JP2002178146A - Arc start control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that arc start becomes defective by welding owing to the generation of an initial arc 3a when a welding wire 1 comes into contact with an object 2 to be welded, in an arc start control method wherein the welding wire 1 is advanced to the object 2 when a welding start signal St is inputted, an initial current Is of a small current value is made to flow when the welding wire 1 comes into contact with the object 2 and also the welding wire 1 is withdrawn from the object 2, the welding wire 1 is advanced again at a steady speed and also a stationary welding current Iw is made to flow when the welding wire 1 leaves the object 2 by the withdrawal and the initial arc 3a is generated. SOLUTION: In this method, an intermittent feeding operation (time t1-t11) wherein the welding wire 1 is advanced only for a preliminarily decided intermittent feeding time Ti without applying a welding voltage Vw and a contact discriminating operation (time t11-t12) wherein contact is discriminated by stopping the above advance and applying the welding voltage Vw are added, thereby preventing weld at the contact time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a consumable electrode gas shielded arc welding system in which a welding wire is fed forward and backward by a wire feed motor capable of forward and reverse rotation to start an arc. It relates to a start control method.

[0002]

2. Description of the Related Art A wire feed motor is rotated forward to feed a welding wire forward to a workpiece, and when it is determined that the welding wire has come into contact with the workpiece, the wire feeding motor is rotated in a reverse direction. The welding wire is fed backward, and at the same time, an initial current Is having a small current value is applied. When the welding wire is separated from the workpiece by the backward feeding and an initial arc is generated, the welding wire is fed at a steady feeding speed. Conventionally, there has been known an arc start control method of consumable electrode gas shielded arc welding in which the feed is forwarded again, and at the same time, a steady welding current is applied to start the arc. Hereinafter, this conventional arc start control method will be described with reference to the drawings.

FIG. 2 is a schematic diagram showing a welding wire feeding system. The welding wire 1 is fed through the welding torch 4 by a feed roll 5a directly connected to the wire feed motor WM. When the wire feed motor WM rotates forward, the welding wire 1 is fed forward to the workpiece 2, and when the wire feed motor WM rotates reversely, the welding wire 1 is fed backward from the workpiece 2. The welding voltage Vw from the welding power supply PS is supplied to the welding wire 1 by a contact tip 4 a attached to the tip of the welding torch 4. Then, a contact (short circuit) occurs between the welding wire 1 and the workpiece 2.
In a state or an arcing state, the welding current Iw is conducted, and in a no-load state, the welding voltage Vw becomes the no-load voltage Vnl and the welding current Iw is not conducted. The shortest distance between the tip of the welding wire 1 and the work 2 is the distance Lw [mm] between the wire tip and the work. Therefore, the distance Lw between the tip of the wire and the workpiece to be welded during the arc is equal to the arc length.

FIG. 3 illustrates a block diagram of a welding power supply device for implementing the above-described conventional arc start control method. Hereinafter, each circuit block will be described with reference to FIG.

The voltage detection circuit VD detects a welding voltage Vw and outputs a voltage detection signal Vd. The short-circuit / arc discrimination circuit SA receives the voltage detection signal Vd as input and outputs a short-circuit signal (High level) when the welding wire 1 and the workpiece 2 are in contact with each other, and outputs an arc when an arc is generated. An occurrence signal (Low level) is output as a short circuit / arc determination signal Sa. However, as described later, in order to delay the timing of switching to forward feeding after the initial arc is generated, the short-circuit / arc discrimination signal Sa is turned off by a predetermined delay time Td when the change point from the short-circuit signal to the arc generation signal is changed. The result is a delayed signal.

[0006] The steady feed speed setting circuit WS outputs a steady feed speed setting signal Ws. The feed control circuit FC
When a welding start signal St is input (High level) from the outside, the welding wire 1 is forwardly fed to the workpiece 2 at an initial feeding speed corresponding to a predetermined initial feeding speed set value Wi, and then continuously. When the short-circuit / arc discrimination signal Sa becomes a short-circuit signal, the welding wire 1 is fed backward from the workpiece 2 at a backward feeding speed corresponding to a predetermined backward feeding speed set value Wr. When the short circuit / arc discrimination signal Sa becomes an arc generation signal, the welding wire 1 is again forward-fed to the workpiece 2 at a steady feeding speed corresponding to the steady feeding speed setting signal Ws. It outputs a feed control signal Fc. The wire feed motor WM feeds the welding wire 1 forward or backward according to the feed control signal Fc, as described above in the description of FIG.

