Arc start control method, welding power source, welding system, and program

Abstract

In gas shielded arc welding, the goal is to enable stable arc starting regardless of the welding method. [Solution] In an arc start control method for gas shielded metal arc welding using welding wire or filler wire, the method includes at least a retract control period in which retract control is performed from the start of welding until the transition to a steady welding period; a start base period in which, after the retract control, the feed speed is alternately switched between a forward feed period and a reverse feed period, and the feed control method is changed to one cycle in which the forward feed period and the reverse feed period are repeated, and the wire is moved to a predetermined reference value related to the tip position of the welding wire or filler wire; and a start initial condition period in which, after the start base period, predetermined welding conditions are maintained for a predetermined period in the feed control method.

Description

Technical Field

[0001] The present invention relates to an arc start control method, a welding power source, a welding system, and a program for performing stable arc start regardless of the welding method.

Background Art

[0002] Gas shielded arc welding is performed by various welding methods according to the application, such as a short circuit welding method, a pulse welding method, and a feed control welding method. However, regardless of the method, from the start of welding to the period when stable welding is achieved (hereinafter, also referred to as the "steady welding period" or "main welding period"), there is a transient welding period during which short circuits occur when the arc is generated, arc instability due to the molten pool not being formed, and instability of droplet transfer due to welding condition fluctuations until the set value is reached. Therefore, conventionally, by controlling this transient welding period (hereinafter, also referred to as the "arc start period"), the short circuit stability at the time of arc generation, improvement of arc instability and droplet transfer instability, reduction of spatter, and ensuring of a good bead shape are achieved.

[0003] Patent Document 1 discloses the control of the arc start period in the case of the short circuit welding method. After instructing the start of welding, the wire feed speed is set to a reverse feed during the short circuit period from the occurrence of the short circuit to the occurrence of the arc, and welding is performed with the wire feed speed set to a forward feed during the arc period from the occurrence of the arc to the occurrence of the next short circuit. Then, by switching the wire feed speed to a constant speed and performing welding, the amount of spatter generated from the occurrence of the arc until the arc becomes stable can be reduced.

[0004] Patent Document 2 discloses control of the arc start period in the case of pulse welding. When a predetermined time (t1) has elapsed from the short-circuit welding control during the arc start period, the system switches to pulse welding, which outputs a pulse waveform with a gentler rising and / or falling slope than the pulse waveform of steady-state welding (hereinafter also referred to as "main welding"). After a sufficient molten pool has formed, the system controls the output to display the pulse waveform of steady-state welding, thereby reducing the amount of spatter generated from the time the arc is generated until the arc stabilizes.

[0005] Patent Document 3 discloses control of the arc start period in a feed control welding method that alternately switches between a forward feed period and a reverse feed period to generate a short-circuit period and an arc period for welding. When starting welding, during the transient welding period until it converges to the steady-state welding period, the absolute values ​​of the reverse feed peak and the absolute values ​​of the forward feed peak of the feed rate are increased over time, thereby stabilizing the welding state when switching from the transient welding period to the steady-state welding period. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2013-169555 [Patent Document 2] International Publication No. 2012 / 032703 [Patent Document 3] Japanese Patent Publication No. 2021-74732 [Patent Document 4] International Publication No. 2015 / 163101 [Patent Document 5] Japanese Patent Publication No. 2020-49506 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] As mentioned above, while arc start time is controlled in all welding methods, including short-circuit welding, pulse welding, and feed control welding, the difficulty of controlling the arc start time is highest in feed control welding. Feed control welding involves control conditions originating from feed control, such as wire frequency and wire amplitude, and requires the control of a wide variety of conditions until the steady-state welding period is reached, making it significantly more difficult to control compared to other methods. As a result, droplet transfer and arc instability are more likely to occur, potentially leading to spatter generation and adverse effects on the bead shape.

[0008] Furthermore, there are different types of feed control welding methods. One type, as exemplified by Patent Document 4, is based on a short-circuit transition pattern that alternately switches the welding wire feed speed between forward and reverse feeding periods to generate short-circuit periods and arc periods (hereinafter also referred to as the "short-circuit feed control method"). Another type, as exemplified by Patent Document 5, is based on a globule transition pattern that alternately switches the welding wire feed speed between forward and reverse feeding periods to suppress the occurrence of short-circuit periods (hereinafter also referred to as the "short-circuit suppression feed control method").

[0009] The short-circuit suppression type feed control method, compared to the short-circuit type feed control method, results in larger droplet sizes at the wire tip. Therefore, the conditions must be gradually changed to increase the droplet size until the steady-state welding period is reached. However, as the steady-state welding period approaches, droplet fluctuations increase, making droplet transfer instability and arc instability more likely. Consequently, spatter generation and bead shape defects are more likely to occur, especially around the transition to the steady-state welding period.

[0010] Here, Patent Document 3 describes a case where a feed control welding method in which controlling the arc start period is difficult is applied, but it is a "short-circuit type feed control method" and does not provide a solution for the "short-circuit suppression type feed control method" in which controlling the arc start period is even more difficult. Furthermore, Patent Documents 1 to 3 are methods for controlling the arc start period according to each welding method, and are not methods for controlling the arc start period that can be commonly applied to multiple welding methods, thus lacking versatility. At the very least, even if the technology of Patent Document 1 or 2 is adapted to a feed control welding method in which controlling the arc start period is difficult, it will not be possible to sufficiently suppress the welding instability that occurs from the arc start period to the steady-state welding period.

[0011] The present invention has been made in view of the above-mentioned problems, and its objective is to provide an arc start control method, a welding power source, a welding system, and a program that can perform stable arc starting in gas shielded arc welding, regardless of the welding method. [Means for solving the problem]

[0012] The present invention consists of the following configuration.

[0013] (1) A method for controlling the arc start in gas shielded metal arc welding using welding wire or filler wire, From the start of welding to the transition to the steady-state welding period, The retract control period during which retract control is performed, After the retract control, the feeding control method is changed to one in which the feeding speed is alternately switched between a forward feeding period and a reverse feeding period, and the forward feeding period and reverse feeding period are repeated as one cycle, and a start base period is set to move the tip position of the welding wire or filler wire to a predetermined reference value, After the aforementioned start base period, there is a start initial condition period in which the predetermined welding conditions are maintained for a predetermined period using the feed control method, An arc start control method characterized by having at least one of the following.

