JPH07148581A - Welding tip managing device - Google Patents

Abstract

PURPOSE:To extend the life of welding tips by optimizing the time for dressing the tips and finding the abnormality and faults by various kinds of factors from a relation between the number of dotting and the diameter at the front end of the tips. CONSTITUTION:The number C of dotting of the welding tip is counted during welding (S1) and the diameter D at the front end of the welding tip is measured after welding (S2). The diameter D at the front end is compared (S3) with an upper limit value Dmax and the number of dotting attaining the upper limit value of C0=C is stored (S4) when D>Dmax is attained. Tip dressing is then executed (S6). The presence or absence of the abnormality of the initial diameter at the front end after the tip dressing is decided (S8) and the exchange of the blade is executed (S10) at need. The change characteristic of the diameter at the front end with respect to the number of dotting and more specifically the number of dotting attaining the upper limit value C0 are checked (S12) and the factors for the abnormality of the early attainment of the upper limit value of the diameter at the front end are analyzed and an alarm is emitted in case of such abnormality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding tip management device mounted on a welding gun.

[0002]

2. Description of the Related Art Automatic spot welding is performed by a welding robot in an automobile body assembly line or the like. This is done by a pair of welding tips (electrodes) attached to a welding gun from both sides of the welding point of the workpiece. It is pressed and sandwiched for spot welding. Further, in the case where spot welding is continuously performed, tip dressing (shaping of the tip of the welding tip) is performed by a tip dresser at the time when welding is performed for a certain fixed number of points.

The welding tip has a larger tip diameter as the number of hit points increases, and the electrical resistance is reduced due to an increase in the contact area, which makes it difficult to generate heat. , Because it is necessary to cut the tip and shape the tip shape.

[0004]

By the way, FIG. 14 shows the relationship between the number of hit points and the tip diameter of the tip when welding is continuously performed. In a normal state, the tip diameter changes as shown by curve 1, and chip dressing is performed with the number of dots A,
The tip diameter is kept below B. However, when the wear of the welding tip becomes severe for some reason and the tip diameter changes as shown by curve 2 in Fig. 14, the tip diameter is A '(<A)
Although it is already the same as the tip diameter at the normal tip dressing time (number of dots A), tip dressing is not performed until the number of dots reaches A, and therefore the tip diameter becomes B '(> B). Therefore, there is a possibility that the tip diameter exceeds B between the number of points A'and A and welding failure occurs.

Therefore, instead of determining the tip dressing time based on the number of hit points, the length of the welding tip is repeatedly measured as shown in Japanese Patent Laid-Open No. 1-215467, and the amount of change in each measurement or In some cases, if the accumulated change amount exceeds a reference value, it is determined to be abnormal and chip dressing is performed. However, since it is not the length of the welding tip but the tip diameter that is directly related to welding failure, it is not always possible to accurately determine the tip dressing time by detecting the degree of wear from the change in length. Can not.

Further, simply judging the chip dress time,
If the wear of the welding tip is severe due to various factors, it is not possible to extend the life of the welding tip only by performing tip dressing. In view of such conventional problems, the present invention aims to optimize the tip dressing time, and at the same time, to detect abnormalities or failures due to various factors from the relationship between the number of hit points and the tip diameter of the tip, and The purpose is to be able to extend the life.

[0007]

Therefore, according to the present invention, as shown in FIG. 1 (A), a point number counting means a for counting the number of welding points of a welding tip and a tip for measuring the tip diameter of the welding tip. The tip diameter measuring means b, the change characteristic extracting means c for extracting the change characteristic of the tip diameter with respect to the number of welding points of the welding tip, and the tip diameter measured by the tip tip diameter measuring means b are compared with the upper limit value, The tip dressing command means d for shaping the tip of the welding tip by the tip dresser when exceeding and the change characteristic extracted by the change characteristic extracting means c are compared with the reference characteristic, and when they are out of this, the factors And an alarm means e for analyzing and warning
Configure a welding tip management device.

