JP3441237B2 - Method and apparatus for determining wear of ignition tip of shield gas welding machine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for automatically detecting and determining wear of an ignition tip of a DC welding machine.

[0002]

2. Description of the Related Art As shown in FIG. 4, a shield gas arc welding machine includes a welding power source 6 and a shield gas supply device 7.
A core wire supply system including a core wire 5, a core wire feeding device 4, and a conduit cable 3, a torch 2, and an ignition tip 1 provided at the tip of the torch 2. The igniting tip 1 is a component that applies a welding voltage to the core wire 5, supplies the core wire through the tip, and has a role of holding a power supply point from the tip 1 to the core wire 5 at a fixed position. Ignition chip 1
As shown in FIG. 5, has a hole 9 having a diameter slightly larger than the outer diameter of the core wire. Done.

The instability factor of the welding method by this device is
It is considered that it is predominant that the feeding force 8 in the ignition tip fluctuates due to the reduction of the tip core wire holding force due to the wear of the tip. Therefore, in order to maintain the welding quality, it is necessary to maintain the feeding point. Must be kept stable and worn tips must be replaced at the right time.

However, the DC shielded gas arc welding phenomenon is caused by repeated arcing and short circuit between the tip of the core wire and the object to be welded, current disturbance due to chip wear, instability of the core wire feeding system and the core wire itself. It is not easy to directly determine the tip life from the welding phenomenon due to external disturbances such as shape and bending. Conventionally, due to the occurrence of welding defects, wear is recognized and the tip is replaced, or the welding length is determined and then unconditionally replaced, or the deflection of the welding ammeter, the appearance of spatter, welding The operator had to empirically judge the sound and replace it.

In addition, as a technique for observing current fluctuations during welding, a welding monitor device (Japanese Patent Laid-Open No. 61-63365) and a welding condition automatic measurement recording method (Japanese Patent Laid-Open No. 61-497).
No. 81), but these merely record effective values of welding current and voltage, maximum and minimum values, etc., and are not techniques for directly monitoring the tip wear state.

[0006]

DISCLOSURE OF THE INVENTION The problem to be solved by the present invention is to provide a method and apparatus for accurately determining tip wear in order to prevent an unstable margin of welding due to tip wear and thus improve welding quality. Is provided.

[0007]

DISCLOSURE OF THE INVENTION The present invention focuses on the correlation between the variation of welding current caused by tip wear and the load current of a core wire supply device, and makes a determination based on the measured values of both to obtain tip wear. It enables accurate determination of. That is, the core wire is fed from the core wire feeder to the ignition tip, and the core wire and the object to be welded are ignited by a shield gas arc welder for welding while applying a DC voltage and spraying a shield gas. In the wear detection determination method, the welding current of the welding machine and the load current of the core wire feeding motor are detected, and the fluctuations of both currents are compared with preset determination threshold values, and based on the results. The wear of the ignition tip of the welding machine is determined, which is a method for detecting the wear of the ignition tip, and a current detection unit which detects the welding current of the welding machine and the current value of the feed motor of the core wire, respectively, A storage unit that stores current values,
An ignition tip wear determination device for a shield gas arc welder, comprising: a determination unit that compares the accumulated current value with predetermined threshold values and determines the wear of the tip based on the result.

[0008]

As shown in FIG. 4, the shield gas arc welding machine is provided with a welding power source 6, a shield gas supply device 7, a core wire supply device 4 having a core wire supply motor 10, and a core wire supply system and a tip. And a torch 2 equipped with an ignition tip 1. The core wire is supplied by the core wire supply device 4 through the ignition tip at the tip of the torch,
A DC voltage is applied from the welding power source between the object to be welded and the core wire, and a shield gas is supplied from the shield gas supply device 7 to perform arc welding.

