Welding control method, welding power supply, welding system, and program

Abstract

In a weld feed control method, the present invention provides a welding control method that can suppress magnetic blowing while maintaining good welding workability. [Solution] A welding control method in a feeding control method that feeds a welding wire at a predetermined average wire feeding speed while alternately repeating forward feeding and reverse feeding, wherein the welding control method comprises at least a first control step of controlling at least one of the welding conditions according to the tip position of the welding wire, and a second control step of controlling at least one of the welding conditions based on at least one of detachment detection, magnetic blow detection, current setting value switching, a certain period of time elapsed since the current setting value switching, and voltage detection value.

Description

[Technical Field]

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

[0002] In welding processes where welding current and voltage constantly change, such as pulsed arc welding, magnetic blow is more likely to occur when the arc rigidity weakens, such as during the base period when the welding current is low. Generally, increasing the welding current strengthens the arc rigidity and prevents magnetic blow, but simply increasing the welding current during the base period has the problem of negatively impacting welding workability.

[0003] Patent Document 1 describes a method for pulsed arc welding using consumable electrodes, in which a welding wire is fed, and a peak period Tp is repeatedly performed, during which a peak current Ip and peak voltage are output at the electrode with positive polarity EP, and a base period Tb is performed, during which a base current Ib and base voltage are output. When the occurrence of magnetic blow is determined based on the rise in base voltage, the output of the welding power supply is controlled. In this method, when magnetic blow is determined at time t42, the output is switched from electrode with positive polarity EP to electrode with negative polarity EN, and an electrode with negative polarity current In is supplied during the period of negative polarity from time t42 to t44. When the elimination of magnetic blow is determined at time t44 based on the decrease in base voltage Vw, the output is returned to electrode with positive polarity EP.

[0004] Patent Document 2 describes a pulsed arc welding control method in which welding is performed by repeatedly feeding a welding wire and passing a peak period Tp that outputs a peak current Ip and a peak voltage, and a base period Tb that outputs a base current Ib and a base voltage Vb. In this method, the base current Ib is vibrated in a current range of 100A or less, with an amplitude of 40A or more, and a frequency of 300Hz or more. Magnetic blow is detected based on the rise in the base voltage Vb when an arc is generated, and the vibration of the base current Ib is started after the magnetic blow is detected. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2024-021966 [Patent Document 2] Japanese Patent Publication No. 2023-015630 [Overview of the project] [Problems that the invention aims to solve]

[0006] As described in Patent Documents 1 and 2, there are techniques for pulsed arc welding control methods that can suppress magnetic blow while maintaining a stable welding state. On the other hand, in recent years, a feeding control method has been developed that involves alternately switching the welding wire feeding speed between forward and reverse feeding periods, which is considered effective in reducing spatter. However, there is no method for this feeding control method that can suppress magnetic blow while maintaining good welding workability. Therefore, with the current feeding control method, if magnetic blow occurs, temporary arc instability occurs, and the intended spatter reduction effect cannot be achieved. In addition, in the feeding control method, the tip position of the welding wire changes and the arc length changes by alternately switching the welding wire feeding speed between forward and reverse feeding periods. Therefore, the timing at which magnetic blow is likely to occur is different from that of pulsed arc welding control methods, and thus the techniques described in Patent Documents 1 and 2 cannot solve the problem.

[0007] The present invention aims to provide a welding control method, a welding power source, a welding system, and a program that can suppress magnetic blowing while maintaining good welding workability in a feed control method. [Means for solving the problem]

[0008] The present invention consists of the following configuration.

[0009] (1) A welding control method in which welding wire is fed at a predetermined average wire feeding speed while alternately repeating forward feeding and reverse feeding, The welding control method is at least, A first control step that controls at least one of the welding conditions according to the tip position of the welding wire, A welding control method characterized by comprising: a second control step of controlling at least one of the welding conditions based on at least one of the following: detachment detection, magnetic blow detection, switching of current setting value, a certain period of time elapsed since switching of current setting value, and voltage detection value.

[0010] (2) A welding power source used for welding control in a feeding control method in which welding wire is fed at a predetermined average wire feeding speed while alternately repeating forward feeding and reverse feeding, A first control function that controls at least one of the welding conditions according to the tip position of the welding wire, A welding power supply characterized by having a second control function that controls at least one of the welding conditions based on at least one of the following: detachment detection, magnetic blow detection, current setting value switching, a certain period of time elapsed since the current setting value switching, and voltage detection value.

