JPS6149793A - Quality discriminating device of electric welding - Google Patents

Abstract

PURPOSE:To discriminate quickly and exactly welding strength, and to improve the work efficiency by reading in advance welding waveform data, determining a nondefective tolerance by setting a reference waveform based on said data, and discriminating the quality of the welding waveform data. CONSTITUTION:When a current is supplied from a welding power source transformer 5, the current flows to metallic wires 3, 4 through each welding electrode 1, 2, and the metallic wires 3, 4 are welded. At the time of this welding, a welding voltage is generated in a measuring standard resistance 6, and this voltage is converted by an analog-digital converter part 7. This digital signal corresponds to a voltage if a voltage waveform of each welding operation, and on the other hand, a nondefective waveform in case when said welding has been executed with sufficient strength is stored in advance as a reference waveform in a memory part 8. This reference waveform and the measured waveform are compared by voltages of plural sample points.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a device for determining whether the welding strength of electric welding is good or bad.

[Technical background of the invention and its problems] One method of welding is resistance welding, in which two types of metal heads are brought together and welded by passing a constant current through them. Conventionally, the strength of this welding has been determined by visually inspecting each welded location after welding.

In contrast, the present inventors have discovered that the strength of welding can be determined by observing the waveform of welding current or welding voltage. For example, the welding waveform generated during welding is guided to an oscilloscope, the waveform is displayed, and the welding waveform is observed and discriminated. However, in this method, it takes time to discriminate the waveform, resulting in poor work efficiency, and there are disadvantages in that accurate waveform discrimination requires skill.

[Purpose of the Invention] This invention has been made in consideration of the above points, and is a method for improving the quality of electric welding, which can quickly and accurately determine the welding strength and can be automated to improve work efficiency. The purpose is to provide a discrimination device.

[Summary of the invention] This invention reads welding waveform data in advance, determines a reference waveform based on it, determines a non-defective acceptable range, and performs a calculation to determine whether or not the welding waveform data falls within the acceptable range. It is used to judge whether the quality is good or bad.

[Embodiments of the invention] An embodiment of the present invention will be described below with reference to the drawings.

In Figure 1, 1.2 is a welding electrode, 3 and 4 are electric Fi1
．． 2 is a metal wire that is supported by and in contact with each other, 5 is a welding power supply transformer, 6 is a standard resistance for measurement, and 7 is an analog-to-digital converter that takes in the voltage generated in the standard resistance for measurement 6 when welding current is applied and directly converts it into digital data. 8 is a memory section, and 9 is a processing device such as a microcomputer that performs a comparison process based on the output from the memory section 8.

The processing device 9 includes a continuous failure counter that counts the number of consecutive failures based on the comparison results, and a total failure counter that counts the total number of failures based on the comparison results.

When a current is supplied from the welding power transformer 5 in the above-described device, the metal wire 3 .
A current flows through the metal wires 3 and 4, and the metal wires 3 and 4 are welded. During this welding, a welding voltage is generated in the standard measuring resistor 6, and this voltage is converted into a digital signal by the analog-to-digital converter section 7.

This digital signal corresponds to the voltage of the voltage waveform for each welding operation, and on the other hand, a good waveform obtained when welding with sufficient strength is stored in advance in the memory section 8 as a reference waveform. In this case, instead of using one non-defective waveform as the reference waveform, the average value of a plurality of welding waveforms may be used as the non-defective waveform, and this may be stored as the reference waveform.

In the present invention, this reference waveform and the measurement waveform are compared based on voltages at a plurality of sample points.

Here, using the waveform shown in FIG. 2(a) as a reference waveform and the waveform shown in FIG. 2(b) as a measured waveform, the comparison operation will be explained with reference to the flowchart of FIG. 3. First, in Fig. 2 <a) and (b), (A) and (A') are the comparison starting voltages,
(8) (B') is the time until the start of comparison, (C) (C
') is the comparison start point, (D) (D') is the sample sampling time interval, (E) is the first tolerance, (F) is the second tolerance, (G) is the time to the tolerance change point, (H)(
H') is the sweep time. Note that each of the counters is cleared prior to the comparison operation.

When the welding operation starts, measurement data is output to the analog-digital converter section 7 in response to the rise of the measurement waveform. The sweep time is counted until the output of the analog-to-digital converter section 7 reaches the comparison start voltage (A) (A').

