JP6460821B2 - Arc welding control method - Google Patents

Description

  The present invention relates to an arc welding control method for performing welding by generating a short circuit period and an arc period by performing forward / reverse feed control for alternately switching a feeding speed of a welding wire between a forward feed period and a reverse feed period. It is.

  In general consumable electrode arc welding, a welding wire that is a consumable electrode is fed at a constant speed, and an arc is generated between the welding wire and a base material to perform welding. In the consumable electrode type arc welding, the welding wire and the base material are often in a welding state in which a short circuit period and an arc period are alternately repeated.

  In order to further improve the welding quality, there has been proposed a method in which welding is performed by periodically repeating forward feeding and backward feeding of a welding wire (see, for example, Patent Documents 1 and 2).

  In invention of patent document 1, it is set as the average value of the feeding speed according to the welding current setting value, and the frequency and amplitude of the forward feed and the reverse feeding of the welding wire are values according to the welding current setting value.

  In the invention of Patent Document 2, the wire feed speed is set to a predetermined constant speed during steady welding, and from the time when the end of welding is instructed, the wire feed speed is changed from normal feed and reverse feed from the predetermined constant speed. Switch to repeated feeding.

Japanese Patent No. 52012266 WO2013 / 136663 Publication

  As described above, in the prior art, stable welding is performed by performing forward / reverse feed control in which the feed speed is alternately switched between a predetermined forward feed period and a predetermined reverse feed period during the steady welding period. be able to. However, in the prior art, when welding is finished, there is a problem that the welding state becomes unstable during a so-called anti-stick period which is a transition period from the forward / reverse feed control to the stop of feed.

  Accordingly, an object of the present invention is to provide an arc welding control method capable of stabilizing the welding state during the anti-stick period in welding in which the forward feed period and the reverse feed period of the feeding speed are alternately switched. To do.

In order to solve the above-described problems, the invention of claim 1
In the arc welding control method of performing welding by generating a short circuit period and an arc period by performing forward / reverse feed control to alternately switch the feeding of the welding wire between the forward feed period and the reverse feed period,
When a welding end command is input, when the reverse feed period ends, the feeding is stopped and welding is ended.
An arc welding control method characterized by the above.

The invention of claim 2 stops the output of the welding voltage when the feeding stops.
The arc welding control method according to claim 1, wherein:

  According to the present invention, when a welding end command is input, the anti-stick period is entered, but after repeating the same operation as during the steady welding period, the welding is ended during the arc period during the reverse feed period. For this reason, welding can be completed in a stable welding state. As a result, since the distance between the tip of the welding wire and the bead becomes an appropriate distance at the end of welding, it is possible to prevent the welding wire from being welded to the bead. Furthermore, the size of the welding wire tip grain is optimized, and the next arc start property can be improved.

It is a block diagram of the welding power supply for implementing the arc welding control method which concerns on Embodiment 1 of this invention. It is a timing chart of each signal at the time of completion | finish of welding in the welding power supply of FIG. 1 which shows the arc welding control method which concerns on Embodiment 1 of this invention. It is a block diagram of the welding power supply for implementing the arc welding control method which concerns on Embodiment 2 of this invention. It is a timing chart of each signal at the time of completion | finish of welding in the welding power supply of FIG. 3 which shows the arc welding control method which concerns on Embodiment 2 of this invention.

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

[Embodiment 1]
In the invention of the first embodiment, when a welding end command is input to the welding power source, the feeding is stopped and the welding is finished when the reverse feeding period of the feeding speed is finished thereafter.

  FIG. 1 is a block diagram of a welding power source for carrying out an arc welding control method according to Embodiment 1 of the present invention. Hereinafter, each block will be described with reference to FIG.

  The power supply main circuit PM receives a commercial power supply (not shown) such as a three-phase 200V, performs output control by inverter control or the like according to a drive signal Dv described later, and outputs an output voltage E. Although not shown, the power supply main circuit PM is driven by a primary rectifier that rectifies commercial power, a smoothing capacitor that smoothes the rectified direct current, and the drive signal Dv that converts the smoothed direct current to high-frequency alternating current. An inverter circuit, a high-frequency transformer that steps down the high-frequency alternating current to a voltage value suitable for welding, and a secondary rectifier that rectifies the stepped-down high-frequency alternating current into direct current.

  The reactor WL smoothes the output voltage E. The inductance value of the reactor WL is, for example, 200 μH.