Here, the change characteristic extracting means c may detect the number of hit points when the tip diameter of the welding tip reaches the upper limit value as the change characteristic of the tip diameter with respect to the number of hit points of the welding tip. Alternatively, the curve of the change characteristic may be detected. In addition to the configuration of FIG. 1 (A), as shown in FIG. 1 (B), an initial tip diameter measuring means f for measuring the tip diameter of the welding tip after tip dressing, and a tip diameter of the welding tip after tip dressing. Initial tip diameter determining means g for determining by comparing with the upper limit value and the lower limit value, and tip dress re-commanding means h for performing chip dressing again when the determination result is outside the range of the upper limit value to the lower limit value. It is preferable to provide a chip dresser abnormality determining means i for determining that the chip dresser is abnormal even when the chip dressing is repeated a predetermined number of times outside the above range.

Further, in addition to the structure of FIG.
As shown in (C), a tip length measuring means j for measuring the length of the welding tip, and tip exchange for comparing the length of the welding tip with a lower limit value and exchanging the welding tip when the length exceeds the lower limit value. The command means k may be provided. In addition, FIG. 1 (B)
As indicated by the dotted line in FIG. 1, the tip length measuring means j for measuring the length of the welding tip and the upper limit value and the lower limit value for comparison in the initial tip diameter determining means g are varied according to the length of the welding tip. -It is advisable to provide the lower limit value varying means m.

[0010]

In the above structure, the tip diameter of the welding tip is measured, the measured tip diameter is compared with the upper limit value, and tip dressing is performed when the tip diameter is exceeded. As a result, the tip diameter of the welding tip can always be controlled to be equal to or less than the upper limit value, and the possibility of defective welding can be reduced.

Then, a change characteristic of the tip diameter with respect to the number of welding points of the welding tip is extracted, and the extracted change characteristic is compared with a reference characteristic (relationship between the number of points and the tip diameter of the tip in a normal state) and deviates from this. Sometimes the cause is analyzed and an alarm is issued. This makes it possible to detect abnormalities and failures due to various factors at an early stage based on the relationship between the number of hit points and the tip diameter of the tip and extend the life of the welding tip.

Here, when extracting the change characteristic of the tip diameter with respect to the number of welding tips, the method is simply carried out by detecting the number of points when the tip diameter of the welding tip reaches the upper limit value. The change characteristic curve itself can be detected, and the change characteristic can be more accurately grasped. In addition, the tip diameter of the welding tip is measured after tip dressing, the upper limit value and the lower limit value are compared to make a determination, and based on this determination result, the tip dressing is performed again when the upper limit value to the lower limit value is out of the range. By doing so, it is possible to properly manage the initial tip diameter after tip dressing, and even if the tip dressing is repeated a predetermined number of times, it is determined that the tip dresser is abnormal when it is outside the above range, so that the tip dresser can also be properly handled. Can be managed.

Further, by measuring the length of the welding tip and causing the welding tip to be replaced when it exceeds the lower limit value, it is possible to appropriately manage the timing of exchanging the welding tip. Furthermore,
When the changes in the measured value of the initial tip diameter after the tip dressing are averagely observed when the welding and the tip dressing are repeated after the replacement of the welding tip, the measured value of the initial tip diameter is:
Although it is small at the time of new product (immediately after replacement), it tends to become larger each time the chip dress is repeated, and tends to become maximum immediately before replacement. This is because the shape of the new chip and the chip after dressing are slightly different, but when measuring using a laser beam, for example, the laser beam has a thickness, so even if the tip diameter itself is the same, It is considered that the measured value is different between the new chip and the chip in which the chip dress is repeated, since the measurement is performed including.

Therefore, when the tip diameter of the welding tip after the tip dressing is compared with the upper limit value and the lower limit value to make a determination, the length of the welding tip is measured and compared according to the length of the welding tip. By varying the upper limit value and the lower limit value for use, the accuracy of the chip dresser abnormality determination and the like becomes more appropriate.

[0015]

EXAMPLES Examples of the present invention will be described below. FIG. 2 shows the overall configuration of an embodiment of the present invention. A welding robot 2 is arranged near the robot welding process line 1 and controlled by a robot control panel 3. Incidentally, 4 is a personal computer and 5 is a controller.

A tip dresser 6 is arranged near the welding robot 2 and is controlled by a control interlock board 8 together with a scrap 7 for removing scraps. Here, the laser type line sensor 9 is arranged in the vicinity of the tip dresser 6 so that the tip diameter of the welding tip attached to the tip of the welding gun of the welding robot 2 can be measured. Therefore, this laser type line sensor 9 corresponds to a tip tip diameter measuring means.

