JPH0426941B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to groove line tracing welding in which welding is performed while swinging a welding torch or welding wire. [Prior art] In welding in which the welding wire is oscillated, if the center of oscillation deviates from the center of the groove, incomplete welding will result. It has been proposed to shift the swing center in the direction where the integral values match and automatically position the swing center substantially at the groove center (for example,
53-11502 and JP-A-54-26261).
In conventional groove tracing welding of this type, the integral value of the welding current at the right end and left end of the oscillation is compared, and if the integral value at the right end is larger than that at the left end, the center of oscillation shifts to the right. If it is the other way around, it is assumed that it is shifted to the left, and the center of swing is shifted to the left and right, respectively. Additionally, the applicant has identified one turn and the other turn of the swing from the swing width and the swing position, samples the welding current at the return point, and compares these welding currents to detect center deviation. Based on this, we proposed a swing width center control that adjusts the center position (Japanese Patent Application Laid-open No. 151965/1983). In these conventional welding methods, it is considered very difficult to perform welding while greatly changing the welding current from high to low due to the relationship between welding stability, center deviation detection timing, and adjustment control timing. When changing the welding arc significantly, the operator visually checked the welding arc and manually adjusted the torch position to the welding seam. However, there were problems in that the arc had to be constantly monitored during welding, which caused great fatigue, and that the bead could meander. [Object of the invention] The present invention greatly changes the welding current between high and low,
Moreover, the purpose is to automatically perform all welding by aligning the center of vibration with the center of the groove and oscillating it. [Structure and operation of the invention] When welding is performed while greatly changing the welding current from high to low, when the arc point is at the left or right end of the oscillation, the fluctuation of the arc is small, and when the welding current is changed from the left end to the right end or vice versa. When moving, arc fluctuations are likely to occur. On the other hand, when the current is high, the welding current fluctuates greatly, and when the current is low, the welding current has little fluctuation and is highly stable. By the way, in welding where the welding line is vertical to upward and the welding position is vertical or upward, molten metal drips down, so welding must be performed with as low a current as possible. However, at low welding currents, the solidification rate of the molten metal at both ends of the groove in rocking welding is fast;
The arc force is also weak, resulting in poor penetration. Therefore,
It is necessary to switch to a higher welding current after reaching both ends of the groove, and variable welding current welding is now in practical use. In this welding method, the welding torch is moved from the right end to the left end and vice versa, the welding torch is temporarily stopped at each end, and a low current is used when moving between the ends to prevent weld metal from dripping. , it is preferable to use a high current at least temporarily during the stop at each end.
By welding in which the welding current is switched between high and low in this manner, sufficient penetration can be obtained during welding in severe positions, and dripping of molten metal can be prevented. In this way, the current change that changes the current to high and low, and the timing of the torch movement and stop are such that the current is high when the torch stops at both ends of the oscillation, and the timing is such that the current is switched to low current and then the torch starts moving. good. On the other hand, when swinging is performed and the center of swing is automatically adjusted, if the welding current fluctuates sharply at the left and right ends where the welding current is sampled, errors are likely to occur in detecting the center of swing. Therefore, in the present invention, the welding torch is moved between the left and right ends to swing the arc left and right, and is temporarily stopped at each end, and the welding current is low.