[0011] (3) A welding system that uses a feeding control method in which the welding wire is fed at a predetermined average wire feeding speed while alternately repeating forward feeding and reverse feeding, A first control function that controls at least one of the welding conditions according to the tip position of the welding wire, A welding system characterized by having a second control function that controls at least one of the welding conditions based on at least one of the following: detachment detection, magnetic blow detection, current setting value switching, a certain period of time elapsed since the current setting value switching, and voltage detection value.

[0012] (4) A program for performing welding control using a feeding control method that feeds welding wire at a predetermined average wire feeding speed while alternately repeating forward feeding and reverse feeding, In the device, a first control function that controls at least one of welding conditions according to a tip position of the welding wire; a second control function that controls at least one of welding conditions based on at least one of: detachment detection, magnetic blow detection, when a current set value is switched, after a certain period of time has elapsed since switching of a current set value, and a voltage detection value; a program characterized by causing the above functions to be realized. [Effects of the Invention]

[0013] According to the present invention, in the feeding control method, magnetic blow can be suppressed while maintaining good welding workability. [Brief Description of the Drawings]

[0014] [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 control of a welding power source, a robot control device, and a servo amplifier in the present embodiment. [Figure 3] FIG. 3 is a graph illustrating the relationship among a wire feeding speed, a wire tip position, and a current detection signal in the first control method of the present embodiment. [Figure 4] FIG. 4 is an explanatory diagram for the first control method according to the present embodiment. [Figure 5] FIG. 5 is an explanatory diagram for the second control method according to the present embodiment. [Figure 6] FIG. 6 is an explanatory diagram showing a modification of the present embodiment in control of welding current. [Figure 7] FIG. 7 is an explanatory diagram showing a modification of the present embodiment in control of welding current. [Figure 8] FIG. 8 is an explanatory diagram showing a modification of the present embodiment in control of welding current. [Figure 9] FIG. 9 is an explanatory diagram showing a modification of the present embodiment in control of welding current. [Figure 10]Figure 10 is an explanatory diagram showing a modified example of this embodiment in controlling the welding current. [Figure 11] Figure 11 is an explanatory diagram showing a modified example of this embodiment in controlling the welding current. [Modes for carrying out the invention]

[0015] Embodiments of the present invention will be described in detail below with reference to the attached drawings.

[0016] Hereinafter, embodiments of the welding control method, welding power supply, welding system, and program relating to this disclosure will be described in detail with reference to the drawings. Note that this embodiment is an example using a welding robot, and the welding control method according to the present invention is not limited to the configuration of this embodiment. For example, an automatic welding device using a trolley may be applied instead of the welding robot body, or a portable, compact welding robot may be applied.

[0017] Furthermore, the wire feeding control method includes a type that alternately switches the welding wire feeding speed between forward feeding periods and reverse feeding periods, and welds based on a short-circuit transition pattern that generates short-circuit periods and arc periods (hereinafter also referred to as the "short-circuit type wire feeding control method"), and a type that alternately switches the welding wire feeding speed between forward feeding periods and reverse feeding periods, and welds based on a globule transition pattern that suppresses the occurrence of short-circuit periods (hereinafter also referred to as the "short-circuit suppression type wire feeding control method"). With respect to the present invention, either type is not particularly important, but the present invention can be said to be particularly effective against the short-circuit suppression type wire feeding control method. This is because the short-circuit suppression type wire feeding control method is a method that consists only of arc periods (i.e., no short-circuit periods) or mainly arc periods, and is susceptible to the effects of magnetic blow, so the effects of the present invention are particularly evident. Therefore, in this embodiment, the system configuration of the short-circuit suppression type wire feeding control method will be described as an example.

[0018] <Configuration of the welding system> 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 robot 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.

[0019] The welding power supply 140 is connected to the welding robot 110 via a positive power cable (not shown) to energize the welding wire 100, and is connected to the workpiece (hereinafter also referred to as "base material") 200 via a negative power cable (not shown). 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.

[0020] 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.

[0021] 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.

[0022] The welding torch 111 is also equipped with a shielding gas nozzle, which is a mechanism for ejecting shielding gas. The type of shielding gas is not particularly limited, but the potential gradient (V / cm) and droplet transfer will differ depending on the shielding gas used and its mixing ratio. Therefore, the supply parameters may be changed for each type of shielding gas used. Examples of gases with a large potential gradient include carbon dioxide, nitrogen, hydrogen, and oxygen. On the other hand, examples of gases with a small potential gradient include argon and helium. When changing the potential gradient of the shielding gas using these gases individually or in mixing ratios, argon gas (hereinafter also referred to as "Ar gas") or carbon dioxide is mainly used, and the potential gradient increases in the order of argon gas alone (including impurities) > argon gas and carbon dioxide mixture > carbon dioxide gas alone (including impurities). Here, naturally, the potential gradient of the argon gas and carbon dioxide mixture increases as the mixing ratio of argon gas increases. The shielding gas is supplied from a shielding gas supply device (not shown).