[0014] (2) A welding power source for controlling the arc start in gas shielded metal arc welding using welding wire or filler wire, From the start of welding to the transition to the steady-state welding period, The retract control period during which retract control is performed, After the retract control, the feeding control method is changed to one in which the feeding speed is alternately switched between a forward feeding period and a reverse feeding period, and the forward feeding period and reverse feeding period are repeated as one cycle, and a start base period is set to move the tip position of the welding wire or filler wire to a predetermined reference value, After the aforementioned start base period, there is a start initial condition period in which the predetermined welding conditions are maintained for a predetermined period using the feed control method, A welding power source characterized by having at least one of the following.

[0015] (3) A welding system for controlling the arc start in gas shielded metal arc welding using welding wire or filler wire, From the start of welding to the transition to the steady-state welding period, The retract control period during which retract control is performed, After the retract control, the feeding control method is changed to one in which the feeding speed is alternately switched between a forward feeding period and a reverse feeding period, and the forward feeding period and reverse feeding period are repeated as one cycle, and a start base period is set to move the tip position of the welding wire or filler wire to a predetermined reference value, After the aforementioned start base period, there is a start initial condition period in which the predetermined welding conditions are maintained for a predetermined period using the feed control method, A welding system characterized by having at least one of the following.

[0016] (4) A program for controlling the arc start in gas shielded metal arc welding using welding wire or filler wire, From the start of welding to the transition to the steady-state welding period, The retract control period during which retract control is performed, After the retract control, change to a feeding control method in which the feeding speed is alternately switched between a forward feeding period and a reverse feeding period, and the forward feeding period and the reverse feeding period are repeated as one cycle, and shift to a reference value related to the tip position of the welding wire or filler wire determined in advance, a start base period, and after the start base period, in a predetermined welding condition, a start initial condition period that is maintained up to a predetermined period by the feeding control method, and A program characterized by having at least.

Effect of the Invention

[0017] According to the present invention, in gas shielded arc welding, regardless of the welding method, particularly when the short-circuit suppression type feeding control method is applied as the welding method, welding instability occurring from the arc start period to the steady welding period can be prevented, and particularly, spatter can be suppressed and a good bead shape can be obtained.

Brief Description of the Drawings

[0018] [Figure 1] FIG. 1 is a schematic diagram showing a configuration example of a welding system according to the present embodiment. [Figure 2] FIG. 2 is a block diagram showing a schematic configuration related to the control of a welding power source, a welding control device, and a servo amplifier in the present embodiment. [Figure 3] FIG. 3 is a graph illustrating the relationship between the wire feeding speed, the wire tip position, and the current detection signal during the present welding or the start initial condition period in the present embodiment. [Figure 4] FIG. 4 is a timing chart corresponding to the present embodiment. [Figure 5] FIG. 5 is a diagram mainly illustrating the start base period in the timing chart corresponding to the present embodiment.

Modes for Carrying Out the Invention

[0019] Hereinafter, embodiments of the arc start control method, welding power source, welding system, and program according to the present invention will be described in detail with reference to the drawings.

[0020] This embodiment is an example of a case using a welding robot, and the arc start control method, power supply, arc start control system, and arc start control program according to the present invention are not limited to the configuration of this embodiment. For example, an automatic welding device using a trolley may be used instead of the welding robot body, or a portable small welding robot may be used. Furthermore, this embodiment is an example of the case of the short-circuit suppression type feed control method, which is the most difficult to control when starting the arc, that is, when welding is performed using the short-circuit suppression type feed control method during the steady-state welding period after arc start control. However, the present invention may also be applied to other methods such as the short-circuit type feed control method, pulsed MAG welding method, and carbon dioxide welding method.

[0021] Furthermore, this embodiment describes a gas-shielded metal arc welding (hereinafter also referred to as "GMAW") method that uses welding wire, which is a consumable electrode in gas-shielded arc welding. However, the welding system according to this disclosure is also applicable to additive manufacturing systems that utilize gas-shielded metal arc welding. In addition, the disclosure also applies to non-consumable electrodes such as TIG welding using filler wire.

[0022] Figure 1 is a schematic diagram showing an example configuration of a welding system 50 according to this embodiment. The welding system 50 includes a welding robot 110, a welding control device 120, a welding power supply 140, a controller 150, a servo amplifier 160, a servo motor 170, a push motor 180, and a wire buffer 190. The push motor 180 feeds the welding wire 100.

[0023] The welding power supply 140 is connected to the welding robot 110 via a positive power cable to supply power to the welding wire 100, which is a consumable electrode, and is connected to the workpiece (hereinafter also referred to as "base material") 200 via a negative power cable. This connection is for welding with reverse polarity. To weld with positive polarity, the welding power supply 140 should be connected with the opposite polarity.

[0024] Furthermore, the welding power supply 140 and the push motor 180 are connected by a signal line, allowing control of the welding wire feed speed. In the feed control of this embodiment, the push motor 180 operates only in the forward direction, while the servo motor 170, described later, can be switched between forward and reverse directions.

[0025] The welding robot 110 is equipped with a welding torch 111 as an end effector. The welding torch 111 has a current supply mechanism, i.e., a contact tip, for supplying current to the welding wire 100. The welding wire 100 generates an arc from its tip when current is supplied from the contact tip, and uses the heat from this arc to weld the workpiece 200, which is the target of welding.

[0026] The welding torch 111 is equipped with a shielding gas nozzle, which is a mechanism for ejecting shielding gas. The shielding gas is not particularly limited, but from the viewpoint of versatility, it is preferable that it contains at least one gas with a high potential gradient, such as carbon dioxide, nitrogen, hydrogen, or oxygen. In the case of a mixed gas with argon gas (hereinafter also referred to as "Ar gas"), a system in which at least 10% by volume of carbon dioxide is mixed is more preferable, and a system in which 90% by volume of carbon dioxide is mixed is even more preferable. Carbon dioxide alone may also be used. The shielding gas is supplied from a shielding gas supply device (not shown).

[0027] The servo motor 170 is located near the welding torch 111. A servo amplifier 160 connected to the servo motor 170 controls the servo motor 170. In this embodiment, the welding torch 111 is configured to be independent of the servo motor 170, but the torch may also be configured to have the servo motor 170 integrated into the welding torch 111. The servo motor 170 controls the feeding direction by switching between forward and reverse rotation based on forward and reverse feeding commands. The servo amplifier 160 enables high-speed calculation processing and has a forward and reverse feeding command generation unit 161, as described later.