In the present invention, in the above-mentioned DC shielded arc welding, a method for eliminating various disturbance factors from the welding current which can be directly detected and extracting information on tip wear was examined. That is, other welding conditions and measurement conditions were kept constant, and a change in welding current was investigated using a new chip and a worn chip in a worn state. Figure 3
(A) shows a change in welding current when a new tip is used and (b) a used tip in a worn state is used. As shown in FIG. 3, the welding current fluctuates with a certain swing width, and it is clear that the width is obviously narrower in the new tip and wider in the worn tip. In addition, in the fluctuation waveform of the welding current, in addition to such a low-frequency fluctuation wave, a long-cycle wave is seen as shown in FIG. 3B.
It was found from this cycle that this was a wave caused by the core wire supply system and occurred regardless of chip wear.

Therefore, when the fluctuation due to the core wire supply system in the welding current waveform was separated and further analyzed, it was found that the fluctuation due to the core wire supply system independently affects the load fluctuation of the core wire supply motor. From this, it was found that if the fluctuation of the supplied motor current was measured on one side and combined with the above-mentioned measurement of the fluctuation of the welding current, only the fluctuation due to the tip wear could be extracted. Based on these two pieces of information, a method for judging chip wear was developed under the criteria shown in Table 1. That is, the present invention accumulates the measured values of the welding current within a certain period of time and obtains the maximum fluctuation range (peak to peak) therein, while also obtaining the same fluctuation range for the motor load current in the core wire supply system. Both are compared to determine whether they exceed a preset threshold value, and the chip wear is determined with high accuracy based on the comparison result.

The measured welding current has a relationship as shown in FIG. 2, and it is possible to set a threshold value for discriminating between a new chip and a worn chip. When using a welding method that artificially changes the welding current such as weaving, the difference between the new tip and the worn tip is maintained only by raising the threshold value, and therefore, by changing the threshold value, Applicable.

[0012]

EXAMPLES The present invention will be described in detail below with reference to examples. FIG. 1 is a block diagram showing the configuration of a determination device according to the present invention, in which a welding current detecting unit 11 for detecting a welding current, a welding current accumulating unit 12 for accumulating the detected welding current, and a core wire for detecting a core feeding motor current. The feed motor current detection unit 13, the core wire feed motor current storage unit 14 that stores the detected feed motor current, and the accumulated welding current and the accumulated core feed motor current are set for each. It comprises comparators 15a and 15b for comparing with a threshold value, and a judging section 15 having a chip life judging unit 15c for judging the wear of the chip based on the outputs from these comparators 15a and 15b.

Welding current detector 11 for detecting welding current
Shunts the welding current by the shunt 11a, cuts the direct current component in the current through the condenser 11b, and then guides it to the alternating current amplifier 11c for amplification. Next, the amplified current is applied to the A / D (analog / digital conversion) converter 11d in order to facilitate the processing. Here, in order to remove unnecessary high frequency noise from the current fluctuation waveform, a low pass filter may be attached in front of the A / D converter 11d.
In this embodiment, this role is fulfilled by adjusting the conversion speed and conversion method of the A / D converter 11d.

The A / D converted welding current data is then sent to the storage unit 12, where only the maximum and minimum values of the data for a certain period are stored in a P-P value holding memory with a built-in circuit. The operation of discarding the other intermediate values while leaving them in 12a is repeated. It should be noted that this cycle is controlled by the hold signal, and the hold signal can be set to be output at an arbitrary cycle by the timer built in the storage unit 12. When the hold signal arrives, the difference between the maximum value and the minimum value during that period (peak to peak: hereinafter referred to as PP value) is output to the comparator 15a of the determination unit 15.

The measurement of the fluctuation of the core wire feeding motor current is also similar to that of the welding current detecting device. That is, the core motor current detection unit 13 that detects the core supply current divides the welding current by the shunt 13a, and in order to facilitate signal processing, the A / D (analog / digital conversion) converter is used. Call 13b.

The A / D-converted data of the core wire feeding motor is then sent to the accumulating section 14, where only the maximum value and the minimum value of the data for a fixed period are stored in a P built-in circuit by a hold signal. The operation of discarding the other intermediate values while leaving them in the P value holding memory 14a is repeated. When the hold signal comes, the comparator 15b of the determination unit 15 determines the difference between the maximum value and the minimum value during that period (peak to peak: P-P value below).
Output to.

