JP4847292B2 - Start synchronous arc welding method - Google Patents

Description

  The present invention relates to a start-synchronized arc welding method for using two welding torches for two welding points and synchronizing welding at the same time to start welding.

  2. Description of the Related Art Conventionally, a start-synchronized arc welding method is used in which two welding torches are used for two welding locations, and the welding start timing is synchronized and welded simultaneously. For example, when there are two symmetrical welding locations in one work, welding quality can be improved by welding the two locations simultaneously in consideration of thermal deformation during welding. In addition, when the workpiece is fixed to the rotating jig and two locations are welded simultaneously using two welding torches, it is necessary to synchronize the welding start of both welding torches and the rotation start of the rotating jig. Hereinafter, the prior art in the case of implementing the start synchronous arc welding method in a welding apparatus using two robots will be described.

  FIG. 4 is a configuration diagram of a welding apparatus that welds two locations simultaneously using two robots. Hereinafter, each configuration will be described with reference to FIG.

  The robot controller RC outputs a first motion control signal Mc1, a second motion control signal Mc2 and an external axis control signal Pc for controlling the motion of two robots RM1 and RM2 and a rotating jig PT which will be described later. Further, the robot controller RC transmits / receives a first welding control signal Wc1 and a first arc generation signal Ac1 to / from the first welding power source PS1, and also transmits a second welding control signal Wc2 to / from the second welding power source PS2. The second arc generation signal Ac2 is transmitted and received.

  The first welding power source PS1 receives the first welding control signal Wc1 from the robot controller RC, transmits the first arc generation signal Ac1, and controls the first feeding motor M1 to rotate. The signal Fct1 is output and the first welding voltage Vw1 and the first welding current Iw1 are output. The second welding power source PS2 receives the second welding control signal Wc2 from the robot controller RC, transmits the second arc generation signal Ac2, and controls the second feeding motor M2 to rotate. The signal Fct2 is output, and the second welding voltage Vw2 and the second welding current Iw2 are output. The first and second welding control signals Wc1 and Wc2 include a start signal, a current setting signal (feeding speed setting signal), a voltage setting signal, a current waveform parameter signal, and the like (not shown). The current waveform parameter signal is a signal for setting the waveform of the welding current during the short-circuit period in CO2 / MAG welding, and a signal for setting the waveform of the pulse current in pulse arc welding. The first and second arc generation signals Ac1 and Ac2 are signals for determining that an arc has occurred at the start of welding and notifying the robot controller RC.

  The first feeding motor M1 feeds the first welding wire 11 through the first welding torch 41 at the first feeding speed Fw1, and the first arc 31 is interposed between the first welding wire 11 and the workpiece 2. Occurs and welding takes place. The second feeding motor M2 feeds the second welding wire 12 through the second welding torch 42 at the second feeding speed Fw2, and the second arc 32 is generated between the second welding wire 12 and the workpiece 2. Occurs and welding takes place. The rotating jig PT fixes the workpiece 2 thereon, and is rotationally controlled by the external axis control signal Pc.

  In the figure, one workpiece 2 is placed on the rotating jig PT, and two locations are welded simultaneously using a first welding torch 41 and a second welding torch 42. Therefore, in order to perform this welding, it is necessary to synchronize the welding start of both welding torches 41 and 42 and the rotation start of rotating jig PT.

[Prior art 1]
FIG. 5 is a timing chart when the start synchronous arc welding method of the prior art 1 is performed in the above-described welding apparatus. 1A shows a first wire-workpiece distance Lw1 which is a distance between the tip of the first welding wire 11 and the work 2, FIG. 1B shows a first welding current Iw1, and FIG. Indicates the first feed speed Fw1, FIG. 4D shows the first arc generation signal Ac1, and FIG. 2E shows the distance between the tip of the second welding wire 12 and the workpiece 2. The distance Lw2 is shown, (F) shows the second welding current Iw2, (G) shows the second feed speed Fw2, and (H) shows the second arc generation signal Ac2. The first feed speed Fw1 is set by a first feed speed setting signal included in the first welding control signal Wc1, and the second feed speed Fw2 is a second feed speed included in the second welding control signal Wc2. It is set by the feed speed setting signal. Hereinafter, a description will be given with reference to FIG.

