Arc-welding device and arc-welding method

Abstract

To allow proper setting of a protruding length of a welding wire in a welding start position.SOLUTION: 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 during movement of a welding torch 22 and a second operation in which the welding wire 23 in contact with the workpiece W is moved rearward. The wire feeding part 21 moves the welding wire 23 rearward by a predetermined distance from a state that the welding wire 23 is in contact with the workpiece W when the welding torch 22 reaches a welding start position.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] Here, the amount of protrusion of the welding wire from the welding tip must be appropriately set since it affects the welding quality and tact time.

[0006] Specifically, if the welding wire is extended too far at the welding start position, the tip of the welding wire may come into contact with the workpiece before arc welding begins, which may result in a problem such as a touch start.

[0007] On the other hand, if the extension length of the welding wire at the welding start position is too short, it may take a long time for the tip of the welding wire to come into contact with the workpiece when arc welding starts, which may reduce productivity.

[0008] 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 appropriately set the extension amount of the welding wire at the welding start position. [Means for solving the problem]

[0009] 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 feeding unit 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 workpiece and the welding torch; a robot that changes a position of the welding torch relative to the workpiece; and a control unit that controls operation of the wire feeding unit 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, controls operation of the wire feeding unit to alternately perform a first operation of feeding the welding wire in the forward direction until it contacts the workpiece and a second operation of feeding the welding wire in the reverse direction after contacting the workpiece while the welding torch is moving, and controls operation of the wire feeding unit to feed the welding wire in the reverse direction a predetermined amount from a state in which the welding wire is in contact with the workpiece when the welding torch reaches the welding start position.

[0010] In the first invention, by alternately performing the first and second operations while the welding torch is moving, the distance between the tip of the welding wire and the workpiece can be determined based on the amount of welding wire fed.

[0011] Then, at the welding start position, by feeding the welding wire back a predetermined amount from a state in which the welding wire is in contact with the workpiece, the protrusion amount of the welding wire can be appropriately set.

[0012] A second 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 operation of feeding the welding wire in a forward direction until it contacts the workpiece while the welding torch is moving and a second operation of feeding the welding wire in a reverse direction that has contacted the workpiece; and, when the welding torch reaches the welding start position, feeding the welding wire in a reverse direction by a predetermined amount from a state in which the welding wire is in contact with the workpiece.

[0013] In the second invention, by alternately performing the first and second operations while the welding torch is moving, the distance between the tip of the welding wire and the workpiece can be determined based on the amount of welding wire fed.

[0014] Then, at the welding start position, by feeding the welding wire back a predetermined amount from a state in which the welding wire is in contact with the workpiece, the protrusion amount of the welding wire can be appropriately set. Effect of the Invention

[0015] According to the present invention, the extension amount of the welding wire at the welding start position can be appropriately set. [Brief description of the drawings]

[0016] [Figure 1] 1 is a schematic configuration diagram of an arc welding device according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a diagram showing a state in which the welding torch is at position P1. [Diagram 3] FIG. 13 is a diagram showing a state in which the welding torch has been moved to position P2. [Figure 4] FIG. 13 is a diagram showing a state in which the welding torch has been moved to position P3. [Diagram 5] FIG. 13 is a diagram showing a state in which the welding torch has been moved to position P4. [Figure 6] FIG. 13 is a diagram showing a state in which the welding torch has been moved to a position P5. [Figure 7]13 is a diagram showing a state in which the welding torch has been moved to a welding start position P6. FIG. [Figure 8] 13 is a diagram showing a state in which the welding wire is fed backward by a predetermined amount at a welding start position P6. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] 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.

[0018] 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).

[0019] 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 .

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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 .

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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 .

[0034] 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.

[0035] 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.

[0036] 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.

[0037] (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.

[0038] 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.

[0039] 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.

[0040] <Welding wire extension at welding start position> Incidentally, the amount of protrusion of the welding wire 23 from the welding tip 22a must be appropriately set since it affects the welding quality and tact time.

[0041] Specifically, if the extension amount of the welding wire 23 is too long at the welding start position, the tip of the welding wire 23 may come into contact with the workpiece W before the start of arc welding, which may cause a problem such as a touch start. In addition, the welding wire 23 may come into contact with the workpiece W before the supply speed of the welding wire 23 reaches the target speed, which may deteriorate the welding quality.

