Arc-welding device and arc-welding method

Abstract

To calculate an amount of vibration of a welding torch in a welding start position.SOLUTION: When a welding torch 22 reaches a welding start position P, a wire feeding part 21 alternately conducts a first operation in which a welding wire 23 is moved forward until the welding wire 23 comes in contact with a workpiece W and a second operation in which the welding wire 23 in contact with the workpiece W is moved rearward. A control unit 14 calculates an amount of vibration of the welding torch 22 based on a feeding amount of the welding wire 23.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an arc welding apparatus and an arc welding method. [Background technology]

[0002] Patent Document 1 discloses an arc start control method for moving a welding torch attached to a manipulator of a welding robot to perform welding.

[0003] In the invention of Patent Document 1, the welding torch is moved in the welding wire feed direction at the welding start position to bring the wire tip closer to the workpiece. Then, when it is determined that the wire tip has come into contact with the workpiece, the robot is moved backward in the direction opposite to the wire feed direction to generate an arc. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4499303 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, when the welding torch is moved from a predetermined position to a welding start position and then stopped, the welding torch vibrates at the welding start position.

[0006] In this case, the faster the welding torch moves, the longer it takes for the vibration of the welding torch to converge at the welding start position. However, if arc welding is started before the vibration of the welding torch converges, there is a risk that welding quality cannot be ensured.

[0007] Furthermore, if there is a wait until the vibration of the welding torch subsides, the time before arc welding can be started will be longer, which will affect the tact time.

[0008] Here, it is possible to use an acceleration sensor to measure the moving speed of the welding torch, but this has the problem of high component costs. Therefore, the inventors of the present application have investigated whether it is possible to calculate the vibration amount of the welding torch at the welding start position without using an acceleration sensor.

[0009] The present invention has been made in consideration of the above-mentioned points, and an object of the present invention is to make it possible to calculate the vibration amount of the welding torch at the welding start position. [Means for solving the problem]

[0010] A first invention is an arc welding apparatus that supplies a welding wire to a workpiece to perform arc welding, the apparatus comprising: a wire feeder that feeds the welding wire; a welding torch that holds the welding wire and supplies power to the welding wire to generate an arc between the welding wire and the workpiece; a robot that changes a position of the welding torch relative to the workpiece; and a control unit that controls operation of the wire feeder and the robot, wherein the control unit controls operation of the robot to move the welding torch toward a welding start position for the workpiece, and the control unit controls operation of the wire feeder to alternately perform a first operation of feeding the welding wire in the forward direction until the welding torch contacts the workpiece and a second operation of feeding the welding wire in the reverse direction when the welding torch reaches the welding start position, and the control unit calculates a vibration amount of the welding torch based on the amount of welding wire fed.

[0011] In the first aspect of the present invention, the vibration amount of the welding torch can be calculated based on the feed amount of the welding wire by alternately performing the first and second operations at the welding start position.

[0012] Specifically, when the feed rate of the welding wire is large, the vibration amount of the welding torch becomes large, and when the feed rate of the welding wire is small, the vibration amount of the welding torch becomes small.

[0013] This makes it possible to grasp the vibration of the welding torch immediately after it has stopped at the welding start position without providing a separate acceleration sensor or the like.

[0014] A second invention is an arc welding apparatus according to the first invention, wherein the control unit controls the operation of the robot so that the acceleration of the welding torch toward the welding start position is reduced when the vibration amount of the welding torch is greater than a predetermined threshold value.

[0015] In the second aspect of the present invention, the amount of vibration of the welding torch at the welding start position can be suppressed by reducing the acceleration of the welding torch moving toward the welding start position based on the amount of vibration of the welding torch.

[0016] A third invention is an arc welding method for supplying a welding wire from a welding torch to a workpiece to perform arc welding, comprising the steps of: moving the welding torch toward a welding start position of the workpiece; alternating between a first action of feeding the welding wire in a forward direction until it contacts the workpiece when the welding torch reaches the welding start position and a second action of feeding the welding wire in a reverse direction that has contacted the workpiece; and calculating a vibration amount of the welding torch based on the amount of welding wire fed.

