How to set welding conditions

Abstract

To allow changes in welding conditions according to the number of turns of a torch cable.SOLUTION: A first operation of reversely feeding a welding wire 21 and then normally feeding it, or a second operation of normally feeding the welding wire 21 and then reversely feeding it, is performed. After the start of normal feeding of the first operation, or after the start of reverse feeding of the second operation, a lapsed time Tn until a current value of a feed motor 22 reaches a prescribed threshold or more is acquired. On the basis of the lapsed time Tn, welding conditions of a welding device 1 are changed.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to a method for setting welding conditions. [Background technology]

[0002] Patent Document 1 discloses an arc start control method in which an initial high-speed feed time and an initial high-speed feed speed are set according to the length of a welding torch, and the welding wire is fed at an initial high-speed feed speed faster than a steady feed speed from the start of re-feeding until the initial high-speed feed time, thereby shortening the feed delay time due to play. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2003-181641 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, while the invention of Patent Document 1 takes into consideration the play of the welding wire depending on the length of the welding torch, it does not take into consideration the play of the welding wire depending on the number of turns of the torch cable.

[0005] Specifically, when the torch cable is wound in turns, the welding wire is routed along the inner circumferential surface of the turn portion of the torch cable at the end of reverse feeding, whereas the welding wire is routed along the outer circumferential surface of the turn portion of the torch cable at the end of forward feeding.

[0006] Therefore, when forward and reverse feed operations are alternately repeated, play occurs in the welding wire within the torch cable, causing the amount of welding wire fed to become unstable and deteriorating welding quality.

[0007] The present invention has been made in view of the above-mentioned points, and an object of the present invention is to make it possible to change welding conditions according to the number of turns of the torch cable. [Means for solving the problem]

[0008] A first invention is a method for setting welding conditions in a welding apparatus including a welding torch, a torch cable connected to the welding torch for guiding a welding wire, and a feed motor for feeding the welding wire through the torch cable, the method including the steps of: performing a first operation of feeding the welding wire in a reverse direction and then feeding it in a forward direction, or a second operation of feeding the welding wire in a forward direction and then feeding it in a reverse direction; acquiring an elapsed time from the start of the forward feed of the first operation or the start of the reverse feed of the second operation until a current value of the feed motor becomes equal to or greater than a predetermined threshold; and changing the welding conditions of the welding apparatus based on the elapsed time.

[0009] In the first aspect of the present invention, a first operation is performed in which the welding wire is fed in the reverse direction and then fed in the forward direction, or a second operation is performed in which the welding wire is fed in the forward direction and then fed in the reverse direction. The elapsed time from the start of the forward feed of the first operation or the start of the reverse feed of the second operation until the current value of the feed motor becomes equal to or greater than a predetermined threshold is obtained. The welding conditions of the welding device are changed based on the elapsed time.

[0010] This makes it possible to estimate the number of turns of the torch cable based on the elapsed time and change the welding conditions according to the number of turns of the torch cable.

[0011] Specifically, when the torch cable is not wound (number of turns is 0), after the forward feed of the first operation starts or the reverse feed of the second operation starts, the motor current has a waveform similar to that of the feed command, so that the feed motor can be immediately operated at the commanded feed speed.

[0012] On the other hand, when the torch cable is wound with turns (for example, one turn), there is slack in the welding wire inside the torch cable. This reduces the feed load of the feed motor, and there is a period during which the current value of the feed motor is smaller than the target current value. This period tends to be longer as the number of turns of the torch cable increases.

[0013] Therefore, in the present invention, the elapsed time until the current value of the feed motor becomes equal to or greater than a predetermined threshold is obtained, and the number of turns of the torch cable is estimated according to the length of the elapsed time.

[0014] In a second aspect of the present invention, in the first aspect of the present invention, in the step of changing the welding conditions, a feed amount of the welding wire is changed.