  At time t1, the first robot RM1 and the second robot RM2 reach their welding start positions. The robot that has reached first waits until another robot arrives. When a start signal (not shown) is input to both welding power sources PS1 and PS2 at time t1, the first welding wire 11 is fed at the first slow-down speed Fi1, as shown in FIG. As shown in FIG. 5G, the second welding wire 12 is fed at the second slowdown speed Fi2. Therefore, the first wire-workpiece distance Lw1 is gradually shortened as shown in FIG. 5A, and the second wire-workpiece distance Lw2 is gradually shortened as shown in FIG. Here, since the wire burn-up height at the end of the previous welding varies, the wire protrusion length varies. As a result, there is a difference between the first wire-workpiece distance Lw1 and the second wire-workpiece distance Lw2 at time t1. Since both the slow-down speeds Fi1 and Fi2, which are the feeding speeds until the welding wire comes into contact with the work, are set to very slow speeds, the time difference (time) t2 and t3) will occur.

  At time t2, when the first welding wire 11 comes into contact with the workpiece 2 and the first wire-workpiece distance Lw1 becomes zero as shown in FIG. One arc 31 is generated and the first welding current Iw1 is energized. As shown in FIG. 4D, since the first arc 31 is generated at time t2, the first arc generation signal Ac1 is transmitted to the robot controller RC. In response to this, the first feed speed setting signal is switched from the first slow-down speed set value to the first steady feed speed set value. Therefore, as shown in FIG. Fw1 changes to the first steady feeding speed Fc1. At this time (time t2), as shown in FIG. 5H, since the second arc generation signal Ac2 has not been transmitted, both the robots RM1 and RM2 remain stopped at the welding start position.

  At time t3, the second welding wire 12 is fed at the second slow-down speed Fi2 as shown in FIG. 5G, and the second welding wire 12 is delayed as shown in FIG. 2, the second wire-workpiece distance Lw2 becomes zero, and the second arc 32 is generated and the second welding current Iw2 is energized as shown in FIG. For this purpose, the second arc generation signal Ac2 is transmitted to the robot controller RC as shown in FIG. In response to this, the second feed speed setting signal included in the second welding control signal is switched from the second slowdown speed set value to the second steady feed speed set value, as shown in FIG. In addition, since the second feeding speed Fw2 changes from the second slowdown speed Fi2 to the second steady feeding speed Fc2, the value of the second welding current Iw2 is the second steady welding as shown in FIG. The current value is Ic2.

  As a result, at time t3, both the first arc generation signal Ac1 shown in FIG. 4D and the second arc generation signal Ac2 shown in FIG. 5H are set to the high level (in a state of being transmitted to the robot controller RC). Therefore, the first robot RM1 and the second robot RM2 start to move along the respective welding lines taught in advance and welding is started. In synchronization with this, the rotating jig PT on which the workpiece 2 is placed also starts to rotate.

  In the prior art 1 described above, when the first arc 31 is generated in advance, the first robot RM1 is stopped and the first welding current Iw1 is energized while waiting for the standby period Td1. Then, when the second arc 32 is generated with a delay, the movement of both robots RM1 and RM2 and the rotation of the rotating jig PT are started synchronously. Thus, in the prior art 1, the start synchronous arc welding method is performed.

  The above-mentioned arc generation signal often determines that an arc has occurred by determining that the welding current is energized. In some cases, it is determined that the welding voltage value has become an arc voltage value that is an intermediate value that is not as high as the no-load voltage value and not as low as the short-circuit voltage value.

[Prior Art 2]
FIG. 6 is a timing chart showing the start-synchronized arc welding method of the prior art 2 using the welding apparatus described above with reference to FIG. The figure corresponds to FIG. 5 described above, and the signals in FIGS. Hereinafter, an operation part different from FIG. 5 will be described.