[0028] A wire buffer 190 is positioned between the push motor 180 and the servo motor 170. The push motor 180 feeds the wire only in the forward direction, while the servo motor 170 feeds the wire in both the forward and reverse directions. As a result, the feeding directions of the push motor 180 and the servo motor 170 may differ. This can lead to situations where the wire is subjected to a large load within the feeding path. To ensure proper feeding control even under such feeding conditions, the wire buffer 190 is provided to suppress wire buckling and other issues.

[0029] The welding wire 100 used in this embodiment is not particularly limited. For example, either a solid wire without flux or a flux-cored wire containing flux may be used. The material of the welding wire 100 is also not limited. For example, the material may be mild steel, stainless steel, aluminum, or titanium, and the wire surface may be plated with Cu or the like. The diameter of the welding wire 100 is also not particularly limited. In this embodiment, it is preferable to set the upper limit of the diameter to 1.6 mm and the lower limit to 0.8 mm.

[0030] Furthermore, in this embodiment, the specific configuration of the workpiece 200 is not particularly limited, nor are the welding conditions such as joint shape, welding position, and groove shape particularly limited. The welding control device 120 mainly controls the operation of the welding robot 110. Therefore, the welding control device 120 may be referred to as a robot controller. The welding control device 120 holds teaching data that predefines the operation pattern of the welding robot 110, welding start position, welding end position, welding conditions, weaving operation, etc., and controls the operation of the welding robot 110 by instructing the welding robot 110 with these. In addition, the welding control device 120 provides the welding power supply 140 with welding conditions such as welding current, welding voltage, and feed rate during the welding operation according to the teaching data.

[0031] As shown in Figure 1, the welding system 50 of this embodiment has a welding control device 120 that is independent of the welding power supply 140, but it is also possible to have a configuration in which the welding control device 120 is included in the welding power supply 140.

[0032] The controller 150 is connected to the welding control device 120 and performs tasks such as creating or displaying programs for operating the welding robot 110 and inputting teaching data. Information entered by the user into the controller 150 is provided to the welding control device 120. The controller 150 may also have a function for manually operating the welding robot 110. The connection between the controller 150 and the welding control device 120 can be wired or wireless, and there is no particular limitation on the type of connection.

[0033] The welding power supply 140, in response to a command from the welding control device 120, supplies power to the welding wire 100 and the workpiece 200, thereby generating an arc between the welding wire 100 and the workpiece 200. The welding power supply 140 also outputs a control signal for the push motor 180 in response to a command from the welding control device 120.

[0034] Next, the functional configuration of the welding system 50 according to this embodiment will be described in detail with reference to Figures 2 and 3. Figure 2 is a block diagram illustrating the schematic configuration related to the control of the welding power supply 140, welding control device 120, and servo amplifier 160 in this embodiment. Figure 3 is a graph illustrating the relationship between the wire feeding speed, the wire tip position, and the current detection signal during the actual welding or the initial start condition period described later in this embodiment.

[0035] The welding power supply 140 is connected to the welding control device 120 via digital communication, and the welding control device 120 is connected to the servo amplifier 160 via digital communication. In other words, the servo amplifier 160, welding control device 120, and welding power supply 140 are connected in a linear configuration in that order via digital communication. This can be interpreted as the servo amplifier 160 and the welding power supply 140 being indirectly connected via digital communication. Alternatively, the servo amplifier 160, welding power supply 140, and welding control device 120 may be connected in a linear configuration in that order. This can be interpreted as the servo amplifier 160 and the welding power supply 140 being directly connected via digital communication.

[0036] In this embodiment, communication between the welding power supply 140 and the welding control device 120 is performed using CAN (Controller Area Network), which is one of the industrial field networks, and communication between the welding control device 120 and the servo amplifier 160 is performed using EtherCAT (Ethernet for Control Automation Technology) (registered trademark), which is one of the industrial field networks, but the invention is not limited to these.

[0037] (Functional configuration of welding power supply) The control system unit 141 of the welding power supply 140 is executed, for example, through the execution of a program by a welding control device 120 or a computer (not shown). The control system unit 141 of the welding power supply 140 includes a current setting unit 36. In this embodiment, the current setting unit 36 ​​has the function of setting various current values ​​that define the welding current flowing through the welding wire 100. The current setting unit 36 ​​has the function of setting the start time and end time for each period of current control. The current setting unit 36 ​​includes a target current setting unit 36A, a wire tip position conversion unit 36B, and a voltage setting unit 36C. The target current setting unit 36A has the function of setting the start time and end time for each of the peak period Dap, fall period Ddwn, base period Db, and rise period Dup related to current control. The wire tip position conversion unit 36B has the function of obtaining information on the tip position of the welding wire 100.

[0038] Various conditions can be determined based on, for example, settings entered in advance by the operator, or a pre-prepared waveform control table or welding condition database. The settings, tables, and databases may be stored in any of the components of the welding system 50. For example, the settings, tables, and databases may be stored in the welding control device 120 or the welding power supply 140. These settings, tables, and databases are stored in the waveform table linear calculation unit 37, which selects the settings to be used for each status of arc start, welding in progress, and anti-stick in the welding sequence unit 43. "Welding in progress" refers to welding within the main welding period.

[0039] The various conditions for the peak period Dap, falling period Ddwn, base period Db, and rising period Dup related to the current non-suppression period TIP (the sum of the Dup and Dap periods in this embodiment) and the current suppression period TIB (the sum of the Ddwn and Db periods in this embodiment) can be determined by the waveform control table linear calculation unit 37 based on a pre-prepared waveform control table. In this embodiment, the various conditions referred to are the settings of conditions such as current value, time, or phase.

[0040] The welding current exhibits a pulse waveform that alternately repeats the welding current during the current-unsuppressed period TIP and the current-suppressed period TIB, based on the phase related to the wire tip position (hereinafter referred to as "wire position phase" or "position phase"). In this embodiment, the timing of the peak period Dap, the fall period Ddwn, the base period Db, and the rise period Dup are controlled based on the wire position phase from 0 to 360° (0 to 2π), where 0° is when the wire tip position is closest to the tip side and 180° is when it is closest to the base material side.

[0041] Based on the setting value of the average feed rate Favg in the welding condition information stored by the control system unit 141, the waveform control table linear calculation unit 37 calculates the set current value Iap for the peak period Dap in the current non-suppression period TIP (hereinafter also referred to as "peak current Iap") and the set current value Ib for the base period Db in the current suppression period TIB (hereinafter also referred to as "base current Ib"), and these are set in the current setting unit 36.