[0015] In the second invention, the welding conditions can be changed by changing the feed rate of the welding wire.

[0016] A third invention is based on the first or second invention, wherein in the step of changing the welding conditions, the feed amount of the welding wire is increased as the elapsed time is longer.

[0017] In the third invention, it is estimated that the number of turns of the torch cable increases as the elapsed time increases, and the welding conditions are changed so that the amount of welding wire fed is increased. This makes it possible to stabilize the amount of welding wire fed and improve the welding quality.

[0018] A fourth invention is any one of the first to third inventions, wherein data indicating a relationship between the elapsed time and the amount of welding wire fed is stored in advance in a table, and in the step of changing the welding conditions, the amount of welding wire fed corresponding to the elapsed time actually obtained is read from the table, and the amount of welding wire fed is changed.

[0019] In the fourth aspect of the present invention, the welding conditions can be automatically changed by reading out from the table the welding wire feed rate that corresponds to the actually acquired elapsed time. Effect of the Invention

[0020] According to the present invention, the welding conditions can be changed according to the number of turns of the torch cable. [Brief description of the drawings]

[0021] [Figure 1] 1 is a diagram showing an overall configuration of a welding device according to an embodiment of the present invention; [Diagram 2] FIG. 13 is a diagram for explaining the position of the welding wire in the torch cable wound one turn at the end of reverse feeding. [Diagram 3] FIG. 2 is a diagram for explaining the position of the welding wire in a torch cable wound one turn at the end of forward feeding. [Figure 4] FIG. 13 is a diagram for explaining the position of the welding wire when reverse feeding is completed in a torch cable wound with 0.5 turns. [Diagram 5] FIG. 13 is a diagram for explaining the position of the welding wire in a torch cable wound with 0.5 turns at the end of forward feeding. [Figure 6] FIG. 11 is a graph showing the change in motor current over time when the torch cable is wound in turns. [Figure 7] FIG. 4 is a graph showing a change in differential motor current over time. [Figure 8] FIG. 11 is a graph comparing changes in motor current over time when the number of turns of the torch cable is changed. [Figure 9] FIG. 11 is a flowchart showing a procedure for changing welding conditions. [Figure 10] FIG. 11 is a graph illustrating elapsed time in a welding device according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] 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.

[0023] 1, the welding device 1 includes a welding torch 10, a torch cable 15, a feeder 20, a gas supply unit 25, and a power supply unit 30. The welding device 1 performs arc welding on a workpiece W.

[0024] The welding torch 10 is connected to a wire feeder 20 via a torch cable 15. The welding torch 10 supplies the welding wire 21 fed from the wire feeder 20 to the workpiece W.

[0025] Torch cable 15 guides welding wire 21 toward welding torch 10. A gas hose (not shown) is provided inside torch cable 15. The gas hose of torch cable 15 is connected to gas hose 26 of gas supply unit 25.

[0026] The gas supply unit 25 is connected to the feeder 20 via a gas hose 26. The shielding gas supplied from the gas supply unit 25 flows through the inside of the gas hose of the torch cable 15 and is sprayed from the tip of the welding torch 10 toward the workpiece W.

[0027] The feeder 20 has a welding wire 21 and a feed motor 22. The welding wire 21 is wound around a wire reel (not shown). The feed motor 22 feeds the welding wire 21 by rotating a feed roller (not shown). The feeder 20 sends a signal indicating a motor current value of the feed motor 22 to the power supply 30 via a motor current signal line 5.

[0028] The feeder 20 switches between a forward feed operation and a reverse feed operation by changing the rotation direction of the feed motor 22. In the forward feed operation, the welding wire 21 is fed from the feeder 20 toward the welding torch 10. In the reverse feed operation, the welding wire 21 is drawn from the welding torch 10 toward the feeder 20.

[0029] The power supply device 30 includes a power supply unit 31, a welding control unit 32, a calculation unit 33, a storage unit 34, and a display unit 35.