[0023] 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.

[0024] 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.

[0025] 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 robot control device 120 mainly controls the operation of the welding robot 110. Therefore, the robot control device 120 may also be called a robot controller. The robot control device 120 holds teaching data that pre-defines 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. The robot control device 120 also provides the welding power supply 140 with welding conditions such as welding current, welding voltage (also called "arc voltage"), and feed speed during the welding operation, according to the teaching data.

[0026] As shown in Figure 1, the welding system 50 of this embodiment has a servo amplifier 160 that is independent of the welding power supply 140 or the robot control device 120. However, the servo amplifier 160 may be included in the welding power supply 140, or it may be included in the robot control device 120. Alternatively, the servo amplifier 160, welding power supply 140, and robot control device 120 may be configured as a single device.

[0027] The controller 150 is connected to the robot control device 120 and performs tasks such as creating or displaying programs for operating the welding robot 110, inputting teaching data, and inputting information to command the welding power supply 140. Information entered by the user into the controller 150 is provided to the robot control device 120. Information entered by the user into the controller 150 may also be provided to peripheral devices such as the welding power supply 140 via the robot control device 120. Examples of information to command the welding power supply 140 include the welding mode and welding conditions, as described later. Furthermore, the controller 150 may also have a function for manually operating the welding robot 110. The connection between the controller 150 and the robot control device 120 can be wired or wireless.

[0028] The welding power supply 140, in response to a command from the robot 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 robot control device 120.

[0029] 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 showing the schematic configuration related to the control of the welding power supply 140, robot 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, which corresponds to the "first control method" in this embodiment.

[0030] The welding power supply 140 is connected to the robot control device 120 via digital communication, and the robot control device 120 is connected to the servo amplifier 160 via digital communication. In other words, the servo amplifier 160, robot control device 120, and welding power supply 140 are connected in a linear fashion 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 robot control device 120 may be connected in a linear fashion in that order. This can be interpreted as the servo amplifier 160 and the welding power supply 140 being directly connected via digital communication.

[0031] In this embodiment, communication between the welding power supply 140 and the robot control device 120 is via CAN (Controller Area Network), which is one of the industrial field networks, and communication between the robot control device 120 and the servo amplifier 160 is via EtherCAT (Ethernet for Control Automation Technology) (registered trademark), which is one of the industrial field networks. However, the embodiment is not limited to these configurations.

[0032] The control system unit 141 of the welding power supply 140 is executed, for example, through the execution of a program by a robot 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, a voltage setting unit 36C, and an arc length control unit 36D. 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. The voltage setting unit 36C has the function of outputting a voltage setting value to the target current setting unit 36A, the arc length control unit 36D, etc. The arc length control unit 36D has the function of calculating a correction amount for at least one current setting signal CCset from among each period (peak period Dap, falling period Ddwn, base period Db, rising period Dup) and outputting it to the target current setting unit 36A. Furthermore, in the present invention, the value of at least one current setting signal CCset from among each period (peak period Dap, falling period Ddwn, base period Db, rising period Dup) is changed by the "second control method" described later.

[0033] The various conditions can be determined based on, for example, pre-entered settings by the operator for each welding mode, or a pre-prepared waveform control table or welding condition database. The welding modes, 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 robot control device 120 or the welding power supply 140. Here, the welding modes can be created by combining preconditions such as the type of shielding gas, the protrusion length, the type of wire, the composition of the wire, or the wire diameter.

[0034] Furthermore, there is a high-current period T during which the welding current is higher than the preset average welding current. IP (In this embodiment, the sum of the Dup and Dap periods) is the low current period T during which the current is lower than the preset average welding current. IB The various conditions for each period (peak period Dap, falling period Ddwn, base period Db, and rising period Dup) related to 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 refer to the current value, time, phase, wire forward and reverse frequencies with the forward and reverse periods as one cycle, wire amplitude, or various gain values. In this embodiment, it is preferable that the current during the high-current period is a current that is greater than the average current, and the current during the low-current period is a current that is less than the average current. The parameters related to the "second control method" described later can also be determined by the waveform control table linear calculation unit 37 based on a pre-prepared waveform control table.

