Arc welding device

Abstract

An arc welding device 1 comprises a welding torch 2 that holds a welding wire 9, a welding power supply 4 that applies a welding voltage between the welding wire 9 and a workpiece 10, a current detection unit 5 that detects a welding current, and a controller 7 that intermittently repeats execution of voltage application control that makes the welding power supply 4 continuously apply alternating-current voltage or direct-current voltage as the welding voltage and determines whether there are abnormalities on the basis of whether there are at least a prescribed number of detection values that satisfy a prescribed condition among detection values from the current detection unit 5 during one completed execution of the voltage application control.

Description

Arc welding equipment

[0001] The present disclosure relates to an arc welding device that performs arc welding by applying a welding voltage between a welding wire and a workpiece.

[0002] Patent Document 1 discloses an arc welding device that performs arc welding by applying a welding voltage between a welding wire and a workpiece to cause a welding current to flow between the welding wire and the workpiece. This arc welding device includes a power supply that applies a welding voltage between the welding wire and the workpiece, and a determination unit that detects an abnormality when the arc interruption detection time, during which the welding current is below a predetermined value, exceeds a predetermined reference time.

[0003] Patent No. 5596394

[0004] In the anomaly detection method of Patent Document 1, when an arc welding apparatus is used to perform intermittent arc welding, such as stitch welding, if the set reference time is too short, the period during which arc welding is not intentionally performed exceeds the reference time, and the determination unit may erroneously detect an anomaly. On the other hand, if the set reference time is too long, detection may be missed. Therefore, the reference time for arc interruption detection must be appropriately set based on the pattern of periods during which arc welding is performed and not performed, which is time-consuming.

[0005] The present disclosure has been made in consideration of these points, and its purpose is to make it possible to determine whether or not an abnormality exists without setting a reference time for arc interruption detection time.

[0006] One aspect of the present disclosure is an arc welding device that performs arc welding by applying a welding voltage between a welding wire and a workpiece and flowing a welding current, and is characterized by comprising: a welding torch that holds the welding wire; a welding power source that applies the welding voltage between the welding wire and the workpiece; a detection unit that detects the welding voltage or the welding current; and a judgment unit that intermittently and repeatedly performs voltage application control to continuously apply an AC voltage or a DC voltage to the welding power source as the welding voltage, and determines whether or not there is an abnormality based on whether or not a predetermined number or more of detection values ​​that satisfy a predetermined condition are present among the detection values ​​of the detection unit during one execution of the voltage application control.

[0007] According to this aspect, the presence or absence of an abnormality can be determined based on whether or not a predetermined number of detection values ​​satisfy a predetermined condition among the detection values ​​of the detection unit during one execution of the voltage application control, thereby eliminating the need to set a reference time for the arc interruption detection time.

[0008] According to the present disclosure, it is possible to determine whether or not an abnormality exists without setting a reference time for the arc interruption detection time.

[0009] While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments and is not to be limited to the disclosed exemplary embodiments.

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the present invention, its applications, or its uses.

[0011] 1 and 2 show an arc welding apparatus 1 according to an embodiment of the present disclosure. The arc welding apparatus 1 includes a welding torch 2, a robot 3, a welding power source 4, a current detection unit 5, a voltage detection unit 6, a controller 7 as a determination unit, and a teach pendant 8. The arc welding apparatus 1 performs arc welding by applying a welding voltage between the welding wire 9 and the workpiece 10 while feeding the welding wire 9 toward the workpiece 10 and thereby causing a welding current to flow. The workpiece 10 is connected to the welding power source 4 via a connection that carries the welding current. A shielding gas such as carbon dioxide gas is sprayed onto the workpiece 10. The arc welding apparatus 1 performs stitch welding, in which arc welding is intermittently repeated while the welding point is moved. This allows a weld bead having a scaly appearance, such as the surface of a bicycle arm, to be formed on the workpiece 10.

[0012] The welding torch 2 holds a welding wire 9 .

[0013] The welding torch 2 is attached to the tip of the robot 3. The robot 3 is, for example, an articulated robot having a plurality of motors 31, and the robot 3 moves the welding torch 2.

[0014] The welding power source 4 applies a welding voltage between the welding wire 9 and the workpiece 10 to cause a welding current to flow.

[0015] The current detection unit 5 detects the welding current flowing between the welding wire 9 and the workpiece 10 .

[0016] The voltage detection unit 6 detects the welding voltage applied between the welding wire 9 and the workpiece 10 .

[0017] The controller 7 controls the robot 3 and the welding power source 4. The functions of the controller 7 are realized by a CPU 71, a detection value storage memory 72, and a memory (not shown) that stores programs and parameters.