[0042] In this embodiment, the welding current is basically controlled in two periods: a peak current period and a base current period. Therefore, the start time of the current suppression period TIB may be expressed as the base current start time, which is the time when the current transitions to the base current Ib, i.e., the start time of the falling period Ddwn. Also, the end time of the current suppression period TIB may be expressed as the end time of the base current Ib, i.e., the base current end time. The duration (hours) of the falling period Ddwn and the base period Db related to the start time of the current suppression period TIB and the end time of the current suppression period TIB are calculated in the waveform control table linear calculation unit 37. The start time of the current unsuppressed period TIP, i.e., the start time of the rise period Dup, may be expressed as the peak current start time, and the end time of the current unsuppressed period TIP may be expressed as the peak current end time. As shown in Figure 3, the timing of the peak current end time is preferably determined in the set period d1 when the wire position phase starts at 0°, and the timing of the peak current start time is preferably determined in the set period d2 when the peak current end time starts. This setting period is best set using phase. For example, if d1 is set to 190° and d2 to 120°, the peak current will end when the wire position phase is 190° (d1) and the peak current will start when the wire position phase is 310° (d1+d2).

[0043] The various start and end times mentioned above are explained in terms of time. However, the wire position phase value may be used as the basis for processing, and the value may be converted from the wire position phase to time or period (cyc). In other words, since the values ​​of wire position phase, time, and period (cyc) are mutually convertible, control may be performed based on any of these values.

[0044] Furthermore, the wire tip position conversion unit 36B determines the wire tip position based on the phase synchronization signal and phase delay correction signal from the servo amplifier 160. In this embodiment, the wire tip position may be expressed as a wire position phase using an angle (0 to 2π), as described above.

[0045] The phase delay correction signal is output from the phase delay correction unit 38. The phase delay correction unit 38 has a database (not shown in the figure). This database stores data that has been pre-calculated for each welding condition, showing the difference between periodic setting information and the actual forward and reverse feeding operation signals of the servo motor 170. For example, if the welding condition is the wire forward and reverse frequency, the phase delay correction amount is determined based on the above database according to the value of the wire forward and reverse frequency used, and is output from the phase delay correction unit 38 as a phase delay correction signal.

[0046] The main power circuit of the welding power supply 140 consists of a three-phase AC power supply (hereinafter also referred to as "AC power supply") 1, a primary rectifier 2, a smoothing capacitor 3, a switching element 4, a transformer 5, a secondary rectifier 6, and a reactor 7.

[0047] The AC power input from the AC power supply 1 is full-wave rectified by the primary rectifier 2 and then smoothed by the smoothing capacitor 3 to be converted into DC power. Next, the DC power is converted into high-frequency AC power by inverter control by the switching element 4, and then converted into secondary power via the transformer 5. The AC output of the transformer 5 is full-wave rectified by the secondary rectifier 6 and then smoothed by the reactor 7. The output current of the reactor 7 is supplied to the contact tip as the output from the main power supply circuit and energizes the welding wire 100, which is a consumable electrode.

[0048] The welding wire 100 is fed by a push motor 180 and a servo motor 170, generating an arc between it and the base material 200. The forward feeding period, during which the tip of the welding wire 100 is moved toward the base material 200, is denoted as the forward feeding period TP. The reverse feeding period, during which the tip of the welding wire 100 is moved in the opposite direction to the position of the base material 200, is denoted as the reverse feeding period TN. In this embodiment, the feeding motor periodically feeds the welding wire 100, with the forward feeding period TP and the reverse feeding period TN combined forming one cycle. The tip of the welding wire usually refers to the tip of the wire when the presence of molten droplets hanging from the wire tip is ignored. That is, the wire melted by the arc is considered to have immediately moved toward the base material 200.

[0049] The feeding of the welding wire 100 by the push motor 180 is controlled by a control signal based on the push feeder control unit 39. The average feeding speed is approximately the same as the melting speed. In this embodiment, the feeding of the welding wire 100 by the push motor 180 is also controlled by the welding power supply 140.

[0050] Furthermore, the push feeder control unit 39 performs control according to the state of the wire buffer 190. In this embodiment, the wire buffer 190 is provided with a wire slack portion (a gap to which the wire can escape if it becomes loose due to the effects of feeding between the motors) so that a large load is not placed on the wire in the feeding path between the push motor 180 and the servo motor 170. The amount of wire buffer is detected as a rotation angle by an absolute encoder, which is a sensor built into the wire buffer 190. The detected value is converted into an analog signal by the serial-to-analog conversion unit 191, and the electrical angle is calculated by the electrical angle calculation unit. The calculated electrical angle is input to the A / D input unit 40 of the welding power supply.

[0051] A difference signal, obtained by taking the difference between the electrical angle from the A / D input unit 40 and a preset reference value of the electrical angle in the electrical angle adjustment unit 41, is input to the push feeder control unit 39. Based on this difference signal, the push feeder control unit 39 controls the push motor 180 to achieve an appropriate wire buffer amount, thereby performing interference control to prevent excessive load on the feeding system. In this embodiment, interference control is performed as described above, but it is not limited to this. Also, in this embodiment, an absolute encoder built into the wire buffer 190 is used, but it is not limited to this. For example, a rotation angle sensor may be used, in which case the serial-to-analog conversion unit 191 does not need to be provided.

[0052] The current setting unit 36 ​​receives a voltage setting signal Vap from the voltage setting unit 36C, which is the target value of the voltage applied between the welding tip and the base material 200.

[0053] On the other hand, the voltage detection signal Vo is a measured value. In this embodiment, the voltage detection signal Vo passes through a low-pass filter LPF, goes through a disconnection detection unit 33 (described later), and is input to the current setting unit 36 ​​together with the disconnection detection signal DTR (described later). Alternatively, a voltage comparison unit may be provided to amplify the difference between the voltage setting signal Vap and the voltage detection signal Vo, and output it to the current setting unit 36 ​​as a voltage error amplification signal.

[0054] The current setting unit 36 ​​controls the welding current during the peak period Dap so that the arc length (hereinafter also referred to as "arc length") remains constant. Based on the voltage setting signal Vap and the voltage detection signal Vo, the current setting unit 36 ​​determines and sets at least the peak period, rise period, base period, and rise period. The values ​​of the peak current Ip and base current Ib may be reset. A current setting signal CCset corresponding to the set period or value is output to the current error amplification unit (PWM) 34.

[0055] The current error amplification unit 34 amplifies the difference between the current setting signal CCset given as the target value and the current detection signal Io detected by the current detection unit 31, and outputs it as a current error amplification signal Ed to the inverter drive unit (INV drive unit) 30. The inverter drive unit 30 corrects the drive signal Ec of the switching element 4 using the current error amplification signal Ed.

