JP2016203221A - Profiling control method of forward and reverse feed arc welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a profiling control method of forward and reverse feed arc-welding, in which a profiling control system is stabilized even when a waveform parameter of a feed speed changes.SOLUTION: A profiling control method of forward and reverse feed arc welding uses the forward and reverse arc welding in which a feed speed Fw of a welding wire is alternately switched into a forward feed period and a reverse feed period to perform welding, and makes a welding torch profile a welding line. A gain of a feedback control system of profiling control is changed when an average value Fa of the feed speed Fw is a fixed value and a waveform parameter (cycle Tf and amplitude Wf)) of a feed speed Fw changes. Thereby, the gain of the profiling control system is automatically optimized in accordance with the change of the waveform parameter, even when the waveform parameter of the feed speed Fw changes, and thus, the profiling control is always stabilized.SELECTED DRAWING: Figure 2

Description

  The present invention uses forward / reverse arc welding in which the welding wire feed speed is alternately switched between a forward feed period and a reverse feed period to perform welding, and forward / reverse feed arc welding in which the welding torch follows the weld line is used. The present invention relates to a copying control method.

  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, a method has been proposed in which welding is performed by periodically repeating forward and backward feeding of the welding wire (see, for example, Patent Document 1).

  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.

  Conventionally, copying control is performed in which a welding torch is welded while following a welding line. In this copying control, a value that correlates with the position deviation amount between the position of the welding torch and the weld line during welding is calculated, and the calculated position deviation amount correlation value is feedback-controlled to copy the position of the welding torch to the weld line. Let me. As a method of copying, there is an arc sensor that weaves the welding torch, changes the distance between the power feed tip and the base material, and calculates the above-described positional deviation amount correlation value based on the change in the welding current or the welding voltage accompanying this change. Used (see Patent Document 2). As another method, a positional deviation amount correlation value may be calculated using a CCD camera (see Patent Document 3).

Japanese Patent No. 52012266 Japanese Patent No. 4515018 Japanese Patent No. 3733485

  Conventionally, the gain of the feedback control system of the scanning control is changed in accordance with the welding current set value (average feed speed) to stabilize the scanning control. However, in forward / reverse feed arc welding, there is a case where the waveform parameter of the feed rate is changed in order to make the weld bead a desired shape while the average feed rate is a constant value. In such a case, there is a problem that the copying control becomes unstable.

  Therefore, an object of the present invention is to provide a scanning control method for forward / reverse feeding arc welding that can always stabilize scanning control even if the waveform parameter of the feeding speed changes.

In order to solve the above-described problems, the invention of claim 1
In a scanning control method for forward / reverse feed arc welding that uses forward / reverse arc welding in which the welding wire feed speed is alternately switched between the forward feed period and the reverse feed period and welds, and the welding torch follows the weld line. ,
When the waveform parameter of the feeding speed changes, the gain of the scanning control is changed.
This is a scanning control method for forward and reverse feed arc welding.

The invention of claim 2 changes the gain of the scanning control when the average value of the feeding speed is a constant value and the waveform parameter of the feeding speed changes.
The scanning control method for forward / reverse feed arc welding according to claim 1.

In the invention of claim 3, the waveform parameter of the feeding speed is a frequency and / or an amplitude.
A method for controlling the scanning of forward / reverse feed arc welding according to claim 1 or 2.

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

It is a block diagram of the welding apparatus for implementing the scanning control method of the forward / reverse feed arc welding which concerns on Embodiment 1 of this invention. It is a timing chart of each signal in the welding apparatus of FIG. 1 which shows the scanning control method of the forward / reverse feed arc welding according to the first embodiment of the present invention.

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

[Embodiment 1]
FIG. 1 is a block diagram of a welding apparatus for performing a scanning control method for forward / reverse feed arc welding 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 described later, and feeds the welding wire 1 at a feed speed Fw by periodically repeating forward feed and reverse feed. 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 average feed speed setting circuit FAR outputs a predetermined average feed speed setting signal Far. The frequency setting circuit SFR outputs a predetermined frequency setting signal Sfr. 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 frequency setting signal Sfr, and the amplitude setting signal Wfr, and receives the amplitude Wf determined by the amplitude setting signal Wfr and the inverse of the frequency setting signal Sfr. A feed speed setting signal Fr having a waveform obtained by shifting a predetermined trapezoidal wave that changes in a positive and negative symmetrical shape with a period Tf determined by the period set value to the forward feed side by the value of the average feed speed setting signal Far is output. To do. The feed speed setting signal Fr will be described in detail with reference to FIG.