FIG. 3 shows the structure of the welding gun portion operated by the welding robot 2. The welding tip 11 is mounted upward on the lower portion of the welding gun 10, and the gun pressurizing air cylinder 12 is provided on the upper portion of the welding gun 10. And a welding tip (13) mounted downwardly through the welding tip (13), and the work piece (14) is pressed and sandwiched by these to perform spot welding. 15 is a spring balancer, 16 is a gun hanger, and 17 is a manual grip switch. Further, 18 is a primary side cable for power supply, 19 is a transformer, 20 is a secondary side cable, and 21 is an auxiliary cable. Further, 22 is an air inlet for gun pressurizing air, 23 is an air regulator, 24 is an electromagnetic valve, 25 is a pressurizing air hose, and 26 is an opening air hose. Also, 27
Is cooling water inlet for gun cooling, 28 is water stop valve, 29
Is a cooling water supply hose, and 30 is a cooling water outlet.

Here, an air pressure sensor 31 is arranged on the air regulator 23 so that the applied pressure can be measured. In addition, a cooling water flow sensor near the cooling water outlet 30
32 is arranged so that the cooling water flow rate can be measured. FIG. 4 shows the structure of the tip dresser 6, in which a sprocket 43 is attached to the tip of the rotation shaft of a motor 42 fixed to the base side of a bracket 41 attached to a base 40, and a belt (or chain) 44 is attached by the rotation of this sprocket 43. The sprocket 45, which is rotatably supported on the tip end side of the bracket 41, is rotatably driven. The sprocket 45 has a cylindrical shape and is provided with a tip shaping blade (cutting blade) 46 on the inner peripheral portion thereof, and the tips of the welding tips 11 and 13 mounted on the welding gun are advanced and pressed against the blade 46. As a result, the tips of the welding tips 11 and 13 are cut and shaped.

FIG. 5 is a flow chart of welding tip management. In step 1 (indicated as S1 in the figure. The same applies hereinafter), the number of hit points C is counted and integrated during welding. In Step 2, after welding (after production of one unit),
Laser-type line sensor 9 for welding tip diameter D
To measure.

In step 3, the measured tip diameter D of the welding tip is compared with a predetermined upper limit value Dmax, and D≤Dm
If ax, continue the next welding as it is, and if D> Dmax, judge that tip dressing etc. is necessary and step 4
Go to. In step 4, as a parameter of the change characteristic of the tip diameter D with respect to the number C of welding tips, the number of points when the tip diameter D reaches the upper limit Dmax (current number of points).
C is stored as the upper limit reaching stroke number C ₀ .

In this embodiment, as the parameter of the change characteristic of the tip diameter with respect to the number of welding tips, the upper limit value hitting point C ₀ is detected, but it is measured every time the tip diameter of the welding tip is measured. The curve of the change characteristic itself may be detected by storing the tip diameter in relation to the number of hit points. In step 5, it is checked whether the life of the welding tip has been reached. Specifically, the length of the welding tip is measured, and it is assumed that it has reached the end of its life if the length is below a predetermined length, or the number of times of tip dressing after replacement of the welding tip is stored, and this is the predetermined value. When the value exceeds the value, it means that the product has reached the end of its life.

If it has not reached the end of its life, the operation proceeds to step 6 where tip dressing is performed by the tip dresser 6 to shape the tip of the welding tip. After the tip dress,
In step 7, the tip diameter D of the welding tip is measured by the laser type line sensor 9. Then, it is determined whether or not the tip diameter D measured in step 8 is abnormal as the initial tip diameter.

If it is determined in step 8 that the initial tip diameter is abnormal after the chip dressing, the process proceeds to step 9 and the initial tip diameter is abnormal after the chip dressing (for example, 2
It is judged whether or not it is continuous), and if it does not occur frequently, it is regarded as a sudden abnormality and the chip dressing (step 6) is performed again in that state. If it frequently occurs, it is presumed that the blade 46 in the tip dresser 6 is not worn or chipped as a cause of the abnormality in the initial tip diameter after the tip dressing.
After instructing the replacement of 46, the chip dressing (step 6) is performed again after the replacement.

