Control method, welding power source, welding system and control program

Abstract

To achieve excellent penetration performance, regardless of the presence or absence of a pulse, even when a maximum welding current is 500 A or less, in gas metal arc welding.SOLUTION: A control method in gas metal arc welding includes the steps of inputting a detected instantaneous voltage (Vo) and an average voltage (Vave) calculated from the instantaneous voltage (Vo) to a control part, calculating an error (Verr) of an arc voltage on the basis of the following expression (A) including at least the instantaneous voltage (Vo), the average voltage (Vave), an arc voltage reference value (Vsa), in the control part, and a ratio R, and calculating any one command value of at least a current and a voltage, on the basis of the error (Verr) of the arc voltage, wherein the expression (A) is Verr={R×(Vsa-Vo)}+{(1-R)×(Vsa-Vave)}, and the ratio R is 0.25 or more.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a control method, a welding power source, a welding system, and a control program for gas metal arc welding. [Background technology]

[0002] In gas metal arc welding, in order to achieve excellent penetration, welding conditions have traditionally been set to create a "buried arc" state. A buried arc generally refers to an arc state that occurs when the arc pressure (hereinafter also referred to as "arc pressure") generated between the welding wire (electrode) and the base metal (hereinafter also referred to as the "workpiece") pushes the molten part (hereinafter also referred to as the "molten pool") on the base metal side, creating a depression, and the tip of the welding wire enters the space (hereinafter also referred to as the "buried space") created by this depression. Stably maintaining this buried arc state can achieve deep penetration and reduce welding defects (lack of fusion, blowholes, etc.).

[0003] Here, examples of conventional techniques for stably maintaining a buried arc include Patent Documents 1 and 2. Patent Document 1 discloses a consumable electrode arc welding method in which a welding wire is fed to a portion of a base metal to be welded and a welding current of an average current of 300 A or more is supplied to the welding wire to generate an arc between the tip of the welding wire and the portion to be welded, thereby welding the base metal, in which the welding wire is fed at a speed at which the tip enters a buried space surrounded by a concave molten portion formed in the base metal by the arc generated between the tip and the portion to be welded, the welding current is varied, and the welding current during high-current periods is controlled so that droplets are transferred from the tip of the welding wire to the side of the molten portion multiple times during each high-current period.

[0004] Furthermore, Patent Document 2 discloses a technology that includes a mode setting circuit that selects a first mode for welding with a buried arc or a second mode for welding with an open arc, a feed rate control circuit that controls the feed rate so that the welding wire feed rate increases when the extension length increases and decreases when the extension length decreases, and a voltage control circuit that controls the output of the power supply unit so that the output voltage increases when the extension length increases and decreases when the extension length decreases, and that the amount of change in output voltage relative to the amount of change in feed rate according to the extension length of the welding wire is smaller when the first mode is set than when the second mode is set. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2018 / 105548 [Patent Document 2] Japanese Patent Publication No. 2020-192587 Summary of the Invention [Problem to be solved by the invention]

[0006] In both Patent Documents 1 and 2, the conditions for stably maintaining a buried arc require the use of a pulsed current and a large current of 300 A or more on average (maximum welding current: 800 A), and so they are only applicable to a limited current range. Furthermore, there are equipment limitations, such as the need to use a power source capable of outputting a maximum welding current of 1000 A or to use multiple power sources in parallel. Neither Patent Document 1 nor Patent Document 2 can be applied to a general-purpose welding power source capable of outputting a maximum welding current of 500 A.

[0007] The present invention has been made in view of the above-mentioned problems, and its object is to provide a control method, welding power source, welding system, and control program for gas metal arc welding that can achieve excellent penetration performance regardless of whether a pulse is used or not, and even when the maximum welding current is 500 A or less. [Means for solving the problem]

[0008] The present invention comprises the following configurations.