  At time t2, when the first welding wire 11 comes into contact with the workpiece 2 as shown in FIG. 5A, the first wire-workpiece distance Lw1 becomes zero, and as shown in FIG. An arc 31 is generated and the first welding current Iw1 is energized. At this time, the first feed speed Fw1 is switched from the first slowdown speed Fi1 to the first welding start feed speed Fs1, as shown in FIG. A first welding start current Is1 corresponding to this feed rate is energized. The first welding start current Is1 is smaller than the steady welding current. At time t2, the first arc generation signal Ac1 is transmitted as shown in FIG. However, at this point in time, the second arc generation signal Ac2 shown in FIG. 5H is not transmitted (High level), so both the robots RM1 and RM2 remain stopped.

  At time t3, as shown in FIG. 5E, when the second welding wire 12 contacts the work 2, the second wire-workpiece distance Lw2 becomes zero, and as shown in FIG. The arc 32 is generated and the second welding current Iw2 is energized. At this time, as shown in FIG. 5G, the second feed speed Fw2 is switched from the second slow-down speed Fi2 to the second welding start feed speed Fs2, so as shown in FIG. The second welding start current Is2 is energized. At time t3, as shown in FIG. 5H, the second arc generation signal Ac2 is transmitted (High level). As a result, both arc generation signals Ac1 and Ac2 are transmitted (High level), so that the movement of both robots RM1 and RM2 and the rotation of the rotating jig PT are started synchronously and welding is started. At this time, as shown in FIG. 5C, the first feed speed Fw1 is switched to the first steady feed speed Fc1, so that the first welding current Iw1 is the first as shown in FIG. It changes to steady welding current Ic2. Further, as shown in FIG. 5G, the second feeding speed Fw2 is switched to the second steady feeding speed Fc2, so that the second welding current Iw2 is changed to the second steady feeding speed Fc2, as shown in FIG. It changes to welding current Ic2.

  As described above, in the related art 2, during the standby period Td1 from the occurrence of the first arc 31 to the occurrence of the second arc 32 after the occurrence of the first arc 31, the preceding first arc 31 is subjected to the steady welding current. Also apply a welding start current with a small value. Thereby, prevention of burn-out during the waiting period Td1 or prevention of expansion of the bead width is achieved (see, for example, Patent Document 1).

Japanese Patent No. 3733979

  In the prior art 1 described above with reference to FIG. 5, during the waiting period Td1 until the second arc 32 is generated on the second welding torch 42 after the first arc 31 is generated on the first welding torch 41 in advance. Then, a steady welding current is applied to the first arc 31. For this reason, there is no problem in welding quality when the waiting period is short, but when it is long, it will stop and melt out, or the bead width of that part will be too wide and the welding quality will deteriorate. was there.

  In the related art 2 described above with reference to FIG. 6, the welding start current is supplied to the first arc 31 during the standby period Td1. Since this welding start current is set to a value smaller than the steady welding current, even if the standby period Td1 becomes longer, the melting or bead width is suppressed more than in the prior art 1. However, if the welding start current is set to a very small value, the arc state becomes unstable and cannot be set. For this reason, when the waiting period Td1 becomes too long, the problem of melt-out or expansion of the bead width occurs as in the case of the prior art 1.

  Therefore, the present invention provides a start-synchronized arc welding method that can suppress burn-out or increase in bead width during the standby period by shortening the standby period.

In order to solve the above-described problem, the first invention moves the first welding torch and the second welding torch to the welding start positions taught in advance, respectively, and the first welding wire and the second welding wire from each welding torch. Feeding the welding wire is started at a slow-down speed, and when the first welding wire from the first welding torch comes into contact with the work and the first arc is generated in advance, the welding is made to wait in that state and delayed When the second arc from the second welding torch contacts the workpiece and a second arc is generated, the standby state is terminated and both welding torches are moved along the previously taught welding lines to perform welding. In the starting synchronized arc welding method,
The start-synchronized arc welding method is characterized in that when the first arc is generated, the slow-down speed of the second welding wire is switched from a normal value to a predetermined high-speed slow-down speed.