As a result of the determination of the tip diameter after tip dressing in step 8, if the initial tip diameter is normal (appropriate value), the process proceeds to step 12. In addition, as a result of the judgment of the chip life in Step 5, if the life is reached,
After proceeding to step 11 and instructing to replace the welding tip, proceed to step 12 after the replacement. In step 12, the change characteristic of the tip diameter D with respect to the number C of the welding tips is checked for conformity with the reference characteristic. This is performed according to the flowchart of FIG. 6 described later.

After the check, in step 13, the number-of-strokes point C is returned to 0 and welding is restarted. Next, the processing contents of the characteristic check (step 12) will be described with reference to the flowchart of FIG. In step 21, the number of dots C of the welding tip
The upper limit reaching stroke number C ₀ , which is a parameter of the change characteristic of the tip diameter D with respect to, is compared with a predetermined value. Proceed to 22.

In step 22, it is judged whether or not such an abnormality in reaching the tip diameter early upper limit value occurs frequently (for example, twice in succession), and if it does not occur frequently, the processing is terminated as a sudden abnormality and the occurrence is frequent. If it is, it is determined to be a chronic abnormality, and the process proceeds to step 23. In step 23, it is determined based on the signal from the air pressure sensor 31 whether or not there is a decrease in the pressing force, and if there is a decrease in the pressing force, the primary side air pressure Drop, air leakage,
Since it can be estimated that the air regulator has failed, step 24
Proceed to to warn of the decrease in pressure, instruct to check the air leak and air regulator.

In step 25, it is judged whether or not the cooling water flow rate is reduced based on the signal from the cooling water flow rate sensor 32. If the cooling water flow rate is reduced, it is determined as a factor of the tip diameter early upper limit reaching abnormality. Since it can be estimated that the flow rate decreases due to an increase in the load of the cooling water circuit, the flow rate decreases due to clogging of the cooling water circuit, etc., the process proceeds to step 26, an alarm is issued for the insufficient cooling water flow rate, and a check of the cooling water circuit is issued.

In step 27, it is determined whether or not the production ratio of the special vehicle type (specifically, the vehicle type used for export) is increased. The vehicle models used for export use rust-preventive treated steel sheets, Durasteel (galvanized steel sheets), etc. If the amount of these increases, the electrical resistance of the plating increases and the chip wear rate increases, so go to Step 28. Go ahead and give instructions to review dress conditions and welding conditions. Specifically, it is advisable to increase the upper limit value Dmax of the tip end diameter for dressing time determination and increase the welding current value.

If none of these apply, step 29
Go to and warn that there is an abnormality of unknown cause. In the present embodiment, the step 1 portion of FIG. 5 corresponds to the hitting point counting means, the step 2 portion of FIG. 5 corresponds to the tip end diameter measuring means together with the laser type line sensor 9, and FIG.
5 corresponds to the change characteristic extraction means, and
The steps 3 and 6 of step 1 correspond to the tip-dress command means, and the step 12 (FIG. 6) of FIG. 5 corresponds to the alarm means.

The step 7 in FIG. 5 corresponds to the initial tip diameter measuring means, the step 8 in FIG. 5 corresponds to the initial tip diameter determining means, and the steps from step 8 to step 9 in FIG. 5 are performed. The portion returning to 6 corresponds to the tip dress re-instructing means, and the portions of steps 9 and 10 in FIG. 5 correspond to the abnormality determining means. Next, another embodiment of the present invention will be described.

In this embodiment, the processing is performed according to the flow charts for managing the welding tips shown in FIGS. Step
At 51, the number of hit points C is counted and integrated during welding.
In step 52, the tip diameter D of the welding tip is measured by the laser type line sensor 9 every time after welding (after production of one unit).

In step 53, every time the tip diameter D of the welding tip is measured, the tip diameter D is stored in relation to the hitting point number C at that time, so that the change characteristic of the tip tip diameter D with respect to the hitting point number C of the welding tip is stored. Memorize In step 54, the curve of the change characteristic of the tip diameter D with respect to the number C of the welding tips is compared with the reference curve.

Here, when the actual curve substantially corresponds to the reference curve illustrated in FIG. 9, it is regarded as normal, and
Continue to step 56. When the actual curve does not correspond to the reference curve, the type illustrated in FIG.
Which of the above is applicable is determined, and processing is performed according to the determination result. In case of type: Due to dust adhesion, etc., it will automatically return to its original position when several points are welded. Therefore, as the processing, the process directly proceeds to step 56.