[0009] (1) A control method for gas metal arc welding, comprising: inputting the detected instantaneous voltage (Vo) and the average voltage (Vave) calculated from the instantaneous voltage (Vo) into a control unit; In the control unit, calculating an arc voltage error (Verr) based on the following formula (A) including at least the instantaneous voltage (Vo), the average voltage (Vave), the arc voltage reference value (Vsa), and a ratio R: calculating a command value for at least one of a current and a voltage based on the arc voltage error (Verr); and The control method, wherein the ratio R is 0.25 or more. Verr={R×(Vsa-Vo)}+{(1-R)×(Vsa-Vave)}····Formula (A)

[0010] (2) A welding power source used for gas metal arc welding, an average arc voltage calculation unit that calculates an average voltage (Vave) that is an average value of instantaneous voltages (Vo) detected during a predetermined period; a control circuit that calculates an arc voltage error (Verr) based on inputs of the instantaneous voltage (Vo) and the average voltage (Vave), and calculates at least one command value of either current or voltage based on the arc voltage error (Verr); The control circuit calculates the arc voltage error (Verr) based on the following formula (A) including at least the instantaneous voltage (Vo), the average voltage (Vave), the arc voltage reference value (Vsa), and a ratio R: The welding power source, wherein the ratio R is 0.25 or more. Verr={R×(Vsa-Vo)}+{(1-R)×(Vsa-Vave)}····Formula (A)

[0011] (3) A welding system equipped with a welding power source for use in gas metal arc welding, The welding power source includes: an average arc voltage calculation unit that calculates an average voltage (Vave) that is an average value of instantaneous voltages (Vo) detected during a predetermined period; a control circuit that calculates an arc voltage error (Verr) based on inputs of the instantaneous voltage (Vo) and the average voltage (Vave), and calculates at least one command value of either current or voltage based on the arc voltage error (Verr); The control circuit calculates the arc voltage error (Verr) based on the following formula (A) including at least the instantaneous voltage (Vo), the average voltage (Vave), the arc voltage reference value (Vsa), and a ratio R: The welding system, wherein the ratio R is 0.25 or greater. Verr={R×(Vsa-Vo)}+{(1-R)×(Vsa-Vave)}····Formula (A)

[0012] (4) A control program in gas metal arc welding that, when executed by a control circuit, The detected instantaneous voltage (Vo) and the average voltage (Vave) calculated from the instantaneous voltage (Vo) are input, Calculating an arc voltage error (Verr) based on the following formula (A) including at least the instantaneous voltage (Vo), the average voltage (Vave), the arc voltage reference value (Vsa), and a ratio R, Calculating at least one command value of current or voltage based on the arc voltage error (Verr); The control program, wherein the ratio R is 0.25 or more. Verr={R×(Vsa-Vo)}+{(1-R)×(Vsa-Vave)}····Formula (A) [Effects of the Invention]

[0013] According to the present invention, regardless of whether a pulse is used or not, and even when the maximum current is 500 A or less, the occurrence of a short circuit can be suppressed and the buried arc state can be stably maintained, thereby providing excellent penetration performance. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram showing an example of the configuration of an arc welding system according to this embodiment. [Figure 2] FIG. 2 is a block diagram of the welding power supply according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] When pulses are not applied and the maximum current is 500 A or less, maintaining a stable buried arc requires shortening the arc length and suppressing arc length fluctuations. This is because shortening the arc length suppresses arc spread and increases the arc current density, which increases the arc pressure on the molten pool and presses down the molten pool surface into a concave shape. In other words, even when the maximum current is 500 A or less, shortening the arc length can create a buried space. However, the arc length is prone to fluctuation due to external disturbances, and a short arc length can easily lead to short circuits, making "maintaining a short arc length" a specific challenge.

[0016] The present invention achieves excellent penetration performance by suppressing short circuits while maintaining a short and stable arc length through the control described in the following embodiments. Furthermore, even if a short circuit occurs, the present invention can achieve more favorable penetration performance by adding control to instantly release the short circuit, as described below. Keeping the arc length short is synonymous with keeping the arc voltage low. Generally, under the same feed rate conditions, setting the arc voltage high will increase the arc length, and setting the arc voltage low will decrease the arc length.

[0017] An embodiment of the present invention will be described below with reference to the drawings. Note that this embodiment is an example of a case where a welding robot is used, and the welding control method of the present invention is not limited to the configuration of this embodiment. For example, the welding control method of the present invention may be applied to an automatic welding device using a cart, or to a small, portable welding robot. Furthermore, this embodiment uses a general-purpose welding power source that can output a maximum welding current of 500 A, and the welding current is not pulsed.

[0018] <Arc welding system overview> First, an outline of an arc welding system used in the control method of this embodiment will be described. Fig. 1 is a schematic diagram showing an example of the configuration of an arc welding system according to this embodiment. Arc welding system 10 includes a welding robot 20, a welding power source 30, a control device 40, a controller 50, a feeder (not shown), and a shielding gas supply device (not shown).