  The feed motor WM receives a feed control signal Fc, which will be described later, and feeds the welding wire 1 at a feed speed Fw by periodically repeating forward feed and reverse feed during the steady welding period. A motor with fast transient response is used as the feed motor WM. In order to increase the rate of change of the feeding speed Fw of the welding wire 1 and the reversal of the feeding direction, the feeding motor WM may be installed near the tip of the welding torch 4. In some cases, two feed motors WM are used to form a push-pull feed system.

  The welding wire 1 is fed through the welding torch 4 by the rotation of the feeding roll 5 coupled to the feeding motor WM, and an arc 3 is generated between the welding wire 1 and the base material 2. A welding voltage Vw is applied between the power feed tip (not shown) in the welding torch 4 and the base material 2, and a welding current Iw is conducted.

  The voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd. The short circuit determination circuit SD receives the voltage detection signal Vd as described above, and when this value is less than the short circuit determination value (about 10 V), it determines that it is a short circuit period and becomes a high level, and when it is above, it is an arc period. And a short circuit determination signal Sd that is at a low level is output.

  The welding start circuit ST outputs a welding start signal St that is at a high level when a welding start command is issued and that is at a low level when a welding end command is issued. The welding start circuit ST corresponds to a start switch of the welding torch 4, a PLC that controls the welding process, a robot control device, and the like.

  The average feed speed setting circuit FAR outputs a predetermined average feed speed setting signal Far. The period setting circuit TFR outputs a predetermined period setting signal Tfr. The amplitude setting circuit WFR outputs a predetermined amplitude setting signal Wfr.

  The feed speed setting circuit FR receives the average feed speed setting signal Far, the cycle setting signal Tfr, and the amplitude setting signal Wfr, and is determined by the amplitude Wf and the cycle setting signal Tfr determined by the amplitude setting signal Wfr. A feed speed setting signal Fr having a waveform obtained by shifting a predetermined trapezoidal wave that changes into a positive and negative symmetrical shape at the period Tf to the positive feed side by the value of the average feed speed setting signal Far is output. The feed speed setting signal Fr will be described in detail with reference to FIG.

  The start-up circuit ON receives the welding start signal St, the short circuit determination signal Sd, and the feed speed setting signal Fr. When the welding start signal St changes to a high level (welding start command), the activation circuit ON is at a high level. When the short circuit determination signal Sd is at the low level (arc) at the time when the reverse feed period of the feed speed setting signal Fr ends after the welding start signal St changes to the low level (welding end command). An activation signal On that is reset to a low level is output.

  The feed control circuit FC receives the start signal On and the feed speed setting signal Fr, and when the start signal On changes to a high level (start command), the feed control circuit FC corresponds to the feed speed setting signal Fr. A feed control signal Fc for feeding the welding wire 1 at the feed speed Fw is output, and a feed control signal Fc for stopping the feed when the start signal on changes to a low level (stop command). It outputs to said feed motor WM.

  The output voltage setting circuit ER outputs a predetermined output voltage setting signal Er. The output voltage detection circuit ED detects and smoothes the output voltage E and outputs an output voltage detection signal Ed.

  The voltage error amplification circuit EV receives the output voltage setting signal Er and the output voltage detection signal Ed, and amplifies an error between the output voltage setting signal Er (+) and the output voltage detection signal Ed (−). The voltage error amplification signal Ev is output. By this circuit, the welding power source is controlled at a constant voltage.

  The drive circuit DV receives the voltage error amplification signal Ev and the activation signal On, and performs PWM modulation control based on the voltage error amplification signal Ev when the activation signal On changes to a high level (activation command). The drive signal Dv for driving the inverter circuit in the power supply main circuit PM is output, and when the start signal On changes to the Low level (stop command), the output of the drive signal Dv is stopped.

  FIG. 2 is a timing chart of signals at the end of welding in the welding power source of FIG. 1, showing the arc welding control method according to the first embodiment of the present invention. (A) shows the time change of the welding start signal St, (B) shows the time change of the feeding speed Fw, (C) shows the time change of the welding current Iw, (D) shows the time change of the welding voltage Vw, (E) shows the time change of the short circuit determination signal Sd, and (F) shows the time change of the activation signal On. Hereinafter, the operation of each signal at the end of welding will be described with reference to FIG.

  As shown in FIG. 6A, the period from time t11 when the welding start signal St changes to the low level (welding end command) is the steady welding period, and the period from time t11 to t14 is the anti-stick period. The time t14 when the arc disappears and the welding is finished is a time point when the start signal On changes to the low level (stop command) as shown in FIG.