[0035] The welding current is determined based on the phase related to the wire tip position (hereinafter referred to as "wire position phase" or "position phase") during the high-current period T IP and low current period T IB This shows a pulse waveform in which the welding current alternates. In this embodiment, the timing of the peak period Dap, fall period Ddwn, base period Db, and rise period Dup is controlled based on the wire position phase from 0 to 360° (0 to 2π), where 0° is when the wire tip is closest to the tip side and 180° is when it is closest to the base material side.

[0036] Based on the setting value of the average feed rate Favg in the welding condition information stored by the control system unit 141, the high current period T is calculated by the waveform control table linear calculation unit 37. IP The set current value Iap for the peak period Dap (hereinafter also referred to as "peak current Iap") and the low current period T IB The set current value Ib for the base period Db (hereinafter also referred to as "base current Ib") is set in the current setting unit 36.

[0037] In the case of this embodiment, the welding current is basically controlled by two values: a peak current Iap and a base current Ib. For this reason, the low current period T IB The start time may be represented as the low current start time, which is the time when transitioning to the base current Ib, that is, the start time of the falling period Ddwn. Also, the current suppression period T IB The end time may be represented as the time when the base current Ib ends, that is, the low current end time. The low current period T IB The start time and the current suppression period T IB The duration (time) of the falling period Ddwn and the duration (time) of the base period Db related to the end time are calculated in the waveform control table linear calculation unit 37. The high current period T IP The start time, that is, the start time of the rising period Dup, may be expressed as the high current start time, and the high current period T IPThe time at which this process ends may also be expressed as the high-current termination time. In Figure 3, the welding current is controlled using two values, peak current Iap and base current Ib, as the basic control method. However, the base period Db or peak period Dap may be divided into multiple sections, and the welding current settings may be changed accordingly. For example, in this embodiment, which will be described later, as shown in Figure 4, the base period Db is divided into a first base period Db1 and a second base period Db2, and these are controlled as the first base current Ib1 and the second base current Ib2, respectively. By controlling in this way, droplet transfer is stabilized, and the spatter reduction effect can be further obtained. Therefore, it is preferable to divide the base period Db or peak period Dap into multiple sections for control. Also, as shown in Figure 3, the timing of the high-current termination time is determined by the setting period d1 when the wire position phase starts at 0°, and the timing of the high-current start time is determined by the setting period d2 when the high-current termination time starts. This setting period is best set using phase. For example, if d1 is set to 190° and d2 to 120°, the high-current period will end when the wire position phase is 190° (d1) and begin when the wire position phase is 310° (d1+d2). Although the setting method is described above using d1 and d2, it is also possible to set it using the values ​​of d1 and d1+d2.

[0038] The various start and end times described 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.

[0039] 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 the wire position phase using an angle (0 to 2π), as described above.

[0040] 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, which includes periodic setting information and the difference between the operating signal of the actual forward and reverse feeding operation 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.

[0041] 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.

[0042] 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.

[0043] 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 defined as the forward feeding period T. P This is denoted as follows: 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 called the reverse feeding period T. N This is how it is written. In this embodiment, the feed motor is used during the positive feed period T. P and reverse payment period T NThe welding wire 100 is fed periodically, with the combined process of these two steps forming one cycle. The tip of the welding wire is generally considered to be the tip of the wire when the presence of molten droplets hanging from the wire tip is ignored. In other words, the wire melted by the arc is considered to have immediately transferred to the base material 200.

[0044] 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.

[0045] 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 (i.e., a gap portion to which the wire can escape if it slackens due to the influence 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 absolute encoder, which is a sensor built into the wire buffer 190, detects the amount of wire buffer as a rotation angle. 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.

[0046] 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.

[0047] In the current setting unit 36, the voltage setting unit 36C outputs a voltage setting value to the target current setting unit 36A, the arc length control unit 36D, etc. The setting value output by the voltage setting unit 36C may be the reference setting voltage Vset (which may also be called the "average voltage setting value" or "single-point center voltage setting value"), the voltage setting signal Vap during the peak period Dap, etc. For example, in this embodiment, the voltage setting signal Vap, which is the target value of the voltage applied between the welding tip and the base material 200 during the peak period Dap, is provided by the voltage setting unit 36C.

[0048] 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.

[0049] The current setting unit 36 ​​calculates a correction amount for the set current value based on the voltage detection signal Vo, the set voltage (reference set voltage Vset or the set voltage for each period), and the set current value set in the current setting unit 36 ​​(set current value Iap and / or set current value Ib), in order to stabilize the arc length (hereinafter also referred to as "arc length"), and outputs this to the target current setting unit 36A. The target current setting unit 36A resets each period or set current value based on the correction amount. The specific control method will be described later, but in this embodiment, correction is performed on at least the set current value Iap. Then, a current setting signal CCset corresponding to the reset period or current value is output to the current error amplification unit (PWM) 34.

