JP4499303B2 - Arc start control method for robot arc welding - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention, after the welding wire is brought close to and contacted with the workpiece, it is inverted to separate the welding wire from the workpiece to generate an initial arc, and the welding wire is again fed closer to the workpiece. The present invention relates to an arc start control method of robot arc welding for shifting to a steady arc.
[0002]
[Prior art]
A consumable electrode type robot arc welding in which a welding voltage is applied by a welding power source device to generate an arc between the welding wire and the workpiece, and a welding torch attached to the manipulator of the welding robot is moved to perform welding. In
When a welding start signal is input from the outside, the manipulator is moved to move the welding torch to the welding start position Sp taught in advance, and the wire feed motor is rotated in the forward direction while the wire feeding motor is rotated in the forward direction. When the wire is fed forward to the work piece, and then it is determined that the welding wire has contacted the work piece, the wire feed motor is reversely rotated to feed the welding wire backward, and at the same time, the initial current of a small current value is obtained. When Is is energized, and the welding wire is separated from the work piece by reverse feeding and an initial arc is generated, the welding wire is fed forward again at a steady feeding speed Ws and a steady welding current Ic is energized. At the same time, there has been known an arc start control method in which the welding torch is shifted from the above-mentioned stopped state to the welding direction taught in advance to shift to a steady arc. It has been. Hereinafter, this arc start control method of the prior art will be described with reference to the drawings.
[0003]
FIG. 2 is a block diagram of a conventional robot arc welding apparatus. Hereinafter, a description will be given with reference to FIG.
When the welding start signal St is input from the outside, the robot controller RC outputs an operation control signal Mc for controlling the operation of the manipulator RM, and also sets a voltage setting signal Vs, which will be described later with reference to FIG. An interface signal If formed by the setting signal Ws and the output start signal On is transmitted to the welding power source PS.
The manipulator RM is equipped with a wire feeding motor WM and a welding torch 4 and moves the tip position (TCP) of the welding torch 4 along a previously-instructed operation locus in accordance with the operation control signal Mc. The welding wire 1 is fed through a coil liner 4a having a length of about 1.5 [m] connecting between the wire feeding motor WM and the main body of the welding torch 4.
[0004]
The welding power supply device PS receives the interface signal If and supplies a welding voltage Vw to the welding wire 1 via a contact tip attached to the tip of the welding torch 4. An arc 3 is generated between them and a welding current Iw is applied. Similarly, the welding power source device PS outputs a feed control signal Fc to control the rotation direction and the rotation speed of the wire feed motor WM. The distance between the tip of the welding wire 1 and the work piece 2 is the distance Lw [mm] between the wire tip and the work piece, and thus the distance Lw between the wire tip and the work piece is the same as the arc length during arc generation. Become.
[0005]
FIG. 3 is a block diagram of the robot controller RC and the welding power source PS described above with reference to FIG. Hereinafter, each circuit block will be described with reference to FIG.
The robot controller RC is composed of the following circuit blocks. When the welding start signal St is input, the operation control circuit MC outputs an operation control signal Mc for moving the manipulator RM along a previously-instructed operation locus to the motor of each axis of the manipulator RM. At the same time, the operation control circuit MC outputs a voltage setting signal Vs, a steady feeding speed setting signal Ws, and an output start signal On to the robot interface circuit IFR. The robot interface circuit IFR transmits an interface signal If formed from the above three signals to the welding power source device PS.
[0006]
On the other hand, the welding power source device PS is composed of the following circuit blocks. The voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd. The short-circuit / arc discrimination circuit SA receives the voltage detection signal Vd as described above and outputs a short-circuit signal (High level) when the welding wire is in contact with the workpiece and an arc-generation signal when the arc is generated. (Low level) is output as a short circuit / arc discrimination signal Sa. The delay circuit DT has a predetermined delay time Td from the time when the short circuit / arc determination signal Sa changes from the short circuit signal to the arc generation signal in order to delay the timing of switching to forward feed again after the initial arc occurs. A delay signal Dt that is at a high level only during this period is output.
[0007]
The welding power supply interface circuit IFP receives the interface signal If and outputs a voltage setting signal Vs, a steady feeding speed setting signal Ws, and an output start signal On. When the output start signal On is input (High level), the forward / reverse feed control circuit RFC feeds the welding wire forward to the workpiece, and then the short / arc determination signal Sa is a short circuit signal. Then, the welding wire is fed backward from the workpiece, and when the delay signal Dt subsequently changes from the High level to the Low level, the welding wire is again sent to the workpiece to correspond to the above-described steady feeding speed setting signal Ws. A feed control signal Fc for feeding forward at the feeding speed is output. The wire feed motor WM feeds the welding wire forward or backward according to the feed control signal Fc.
[0008]
The output control circuit INV receives a commercial power supply (usually three-phase 200 V) and outputs a welding voltage and a welding current suitable for maintaining an arc stably by inverter control, thyristor phase control, or the like. This output control circuit INV energizes the initial current Is having a predetermined small current value from the time when the output start signal On is input to the time when the delay signal Dt changes from the High level to the Low level. A constant current characteristic or a drooping characteristic is generated and output, and thereafter, a constant corresponding to the voltage setting signal Vs for energizing the steady welding current Ic corresponding to the steady feeding speed setting signal Ws is output. A voltage characteristic is formed and output.
[0009]
FIG. 4 is a timing chart of each signal of the robot control device RC and the welding power source device PS described above with reference to FIG. FIG. 4A shows the time change of the welding start signal St, FIG. 2B shows the time change of the output start signal On, FIG. 3C shows the time change of the feed control signal Fc, FIG. (D) shows the time change of the short circuit / arc discrimination signal Sa, (E) shows the time change of the delay signal Dt, (F) shows the time change of the welding current Iw, G) shows the change over time in the distance Lw between the wire tip and the workpiece, and FIGS. (H1) to (H5) show the feeding state of the welding wire 1 at each time. Hereinafter, a description will be given with reference to FIG.
[0010]
(1) Period from time t1 to t2
At time t1, as shown in FIG. 5A, when the welding start signal St is input from the outside (High level), the welding torch 4 attached to the manipulator is moved, and at time t2, the welding torch 4 is moved. Arrives at the welding start position Sp taught in advance and stops.
[0011]
(2) Period from time t2 to t3
When the welding torch 4 arrives at the welding start position Sp at time t2, an output start signal On is output (High level) from the operation control circuit Mc described above, as shown in FIG. In response to this, as shown in FIG. 6C, the feed control signal Fc becomes a predetermined positive initial feed speed setting value Wi, and as shown in FIG. Is fed forward to the work piece 2 at an initial feed speed. When the feed control signal Fc is a positive value, forward feeding is performed, and when the feed control signal Fc is negative, backward feeding is performed. At the same time, the output control circuit INV described above forms and outputs a constant current characteristic or a drooping characteristic, but during this period, the welding wire 1 and the workpiece 2 are separated and are in an unloaded state. No load voltage is applied.
