JP3898812B2 - Welding stability determination method and stability determination device for arc welding termination processing section - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a consumable electrode type gas shielded arc welding, for the purpose of preventing outflow of poor welding quality caused by the instability of the welding phenomenon of the termination treatment portion, and a welding stability determination method of the arc welding termination treatment portion and The present invention relates to a determination device.
[0002]
[Prior art]
In consumable electrode type gas shielded arc welding, the output control of the welding power source is changed from the thyristor method to the inverter method due to the advancement of the control element, and the control speed is increased by about 50 to 200 times from 300 Hz to 15 to 60 KHz. The current waveform can be controlled, improving the arc start performance, improving the stability of the welding phenomenon during high-speed welding, reducing the amount of spatter generated, and reducing the diameter of the spherical tip of the welding wire to improve arc start performance. This is possible and the stability of the welding phenomenon is being improved.
[0003]
However, the welding quality of the termination processing section is likely to cause various abnormal phenomena due to the inertia of the wire feeding mechanism, and has become a big problem in automatic welding lines by welding robots. In general, whether or not the stability of the welding phenomenon of the termination processing unit is determined is determined by visualizing the uniformity of the appearance of the weld bead of the termination processing unit by an operator or an engineer.
[0004]
However, because of the qualitative determination by visual observation, there are individual differences in the determination in the case of a minute abnormality, and it has been difficult to obtain a uniform standard for in-line determination.
[0005]
[Problems to be solved by the invention]
At present, there is no method to monitor the welding phenomenon stability of the termination processing part in real time and quantitatively, as a countermeasure for stabilizing the welding phenomenon, regularly clean the wire feeding path, replace the wire conduit cable, These measures were taken after contact tips were replaced or when welding quality abnormalities occurred. The present invention has been made in view of the above-mentioned problems of the prior art, and aims to provide a method and apparatus for accurately determining the quality of the welding phenomenon by accurately grasping the welding phenomenon of the termination processing portion. To do.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1
Termination part of consumable electrode type gas shielded arc welding, in which welding is performed while alternately repeating short-circuiting and arcing. In determining arc welding stability, voltage detection means for detecting the welding voltage between the welding wire and the workpiece, welding The analog output signal output using the current detection means for detecting the welding current flowing between the wire and the material to be welded is converted into a digital signal at a predetermined sampling frequency and input to the arithmetic means, and the welding stability of the termination processing section The following three items representing the degree of
(A) Standard deviation σ (∫I _An dt) of the integrated value of the welding current during the arc period for each cycle
(B) Standard deviation σ (∫I _Sn dt) of the integrated value of the welding current during the short-circuit period for each cycle
(C) Standard deviation σ (T _An / T _Sn ) of arc / short-circuit time ratio for each cycle
When any one or more items are calculated and compared with the corresponding reference values, when any one of the differences from the reference value exceeds a preset allowable range, the welding of the termination processing part Is a method for determining the welding stability of an arc welding termination processing section, characterized in that it is determined that is unstable or defective.
[0007]
The invention of claim 2
A consumable electrode type gas shielded arc welding termination treatment unit arc welding stability determination device that performs welding while alternately repeating a short circuit and an arc, and a voltage detection unit that detects a welding voltage between a welding wire and a workpiece, Based on the current detection means for detecting the welding current flowing between the welding wire and the material to be welded, the A / D converter for converting the analog output signal from both means into a digital signal, and the digital signal from the converter,
(A) Standard deviation σ (∫I _An dt) of the integrated value of the welding current during the arc period for each cycle
(B) Standard deviation σ (∫I _Sn dt) of the integrated value of the welding current during the short-circuit period for each cycle
(C) Standard deviation σ (T _An / T _Sn ) of arc / short-circuit time ratio for each cycle
The calculation means for calculating any one or more of the three items and the calculation result from the calculation means are compared with a preset reference value to determine whether the difference from the reference value is within the allowable range. And a display for displaying the output of the comparator. A welding stability determination device for an arc welding termination processing unit.