[0017] In the third aspect of the present invention, the first operation and the second operation are alternately performed at the welding start position, so that the vibration amount of the welding torch can be calculated based on the feed amount of the welding wire. Effect of the Invention

[0018] According to the present invention, the vibration amount of the welding torch at the welding start position can be calculated. [Brief description of the drawings]

[0019] [Figure 1] 1 is a schematic configuration diagram of an arc welding device according to an embodiment of the present invention; [Diagram 2] FIG. 13 is a diagram showing a state in which the welding torch has been moved to a welding start position. [Diagram 3]FIG. 13 is a diagram showing a state in which the welding torch is vibrated in a direction approaching the workpiece. [Figure 4] FIG. 13 is a diagram showing a state in which the welding torch is vibrated in a direction away from the workpiece. [Diagram 5] FIG. 13 is a diagram showing a state in which the welding torch is vibrated in a direction approaching the workpiece again. [Figure 6] FIG. 13 is a diagram showing a state in which the welding torch is vibrated in a direction away from the workpiece again. [Figure 7] FIG. 13 is a diagram showing a state in which the vibration of the welding torch has converged. [Figure 8] FIG. 11 is a graph showing the relationship between elapsed time and the wire feed amount. [Figure 9] FIG. 11 is a graph showing the relationship between elapsed time and the height of the torch. [Figure 10] FIG. 11 is a graph showing the relationship between elapsed time and the vibration amount of a torch. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the following description of the preferred embodiment is merely illustrative in nature and is not intended to limit the present invention, its applications, or its uses.

[0021] 1, the arc welding device 1 welds the workpiece W by generating an arc between a welding wire 23, which is a consumable electrode, and the workpiece W. The workpiece W is made of, for example, mild steel or a material having a higher electrical resistance than mild steel (for example, stainless steel).

[0022] The arc welding apparatus 1 includes a welding unit 10 , a wire feeder 21 , a welding torch 22 , a robot 24 , and a setting unit 25 .

[0023] Based on a signal from control unit 14 of welding unit 10, wire feeder 21 feeds welding wire 23 toward workpiece W at a predetermined feed speed. Specifically, wire feeder 21 feeds welding wire 23 to welding torch 22. Welding torch 22 holds welding wire 23 so that welding wire 23 fed from wire feeder 21 and workpiece W face each other. Based on a signal from control unit 14, wire feeder 21 alternately feeds welding wire 23 in a forward direction toward workpiece W and in a reverse direction opposite to the forward feed.

[0024] Welding torch 22 holds welding wire 23 and supplies power to welding wire 23 to generate an arc between welding wire 23 and workpiece W. Specifically, welding torch 22 has a welding tip 22a. Welding tip 22a supplies power from welding unit 10 to welding wire 23.

[0025] Wire feeder 21 is provided with a feed speed detector (not shown) that detects the feed speed of welding wire 23. A detection signal indicating the feed speed of welding wire 23 detected by the feed speed detector is transmitted to controller 14.

[0026] The robot 24 has a plurality of joints. A welding torch 22 is attached to the tip of the robot 24. The robot 24 changes the position of the welding torch 22 with respect to the workpiece W.

[0027] Setting unit 25 is used to set welding conditions including a welding current and a welding voltage. Specifically, setting unit 25 sets a set welding current for performing welding, a set welding voltage for performing welding, a feed speed of welding wire 23, a type of shielding gas, a material of welding wire 23, a diameter of welding wire 23, a pulse welding period, a number of pulse outputs, etc.

[0028] Welding unit 10 includes a power conversion unit 11, a welding current detection unit 12, a welding voltage detection unit 13, and a control unit .