[0056] The current setting unit 36 ​​also receives a detachment detection signal DTR, which is a signal that detects the detachment of molten droplets from the tip of the welding wire 100. The detachment detection signal DTR is output from the detachment detection unit 33. The detachment detection unit 33 monitors the change in the voltage detection signal Vo output by the voltage detection unit 32 and detects the detachment of molten droplets from the welding wire 100 from the change. Note that the detachment detection unit 33 is just one example of a detection means.

[0057] The detachment detection unit 33 detects droplet detachment by comparing, for example, the differential or second differential of the voltage detection signal Vo passed through the LPF with a predetermined threshold value for detection. The detection threshold value is pre-stored in a memory unit (not shown in the figure). The detachment detection unit 33 may also generate a detachment detection signal DTR based on the change in resistance value calculated from the measured voltage detection signal Vo and current detection signal Io.

[0058] The waveform control table linear calculation unit 37 is given the average feed rate Favg of the weld wire 100 being fed. The average feed rate Favg is stored in advance in the feed setting data unit 35. In this embodiment, the feed setting data unit 35 is located within the welding power supply 140, but various information related to the feed setting may be stored within the welding control device 120, and this information may be output from the welding control device 120 to the welding power supply 140.

[0059] The waveform control table linear calculation unit 37 determines values ​​such as the peak current Ip, base current Ib, the time at which the base current Ib starts, and the time at which the base current Ib ends, based on the given average feed rate Favg, and outputs them to the current setting unit 36. As mentioned above, the values ​​of wire position phase, time, and period cyc are mutually convertible, so the setting value of the base start phase may be converted to a value of time or period cyc, and the converted value may be output to the current setting unit 36.

[0060] In this embodiment, the average feed rate Favg is input to the waveform control table linear calculation unit 37. However, a value related to the average feed rate Favg may be input to the waveform control table linear calculation unit 37 as a set value, and the waveform control table linear calculation unit 37 may replace the average feed rate Favg with that set value. For example, if a storage unit (not shown) stores a database of the average feed rate Favg and the average current value that enables optimal welding for that average feed rate Favg, the average current value may be used as the set value, and the set value may be replaced with the average feed rate Favg.

[0061] The feed setting data unit 35 may store setting values ​​such as the average feed speed Favg, wire amplitude Wf, wire forward / reverse frequency Hf, and wire forward / reverse period Tf. The wire amplitude Wf, wire forward / reverse frequency Hf, and wire forward / reverse period Tf may be determined based on the input average feed speed Favg. The feed setting data unit 35 may also store other setting values ​​as feed setting data. In this embodiment, the value of wire amplitude Wf ​​refers to the wave height Wh shown in Figure 3. That is, the set value of wire amplitude Wf ​​is equal to the wave height Wh.

[0062] In this embodiment, the period during which the feeding speed is greater than the average feeding speed Favg is defined as the positive feeding period, and the period during which the feeding speed is less than the average feeding speed Favg is defined as the negative feeding period, resulting in feeding in which positive and negative feeding periods alternate (hereinafter abbreviated as "amplitude feeding"). Note that the period during which the feeding speed is less than the average feeding speed Favg refers to a feeding speed less than the average feeding speed Favg, and includes negative feeding speeds, i.e., speeds at which the wire tip moves in the opposite direction to a certain position on the base material 200. The wire amplitude Wf ​​gives the range of change with respect to the average feeding speed Favg, and the wire forward / reverse period Tf gives the time of change in wire amplitude, which is the repeating unit. The wire forward / reverse frequency Hf is the reciprocal of the wire forward / reverse period Tf.

[0063] The average feed speed Favg, wire amplitude Wf, wire forward / reverse frequency Hf, and wire forward / reverse period Tf stored in the feed setting data unit 35 are input from the digital communication unit 42 to the digital communication unit 122 of the welding control device 120. In this embodiment, this feed setting data is communicated via CAN communication.

[0064] The welding sequence unit 43 processes each task in the following order based on teaching data: idle, gas flow, arc start, welding, and anti-stick. In Figure 2, for convenience, the welding condition information held by the welding control device 120 is enclosed in a dashed line within the welding power supply 140.

[0065] (Functional configuration of welding control device) As described above, the digital communication unit 122 of the welding control device 120 receives feed setting data such as the average feed speed Favg, wire amplitude Wf, wire forward / reverse frequency Hf, and wire forward / reverse period Tf from the feed setting data unit 35 of the welding power supply 140 via CAN communication. The welding control device 120 has a digital communication unit 123 for outputting this feed setting data to the digital communication unit 162 of the servo amplifier 160. In this embodiment, the digital communication unit 123 of the welding control device 120 and the digital communication unit 162 of the servo amplifier 160 are connected by EtherCAT® communication.

[0066] (Servo amplifier functional configuration) The digital communication unit 162 of the servo amplifier 160 receives feed setting data such as the average feed speed Favg, wire amplitude Wf, wire forward / reverse frequency Hf, and wire forward / reverse period Tf via EtherCAT® communication. The forward / reverse feed command generation unit 161 of the servo amplifier 160 generates a feed command for forward or reverse feed based on the setting information, i.e., the feed setting data, input via digital communication. The forward / reverse feed command generation unit 161 calculates the amplitude feed speed Ff from the wire amplitude Wf ​​and wire forward / reverse period Tf, and outputs a feed speed command signal Fw to the servo motor 170 based on the amplitude feed speed Ff and the average feed speed Favg.

[0067] In this embodiment, the feed rate command signal Fw is expressed by the following equation. Fw=Ff+Favg...Formula (A)

[0068] Furthermore, the forward / reverse feeding command generation unit 161 may detect at which wire position phase of amplitude feeding detachment occurred based on the detachment detection signal DTR provided by the detachment detection unit 33. However, the feeding speed command signal Fw represented by equation (A) is limited to cases where detachment of a molten droplet from the tip of the welding wire 100 is detected within the assumed period. If detachment of a molten droplet is not detected within the assumed period, the forward / reverse feeding command generation unit 161 may switch the feeding speed command signal Fw to feeding control at a constant speed. For example, the forward / reverse feeding command generation unit 161 switches the feeding speed command signal Fw to feeding at the average feeding speed Favg. The switch from feeding at the average feeding speed Favg to the feeding control represented by equation (A) is determined according to the timing at which detachment of a molten droplet is detected.