[0008]
[Action]
The degree of stability of the welding phenomenon that occurs due to the fact that the arc discharge is not stably formed in the termination processing unit, the standard deviation of the integrated welding current value in the arc period for each cycle, and the welding current in the short-circuit period for each cycle. Calculate any one or more of the three items of standard deviation of the integrated value and standard deviation of the arc / short-circuit time ratio for each cycle and display them as quantitative values, and compare them with the corresponding reference values. It is determined that the welding phenomenon is unstable when the difference between any one of the quantitative values and the reference value exceeds a preset allowable range. By doing so, it is possible to accurately and reliably detect welding quality abnormality due to instability of the welding phenomenon due to power feeding failure to the welding wire or increase in feeding resistance.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Next, preferred embodiments of the present invention will be described based on examples of the drawings.
FIG. 1 is a block diagram of an embodiment of the present invention. In the figure, reference numeral 1 denotes a welding power source that applies a predetermined current / voltage between the welding wire 2 and the workpiece 5 and the welding wire 2 is fed at a predetermined speed by the feed roller 3 to weld the workpiece 5. Be paid. 4 is a contact tip, 6 is a shunt for measuring the welding current, 7 is a current detection circuit for detecting a welding current flowing through the welding wire and the workpiece, and 8 is a welding voltage between the welding wire and the workpiece. A voltage detection circuit 9 for converting each analog output signal from both detection circuits 7 and 8 into a digital signal at a predetermined sampling frequency, and 17 an arithmetic and output device for both detection circuits 7 and 8 and A / D converter 9 is included.
[0010]
This device 17 measures the welding voltage and welding current and converts them digitally, and the standard deviation of the arc current welding current integrated value for each cycle and the standard deviation of the short circuit duration welding current integrated value, and the arc / short circuit time for each cycle. CPU 10 for performing various calculations to calculate the standard deviation of the ratio, comparing the calculation result with a preset reference value, and comparing whether the difference from the reference value is within an allowable range, and those calculations CRT 11 (display) and printer 15 for displaying and printing data, memory (ROM 12, RAM 13) for storing various data necessary for programs and calculations, keyboard 14 for inputting constants and other data necessary for measurement, and welding The display 16 displays an abnormal signal such as an abnormal current integral value or an arc / short circuit time ratio error.
[0011]
Next, a method for determining the stability of the welding phenomenon of the termination processing unit according to the present invention will be described. First, FIG. 2 shows a schematic processing flow for executing the arc discharge state analysis of the termination processing unit. First, a sampling speed, a trigger level, and an arc / short-circuit determination voltage are input from the keyboard 14 and set in the CPU 10 to start welding. When the welding voltage reaches the trigger level, the welding voltage / current input is started, and the data is stored in the RAM 13 until the number of measurements reaches the set number. When a predetermined number of samplings are completed, various calculations are performed by executing a program stored in the ROM 12.
[0012]
Here, for various calculations, setting of calculation sections can be input from the keyboard 14 to prevent erroneous determination of calculation data. That is, the arc start and the steady part can be removed from the calculation interval. When the calculation is completed, the various calculation results are compared with the corresponding reference values, and the welding phenomenon is unstable when the difference between any one of each quantitative value and the reference value exceeds a preset allowable range. As a result, an abnormality signal such as a welding current integral value abnormality or an arc / short-circuit time ratio abnormality is output, and a welding quality abnormality such as an irregular bead shape, undercut, or burnout is determined. If the arc discharge is stably formed, an OK signal is output.
[0013]
Next, the calculation of the arc period welding current integral value of subroutine 1 in FIG. 2 will be described.
FIG. 3 shows details of a subroutine for performing arc period welding current integral value standard deviation calculation processing. Calculation of arc period welding current integral value standard deviation, from _one hour after the time-up T, samples the welding current and welding voltage flowing between the welding wire and material to be welded up to the set time T _2, n-th cycle of the welding voltage The welding current measurement is started from the time when the voltage reaches Va or higher, the welding current integral value of the arc period until the time when Va falls below Va is calculated, and then the standard deviation of the integrated value is calculated. The settings of the discrimination voltage Va and the times T ₁ and T ₂ can be freely changed.