  In addition, the second invention is the start synchronous arc welding method according to the first invention, wherein the high-speed slowdown speed changes from a speed higher than the normal value to a slow speed as time passes. .

  According to a third aspect of the present invention, there is provided the start synchronous arc welding method according to the first aspect, wherein the high-speed slowdown speed changes from the normal value to a high speed as time elapses.

  According to the first invention described above, when the first arc occurs in advance, the waiting period of the first arc is greatly shortened by increasing the slow-down speed of the second welding wire from that point. can do. For this reason, it is possible to suppress the melted-out due to the first arc during the standby period or the expansion of the bead width of the welding start portion.

  According to the second invention described above, the value of the high-speed slowdown speed when the second welding wire comes into contact with the workpiece is smaller than the initial value at the time of switching. The arc start property of the second arc is improved as compared with the first invention. For this reason, the effect is particularly great in welding of an aluminum material in which arc start properties are a problem.

  According to the third invention described above, the effect of shortening the standby period is achieved, and when the standby period is short, the value of the high speed slowdown speed Fh is not so different from the normal value, so the arc start performance is not deteriorated. As the waiting period becomes longer, the value of the high-speed slowdown speed increases and the arc start performance becomes slightly worse, but the effect of suppressing the melting or bead width expansion by further shortening the waiting period is better. growing.

  Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment 1]
FIG. 1 is a timing chart showing a start synchronous arc welding method according to Embodiment 1 of the present invention. The welding apparatus is the same as that in FIG. 4 described above, but the control method is different. Therefore, this figure is a timing chart of each signal in FIG. (A) shows the first wire-workpiece distance Lw1, (B) shows the first welding current Iw1, (C) shows the first feeding speed Fw1, (D) ) Shows the first arc generation signal Ac1, FIG. 8E shows the second wire-workpiece distance Lw2, FIG. 8F shows the second welding current Iw2, and FIG. The feed speed Fw2 is shown, and FIG. 9H shows the second arc generation signal Ac2. Hereinafter, a description will be given with reference to FIG.

  At time t1, the first robot RM1 and the second robot RM2 reach the welding start position and stop at that position. When one robot arrives first, it waits until the other robot arrives. At time t1, as shown in FIG. 5C, the first welding wire 11 starts feeding at the first slow-down speed Fi1, so as shown in FIG. The distance Lw1 is gradually shortened. Further, since the second welding wire 12 starts feeding at the second slow-down speed Fi2 as shown in FIG. 5G, the second wire-workpiece distance Lw2 as shown in FIG. Here, the first welding wire 11 and the second welding wire 12 have different wire protruding lengths, because the wire protruding length of the first welding wire 11 is long, and therefore, at the time t1. This is a case where the distance Lw1 between the first wire and the workpiece is shorter than the distance Lw2 between the second wire and the workpiece, and as a result, the first welding wire 11 contacts the workpiece 2 before the second welding wire 12. To do.

  At time t2, as shown in FIG. 4A, when the first welding wire 11 comes into contact with the workpiece 2, the first wire-workpiece distance Lw1 becomes zero. As shown in FIG. One arc 31 is generated and the first welding current Iw1 is energized. Then, as shown in FIG. 4D, the first arc generation signal Ac1 becomes High level and is transmitted to the robot controller RC. However, as shown in FIG. 5H, since the second arc generation signal Ac2 is still at the low level, the first robot RM1 and the second robot RM2 remain stopped at the welding start position. When the first arc generation signal Ac1 is transmitted to the robot controller RC, the first feed speed setting signal included in the first welding control signal Wc1 changes. As shown in FIG. The one feed speed Fw1 is switched to the steady feed speed Fc1. As a result, as shown in FIG. 5B, the first welding current Iw1 becomes a steady welding current value Ic1.