[0029] The power conversion unit 11 is electrically connected to the power source 100. The power conversion unit 11 generates a welding voltage V suitable for welding, using power supplied from the power source 100. The power conversion unit 11 is electrically connected to the welding wire 23 via the welding tip 22a of the welding torch 22. The power conversion unit 11 is electrically connected to the workpiece W. The power conversion unit 11 applies the welding voltage V between the welding wire 23 and the workpiece W, thereby causing a welding current I to flow through the welding wire 23 and the workpiece W.

[0030] The power conversion unit 11 includes a first rectification unit 101, a first switching unit 102, a transformer 103, a second rectification unit 104, a reactor 105, and a second switching unit 106.

[0031] The first rectifier 101 rectifies the output of the power source 100. The first switching unit 102 adjusts the output of the first rectifier 101 by switching operation. The transformer 103 converts the output of the first switching unit 102 into an output suitable for welding.

[0032] The second rectifier 104 rectifies the output of the transformer 103. The reactor 105 is connected in series with the second rectifier 104 and smoothes the output of the second rectifier 104. The second switching unit 106 adjusts the output of the reactor 105 by switching operation. The output of the second switching unit 106 is supplied to the welding wire 23 and the workpiece W via the welding tip 22a of the welding torch 22.

[0033] As a result, a welding voltage V is applied between the welding wire 23 and the workpiece W, and a welding current I flows through the welding wire 23 and the workpiece W.

[0034] Welding current detection unit 12 detects welding current I. Welding voltage detection unit 13 detects welding voltage V. A detection signal indicative of the welding current I detected by welding current detection unit 12 and a detection signal indicative of the welding voltage V detected by welding voltage detection unit 13 are transmitted to control unit 14.

[0035] Control unit 14 transmits signals between each part of welding unit 10 and devices external to welding unit 10. In the example shown in Fig. 1, the parts of welding unit 10 that transmit signals with control unit 14 are first switching unit 102, second switching unit 106, welding current detection unit 12, and welding voltage detection unit 13. The devices external to welding unit 10 that transmit signals with control unit 14 are wire feeder 21, robot 24, and setting unit 25.

[0036] Control unit 14 controls each part of welding unit 10 and devices external to welding unit 10 based on signals transmitted from each part of welding unit 10 and devices external to welding unit 10 .

[0037] Control unit 14 controls the operation of wire feeder 21 to change the feed speed of welding wire 23. Specifically, control unit 14 controls the feed speed of welding wire 23 in wire feeder 21 in accordance with the set current of welding current I set by setting unit 25. Here, the feed speed and welding current I are correlated with each other. More specifically, the average welding speed (also referred to as feed amount) as a moving average and the average welding current (also referred to as set current) which is the average current as a moving average are correlated with each other.

[0038] Control unit 14 controls first switching unit 102 and second switching unit 106 of power conversion unit 11, wire feeder 21, and robot 24 that holds welding torch 22. Control unit 14 moves welding torch 22 along the welding direction of workpiece W by providing current commands to motors (not shown) of each axis of robot 24.

[0039] The control unit 14 is configured with, for example, a processor and a memory electrically connected to the processor. The memory stores programs and information for operating the processor.

[0040] (Method of controlling arc welding device) Next, a description will be given of the operation of the arc welding apparatus 1. The arc welding apparatus 1 supplies a shielding gas from a gas supply port (not shown) to shield a welding point of the workpiece W from the outside air while supplying a current between the welding wire 23 and the workpiece W.

[0041] This generates an arc between the welding wire 23 and the workpiece W, and the heat of the arc melts the tip of the welding wire 23 and part of the workpiece W. The molten welding wire 23 turns into molten droplets that drip onto the workpiece W and form a molten pool together with the part of the workpiece W that has been melted by the heat of the arc.

[0042] The welding torch 22 moves along the welding direction of the workpiece W. As the welding torch 22 moves, a bead is formed on the workpiece W, and the workpiece W is welded.

[0043] <Welding torch vibration amount at welding start position> Incidentally, when welding torch 22 is moved from a predetermined position to the welding start position and then stopped, welding torch 22 vibrates at the welding start position.