Further, during the period from the time t2 to the time t3, as shown in FIG. 5G, the distance Lw between the wire tip and the workpiece is gradually shortened by the above-described forward feeding.
[0012]
(3) Period from time t3 to t4
At time t3, when the welding wire 1 comes into contact with the work piece 2 by the forward feeding of the item (2) as shown in FIG. 11 (H2), as shown in FIG. The signal Sa changes to a short circuit signal (High level). In response to this, as shown in FIG. 5C, the feed control signal Fc becomes a predetermined negative value of the reverse feed speed setting value Wr, and the welding wire 1 moves backward from the work piece 2 to the reverse feed speed. It is fed backwards. At the same time, as shown in FIG. 5F, the initial current Is having a small current value is applied by the constant current characteristic or the drooping characteristic described in the item (2). The value of the initial current Is is set to a small current value of about several [A] to several tens [A].
Further, during the period from the time t3 to the time t4, a motor response delay time for the above-described wire feed motor WM to reverse from forward rotation (forward feed) to reverse rotation (reverse feed) occurs. Furthermore, a play response delay time for canceling the play due to the bending of the coil liner described above by reverse feeding also occurs. For this reason, during this period, the welding wire 1 and the workpiece 2 remain in contact with each other, and the distance Lw between the wire tip and the workpiece is 0 [mm] as shown in FIG. Remains.
[0013]
(4) Period from time t4 to t5
Immediately after time t4, as shown in (H3) of the figure, when the welding wire 1 and the work piece 2 are separated by the backward feeding of the item (3), the initial arc 3a to which the initial current Is is energized is generated. appear. Further, from the time t4 when the initial arc 3a is generated to the time t5 when the delay time Td described above elapses, the delay signal Dt remains at the high level as shown in FIG. During this time, as shown in FIG. 4 (H4), the backward feeding is continued while maintaining the initial arc generation state 3a. Therefore, as shown in FIG. 5G, the distance Lw between the wire tip and the workpiece is gradually increased.
[0014]
(5) Period after time t5
At time t5, when the delay signal Dt changes from the High level to the Low level as shown in (E) of the figure, the feed control signal Fc is a positive value of steady transmission as shown in (C) of the figure. The feed speed setting signal Ws is obtained, and the welding wire 1 is fed forward again to the workpiece 2 at a steady feed speed. At the same time, the output control circuit INV described above forms a constant voltage characteristic corresponding to the voltage setting signal Vs. Therefore, the welding voltage (not shown) has a value corresponding to the voltage setting signal Vs and is shown in FIG. As described above, a steady welding current Ic having a large current value corresponding to the steady feeding speed Ws is energized. At the same time, the welding torch 4 is switched from the stopped state to the movement in the welding direction taught in advance.
[0015]
However, also at this time t5, the motor response delay time and the play response delay time occur (time t5 to t6) as in the above-described time period t3 to t4. Therefore, as shown in FIG. 5G, the wire tip-to-be-welded distance Lw converges to the steady arc length at time t6, and from the initial arc 3a at time t5 shown in FIG. Transition to the steady arc 3b at time t6 shown in (H5).
[0016]
[Problems to be solved by the invention]
FIG. 5 is a timing chart corresponding to FIG. 4 described above for explaining the problem to be solved in the prior art. FIG. 4A shows the time change of the welding start signal St, FIG. 2B shows the time change of the output start signal On, FIG. 3C shows the time change of the feed control signal Fc, FIG. (D) shows the time change of the short circuit / arc discrimination signal Sa, (E) shows the time change of the delay signal Dt, (F) shows the time change of the welding current Iw, G) shows the change over time in the distance Lw between the wire tip and the workpiece, and FIGS. (H1) to (H5) show the feeding state of the welding wire 1 at each time. In the figure, the operation during the period other than time t3 to t4 and time t5 to t6 is the same as that in FIG. Hereinafter, both periods of time t3 to t4 and time t5 to t6 in the same figure will be described with reference to the same figure.
[0017]
(1) Period from time t3 to t4 (first response delay time T1)
As described above in the description of FIG. 4, when the welding wire 1 and the work piece 2 come into contact with each other at the time t3 as shown in FIG. / The arc discrimination signal Sa changes to a short circuit signal (High level), and the welding wire 1 is reversed from forward feeding and switched to backward feeding. At this time, a motor response delay time for the wire feeding motor WM shown in FIG. 3 to switch from forward rotation for forward feeding to reverse rotation for backward feeding occurs. Furthermore, as described above, a play response delay time for canceling the play due to the bending of the coil liner connecting the wire feed motor WM and the welding torch main body by the reverse feed occurs. This play response delay time greatly varies depending on the length of the coil liner, the degree of bending of the coil liner caused by various welding postures, and the like. The motor response delay time and the play response delay time are added to form a first response delay time T1.
Immediately after time t4 after the elapse of the first response delay time T1, as shown in FIG. 5H3, the welding wire 1 and the work piece 2 are separated from each other by the original backward feeding, and an initial arc 3a is generated. Then, as shown in FIG. 5G, thereafter, the distance Lw between the wire tip and the workpiece is gradually increased. Usually, the first response delay time T1 is about 300 to 500 [ms].
[0018]
(2) Period from time t5 to t6 (second response delay time T2)
At time t5, when the delay signal Dt changes from the High level to the Low level as shown in FIG. 5E while maintaining the initial arc generation state as shown in FIG. Reverses from reverse feed and switches to forward feed. At this time, similarly to the above item (1), a motor response delay time for the wire feed motor WM to switch from reverse rotation of reverse feed to forward rotation of forward feed occurs. Furthermore, a play response delay time for canceling the play due to the bending of the coil liner by forward feeding occurs. The motor response delay time and the play response delay time are added to obtain a second response delay time T2. Usually, the second response delay time T2 is also about 300 to 500 [ms].
[0019]
The first problem to be solved is as follows. During the second response delay time T2 from time t5 to time t6, a steady welding current Ic having a current value larger than the initial current Is is energized as shown in FIG. The feeding speed of the welding wire is a transient value smaller than the steady value due to the response delay time. For this reason, since the melting rate by the steady welding current Ic becomes larger than the transient feed rate, the arc length (distance Lw between the wire tip and the workpiece to be welded) is set as shown in FIG. After time t5, the length becomes longer, and as shown in FIG. 5H5, the arc 3c having an excessive arc length melts down, resulting in a weld defect such as a bead defect. Hereinafter, this first problem to be solved is referred to as poor welding due to arc length increase during the response delay time.
[0020]
Furthermore, the second problem to be solved is as follows. The response delay time T1 + T2 of the added value of the first response delay time T1 and the second response delay time T2 is 600 to 1000 [ms]. This unnecessary time is required for each arc start. In general, in the welding of machine parts, automobile parts, etc., there are many cases where a large number of weldings that generate an arc for only a few seconds are performed. In such a large number of short-time weldings, an extra time of 600 to 1000 [ms] is required for each arc start, resulting in poor productivity. Hereinafter, this problem is referred to as a decrease in productivity due to response delay time.