[0019] Welding power source 30 is connected to welding robot 20 via a positive power cable (not shown) so as to be able to energize welding wire 22, which is a consumable electrode, and is connected to an object to be welded (hereinafter also referred to as "work") W via a negative power cable (not shown). The connection state shown in Fig. 1 is for welding with reverse polarity; to weld with positive polarity, the polarity of welding power source 30 should be reversed.

[0020] Furthermore, welding power source 30 and a feeder for feeding welding wire 22 are connected by a signal line (not shown), and the feed speed of welding wire 22 can be controlled.

[0021] The welding robot 20 is equipped with a welding torch 21 as an end effector. The welding torch 21 has an energization mechanism, i.e., a contact tip (not shown), that energizes the welding wire 22. When energized from the contact tip, the welding wire 22 generates an arc from its tip, and the generated heat welds the workpiece W, which is the welding target.

[0022] Furthermore, the welding torch 21 is equipped with a shielding gas nozzle (not shown) that is a mechanism for spraying shielding gas. In this embodiment, the shielding gas is not particularly limited, but it is possible to use commonly used carbon dioxide gas or a mixture of argon gas (hereinafter also referred to as "Ar") and carbon dioxide gas. This shielding gas is supplied from a shielding gas supply device.

[0023] The welding wire 22 used in this embodiment may be either a solid wire containing no flux or a flux-cored wire containing flux. The material of the welding wire 22 is not particularly limited, and may be, for example, mild steel, stainless steel, aluminum, or titanium, or the wire surface may be plated with copper or the like. Furthermore, the diameter of the welding wire 22 is not particularly limited. In this embodiment, the upper limit of the diameter is preferably 1.6 mm, and the lower limit of the diameter is preferably 0.8 mm.

[0024] Furthermore, the workpiece W in this embodiment is not particularly limited, and the joint shape, welding position, and groove shape are also not particularly limited.

[0025] Control device 40 mainly controls the operation of welding robot 20. Control device 40 holds teaching data that predefines the operation pattern, welding start position, welding end position, welding conditions, weaving operation, etc. of welding robot 20, and instructs welding robot 20 on these data to control the operation of welding robot 20. Control device 40 also provides welding conditions such as welding current, arc voltage, and wire feed speed to welding power source 30 during welding work in accordance with the teaching data.

[0026] The controller 50 is connected to the control device 40, and creates or displays programs for operating the welding robot 20, inputs teaching data, and sends the programs to the control device 40. The controller 50 also has a function for manually operating the welding robot 20. The connection between the controller 50 and the control device 40 may be wired or wireless.

[0027] In response to a command from the control device 40, the welding power source 30 supplies power to the welding wire 22 and the workpiece W, thereby generating an arc between the welding wire 22 and the workpiece W. In response to a command from the control device 40, the welding power source 30 also outputs a signal to the feeder to control the speed at which the welding wire 22 is fed.

[0028] <Functional configuration of welding power source> 2 is a block diagram of a welding power supply according to this embodiment. The welding power supply 30 includes a power supply unit PM that supplies power for generating an arc to perform welding, a welding current setting unit IS that outputs a welding current setting signal Is, an output voltage setting unit VS that outputs a voltage setting signal Vs, an arc voltage control circuit 312 that receives signals such as a detected instantaneous voltage detection signal Vo and an average voltage Vave of the detected instantaneous voltage detection signal Vo and calculates and outputs a correction current Ierr, a current setting circuit 311 that receives the correction current Ierr and the welding current setting signal Is and outputs a target current command Ir that serves as a control variable for the power supply PM, an output current control circuit 31 that includes at least the arc voltage control circuit 312 and the current setting circuit 311, a voltage detection unit VD that detects the arc voltage during welding and outputs the instantaneous voltage detection signal Vo, a current detection unit ID that detects the welding current during welding and outputs the welding current detection signal Io, a short-circuit / arc discrimination circuit 32 that discriminates between a short-circuit period and an arc period based on the instantaneous voltage detection signal Vo, and a reactor WL.

[0029] The power supply unit PM receives an input from a commercial power source such as a three-phase 200V power supply, and controls the output of the input AC voltage using an inverter, inverter transformer, rectifier, etc. (not shown) in accordance with a current error amplification signal Ei, which is an error amplification signal between a target current command signal Ir (described later) and a welding current detection signal Io, to output a welding current and an arc voltage. A reactor WL is also provided to smooth the output voltage.