  The feed control circuit FC receives the feed speed setting signal Fr and receives a feed control signal Fc for feeding the welding wire 1 at a feed speed Fw corresponding to the value of the feed speed setting signal Fr. It outputs to said feed motor WM.

  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 for calculating the positional deviation amount correlation value is performed using a conventional arc sensor, CCD camera, or the like (see Patent Documents 2 and 3). When the positional deviation amount correlation value signal ΔL is a positive value, it indicates that the position of the welding torch 4 is shifted to the right side from the weld line, and when it is 0, it indicates that the positional deviation is not negative. A value of indicates that the position is shifted to the left.

The gain setting circuit GR receives the above average feed speed setting signal Far, the above frequency setting signal Sfr, and the above amplitude setting signal Wfr and inputs a predetermined gain setting function using the average feed speed setting signal Far. The gain standard value is calculated by the above, the gain standard value is corrected by both values of the frequency setting signal Sfr and the amplitude setting signal Wfr, and is output as the gain setting signal Gr. The gain setting signal Gr is a positive value. The gain setting function is defined in advance by experiments. The gain setting function is a function that decreases the standard gain value as the average feed speed setting signal Far increases. The correction of the gain standard value is performed as follows, for example.
1) A frequency reference value Sf0 and an amplitude reference value Wf0 are set in advance.
2) Gr = (standard gain value) −a · (Sfr−Sf0) −b · (Wfr−Wf0). a and b are predetermined positive constants. As a result, the gain standard value is corrected to be smaller as the value of the frequency setting signal Sfr is larger than the frequency reference value Sf0, and the gain standard value is corrected to be larger as it is smaller than the frequency reference value Sf0. Further, the gain standard value is corrected to be smaller as the value of the amplitude setting signal Wfr is larger than the amplitude reference value Wf0, and the gain standard value is corrected to be larger as it is smaller than the amplitude reference value Wf0.

  The shift amount calculation circuit DD calculates and outputs the shift amount signal ΔD = ΔL · (−1) · Gr, with the positional deviation amount correlation value signal ΔL and the gain setting signal Gr as inputs. As a result, when the welding torch 4 having the positional deviation amount correlation value signal ΔL <0 is shifted to the left from the weld line, the shift amount signal ΔD> 0, and the welding torch 4 is moved to the right by the absolute value of ΔD. Will shift. The same applies to the reverse case. The amount by which the welding torch 4 is shifted varies depending on the gain setting signal Gr. Therefore, the gain of the feedback control system of the copying control is varied by the gain setting signal Gr. As a result, even if the average feeding speed is a constant value, if the frequency and / or amplitude of the waveform parameter of the feeding speed changes, the gain of the copying control is changed and optimized. Thereby, even if the waveform parameter of the feeding speed changes, the copying control can always be stabilized.

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

  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 apparatus is controlled at a constant voltage.

  The drive circuit DV receives the voltage error amplification signal Ev, performs PWM modulation control based on the voltage error amplification signal Ev, and outputs a drive signal Dv for driving the inverter circuit in the power supply main circuit PM. To do.

  FIG. 2 is a timing chart of each signal in the welding apparatus of FIG. 1, showing a scanning control method for forward / reverse feed arc welding according to Embodiment 1 of the present invention. FIG. 4A shows the time change of the feeding speed Fw, FIG. 3B shows the time change of the welding current Iw, and FIG. 4C shows the time change of the welding voltage Vw. Hereinafter, the operation of each signal will be described 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 obtained by averaging a predetermined trapezoidal wave that changes into a positive / negative symmetrical shape with a period Tf = 1 / Sf, which is the reciprocal of the frequency Wf determined by the amplitude setting signal Wfr and the frequency Sf determined by the frequency setting signal Sfr. The waveform is shifted to the forward feed side by the value of the feed speed setting signal Far. For this reason, as shown in FIG. 5A, 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, as shown in FIG. 5A, the reverse feed period at times t1 to t5 is a predetermined reverse feed acceleration period and reverse feed peak, respectively. 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]
As shown in FIG. 5A, 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. During this period, the short-circuit state continues.