[0021]
Therefore, in the present invention, it is possible to prevent the occurrence of poor welding due to the arc length increase during the response delay time described above, prevent the productivity from being lowered due to the response delay time, and realize a good arc start. An arc start control method for robot arc welding is provided.
[0022]
[Means for Solving the Problems]
The invention of claim 1 at the time of filing, as shown in FIGS.
The welding power supply device PS applies a welding voltage Vw to generate an arc between the welding wire 1 and the workpiece 2 and wears the welding torch 4 attached to the manipulator RM of the welding robot for welding. In electrode-type robot arc welding,
When the welding start signal St is input, the welding torch 4 is moved to the welding start position Sp taught in advance,
After reaching the welding start position Sp, the welding torch 4 is moved substantially in the feeding direction of the welding wire to bring the wire tip closer to the workpiece 2;
When it is determined that the tip of the wire is in contact with the workpiece 2, an initial current Is having a predetermined small current value is energized from the welding power source device PS and the welding torch 4 is substantially in the direction of feeding the welding wire. Move backwards to move the wire tip away from the work piece 2;
When the wire tip and the workpiece 2 are separated by the backward movement, an initial arc 3a in which the initial current Is is energized is generated,
While the initial arc generation state 3a is maintained, the backward movement is continued and when the welding torch 4 returns to the welding start position Sp, the backward movement is switched to the movement in the welding direction taught in advance, and the welding is simultaneously performed. This is an arc start control method for robot arc welding in which the feeding of the wire 1 is started and a steady welding current Ic is applied to smoothly transition from the initial arc generation state 3a to the steady arc generation state 3b.
[0023]
The invention of claim 2 at the time of filing, as shown in FIGS.
The welding power supply device PS applies a welding voltage Vw to generate an arc between the welding wire 1 and the workpiece 2 and wears the welding torch 4 attached to the manipulator RM of the welding robot for welding. In electrode-type robot arc welding,
When the welding start signal St is input, the welding torch 4 is moved to the welding start position Sp taught in advance,
After reaching the welding start position Sp, the welding torch 4 is moved substantially in the feeding direction of the welding wire to bring the wire tip closer to the workpiece 2;
When it is determined that the tip of the wire is in contact with the workpiece 2, an initial current Is having a predetermined small current value is energized from the welding power source device PS and the welding torch 4 is substantially in the direction of feeding the welding wire. Move backwards to move the wire tip away from the work piece 2;
When the wire tip and the workpiece 2 are separated by the backward movement, an initial arc 3a in which the initial current Is is energized is generated,
While the initial arc generation state 3a is maintained, the backward movement is continued, and when the distance Lw between the wire tip and the workpiece reaches a predetermined backward distance setting value Ls, the backward movement returns to the welding start position Sp. Switch to the movement, simultaneously start feeding the welding wire 1 and energize the steady welding current Ic,
After returning to the welding start position Sp, the arc of robot arc welding that smoothly shifts from the initial arc generation state 3a to the steady arc generation state 3b by moving the welding torch 4 in the welding direction taught in advance. This is a start control method.
[0024]
The invention of claim 3 at the time of filing is as shown in FIG.
Claim 2 at the time of filing that the feeding start of the welding wire 1 and the start of energization of the steady welding current Ic described in claim 2 at the time of filing are performed from the time when the welding torch 4 returns to the welding start position Sp by the return movement. This is an arc start control method.
[0025]
The invention of claim 4 at the time of filing, as shown in FIGS.
When the return movement described in claim 2 at the time of filing is a movement in the direction of shortening the distance Lw between the wire tip and the workpiece, the current value is larger than the steady welding current Ic during the return movement period Tb. The arc start control method according to claim 2 at the time of filing to energize the transition current Ib1.
[0026]
The invention of claim 5 at the time of filing, as shown in FIGS.
When the return movement described in claim 2 at the time of filing is a movement in a direction to shorten the distance Lw between the wire tip and the workpiece, the feeding of the welding wire 1 is stopped during the return movement period Tb. Then, a predetermined transition current Ib2 is applied corresponding to the speed of the return movement, and after the welding torch 4 returns to the welding start position Sp, the welding wire 1 starts to be fed and a steady welding current Ic is supplied. The arc start control method according to claim 2 at the time of filing.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
An example of an embodiment of the present invention is shown in FIG. 1 (the same diagram as FIG. 7),
As shown in FIG. 5A, when a welding start signal St is input from the outside, the welding torch 4 is moved to a welding start position Sp taught in advance,
After reaching the welding start position Sp (time t2), the welding torch 4 is moved substantially in the feed direction of the welding wire to bring the wire tip closer to the workpiece 2;
As shown in FIG. 4D, when it is determined that the wire tip has contacted the work piece 2 (time t3), an initial current Is having a predetermined small current value is applied and the welding torch 4 is substantially omitted. Move backward in the direction opposite to the welding wire feed direction to move the wire tip away from the work piece 2;
When the wire tip and the work piece 2 are separated by the backward movement (time t4), as shown in FIG. (H3), an initial arc 3a in which the initial current Is is supplied is generated.
While the initial arc generation state 3a is maintained, the backward movement is continued, and when the welding torch 4 returns to the welding start position Sp (time t5), the movement from the backward movement to the welding direction taught in advance is performed. By switching, and simultaneously feeding the welding wire 1 and energizing the steady welding current Ic, the steady arc generation shown in FIG. (H5) from the initial arc generation state 3a shown in FIG. This is an arc start control method of robot arc welding that smoothly shifts to the state 3b.
[0028]
【Example】
[Example 1]
The invention of the first embodiment described below corresponds to the invention of claim 1 at the time of filing. The invention of Example 1 is the robot arc welding,
(1) When a welding start signal is input, after the welding torch is moved to the previously taught welding start position Sp,
(2) Move the welding torch approximately in the welding wire feeding direction to bring the wire tip closer to the workpiece,
(3) When the tip of the wire comes into contact with the work piece, an initial current Is having a predetermined small current value is applied, and the welding torch is moved in a direction substantially opposite to the feeding direction of the welding wire to cover the tip of the wire. Move backwards away from the weldment,
(4) When the tip of the wire and the work piece are separated by the backward movement, an initial arc in which the initial current Is is energized is generated, and the backward movement is continued while maintaining the initial arc generation state.
(5) When the welding torch returns to the welding start position Sp, it switches from the backward movement to the movement in the welding direction taught in advance, and simultaneously starts feeding the welding wire and energizes the steady welding current Ic. This is an arc start control method. Hereinafter, the invention of Example 1 will be described with reference to the drawings.
[0029]
FIG. 6 is a block diagram of the robot controller RC and the welding power source device PS for carrying out the arc start control method of the first embodiment. In the figure, the same circuit blocks as those in FIG. 3 described above are denoted by the same reference numerals, and description thereof is omitted. Hereinafter, operation synchronous operation control circuit SMC, operation synchronous robot interface circuit SIFR, operation synchronous welding power supply interface circuit SIFP, operation synchronous feed control circuit SFC, and operation synchronous output control, which are different circuit blocks from FIG. The circuit SINV will be described.