[0044] At this time, the faster the movement speed of welding torch 22, the longer it takes for the vibration of welding torch 22 to converge at the welding start position. However, if arc welding is started before the vibration of welding torch 22 converges, there is a risk that welding quality cannot be ensured.

[0045] Furthermore, if there is a wait until the vibration of welding torch 22 subsides, the time until arc welding can be started will be longer, which will affect the tact time.

[0046] Therefore, in this embodiment, the vibration amount of welding torch 22 at the welding start position can be estimated.

[0047] Specifically, a case will be considered in which welding torch 22 is moved from a predetermined position toward welding start position P, as shown in Fig. 2. During the movement of welding torch 22, control is performed so that no welding current flows through welding wire 23 and workpiece W, thereby preventing an arc from being generated between welding wire 23 and workpiece W.

[0048] 2, before welding torch 22 starts to move, the tip of welding wire 23 is separated from workpiece W. Control unit 14 controls the operation of wire feeder 21 so as to perform a first operation of feeding welding wire 23 in the forward direction until it comes into contact with workpiece W while welding torch 22 is moving toward welding start position P.

[0049] Whether welding wire 23 is in contact with workpiece W can be determined by checking whether the voltage applied to welding wire 23 is 0 V (conductive state).

[0050] 2, at welding start position P, the height of welding torch 22 relative to workpiece W is set to be reference height H. At welding start position P, the tip of welding wire 23 is in contact with workpiece W, and the protrusion amount of welding wire 23 is H.

[0051] Here, when welding torch 22 is moved to welding start position P and then stopped, welding torch 22 at welding start position P vibrates.

[0052] In the example shown in Fig. 3, welding torch 22 vibrates in a direction approaching workpiece W. Control unit 14 controls the operation of wire feeder 21 to perform a second operation of feeding welding wire 23 in reverse, the welding wire 23 being in contact with workpiece W. The feed amount of welding wire 23 at this time is designated as D1. In the example shown in Fig. 3, by subtracting feed amount D1 from reference height H, it can be estimated that welding torch 22 has moved to a position at height H1 from workpiece W as welding torch 22 vibrates.

[0053] In the example shown in Fig. 4, welding torch 22 vibrates in a direction away from workpiece W. Control unit 14 controls the operation of wire feeder 21 to perform a first operation of feeding welding wire 23 in the forward direction until it contacts workpiece W. The feed amount of welding wire 23 at this time is designated as D2. In the example shown in Fig. 4, by adding feed amount D2 to reference height H, it can be estimated that welding torch 22 has moved to a position of height H2 from workpiece W as welding torch 22 vibrates.

[0054] In the example shown in Fig. 5, welding torch 22 is vibrating in a direction approaching workpiece W again. Control unit 14 controls the operation of wire feeder 21 to perform a second operation of feeding welding wire 23 in reverse, the welding wire 23 being in contact with workpiece W. The feed amount of welding wire 23 at this time is designated as D3. In the example shown in Fig. 5, by subtracting feed amount D3 from reference height H, it can be estimated that welding torch 22 has moved to a position of height H3 from workpiece W as welding torch 22 vibrates.

[0055] In the example shown in Fig. 6, welding torch 22 is vibrating again in a direction away from workpiece W. Control unit 14 controls the operation of wire feeder 21 to perform a first operation of feeding welding wire 23 in the forward direction until it contacts workpiece W. The feed amount of welding wire 23 at this time is set to D4. In the example shown in Fig. 6, by adding feed amount D4 to reference height H, it can be estimated that welding torch 22 has moved to a position of height H4 from workpiece W as welding torch 22 vibrates.

[0056] Thereafter, welding torch 22 continues to vibrate in a direction approaching workpiece W and a direction away from workpiece W. The feed rate of welding wire 23 gradually decreases as the vibration of welding torch 22 converges. Finally, welding torch 22 stops at the position of reference height H, and the feed rate of welding wire 23 becomes "0" (see FIG. 7).