[0030] The current detection unit ID detects the welding current during welding and outputs a welding current detection signal Io. The welding current detection signal Io is converted into a digital signal by an A / D conversion unit (not shown) and input to a current error amplifier circuit EI, an arc voltage control circuit 312, and other control circuits (not shown). The current error amplifier circuit EI inputs a current error amplified signal Ei to the power supply unit PM. The power supply unit PM controls the output of an inverter, inverter transformer, rectifier, etc. in accordance with this current error amplified signal Ei, and outputs the welding current and arc voltage.

[0031] The voltage detection unit VD detects the arc voltage during welding and outputs an instantaneous voltage detection signal Vo. The instantaneous voltage detection signal Vo may also be referred to as a voltage detection signal Vo. The instantaneous voltage detection signal Vo is converted into a digital signal by an A / D conversion unit (not shown) and input to the arc voltage control circuit 312, the short circuit / arc discrimination circuit 32, the average arc voltage calculation unit 33, and other control circuits.

[0032] The output current control circuit 31 includes at least an arc voltage control circuit 312 and a current setting circuit 311, which will be described later, and outputs a target current command signal Ir. It may also include a memory unit DB (not shown). The memory unit DB stores in advance data such as various initial setting signals, thresholds applied in each judgment and calculation unit, and output characteristics of the welding power source 30, such as the external characteristics Ac of the welding power source 30, and outputs signals to each circuit and unit. For example, the memory unit DB may store in advance a welding current setting signal Is, a voltage setting signal Vs, a wire feed speed setting signal, waveform control settings, constants for calculations in various circuits, and the like.

[0033] In this embodiment, a welding current setting signal Is and a voltage setting signal Vs are input from a welding current setting unit IS and an output voltage setting unit VS, and various setting values ​​such as an external characteristic Ac are input to various circuits via a memory unit DB (not shown).

[0034] As will be described later, the arc voltage control circuit 312 in the output current control circuit 31 receives at least the welding current setting signal Is, the voltage setting signal Vs, the instantaneous voltage detection signal Vo, the average voltage Vave of the detected instantaneous voltage detection signal Vo, and the welding current detection signal Io as inputs, and is used to calculate the correction current Ierr based on these.

[0035] A correction current Ierr is input to a current setting circuit 311. The current setting circuit 311 adds a welding current setting signal Is output from a welding current setting unit IS to the correction current Ierr, and outputs a target current command signal Ir to a current error amplifier circuit EI (see equation (1)). It is preferable to apply a limiter (limit the amount of change) to the target current command signal Ir.

[0036] Ir = Is + Ierr (1)

[0037] The correction current Ierr may be input to the current setting circuit 311 not only from the arc voltage control circuit 312 but also from other control circuits (not shown).

[0038] In this embodiment, a short circuit / arc discrimination signal is input from the short circuit / arc discrimination circuit 32 to the current setting circuit 311. As will be described later, the present invention can suppress the occurrence of a short circuit by performing predetermined control during the arc period, and can stably maintain the buried arc state, thereby achieving excellent penetration performance. In other words, when the discrimination result indicates that the current is an arc period, the control of the present invention is performed during the arc period or any section within the arc period.

[0039] The present invention relates to control for suppressing a short circuit. However, when a short circuit occurs, i.e., when the determination result indicates that a short circuit period has occurred, better penetration performance can be achieved by switching to early short circuit release control, which will be described later. In this embodiment, a plurality of preset control modes are selected before welding. At this time, when the control mode of the present invention is selected, the short circuit control becomes the above-described early short circuit release control. In other words, when another control mode is selected, short circuit control parameters different from those of the early short circuit release control may be applied to perform short circuit control.

[0040] The short / arc determination circuit 32 determines whether the period is an arc period or a short circuit period based on the instantaneous voltage detection signal Vo. In this embodiment, the value of the instantaneous voltage detection signal Vo is compared with a predetermined determination voltage Vth, and a period in which the instantaneous voltage detection signal Vo exceeds the determination voltage Vth (Vo>Vth) is determined to be an arc period, and a period in which the instantaneous voltage detection signal Vo is equal to or less than the determination voltage Vth (Vo≦Vth) is determined to be a short circuit period.