[0014]
As shown in FIG. 6, this arc period welding current integrated value represents an arc period welding current waveform for each cycle and an area ∫I _An dt surrounded by the arc time, and its standard deviation σ (∫I _An dt) is It represents the welding current and arc time variation during the arc period at the same time. The fact that the standard deviation of the welding current integral value becomes large means that the droplet transfer phenomenon is unstable due to the occurrence of an instantaneous arc in which the short-circuit phenomenon almost continues or a long-term arc phenomenon that does not lead to a short-circuit. The lower the standard deviation, the more stable the droplet transfer phenomenon.
[0015]
Here, in order to reduce the change of the standard deviation due to sampling noise, chattering, etc., the arc phenomenon within 1 msec is calculated as a short circuit time. The welding current integrated value standard deviation is compared with a reference value, and when the difference from the reference value exceeds a preset allowable range, an abnormal signal is output as an arc period welding current integrated value abnormality.
[0016]
Next, the calculation of the short-circuit period welding current integral value in subroutine 2 in FIG. 2 will be described. FIG. 4 shows details of a subroutine for performing a welding current integral value standard deviation calculation process during the short-circuit period. The calculation of the standard deviation of the welding current integral value during the short-circuiting period is performed by welding flowing between the welding wire and the welded material from the time T ₁ which is the start time of the steady welding measurement to the set time T ₂ which is the end time of the steady welding measurement. The current and welding voltage are sampled, and the welding current measurement is started from the time when the welding voltage V (n) in the n-th cycle reaches the arc / short-circuit determination voltage Va or lower, and the short-circuit period until the time when the current rises to Va or higher is measured. Calculate the welding current integral value, and then calculate the standard deviation of the integral value. The setting of the determination voltage Va and the times T ₁ and T ₂ can be arbitrarily changed.
[0017]
As shown in FIG. 6, this short circuit time welding current integrated value represents the welding current waveform in each short circuit period and the area ∫I _Sn dt surrounded by the short circuit time, and its standard deviation σ (∫I _Sn dt). Represents simultaneously the welding current during the short circuit period and the variation in the short circuit time.
[0018]
The fact that this standard deviation increases means that the short-circuit phenomenon is unstable due to the occurrence of instantaneous short-circuits in which droplet transfer is hardly performed or long-term short-circuits in which the short-circuit phenomenon is not released. Indicates that the droplet transfer is periodically performed.
[0019]
Here, in order to reduce the change of the standard deviation due to sampling noise, chattering, etc., the short-circuit phenomenon within 1 msec is calculated as the arc time. This short-circuit period welding current integrated value standard deviation is compared with a reference value, and when the difference from the reference value exceeds a preset allowable range, an abnormality signal is output as a short-circuit period welding current standard deviation abnormality.
[0020]
Next, the calculation of the standard deviation of the arc / short circuit time ratio in subroutine 3 in FIG. 2 will be described. FIG. 5 shows the details of a subroutine for performing the standard deviation calculation processing of the arc / short-circuit time ratio. From the arc / short time ratio calculation is time T ₁ after timeout of the standard deviation, and sample the welding current and welding voltage flowing between the welding wire and material to be welded up to the set time T _2, n-th cycle of the welding voltage V The measurement of the arc time T _An is started from the time when (n) reaches Va or more, and the arc time until the time when it falls to Va or less, and the time when the welding voltage V (n) in the nth period reaches Va or less. The measurement of the short circuit time T _Sn is started, the short circuit time until the time when the voltage rises to Va or more is measured, the arc / short circuit time ratio is calculated, and then the standard deviation σ ( T _An / T _Sn ) is calculated.
[0021]
The fact that the standard deviation of the arc / short-circuit time ratio increases means that the droplet transfer phenomenon due to the occurrence of instantaneous arc, long-term arc, instantaneous short-circuit, long-term short-circuit, etc. is unstable. Indicates that the transition phenomenon is stable. The standard deviation of the arc / short circuit time ratio is compared with a reference value, and when the difference from the reference value exceeds a preset allowable range, an abnormal signal is output as an arc / short circuit time ratio abnormality.