[0069] The servo amplifier 160 controls the inverter of the servo motor 170 based on the feed speed command signal Fw. The synchronous signal generation unit 163 of the servo amplifier 160 outputs a phase synchronous signal to the welding power supply 140. This phase synchronous signal is generated based on the feed speed command signal Fw.

[0070] Furthermore, the welding power supply 140 and the synchronization signal generation unit 163 of the servo amplifier 160 may be connected by at least analog input / output. In this case, the welding power supply 140 receives the synchronization signal from the servo amplifier 160 via analog input / output. By transmitting feed setting data such as the average feed speed Fabag, wire amplitude Wf, wire forward / reverse frequency Hf, and wire forward / reverse period Tf via digital communication, while transmitting the synchronization signal via analog communication, digital and analog communication can be efficiently used depending on the application.

[0071] Here, the phase related to the wire feed speed command signal Fw (hereinafter also referred to as the "feed speed phase") is set as follows: 0° for the start of forward feeding, 180° (π) for the end of forward feeding and the start of reverse feeding, and 360° (2π) for the end of reverse feeding. In this embodiment, if the value of the wire feed speed Fw is less than the average feed speed Favg, it means reverse feeding; if the value is equal to or greater than the average feed speed Favg, it means forward feeding. In this embodiment, the phase synchronization signal consists of a synchronization signal for the feed speed phase and a synchronization signal for the wire position phase. The synchronization signal for the feed speed phase is a synchronization signal that turns ON during the forward feeding period (positions 0 to π) and OFF during the reverse feeding period (positions π to 2π). On the other hand, the wire position phase synchronization signal is set to ON during the period when the wire is closer to the base material 200 side than the center position of the wave height when the wire is being fed forward and backward (position 0.5π to 1.5π), and to OFF during the period when the wire is closer to the tip side than the center position of the wire amplitude (position 1.5π to 0.5π). Based on this phase synchronization signal and the aforementioned phase delay correction amount, the tip position of the welding wire 100, i.e., the wire position phase, is determined by the wire tip position conversion unit (deg) 36B in the welding power supply 140.

[0072] <Arc start control> Next, the arc start control according to the present invention will be described. Figure 4 is a timing chart corresponding to this embodiment. The timing chart in Figure 4 shows the timing for the wire feed speed set value Fset, the retract signal, the current setting signal CCset, and the voltage setting signal Vap. The wire feed speed set value Fset corresponds to the average feed speed Favg. The retract signal is labeled "Retract EN" in the figure. The timing chart in Figure 4 is an example where the shielding gas composition is carbon dioxide, but the process is similar even in the case of a mixed gas containing Ar gas, for example.

[0073] The arc start control of the present invention includes, from the welding start signal St, which corresponds to the start of welding (also called the arc-on signal) in the teaching data program, at least a retract control period, a start base period which is a preparation period for performing forward and reverse feed control after retract control, and a start initial condition period after the start base period in which forward and reverse feed control is performed under conditions different from those of the actual welding. Each of these periods will be described in detail below.

[0074] As shown in Figure 4, in this embodiment, the retract control period consists of a slowdown period and a retract CC period. T1 is the time when the slowdown period begins after the welding start signal St is turned ON, T2 is the time when the retract CC period begins as soon as the slowdown period ends, T3 is the time when the retract CC period ends and the start base period begins, T4 is the time when the start base period ends and the start initial condition period begins, and T5 is the time when the start initial condition period ends and steady-state welding begins. In other words, the period from T1 to T2 is the slowdown period, the period from T2 to T3 is the retract CC period, the period from T3 to T4 is the start base period, the period from T4 to T5 is the start initial condition period, and from T5 until the welding start signal St is turned OFF is the steady-state welding period. Details of each period will be explained below.

[0075] (T1-T2 period: Slowdown period) The slowdown section is the period from the start of welding until the arc is generated. When the welding start signal St is input and the welding sequence unit 43 enters the arc start state at the welding position, the welding wire is fed toward the base metal. After the welding wire and the base metal come into contact, a short circuit occurs, causing a high current to flow and generating the initial arc. If proper control is not performed at this stage, there is a risk of wire breakage or failure of the initial arc. In this embodiment, after the welding start signal St is turned ON at T1, the welding wire is fed toward the base metal at a preset feeding speed at the welding start position. If this feeding speed is too high, the welding wire will push strongly against the base metal, causing wire buckling and torch vibration. Therefore, the feeding speed set in the slowdown section should be as low as possible, and it is even better to set it within the range of 0.4 to 2.5 m / min. It is also advisable to change the feeding speed according to the type of steel and wire diameter of the wire being used. Furthermore, at the end of the slowdown section T2, after the welding wire and the base metal come into contact, the retract EN signal turns ON, and the retract CC section, which will be described next, begins. Contact between the welding wire and the base metal can be determined, for example, by current flow detection (also called "short circuit detection"). If current flow detection is not possible, the slowdown section can be forcibly ended and the retract EN signal turned ON after a predetermined time has elapsed.

[0076] (T2-T3 period: Retract CC section) The retract CC section begins at T2, immediately after the welding wire and base metal come into contact. When the retract EN signal turns ON and the retract CC section begins, reverse feeding is performed at a predetermined feeding speed. This feeding speed for reverse feeding is defined as the retract speed. This process allows for smooth arc generation and maintenance. The set values ​​and times for each parameter, such as the retract speed and welding current, are not particularly restricted and can be pre-set in the waveform control parameter table. Here, the set value for the retract speed may be changed according to the average feeding speed (feeding speed setting value) of the actual welding. The retract CC section can be set according to the communication configuration of the control equipment. This is because, depending on the communication configuration, a communication delay will inevitably occur when transmitting the parameters necessary for control in the next period, so it is preferable to set the time taking communication delay into consideration. In this embodiment, parameters for starting feed control in the next period are transmitted, but since a delay of approximately 20 to 40 msec occurs in digital communication, the length of the retract CC section is set to be longer than the delay time. Furthermore, the welding current setting during the retract CC section may be changed according to the elapsed time between the end of the previous weld and the start of the next weld, in the case of multi-layer welding. This is because the workpiece temperature rises due to the previous weld, and this temperature affects the formation of the molten pool in the retract CC section, for example, the size of the molten pool. In other words, if the elapsed time is short, the workpiece temperature is high, making it easier for a molten pool to form and for it to spread widely. Therefore, by adjusting the welding current to be lower than the original setting, variations in the size of the molten pool can be suppressed and a stable arc can be maintained. Note that "end of welding" here refers to the end of arc end treatment.