The voltage setting circuit VS outputs a voltage setting signal Vs for setting the welding voltage Vw of the welding power supply PS.
The output control circuit INV is connected to a commercial power supply (usually a three-phase 200
With V) as input, a welding voltage Vw and a welding current Iw suitable for maintaining the arc 3 stably are output by inverter control, thyristor phase control, and the like. The output control circuit INV has a predetermined small current value between the time when the welding start signal St is input from the outside and the time when the short circuit / arc discrimination signal Sa changes from the short circuit signal to the arc generation signal. The above-mentioned voltage setting signal Vs for supplying a steady welding current corresponding to the above-mentioned steady feed speed setting signal Ws after forming and outputting a constant current characteristic or a drooping characteristic for passing the initial current Is. Is formed and output.

FIG. 4 shows the welding power supply device PS described in FIG.
3 is a timing chart of each signal of FIG. FIG. 7A shows the time change of the welding start signal St, and FIG. 7B shows the time change of the feed control signal Fc, and FIG.
Indicates a time change of the short circuit / arc discrimination signal Sa,
FIG. 3D shows the time change of the welding voltage Vw, FIG. 3E shows the time change of the welding current Iw, and FIG. 3F shows the change of the distance Lw between the wire tip and the workpiece. The time changes are shown, and FIGS. (G1) to (G5) show the feeding state of the welding wire 1 at each time. Hereinafter, description will be made with reference to FIG.

[0009] Period from time t1 to t2 At time t1, as shown in FIG. 1A, when the welding start signal St is input from outside (High level),
As shown in FIG. 7B, the feed control signal Fc becomes a positive initial feed speed set value Wi, and the welding wire 1 is initially sent to the workpiece 2 as shown in FIG. It is fed forward at the feed rate. When the feed control signal Fc has a positive value, forward feed is performed, and when the feed control signal Fc has a negative value, reverse feed is performed. At the same time, as described above in the description of FIG. 3, the output control circuit I
The NV forms and outputs a constant current characteristic or a drooping characteristic. During this period, since the welding wire 1 and the workpiece 2 are separated and in a no-load state, as shown in FIG. A no-load voltage Vnl is applied. During the period from time t1 to t2, the distance Lw between the wire tip and the workpiece is gradually reduced due to the above-described forward feeding, as shown in FIG.

[0010] Period from time t2 to t3 At time t2, as shown in FIG. 2G, when the welding wire 1 comes into contact with the workpiece 2 by the above-described forward feeding, as shown in FIG. Then, the short circuit / arc determination signal Sa changes to a short circuit signal (High level). In response to this change, as shown in FIG.
c is a negative value of the backward feed speed set value Wr, and the welding wire 1 is fed backward from the workpiece 2 at the backward feed speed.
At the same time, as shown in FIG. 2D, the welding voltage Vw becomes a very small value of several [V] because the welding wire and the workpiece are in contact with each other, and as shown in FIG. As described above, the initial current Is having a small current value flows due to the constant current characteristic or the drooping characteristic described above. 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 time t2 to time t3, the welding wire 1 is fed backward, but the wire feeding motor WM shown in FIG.
The welding wire 1 and the workpiece 2 remain in contact with each other due to the response delay time of the reversal of the welding wire 1 and the time required for the backward feeding of the play due to the bending of the welding wire 1 in the welding torch. Therefore, as shown in FIG. 5F, the distance Lw between the tip of the wire and the workpiece remains 0 [mm] during this period.

[0011] At time t3, at time t3, when the welding wire 1 and the workpiece 2 are separated by the backward feeding as shown in FIG. Initial arc 3a
Occurs. When the initial arc 3a occurs, FIG.
As shown in (1), the welding voltage Vw has a value corresponding to the arc length of the initial arc 3a (the distance Lw between the tip of the wire and the workpiece). Further, from time t3 when the initial arc 3a occurs to time t4 when the above-described delay time Td elapses,
As shown in FIG. 3C, the short-circuit / arc determination signal Sa remains the short-circuit signal (High level). During this time, the backward feeding is continued while the initial arc occurrence state 3a is maintained, as shown in FIG. Therefore, as shown in FIG. 3F, the distance Lw between the tip of the wire and the workpiece is gradually increased.