  The feed speed Fw shown in FIG. 5B is controlled to the value of the feed speed setting signal Fr output from the feed speed setting circuit FR of FIG. The feed speed setting signal Fr is a positive trapezoidal wave that changes in a positive and negative symmetric shape with the amplitude Wf determined by the amplitude setting signal Wfr and the period Tf determined by the period setting signal Tfr by the value of the average feed speed setting signal Far. The waveform is shifted to the sending side. For this reason, as shown in FIG. 5B, the feed speed Fw has an amplitude Wf that is symmetrical in the vertical direction with the average feed speed Fa indicated by a broken line determined by the average feed speed setting signal Far as a reference line. It becomes a trapezoidal wave-shaped feeding speed pattern determined in advance with the period Tf. That is, the amplitude above the reference line and the amplitude below the reference line have the same value, and the period above and below the reference line have the same value.

  Here, when the trapezoidal wave of the feed speed Fw is seen with 0 as the reference line, the reverse feed period at times t1 to t5 is a predetermined reverse feed acceleration period and reverse feed peak as shown in FIG. Period, reverse feed peak value, and reverse feed deceleration period, and the forward feed period from time t5 to t9 is formed from a predetermined forward feed acceleration period, forward feed peak period, forward feed peak value, and forward feed deceleration period, respectively. The

[Operation in the reverse feed period from time t1 to t5]
Since the welding start signal St is at a high level (welding start command) as shown in FIG. 9A, the start signal On is also at a high level (start command) as shown in FIG. ing. For this purpose, the welding power source is activated, the welding wire 1 is fed, and the welding voltage Vw and the welding current Iw are output. As shown in FIG. 5B, the feed speed Fw enters the reverse feed acceleration period from time t1 to t2, and accelerates from 0 to the reverse feed peak value. Since the short circuit state continues during this period, the short circuit determination signal Sd is at the high level (short circuit) as shown in FIG.

  When the reverse acceleration period ends at time t2, as shown in FIG. 5B, the feed speed Fw enters the reverse peak period from time t2 to t4 and becomes the reverse peak value described above. At time t3 during this period, an arc is generated by the pinch force generated by reverse feeding and energization of the welding current Iw. In response to this, the welding voltage Vw rapidly increases to an arc voltage value of several tens of volts as shown in FIG. 4D, and the short-circuit determination signal Sd is set at the low level (arc) as shown in FIG. ). As shown in FIG. 5C, the welding current Iw gradually decreases during the subsequent arc period.

  When the reverse feed peak period ends at time t4, as shown in FIG. 5B, the reverse feed deceleration period from time t4 to t5 starts, and the reverse feed peak value decelerates to zero.

[Operation in the forward feed period from time t5 to t9]
As shown in FIG. 5B, the feed speed Fw enters the forward feed acceleration period from time t5 to t6, and accelerates from 0 to the forward feed peak value. During this period, the arc period remains.

  When the forward feed acceleration period ends at time t6, the feed speed Fw enters the forward feed peak period from time t6 to t8, as shown in FIG. At time t7 during this period, a short circuit occurs due to normal feeding. In response to this, the welding voltage Vw rapidly decreases to a short circuit voltage value of several V as shown in FIG. 4D, and the short circuit determination signal Sd is at a high level (short circuit) as shown in FIG. To change. As shown in FIG. 5C, the welding current Iw gradually increases during the subsequent short-circuit period.

  When the forward feed peak period ends at time t8, as shown in FIG. 5B, the forward feed deceleration period from time t8 to t9 starts, and the forward feed peak value decelerates to zero.

  The above operation is repeated during the reverse transmission period from time t9 to t10. Therefore, an arc is generated during the reverse feed peak period.

  The normal feed period starts at time t10, and at time t11 during the normal feed acceleration period from time t10 to t12, the welding start signal St changes to the low level (welding end command) as shown in FIG. At time t14 when the next reverse feed period ends from the time when the welding start signal St changes to the low level (welding end command) at time t11, as shown in FIG. (Stop command). The period from time t11 to t14 is an anti-stick period. However, the operation during the steady welding period described above is repeated also during the anti-stick period. Therefore, a short circuit occurs during the forward feed peak period during the forward feed period from time t10 to t13, and an arc occurs during the reverse feed peak period during the reverse feed period from time t13 to t14.