In the case of the type: If this occurs once, it is considered to be the same as the type, but if it occurs sporadically, it is considered that there is some cause for abnormal wear of the welding tip. Therefore, the routine proceeds to step 55, where an alarm is output, and then the routine proceeds to step 56. In case of type: It is considered that the welding tip is abnormally worn due to explosion or the like. Therefore, the process proceeds to step 57 in order to perform the tip dressing.

In step 56, the measured tip diameter D of the welding tip is compared with a predetermined upper limit value Dmax, and D≤Dm.
When ax, the next welding is continued as it is, and when D> Dmax, it is judged that tip dressing is necessary, and the routine proceeds to step 57. In step 57, tip dressing is performed by the tip dresser 6 to shape the tip of the welding tip.

In step 58, the chip dress count CD is incremented. After the tip dressing, the tip diameter (initial tip diameter) D of the welding tip is measured by the laser type line sensor 9 in step 59. Then, the initial tip diameter D measured in step 60 is set to the upper limit value DOmax and the lower limit value D0min.
By comparing with, it is determined whether or not it is within these ranges (D0min ≦ D ≦ DOmax).

That is, when the measured value of the initial tip diameter after chip dressing is smaller than the lower limit value D0min, the state shown in FIG. Figure 10 due to damage
When the measured value of the initial tip diameter is larger than the upper limit value D0max as shown in FIG. 10C, the state shown in FIG.
Due to the settling of the blade 46, the state shown in FIG.

Therefore, the measured value of the initial tip diameter is the upper limit value D0m.
If it is out of the range from ax to the lower limit value D0min, the process proceeds to step 61, the chip dressing number CD is compared with the predetermined value CD1, and if it is less than the predetermined value CD1, the process returns to step 57 to perform the chip dressing again. . However, when the tip dressing is repeated a predetermined number of times but is out of the above-mentioned range, the blade 46 is damaged or has reached the limit of its settling. Proceed to to output an error, stop the line, and allow blade 46 to be replaced.

Further, although the number of times is not the predetermined number of times (CD1), if the chip dressing is not performed within the above range unless the dressing is performed several times, or if this state is sporadic, the blade 46 begins to bend. Can be regarded as Therefore, if the result of the determination in step 60 is within the range, the process proceeds to step 63, the chip dressing number CD is compared with a predetermined value CD2 (<CD1), and if it is equal to or more than the predetermined value CD2, the process proceeds to step 64. An alarm for instructing replacement of the blade 46 is output.

After the tip dressing and measurement are completed, the process proceeds to step 65. In step 65, the laser type line sensor 9 is used to measure the length L of the welding tip (tip length). In step 66, the measured tip length L is compared with a predetermined lower limit value Lmin, and when L <Lmin, the routine proceeds to step 67, where an alarm for instructing the replacement of the welding tip is output.

In step 67, based on the measured chip length (however, if replaced, the initial chip length after replacement) L, referring to the map, the upper limit value D0m for initial tip diameter determination
Set ax and lower limit value D0min. The reason for this will be described later. Finally, in step 68, the number of hit points C and the number of chip dresses CD are returned to 0, and welding is restarted (return to step 51).

The reason why the upper limit value D0max and the lower limit value D0min for determining the initial tip diameter are made variable according to the chip length L will be described. When the changes in the measured values of the initial tip diameter after the tip dressing are averagely observed when the welding and the tip dressing are repeated after the replacement of the welding tip, the measured values of the initial tip diameter are shown in FIG. As shown in, although it is small at the time of new article (immediately after replacement), it becomes larger each time the chip dress is repeated, and becomes maximum immediately before replacement. This is because the shape of the new chip and the chip after dressing are slightly different as shown in Fig. 12, but the laser beam used for measurement has a thickness, so even if the tip diameter itself is the same, It is considered that the measured values are different between the new chip and the chip in which the chip dress is repeated because the measurement is performed with the chip included.

Therefore, when the tip diameter of the welding tip after tip dressing is compared with the upper limit value and the lower limit value to make a determination, it is necessary to consider the change in the above-mentioned measured value of the tip diameter. Therefore, statistically process the tip length data from immediately after the welding tip replacement to immediately before the lap exchange and the initial tip diameter data after the tip dressing, and show the relationship between the tip length and the initial tip diameter as shown by the dotted line in FIG. Find and figure this relationship
As shown by the solid line in 13, the upper limit value D0max for initial tip diameter determination
And the lower limit value D0min.