At time t4, at time t4, when the short-circuit / arc determination signal Sa changes from the short-circuit signal (High level) to the arc generation signal (Low level) as shown in FIG. As shown in B), the feed control signal Fc becomes a positive value steady feed speed setting signal Ws, and the welding wire 1 is fed forward to the workpiece 2 again at the steady feed speed. at the same time,
As described above in the description of FIG. 3, the output control circuit INV
Forms a constant voltage characteristic corresponding to the voltage setting signal Vs, so that the welding voltage Vw has a value corresponding to the voltage setting signal Vs as shown in FIG.
As shown in (1), a steady welding current having a large current value corresponding to the steady feed speed is supplied. Therefore, the transition from the initial arc 3a shown in FIG. (G4) to the steady arc 3b shown in (G5) is made, and as shown in FIG. (F), the distance Lw between the wire tip and the workpiece is also increased. A steady arc length corresponding to the voltage setting signal Vs is obtained.

[0013]

FIG. 5 is a timing chart corresponding to FIG. 4 for explaining the problem to be solved in the prior art. FIG. 6A shows the time change of the welding start signal St, and FIG. 6B shows the feed control signal Fc.
(C) shows the time change of the short-circuit / arc discrimination signal Sa, and FIG. (D) shows the time change of the welding voltage Vw, and FIG. Shows the time change of the welding current Iw, FIG. (F) shows the time change of the distance Lw between the tip of the wire and the workpiece, and FIGS. (G1) to (G4) show the welding wire at each time. 1 shows a feeding state. Hereinafter, description will be made with reference to FIG.

As in the case of FIG. 4, at time t1,
When the welding start signal St is externally input (High level) as shown in FIG. 7A, the feed control signal Fc becomes a positive initial feed speed as shown in FIG. It becomes the set value Wi, and as shown in FIG.
Is fed forward to the workpiece 2 at the initial feeding speed. At the same time, as in the case of FIG. 4, the output control circuit INV forms a constant current characteristic or a drooping characteristic and outputs it. At this point, since the load is in a no-load state, as shown in FIG.
A no-load voltage Vnl of a high voltage value of about [V] is applied.

With the elapse of time by the above-mentioned forward feeding,
As shown in FIG. 4F, the distance Lw between the wire tip and the workpiece is gradually reduced. At time t11, when the tip end of the wire and the workpiece 2 are very close to each other, the no-load voltage V of the high voltage value as shown in FIG.
In some cases, the initial arc 3a is generated by nl, and in this case, the initial current Is flows as shown in FIG. Since the forward feeding is continued with the initial arc 3a generated, the welding wire 1 and the workpiece 2 come into contact at time t2, and the initial arc 3a disappears. At this time, the wire tip and the workpiece 2 are melted by the initial arc 3a during the above period (time t11 to t2) as shown in FIG. Disappears, the tip of the wire welds to the workpiece 2 (hereinafter, this phenomenon is referred to as welding during contact).

On the other hand, as shown in FIG.
, The short-circuit / arc determination signal Sa is the short-circuit signal
gh level), and the backward feeding of the welding wire 1 is started. However, since the wire tip is welded and the welding wire 1 and the workpiece 2 do not separate, the initial arc 3a does not occur forever. Therefore, even at time t21 after a long time has elapsed from time t2, the feed control signal Fc shown in FIG.
r, the short circuit / arc discrimination signal Sa shown in FIG. 4C remains the short circuit signal, and the welding voltage Vw shown in FIG. 4D remains at a value of several [V]. The same figure (E)
Is the initial current value Is, and the distance Lw between the wire tip and the workpiece shown in FIG.
[G], and the welding wire 1 is still welded to the workpiece 2 as shown in FIG. This results in arc start failure.

The above-mentioned welding at the time of contact is likely to occur when the work to be welded is steel or stainless steel, and the frequency of occurrence is low when the work is aluminum or an alloy thereof. Further, in the case of steel, for example, welding occurs even when the initial current value Is is a very small value of several [A]. When the initial current value Is is about 10 [A] or more, welding occurs at a very high frequency. Even if the initial current value Is is set to several [A] at this time, when the initial arc 3a is generated at the time t11 and the initial current Is starts to be supplied, the overshoot causes a short time of several tens of [A]. A] Since the above-mentioned current flows and the melting of the wire tip is promoted, welding occurs.

Therefore, the present invention provides an arc start control method capable of reliably performing a good arc start without causing the above-mentioned welding at the time of contact.