  Further, when the first arc 31 is generated at time t2 and the first arc generation signal Ac1 is transmitted to the robot controller RC as shown in FIG. 4D, it is included in the second welding control signal Wc2. The second feed speed setting signal is changed, and the second feed speed Fw2 is switched to a predetermined high speed slowdown speed Fh as shown in FIG. The high speed slowdown speed Fh is a value larger than the normal value of the slowdown speed (second slowdown speed Fi2). For example, the normal value of the slowdown speed is about 1 to 2 m / min, and the high speed slowdown speed Fh is about 2 to 3 times that value. A larger value may be set depending on the welding conditions. When switching to the high speed slowdown speed Fh, as shown in FIG. 5E, the second wire-workpiece distance Lw2 approaches the work 2 faster than before until time t2, and contacts the work 2 at time t3. To do. For this reason, the standby period Td2 between times t2 and t3 is considerably shortened compared to the prior art.

  At time t3, when the second welding wire 12 comes into contact with the workpiece 2 as shown in FIG. 5E, the second wire-workpiece distance Lw2 becomes zero. Therefore, as shown in FIG. Two arcs 32 are generated and the second welding current Iw2 is energized. At time t3, as shown in FIG. 5H, the second arc generation signal Ac2 becomes High level and is transmitted to the robot controller RC. In response to this, the second feed speed setting signal included in the second welding control signal Wc2 changes, and the second feed speed Fw2 is changed to the second steady feed speed Fc2 as shown in FIG. Switch to. For this purpose, the second steady welding current Ic2 is energized as shown in FIG.

  At time t3, both the first arc generation signal Ac1 shown in FIG. 4D and the second arc generation signal Ac2 shown in FIG. 5H are at the high level, so that the first robot RM1 and the second robot RM2 are in advance. The welding is started by starting the movement along each taught welding line and starting the rotation of the rotating jig PT.

  According to the first embodiment described above, when the first arc occurs in advance, the first arc standby period Td2 is greatly increased by increasing the slowdown speed of the second welding wire from that point. It can be shortened. For this reason, it is possible to suppress the melted-out due to the first arc during the standby period or the expansion of the bead width of the welding start portion.

  A numerical example is shown for the effect of shortening the waiting period. In the figure, the height difference between the first wire-workpiece distance Lw1 and the second wire-workpiece distance Lw2 at time t1 is 8 mm, and the second slowdown speed Fi2 = 1.2 m / min. In some cases, the waiting period Td1 of the prior art is 400 ms. On the other hand, in the present embodiment, when the high-speed slowdown speed Gh = 3.6 m / min is set, the waiting period Td2 is shortened to 1/3, 133 ms.

  By the way, generally, when the slow-down speed is increased, the arc start property tends to be slightly deteriorated. Therefore, the arc start property of the second arc is slightly deteriorated also in the present embodiment. However, this is not a big problem as compared to the fact that the waiting period becomes longer and the weld quality is remarkably deteriorated due to melting or bead width expansion.

[Embodiment 2]
FIG. 2 is a timing chart showing a start synchronous arc welding method according to Embodiment 2 of the present invention. This figure corresponds to FIG. 1 described above, and the signals in FIGS. However, as shown in FIG. 5G, only the high-speed slowdown speed Fh during the waiting period Td2 at times t2 to t3 is different, and this point will be described.

  When the first arc 31 is generated at time t2, the second slowdown speed Fi2 of the second welding wire 12 is switched to the high speed slowdown speed Fh as shown in FIG. The high speed slowdown speed Fh according to the second embodiment increases in a step-like manner at the time t2 than the normal value (second slowdown speed Fi2), and thereafter gradually decreases with time. At time t3, the second welding wire 12 comes into contact with the work 2 and a second arc 32 is generated.

  According to the second embodiment described above, the value of the high-speed slowdown speed Fh at the time when the second welding wire comes into contact with the workpiece (time t3) is smaller than the initial value at the time of switching (time t2). In addition to the effect of shortening the period, the arc start performance of the second arc is improved as compared with the first embodiment. For this reason, the effect is particularly great in welding of an aluminum material in which arc start properties are a problem.