[0030]
When the welding start signal St is input from the outside, the operation synchronous operation control circuit SMC outputs a predetermined voltage setting signal Vs and a steady feeding speed setting signal Ws, and a manipulator RM (welding torch 4). After moving to the welding start position Sp and arriving at the welding start position Sp, the output start signal On is output and the manipulator RM is moved in the substantially feeding direction, and when the short circuit / arc determination signal Sa becomes a short circuit signal, When the manipulator RM is moved backward and returned to the welding start position Sp, a return signal Rp is output and an operation control signal Mc for moving the manipulator RM in the taught welding direction is output.
[0031]
The operation-synchronized robot interface circuit SIFR is an interface signal If formed from the five signals of the voltage setting signal Vs, the steady feeding speed setting signal Ws, the output start signal On, the short-circuit / arc determination signal Sa, and the return signal Rp. Is communicated with the welding power source PS.
[0032]
The operation synchronous welding power source interface circuit SIFP communicates with the robot controller RC an interface signal If formed from the above five signals. When the return signal Rp is input, the operation synchronous feed control circuit SFC receives a feed control signal Fc that feeds the welding wire forward at a feed rate corresponding to the steady feed rate setting signal Ws. Output. The operation synchronous output control circuit SINV is a constant current characteristic that energizes an initial current Is having a predetermined small current value from the time when the output start signal On is input to the time when the return signal Rp is input. Alternatively, a drooping characteristic is formed and output, and thereafter, a constant voltage characteristic corresponding to the voltage setting signal Vs for applying the steady welding current Ic corresponding to the steady feeding speed setting signal Ws is formed. And output.
[0033]
FIG. 7 is a timing chart of each signal of the robot control device RC and the welding power source device PS of the first embodiment described above with reference to FIG. FIG. 4A shows the time change of the welding start signal St, FIG. 2B shows the time change of the output start signal On, FIG. 3C shows the time change of the feed control signal Fc, (D) shows the time change of the short circuit / arc discrimination signal Sa, (E) shows the time change of the return signal Rp, (F) shows the time change of the welding current Iw, G) shows the change over time in the distance Lw between the wire tip and the workpiece, and FIGS. (H1) to (H5) show the feeding state of the welding wire 1 at each time. In the figure, the delay signal Dt shown in FIGS. 3 (E) and 4 (E) is replaced by the return signal Rp. Hereinafter, a description will be given with reference to FIG.
[0034]
(1) Period from time t1 to t2
At time t1, as shown in FIG. 6A, when the welding start signal St is input from the outside (High level), the welding torch 4 mounted on the manipulator is moved, and FIG. As shown, at time t2, the welding torch 4 arrives at the welding start position Sp taught in advance and stops.
[0035]
(2) Period from time t2 to t3
When the welding torch 4 arrives at the welding start position Sp at time t2, the output start signal On is output (High level) from the operation synchronous operation control circuit SMC described above, as shown in FIG. In response to this, while the feeding of the welding wire 1 is stopped, the operation synchronous output control circuit SINV described above forms and outputs a constant current characteristic or a drooping characteristic. Since it is separated from the weldment 2 and is in a no-load state, a no-load voltage is applied. At the same time, the welding torch 4 is moved substantially in the feeding direction of the welding wire, and the tip of the wire is brought closer to the workpiece 2. Accordingly, as shown in FIG. 5G, the distance Lw between the wire tip and the workpiece is gradually shortened.
[0036]
(3) Period from time t3 to t4
At time t3, when the tip of the wire comes into contact with the work piece 2 by the movement of the welding torch 4 in the above item (2) as shown in FIG. (H2), as shown in FIG. The determination signal Sa changes to a short circuit signal (High level). In response to this change, the welding torch 4 is moved backward in the direction opposite to the feeding direction of the welding wire. At the same time, as shown in FIG. 5F, the initial current Is having a small current value is applied by the constant current characteristic or the drooping characteristic described in the item (2).
Further, the welding torch 4 is moved backward during the period from the time t3 to the time t4, but the welding wire 1 and the workpiece 2 are in contact with each other by the first response delay time T11 due to the response delay time of the manipulator motor. The state remains. Therefore, as shown in FIG. 5G, the distance Lw between the wire tip and the work piece remains 0 [mm]. However, the first response delay time T11 is shorter than the first response delay time T1, which is the sum of the motor response delay time and the play response delay time described above in the description of FIG. Normally, the value is about 100 [ms] or less.
[0037]
(4) Period from time t4 to t5
At time t4, as shown in FIG. 5H3, when the wire tip and the workpiece 2 are separated by the backward movement of the item (3), the initial arc 3a in which the initial current Is is energized is generated. . Further, the backward movement is continued from time t4 when the initial arc 3a is generated to time t5 when the welding torch 4 returns to the welding start position Sp. Therefore, as shown in FIG. 5G, the distance Lw between the wire tip and the workpiece is gradually increased.
[0038]
(5) Period after time t5
At time t5, when the welding torch 4 returns to the welding start position Sp by the backward movement of the item (4), a return signal Rp is output (High level) as shown in FIG. In response to this, the feed control signal Fc becomes a positive feed speed setting signal Ws having a positive value, and the welding wire 1 is fed forward to the workpiece 2 as shown in FIG. At the same time, the operation synchronous output control circuit SINV described above forms a constant voltage characteristic corresponding to the voltage setting signal Vs, so that the welding voltage Vw (not shown) becomes a value corresponding to the voltage setting signal Vs, and As shown in F), a steady welding current Ic having a large current value corresponding to the steady feeding speed Ws is energized. At the same time, the welding torch 4 starts to move in the welding direction taught in advance.
[0039]
At time t5, the response delay time of the manipulator motor and the response delay time of the wire feed motor for switching the welding torch 4 from the backward movement to the movement in the welding direction are generated. However, since the manipulator only changes the moving direction, the response delay time due to this is short. On the other hand, the wire feed motor is not the reverse rotation from the reverse rotation to the normal rotation as in the prior art, but only the start of the normal rotation, so the response delay time due to this is short. Therefore, the second response delay time T21 of the present invention, which is the above-described addition value, is shorter than the second response delay time T2 of the prior art, and the value is normally 100 [ms] or less. Therefore, after a short period T21 from time t5 to time t6 has elapsed, the transition from the initial arc 3a shown in FIG. 5H to the steady arc 3b shown in FIG. Welding failure due to arc length increase during time does not occur. Furthermore, since the total response delay time T11 + T21 of the present invention is 1/3 to 1/5 or less of the response delay time T1 + T2 of the prior art, it is possible to prevent a decrease in productivity due to the response delay time. it can.