[0022]
As described above, the welding quality abnormality is monitored only in the termination processing portion excluding the arc start portion and the steady welding portion. The welding end portion processing is attenuated by a specific time constant of the welding wire. This is because the welding phenomenon tends to become unstable because the running portion is melted, and the determination cannot be made according to the criterion of the steady welded portion. Therefore, according to the present embodiment, when the welding phenomenon is stably formed in the termination processing portion, the abnormal signal is not output. For this reason, in an automatic or semi-automatic arc welding apparatus, the unstable state of the welding phenomenon in the termination processing unit can be easily detected by the output of an abnormal signal, and can be easily detected by an operator or engineer. The outflow of non-defective products can be reliably prevented.
[0023]
FIG. 7 is a diagram for explaining a droplet transfer phenomenon, a welding voltage waveform, and a welding current waveform in each stage (A) to (H) during arc welding.
[0024]
【The invention's effect】
As described above, according to the welding stability determination method of the termination processing unit according to claim 1, the welding current and the welding voltage are calculated for any one or more items from (a) to (c) over a predetermined time. When compared with the reference value corresponding to each of them, the welding phenomenon of the termination processing portion is unstable or defective when the difference between any one of the quantitative values and the reference value exceeds a preset allowable range. There is an advantage that it can be determined in real time. In addition, there is an effect that these data can be effectively used as an index for outputting a power supply control signal for automatic recovery processing when a welding abnormality occurs.
[0025]
Furthermore, according to the welding stability determination device of claim 2, the welding stability of the termination processing portion can be monitored accurately and quantitatively in real time during welding, and the outflow of defective welding quality can be reliably prevented. There is an advantage to.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an overall configuration of an embodiment of a termination processing portion welding stability determination device of the present invention.
FIG. 2 is an analysis execution flowchart of the present invention.
FIG. 3 is a subroutine for performing arc period welding current integral value standard deviation calculation processing;
FIG. 4 is a subroutine for performing a welding current integral value standard deviation calculation process during a short circuit period.
FIG. 5 is a subroutine for performing arc / short circuit time ratio standard deviation calculation processing;
FIG. 6 is an explanatory diagram of a droplet transfer phenomenon, a welding voltage waveform, and a welding current waveform during arc welding.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Welding power supply 2 Welding wire 4 Contact tip 5 To-be-welded material 6 Current divider 7 Welding current detection circuit 8 Welding voltage detection circuit 9 A / D converter 10 CPU
16 Display 17 Operation and Output Device

Claims (2)

Termination part of consumable electrode type gas shielded arc welding, in which welding is performed while alternately repeating short-circuiting and arcing, to detect the welding voltage between the welding electrode (hereinafter referred to as the welding wire) and the workpiece to be welded. An analog output signal output using a voltage detection means, and a current detection means for detecting a welding current flowing between the welding wire and the material to be welded, is converted into a digital signal at a predetermined sampling frequency, and input to the calculation means, The following three items that indicate the degree of welding stability of the end treatment part:
(A) Standard deviation σ (∫I _An dt) of the integrated value of the welding current during the arc period for each cycle
(B) Standard deviation σ (∫I _Sn dt) of the integrated value of the welding current during the short-circuit period for each cycle
(C) Standard deviation σ (T _An / T _Sn ) of arc / short-circuit time ratio for each cycle
When any one or more items are calculated and compared with the corresponding reference values, when any one of the differences from the reference value exceeds a preset allowable range, the welding of the termination processing part Is determined to be unstable or defective. A method for determining the welding stability of an arc welding termination treatment section. A consumable electrode type gas shielded arc welding termination treatment unit arc welding stability determination device that performs welding while alternately repeating a short circuit and an arc, and a voltage detection unit that detects a welding voltage between a welding wire and a workpiece, Based on the current detection means for detecting the welding current flowing between the welding wire and the material to be welded, the A / D converter for converting the analog output signal from both means into a digital signal, and the digital signal from the converter,
(A) Standard deviation σ (∫I _An dt) of the integrated value of the welding current during the arc period for each cycle
(B) Standard deviation σ (∫I _Sn dt) of the integrated value of the welding current during the short-circuit period for each cycle
(C) Standard deviation σ (T _An / T _Sn ) of arc / short-circuit time ratio for each cycle
The calculation means for calculating any one or more of the three items and the calculation result from the calculation means are compared with a preset reference value to determine whether the difference from the reference value is within the allowable range. And a display for displaying the output of the comparator. A welding stability determination device for an arc welding termination processing section.

Images