[0019]

According to the first aspect of the present invention, as shown in FIGS. 6 to 8, when a welding start signal St is input to the welding power source PS, the welding power source PS While the output is stopped, the welding wire 1 is forward-fed to the workpiece 2 for a predetermined intermittent feeding time Tj, and then the output of the welding power supply device PS is started to cause the welding wire 1 to be welded to the workpiece 2. It is determined whether or not the object 2 is in contact. If the object 2 is not in contact, the output of the welding power supply PS is stopped, and the welding power supply PS is again fed forward for the intermittent feeding time Ti. The output is started and the intermittent feed contact determination operation for determining whether the welding wire 1 is in contact with the workpiece 2 is repeated until the welding wire 1 and the workpiece 2 are in contact with each other. The above welding is performed by the intermittent feeding contact When it is determined that the ear 1 and the workpiece 2 are in contact with each other, an initial current Is having a predetermined small current value is supplied from the welding power supply PS and the welding wire 1 is retracted from the workpiece 2. When the welding wire 1 is separated from the workpiece 2 by the backward feeding, an initial arc 3a through which the initial current Is flows is generated, and after the initial arc 3a is generated, the welding wire 1 is A steady arc is generated from the initial arc generation state 3a by feeding the workpiece 2 forward again at the determined steady feed rate and applying a steady welding current Iw corresponding to the steady feed rate. This is an arc start control method for consumable electrode gas shielded arc welding that smoothly transitions to state 3b.

The invention of claim 2 at the time of filing is shown in FIGS.
0, a welding start signal St is sent to the welding power supply PS.
Is input, the welding wire 1 is forwardly fed to the workpiece 2 by a predetermined intermittent feed distance Ls while the output of the welding power source PS is stopped, and then the welding power source PS is stopped.
Is started to determine whether the welding wire 1 and the workpiece 2 are in contact with each other. If not, the output of the welding power supply PS is stopped and the intermittent feeding distance Ls is returned again. The intermittent feed contact determination operation of starting the output of the welding power supply PS after starting the forward feed and determining whether the welding wire 1 is in contact with the workpiece 2 is performed by the welding power supply PS. It repeats until the welding object 2 comes into contact, and when it is determined that the welding wire 1 has come into contact with the workpiece 2 by the intermittent feeding contact determining operation, the initial current Is having a predetermined small current value is determined. When the welding power supply PS is energized, the welding wire 1 is backwardly fed from the workpiece 2, and when the welding wire 1 is separated from the workpiece 2 by the backward feeding, the initial current Is is increased.
Is generated, an initial arc 3a is generated.
After the occurrence of “a”, the welding wire 1 is forwardly fed again to the workpiece 2 at a predetermined steady feeding speed, and a steady welding current Iw corresponding to the steady feeding speed is supplied. This is an arc start control method for consumable electrode gas shielded arc welding that smoothly transitions from the initial arc generation state 3a to the steady arc generation state 3b.

As shown in FIGS. 6 to 9, the invention of claim 3 at the time of filing applies the intermittent feed time Ti described in claim 1 at the time of filing, from the outside of the welding power supply PS. An arc start control method according to claim 1.

The invention of claim 4 at the time of filing is shown in FIGS.
As shown in FIG. 0, the arc start control method according to claim 2 at the time of application, wherein the intermittent feeding distance Ls described in claim 2 at the time of application is set from outside the welding power supply device PS.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1 (the same drawing as FIG. 8), an embodiment of the present invention is configured such that when a welding start signal St is input (time t1) to the welding power supply device, With the output of the welding power supply stopped, the output of the welding power supply is started after the welding wire 1 is forward-fed to the workpiece 2 for a predetermined intermittent feeding time Tj (time t1 to t11). Then, it is determined whether the welding wire 1 is in contact with the workpiece 2 (time t11 to t12). If not, the output of the welding power supply is stopped and the intermittent feeding time is resumed. The intermittent feeding contact determination operation for starting the output of the welding power supply device after the forward feeding only during Ti and determining whether the welding wire 1 and the workpiece 2 are in contact with each other is performed with the welding wire 1. Repeatedly until the workpiece 2 comes into contact with the workpiece 2, When it is determined that the welding wire 1 and the workpiece 2 are in contact with each other by the intermittent feeding contact determination operation (time t2), an initial current Is having a predetermined small current value is supplied from the welding power supply device. At the same time, the welding wire 1 is backwardly fed from the workpiece 2, and when the welding wire 1 is separated from the workpiece 2 by the backward feeding, an initial arc 3 a in which the initial current Is flows is generated. After the initial arc 3a is generated (time t4), the welding wire 1 is again forward-fed to the workpiece 2 at a predetermined steady-state feeding speed, and steady welding corresponding to the steady-state feeding speed is performed. When the current Iw is supplied, the initial arc occurrence state 3a is changed to the steady arc occurrence state 3
This is an arc start control method for consumable electrode gas shielded arc welding that smoothly shifts to b.