[0040]
[Example 2]
The invention of Example 2 described below corresponds to the invention of claim 2 at the time of filing. The invention of Example 2
(1) When the distance Lw between the wire tip and the workpiece to be welded reaches a predetermined setback distance Ls by the backward movement of the welding torch while maintaining the initial arc generation state in the invention of the first embodiment, Switching from the backward movement to the return movement to the welding start position Sp, simultaneously starting the feeding of the welding wire and energizing the steady welding current Ic,
(2) An arc start control method in which when the welding torch returns to the welding start position Sp, the return movement is switched to the movement in the welding direction taught in advance. Hereinafter, the invention of Example 2 will be described with reference to the drawings.
[0041]
FIG. 8 is a block diagram of the robot control device RC and the welding power source device PS for carrying out the arc start control method of the second embodiment. In the figure, the same circuit blocks as those in FIG. 6 described above are denoted by the same reference numerals, and description thereof is omitted. Hereinafter, operation synchronous operation control circuit SMC, operation synchronous robot interface circuit SIFR, operation synchronous welding power supply interface circuit SIFP, operation synchronous feed control circuit SFC, and operation synchronous output control, which are different circuit blocks from FIG. The circuit SINV will be described.
[0042]
When the welding start signal St is input from the outside, the operation synchronous operation control circuit SMC of the second embodiment outputs a predetermined voltage setting signal Vs and a steady feeding speed setting signal Ws, and a manipulator RM (welding When the torch 4) is moved to the welding start position Sp and arrives at the welding start position Sp, the output start signal On is output and the manipulator RM is moved in the substantially feeding direction, and the short circuit / arc determination signal Sa becomes the short circuit signal. Then, the manipulator RM is moved backward, and unlike the first embodiment, when the distance Lw between the wire tip and the work piece reaches a predetermined backward distance set value Ls due to the backward movement described above, the backward distance coincidence signal Lp is output. At the same time, the manipulator RM is moved back to the welding start position Sp, and after returning to the welding start position Sp, the manipulator RM is moved in the welding direction taught. It outputs a that operation control signals Mc.
[0043]
The operation synchronous robot interface circuit SIFR of the second embodiment includes the voltage setting signal Vs, the steady feeding speed setting signal Ws, the output start signal On, the short-circuit / arc determination signal Sa, and a backward distance coincidence signal different from the first embodiment. An interface signal If formed from the five Lp signals is communicated with the welding power source PS.
[0044]
The operation synchronous welding power supply interface circuit SIFP of the second embodiment communicates an interface signal If formed from the above five signals with the robot controller RC. The operation synchronous feeding control circuit SFC according to the second embodiment forwards the welding wire at a feeding speed corresponding to the steady feeding speed setting signal Ws when the backward distance coincidence signal Lp is input. A feed control signal Fc is output. The operation-synchronized output control circuit SINV according to the second embodiment has an initial current Is having a predetermined small current value between the time when the output start signal On is input and the time when the backward distance coincidence signal Lp is input. A constant current characteristic or a drooping characteristic is generated and output, and thereafter, it corresponds to the voltage setting signal Vs for supplying the steady welding current Ic corresponding to the steady feeding speed setting signal Ws. A constant voltage characteristic is formed and output.
[0045]
FIG. 9 is a timing chart of signals of the robot control device RC and the welding power source device PS according to the second embodiment described above with reference to FIG. FIG. 4A shows the time change of the welding start signal St, FIG. 2B shows the time change of the output start signal On, FIG. 3C shows the time change of the feed control signal Fc, FIG. (D) shows the time change of the short-circuit / arc discrimination signal Sa. Unlike FIG. 1, (E) shows the time change of the receding distance coincidence signal Lp, and FIG. (F) shows the welding current Iw. The time change shows the time change of the distance Lw between the wire tip and the workpiece, and FIGS. (H1) to (H5) show the feeding state of the welding wire 1 at each time. In the figure, in order to show the unique effect of the second embodiment, the distance Lw between the wire tip and the workpiece to be welded when the welding torch 4 first reaches the welding start position Sp is less than about 3 [mm] This is a very short case of 0 [mm] (contact). Hereinafter, a description will be given with reference to FIG.
[0046]
(1) Period from time t1 to t2
At time t1, as shown in FIG. 6A, when the welding start signal St is input from the outside (High level), the welding torch 4 mounted on the manipulator is moved, and FIG. As shown, at time t2, the welding torch 4 arrives at the welding start position Sp taught in advance and stops.
[0047]
(2) Period from time t2 to t3
When the welding torch 4 arrives at the welding start position Sp at time t2, the output start signal On is output (High level) from the operation synchronous operation control circuit SMC described above, as shown in FIG. Accordingly, while the feeding of the welding wire 1 is stopped, the operation synchronous output control circuit SINV described above forms and outputs a constant current characteristic or a drooping characteristic. During this period, the welding wire 1 and the workpiece to be welded are output. Since it is away from the object 2 and is in a no-load state, a no-load voltage is applied. At the same time, the welding torch 4 is moved substantially in the feeding direction of the welding wire, and the tip of the wire is brought closer to the workpiece 2. At this time, since the distance Lw between the wire tip and the workpiece to be welded at time t2 is very short as described above, it becomes 0 [mm] in a short time as shown in FIG.
[0048]
(3) Period from time t3 to t4
At time t3, when the tip of the wire comes into contact with the work piece 2 by the movement of the welding torch 4 in the above item (2) as shown in FIG. (H2), as shown in FIG. The determination signal Sa changes to a short circuit signal (High level). In response to this change, the welding torch 4 is moved backward in the direction opposite to the feeding direction of the welding wire. At the same time, as shown in FIG. 5F, the initial current Is having a small current value is applied by the constant current characteristic or the drooping characteristic described in the item (2).
Further, the welding torch 4 is moved backward during the period from the time t3 to the time t4, but the welding wire 1 and the workpiece 2 are in contact with each other by the first response delay time T11 due to the response delay time of the manipulator motor. The state remains. Therefore, as shown in FIG. 5G, the distance Lw between the wire tip and the work piece remains 0 [mm]. However, as in the first embodiment, the first response delay time T11 is the first response delay time which is the sum of the motor response delay time and the play response delay time described above in the description of FIG. The time is shorter than T1, and the value is usually about 100 [ms] or less.
[0049]
(4) Period from time t4 to t5
At time t4, as shown in FIG. 5H3, when the wire tip and the workpiece 2 are separated by the backward movement of the item (3), the initial arc 3a in which the initial current Is is energized is generated. Further, the backward movement is continued from time t4 when the initial arc 3a is generated to time t5 when the distance Lw between the wire tip and the workpiece reaches a predetermined backward distance setting value Ls. Therefore, as shown in FIG. 5G, the distance Lw between the wire tip and the workpiece is gradually increased and becomes equal to the retreat distance setting value Ls at time t5.