[0041] The average arc voltage calculation unit 33 receives the instantaneous voltage detection signal Vo as input and calculates the average voltage Vave as the average over a predetermined period. If the averaging period is too short, the value will be close to the instantaneous voltage, causing the control output to fluctuate sensitively, which may cause arc instability. On the other hand, if the period is too long, the transient response will be slow, so it is preferable to select a period from the range of 20 to 200 msec.

[0042] <Control method of arc voltage control circuit> Next, a control method for the arc voltage control circuit 312 according to this embodiment will be described in detail.

[0043] Welding current setting signal Is, voltage setting signal Vs, instantaneous voltage detection signal Vo, average voltage Vave, welding current detection signal Io, and external characteristic (Ac) are input to arc voltage control circuit 312. Arc voltage control circuit 312 calculates arc voltage reference value Vsa from voltage setting signal Vs, external characteristic Ac, welding current setting signal Is, and welding current detection signal Io, as shown in equation (2).

[0044] Vsa=Vs+Ac×(Is-Io)...Equation (2)

[0045] The arc voltage control circuit 312 then calculates the error Verr from the calculated Vsa, average voltage Vave, instantaneous voltage detection signal Vo, and a preset instantaneous voltage ratio R, as shown in equation (3). Here, the ratio R should be set in the range of 0 to 1.00. In this embodiment, the instantaneous voltage ratio R is used, but a calculation formula using the average voltage ratio may also be used.

[0046] Verr={R×(Vsa-Vo)}+{(1-R)×(Vsa-Vave)}····Formula (3)

[0047] The arc voltage control circuit 312 further calculates the correction current Ierr using the PI control formula shown in Equation (4) based on the calculated Verr. Here, Gp denotes the P gain of the PI control, and Gi denotes the i gain of the PI control. The values ​​of Gp and Gi may be set in advance in a storage unit DB or the like. In this embodiment, an optimal gain is set depending on the set value of the wire feed speed.

[0048] Ierr=Gp×Verr+Gi×Σ(Verr)...Equation (4)

[0049] <Instantaneous voltage ratio R: 0.25 or more> In the present invention, the instantaneous voltage ratio R in the above control formula must be 0.25 or greater. As shown in Table 1 below, if the instantaneous voltage ratio R is less than 0.25, the arc cannot be restored once it becomes unstable due to a disturbance. In other words, the arc length cannot be kept short. On the other hand, if the instantaneous voltage ratio R is 0.25 or greater, the arc length can be kept short continuously, and the effect of deep penetration can be achieved. Furthermore, if the instantaneous voltage ratio R is 0.90 or greater, the arc length can be kept short even more stably.

[0050] [Table 1]

[0051] <Welding conditions> The welding conditions corresponding to Table 1 above are as follows: Welding wire: JIS Z3312 YGW15 welding wire, wire diameter: φ1.2mm Shielding gas: Ar+20%CO2 CTWD (Chip-to-Workpiece Distance): 22mm Welding speed: 50cm / min Torch angle: forward angle, backward angle 0° Wire feed speed: 13 m / min (equivalent to a set current of 330 A) Arc voltage setting: 31.4V

[0052] <Early short-circuit release control> Although the arc period control method of the present invention is effective in suppressing short circuits, some short circuits do occur. As described above, when the proportion of short circuit time is large, penetration performance tends to decrease. Therefore, in the present invention, control is performed to quickly release the short circuit in order to reduce the proportion of short circuit time. Specifically, immediately after the short circuit / arc discrimination circuit 32 determines that a short circuit period has occurred, the current setting circuit 311 instantaneously outputs a short circuit release current to the current error amplifier circuit EI. The instantaneous short-circuit releasing current referred to here means increasing the current at a rate of 200 A / msec or more up to a predetermined short-circuit releasing current value. The current setting circuit 311 may maintain the current value at the short-circuit releasing current value until the short-circuit period is completed, that is, until the short-circuit / arc determination circuit 32 determines that the short circuit has been released.

[0053] The release of the short circuit described above is similar to the start of the arc period, that is, the current setting circuit 311 may maintain the current value at the short circuit release current value until the short circuit / arc determination circuit 32 determines that the arc period has started.

[0054] In addition, in the present invention, after the early short circuit release control is performed, a separate control may be provided during the arc period before the control of the present invention is performed, depending on the welding conditions after the short circuit release. The welding conditions after the short circuit release include the presence or absence of droplets after the short circuit release and vibration of the molten pool.

[0055] By carrying out the above control, even if a short circuit occurs, it is possible to quickly release the short circuit, which means that the total short circuit time can be reduced, resulting in better penetration performance.