In synchronization with high current changes, welding current sampling for detecting the center position of the oscillation is performed when the oscillation reaches the left end and the right end when the current is still low, and then and high current during stop just before driving to the left end. According to this,
The welding current is low while the oscillation reaches the left and right ends and necessary sampling etc. are performed, the welding current is high during subsequent stops, and becomes low when moving towards the other end. Alternatively, when the timing of the low current period and the high current period is determined in advance, the swinging toward the opposite side is started after the high current period has passed, and sampling is performed when the other end is reached. Such synchronization can be easily implemented by using one timing signal as a parameter for high/low switching control of the welding current and as a parameter for swing control. If center shift adjustment is performed in the high welding current section and the welding current sampling section, the welding current will fluctuate, and there is a high possibility that detection will be erroneous or that the weld bead will become bad. Therefore, in a preferred embodiment of the present invention, a low welding current section in the next half-stroke of one reciprocation is assigned to the center deviation adjustment section, and current sampling is not performed in that section. Further, when the width of the groove changes, it is preferable to automatically adjust the swing width accordingly, and when changing the swing width, it is preferable to automatically adjust the welding speed in conjunction with it. Therefore, in one invention of the present application, after sampling the welding currents (maximum values at the left and right ends) at the left and right ends of the oscillation, welding currents (left and right end delay values) in the low current section after a set delay time are sampled. The maximum value on the left end and the delay value on the left end are compared, and the maximum value on the right end and the delay value on the right end are compared. Based on the results of both comparisons, wide and narrow swing widths are detected, and the swing width and welding speed are determined. Automatically adjust. As a result, not only the swing center but also the swing width is automatically adjusted. When the groove width changes, it is necessary to change the swing width of the torch and the running speed of the trolley (welding speed). The groove width was detected by detecting the excess height after welding using a contact detector, etc., and controlling the swing width and cart speed. Since a detector must be attached, the torch portion becomes larger and more complex. Moreover, there are problems such as poor accuracy because the area directly under the weld is not detected, but according to the above-described invention, such problems can be improved. In another invention of the present application, the welding current is sampled at least in one of the left end and the right end of the oscillation, and in a low current section, and this welding current is compared with a set value to adjust the extension. Changing the extension brings about a change in the welding current, so the left and right end maximum values and left,
It is necessary to remove the sampling point of the rightmost delay value. Therefore, in a preferred embodiment, the timing for performing the extension adjustment at the same time as the center adjustment is determined. In the continuous fixed current welding method, a technology for automatically controlling the extension direction by detecting the welding current is known, but there is no arc sensor type technology for welding that changes the welding current from high to low. Currently, contact type detectors are applied to the base metal surface and automatically controlled as an extension. This method has drawbacks such as the inability to bring the detector close to the torch and the complexity of the torch, resulting in poor tracing accuracy. However, according to the present invention described above, since the welding current is relatively stable in the low current section, accurate automatic arc sensor type extension direction control is performed. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an external appearance of a device implementing the present invention in one embodiment, and FIG. 2a shows an outline of the configuration of the electrical system.
Fig. 2b shows details of a part of the electrical system, and Fig. 3 shows welding current and control timing of each part. Referring to FIG. 1, a truck 73 running on a rail 71 is driven by a truck motor 55 via a reduction gear or the like. That is, the truck motor 55 rotates a pinion (not shown) meshed with the rack 72. An adjustment table 74 is mounted on the trolley 73 so as to be movable in the left-right direction, and the adjustment table 74 is driven left and right by a seam tracing motor 49. The oscillating motor 5 drives the connecting rods 75 and 76 back and forth in the left and right directions. A swing plate 77 is fixed to the connecting rods 75 and 76, and an extension motor 63 fixed to the swing plate 77 via a base 82 drives the torch holder 83 up and down. 2 is a torch, and 1 is an object to be welded. 81 is a torch angle adjustment handle, and 80 is a torch trajectory switching bolt. Using the bolt 80, a parallel movement mode in which the entire torch 2 swings left and right, and a rotation mode in which only the tip of the torch 2 swings left and right are selected and set. See Figure 2a. The current flowing between the welding torch 2 and the workpiece 1, that is, the welding current, is detected by a current detector 22, amplified by an amplifier 24, and smoothly shaped by a waveform correction circuit 23, and then sent to analog switches 25 to 28 and an operational amplifier. 57. Analog switches 25 to 28 are controlled on and off by timing signals A to D, respectively. Welding current H, L switching timing generation circuit 21
is the welding power source 20 and the oscillation & amplitude control circuit 7
A timing pulse is applied to alternately instruct low L and high H with a predetermined width at regular intervals. The power supply circuit 20 changes the welding current to high H and low L in synchronization with the timing pulse, as shown in the top row of FIG.
Switch to On the other hand, the oscillation and amplitude control circuit 7 switches from high H to low L in synchronization with the timing pulse, starts moving from one side to the other, stops moving at the amplitude determined by the output of the adder 8, and then A signal is generated to maintain the stopped state until the timing pulse changes from high H to low L, and is applied to the motor energizing amplifier 6. That is, the oscillation & amplitude control circuit 7
As shown in figure b, an oscillation width increase/decrease setting device is connected to the actual position signal of the feedback potentiometer 4, which generates the torch position signal, and the standard value signal of the standard value setting potentiometer 9, which generates the standard amplitude signal. Comparators 7a ₁ and 7a ₂ compare the target value signal obtained by adding the correction value set in 10 with the operational amplifier 8, and when the actual position signal (positive) becomes larger than the target value signal (positive), the torch When the torch 2 reaches the right end target position), the comparator _7a1 outputs H and sets the flip-flop 7b, and when the actual position signal (negative) becomes smaller than the inverted signal (negative) of the target value signal (the torch 2 When the left end target position value is reached) comparator _7a2 becomes H.