[0077] (T3-T4 period: Start-up period) Refer to Figures 4 and 5 together. Figure 5 is a diagram that mainly illustrates the start base period in the timing chart corresponding to this embodiment. In Figure 5, the arrows near the workpiece 200 indicate the movement of the wire tip position. Also, the dotted line in Figure 5 indicates the feed speed command signal Fw.

[0078] The start-base period begins at T3, when the retract CC section ends and the retract EN signal turns OFF. The start-base period is a preparation period before entering the start-initial conditions period, which will be described later. Since the start-initial conditions period is used for wire feed control, the start-base period can also be considered a preparation period for stable wire feed control during the start-initial conditions period. When the start-base period begins, the wire tip position at time T3 is advanced to a predetermined reference position. In this embodiment, the wire tip position is defined as the wire position phase, as described above, and the position where the wire position phase is 0° corresponds to the reference position in this embodiment. Note that during the start-base period, the reference value related to the tip position of the welding wire or filler wire may be at least one of the wire position phase and the feed rate phase.

[0079] The wire position at time T3 varies depending on the duration of the retract CC section, and since forward and reverse feeding is performed from that position to the reference position, the length of the T3-T4 period is variable. In other words, the point at which the wire tip reaches the reference position is T4, which marks the end of the start base period. Furthermore, it is preferable to change the setting value of at least one welding condition, excluding the feed speed setting value, during this period. Examples of welding conditions include welding current, arc voltage, and welding speed, but in this embodiment, it is preferable to change the setting value of the welding current, and it is more preferable to maintain the welding current setting value at a low current of 250A or less, and even more preferable, the setting value of the welding current should be the value of the lowest current setting value within the base period. By performing such control, arc instability such as arc breakup caused when switching to feed control can be suppressed during the start initial condition period described later, and it is possible to prevent an increase in spatter and poor bead appearance at the start position.

[0080] (T4-T5 period: Initial conditions period at the start) When the wire tip reaches the reference position and the start-base period ends, the start-initial condition period begins, and forward / reverse wire feeding control is performed. During the start-initial condition period, predetermined welding conditions are maintained for a period predetermined by the wire feeding control method. These conditions differ from those during steady-state welding. In this embodiment, a lower wire feeding speed setting value than that used during steady-state welding is provided, and the setting values ​​for various conditions are determined from the waveform control table linear calculation unit based on the wire feeding speed setting value during the start-initial condition period. At this time, it is preferable to control the welding current by switching between peak current and base current depending on the wire position. In other words, during the start-initial condition period, the welding current is set to a pulse waveform that repeats between peak and base periods. The start timing of the peak period and the base period is determined according to the tip position of the welding wire or filler wire. The pulse waveform conditions, i.e., waveform parameters, may be determined based on a predetermined waveform table and the average wire feeding speed setting value.

[0081] Furthermore, as shown in Figure 4, it is preferable to control the welding current by dividing the base period into a first base period Db1 and a second base period Db2. By performing such control, the arc stability during the initial start condition period is further improved, and the generation of spatter is suppressed. In addition, it is preferable to set the arc voltage to a value greater than the appropriate value. Specifically, it is preferable to set the ratio of the average feed rate to the arc voltage setting value (Vset / Fave) to within the range of 2.0 to 6.0. Setting the arc voltage in this way increases the arc length, which further improves the arc stability during the initial start condition period and suppresses the generation of spatter.

[0082] Furthermore, the start-up initial condition period can be terminated when a predetermined elapsed time, the number of wire forward / reverse frequency Hf cycles, or the number of welding current pulses exceeds a specified threshold, such as a specified time or number of cycles. The threshold may be predetermined, but it may also be changed according to the set welding conditions or welding information. Examples of set welding conditions include the feed rate setting, and examples of welding information include plate thickness or molten pool size.

[0083] (T5 period onwards: steady-state welding period) Once the initial start-up period ends, the welding conditions switch to those used during steady-state welding.

[0084] The present invention is not limited to the embodiments described above. It is also intended and within the scope of protection to be provided for the combination of each configuration of the embodiments, as well as for modifications and applications by those skilled in the art based on the description in the specification and well-known art.

[0085] As described above, the following matters are disclosed in this specification:

[0086] (1) An arc start control method in gas shielded metal arc welding using welding wire or filler wire, wherein from the start of welding to the transition to the steady-state welding period, The retract control period during which retract control is performed, After the retract control, the feeding control method is changed to one in which the feeding speed is alternately switched between a forward feeding period and a reverse feeding period, and the forward feeding period and reverse feeding period are repeated as one cycle, and a start base period is set to move the tip position of the welding wire or filler wire to a predetermined reference value, After the aforementioned start base period, there is a start initial condition period in which the predetermined welding conditions are maintained for a predetermined period using the feed control method, An arc start control method characterized by having at least one of the following.

[0087] (2) The arc start control method according to (1), characterized in that, during the start base period, the reference value relating to the tip position of the welding wire or filler wire is a value predetermined in at least one of the wire position phase and the feed rate phase.

[0088] (3) The arc start control method according to (1), characterized in that at least one welding condition other than the feed rate is changed during the start base period.

[0089] (4) The arc start control method according to (1), characterized in that, during the initial start condition period, the welding current is a pulse waveform that repeats a peak period and a base period, and the start timing of the peak period and the base period is determined according to the tip position of the welding wire or filler wire.

[0090] (5) The arc start control method according to (4), characterized in that, during the initial start condition period, the method switches from the initial start condition period to a steady-state welding period, with at least one of the following conditions as a threshold: elapsed time and the number of pulses of the welding current.

[0091] (6) The arc start control method according to (5), characterized in that the threshold is changed according to the set welding conditions or welding information.

[0092] (7) The arc start control method according to (1), characterized in that, during the initial start condition period, the set value of the arc voltage is set such that the ratio of the average feed speed to the set value of the arc voltage is 2.0 to 6.0.

[0093] (8) The retract control period includes at least the retract CC interval, The arc start control method according to (1), characterized in that the set value of the welding current in the retract CC section is changed according to the elapsed time from the end of the previous welding to the start of the next welding.