  The timing at which the welding start signal St becomes the low level (welding end command) is an arbitrary timing of the feed speed Fw, and it is also optional whether it is during the arc period or during the short circuit period. Regardless of the timing from time t10 to time t14, the start signal On changes to the low level (stop command) regardless of the timing at which the welding start signal St changes to the low level (weld end command). Become.

  At time t14, the start signal On changes to the low level (stop command) as shown in FIG. 5F, and the short circuit determination signal Sd changes to the low level (arc) as shown in FIG. Therefore, as shown in FIG. 5B, the feeding speed Fw is 0, and the feeding is stopped. At the same time, since the output of the welding voltage Vw is also stopped as shown in FIG. 4D, the energization of the welding current Iw is also stopped as shown in FIG. At time t14, the arc disappears and welding is completed.

  During the anti-stick period from time t11 to t14, the same operation as during the steady welding period is repeated, so that the welding state is stable. In addition, when welding is completed at time t14, since the reverse feed is completed in the arc period, the distance between the welding wire tip and the bead becomes an appropriate value, and the welding wire is welded to the bead. Can be prevented. Further, since the size of the welding wire tip grain becomes an appropriate value, the next arc start property is also improved.

  In the above, the feeding speed Fw changes in a trapezoidal wave shape, but the same applies to a case where the feeding speed Fw changes in a sine wave shape, a triangular wave shape, or the like.

A numerical example of the trapezoidal wave of the feeding speed Fw is shown below.
Trapezoidal wave with period Tf = 10 ms, amplitude Wf = 60 m / min, average feed speed Fa = 5 m / min, each half period of tilt period = 1.2 ms, peak period = 2.6 ms, peak value = 30 m / min When set, this trapezoidal waveform is shifted to the forward feed side by the average feed speed Fa = 5 m / min. The average welding current is about 250A. Each waveform parameter in this case is as follows.
Reverse feed period = 4.6 ms, Reverse feed acceleration period = 1.0 ms, Reverse feed peak period = 2.6 ms, Reverse feed peak value = −25 m / min, Reverse feed deceleration period = 1.0 ms
Forward feed period = 5.4 ms, forward feed acceleration period = 1.4 ms, forward feed peak period = 2.6 ms, forward feed peak value = 35 m / min, forward feed deceleration period = 1.4 ms

  According to the above-described first embodiment, after the welding end command is input, when it is the arc period at the end of the reverse feed period, the feeding is stopped and the welding is ended. When the welding end command is input, the anti-stick period starts, but the same operation as in the steady welding period is repeated, so that a stable welding state is obtained. For this reason, at the end of welding, the distance between the tip of the welding wire and the bead becomes an appropriate distance, so that the welding wire can be prevented from being welded to the bead. Furthermore, the size of the welding wire tip grain is optimized, and the next arc start property can be improved.

[Embodiment 2]
In the second embodiment, the arc period is shifted to the arc period during the reverse feed period after the welding end command is input, and the welding is stopped when the arc period continues for a predetermined period. .

  FIG. 3 is a block diagram of a welding power source for carrying out the arc welding control method according to the second embodiment. This figure corresponds to FIG. 1 described above, and the same reference numerals are given to the same blocks, and description thereof will not be repeated. This figure is obtained by replacing the activation circuit ON of FIG. 1 with a second activation circuit ON2. Hereinafter, this block will be described with reference to FIG.

  The second start-up circuit ON2 receives the welding start signal St, the short circuit determination signal Sd, and the feed speed setting signal Fr, and when the welding start signal St changes to a high level (welding start command). From the time when the short circuit determination signal Sd changes to the low level (arc) during the reverse feed period of the feed speed setting signal Fr after the welding start signal St is changed to the low level (welding end command) after being set to the high level. When the predetermined period elapses during the arc period, an activation signal On that is reset to a low level is output.

  4 is a timing chart of signals at the end of welding in the welding power source of FIG. 3, showing an arc welding control method according to Embodiment 2 of the present invention. (A) shows the time change of the welding start signal St, (B) shows the time change of the feeding speed Fw, (C) shows the time change of the welding current Iw, (D) shows the time change of the welding voltage Vw, (E) shows the time change of the short circuit determination signal Sd, and (F) shows the time change of the activation signal On. This figure corresponds to FIG. 2 described above. Since only the timing at which welding is completed is different in FIG. 5 and other operations are the same, the description of the same operations will not be repeated. Hereinafter, different operations will be described with reference to FIG.