[0056] The present invention is not limited to the above-described embodiments, and it is also intended that the various configurations of the embodiments be combined with each other, and that modifications and applications be made by those skilled in the art based on the description in the specification and well-known techniques, and these modifications and applications are included in the scope of protection sought.

[0057] As described above, the present specification discloses the following:

[0058] (1) A control method for gas metal arc welding, comprising: inputting the detected instantaneous voltage (Vo) and the average voltage (Vave) calculated from the instantaneous voltage (Vo) into a control unit; In the control unit, calculating an arc voltage error (Verr) based on the following formula (A) including at least the instantaneous voltage (Vo), the average voltage (Vave), the arc voltage reference value (Vsa), and a ratio R: calculating a command value for at least one of a current and a voltage based on the arc voltage error (Verr); and The control method, wherein the ratio R is 0.25 or more. Verr={R×(Vsa-Vo)}+{(1-R)×(Vsa-Vave)}····Formula (A)

[0059] According to this control method, excellent penetration performance can be achieved regardless of whether a pulse is used or not, and even when the maximum welding current is 500 A or less.

[0060] (2) determining whether a short circuit or an arc exists; Immediately after determining that a short circuit has occurred, increasing the current to a predetermined short-circuit release current value; The control method according to (1), further comprising:

[0061] According to this control method, the proportion of short circuit time can be reduced and penetration performance can be improved.

[0062] (3) The control method according to (1) or (2), characterized in that the arc voltage reference value (Vsa) is calculated based on at least a voltage set value (Vs) and an external characteristic (Ac).

[0063] According to this control method, the arc voltage reference value (Vsa) can be determined according to the external characteristics.

[0064] (4) The control method according to any one of (1) to (3), wherein the ratio R is 0.90 or more.

[0065] According to this control method, excellent penetration performance can be achieved.

[0066] (5) The short-circuit release current value is greater than a set current, The control method according to (2), characterized in that in the step of increasing the current, immediately after determining that the short circuit has occurred, the current is increased to the short circuit release current value at a gradient of 200 A / msec or more, and the value of the current is maintained at the short circuit release current value until it is determined that the short circuit has been released.

[0067] According to this control method, the proportion of short circuit time can be reduced and penetration performance can be improved.

[0068] (6) A welding power source used for gas metal arc welding, an average arc voltage calculation unit that calculates an average voltage (Vave) that is an average value of instantaneous voltages (Vo) detected during a predetermined period; a control circuit that calculates an arc voltage error (Verr) based on inputs of the instantaneous voltage (Vo) and the average voltage (Vave), and calculates at least one command value of either current or voltage based on the arc voltage error (Verr); The control circuit calculates the arc voltage error (Verr) based on the following formula (A) including at least the instantaneous voltage (Vo), the average voltage (Vave), the arc voltage reference value (Vsa), and a ratio R: The welding power source, wherein the ratio R is 0.25 or more. Verr={R×(Vsa-Vo)}+{(1-R)×(Vsa-Vave)}····Formula (A)

[0069] This welding power source can provide excellent penetration performance regardless of whether or not a pulse is used, even when the maximum welding current is 500 A or less.

[0070] (7) A welding system equipped with a welding power source for use in gas metal arc welding, The welding power source includes: an average arc voltage calculation unit that calculates an average voltage (Vave) that is an average value of instantaneous voltages (Vo) detected during a predetermined period; a control circuit that calculates an arc voltage error (Verr) based on inputs of the instantaneous voltage (Vo) and the average voltage (Vave), and calculates at least one command value of either current or voltage based on the arc voltage error (Verr); The control circuit calculates the arc voltage error (Verr) based on the following formula (A) including at least the instantaneous voltage (Vo), the average voltage (Vave), the arc voltage reference value (Vsa), and a ratio R: The welding system, wherein the ratio R is 0.25 or greater. Verr={R×(Vsa-Vo)}+{(1-R)×(Vsa-Vave)}····Formula (A)

[0071] This welding system can provide excellent penetration performance regardless of whether a pulse is used or not, even when the maximum welding current is 500 A or less.