[0018] During stitch welding, the controller 7 causes the welding power source 4 to continuously apply an AC voltage or a DC voltage as the welding voltage between the welding wire 9 and the workpiece 10, intermittently and repeatedly executing this voltage application control while moving the welding point under the control of the robot 3. After the voltage application control ends, the controller 7 causes the welding power source 4 to stop applying voltage between the welding wire 9 and the workpiece 10 until the next voltage application control is started. The length of the weld bead formed by one voltage application control, the spacing between adjacent weld beads, the duration of one voltage application control, and the time interval between voltage application controls are variable and can be set in the controller 7 based on user input to the teach pendant 8, for example. The spacing between adjacent weld beads is set to 1 mm, for example, but can also be set to 1 to 10 mm. The time interval between voltage application controls is set to 50 to 5,000 ms, for example.

[0019] Furthermore, the controller 7 receives the detection value of the current detection unit 5 from the current detection unit 5. Based on the detection value received from the current detection unit 5, the controller 7 determines whether or not an abnormality exists.

[0020] The teach pendant 8 sends a signal according to the user's input to the controller 7. Furthermore, the teach pendant 8 performs output such as displaying on a display in accordance with the output of the controller 7.

[0021] FIG. 3 is a flowchart illustrating the operation of the controller 7 from the start to the end of stitch welding.

[0022] First, in S101, the CPU 71 of the controller 7 starts executing the welding program for the robot 3. As a result, the robot 3 moves the welding torch 2, thereby moving the welding point.

[0023] Next, in S102, the controller 7 starts voltage application control. That is, the controller 7 causes the welding power source 4 to start applying an AC voltage or a DC voltage as the welding voltage. As a result, the welding power source 4 continuously applies an AC voltage as the welding voltage between the welding wire 9 and the workpiece 10. The CPU 71 of the controller 7 also starts a current value acquisition process that acquires the detection value of the current detection unit 5 at predetermined time intervals and stores the detected value in the detection value storage memory 72.

[0024] Next, in S103, the controller 7 ends the voltage application control. That is, the controller 7 causes the welding power source 4 to end the application of the AC voltage as the welding voltage. As a result, the welding power source 4 stops applying the AC voltage between the welding wire 9 and the workpiece 10. The CPU 71 of the controller 7 also ends the current value acquisition process.

[0025] Next, in S104, the controller 7 determines whether the current detection unit 5 detected one or more values ​​equal to or greater than a predetermined current threshold during the previous, i.e., immediately preceding, voltage application control. The predetermined current threshold is set to, for example, 8 A. If the controller 7 determines that the current detection unit 5 detected no values ​​equal to or greater than the predetermined current threshold during the previous voltage application control, the controller 7 proceeds to S105. On the other hand, if the controller 7 determines that the current detection unit 5 detected one or more values ​​equal to or greater than the predetermined current threshold during the previous voltage application control, the controller 7 proceeds to S106. Note that it is preferable to set the current threshold so that the number of detected values ​​equal to or greater than the current threshold during voltage application control corresponds to the number of short circuits (conduction) during that voltage application control. By setting the current threshold in this manner, the number of detected values ​​equal to or greater than the current threshold during voltage application control can be obtained, thereby confirming the number of short circuits (conduction) during voltage application control.

[0026] In S105, the controller 7 determines that an abnormality has occurred and ends the process. If the controller 7 determines that an abnormality has occurred, the controller 7 may cause the teach pendant 8 or another external output device (not shown) to output a predetermined signal indicating the abnormality.

[0027] In S106, the controller 7 determines that there is no abnormality. The controller 7 determines whether or not to end welding. If the controller 7 determines not to end welding (to continue welding), the process returns to S102. On the other hand, if the controller 7 determines to end welding, the process ends. The controller 7 ends the execution of the control program for the robot 3 and stops the movement of the welding point.

[0028] 3, the arc welding device 1 can perform stitch welding, which involves short arc welding sessions every 50 to 5000 ms. Each time a short arc welding session ends, the controller 7 determines whether or not an abnormality exists based on the detection value of the current detection unit 5 during the immediately preceding arc welding session.

[0029] Therefore, according to this embodiment, the presence or absence of an abnormality can be determined based on whether or not there was one or more detection values ​​equal to or greater than a predetermined current threshold among the detection values ​​of the current detection unit 5 during the previous voltage application control. This eliminates the need to set a reference time for the arc interruption detection time. Furthermore, since there are no missed or erroneous detections due to an inappropriate setting of the reference time for the arc interruption detection time, the presence or absence of an abnormality related to arc interruption can be determined more reliably than in Patent Document 1.