[0057] In this manner, by alternately performing the first operation and the second operation at welding start position P, the vibration amount of welding torch 22 can be calculated based on the feed amount of welding wire 23.

[0058] 8 and 9, it can be seen that the greater the feed rate of welding wire 23, the greater the deviation of the height position of welding torch 22 from reference height H. The amount of vibration of welding torch 22 can be represented by the amount of change in the height position of welding torch 22 with respect to reference height H.

[0059] Control unit 14 calculates vibration amounts A1-A4 of welding torch 22 based on feed rates D1-D4 of welding wire 23 (see FIG. 10). Vibration amounts A1-A4 of welding torch 22 are proportional to the absolute values ​​of feed rates D1-D4 of welding wire 23.

[0060] That is, when the feed rate of welding wire 23 is large, the vibration amount of welding torch 22 becomes large, and when the feed rate of welding wire 23 is small, the vibration amount of welding torch 22 becomes small.

[0061] This makes it possible to grasp the vibration of welding torch 22 immediately after it has stopped at welding start position P without providing a separate acceleration sensor or the like.

[0062] Control unit 14 determines whether the vibration amount of welding torch 22 is greater than a predetermined threshold value S (see FIG. 10). Threshold value S is appropriately set taking into consideration the time it takes for the vibration of welding torch 22 to converge immediately after it has stopped at welding start position P.

[0063] 10, the largest vibration amount A1 of welding torch 22 is larger than threshold value S. In this case, it is determined that the vibration of welding torch 22 immediately after it stops at welding start position P is large.

[0064] When the vibration amount of welding torch 22 is greater than a predetermined threshold value S, control unit 14 controls the operation of robot 24 to reduce the acceleration of welding torch 22 toward welding start position P. This makes it possible to suppress the vibration amount of welding torch 22 at welding start position P. [Industrial Applicability]

[0065] INDUSTRIAL APPLICABILITY As described above, the present invention provides the highly practical effect of being able to calculate the vibration amount of the welding torch at the welding start position, and is therefore extremely useful and has high industrial applicability. [Explanation of symbols]

[0066] 1 Arc welding equipment 14 Control section 21 Wire feed section 22 Welding torch 23 Welding Wire 24 Robot P Welding start position S Threshold W work

Claims

1. An arc welding apparatus that supplies a welding wire to a workpiece to perform arc welding, a wire feeder that feeds the welding wire; a welding torch that holds the welding wire and supplies power to the welding wire to generate an arc between the welding wire and the workpiece; A robot for changing a position of the welding torch relative to the workpiece; a control unit that controls the operation of the wire feeder and the robot, The control unit is Controlling the operation of the robot so as to move the welding torch toward a welding start position of the workpiece; When the welding torch reaches the welding start position, an operation of the wire feeder is controlled so as to alternately perform a first operation of feeding the welding wire in a forward direction until the welding wire comes into contact with the workpiece and a second operation of feeding the welding wire in a reverse direction after the welding torch has come into contact with the workpiece; A vibration amount of the welding torch is calculated based on the feed amount of the welding wire. Arc welding equipment.

2. 2. The arc welding apparatus of claim 1, The control unit controls the operation of the robot so that the acceleration of the welding torch toward the welding start position is reduced when a vibration amount of the welding torch is greater than a predetermined threshold value. Arc welding equipment.

3. 1. An arc welding method for supplying a welding wire from a welding torch to a workpiece to perform arc welding, comprising: moving the welding torch toward a welding start position of the workpiece; a step of alternately performing a first operation of feeding the welding wire in a forward direction until the welding wire comes into contact with the workpiece when the welding torch reaches a welding start position and a second operation of feeding the welding wire in a reverse direction after the welding torch has come into contact with the workpiece; and calculating a vibration amount of the welding torch based on the feed amount of the welding wire. Arc welding method.

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