[0050] The current error amplification unit 34 amplifies the difference between the current setting signal CCset, which is given as a 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.

[0051] 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.

[0052] The detachment detection unit 33 detects droplet detachment by comparing, for example, the value obtained by differentiating or second-deriving the voltage detection signal Vo passed through the LPF with a predetermined threshold value for detection. The threshold value for detection 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.

[0053] The waveform control table linear calculation unit 37 is provided with the average feed rate Favg of the weld wire 100 being fed. The average feed rate Favg is input by the controller 150, for example, and provided to the waveform control table linear calculation unit 37 via the robot control device 120. The average feed rate Favg can be stored in the feed setting data unit 35 via the controller 150. In this embodiment, the average feed rate Favg is treated as a command value, but the average welding current setting value may also be treated as a command value. The average feed rate Favg and the average welding current setting value are related in that determining one will determine the other by setting the melting parameters described later. In this embodiment, the feed setting data unit 35 is located in the welding power supply 140, but it may also be located in the robot control device 120.

[0054] The waveform control table linear calculation unit 37 determines values ​​such as peak current Iap, base current Ib, the time at which base current Ib starts, the time at which base current Ib ends, wire forward / reverse frequency, wire amplitude, or various gain values ​​from a given average feed rate Fabag, based on parameter tables separated for at least one welding mode, and outputs these values ​​to the current setting unit 36 ​​and the feed setting data unit 35. 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, etc., may be converted to a value of time or period cyc, and the converted value may be output to the current setting unit 36.

[0055] The feed setting data unit 35 receives and sets setting values ​​such as the average feed speed Favg, wire amplitude Wf, wire forward / reverse frequency Hf, and wire forward / reverse period Tf from the waveform control table linear calculation unit 37. The various setting values ​​in the feed setting data unit 35 may include not only the setting values ​​input from the waveform control table linear calculation unit 37, but also pre-stored setting values. 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.

[0056] In this embodiment, the tip position of the welding wire is defined as the position where the melting balance is achieved during welding. The period during which the feed rate is greater than the average feed rate Favg is defined as the positive feed period, and the period during which the feed rate is less than the average feed rate Favg is defined as the negative feed period. The feed is characterized by alternating positive and negative feed periods (hereinafter abbreviated as "amplitude feed"). The period during which the feed rate is less than the average feed rate Favg refers to a feed rate less than the average feed rate Favg, and includes negative feed rates, i.e., the rate at which the wire tip moves in the opposite direction to the position on the base material 200. The wire amplitude Wf ​​gives the range of change relative to the average feed rate Favg, and the wire forward / reverse period Tf gives the time of change in the wire amplitude, which is the repeating unit. The wire forward / reverse frequency Hf is the reciprocal of the wire forward / reverse period Tf.

[0057] 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 robot control device 120. In this embodiment, this feed setting data is communicated via CAN communication.

[0058] 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, the welding condition information held by the robot control device 120 is shown enclosed in a dashed line within the welding power supply 140 for convenience.

[0059] (Functional configuration of robot control device) As described above, the digital communication unit 122 of the robot 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 robot 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 robot control device 120 and the digital communication unit 162 of the servo amplifier 160 are connected by EtherCAT® communication.

[0060] (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.

[0061] In this embodiment, the feed rate command signal Fw is represented by the following equation (A). Fw=Ff+Favg...Formula (A)

[0062] 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.

[0063] 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.

[0064] <Control Method> Based on the system configuration described above, the control method of the present invention will be explained in detail.

[0065] (First control method) Figure 4 is an explanatory diagram of the first control method according to this embodiment. As the first control, the welding conditions are switched based on the tip position of the welding wire. Examples of welding conditions to be controlled include the welding current and the arc voltage. It is preferable to control the welding current based on the wire position phase, as in this embodiment shown in Figure 4, in order to more stably detach or drip the molten droplets formed on the tip of the welding wire. The parameters related to the first control will be described below based on Figure 4.

[0066] Of the set feeding parameters, at least the wire forward / reverse feeding period or wire amplitude values ​​should be provided in the parameter table, and the values ​​extracted from the parameter table based on the feeding speed setting should be used as the set values. The wire forward / reverse feeding period is defined as the sum of the forward feeding period and the reverse feeding period. It is preferable to optimize the wire forward / reverse frequency Hf, which is the reciprocal of the wire forward / reverse feeding period, and the size of the detached droplets, which depends on the droplet transfer form and arc pressure. Considering arc stability within the welding current range applied in gas shielded arc welding, it is more preferable to set the wire forward / reverse frequency Hf in the parameter table at an appropriate value. If the welding current range used is 500A or less, it is more preferable to set it within the range of 50 to 250Hz.