When the comparison start voltage (A') is reached, the comparison start points (C) and (C') with the reference waveform match. Next, it is compared whether the counted sweep time value has reached the tolerance change time (G). This is because the voltage change in the first half and second half of the voltage waveform is different, as is clear from the drawing.
This is because the tolerance value is changed accordingly to enable more accurate comparison and judgment. In other words, when the tolerance change time (G) has not been reached, the data of the M1 tolerance value (E) is imported, and when the tolerance change time (G) is exceeded, the data of the second tolerance value (F) is imported. and starts the comparison operation. Then, the data value of the measured waveform and the reference waveform are compared for each sample point. That is, if the measurement is within the tolerance change time (G), the first tolerance value (E) is used for comparison for each sample point, and the measurement is within the tolerance change time (G).
If G) is exceeded, a second tolerance value (F) is used for comparison for each sample point. Then, the measurement data is the tolerance value - (E
)CF), the continuous failure counter is reset and a comparison is made to determine whether the sweep time has reached a predetermined value (H) (H'). If the result exceeds (H) (H'), the predetermined comparison is completed, a non-defective product is determined, and a non-defective product signal is generated. Further, as a result of the comparison between the measured data value and the reference waveform, if the tolerance value (E) (F) is exceeded, the continuous failure counter is incremented by 1, and the total failure counter is incremented by 1. If the value of the consecutive defective counter exceeds a predetermined value before the sweep time exceeds a predetermined value (H) (H'), a defective determination is made and a defective signal is generated. Also, when the value of the total defect counter exceeds a preset value, defect determination is performed and a defect signal is generated.

In this way, the predetermined sweep time (
The comparison operation of each sample point is repeated at the sample sampling time interval until H) (H') has elapsed, and if the comparison at all sample points is within the tolerance value (E) (F), the product is good. A signal is generated, and a non-defective signal is also generated when the consecutive number of defective points and the total number of times are both within predetermined values set in advance. Further, when either the consecutive number of defective points or the total number of defective points exceeds a predetermined value set in advance, a defective signal is generated. In this case, the reference setting values for consecutive failures and total failures are determined experimentally or empirically.

In this way, the welding waveform data is read in advance, a reference waveform is set based on it, and an acceptable range for a good product is set. From then on, the measurement data for each weld is checked to determine whether it is within the acceptable range or not. Since pass/fail determination is automatically performed, welding strength can be determined quickly and accurately, and it can be easily incorporated into a production line, improving work efficiency. Also, the starting point for comparison between the reference waveform and the measured waveform is determined by the voltage of both (A>(
A') is used to determine if they match, so even if the start of welding is delayed or ahead of the reference waveform due to effects such as welding resistance, it is possible to ensure that the two waveforms match. This also makes it possible to accurately determine the quality of welding. Furthermore, since the allowable range for the reference waveform is changed between the first half and the second half of the sweep time, it is possible to determine the quality of the welding waveform in accordance with the properties of the welding waveform, making it possible to more accurately determine the quality of the welding.

Note that in the above embodiment, the welding current was converted into a voltage waveform by the resistor 6 and the welding waveform was measured, but the welding voltage is not necessarily limited to this, and the welding voltage can be directly measured to Alternatively, the welding waveform may be measured by measuring the welding power waveform. In addition, in the above embodiment, the pass/fail determination was performed based on the number of consecutive defective points at each point and the total number of times, but the invention is not necessarily limited to this. For example, the area of the waveform portion outside the tolerance range may be calculated. It is also possible to determine the quality of the product by using the same method, and various changes can be made without departing from the gist of the present invention.

[Effects of the Invention] As detailed above, according to the present invention, the welding waveform is read in advance, a reference waveform is set based on the welding waveform, and an allowable range is determined.
Thereafter, welding is judged to be good or bad based on whether the measured welding waveform is within the allowable range, so welding strength can be determined quickly and accurately, and it can be automated to improve work efficiency. It is possible to provide a device for determining the quality of electric welding.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; FIG. 1 is a schematic configuration diagram, FIG. 2 is a waveform diagram showing an example of a reference waveform and a measured waveform, and FIG. 3 is a flowchart showing a quality determination process. 1.2... Welding electrode, 3.4... Metal wire, 5...
Welding power supply transformer, 6... Standard resistance for measurement, 7...
Analog-digital converter section, 8... memory section,
9... Processing device. Applicant's agent Patent attorney Takehiko Suzue Figure 1> $Q

Claims (5)

[Claims] (1) A means for digitizing and reading welding waveform data of electric welding, a means for obtaining and storing reference waveform data from welding waveform data read in advance, and a means for setting a non-defective product tolerance range based on the reference waveform data. 1. An apparatus for determining quality of electric welding, comprising: calculation and determination means for determining whether newly read welding waveform data is within the permissible range or not. (2) The electric welding quality determination device according to claim 1, wherein the welding waveform data is a welding current waveform corresponding to time. (3) The calculation and determination means performs a calculation to compare the read welding waveform data with a non-defective acceptable range at a plurality of points sampled at regular time intervals. A device to determine the quality of electric welding. (4) The electric welding method according to claim 1, 2, or 3, wherein the upper and lower limits of the allowable range for non-defective products are set by adding and subtracting constant values from reference waveform data. Good/failure judgment device. (5) The electric welding quality determination device according to claim 1, wherein the constant values determining the upper and lower limits of the acceptable range of non-defective products are changed within the sweep time of the welding waveform.