[0050]
(5) Period after time t5
At time t5, when the distance Lw between the wire tip and the work piece reaches the retraction distance set value Ls due to the retreat movement of the above item (4), a retreat distance coincidence signal Lp is output as shown in FIG. High level). In response to this, the feed control signal Fc becomes a positive feed speed setting signal Ws having a positive value, and the welding wire 1 is fed forward to the workpiece 2 as shown in FIG. At the same time, the above-described operation synchronous output control circuit SINV forms a constant voltage characteristic corresponding to the voltage setting signal Vs, so that the welding voltage Vw (not shown) becomes a value corresponding to the voltage setting signal Vs, and FIG. ), A steady welding current Ic having a large current value corresponding to the steady feeding speed Ws is energized. At the same time, the welding torch 4 is moved back to the welding start position Sp. After returning to the time t51, the movement is started in the welding direction taught in advance.
[0051]
Similar to the first embodiment, at time t5, the response delay time of the manipulator motor for switching the welding torch 4 to the movement in the welding direction through the return movement to the welding start position Sp in the backward movement, the wire feed Response delay time of the feed motor occurs. However, since the manipulator only changes the moving direction, the motor response delay time due to this is short. On the other hand, the wire feed motor does not reverse from the reverse rotation to the normal rotation as in the prior art, but only the start of the normal rotation, and thus the response delay time is short. Therefore, the second response delay time T21 of the present invention, which is the above-described addition value, is shorter than the second response delay time T2 of the prior art, and the value is normally 100 [ms] or less. For this reason, after a short period T21 from time t5 to time t6 has elapsed, the transition from the initial arc 3a shown in FIG. 5H to the steady arc 3b shown in FIG. Welding failure due to arc length increase during time does not occur. Furthermore, since the total response delay time T11 + T21 of the present invention is 1/3 to 1/5 or less of the response delay time T1 + T2 of the prior art, it is possible to prevent a decrease in productivity due to the response delay time. it can.
[0052]
Furthermore, in Example 1, the backward movement continues until the welding start position Sp is restored. For this reason, when the distance Lw between the wire tip and the workpiece to be welded when arriving at the welding start position Sp for the first time is very short or in contact, the backward movement of an appropriate distance cannot be performed. In addition, a phenomenon in which the initial arc 3a does not occur at all or a phenomenon in which the initial arc 3a disappears due to recontact may occur, resulting in a defective arc start. On the other hand, in Example 2, even when the distance Lw between the wire tip and the workpiece to be welded when it first arrives at the welding start position Sp is very short or in contact, an appropriate setback distance Ls is set. Since the backward movement is surely continued until reaching the above, the above problem does not occur.
[0053]
[Example 3]
The invention of Example 3 described below corresponds to the invention of claim 3 at the time of filing. The invention of Example 3 is an arc start in which the welding wire feeding start and the steady welding current Ic energization start in the invention of Example 2 described above are started from the time when the welding torch returns to the welding start position Sp by the return movement. It is a control method. The invention of Example 3 will be described below with reference to the drawings.
[0054]
The block diagram of the robot control device RC and the welding power source device PS for carrying out the arc start control method of the third embodiment has a configuration in which the operation synchronous operation control circuit SMC is changed as follows in FIG. Are the same. Hereinafter, the operation synchronous operation control circuit SMC of the third embodiment will be described.
When the welding start signal St is input, the operation synchronous operation control circuit SMC of the third embodiment outputs a predetermined voltage setting signal Vs and a feeding speed setting signal Ws, and a manipulator RM (welding torch 4). After moving to the welding start position Sp and arriving at the welding start position Sp, the output start signal On is output and the manipulator RM is moved in the substantially feeding direction, and when the short circuit / arc determination signal Sa becomes a short circuit signal, The manipulator RM is moved back to the welding start position Sp when the distance Lw between the wire tip and the workpiece to be welded reaches a predetermined setback distance Ls by the above-mentioned backward movement. When returning to the start position Sp, a return signal Rp is output and an operation control signal for moving the manipulator in the taught welding direction. And outputs the Mc.
[0055]
FIG. 10 is a timing chart of each signal of the robot control device RC and the welding power source device PS according to the third embodiment described above. FIG. 4A shows the time change of the welding start signal St, FIG. 2B shows the time change of the output start signal On, FIG. 3C shows the time change of the feed control signal Fc, FIG. (D) shows the time change of the short circuit / arc discrimination signal Sa. Unlike FIG. 2, (E) shows the time change of the return signal Rp, and (F) shows the time change of the welding current Iw. (G) shows the change over time of the distance Lw between the wire tip and the workpiece, and (H1) to (H5) show the feeding state of the welding wire 1 at each time. In the figure, since the operation before time t5 is the same as that in FIG. 9 described above, description of those periods is omitted. Hereinafter, a period after time t5 different from FIG. 9 will be described.
[0056]
Period after time t5
When the distance Lw between the wire tip and the workpiece reaches the backward distance set value Ls due to the backward movement at time t5, the welding torch 4 is moved back to the welding start position Sp at time t51 and returned to the welding start position Sp at time t51. As shown in FIG. 5E, the return signal Rp is output (High level). In response to this, the feed control signal Fc becomes a positive feed speed setting signal Ws having a positive value, and the welding wire 1 is fed forward to the workpiece 2 as shown in FIG. At the same time, the operation synchronous output control circuit SINV described above forms a constant voltage characteristic corresponding to the voltage setting signal Vs, so that the welding voltage Vw (not shown) becomes a value corresponding to the voltage setting signal Vs, and As shown in F), a steady welding current Ic having a large current value corresponding to the steady feeding speed Ws is energized.
[0057]
[Example 4]
The invention of Example 4 described below corresponds to the invention of claim 4 at the time of filing. In the invention of the fourth embodiment, when the return movement in the invention of the second embodiment is a movement in a direction to shorten the wire tip-to-be-welded distance Lw, during the return movement period Tb, the steady welding current Ic is used. This is an arc start control method in which a transition current Ib1 having a large current value is applied. Hereinafter, the invention of Example 4 will be described with reference to the drawings.
[0058]
FIG. 11 is a block diagram of the robot controller RC and the welding power source PS for carrying out the arc start control method of the fourth embodiment. In the figure, the same circuit blocks as those in FIG. 8 described above are denoted by the same reference numerals, and description thereof is omitted. Hereinafter, the operation synchronous operation control circuit SMC, the operation synchronous robot interface circuit SIFR, the operation synchronous welding power supply interface circuit SIFP, and the operation synchronous output control circuit SINV, which are circuit blocks different from those in FIG.
[0059]
When the welding start signal St is input, the operation synchronous operation control circuit SMC of the fourth embodiment receives a predetermined voltage setting signal Vs, a steady feeding speed setting signal Ws, and an initial current setting signal Is that is not in the second embodiment. , The manipulator RM (welding torch 4) is moved to the welding start position Sp, and after reaching the welding start position Sp, the output start signal On is output and the manipulator RM is moved substantially in the feeding direction. When the short-circuit / arc discrimination signal Sa becomes a short-circuit signal, the manipulator RM is moved backward, and when the distance Lw between the wire tip and the workpiece reaches a predetermined backward distance set value Ls by the backward movement, the backward distance When the coincidence signal Lp is output and the return movement to the welding start position Sp is a movement in the direction of shortening the distance Lw between the wire tip and the workpiece, it is When the initial current setting signal Is is corrected to a predetermined transition current value Ib and output, and simultaneously, the manipulator RM is moved back to the welding start position Sp and returned to the welding start position Sp, the return signal Rp Thereafter, an operation control signal Mc for moving the manipulator RM in the taught welding direction is output.