[0067] The wire amplitude is the range of change in the tip position of the welding wire 100 between the uppermost and lowermost ends. The "reference distance," which is the reference position for the wire amplitude Wf, can be set arbitrarily, but it is preferable from the viewpoint of arc stability to set the reference distance to the median value or near the median value of the wave height Wh. The value of the wire amplitude Wf ​​is preferably optimized according to the size of the detached droplets, which depends on the droplet transfer morphology and arc pressure, similar to the wire forward and reverse frequency Hf. When considering arc stability within the range of welding currents applied in gas shielded arc welding, it is more preferable to set the wire amplitude Wf ​​to an appropriate value in the parameter table. When the welding current range used is 500A or less, it is more preferable to set it within the range of 1 to 15 mm.

[0068] In this embodiment, the timing of the end of the high-current period (end of the peak period Dap) is set within the range of wire position phase 10° to 270°, and the timing of the start of the high-current period (end of the second base period Db2) is set within the range of wire position phase 150° to 90° of the next cycle. The values ​​extracted from the parameter table based on the feed rate setting are then used as the set values. By setting within this range, molten droplets formed on the tip of the welding wire can be detached or dripped more stably, and a good bead shape and penetration depth can be obtained.

[0069] (Second control method) Next, the second control method will be described. The second control method changes at least one welding condition for a certain period of time based on at least one signal from among (a) detachment detection, (b) magnetic blow detection, (c) current setting value switching, (d) a certain period of time after the current setting value switching, and (e) voltage detection value, while the control is being performed by the first control method described above. Magnetic blow detection is also called arc interruption detection.

[0070] The welding conditions to be changed include welding current and arc voltage. Basically, to increase the rigidity of the arc, the conditions should be changed so that the welding current is increased or the arc voltage is decreased. (b) Magnetic blow detection is performed by setting an arc voltage threshold (60-80V), and determining that magnetic blow has occurred when the detected arc voltage exceeds the threshold a predetermined number of times. If the trigger is to switch the current setting value, it is preferable to use the start position of the base period Db (the start position of Db1 in this embodiment), where the possibility of magnetic blow occurring is high, as the trigger.

[0071] Figure 5 is an explanatory diagram of the second control method according to this embodiment. In this example, the second control based on the departure signal of (a) departure detection described above will be explained.

[0072] Detachment detection is initiated in the aforementioned detachment detection unit 33 from the start of the base period Db (start of the first base period Db1). If there is any indication of droplet detachment during the base period Db (either the first base period Db1 or the second base period Db2), a detachment detection signal DTR is output. When the detachment detection signal DTR is input to the current setting unit 36, the base current Ib is increased based on at least a predetermined increase in welding current and maintenance time. In this embodiment, the increased base current Ib refers to at least one of the first base current Ib1 or the second base current Ib2. For example, if the first base current Ib1 is 80A and the parameter table is set to a welding current increase of 50A and an increased current maintenance time of 5msec, immediately after the detachment detection signal DTR is input during the first base period Db1, the first base current Ib1 becomes 130A (80A + 50A), and this current is maintained for 5msec. Hereafter, the period during which the welding current is increased or maintained by the second control is defined as the boost period. The parameter table may also include the slope (A / μs) until the welding current increases and the delay time from the input of the detachment detection signal DTR until the welding current starts to increase. If this delay time is 0 (zero), the welding current will increase immediately after the detachment detection signal DTR is input to the current setting unit 36, as in this embodiment.

[0073] Furthermore, in this embodiment, it is preferable to add (b) magnetic blow detection as a second control. During the boost period in which the welding current is increased, when a magnetic blow detection signal is input to the current setting unit 36, the welding current during the boost period may be increased or decreased a predetermined number of times. For example, if the wire forward / reverse cycle is 10 cycles and a "correction amount for increased current" (±10A / time) is set in the parameter table, when a magnetic blow detection signal is input to the current setting unit 36, the welding current during the boost period will increase or decrease by 10A each time for 10 cycles. The "correction amount for increased current" may be set between ±1 and ±50A. Here, if a magnetic blow detection signal is input during the specified number of times, the counter for the number of times is reset and starts counting again up to the specified number of times. Alternatively, instead of setting a specified number of times, the amount of increase in the welding current after correction by the magnetic blow detection signal may be updated as the set value for the increase in the welding current, and increased or decreased each time a magnetic blow detection signal is received. For example, if the initial setting for the increase in welding current is 50A and it is corrected to increase by another 10A, the setting value will be changed so that the increase in welding current after the next detachment detection signal DTR becomes 60A. Thus, it is preferable to apply (a) detachment detection and (b) magnetic blow detection in combination.