[Embodiment 3]
FIG. 3 is a timing chart showing a start synchronous arc welding method according to Embodiment 3 of the present invention. This figure corresponds to FIG. 1 described above, and the signals in FIGS. However, as shown in FIG. 5G, only the high-speed slowdown speed Fh during the waiting period Td2 at times t2 to t3 is different, and this point will be described.

  When the first arc 31 is generated at time t2, the second slowdown speed Fi2 of the second welding wire 12 is switched to the high speed slowdown speed Fh as shown in FIG. The high-speed slowdown speed Fh according to the third embodiment changes so as to gradually increase from the normal value (second slowdown speed Fi2) at time t2. At time t3, the second welding wire 12 comes into contact with the work 2 and a second arc 32 is generated.

  According to the third embodiment described above, the effect of shortening the standby period is exhibited, and when the standby period is short, the value of the high-speed slowdown speed Fh is not so different from the normal value, so the arc start performance is not deteriorated. As the waiting period increases, the value of the high-speed slowdown speed Fh increases and the arc start performance becomes slightly worse. However, the effect of suppressing melting or bead width expansion by further shortening the waiting period Is big.

  In the first to third embodiments described above, even if the first arc 31 is generated in advance, the first robot RM1 is stopped until the second arc 32 is generated. However, since the standby period is shortened by the first to third embodiments, the first robot RM1 may be moved along the weld line when the first arc 31 is generated. Further, a welding start current may be applied to the first arc 31 during the standby period, as in the case of the related art 2.

It is a timing chart which shows the start synchronous arc welding method which concerns on Embodiment 1 of this invention. It is a timing chart which shows the start synchronous arc welding method which concerns on Embodiment 2 of this invention. It is a timing chart which shows the start synchronous arc welding method which concerns on Embodiment 3 of this invention. It is a block diagram of the welding apparatus for enforcing the start synchronous arc welding method of a prior art. 6 is a timing chart showing a start-synchronized arc welding method of Prior Art 1. It is a timing chart which shows the start synchronous arc welding method of prior art 2.

Explanation of symbols

2 Work 11 First welding wire 12 Second welding wire 31 First arc 32 Second arc 41 First welding torch 42 Second welding torch Ac1 First arc generation signal Ac2 Second arc generation signal Fc1 First steady feeding speed Fc2 Second steady feed speed Fct1 First feed control signal Fct2 Second feed control signal Fh High speed slowdown speed Fi1 First slowdown speed Fi2 Second slowdown speed Fs1 First welding start Feed speed Fs2 Second weld start Feeding speed Fw1 First feeding speed Fw2 Second feeding speed Ic1 First steady current Ic2 Second steady current Is1 First welding start current Is2 Second welding start current Iw1 First welding current Iw2 Second welding current Lw1 First Wire-work distance Lw2 Second wire-work distance M1 First feed motor M2 Second feed motor Mc1 First motion control signal Mc2 Second motion control signal Pc External shaft control signal PS1 First welding power source S2 second welding power PT rotating jig RC robot controller RM1 first robot RM2 second robot Td1, Td2 waiting period Vw1 first welding voltage Vw2 second welding voltage Wc1 first welding control signal Wc2 second welding control signal

Claims (3)

The first welding torch and the second welding torch are respectively moved to the welding start positions taught in advance, and the feeding of the first welding wire and the second welding wire from each welding torch is started at a slow-down speed. When the first arc from the first welding torch contacts the workpiece and the first arc is generated in advance, the state is waited in that state, and the second welding wire from the second welding torch contacts the workpiece with a delay. Then, when the second arc occurs, in the start synchronous arc welding method of ending the standby state and moving both welding torches along the previously taught welding lines, respectively,
A start-synchronized arc welding method characterized by switching the slowdown speed of the second welding wire from a normal value to a predetermined high speed slowdown speed when the first arc is generated.   The start-synchronized arc welding method according to claim 1, wherein the high-speed slow-down speed changes from a speed higher than the normal value to a slow speed as time elapses. The start-synchronized arc welding method according to claim 1, wherein the high-speed slowdown speed changes from the normal value to a high speed as time elapses.

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