[0060]
The operation synchronous robot interface circuit SIFR of the fourth embodiment includes the voltage setting signal Vs, the steady feeding speed setting signal Ws, the output start signal On, the short circuit / arc determination signal Sa, the backward distance matching signal Lp, and the second embodiment. Communicates with the welding power source PS an interface signal If formed from seven signals of different initial current setting signal Is and return signal Rp.
[0061]
The operation synchronous welding power supply interface circuit SIFP of the fourth embodiment communicates an interface signal If formed from the above seven signals with the robot controller RC. The operation-synchronized output control circuit SINV of the fourth embodiment generates a current corresponding to the initial current setting signal Is from the time when the output start signal On is input to the time when the return signal Rp is input. A constant current characteristic or a drooping characteristic to be energized is formed and output, and thereafter, it corresponds to the voltage setting signal Vs for energizing the steady welding current Ic corresponding to the steady feeding speed setting signal Ws. A constant voltage characteristic is formed and output.
[0062]
FIG. 12 is a timing chart of each signal of the robot control device RC and the welding power source device PS of the fourth embodiment described above. FIG. 4A shows the time change of the welding start signal St, FIG. 2B shows the time change of the output start signal On, FIG. 3C shows the time change of the feed control signal Fc, FIG. (D) shows the time change of the short-circuit / arc discrimination signal Sa, FIG. (E) shows the time change of the backward distance coincidence signal Lp, and unlike FIG. 2, (F) shows the return signal Rp. (G) shows the time change of the welding current Iw, (H) shows the time change of the distance Lw between the wire tip and the workpiece, and (I1) to (I5). Indicates the feeding state of the welding wire 1 at each time. In the figure, since the operation before time t5 is the same as that in FIG. 9 described above, description of those periods is omitted. Hereinafter, a period after time t5 different from FIG. 9 will be described.
[0063]
Period after time t5
At time t5, when the distance Lw between the wire tip and the workpiece reaches the setback distance set value Ls due to the backward movement, the backward distance coincidence signal Lp is output (High level) as shown in FIG. In response to this, as shown in FIG. 5C, the feed control signal Fc becomes a positive feed speed setting signal Ws having a positive value, and the welding wire 1 is fed forward to the work piece 2, As shown in FIG. 5G, the welding current Iw changes from the initial current Is to the transition current Ib1. At the same time, when the welding torch 4 is moved back to the welding start position Sp and returned to the welding start position Sp at time t51, a return signal Rp is output (High level) as shown in FIG. Accordingly, the operation synchronous output control circuit SINV described above forms a constant voltage characteristic corresponding to the voltage setting signal Vs, so that the welding voltage (not shown) has a value corresponding to the voltage setting signal Vs, and As shown in (G), a steady welding current Ic having a large current value corresponding to the steady feeding speed Ws is energized.
[0064]
During the return movement period Tb from the time t5 to the time t51, the wire tip is constantly fed by the forward feed at the steady feed speed Ws and the addition of the return movement in the direction of shortening the distance Lw between the wire tip and the workpiece. The workpiece is approached at a speed faster than the feeding speed Ws. For this reason, by applying a predetermined transition current In2 to a value larger than the steady welding current Ic, it is possible to prevent the tip of the wire from penetrating into contact with the workpiece and causing a defective arc start. .
[0065]
[Example 5]
The invention of Example 5 described below corresponds to the invention of claim 5 at the time of filing. In the invention of the fifth embodiment, when the return movement in the invention of the second embodiment is a movement in a direction to shorten the wire tip-to-be-welded distance Lw, the welding wire is fed during the return movement period Tb. After the welding torch returns to the welding start position Sp, the welding wire is fed and the steady welding current Ic is energized after the welding torch returns to the welding start position Sp. This is an arc start control method. The invention of Example 5 will be described below with reference to the drawings.
[0066]
FIG. 13 is a block diagram of the robot controller RC and the welding power source PS for carrying out the arc start control method of the fifth embodiment. In the figure, the same circuit blocks as those in FIG. 11 described above are denoted by the same reference numerals, and description thereof is omitted. The operation synchronous feed control circuit SFC, which is a circuit block different from that shown in FIG. 11 surrounded by a dotted line, will be described below.
[0067]
When the return signal Rp is input, the operation-synchronized feed control circuit SFC according to the fifth embodiment receives a feed control signal Fc that feeds the welding wire forward at a feed speed corresponding to the steady feed speed setting signal Ws. Output.
[0068]
FIG. 14 is a timing chart of each signal of the robot control device RC and the welding power source device PS according to the fifth embodiment. FIG. 4A shows the time change of the welding start signal St, FIG. 2B shows the time change of the output start signal On, FIG. 3C shows the time change of the feed control signal Fc, FIG. (D) shows the time change of the short-circuit / arc discrimination signal Sa, FIG. (E) shows the time change of the backward distance coincidence signal Lp, and unlike FIG. 2, (F) shows the return signal Rp. (G) shows the time change of the welding current Iw, (H) shows the time change of the distance Lw between the wire tip and the workpiece, and (I1) to (I5). Indicates the feeding state of the welding wire 1 at each time. In the figure, since the operation before time t5 is the same as that in FIG. 9 described above, description of those periods is omitted. Hereinafter, a period after time t5 different from FIG. 9 will be described.
[0069]
Period after time t5
At time t5, when the distance Lw between the wire tip and the workpiece reaches the setback distance set value Ls due to the backward movement, the backward distance coincidence signal Lp is output (High level) as shown in FIG. In response to this, as shown in FIG. 5G, the welding current Iw changes from the initial current Is to the transition current Ib2. At the same time, when the welding torch 4 is moved back to the welding start position Sp and returned to the welding start position Sp at time t51, a return signal Rp is output (High level) as shown in FIG. In response to this, as shown in FIG. 5C, the feed control signal Fc becomes a positive feed speed setting signal Ws having a positive value, and the welding wire 1 is fed forward to the work piece 2 while being fed forward. As described above, since the operation synchronous output control circuit SINV forms a constant voltage characteristic corresponding to the voltage setting signal Vs, the welding voltage (not shown) has a value corresponding to the voltage setting signal Vs, as shown in FIG. In addition, a steady welding current Ic having a large current value corresponding to the constant feed speed Ws is energized.
