JP6516290B2 - Copy control method of forward and reverse feed arc welding - Google Patents

Description

  The present invention uses forward and reverse arc welding in which welding speeds are alternately switched between forward and reverse feed periods, and forward and reverse arc welding is used to make the welding torch follow the weld line. The present invention relates to a copy control method.

  In general consumable electrode arc welding, welding is performed by feeding a consumable welding wire at a constant speed and generating an arc between the welding wire and a base material. In consumable electrode type arc welding, a welding state often occurs in which a welding wire and a base material alternately repeat a short circuit period and an arc period.

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

  In the invention of Patent Document 1, the average value of the feeding speed according to the welding current setting value is used, and the frequency and the amplitude of the forward feeding and the reverse feeding of the welding wire are values according to the welding current setting value.

  Also, conventionally, copying control has been performed in which a welding torch is welded while following a welding line. In this copying control, during welding, a value that correlates with the positional displacement between the welding torch position and the welding wire is calculated, and the calculated positional displacement amount correlation value is feedback-controlled to copy the welding torch position onto the welding wire. Make it happen. As a method of copying, an arc sensor which weaves a welding torch to change a distance between a feeding tip and a base material and calculates the above positional deviation amount correlation value based on a change in welding current or welding voltage accompanying this change It is used (refer patent document 2). As another method, a positional deviation amount correlation value may be calculated using a CCD camera (see Patent Document 3).

Patent No. 5201266 Patent No. 4515018 gazette Patent No. 3733485 gazette

  Conventionally, according to various welding conditions such as welding current setting value (average feed speed), groove shape, welding wire type, shield gas type, distance between feed tip and base metal, external characteristics of welding power source, etc. The gain of the feedback control system of copying control was adjusted to stabilize the copying control. This is because, if the welding conditions change, the accuracy of the copying control changes significantly, and in order to maintain high accuracy, it is necessary to readjust the gain of the copying control according to the welding conditions. Also, in forward / reverse feed arc welding, the feed speed is constantly changing between the forward feed period and the reverse feed period at a frequency of about 100 Hz, so the gain of the scanning control changes and the movement of the welding torch changes. Then, there is a problem that the stability of the welding state changes.

  Therefore, it is an object of the present invention to provide a copy control method of forward / reverse feed arc welding that can maintain the stability of the welding state even if the gain of the copy control changes.

In order to solve the problems described above, the invention of claim 1 is
In forward and reverse feed arc welding, where the welding torch is made to follow the welding line using forward and reverse arc welding in which welding speed is switched alternately between forward feed period and reverse feed period. ,
The frequency and / or the amplitude of the feeding speed are set by a predetermined waveform setting function having the gain of the scanning control as an input,
The waveform setting function is a function that lowers the frequency and decreases the amplitude as the gain of the scanning control increases.
It is a copy control method of forward and reverse feed arc welding characterized by

  According to the present invention, even if the gain of the scanning control changes, the waveform parameter of the feed speed is automatically optimized according to the change of the gain, so the welding state can always be stabilized.

It is a block diagram of the welding device for enforcing the copy control method of forward / reverse feed arc welding concerning Embodiment 1 of this invention. It is a timing chart of each signal in the welding apparatus of FIG. 1 which shows the copy control method of forward / reverse feed arc welding concerning Embodiment 1 of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First Embodiment
FIG. 1 is a block diagram of a welding apparatus for implementing a copy control method of forward / reverse feed arc welding according to a first embodiment of the present invention. Each block will be described below with reference to the figure.

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

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

  The feed motor WM feeds the welding wire 1 at the feed speed Fw, periodically repeating forward feed and reverse feed, with a feed control signal Fc described later as an input. A fast transient response motor is used as the feed motor WM. The feed motor WM may be installed near the tip of the welding torch 4 in order to accelerate the rate of change of the feed speed Fw of the welding wire 1 and the reversal of the feed direction. Also, in some cases, a push-pull type feed system may be realized by using two feed motors WM.

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

  The positional deviation amount correlation value calculation circuit DL calculates a value correlated with the positional deviation amount between the welding line and the position of the welding torch 4 and outputs a positional deviation amount correlation value signal ΔL. The method of calculating the positional displacement amount correlation value is performed using an arc sensor, a CCD camera or the like which is the prior art (see Patent Documents 2, 3 and the like). When the positional displacement amount correlation value signal ΔL is a positive value, it indicates that the position of the welding torch 4 is displaced to the right from the welding line, and when it is 0, it indicates that the positional displacement is not performed, and it is negative In the case of the value of, it indicates that the position is shifted to the left.

  The gain setting circuit GR outputs a gain setting signal Gr that is optimized according to the welding conditions. The gain setting signal Gr is a positive value.

