintain a constant current.

  In the present embodiment, the feed speed setting circuit 33 calculates a voltage difference ΔV between the welding voltage Vw and the reference welding voltage Vst from the input voltage detection signal Vd. The reference welding voltage Vst is a value that can be empirically determined in advance from the welding base material W, the welding wire 15, the welding speed VR, and the current value is1. Next, the feed speed setting circuit 33 determines the feed speed difference ΔWs from the voltage difference ΔV. For this determination, for example, a graph shown in FIG. 6 is used.

  As shown in FIG. 6, when the voltage difference ΔV = 0, that is, when the welding voltage Vw is equal to the reference welding voltage Vst, the feeding speed difference ΔWs is set to zero. In this embodiment, when the absolute value of the voltage difference ΔV is equal to or less than the voltage difference threshold value ΔVth, the feeding speed difference ΔWs is set to 0. When the absolute value of the voltage difference ΔV is larger than the voltage difference threshold value ΔVth, the feeding speed difference ΔWs is set according to the illustrated graph. In the present embodiment, the voltage difference ΔV and the feeding speed difference ΔWs are in a step-like relationship.

  The feed speed setting circuit 33 adds the determined feed speed difference ΔWs to the feed speed setting signal Ws. As a result, the feed speed setting signal Ws increased or decreased according to the voltage difference ΔV is sent to the feed control circuit 34. As a result, the feeding speed Vf of the welding wire 15 is increased or decreased.

  Thereafter, the droplet transfer period T1 starts again from time t1. In this way, the droplet transfer period T1 and the arc continuation period T2 are repeated.

  Next, the operation of this embodiment will be described.

  According to the present embodiment, when the distance D between the welding wire 15 and the welding base material W varies due to the above-described factors, the voltage difference ΔV varies according to the variation. The feed speed setting circuit 33 performs control to increase / decrease the feed speed Vf based on the voltage difference ΔV. The feeding speed Vf is increased or decreased so that the welding voltage Vw approaches the reference welding voltage Vst. As a result, the length of the arc a is kept at a desirable length when the welding voltage Vw takes the reference welding voltage Vst. Therefore, it is possible to avoid a situation in which the length of the arc a becomes too long and the arc is cut off, or the length of the arc a becomes too short and a short circuit occurs. This is suitable for continuing the arc welding stably and preventing the appearance of the weld bead from being disturbed.

  When the voltage difference ΔV is equal to or less than the voltage difference threshold value ΔVth, the feeding speed difference ΔWs is set to 0 to prevent the feeding speed Vf from being frequently accelerated or decelerated due to the occurrence of the minute voltage difference ΔV. Can do. Frequent acceleration / deceleration that is not intended may cause undue hunting or the like even if the acceleration / deceleration amount is very small. According to the present embodiment, such disturbance of control can be suppressed. Setting the voltage difference ΔV and the feeding speed difference ΔWs in a stepped manner is easy to use because the relationship between the voltage difference ΔV and the feeding speed difference ΔWs can be input and held, for example, in the form of a table. .

  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, the voltage difference ΔV and the feeding speed difference ΔWs are stepped, but the relation between the voltage difference ΔV and the feeding speed difference ΔWs may be linear, for example. Although setting the voltage difference threshold value ΔVth is preferable for stable feed speed control, control without using the voltage difference threshold value ΔVth may be performed.

  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 22 Interface circuit 3 Welding power supply 31 Output control circuit (current control means)
32 Current detection circuit 33 Feeding speed setting circuit (feeding speed setting means)
34 Feed control circuit 35 Interface circuit 36 Voltage detection circuit D Distance W Welding base material (base material)
St Welding start signal On Output start signal Ws Feeding speed setting signal ΔWs Feeding speed difference Mc Operation control signal Fc Feeding control signal VR Robot movement speed Iw, Iw1, Iw2 Welding current iw1 Current value (first value)
Vf Feeding speed Vw Welding voltage Vst Reference welding voltage ΔV Voltage difference ΔVth Voltage difference threshold 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 is1 current value

Claims (12)

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,
In the second step, when the welding voltage between the consumable electrode and the base material is larger than a predetermined reference welding voltage, the feeding speed of the consumable electrode is increased, and the welding voltage is An arc welding method, wherein the feeding speed is reduced when the welding voltage is smaller than the welding voltage.   The arc welding method according to claim 1, wherein the feeding speed is not changed when a voltage difference between the welding voltage and the reference welding voltage is smaller than a predetermined voltage difference threshold value.   The arc welding method according to claim 2, wherein the feeding speed is set in a step shape with respect to the voltage difference.   The arc welding method according to any one of claims 1 to 3, wherein the welding current in the second step is a direct current.   The arc welding method according to claim 4, wherein constant current control is performed on the welding current in the second step.   The arc welding method according to claim 1, wherein the welding current in the first step is an alternating pulse current. 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 a second period in which the average value of the absolute value of the welding current is set to a second value smaller than the first value Current control means for repeatedly generating
Welding voltage detection means for detecting a welding voltage between the consumable electrode and the base material;
In the second period, when the welding voltage is larger than a predetermined reference welding voltage, the feeding speed of the consumable electrode is increased, and when the welding voltage is smaller than the reference welding voltage, the feeding is performed. A feed speed setting means for decelerating the speed;
An arc welding system comprising:   The arc according to claim 7, wherein the feeding speed setting means does not change the feeding speed when a voltage difference between the welding voltage and the reference welding voltage is smaller than a predetermined voltage difference threshold value. Welding system.   The arc welding system according to claim 8, wherein the feeding speed setting means sets the feeding speed in a stepped manner with respect to the voltage difference.   The arc welding system according to any one of claims 7 to 9, wherein the welding current in the second period is a direct current.   The arc welding system according to claim 10, wherein the current control means performs constant current control on the welding current in the second period.   The arc welding system according to any one of claims 7 to 11, wherein the welding current in the first period is an AC pulse current.