[0094] (9) A welding power source for controlling the arc start in gas shielded metal arc welding using welding wire or filler wire, wherein from the start of welding to the transition to the steady-state welding period, The retract control period during which retract control is performed, After the retract control, the feeding control method is changed to one in which the feeding speed is alternately switched between a forward feeding period and a reverse feeding period, and the forward feeding period and reverse feeding period are repeated as one cycle, and a start base period is set to move the tip position of the welding wire or filler wire to a predetermined reference value, After the aforementioned start base period, there is a start initial condition period in which the predetermined welding conditions are maintained for a predetermined period using the feed control method, A welding power source characterized by having at least one of the following.

[0095] (10) A welding system for controlling the arc start in gas shielded metal arc welding using welding wire or filler wire, wherein from the start of welding to the transition to the steady welding period, The retract control period during which retract control is performed, After the retract control, the feeding control method is changed to one in which the feeding speed is alternately switched between a forward feeding period and a reverse feeding period, and the forward feeding period and reverse feeding period are repeated as one cycle, and a start base period is set to move the tip position of the welding wire or filler wire to a predetermined reference value, After the aforementioned start base period, there is a start initial condition period in which the predetermined welding conditions are maintained for a predetermined period using the feed control method, A welding system characterized by having at least one of the following.

[0096] (11) A program for controlling the arc start in gas shielded metal arc welding using welding wire or filler wire, wherein the program takes place from the start of welding to the transition to the steady-state welding period. The retract control period during which retract control is performed, After the retract control, the feeding control method is changed to one in which the feeding speed is alternately switched between a forward feeding period and a reverse feeding period, and the forward feeding period and reverse feeding period are repeated as one cycle, and a start base period is set to move the tip position of the welding wire or filler wire to a predetermined reference value, After the aforementioned start base period, there is a start initial condition period in which the predetermined welding conditions are maintained for a predetermined period using the feed control method, A program characterized by having at least the following. [Explanation of Symbols]

[0097] 1 AC power supply 2 Primary rectifier 3. Smoothing Capacitor 4 Switching elements 5 transformers 6 Secondary rectifier 7 Reactor 30 Inverter drive unit (INV drive unit) 31 Current detection unit 32 Voltage detection unit 33 Detachment detection unit 34 Current Error Amplification Section (PWM) 35. Supply setting data section 36 Current setting section 36A target current setting section 36B Wire tip position conversion unit 36C Voltage setting section 37 Waveform Control Table Linear Calculation Unit 38 Phase delay correction unit 39 Push Feeder Control Unit 40 A / D Input Section 41 Electrical angle adjustment section 42 Digital Communications Department 43 Welding Sequence Section 50 Welding Systems 100 welding wires 110 Welding Robots 111 Welding Torch 120 Welding control device 122 Digital Communications Department 123 Digital Communications Department 140 Welding Power Supply 141 Control System Section 150 controllers 160 Servo Amplifier 161 Forward / reverse feed command generation unit 162 Digital Communications Department 163 Synchronization signal generation unit 170 Servo motors 180 Push Motor 190 Wire Buffer 191 Serial-to-analog conversion section 200 work

Claims

1. A method for controlling the arc start in gas shielded metal arc welding using welding wire or filler wire, From the start of welding to the transition to the steady-state welding period, The retract control period during which retract control is performed, After the retract control, the feeding speed is switched alternately between a forward feeding period and a reverse feeding period, and the feeding control method is changed to one cycle consisting of a forward feeding period and a reverse feeding period, and a start base period is set to move the tip position of the welding wire or filler wire to a predetermined reference value. After the aforementioned start base period, there is a start initial condition period in which the predetermined welding conditions are maintained for a predetermined period using the feed control method, An arc start control method characterized by having at least one of the following.

2. The arc start control method according to claim 1, characterized in that, during the start base period, the reference value relating to the tip position of the welding wire or filler wire is a value predetermined in at least one of the wire position phase and the feed rate phase.

3. The arc start control method according to claim 1, characterized in that at least one welding condition other than the feed rate is changed during the start base period.

4. The arc start control method according to claim 1, characterized in that, during the initial start condition period, the welding current is a pulse waveform repeating a peak period and a base period, and the start timing of the peak period and the base period is determined according to the tip position of the welding wire or filler wire.

5. The arc start control method according to claim 4, characterized in that, during the initial start condition period, the system switches from the initial start condition period to a steady-state welding period, with at least one of the following conditions—elapsed time and the number of pulses of the welding current—as a threshold.

6. The arc start control method according to claim 5, characterized in that the threshold is changed according to the set welding conditions or welding information.

7. The arc start control method according to claim 1, characterized in that, during the initial start condition period, the set value of the arc voltage is set such that the ratio of the average feed speed to the set value of the arc voltage is 2.0 to 6.

0.

8. The retract control period includes at least a retract CC interval, The arc start control method according to claim 1, characterized in that the set value of the welding current in the retract CC section is changed according to the elapsed time from the end of the previous welding to the start of the next welding.

9. A welding power source for controlling the arc start in gas shielded metal arc welding using welding wire or filler wire, From the start of welding to the transition to the steady-state welding period, The retract control period during which retract control is performed, After the retract control, the feeding speed is switched alternately between a forward feeding period and a reverse feeding period, and the feeding control method is changed to one cycle consisting of a forward feeding period and a reverse feeding period, and a start base period is set to move the tip position of the welding wire or filler wire to a predetermined reference value. After the aforementioned start base period, there is a start initial condition period in which the predetermined welding conditions are maintained for a predetermined period using the feed control method, A welding power source characterized by having at least one of the following.

10. A welding system for controlling arc start in gas shielded metal arc welding using welding wire or filler wire, From the start of welding to the transition to the steady-state welding period, The retract control period during which retract control is performed, After the retract control, the feeding speed is switched alternately between a forward feeding period and a reverse feeding period, and the feeding control method is changed to one cycle consisting of a forward feeding period and a reverse feeding period, and a start base period is set to move the tip position of the welding wire or filler wire to a predetermined reference value. After the aforementioned start base period, there is a start initial condition period in which the predetermined welding conditions are maintained for a predetermined period using the feed control method, A welding system characterized by having at least one of the following.

11. A program for controlling the arc start in gas shielded metal arc welding using welding wire or filler wire, From the start of welding to the transition to the steady-state welding period, The retract control period during which retract control is performed, After the retract control, the feeding speed is switched alternately between a forward feeding period and a reverse feeding period, and the feeding control method is changed to one cycle consisting of a forward feeding period and a reverse feeding period, and a start base period is set to move the tip position of the welding wire or filler wire to a predetermined reference value. After the aforementioned start base period, there is a start initial condition period in which the predetermined welding conditions are maintained for a predetermined period using the feed control method, A program characterized by having at least the following.

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