[0030] The power supply unit 31 supplies power to the feeder 20 via the power cable 7. The power supply unit 31 applies a voltage to the workpiece W via the base metal cable 8. A positive voltage is applied to the welding wire 21. A negative voltage is applied to the workpiece W. As a result, the welding device 1 generates an arc discharge between the tip of the welding wire 21 and the workpiece W, and performs arc welding.

[0031] The welding control unit 32 controls the operation of the feeding device 20. The welding control unit 32 issues a feeding command to the feeding device 20 via the control signal line 6. The feeding device 20 controls the feeding motor 22 to a constant speed at the commanded speed, thereby feeding the welding wire 21.

[0032] The calculation unit 33 receives a signal indicating the motor current value sent from the feeding device 20 via the motor current signal line 5. As will be described in detail later, the calculation unit 33 estimates the number of turns of the torch cable 15 based on the first current value Ia, the second current value Ic, and the elapsed time Tn detected during the feeding of the welding wire 21. The calculation result of the calculation unit 33 is stored in the memory unit 34.

[0033] The memory unit 34 stores data indicating various welding conditions including a welding current value, a welding voltage value, etc. A table indicating the relationship between the number of turns of the torch cable 15 and the optimal feed amount of the welding wire 21 is stored in advance in the memory unit 34. The calculation unit 33 reads out various welding conditions from the memory unit 34.

[0034] The display unit 35 displays predetermined information. For example, the display unit 35 displays a welding current value and a welding voltage value during arc welding.

[0035] Incidentally, when the overall length of torch cable 15 is long, torch cable 15 may be wound in turns so as not to interfere with the welding work. When torch cable 15 is wound in turns, the overall length of welding wire 21 in torch cable 15 differs between the end of reverse feed and the end of forward feed.

[0036] Specifically, a case where torch cable 15 is wound one turn will be considered as shown in Fig. 2. At the end of reverse feeding in Fig. 2, welding wire 21 is routed along the inner circumferential surface of the turn portion of torch cable 15. At the end of forward feeding in Fig. 3, welding wire 21 is routed along the outer circumferential surface of the turn portion of torch cable 15.

[0037] Here, the total length of welding wire 21 in torch cable 15 is shorter at the end of reverse feed than at the end of forward feed. When forward feed is started from the state at the end of reverse feed (see FIG. 2), welding wire 21 does not protrude from welding torch 10 until it reaches the state at the end of forward feed (see FIG. 3).

[0038] Also, as shown in Fig. 4, a case where torch cable 15 is wound half a turn, that is, 0.5 turns, will be considered. At the end of reverse feeding in Fig. 4, welding wire 21 is routed along the inner circumferential surface of the turn portion of torch cable 15. At the end of forward feeding in Fig. 5, welding wire 21 is routed along the outer circumferential surface of the turn portion of torch cable 15.

[0039] Here, the greater the number of turns of torch cable 15, the greater the play of welding wire 21 within torch cable 15. In other words, when torch cable 15 is wound one turn, welding wire 21 has more play than when torch cable 15 is wound 0.5 turn.

[0040] Therefore, if welding conditions such as the wire feed speed are kept constant regardless of the number of turns of torch cable 15, the feed rate of welding wire 21 becomes unstable, which may cause unstable arc welding or welding defects.

[0041] Therefore, in this embodiment, the welding conditions can be changed according to the number of turns of the torch cable 15.

[0042] <Determining the number of turns in a torch cable> When determining the number of turns of torch cable 15, first, a first operation is performed in which welding wire 21 is fed in the reverse direction and then forward by feed motor 22. Note that a second operation may be performed in which welding wire 21 is fed in the reverse direction and then forward, but the following describes the case in which the first operation is performed.

[0043] Fig. 6 is a graph showing the change in motor current over time when torch cable 15 is wound in one turn. Note that the graph shown in Fig. 6 assumes that torch cable 15 is bent one turn with a diameter of φ600 mm.