The judging unit 15 is composed of comparators 15a and 15b and a judging unit 15c, and performs comparison and wear judgment based on a threshold value. In the comparators 15a and 15b, the P-P value of the welding current sent from the storage unit 12 and
The P-P value of the core wire feeding motor current is compared with the threshold values set for the welding current and the core wire feeding motor current, and it is compared and judged whether or not they are exceeded.
The result is output to the determiner 15c. The determiner 15
In c, the judgment result is finally output based on the judgment logic table as shown in Table 1. In Table 1, OK indicates that the threshold is not exceeded, and NG indicates that the threshold is exceeded.

That is, if the welding current fluctuates greatly and the core wire feeding motor current neither increases nor fluctuates, it is determined that the tip is worn. Even if the fluctuation of the welding current exceeds the threshold and the fluctuation of the feed motor current exceeds the threshold, or the fluctuation of the welding current does not exceed the threshold, If the fluctuation of the supply current exceeds the threshold value, it is determined that the core wire feeding system has failed.

The P-P value of the measured welding current is
Since the original signal also contains a large variation, a large peak-to-peak value may sometimes be output. Therefore, in order to prevent an erroneous determination, the threshold comparison described above is performed a plurality of times (in the present embodiment, It is also preferable to perform the determination logic so as to determine that the variation is large, that is, chip wear when the threshold value is continuously exceeded twice. Furthermore, it is also preferable to provide a logic circuit so that the current during this time is not sampled as data at the welding start and end portions where the welding phenomenon is unstable and inevitably has large fluctuations.

In addition to the above two PP values, information on the maximum load current of the core wire feeding motor is further added,
Compare whether this load current value exceeds the threshold value,
It is also preferable to make a determination by adding this comparison result to the above two comparison results.

[0021]

[Table 1]

[0022]

EFFECTS OF THE INVENTION By using the above method and apparatus for detecting and detecting the degree of wear of the tip of the present invention, accurate tip replacement can be performed, defective welding can be prevented, and the welding work time can be restricted by the tip replacement before the use limit. Waste of chips can be eliminated.

[Brief description of drawings]

FIG. 1 is a block diagram of a device configuration of the present invention.

FIG. 2 is a diagram showing a characteristic of a PP value with respect to a welding current value.

FIG. 3 is a current waveform diagram showing a change in welding current depending on old and new tips.

FIG. 4 is a schematic diagram showing a configuration of a welding machine.

FIG. 5 is a diagram showing a feeding point of an ignition chip.

[Explanation of symbols]

1 ignition chip 2 torch 3 Conjet cable 4 feeder 5 core wire 6 welding power source 7 Shield gas tank 8 feeding points 9 power supply holes 10 supply motor

Front page continued (72) Inventor Kazuhiro Tanaka 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Co., Ltd. Inside the Kimitsu Works (72) Inventor Shin Ogawa 1036-1, Kimitsu, Chiba Taihei Industrial Co., Ltd. Within Kimitsu Branch (56) Reference JP-A-7-124744 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B23K 9/10 B23K 9/26

Claims (2)

(57) [Claims] 1. A method for determining wear of an ignition tip of a shield gas arc welding machine, comprising: feeding a core wire; applying a DC voltage between the core wire and an object to be welded; and welding while spraying a shield gas. The welding current of the welding machine and the load current of the core wire feeding motor are detected, the fluctuations of both currents are compared with the preset judgment threshold values, and the ignition tip of the welding machine is based on the comparison result. A method for determining the wear of an ignition tip, which is characterized by determining the wear of the ignition tip. 2. A current detecting section for respectively detecting a welding current of a welding machine and a current value of a feeding motor for a core wire, a storage section for storing the current value, and a predetermined value for the stored current value. An ignition chip wear determination device for a shield gas welder, comprising: a determination unit that compares a threshold value and determines the wear of the tip based on the comparison result.