[0074] (modified version) The manner in which the welding current is increased or decreased during the boost period described above is not limited to maintaining a constant amount as shown in the above embodiment, but may also be sloping, curved, or pulsed, or a combination thereof.

[0075] In the second control method, at least one of the following controls may be applied to the welding current: gradually increasing it, maintaining it at a predetermined value for a certain period of time, and pulsed welding.

[0076] In the second control method, at least one of the following controls may be applied to the arc voltage: gradually decreasing it, maintaining it at a predetermined value for a certain period of time, and pulsed.

[0077] Figures 6 to 11 are explanatory diagrams showing modified examples of this embodiment in controlling the welding current. When controlling the arc voltage, the increase and decrease should be reversed compared to controlling the welding current. For example, in the case of Figure 6, which will be explained later, the phrase "a delay time may be provided, and the welding current may be gradually increased after a certain period of time has elapsed from the start of the base period" should be read as "a delay time may be provided, and the arc voltage may be gradually decreased after a certain period of time has elapsed from the start of the base period."

[0078] In the second control method shown in Figure 6, the welding current is gradually increased in a slope manner from the start of the base period, which is when the current setting value is switched. Alternatively, a delay time may be introduced so that the welding current is gradually increased after a certain period of time has elapsed from the start of the base period.

[0079] In the second control method shown in Figure 7, the welding current is gradually increased in a curved manner from the start of the base period, which is when the current setting value is switched. Alternatively, the welding current may be gradually increased exponentially or in a curved manner after a certain period of time has elapsed from the start of the base period.

[0080] In the second control method shown in Figure 8, the welding current is gradually increased in a slope manner from the start of the base period. In addition to this, control is performed to raise the welding current to a constant value (maintain a constant amount) in response to detachment detection by a detachment detection signal. Alternatively, the rate at which the welding current is gradually increased from the start of the base period, i.e., the slope of the slope shown in Figure 8, may be increased, and then control may be performed to lower the welding current to a constant value in response to detachment detection by a detachment detection signal.

[0081] In the second control method shown in Figure 9, the welding current is gradually increased in a slope manner after detachment detection by the detachment detection signal, but the rate at which the welding current is increased, i.e., the slope of the slope shown in Figure 9, is set in two stages.

[0082] In the second control method shown in Figure 10, the welding current is increased and then controlled in a pulsed manner after detachment detection is detected by a detachment detection signal.

[0083] In the second control method shown in Figure 11, after detecting detachment using a detachment detection signal, the welding current is increased to a predetermined value (maintained at a constant level), and then the welding current is controlled to gradually decrease in a curved manner.

[0084] Furthermore, the second control method may be switched ON and OFF depending on the situation. In this embodiment, it is preferable to switch the second control method ON and OFF depending on the position during weaving. Specifically, the control should be OFF at the center of the weaving and ON near both ends of the groove. By switching the control of the second control method in this way, the welding workability during weaving is further improved.

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

[0086] (1) A welding control method in which welding wire is fed at a predetermined average wire feeding speed while alternately repeating forward feeding and reverse feeding, The welding control method is at least, A first control step that controls at least one of the welding conditions according to the tip position of the welding wire, A welding control method characterized by comprising: a second control step of controlling at least one of the welding conditions based on at least one of the following: detachment detection, magnetic blow detection, switching of current setting value, a certain period of time elapsed since switching of current setting value, and voltage detection value.

[0087] (2) The welding conditions controlled in the first control step shall be at least the welding current, At least according to the tip position of the welding wire, The welding control method according to (1), characterized in that the welding current is controlled to be higher than a preset average welding current during high-current periods and lower than a preset average welding current during low-current periods.

[0088] (3) In the second control step, the welding conditions to be controlled are: A welding control method according to (1) or (2), characterized by controlling at least one of the welding current and arc voltage.

[0089] (4) In the second control step, with respect to the welding current, The welding control method according to (3), characterized by gradually increasing, maintaining a predetermined value for a certain period of time, and controlling at least one of the pulses.

[0090] (5) In the second control step described above, with respect to the arc voltage, The welding control method according to (3), characterized by controlling at least one of the following: gradually decreasing, maintaining a predetermined value for a certain period of time, and pulses.

[0091] (6) The welding control method according to (1), characterized in that when weaving is performed, the ON and OFF of the second control step is switched according to the weaving position.