[0024]

[Embodiment 1] The invention of Embodiment 1 described below corresponds to the inventions of Claims 1 and 3 at the time of filing.
The invention of the first embodiment is an arc start control method in which the forward feeding operation for bringing a welding wire into contact with an object to be welded in the prior art described above is replaced with the following intermittent feeding contact determination operation. That is, when a welding start signal is input from the outside, the welding wire is forward-fed to the workpiece while the output of the welding power supply is stopped for a predetermined intermittent feed time Tj, Is started to determine whether the welding wire is in contact with the work to be welded. If not, the output of the welding power supply device is stopped and the feed is forwarded again only for the intermittent feed time Ti. After that, the output of the welding power supply device is started, and the intermittent feed contact determination operation for determining whether the welding wire is in contact with the workpiece is repeated until the welding wire contacts the workpiece.

The subsequent operation is the same as that of the above-mentioned prior art. That is, when it is determined that the welding wire has come into contact with the work to be welded by the intermittent feeding contact determination operation, an initial current Is having a predetermined small current value is supplied from the welding power supply device and the welding wire is welded. When the welding wire is separated from the workpiece by the backward feeding, an initial arc in which the initial current Is flows is generated. At the time when the initial arc occurs, the welding wire is fed in a predetermined steady state. A consumable electrode that feeds forward again to the workpiece at the feed rate and smoothly transitions from the initial arcing state to the steady arcing state by applying a steady welding current corresponding to the steady feeding rate. This is an arc start control method for gas shielded arc welding. Hereinafter, Example 1
The invention will be described with reference to the drawings.

FIG. 6 is a block diagram of a welding power supply for implementing the arc start control method of the first embodiment.
In this figure, the same circuit blocks as those in FIG. 3 described above are denoted by the same reference numerals, and description thereof will be omitted. Hereinafter, the intermittent feed time setting circuit TI and the output start / feed control circuit OF which are circuit blocks different from those in FIG.
C and the output control circuit INV will be described.

The intermittent feed time setting circuit TI outputs an intermittent feed time setting signal Ti having a predetermined time length. The value of the intermittent feed time setting signal Ti depends on the material and diameter of the welding wire, the welding method (carbon dioxide arc welding, pulse arc welding, etc.), the material and shape of the workpiece, the welding speed, the steady feeding speed, the initial It is set to an appropriate value according to the feeding speed and the like.
Further, it is the invention of claim 3 at the time of application that the intermittent feed time setting signal Ti is set to an arbitrary value from an external control device such as a welding robot control device.

The output start / feed control circuit OFC receives the welding start signal St and the short circuit / arc discrimination signal Sa, and outputs an output start signal On and a feed control signal Fc in accordance with a control algorithm described later with reference to FIG. The output control circuit INV receives the output start signal On and the short-circuit / arc discrimination signal Sa as inputs, and when the output start signal On is input (High level), a predetermined initial current Is is supplied. A current characteristic or a drooping characteristic is formed and output. When the output start signal On is not input (Low level), the output is stopped, and the output start signal On is input, and After the point at which the short-circuit / arc determination signal Sa changes from the short-circuit signal to the arc generation signal, the steady-state feed speed setting signal Ws
And outputs a constant voltage characteristic corresponding to the voltage setting signal Vs for supplying a steady welding current corresponding to.

FIG. 7 is a flowchart showing a control algorithm at the time of arc start of the output start / feed control circuit OFC. Hereinafter, description will be made with reference to FIG.
In step ST1, the welding start signal St is set to Hig.
It is determined whether the signal is at the h level (whether it is input). If YES, the process proceeds to the next step ST2. If NO, the process of this step is repeated. In step ST2, the output start signal On is set to Low level (output stop),
The feed control signal Fc is output as the initial feed speed set value Wi. In step ST3, the above-mentioned step ST2
It is determined whether or not the time determined by the intermittent feed time setting signal Ti has elapsed from the time of the processing of (1). If YES, the process proceeds to the next step ST4, and if NO, the process of this step is repeated. By the processes of steps ST2 and ST3, the welding wire is fed forward only during the intermittent feeding time Ti while the output of the welding power supply is stopped.

In step ST4, the feed control signal F
c is set to zero to output (feeding is stopped), and the output start signal On is set to a high level (output start). In step ST5, the short-circuit / arc determination signal Sa is set to High.
It is determined whether the level is a level (short-circuit signal). If YES, the process proceeds to the next step ST6.
Return to The intermittent feeding contact determination operation is performed by the processing of steps ST2 to ST5 described above.