[0042] On the other hand, if the extension amount of the welding wire 23 at the welding start position is too short, the welding quality can be ensured, but the time until the tip of the welding wire 23 comes into contact with the workpiece W at the start of arc welding will be long, which may result in poor productivity.

[0043] Here, the extension amount of welding wire 23 is set to be a constant length at multiple welding start positions. However, the extension amount of welding wire 23 may vary at the welding start position due to, for example, the operation of moving welding torch 22 from the previous welding end position to the next welding start position, or the amount of play caused by bending of welding wire 23.

[0044] Therefore, in this embodiment, the extension amount of the welding wire 23 at the welding start position can be appropriately set.

[0045] Specifically, a case will be considered in which welding torch 22 is moved from position P1 toward welding start position P6 as shown in Fig. 2. Note that while welding torch 22 is moving from position P1 to welding start position P6, 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.

[0046] 2, at position P1, 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 from position P1 toward position P2.

[0047] 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).

[0048] 3, at position P2, the tip end of welding wire 23 is in contact with workpiece W. Controller 14 controls the operation of wire feeder 21 to perform a second operation of feeding welding wire 23 in contact with workpiece W in the reverse direction while welding torch 22 is moving from position P2 toward position P3.

[0049] 4, at position P3, the tip of welding wire 23 is separated 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 welding wire 23 comes into contact with workpiece W while welding torch 22 is moving from position P3 toward position P4.

[0050] 5, at position P4, the tip end of welding wire 23 is in contact with workpiece W. Controller 14 controls the operation of wire feeder 21 to perform a second operation of feeding welding wire 23 in contact with workpiece W in the reverse direction while welding torch 22 is moving from position P4 toward position P5.

[0051] 6, at position P5, 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 from position P5 toward welding start position P6.

[0052] In this way, by alternately performing the first and second operations while moving the welding torch 22 toward the welding start position P6 of the workpiece W, the distance between the tip of the welding wire 23 and the workpiece W can be determined based on the amount of welding wire 23 being fed.

[0053] 7, when welding torch 22 reaches welding start position P6, the tip of welding wire 23 is in contact with workpiece W. Control unit 14 controls the operation of wire feeder 21 so as to feed welding wire 23 backward by a predetermined amount H (see FIG. 8) from the state in which welding wire 23 is in contact with workpiece W at welding start position P6.

[0054] This makes it possible to appropriately set the protruding amount of the welding wire 23, as shown in FIG.

[0055] 8, the distance between the tip of welding torch 22 and workpiece W is set to 15 mm. The distance between the tip of welding wire 23 and workpiece W, which may cause a malfunction such as a touch start or may cause welding wire 23 to come into contact with workpiece W before the supply speed of welding wire 23 reaches a target speed, is set to about 1 mm. The distance between the tip of welding wire 23 and workpiece W, which may cause a long time until the tip of welding wire 23 comes into contact with workpiece W and may result in poor productivity, is set to about 5 mm.

[0056] In this embodiment, the extension amount of the welding wire 23 is set so that the distance between the tip of the welding wire 23 and the workpiece W is about 2 to 3 mm, thereby preventing problems such as touch start and improving the tact time. [Industrial Applicability]

[0057] INDUSTRIAL APPLICABILITY As described above, the present invention provides the highly practical effect of being able to appropriately set the extension amount of the welding wire at the welding start position, and is therefore extremely useful and has high industrial applicability. [Explanation of symbols]

[0058] 1 Arc welding equipment 14 Control section 21 Wire feed section 22 Welding torch 23 Welding Wire 24 Robot Double 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; During the movement of the welding torch, 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 wire has come into contact with the workpiece; When the welding torch reaches the welding start position, the operation of the wire feeder is controlled so that the welding wire is fed backward by a predetermined amount from a state in which the welding wire is in contact with the workpiece. Arc welding equipment.

2. 1. An arc welding method for supplying a welding wire from a welding torch to a workpiece to perform arc welding, comprising: moving a 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 during movement of the welding torch and a second operation of feeding the welding wire in a reverse direction after the welding wire has come into contact with the workpiece; and when the welding torch reaches the welding start position, feeding the welding wire back by a predetermined amount from a state in which the welding wire is in contact with the workpiece. Arc welding method.

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