[0092] (7) A welding power source used for welding control in a feeding control method in which welding wire is fed at a predetermined average wire feeding speed while alternately feeding forward and feeding backward, A first control function that controls at least one of the welding conditions according to the tip position of the welding wire, A welding power supply characterized by having a second control function that controls at least one of the welding conditions based on at least one of the following: detachment detection, magnetic blow detection, current setting value switching, a certain period of time elapsed since the current setting value switching, and voltage detection value.

[0093] (8) A welding system that uses a feeding control method in which the welding wire is fed at a predetermined average wire feeding speed while alternately repeating forward feeding and reverse feeding, A first control function that controls at least one of the welding conditions according to the tip position of the welding wire, A welding system characterized by having a second control function that controls at least one of the welding conditions based on at least one of the following: detachment detection, magnetic blow detection, current setting value switching, a certain period of time elapsed since the current setting value switching, and voltage detection value.

[0094] (9) A program for performing welding control using a feeding control method that feeds welding wire at a predetermined average wire feeding speed while alternately repeating forward feeding and reverse feeding, In the device, A first control function that controls at least one of the welding conditions according to the tip position of the welding wire, A program characterized by implementing a second control function that controls at least one of the welding conditions based on at least one of the following: detachment detection, magnetic blow detection, current setting value switching, a certain period of time elapsed since the current setting value switching, and voltage detection value. [Explanation of Symbols]

[0095] 1 AC power supply 2 Primary rectifier 3. Smoothing Capacitor 4 Switching elements 5 transformers 6 Secondary rectifier 7 Reactor 30 Inverter drive unit 31 Current detection unit 32 Voltage detection unit 33 Detachment detection unit 34 Current Error Amplification Section 35. Supply setting data section 36 Current setting section 36A target current setting section 36B Wire tip position conversion unit 36C Voltage setting section 36D Arc Length Control Unit 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 Robot control devices 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 welding control method in a wire feeding control method that feeds welding wire at a predetermined average wire feeding speed while alternately repeating forward feeding and reverse feeding, The welding control method is at least, A first control step that controls at least one of the welding conditions according to the tip position of the welding wire, A welding control method characterized by comprising: a second control step of controlling at least one of the welding conditions based on at least one of the following: detachment detection, magnetic blow detection, switching of current setting value, a certain period of time elapsed since switching of current setting value, and voltage detection value.

2. The welding conditions controlled in the first control step are at least the welding current, At least according to the tip position of the welding wire, The welding control method according to claim 1, characterized in that the welding current is controlled to have a high current period in which it is higher than a preset average welding current and a low current period in which it is lower than a preset average welding current.

3. In the second control step described above, the welding conditions to be controlled are: A welding control method according to claim 1 or 2, characterized by controlling at least one of the welding current and arc voltage.

4. In the second control step described above, with respect to the welding current, The welding control method according to claim 3, characterized by controlling at least one of the following: gradually increasing, maintaining a predetermined value for a certain period of time, and pulses.

5. In the second control step described above, the arc voltage is as follows: The welding control method according to claim 3, characterized by controlling at least one of the following: gradually decreasing, maintaining a predetermined value for a certain period of time, and pulses.

6. The welding control method according to claim 1, characterized in that when weaving is performed, the second control step is switched ON and OFF according to the weaving position.

7. A welding power source used for welding control in a feeding control method in which welding wire is fed at a predetermined average wire feeding speed while alternately repeating forward feeding and reverse feeding, A first control function that controls at least one of the welding conditions according to the tip position of the welding wire, A welding power supply characterized by having a second control function that controls at least one of the welding conditions based on at least one of the following: detachment detection, magnetic blow detection, current setting value switching, a certain period of time elapsed since the current setting value switching, and voltage detection value.

8. A welding system that employs a feeding control method in which the welding wire is fed at a predetermined average wire feeding speed while alternately repeating forward feeding and reverse feeding, A first control function that controls at least one of the welding conditions according to the tip position of the welding wire, A welding system characterized by having a second control function that controls at least one of the welding conditions based on at least one of the following: detachment detection, magnetic blow detection, switching of the current setting value, a certain period of time elapsed since the switching of the current setting value, and a voltage detection value.

9. A program for performing welding control using a feeding control method that feeds welding wire at a predetermined average wire feeding speed while alternately repeating forward feeding and reverse feeding, In the device, A first control function that controls at least one of the welding conditions according to the tip position of the welding wire, A program characterized by implementing a second control function that controls at least one of the welding conditions based on at least one of the following: detachment detection, magnetic blow detection, current setting value switching, a certain period of time elapsed since the current setting value switching, and voltage detection value.

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