The processing of the subsequent steps is the same as that of the above-described prior art. In step ST6,
The feed control signal Fc is set to the reverse feed speed set value Wr and output. By this processing, when the short-circuit / arc discrimination signal Sa becomes a short-circuit signal (contact between the welding wire and the workpiece), the backward feeding of the welding wire is started, and the output start signal On is still output. Therefore, the initial current Is flows. In step ST7, it is determined whether the short-circuit / arc determination signal Sa is at a low level (arc generation signal). If YES, the process proceeds to the next step ST8, and if NO, the process of this step is repeated. In step ST8, the feed control signal Fc is changed to the steady feed speed setting signal Ws.
And output it. With this process,
When the short circuit / arc discrimination signal Sa becomes an arc generation signal, re-advancing feeding of the welding wire is started, and a steady welding current is supplied because the output start signal On is still output.

FIG. 8 is a timing chart of each signal in the welding power supply PS of the first embodiment. FIG. 6A shows the time change of the welding start signal St, and FIG. 6B shows the time change of the feed control signal Fc.
FIG. 3C shows the time change of the output start signal On, FIG. 3D shows the time change of the short circuit / arc discrimination signal Sa, and FIG. 3E shows the time change of the welding voltage Vw. FIG. (F) shows the time change of the welding current Iw, and FIG. (G) shows the distance L between the wire tip and the workpiece.
(H1) to (H6) show the feeding state of the welding wire 1 at each time. In the figure, the operation in the period after time t2 is the same as that in FIG. 4 described above, and the description of those periods will be omitted. Hereinafter, an operation in a period from time t1 to time t2 different from that in FIG. 4 will be described with reference to FIG.

During the period from time t1 to t11 (intermittent feeding operation) At time t1, when the welding start signal St is input (High level) as shown in FIG. Thus, the feed control signal Fc becomes the initial feed speed set value Wi only for the predetermined intermittent feed time Ti (time t1 to t11), and as shown in FIG. Is not output (Low level). For this reason, since the output of the welding power supply is stopped, the welding wire 1 moves forward only during the above-mentioned intermittent feeding time Ti without applying the welding voltage Vw, as shown in FIG. Will be sent. Therefore, as shown in FIG.
The distance Lw between the wire tip and the workpiece is gradually reduced.

The period from time t11 to t12 (contact determination operation) The intermittent feeding time Ti from the input of the welding start signal St
At time t11 after the lapse, the feed control signal Fc becomes zero as shown in FIG. 7B, and the output start signal On is output (High level) as shown in FIG. For this reason, the output of the welding power supply device is started in a state where the forward feeding of the welding wire 1 is stopped. However, at this point, since the welding wire 1 and the workpiece 2 are separated and in a no-load state, the welding voltage Vw becomes the no-load voltage Vnl as shown in FIG. ), The welding current Iw is not supplied. Further, as shown in FIG. 3G, the distance Lw between the tip of the wire and the workpiece does not change because forward feeding is stopped. further,
As shown in FIG. 3D, the short-circuit / arc determination signal Sa
Does not output the short-circuit signal (High level) because the welding wire 1 and the workpiece 2 are separated from each other.

The period from time t12 to time t13 (second intermittent feeding operation) Since the short-circuit / arc determining signal Sa does not change to a short-circuit signal in the contact determining operation of the above item, the intermittent feeding operation of the above item is performed again. Do. The period from time t13 to t14 (second contact discriminating operation) Even at time t13, the welding wire 1 and the workpiece 2 are still separated from each other. As shown in D), even during this period, the short-circuit / arc determination signal Sa does not change to a short-circuit signal.

The period from time t14 to t2 (third intermittent feeding operation) By the same intermittent feeding operation as described above, FIG.
As shown in FIG. 1, the welding wire 1 comes into contact with the workpiece 2.
At this time, the output of the welding power supply is stopped,
The initial arc 3a never occurs at the time of contact,
As a result, the welding wire 1 does not adhere to the workpiece 2.

After time t 2 When it is determined at the time t 2 that the welding wire 1 has come into contact with the workpiece 2 by the same contact determination operation as described above, the short-circuit / arc determination is performed as shown in FIG. The signal Sa changes to a short-circuit signal (High level). The subsequent operations are the same as those in FIG.

