JPS6326272A - Method and device for controlling arc length in non-consumable electrode type automatic welding - Google Patents

Abstract

PURPOSE:To enable a stabilized arc length control even if the response of a control system is remarkably made higher by monitoring a feeding wire and the body to be welded or the voltage between electrodes in order to control an arc voltage in the set voltage. CONSTITUTION:The voltage Va between a feeding wire 7 and the base metal 5 to be welded is detected by a differential amplifier 20 and fed to a comparator 23 through a filter 21. The comparator 23 sends out an output by comparing with a wire separation discriminating reference signal Vak. A signal generater 24 makes a wire separation detecting signal with the waveform formation of the output of the comparator 23 and feeds to a sample holding circuit 11. The circuit 11 receives the signal A and holds the arc voltage V with its sampling at its rise. Since the arc voltage V to be compared with the set arc voltage by the comparator 13 becomes the voltage reduced sufficiently the stability of the control system can be secured even if the gain of an amplifier circuit 15 be taken higher.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for controlling arc length to a constant value in a welding process using a non-consumable electrode.

[Conventional technology]

In this type of welding method, in order to ensure good welding quality, the arc length has traditionally been controlled to be constant, as described in Japanese Utility Model Publication No. 56-48462, for example. There is.

This arc length control focuses on the fact that when the welding current exceeds a certain value, the arc voltage is proportional to the welding current and the arc length, and as shown in FIG. Arc voltage between 2 and pressure detector 9
The detected arc voltage is passed through a filter 8 to remove noise, and then compared with the set arc voltage set by the voltage setting device 14, and the difference is taken out by the comparator 12.
Amplifying circuits (power amplifier 18 and control amplifier 19)
) and then the torch drive mechanism (torch drive motor 1
6 and mechanical means 17), and the welding torch position is controlled in the torch axial direction so that the above-mentioned difference becomes zero. Note that 4 is an arc, and 6 is a feeding tip for feeding the feeding wire 7.

[Problem that the invention seeks to solve]

Therefore, when high-speed movement is required for the vertical movement of the welding torch, for example, in automatic groove tracing control as described in Japanese Patent Publication No. 52-29973 and Japanese Patent Publication No. 59-15743, welding Since the vertical movement of the torch must follow the shape of the groove wall, it is necessary to improve the responsiveness of the control system to cope with this. In this control system, high responsiveness can be achieved by increasing the gain of the control amplifier 19, but at the same time, it has the problem of becoming vulnerable to noise that enters as disturbance. There are two types of disturbances that cannot be ignored: ripple noise from the welding power source and droplet transfer noise from the feed wire (Figure 4).The former is an integral multiple of the power frequency (commercial frequency 50 or 60 Hz). Since the latter has a frequency of Increasing the value becomes the biggest factor in losing stability of the control system, so the conventional method described above has a problem in that it is difficult to improve the tracing accuracy.

This invention was made to solve the above-mentioned conventional problems, and is a non-consumable electrode type automatic that can perform stable arc length control even if the responsiveness of the control system is significantly increased compared to the conventional one. The purpose of this invention is to obtain a method and device for controlling arc length in welding.

[Means to solve the problem]

In order to achieve the above object, the present invention monitors the voltage between the feed wire and the object to be welded or between the feed wire and the electrode, and supplies the feed wire based on the level of the voltage. The structure is such that it is determined whether there is contact between the wire and the molten pool, and during the non-contact period, the arc voltage at the time of detection of the period or at the time of contact preceding the period is compared with the set arc voltage.

[Embodiments of the invention]

Before explaining the present invention in detail, please refer to Fig. 4 and Fig. 5 for the change in arc voltage during droplet transfer (■) and the change in voltage (■1) between the feed wire and the base metal to be welded, respectively. (In Fig. 4, ■1 indicates when the feed wire 7 fed toward the molten pool P and the base metal 5 to be welded are in contact as shown in (a). The voltage between the welding torch 2 and the base material 5 to be welded, v2, is the voltage between the feeding wire 7 and the base material 5 to be welded (
As shown in b), the voltage between the welding torch 2 and the base material 5 to be welded when they are separated includes a ripple component ΔV. Fifth
In the figure, ■□ indicates that the feeding wire 7 and the base material 5 to be welded are (a
The voltage between the two when they are in contact as shown in ) is the voltage between them when the feed wire 7 and the base metal to be welded 5 are separated as shown in the peak).