is output to reset the flip-flop 7b. As a result, the Q output of the flip-flop 7b is H until the torch 2 reaches the right end target position from the right end target position, and the output is H until the torch 2 reaches the right end target position from the left end target position. . On the other hand, when the torch 2 reaches the left and right target positions, the flip-flop 7d is reset through the OR gate 7c.
d is set by the timing circuit 21's low current indication pulse. As a result, flip-flop 7d
The Q output is H from entering the low current section until the torch 2 reaches the left and right target positions (torch oscillation drive period). The AND gate _7e1 generates an H signal when the torch 2 is oscillating from the right end to the left end, and the AND gate _7e2 generates an H signal when the torch 2 is oscillating from the left end to the right end. While the AND gate 7e ₁ is outputting H, the photocoupler 7f ₁ applies a positive voltage to the speed indicating resistor 56, which causes the motor M2 to rotate forward and drive the torch 2 from the right end to the left end. and gate 7
While e ₂ is outputting H, the photocoupler 7f ₂ applies a negative voltage to the resistor 56, which causes the motor M2 to rotate in reverse and drive the torch 2 from the left end to the right end. As a result, the high H and low L welding currents (the top row in FIG. 3) and the swing position (the second row in FIG. 3) are in a synchronous relationship. The adder 8 is supplied with a voltage indicating the standard amplitude value from a resistor 9 that sets the standard amplitude, and a voltage indicating the amount of oscillation width adjustment from the oscillation amplification reduction setting device 10 (both polarities of + and -). is given, and the adder 8 supplies the oscillation and amplitude control circuit 7 with a voltage representing the added value of both (standard value+adjusted value=target value). As shown in FIG. 2b, the oscillating amplification/reduction setting device 10 has a logic circuit 10a, an up/down counter 10b, and a D/A converter 10c, and has an up/down count function, and has an up/down count function when the input signal H is once high. When the level is reached, the adjustment amount output is changed to a voltage lowered by one unit amount, and once the input signal G becomes a high level, the adjustment amount output is changed to a voltage raised one unit amount. The output voltage ranges from + to -, and when signal H repeatedly goes high, the output voltage becomes -, and the output of adder 8 is essentially a subtracted output. As shown in FIG. 2b, the right end detector 11 and the left end detector 12 are provided with a resistor 12a for setting an end detection point,
It is composed of an adder 12b and comparators 11c and 12c, and the adder 12b generates a signal obtained by adding the detection point setting value to the output of the adder 8 (standard value + adjustment value = target value). The comparator 11c generates an H right end reaching signal (right end pulse) when the actual position signal (positive) of the potentiometer 4 becomes larger than the output (positive) of the adder 8, and the comparator 12c generates an H right end reaching signal (right end pulse). When the actual position signal (negative) of No. 4 becomes smaller than the inverted signal (negative) of the output of adder 8, a left end arrival signal (left end pulse) of H is generated. These end pulses are applied to OR gate 14, AND gates 15 and 16, and frequency divider circuit 13. Triggered by the output of the OR gate 14, the delay circuit T1 produces a high level output, returns the output to a low level after a set time T1, and this output is applied to the AND gates 15 and 16, so that the output of the AND gate 15 A is T1 when the swing reaches the right end
High level during. Output B of AND gate 16
is at a high level during T1 when the swing reaches the left end. These signals A and B are a right-end maximum value sampling instruction signal and a left-end maximum value sampling instruction signal, respectively. OR gate 17 generates the same signal as OR gate 14, which triggers delay circuit T2 to make the output high for T2. When returning to low level after T2, delay circuit T3 is triggered to make the output high for T3. The output of delay circuit T3 is applied to AND gates 18 and 19. The AND gate 18 is activated at T2 after the swing reaches the right end.
The right end delay value sampling instruction signal C becomes high level after T3 and then returns to low level after T3.
AND gate 19 is activated after the swing reaches the left end.