[Embodiment 2] The invention of Embodiment 2 described below corresponds to the inventions of Claims 2 and 4 at the time of filing. In the above-described first embodiment, the welding wire is fed forward only during the predetermined intermittent feeding time Ti. However, in the second embodiment, the welding wire is fed in the predetermined intermittent feeding distance L.
Feed forward by s. Except for this point, the invention of the first embodiment and the invention of the second embodiment are the same. Hereinafter, the second embodiment will be described with reference to the drawings.

FIG. 9 is a block diagram of a welding power supply device for implementing 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 will be omitted. Hereinafter, the feeding speed detection circuit WD, the feeding speed integration circuit WDI, the intermittent feeding distance setting circuit LS, and the output start / feed control circuit OFC which are circuit blocks different from those in FIG.
Will be described.

The feed speed detection circuit WD detects the feed speed Wf and outputs a feed speed detection signal Wd. As the detection method, there is a method in which an encoder, a tachogenerator, or the like is attached to the wire feed motor WM and an output signal thereof is used, or a method in which the armature voltage of the wire feed motor WM is used as a detection signal. The feed speed integrating circuit WDI integrates the feed speed detection signal Wd to output a feed distance signal Wdi, and resets the integrated value when a reset signal Rs described later is input.

The intermittent feed distance setting circuit LS outputs a predetermined intermittent feed distance setting signal Ls. The value of the intermittent feed distance setting signal Ls is the same as the value of the above-mentioned intermittent feed time Ti, the material and diameter of the welding wire, the welding method, the material and shape of the workpiece, the welding speed, and the steady feed. It is set to an appropriate value according to the speed, the initial feeding speed, and the like. It is the invention of claim 4 at the time of application that the intermittent feed distance setting signal Ls is set to an arbitrary value from an external control device such as a welding robot control device.

Output start / feed control circuit OFC of Embodiment 2
Receives a welding start signal St, a short circuit / arc discrimination signal Sa, and a feed distance signal Wdi, and outputs an output start signal On, a feed control signal Fc, and a reset signal Rs in accordance with a control algorithm described later with reference to FIG.

FIG. 10 is a diagram showing the start of output of the second embodiment.
It is a flowchart which shows the control algorithm at the time of the arc start of the feed control circuit OFC. In this figure, the same steps as those in FIG.
Their description is omitted. Hereinafter, steps ST31 and ST41 different from FIG. 7 will be described with reference to FIG.

In step ST31, it is determined whether or not the forward feed distance of the welding wire by the processing in step ST2 has reached the distance determined by the intermittent feed distance setting signal Ls. If YES, the process proceeds to the next step ST41. If NO, the process of this step is repeated. By the processes in steps ST2 and ST31, the welding wire is fed forward by the intermittent feeding distance Ls while the output of the welding power supply is stopped.

In step ST41, a reset signal Rs is output, the feed control signal Fc is set to zero and output (feed is stopped), and the output start signal On is set to a high level (output start). With this processing, the integrated value of the above-described feed speed integration circuit WDI is reset, and the contact determination operation is performed.

[Effect] FIG. 11 is a comparison diagram of the welding rate showing the effect of the present invention. This figure is an example of an experimental result in which the frequency of occurrence of welding at the time of contact (welding rate) was compared between the prior art and the present invention under the following experimental conditions. As the experimental conditions, a mild steel wire having a diameter of 1.2 [mm] was used as the welding wire, the initial current Is was set to 5 [A], and carbon dioxide arc welding was used for the welding method, and 100 arc starts were performed. The test was performed. The figure shows the number of times welding has occurred at the time of contact in 100 arc starts. As is clear from the drawing, welding at the time of contact occurred as much as 22% in the prior art, but no welding occurred at the time of contact in the present invention. Further, the welding rate increases in the prior art in proportion to the increase in the value of the initial current Is, but in the present invention, welding does not occur at the time of contact regardless of the value of the initial current Is.

[0047]

According to the present invention, the occurrence of welding at the time of contact between the welding wire and the workpiece can be prevented by the arc start control method involving the intermittent feeding contact determination operation, so that good arc start performance can be obtained. Can be obtained. Furthermore, in the present invention, the above-described effects are obtained even when the work to be welded is various metals such as steel, stainless steel, and aluminum alloy. Further, the present invention has the above-mentioned effects irrespective of the value of the initial current Is. Claim 3 at the time of application
In the invention according to claim 4, the intermittent feed time Ti or the intermittent feed distance Ls is determined from the external control device by the material and diameter of the welding wire, the welding method, the material and shape of the workpiece, the welding speed, and the steady feeding speed. Since it can be set to an appropriate value according to the initial feeding speed and the like, it is possible to prevent the occurrence of welding at the time of contact even under various welding conditions, and to always obtain good arc start performance.