Next, one embodiment of the present invention will be described with reference to FIGS. 1 and 2.

In FIG. 1, IO is a wire condition detection device for detecting the presence or absence of contact between the feed wire 7 and the base metal 5 to be welded, and has a configuration as shown in FIG. The wire separation detection signal A sent out by this is supplied to the sample and hold circuit 11 as a sample and hold command. The output of the sample and hold circuit 11 is compared with a set arc voltage Vk by a comparator 13, and the difference signal is supplied to an amplifier circuit 15. Since the other configurations are the same as those in FIG. 4, the same reference numerals are given and the explanation thereof will be omitted.

In FIG. 2, reference numeral 20 denotes a differential amplifier, which receives the voltage of the feed wire 7 and the voltage of the base material 5 to be welded.
The voltage (V) between the base material 5 and the base material 5 to be welded is detected, and the output V is supplied to the comparator 23 through the filter 21. The comparator 23 receives the above output V.

For example, as aVak, which compares the wire separation determination reference signal Vlk and sends an output when ■>vo,
vo and v in Figure 5! intermediate value (about 1.5 volts)
Set. The signal generator 24 shapes the output from the comparator 23 into a waveform to create a wire separation detection signal A, which is supplied to the sample and hold circuit 11 . Sample hold circuit 11
When this wire separation detection signal A arrives, the arc voltage ■ is sampled at the rising edge of the wire separation detection signal A.
The arc voltage V sampled during input is held. For this reason, the voltage that is compared with the set arc voltage (■) by the comparator 13 is
As shown in 1, the period of separation from the molten pool P is the fourth period.
The voltage is not the voltage 2 shown in the figure, but a voltage equal to the voltage V.

As a result, the arc voltage V compared with the set arc voltage V becomes a voltage with sufficiently reduced ripples, as shown by the dotted line in Figure 4, so even if the gain of the amplifier circuit 15 is set high, the control system remains stable. The performance can be ensured, and the responsiveness can be significantly improved compared to the conventional method.

In the above embodiment, the voltage V between the feed wire 7 and the base material to be welded 5 is extracted and supplied to the wire condition detection device 10, but instead of this, the voltage V between the feed wire 7 and the non-consumable electrode 3
A similar effect can be obtained by extracting and supplying the voltage between the two.

〔Effect of the invention〕

As explained above, this invention can also remove noise components from the arc voltage that adversely affect the operation of the control system but are difficult to remove with ordinary filters.
Even if the gain of the control system is significantly increased compared to the conventional method, control stability can be ensured and the welding torch can be operated at high speed, so the groove tracing accuracy can be significantly improved compared to the conventional method. .

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a detailed block diagram of main parts in the above embodiment, Fig. 3 is a block diagram showing a conventional arc length control device, and Fig. 4 is an arc voltage FIG. 5 is a diagram showing the relationship between the waveform and the feeding wire position, and FIG. 5 is a diagram showing the droplet transfer noise component in relation to the feeding wire position. 8-・Low pass filter, 9-・-Arc voltage detector,
10- Wire condition detection device, 11- Sampling circuit, 13- Comparator.

Claims (2)

[Claims] (1) In the arc length control method in non-consumable electrode automatic welding, which detects the arc voltage, compares it with the set arc voltage, and moves the welding torch in the direction of the torch axis according to the difference, The voltage between the feeding wire and the object to be welded or the feeding wire and the electrode is monitored, and based on the level of the voltage, it is determined whether or not there is contact between the feeding wire and the molten pool, and non-contact is detected. A method for controlling arc length in non-consumable electrode type automatic welding, characterized in that, in a period, the arc voltage at the time of detection of the period or at the time of contact preceding the period is compared with the set arc voltage. (2) A voltage detector that detects the arc voltage, a comparator that compares the output of the voltage detector that is input through a low-pass filter with the set arc voltage, and a welding torch that responds to the differential signal output by the comparator. In an arc length control device for non-consumable electrode type automatic welding that has a servo system that drives the molten pool in the axial direction, a sample hold circuit is inserted between the filter and the comparator, and the sample is fed toward the molten pool. A detection device is provided that monitors the voltage between the feed wire and the workpiece and generates a non-contact detection signal when the voltage exceeds a set voltage, and the sampling and hold circuit detects the rising edge of the non-contact detection signal. An arc length control device for non-consumable electrode type automatic welding, characterized in that the arc voltage is sampled and held during a signal output period.