[0044] 6, the point in time when feed motor 22 starts a forward feed operation after performing a reverse feed operation is set to 0. After the forward feed operation starts, a current is applied to feed motor 22 so that welding wire 21 is fed at a constant speed.

[0045] A signal indicating the current value applied to the feed motor 22 is sent to the power supply device 30 via the motor current signal line 5. The calculation unit 33 calculates the change in the motor current over time. The calculation unit 33 determines that the increase in the torque of the feed motor 22 has become equal to or less than a predetermined value at a first time point a when the change in the motor current becomes constant.

[0046] For example, as shown in Fig. 7, when the change in motor current per unit time (differential motor current) becomes equal to or less than a predetermined threshold, it is determined that the increase in torque of the feed motor 22 becomes equal to or less than a predetermined value. After the start of the forward feed operation of the feed motor 22, the period up to the first point a is a transitional period until an arbitrary feed speed is reached.

[0047] The feed device 20 detects a first current value Ia flowing through the feed motor 22 at a first time point a.

[0048] 6 and 7, the calculation unit 33 determines that the increase in the torque of the feed motor 22 becomes equal to or greater than a predetermined value at a second time point b when the motor current starts to increase after the first time point a has elapsed. In the example shown in Fig. 6 and 7, the slope of the motor current, that is, the current value at the second time point b when the differential motor current changes suddenly, is set as the predetermined threshold value.

[0049] The calculation unit 33 acquires the elapsed time Tn from the start of forward feeding in the first operation until the current value of the feed motor 22 becomes equal to or greater than a predetermined threshold value. In the example shown in Fig. 6, the calculation unit 33 acquires the elapsed time Tn from the start of the forward feeding operation until the second point b.

[0050] After the second point b has passed, at a third point c when welding wire 21 protrudes from the tip of welding torch 10, feeding device 20 detects second current value Ic flowing through feeding motor 22.

[0051] After second point b, until third point c is reached, the feed speed of welding wire 21 gradually increases at the tip of welding torch 10. During the period from second point b to third point c, welding wire 21 starts to protrude from the tip of welding torch 10, and the wire feed speed at the tip of welding torch 10 approaches the command feed speed (the feed speed of feed motor 22).

[0052] At third point in time c, the commanded feed speed coincides with the wire feed speed at the tip of welding torch 10. After third point in time c has passed, the feed speed of welding wire 21 maintains the feed speed command value given to feeder 20.

[0053] 6, the reason for the existence of bending points such as first time point a and second time point b is that, as a result of feed motor 22 performing a reverse feed operation and then a forward feed operation, there is play before welding wire 21 protrudes from the tip of welding torch 10. In other words, after feed motor 22 starts its forward feed operation, welding wire 21 does not protrude from the tip of welding torch 10 until second time point b, and this period is a period in which the play is absorbed in torch cable 15.

[0054] Therefore, as shown by the dotted line in FIG. 6, if the feed motor 22 does not perform the reverse feed operation, the motor current will increase to the second current value Ic without bending at the first time point a and the second time point b.

[0055] Fig. 8 is a graph comparing the time change of the motor current when the number of turns of the torch cable is changed. As shown in Fig. 8, when the torch cable 15 is not wound with turns (the number of turns is 0), there is no bending point.

[0056] On the other hand, when comparing the case where torch cable 15 is wound 1 turn with the case where it is wound 0.5 turns, the elapsed time T1 when wound 1 turn is longer than the elapsed time T0.5 when wound 0.5 turns. In other words, the elapsed time Tn tends to be longer as the number of turns of torch cable 15 increases.

[0057] Therefore, by acquiring the elapsed time Tn, the number of turns of the torch cable 15 can be estimated.

[0058] <How to set welding conditions> As shown in FIG. 9, in step S11, welding device 1 is powered on to prepare for welding.