  When the reverse acceleration period ends at time t2, as shown in FIG. 5A, 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 suddenly increases to an arc voltage value of several tens of volts as shown in FIG. 5C, and the welding current Iw is set to the arc period thereafter as shown in FIG. The inside gradually decreases.

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

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

  When the forward feed acceleration period ends at time t6, as shown in FIG. 5A, the feed speed Fw enters the forward feed peak period from time t6 to t8, and becomes the above-mentioned forward feed peak value. 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. 5C, and the welding current Iw is maintained during the subsequent short-circuit period as shown in FIG. Gradually increases.

  When the forward feed peak period ends at time t8, as shown in FIG. 5A, the forward feed deceleration period starts at time t8 to t9, and decelerates from the forward feed peak value to zero. During this period, the short circuit period continues.

  Thereafter, the operations in the reverse feed period and the forward feed period are repeated.

A numerical example of the trapezoidal wave of the feeding speed Fw is shown below.
Frequency Sf = 100 Hz (cycle Tf = 10 ms), amplitude Wf = 60 m / min, average feed speed Fa = 5 m / min, each half period of slope = 1.2 ms, peak period = 2.6 ms, peak value = 30 m When a trapezoidal wave of / min is set, this trapezoidal wave is shifted to the forward feed side by an 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

  As shown in FIG. 2A, the waveform parameters of the feeding speed Fw are the frequency Sf, the amplitude Wf, and the like. When these waveform parameters change, the gain setting signal Gr changes by the gain setting circuit GR of FIG. During welding, a value (position shift amount correlation value signal ΔL) that correlates with the position shift amount between the welding torch 4 and the weld line is calculated every moment by the position shift amount correlation value calculation circuit DL of FIG. Then, the shift amount calculation circuit DD in FIG. 1 calculates a shift amount signal ΔD for shifting the welding torch 4 based on the positional deviation amount correlation value signal ΔL and the gain setting signal Gr. By this signal, the welding torch 4 is shifted in the left-right direction along the weld line. Therefore, when the average feed speed setting signal Far is a constant value and the frequency setting signal Sfr and / or the amplitude setting signal Wfr change, the gain setting signal Gr changes, and the gain of the scanning control system is optimized. To do. As a result, the copying control is always stabilized.

  According to the first embodiment described above, the gain of the scanning control is changed when the waveform parameter of the feeding speed is changed. Thereby, in this embodiment, even if the waveform parameter of the feeding speed changes, the gain of the scanning control system is automatically optimized according to the change of the waveform parameter, so that the scanning control is always stabilized. be able to.

DESCRIPTION OF SYMBOLS 1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feeding 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 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 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 Sf0 Frequency reference value SFR Frequency setting circuit Sfr Frequency setting signal Tf Frequency Vw Welding Voltage Wf Amplitude Wf0 Amplitude reference value WFR Amplitude setting circuit Wfr Amplitude setting signal WL Reactor W Feed motor ΔD shift amount signal ΔL positional displacement amount correlation value signal

Claims (3)

In a scanning control method for forward / reverse feed arc welding that uses forward / reverse arc welding in which the welding wire feed speed is alternately switched between the forward feed period and the reverse feed period and welds, and the welding torch follows the weld line. ,
When the waveform parameter of the feeding speed changes, the gain of the scanning control is changed.
A scanning control method for forward and reverse feed arc welding, characterized in that: When the average value of the feeding speed is a constant value and the waveform parameter of the feeding speed is changed, the gain of the scanning control is changed.
The scanning control method for forward / reverse feed arc welding according to claim 1. The waveform parameter of the feed rate is frequency and / or amplitude;
3. A scanning control method for forward / reverse feed arc welding according to claim 1 or 2, wherein:

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