[Brief description of the drawings]

FIG. 1 is a timing chart of a welding power supply device illustrating an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a welding wire feeding system.

FIG. 3 is a block diagram of a conventional device.

FIG. 4 is a timing chart of each signal of the 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 welding power supply device according to the first embodiment.

FIG. 7 is a flowchart of an intermittent feeding contact determination operation according to the first embodiment.

FIG. 8 is a timing chart of each signal of the welding power supply device according to the first embodiment.

FIG. 9 is a block diagram of a welding power supply device according to a second embodiment.

FIG. 10 is a flowchart of an intermittent feeding contact determination operation according to the second embodiment.

FIG. 11 is a welding rate comparison diagram showing the effect of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Welding wire 2 Workpiece 3a Initial arc (generation state) 3b Steady arc (generation state) 4 Welding torch 4a Contact tip 5a Feeding roll of wire feeder FC feed control circuit Fc feed control signal INV output control Circuit Is Initial current (value / set value) LS Intermittent feed distance setting circuit Ls Intermittent feed distance (setting signal) Lw Distance between wire tip and work piece OFC output start / feed control circuit On output start signal PS Welding power Device Rs Reset signal SA Short circuit / arc discriminating circuit Sa Short circuit / arc discriminating signal St Welding start signal Td Delay time TI Intermittent feed time setting circuit Ti Intermittent feed time (setting signal) VD Voltage detection circuit Vd Voltage detection signal Vnl No load Voltage VS Voltage setting circuit Vs Voltage setting signal Vw Welding voltage (value) WD Feed speed detection circuit Wd Feed Degree detection signal Wdi Feed distance signal WDI Feed speed integration circuit Wf Feed speed Wi Initial feed speed set value WM Wire feed motor Wr Reverse feed speed set value WS Steady feed speed setting circuit Ws Steady feed Speed setting signal

Claims (4)

[Claims] When a welding start signal is input to a welding power supply, a welding wire is fed forward to a workpiece for a predetermined intermittent feeding time while the output of the welding power supply is stopped. Starting the output of the welding power supply device later to determine whether the welding wire and the workpiece are in contact,
When not in contact, the output of the welding power supply is stopped, and the output of the welding power supply is started again after forward feeding only for the intermittent feeding time, so that the welding wire and the workpiece are separated. The intermittent feeding contact determination operation for determining whether or not the contact is repeated until the welding wire comes into contact with the workpiece, and the welding wire comes into contact with the workpiece by the intermittent feeding contact determination operation. When it is determined that the initial current of a predetermined small current value is supplied from the welding power supply device, the welding wire is fed back from the workpiece, and the welding wire is welded by the backward feeding. An initial arc in which the initial current flows when the object is separated from the object is generated, and after the initial arc is generated, the welding wire is fed forward to the workpiece again at a predetermined steady feeding speed. The initial arc consumable electrode gas shielded arc welding arc start control method for a smooth transition from the generation state to the arc generation state of constant by passing a welding current constant corresponding to the feed rate of the constant to. 2. When a welding start signal is input to the welding power supply, the welding wire is forward-fed to the workpiece by a predetermined intermittent feeding distance while the output of the welding power supply is stopped. The output of the welding power supply is started to determine whether the welding wire is in contact with the workpiece, and if not, the output of the welding power supply is stopped and the intermittent feeding distance is again returned. After the forward feeding, the output of the welding power supply device is started to perform an intermittent feed contact determining operation for determining whether the welding wire is in contact with the workpiece. When it is determined that the welding wire and the workpiece are in contact with each other by the intermittent feeding contact determination operation, a predetermined initial current of a small current value is supplied from the welding power supply device while the current is supplied. Dissolution The contact wire is fed back from the workpiece, and when the welding wire is separated from the workpiece by the backward feed, an initial arc through which the initial current flows is generated, and the welding is performed after the initial arc is generated. The wire is forwardly fed again to the workpiece at a predetermined steady feed rate and a steady welding current corresponding to the steady feed rate is supplied, whereby a steady arc is generated from the initial arc occurrence state. An arc start control method for consumable electrode gas shielded arc welding that smoothly transitions to a state. 3. The arc start control method according to claim 1, wherein the intermittent feeding time is set from outside the welding power supply device. 4. The arc start control method according to claim 2, wherein the intermittent feeding distance is set from outside the welding power supply.