  As shown in FIG. 5A, the period from time t11 when the welding start signal St changes to the low level (welding end command) is the steady welding period, and the period from time t11 to t15 is the anti-stick period. The time t15 when the arc disappears and the welding is finished is a time when the start signal On changes to the low level (stop command) as shown in FIG. As will be described later, after the welding start signal St changes to the Low level (welding end command) at time t11, the feed speed Fw enters the reverse feed period from time t13, An arc is generated at t14, and the arc period continues for a predetermined period.

  Since the operation during the steady welding period up to time t11 is the same as in FIG. 2, the description will not be repeated. A normal feed period starts at time t10, and at time t11 during the normal feed acceleration period from time t10 to t12, the welding start signal St changes to a low level (welding accommodation command) as shown in FIG. The period from the time when the welding start signal St changes to the Low level (welding end command) at time t11 to the time t15 when the activation signal On shown in FIG. It becomes. However, the same operation as in the above-described steady welding period is repeated during the anti-stick period.

  A short circuit occurs during the forward feed peak period during the forward feed period at times t10 to t13. As shown in FIG. 5B, the feeding speed Fw enters the reverse feeding period from time t13. An arc occurs at time t14 during the reverse peak period. When the arc is generated, the short circuit determination signal Sd changes to the low level (arc) as shown in FIG. Since the arc period continues from time t14 to time t15 when the predetermined period has elapsed, the start signal On changes to the low level (stop command) at time t15 as shown in FIG. In response to this, as shown in FIG. 5B, the feeding speed Fw is forcibly set to 0, and feeding stops. At the same time, since the output of the welding voltage Vw is also stopped as shown in FIG. 4D, the energization of the welding current Iw is also stopped as shown in FIG. At time t15, the arc disappears and the welding ends.

  During the anti-stick period from time t11 to t15, the same operation as during the steady welding period is repeated, so that the welding state is stable. In addition, at the time when welding is completed at time t15, the arc period is a point in time that continues for a predetermined period. Therefore, the distance between the welding wire tip and the bead becomes an appropriate value, and the welding wire is welded to the bead. Can be prevented. In addition, since the size of the welding wire tip grain becomes an appropriate value, the next arc start property is also improved. Furthermore, the size of the welding wire tip grains can be changed to a desired value by adjusting the predetermined period. For this reason, it is possible to obtain optimum wire grains according to the welding conditions such as the diameter and material of the welding wire, and it is possible to make the arc start performance better than that of the first embodiment.

  In the figure, the time t15 at which the activation signal on changes to the Low level is a time before the end of the reverse transmission period. However, as long as it is during the arc period, it may be during the next normal feeding period.

  According to the above-described second embodiment, after the welding end command is input, the process shifts to the arc period during the reverse feed period, and when the arc period continues for a predetermined period, the feeding is stopped and the welding is ended. As a result, the second embodiment has the same effect as the first embodiment. Furthermore, in the second embodiment, by adjusting the arc period of the predetermined period, the wire tip grains at the end of welding can be optimally determined according to the welding conditions, so that the arc start performance can be further improved. it can.

DESCRIPTION OF SYMBOLS 1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feed roll DV Drive circuit Dv Drive signal E Output voltage ED Output voltage detection circuit Ed Output voltage detection signal ER Output voltage setting circuit Er Output voltage setting signal EV Voltage error amplification circuit Ev Voltage error amplification signal Fa Average feed speed FAR Average feed speed setting circuit Far Average feed speed setting signal FC Feed control circuit Fc Feed control signal FR Feed speed setting circuit Fr Feed speed setting signal Fw Feed speed Iw Welding current ON Start-up circuit On Start-up signal ON2 Second start-up circuit PM Power supply main circuit SD Short-circuit determination circuit Sd Short-circuit determination signal ST Welding start circuit St Welding start signal Tf Period TFR Period setting circuit Tfr Period setting signal VD Voltage detection circuit Vd Voltage detection Signal Vw Welding voltage Wf Amplitude WFR Amplitude setting circuit Wfr Amplitude setting signal WL Reactor WM Feeding mode

Claims (2)

]
In the arc welding control method of performing welding by generating a short circuit period and an arc period by performing forward / reverse feed control to alternately switch the feeding of the welding wire between the forward feed period and the reverse feed period,
When a welding end command is input, when the reverse feed period ends, the feeding is stopped and welding is ended.
An arc welding control method characterized by the above. Stopping the output of the welding voltage when the feeding is stopped;
The arc welding control method according to claim 1.

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