  The shift amount calculation circuit DD receives the position shift amount correlation value signal ΔL and the gain setting signal Gr, calculates and outputs a shift amount signal ΔD = ΔL · (−1) · Gr. As a result, when the welding torch 4 of positional displacement amount correlation value signal ΔL <0 is displaced to the left from the welding line, the shift amount signal ΔD> 0, and only the absolute value of ΔD in the welding torch 4 rightward direction It will be shifted. The same is true for the opposite case. The amount by which the welding torch 4 is shifted changes according to the gain setting signal Gr. Therefore, the gain of the feedback control system of the scanning control is varied by the gain setting signal Gr.

  The welding torch moving device MS takes the above shift amount signal ΔD as an input and shifts the position of the welding torch 4 in a direction (right and left direction) perpendicular to the welding line based on this signal so as to be along the welding line. When the welding torch 4 is weaving, the weaving center position corresponds to the position of the welding torch described above. The welding torch moving device MS is, for example, a robot.

  The average feed speed setting circuit FAR outputs a predetermined average feed speed setting signal Far.

  The frequency setting circuit SFR calculates and outputs a frequency setting signal Sfr according to a predetermined frequency setting function to which the above gain setting signal Gr is input. The frequency setting function is a function that is defined in advance by experiment and is in inverse proportion to the value of the frequency setting signal Sfr decreasing as the value of the gain setting signal Gr increases.

  The amplitude setting circuit WFR calculates and outputs an amplitude setting signal Wfr according to a predetermined amplitude setting function which receives the above-mentioned gain setting signal Gr. The amplitude setting function is a function that is defined in advance by experiment and is in inverse proportion to the value of the amplitude setting signal Wfr decreasing as the value of the gain setting signal Gr increases. The above frequency setting function and amplitude setting function will be called waveform setting functions.

  The feed speed setting circuit FR receives the above average feed speed setting signal Far, the above frequency setting signal Sfr and the above amplitude setting signal Wfr, and receives the amplitude Wf determined by the amplitude setting signal Wfr and the reciprocal of the frequency setting signal Sfr. Output a feed speed setting signal Fr that is a waveform obtained by shifting a predetermined trapezoidal wave that changes in a positive / negative symmetric shape with a cycle Tf determined by the cycle setting value to the positive feed side by the value of the average feed speed setting signal Do. The feed speed setting signal Fr will be described in detail with reference to FIG. The waveform of the feed speed setting signal Fr may be a sine wave or a triangular wave other than the trapezoidal wave.

  Feed control circuit FC receives feed speed setting signal Fr described above, and feeds control signal Fc for feeding welding wire 1 at a feed speed Fw corresponding to the value of feed speed setting signal Fr. It outputs to the above-mentioned 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 as inputs, and amplifies the error between the output voltage setting signal Er (+) and the output voltage detection signal Ed (-). , And outputs a voltage error amplified signal Ev. The welding apparatus is controlled at a constant voltage by this circuit.

  Drive circuit DV receives the above-described voltage error amplification signal Ev as input, performs PWM modulation control based on voltage error amplification signal Ev, and outputs a drive signal Dv for driving the inverter circuit in the above-described power supply main circuit PM. Do.

  FIG. 2 is a timing chart of each signal in the welding apparatus of FIG. 1 showing a copy control method of forward / reverse feed arc welding according to the first embodiment of the present invention. The figure (A) shows the time change of feed speed Fw, the figure (B) shows the time change of welding current Iw, and the figure (C) shows the time change of welding voltage Vw. The operation of each signal will be described below with reference to FIG.

  The feed speed Fw shown in FIG. 6A 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 an average of predetermined trapezoidal waves that change in a positive-negative symmetric shape with a cycle Tf = 1 / Sf that is the reciprocal of the frequency Sf determined by the amplitude Wf and the frequency setting signal Sfr. The waveform is shifted to the positive feed side by the value of the feed speed setting signal Far. For this purpose, as shown in FIG. 6A, the feed speed Fw has an amplitude Wf which is vertically symmetrical 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-like feed speed pattern predetermined with a cycle Tf. That is, the amplitude above and below the reference line is the same value, and the period above and below the reference line is the same value.

  Here, looking at the trapezoidal wave of the feed speed Fw with 0 as a reference line, as shown in FIG. 6A, the reverse transfer period from time t1 to t5 is a predetermined reverse transfer acceleration period, reverse transfer peak, respectively. A period, a reverse feed peak value and a reverse feed deceleration period are formed, and a forward feed period of time t5 to t9 is formed of a predetermined forward feed acceleration period, a forward feed peak period, a forward feed peak value and a forward feed deceleration period, respectively. Ru.

[Operation of reverse sending period from time t1 to t5]
As shown in FIG. 6A, the feed speed Fw enters the reverse feed acceleration period from time t1 to t2, and accelerates from 0 to the above-mentioned reverse feed peak value. During this period, the short circuit condition continues.

  When the reverse feed acceleration period ends at time t2, the feed speed Fw enters the reverse feed peak period from time t2 to t4, and becomes the above-mentioned reverse feed peak value, as shown in FIG. At time t3 during this period, an arc is generated by the pinch force by the reverse feed and the welding current Iw. In response to this, the welding voltage Vw sharply increases to an arc voltage value of several tens of volts as shown in FIG. 7C, and as shown in FIG. It will decrease gradually.