A left end delay value sampling instruction signal D which becomes high level after T2 and returns to low level after T3 is generated. These signals are shown in the third and fourth rows of FIG. On the other hand, the frequency dividing circuit 13 counts the outputs of the right edge detection circuit 11 and the left edge detection circuit 12, and when the count value reaches 3, triggers the delay circuits T4 and T5, and when the count value reaches 4, the count value is reset to 1. Perform the frequency division operation to set. The output of the delay circuit T4 is
As a result, each time the next half stroke of one round trip is completed, T
The output of the delay circuit T6 becomes the reset instruction signal F which becomes high level during T6 after T5 from E. These signals are shown in the fifth and sixth rows of FIG. The outputs C and D of the AND gates 18 and 19 are applied to an OR gate 59 and then applied to a sample hold circuit 58 as a sample instruction signal. Therefore, the low welding current in the sections of signals C and D is extracted and held in the sample hold circuit 58. Each of the above-mentioned signals A to D is applied to each of the analog switches 25 to 28 as an on instruction signal. As a result, analog switch 25-2
8 outputs are peak hold circuits 29 to 3, respectively.
2, and the highest voltage during the period of application is held in circuits 29-32. The peak hold circuit 29 holds the maximum value of the welding current in the signal A section at the timing of the signal A. In other words, the maximum value of the signal A section is held from when the left end of the swing is reached. The peak hold circuit 30 holds the maximum value of the welding current in the signal B section at the timing of the signal B. In other words, the maximum value of the signal B section is held from the time when the left end of the swing is reached. The peak hold circuit 31 holds the maximum value of the welding current in the signal C section at the timing of the signal C. In other words, the maximum value of the signal C section after a delay of T2 after reaching the right end of the swing is held. Further, the peak hold circuit 32 holds the maximum value of the welding current in the signal D section at the timing of the signal D. In other words, the maximum value of the signal D section after T2 after reaching the left end of the swing is held. As shown in FIG. 3, the signals A to D
All occur in the low current section of the welding current, so
The currents held in the peak hold circuits 29 to 32 are those in the low current section of the welding current. This holding voltage is applied to differential amplifiers 33-35. The hold voltages of the peak hold circuits 29 and 30 are applied to the differential amplifier 33. That is, the maximum value a of the signal A section from reaching the right end of the swing and the maximum value a' of the signal B section from reaching the left end of the swing are input.
Amplifier 33 outputs a voltage representing a-a'. The hold voltages of the peak hold circuits 29 and 31 are applied to the differential amplifier 34. That is, the maximum value a of the signal A section from reaching the right end of the swing and the maximum value b of the signal C section after T2 from reaching the right end of the swing are input. Amplifier 34 outputs a voltage representing a-b. The hold voltages of the peak hold circuits 30 and 32 are applied to the differential amplifier 35. That is, the maximum value a' of the signal B section from reaching the left end of the swing and the maximum value b' of the signal D section T2 after reaching the left end of the swing are input. Amplifier 35 outputs a voltage representing a'-b'. Voltages representing these calculation results are applied to comparators 42-47 by turning on analog switches 36-38 during the next signal E (during T4). Comparators 42 and 43 compare voltage a-a' with a reference voltage set by resistor 39, and generate motor control signals instructing seam copying motor 49 to rotate forward, reverse, or stop. The relationship between the voltage a-a' and the outputs of the comparators 42 and 43 is shown in Table 1 below.

[Table] Range.
Comparators 44 and 45 compare voltage a-b with a reference voltage set by resistor 40, and generate an instruction signal G for increasing the swing width and decreasing the speed of the bogie. Comparator 46
and 47 compare the voltage a'-b' with the reference voltage set by the resistor 41, and generate an instruction signal H for decreasing the swing width and increasing the speed of the bogie. The relationship between the voltages a-b, a'-b and the outputs of the comparators 44 to 47 is shown in Table 2 below.