[0030] Furthermore, since the presence or absence of an abnormality is determined based on the number of detected values ​​that satisfy a predetermined condition during past voltage application control, the determination criteria can be set relatively freely.

[0031] Furthermore, since the determination of whether or not there is an abnormality is made based on the number of detected values ​​that satisfy a predetermined condition during the previous voltage application control, there is no need to consider the time during which the detected values ​​satisfy the predetermined condition, as in Patent Document 1.

[0032] Furthermore, the presence or absence of an abnormality is determined based on whether the detection value of the current detection unit 5 during past voltage application control was equal to or greater than a predetermined current threshold, so the determination criteria can be set precisely by setting the current threshold.

[0033] Furthermore, the robot 3 automatically moves the welding point while intermittently controlling the voltage application, allowing for precise intermittent arc welding. This allows for a beautiful weld bead appearance. Furthermore, any abnormalities can be automatically detected.

[0034] In this embodiment, in S104, the presence or absence of an abnormality is determined by determining whether or not one or more detected values ​​of the current detection unit 5 during the previous voltage application control are equal to or greater than a predetermined current threshold. However, the presence or absence of an abnormality may also be determined by determining whether or not one or more detected values ​​of the current detection unit 5 during a voltage application control that was executed before the previous one are equal to or greater than a predetermined current threshold.

[0035] In this embodiment, in S104, the presence or absence of an abnormality is determined by determining whether the current detection unit 5 detected one or more values ​​equal to or greater than the predetermined current threshold during one voltage application control run. However, the presence or absence of an abnormality may also be determined by determining whether the current detection unit 5 detected two or more or a predetermined number of values ​​equal to or greater than the predetermined current threshold during one voltage application control run. Specifically, the absence of an abnormality may be determined when the current detection unit 5 detected two or more or a predetermined number of values ​​equal to or greater than the predetermined current threshold during one voltage application control run. The predetermined number is preferably set according to the length of one voltage application control run. By setting the predetermined number to a small number, the presence or absence of an abnormality can be determined even when the period of one voltage application control run is relatively short. When the period of one voltage application control run is relatively long, the accuracy of the determination can be improved by setting the predetermined number to a large number.

[0036] Furthermore, in this embodiment, the presence or absence of an abnormality is determined based on the detection value of the current detection unit 5 during one completed cycle of the voltage application control. However, the determination may also be based on the detection value of the voltage detection unit 6 during one completed cycle of the voltage application control. Specifically, the presence or absence of an abnormality may be determined by determining whether or not there are two or more predetermined values ​​that are equal to or less than a predetermined voltage threshold among the detection values ​​of the voltage detection unit 6 during one completed cycle of the voltage application control. In other words, if there are two or more predetermined values ​​that are equal to or less than a predetermined voltage threshold among the detection values ​​of the voltage detection unit 6 during one completed cycle of the voltage application control, it may be determined that there is no abnormality (normal). The predetermined voltage threshold is set to, for example, 5 V.

[0037] The arc welding device disclosed herein can determine whether or not an abnormality exists without setting a reference time for the arc interruption detection time, and is useful as an arc welding device that performs arc welding by applying a welding voltage between a welding wire and a workpiece.

[0038] REFERENCE SIGNS LIST 1 Arc welding device 2 Welding torch 3 Robot 4 Welding power source 5 Current detection unit 6 Voltage detection unit 7 Controller (determination unit) 9 Welding wire 10 Workpiece

Claims

1. An arc welding device which performs arc welding by applying a welding voltage between a welding wire and a workpiece to cause a welding current to flow, comprising: a welding torch which holds the welding wire; a welding power source which applies the welding voltage between the welding wire and the workpiece; a detection unit which detects the welding voltage or the welding current; and a judgment unit which intermittently and repeatedly executes voltage application control which causes the welding power source to continuously apply an AC voltage or a DC voltage as the welding voltage, and judges the presence or absence of an abnormality based on whether or not a predetermined number or more of detection values ​​which satisfy a predetermined condition are present among the detection values ​​of the detection unit during one execution of the voltage application control.

2. An arc welding device according to claim 1, wherein the judgment section makes the judgment based on a detection value of the detection section during the previous voltage application control.

3. An arc welding device according to claim 1 or 2, wherein the detection unit detects the welding current, and the predetermined condition is that the welding current is equal to or greater than a predetermined current threshold value.

4. An arc welding apparatus as claimed in claim 1 or 2, further comprising a robot to which the welding torch is attached, and wherein the judgment unit intermittently repeats the voltage application control while moving the welding point by controlling the robot.

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