[0059] In step S12, the feeder 20 measures the elapsed time Tn of the slack absorption period of the welding wire 21 by feeding the welding wire 21 in the reverse direction and then in the forward direction.

[0060] In step S13, the calculation unit 33 estimates the number of turns of the torch cable 15 based on the elapsed time Tn.

[0061] In step S14, the calculation unit 33 reads out from the table in the storage unit 34 the feed rate of the welding wire 21 that corresponds to the actually acquired elapsed time Tn, and changes the welding conditions.

[0062] Specifically, when torch cable 15 is wound for 1 turn, the feed rate of welding wire 21 is set to be greater than when torch cable 15 is wound for 0.5 turns. For example, the average feed rate of welding wire 21 is changed by about 1 m / min for every 0.5 turns.

[0063] In step S15, the welding device 1 starts welding under the changed welding conditions, and then ends the process.

[0064] Other Embodiments The above embodiment may be configured as follows.

[0065] In this embodiment, the current value at the second point b when the differential motor current changes suddenly is set as the threshold value, and the elapsed time Tn from the point when the forward feed operation is started after the welding wire 21 is fed in reverse to the second point b is acquired, but the present invention is not limited to this embodiment.

[0066] For example, as shown in Fig. 10, the second current value Ic at the third time point c may be used as a reference, and the value obtained by multiplying the second current value Ic by a predetermined coefficient α may be used as the threshold value. In this case, the elapsed time Tn from the time when the forward feeding operation is started after the welding wire 21 is fed in the reverse direction to the time when the current value of the feeding motor 22 becomes equal to or greater than the threshold value may be obtained.

[0067] For example, by setting α=0.8 and a current value that is 80% of the second current value Ic as the threshold, the elapsed time Tn at the point when the current value of the feed motor 22 becomes equal to or greater than Ic×α can be obtained. Note that the value of the coefficient α is merely an example, and may be set appropriately depending on the configuration of each device and the number of turns that the torch cable 15 can make.

[0068] Further, the present embodiment is not limited to active welding in which welding is performed by alternately repeating reverse and forward feeding of welding wire 21, but includes welding in which welding wire 21 is fed at a constant speed. [Industrial Applicability]

[0069] INDUSTRIAL APPLICABILITY As described above, the present invention provides the highly practical effect of being able to change welding conditions depending on the number of turns of the torch cable, and is therefore extremely useful and has high industrial applicability. [Explanation of symbols]

[0070] 1 Welding equipment 10. Welding Torch 15 Torch Cable 20 Feeding device 21 Welding Wire 22 Feed motor 33 Arithmetic section 34 Storage section Tn Elapsed time

Claims

1. 1. A method for setting welding conditions in a welding apparatus including a welding torch, a torch cable connected to the welding torch and guiding a welding wire, and a feed motor that feeds the welding wire through the torch cable, comprising: performing a first operation of feeding the welding wire in a reverse direction and then feeding it in a forward direction, or a second operation of feeding the welding wire in a forward direction and then feeding it in a reverse direction; acquiring an elapsed time from a start of forward feeding of the first operation or a start of reverse feeding of the second operation until a current value of the feed motor becomes equal to or greater than a predetermined threshold; and changing a welding condition of the welding device based on the elapsed time. How to set welding conditions.

2. In claim 1, In the step of changing the welding conditions, the feed amount of the welding wire is changed. How to set welding conditions.

3. In claim 1 or 2, In the step of changing the welding conditions, the amount of the welding wire fed is increased as the elapsed time is longer. How to set welding conditions.

4. In any one of claims 1 to 3, data indicating a relationship between the elapsed time and the feed amount of the welding wire is stored in a table in advance; In the step of changing the welding conditions, the feed amount of the welding wire corresponding to the actually acquired elapsed time is read from the table, and the feed amount of the welding wire is changed. How to set welding conditions.

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