【table】

〔Effect of the invention〕

As described above, according to the present invention, the bead quality is constant and there are no defects, high-quality welding is possible even when the bevel processing and base metal setting are rough, and welding machine settings are easy. Benefits include being able to use and monitor multiple welding machines by one person.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing the external appearance of a welding machine embodying the present invention in one embodiment, Fig. 2a is a block diagram showing a general configuration of the electrical control system of the welding machine, and Fig. 2b is a part of the electrical control system. 3 is a time chart showing the welding current and the timing of signal sampling and control. FIG. 4 is a waveform chart showing the welding current that brings about a specific control state. 1: Workpiece, 2: Welding torch, 3: Potentiometer, 4: Potentiometer, 5: Torch oscillation motor, 7: Oscillation & amplitude control circuit, 10: Oscillation width amplification amount setting device, 11: Right end Detector, 12: left end detector, T1 to T6: delay circuit,
20: Welding power supply circuit, 21: Timing generator,
22: Current detector, 23: Waveform correction circuit, 25~
28, 36 to 38, 62: Analog switch, 2
9-32: Peak hold circuit (memory means), 3
3 to 35: Differential amplifier, 42 to 47: Comparator, 4
9: seam tracing movement motor, 51: bogie speed amplification amount setter, 55: bogie motor, 58: sample hold circuit (memory means), 63: extension motor, 71: rail, 72: rack, 73:
Dolly, 74: Adjustment stand, 75, 76: Connecting rod, 7
7: Rocking plate, 80: Torch trajectory switching bolt, 8
1: Torch angle adjustment handle, 82: Base, 8
3: Torch holder.

Claims (1)

[Claims] 1. In consumable electrode welding in which groove welding is performed by swinging the welding torch tip in a direction perpendicular to the welding progress direction: moving the welding torch tip from left to right and vice versa Move the tip of the welding torch so that the welding current is low during the oscillation to temporarily stop at the left and right ends, and during the pause, the welding current increases immediately before moving from one end to the other end. Stop and lower the welding current,
Switch to high; the left end maximum value is the maximum value of the low welding current within the set range near the moment the welding torch tip reaches the left end, and the right end maximum value is the maximum value of the low welding current within the set range near the right end moment. Stored in a storage means; Compare the left end maximum value and the right end maximum value, and based on the comparison result, shift the center of the swing of the welding torch to the left end side or the right end side so that both maximum values match. Groove tracing welding control method. 2. In consumable electrode welding, in which the tip of the welding torch is oscillated in a direction perpendicular to the direction of welding progress to weld the groove: The tip of the welding torch is moved from left to right and vice versa, temporarily stopping at the left and right ends. The tip of the welding torch is moved and stopped so that the welding current is low during the movement of the oscillation to be stopped, and the welding current becomes high immediately before the movement from one end to the other during the pause. low,
Switch to high: Left end maximum value, which is the maximum value of low welding current within the set width near the instant the welding torch reaches the left end, right end maximum value, which is the maximum value of low welding current within the set width near the moment the welding torch reaches the right end, and left end maximum value. The left end delay value, which is the welding current value at a low welding current a set time after the instantaneous vicinity, and the right end delay value, which is the welding current value at the low welding current a set time after the right end reaching instantaneous vicinity, are stored in the storage means. Compare the left end maximum value and the right end maximum value, and based on the comparison result, shift the swing center of the welding torch to the left end side or right end side so that both maximum values match; A groove tracing welding control method is characterized in that the right end maximum value and the right end delay value are compared, and the swing width of the welding torch and the welding progress speed are controlled based on the results of both comparisons. 3. In consumable electrode welding where the tip of the welding torch is oscillated in a direction perpendicular to the direction of welding progress to weld the groove: The tip of the welding torch is moved from left to right and vice versa, temporarily stopping at the left and right ends. The tip of the welding torch is moved and stopped so that the welding current is low during the movement of the oscillation to be stopped, and the welding current becomes high immediately before the movement from one end to the other during the pause. low,
Switch to high: Left end maximum value, which is the maximum value of low welding current within the set width near the instant the welding torch reaches the left end, right end maximum value, which is the maximum value of low welding current within the set width near the moment the welding torch reaches the right end, and left end maximum value. The left end delay value, which is the welding current value at a low welding current a set time after the instantaneous vicinity, and the right end delay value, which is the welding current value at the low welding current a set time after the right end reaching instantaneous vicinity, are stored in the storage means. Compare the left end maximum value and the right end maximum value, and based on the comparison result, shift the swing center of the welding torch to the left end side or right end side so that both maximum values match; Also, compare the right end maximum value and the right end delay value, and control the swing width of the welding torch and the welding progress speed based on the results of both comparisons. A welding current value at a low welding current is stored in a storage means, this stored value is compared with a set value, and an extension is controlled based on the comparison result.