[0072] (8) A control program for gas metal arc welding, which, when executed by a control circuit, The detected instantaneous voltage (Vo) and the average voltage (Vave) calculated from the instantaneous voltage (Vo) are input, Calculating an arc voltage error (Verr) based on the following formula (A) including at least the instantaneous voltage (Vo), the average voltage (Vave), the arc voltage reference value (Vsa), and a ratio R, Calculating at least one command value of current or voltage based on the arc voltage error (Verr); The control program, wherein the ratio R is 0.25 or more. Verr={R×(Vsa-Vo)}+{(1-R)×(Vsa-Vave)}····Formula (A)

[0073] According to this control program, excellent penetration performance can be achieved regardless of whether a pulse is used or not, and even when the maximum welding current is 500 A or less. [Explanation of symbols]

[0074] 10 Arc welding system 20 Welding robot 21 Welding torch 22 Welding wire 30 Welding power source 31 Output current control circuit 311 Current setting circuit 312 Arc voltage control circuit 32 Arc detection circuit 33 Average arc voltage calculation section 40 Control device 50 Controllers

Claims

1. 1. A control method for gas metal arc welding, comprising: inputting the detected instantaneous voltage (Vo) and an average voltage (Vave) calculated from the instantaneous voltage (Vo) into a control unit; a step of calculating, in the control unit, an error (Verr) of the arc voltage based on the following formula (A) including at least the instantaneous voltage (Vo), the average voltage (Vave), an arc voltage reference value (Vsa), and a ratio R; calculating a command value for at least one of a current and a voltage based on the arc voltage error (Verr); and The control method, wherein the ratio R is 0.25 or more. Verr={R×(Vsa-Vo)}+{(1-R)×(Vsa-Vave)}...Formula (A)

2. determining whether there is a short circuit or an arc; Immediately after determining that a short circuit has occurred, increasing the current to a predetermined short-circuit release current value; 2. The control method of claim 1, further comprising:

3. 2. The control method according to claim 1, wherein the arc voltage reference value (Vsa) is calculated based on at least a voltage set value (Vs) and an external characteristic (Ac).

4. 2. The control method according to claim 1, wherein the ratio R is 0.90 or greater.

5. The short-circuit release current value is greater than a set current, 3. The control method according to claim 2, wherein in the step of increasing the current, immediately after determining that the short circuit has occurred, the current is increased to the short circuit release current value at a gradient of 200 A / msec or more, and the value of the current is maintained at the short circuit release current value until it is determined that the short circuit has been released.

6. A welding power source used in gas metal arc welding, an average arc voltage calculation unit that calculates an average voltage (Vave) that is an average value of instantaneous voltages (Vo) detected during a predetermined period; a control circuit that calculates an arc voltage error (Verr) based on inputs of the instantaneous voltage (Vo) and the average voltage (Vave), and calculates at least one command value of either current or voltage based on the arc voltage error (Verr); The control circuit calculates an error (Verr) of the arc voltage based on the following formula (A) including at least the instantaneous voltage (Vo), the average voltage (Vave), the arc voltage reference value (Vsa), and a ratio R: A welding power source, wherein the ratio R is 0.25 or more. Verr={R×(Vsa-Vo)}+{(1-R)×(Vsa-Vave)}...Formula (A)

7. A welding system for gas metal arc welding, including a welding power source, The welding power source includes: an average arc voltage calculation unit that calculates an average voltage (Vave) that is an average value of instantaneous voltages (Vo) detected during a predetermined period; a control circuit that calculates an arc voltage error (Verr) based on inputs of the instantaneous voltage (Vo) and the average voltage (Vave), and calculates at least one command value of either current or voltage based on the arc voltage error (Verr); The control circuit calculates an error (Verr) of the arc voltage based on the following formula (A) including at least the instantaneous voltage (Vo), the average voltage (Vave), the arc voltage reference value (Vsa), and a ratio R: The welding system, wherein the ratio R is 0.25 or greater. Verr={R×(Vsa-Vo)}+{(1-R)×(Vsa-Vave)}...Formula (A)

8. A control program for gas metal arc welding, which, when executed by a control circuit, The detected instantaneous voltage (Vo) and the average voltage (Vave) calculated from the instantaneous voltage (Vo) are input, Calculating an arc voltage error (Verr) based on the following formula (A) including at least the instantaneous voltage (Vo), the average voltage (Vave), the arc voltage reference value (Vsa), and a ratio R, Calculating at least one command value of a current or a voltage based on the arc voltage error (Verr); The control program is characterized in that the ratio R is 0.25 or more. Verr={R×(Vsa-Vo)}+{(1-R)×(Vsa-Vave)}...Formula (A)

Images