  When the reverse transfer peak period ends at time t4, as shown in FIG. 7A, the reverse transfer deceleration period starts from time t4 to t5, and the reverse transfer peak value is decelerated to 0 as described above. During this period, the arcing period continues.

[Operation of forward sending period of time t5 to t9]
As shown in FIG. 6A, the feed speed Fw enters the positive feed acceleration period from time t5 to t6, and accelerates from 0 to the above-mentioned positive feed peak value. During this period, the arc period remains.

  When the positive feed acceleration period ends at time t6, as shown in FIG. 6A, the feed speed Fw enters the positive feed peak period from time t6 to t8 and becomes the above-mentioned positive feed peak value. At time t7 during this period, a short circuit occurs due to forward feeding. In response to this, as shown in FIG. 6C, the welding voltage Vw sharply decreases to a short circuit voltage value of several volts, and as shown in FIG. 6B, the welding current Iw falls during the subsequent short circuit period. Will increase gradually.

  When the forward feed peak period ends at time t8, as shown in FIG. 7A, the forward feed deceleration period from time t8 to t9 is entered, and the above-mentioned forward feed peak value is decelerated to zero. During this period, the short circuit period continues.

  After this, the operations of the above-mentioned reverse sending period and the above-mentioned forward sending period are repeated.

The numerical example of the trapezoidal wave of the feed speed Fw is shown below.
Frequency Sf = 100 Hz (period Tf = 10 ms), amplitude Wf = 60 m / min, average feed speed Fa = 5 m / min, half period of each slope period = 1.2 ms, peak period = 2.6 ms, peak value = 30 m When the trapezoidal wave is set to / min, the trapezoidal wave is shifted to the positive 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 transfer period = 4.6 ms, reverse transfer acceleration period = 1.0 ms, reverse transfer peak period = 2.6 ms, reverse transfer peak value = −25 m / min, reverse transfer deceleration period = 1.0 ms
Positive feed period = 5.4 ms, Positive feed acceleration period = 1.4 ms, Positive feed peak period = 2.6 ms, Positive feed peak value = 35 m / min, Positive feed deceleration period = 1.4 ms

  As shown in FIG. 2A, the waveform parameters of the feed speed Fw are the frequency Sf, the amplitude Wf, and the like. When the gain setting signal Gr adjusted to an appropriate value according to the welding conditions changes, the frequency setting signal Sfr is calculated by the frequency setting circuit SFR of FIG. 1, and the amplitude setting signal Wfr is calculated by the amplitude setting circuit WFR of FIG. Ru. Then, based on these signals, the frequency Sf and the amplitude wf of the feed speed Fw are automatically set. For this reason, even if the value of the gain setting signal Gr changes, the frequency Sf and the amplitude Wf of the feed speed Fw are automatically optimized so that the welding state is stabilized.

  During welding, a value (position shift amount correlation value signal ΔL) correlating with the position shift amount between the welding torch 4 and the weld line is calculated every time by the position shift amount correlation value calculation circuit DL of FIG. Then, the shift amount calculation circuit DD of FIG. 1 calculates the shift amount signal ΔD for shifting the welding torch 4 based on the positional shift amount correlation value signal ΔL and the gain setting signal Gr. The welding torch 4 is shifted laterally along the welding line by this signal. As a result, the welding state can be kept stable while maintaining the high accuracy of the copying control.

  In the first embodiment, both the frequency setting signal Sfr and the amplitude setting signal Wfr are changed by the gain setting signal Gr. However, only one of them may be changed.

  According to the first embodiment described above, the waveform parameter (frequency and / or amplitude) of the feeding speed is set by a predetermined waveform setting function having the gain of scanning control as an input. Thereby, in the present embodiment, even if the gain of the scanning control changes, the waveform parameter of the feed speed is automatically optimized according to the change of the gain, so the welding state can always be stabilized. it can.

DESCRIPTION OF SYMBOLS 1 welding wire 2 base material 3 arc 4 welding torch 5 feed roll DD shift amount calculation circuit DL position shift amount correlation value calculation circuit 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 amplifier 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 Feeding speed setting signal Fw Feeding speed GR Gain setting circuit Gr Gain setting signal Iw Welding current MS Welding torch moving device PM Power supply main circuit Sf Frequency SFR Frequency setting circuit Sfr Frequency setting signal Tf Period Vw Welding voltage Wf Amplitude WFR Amplitude setting circuit Wfr Amplitude setting signal WL Reactor WM Feed motor ΔD Shift amount signal Δ Positional deviation amount correlation value signal

Claims (1)

In forward and reverse feed arc welding, where the welding torch is made to follow the welding line using forward and reverse arc welding in which welding speed is switched alternately between forward feed period and reverse feed period. ,
The frequency and / or the amplitude of the feeding speed are set by a predetermined waveform setting function having the gain of the scanning control as an input,
The waveform setting function is a function that lowers the frequency and decreases the amplitude as the gain of the scanning control increases.
Control method of forward and reverse feed arc welding characterized in that.

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