[0070]
During the return movement period Tb from the time t5 to the time t51, the feeding of the welding wire remains stopped. However, the return of the wire in the direction of shortening the distance Lw between the wire tip and the workpiece to be welded causes the wire tip to be welded. Get closer to. For this reason, by applying a predetermined transition current Ib2 corresponding to the speed of the return movement, it is possible to prevent the wire tip from being pushed into contact with the workpiece and causing a defective arc start.
[0071]
In the embodiment described above, the case where the manipulator of the welding robot is used as the moving means of the welding torch has been described. However, an XY table used in an automatic bogie or NC processing machine capable of moving a welding torch and / or a workpiece to be welded in the vertical direction of the welding wire feed direction and the horizontal direction of the welding direction. Etc. can be used to implement the present invention.
[0072]
【The invention's effect】
In the arc start control method of the present invention, the first response delay time T11 when the welding torch starts moving backward and the second response delay time T21 when the welding wire starts moving forward can be shortened. It is possible to prevent poor welding due to an increase in arc length during the delay time and a decrease in productivity due to a response delay time, and always perform a good arc start.
Furthermore, in the inventions of Embodiments 2 and 3, in addition to the above-described effects, when the distance Lw between the wire tip and the workpiece to be welded when the welding torch first arrives at the welding start position Sp is very short or in contact therewith. Even in such a case, since the backward movement is continued until the appropriate backward distance set value Ls is reached, it is possible to prevent the arc start failure due to the absence of the initial arc caused by the short backward distance and the disappearance immediately after the occurrence.
Furthermore, in the inventions of the fourth and fifth embodiments, in addition to the above-described effects, by applying an appropriate transition current Ib corresponding to the speed at which the wire tip approaches the work piece during the return movement period Tb, It is possible to prevent arc start failure due to the plunging into the work piece.
[Brief description of the drawings]
FIG. 1 is a timing chart of a robot arc welding apparatus illustrating an embodiment of the present invention.
FIG. 2 is a block diagram of a conventional robot arc welding apparatus.
FIG. 3 is a block diagram of a conventional apparatus.
FIG. 4 is a timing chart of each signal of a conventional device.
FIG. 5 is a timing chart showing a problem to be solved in the prior art
FIG. 6 is a block diagram of the first embodiment.
FIG. 7 is a timing chart of each signal in the first embodiment.
FIG. 8 is a block diagram of the second embodiment.
FIG. 9 is a timing chart of each signal according to the second embodiment.
FIG. 10 is a timing chart of signals in Example 3.
FIG. 11 is a block diagram of the fourth embodiment.
FIG. 12 is a timing chart of signals in Example 4.
FIG. 13 is a block diagram of the fifth embodiment.
FIG. 14 is a timing chart of signals in Example 5.
[Explanation of symbols]
1 Welding wire
2 Workpiece
3 Arc
3a Initial arc (occurrence state)
3b Steady arc (occurrence state)
3c Arc with excessive arc length
4 Welding torch
4a Coil liner
DT delay circuit
Dt delay signal
Fc feed control signal
Ib, Ib1, Ib2 transition current
If interface signal
IFP welding power interface circuit
IFR robot interface circuit
INV output control circuit
Is Initial current (setting signal)
Iw welding current
Lp Backward distance coincidence signal
Ls Setback distance setting value
Lw Distance between wire tip and workpiece
MC operation control circuit
Mc operation control signal
On output start signal
PS welding power supply
RC robot controller
RFC forward / reverse feed control circuit
RM manipulator
Rp return signal
SA short-circuit / arc discrimination circuit
Sa short / arc discrimination signal
SFC operation synchronous feed control circuit
SIFP operation synchronous welding power interface circuit
SIFR motion synchronous robot interface circuit
SINV operation synchronous output control circuit
Sp welding start position
St welding start signal
T1, T11 First response delay time
T2, T21 Second response delay time
Tb Return movement period
Td delay time
VD voltage detection circuit
Vd Voltage detection signal
Vs Voltage setting signal
Vw welding voltage
Wi initial feed speed setting value
WM wire feed motor
Wr Reverse feed speed setting value
Ws Regular feed speed (setting signal)

Claims (5)

A consumable electrode type robot arc welding in which a welding voltage is applied by a welding power source device to generate an arc between the welding wire and the workpiece, and a welding torch attached to the manipulator of the welding robot is moved to perform welding. In
When a welding start signal is input, the welding torch is moved to a welding starting position taught in advance, and after reaching the welding starting position, the welding torch is moved substantially in the welding wire feeding direction to move the wire tip. When approaching the workpiece and determining that the tip of the wire is in contact with the workpiece, an initial current having a predetermined small current value is supplied from the welding power source device and the welding torch is substantially connected to the welding wire. An initial arc in which the initial current is energized when the wire tip is moved backward in a direction opposite to the feeding direction to move the wire tip away from the workpiece, and the wire tip and the workpiece are separated by the backward movement. When the initial arc generation state is maintained and the backward movement is continued and the welding torch returns to the welding start position, the backward movement is taught in advance. Switching to the movement in the welding direction, simultaneously starting the feeding of the welding wire and energizing the steady welding current to smoothly transition from the initial arc generation state to the steady arc generation state. Arc start control method. A consumable electrode type robot arc welding in which a welding voltage is applied by a welding power source device to generate an arc between the welding wire and the workpiece, and a welding torch attached to the manipulator of the welding robot is moved to perform welding. In
When a welding start signal is input, the welding torch is moved to a welding starting position taught in advance, and after reaching the welding starting position, the welding torch is moved substantially in the welding wire feeding direction to move the wire tip. When approaching the workpiece and determining that the tip of the wire is in contact with the workpiece, an initial current having a predetermined small current value is supplied from the welding power source device and the welding torch is substantially connected to the welding wire. An initial arc in which the initial current is energized when the wire tip is moved backward in a direction opposite to the feeding direction to move the wire tip away from the workpiece, and the wire tip and the workpiece are separated by the backward movement. Occurs, the backward movement is continued while maintaining the initial arc generation state, and the backward movement is performed when the distance between the wire tip and the workpiece reaches a predetermined backward distance set value. Switching to the return movement to the welding start position, simultaneously starting feeding the welding wire and energizing a steady welding current. After returning to the welding start position, the welding torch is taught in advance. An arc start control method for robot arc welding that smoothly shifts from the initial arc generation state to a steady arc generation state by moving in a direction. 3. The arc start control method according to claim 2, wherein the feeding start of the welding wire and the start of energization of the steady welding current are performed from the time when the welding torch returns to the welding start position by the return movement. 3. The arc start according to claim 2, wherein when the return movement is a movement in a direction of shortening the distance between the wire tip and the work piece, an arc current having a current value larger than a steady welding current is applied during the return movement period. Control method. When the return movement is a movement in the direction of shortening the distance between the wire tip and the workpiece, it is determined in advance corresponding to the speed of the return movement while the feeding of the welding wire is stopped during the return movement period. 3. The arc start control method according to claim 2, wherein after the welding current is turned on and the welding torch returns to the welding start position, feeding of the welding wire is started and a steady welding current is passed.

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