Therefore, when comparing the tip diameter of the welding tip after tip dressing with D0max and the lower limit value D0min, the tip length L is measured in advance and the map of FIG. Therefore, by setting the upper limit value D0max and the lower limit value D0min for the initial tip diameter determination, the accuracy of the tip dresser abnormality determination and the like becomes more appropriate.

In this embodiment, the steps shown in FIG.
The portion 51 corresponds to the hitting point counting means, and the step 52 in FIG. 7 is performed.
Together with the laser type line sensor 9 corresponds to the tip diameter measuring means, the step 53 in FIG. 7 corresponds to the change characteristic extracting means, and the steps 56 and 57 in FIG. 7 correspond to the tip dress command means. However, the steps 54 and 55 in FIG. 7 correspond to the alarm means.

The step 59 in FIG. 8 corresponds to the initial tip diameter measuring means, the step 60 in FIG. 8 corresponds to the initial tip diameter determining means, and steps 60 to 60 in FIG.
The portion returning to step 57 via 61 corresponds to the tip dress re-instructing means, and the portions of steps 61 and 62 in FIG. 8 correspond to the abnormality determining means. The step 65 in FIG. 8 corresponds to the chip length measuring means, and the step 67 in FIG. 8 corresponds to the chip exchange commanding means. Further, step 68 in FIG. 8 corresponds to the upper / lower limit value changing means.

[0047]

As described above, according to the present invention, the tip dressing time of the welding tip is determined by measuring the tip tip diameter, so that the tip tip diameter is always kept below the upper limit value to prevent welding failure. The effect that the possibility of occurrence can be reduced is obtained. Then, the relationship between the number of hit points and the tip tip diameter under normal conditions is used as a reference characteristic, and by monitoring the deviation from the reference characteristic, abnormalities and failures due to various factors can be detected early, and the life of the welding tip is extended. The effect that can be obtained is obtained.

Further, when the change characteristic of the tip diameter with respect to the number of welding points of the welding tip is extracted, the method of detecting the number of hit points reaching the upper limit value can be easily carried out, and the curve of the change characteristic itself can be detected. By adopting the method,
It becomes possible to grasp the change characteristics more accurately. Further, after tip dressing, the tip diameter of the welding tip is compared with the upper limit value and the lower limit value for determination, and based on this determination result, when the tip dressing is performed again when it is out of the range of the upper limit value to the lower limit value, The initial tip diameter after the tip dressing can be properly managed, and the tip dresser can be appropriately managed by determining that the tip dresser is abnormal even when the tip dressing is repeated a predetermined number of times and is out of the range.

Further, by measuring the length of the welding tip and causing the welding tip to be replaced when it exceeds the lower limit value, it is possible to properly manage the timing of the welding tip replacement. Furthermore,
When determining the tip diameter of the welding tip after tip dressing by comparing it with the upper limit value and the lower limit value, depending on the length of the welding tip, by varying the upper limit value and the lower limit value for comparison,
The accuracy of the chip dresser abnormality determination is further improved.

[Brief description of drawings]

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

FIG. 2 is a diagram showing the overall configuration of an embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a welding gun portion.

FIG. 4 is a diagram showing a configuration of a chip dresser.

FIG. 5: Flow chart for welding tip management

FIG. 6 Flowchart of characteristic check

FIG. 7 is a flowchart (part 1) of welding tip management of another embodiment.

FIG. 8 is a flowchart (part 2) of welding tip management of another embodiment.

FIG. 9 is a diagram showing an aspect of characteristic determination.

FIG. 10 is a diagram showing an example of an initial tip diameter abnormality.

FIG. 11 is a diagram showing a change characteristic of the initial tip diameter.

[Figure 12] Diagram comparing new chips and those immediately before replacement

FIG. 13 is a diagram showing a relationship between a chip length and an upper limit value and a lower limit value.

[Figure 14] Characteristic diagram of the number of dots-the tip diameter

[Explanation of symbols]

 2 Welding robot 6 Tip dresser 9 Laser line sensor 10 Welding gun 11 Welding tip 12 Air cylinder 13 Welding tip 14 Workpiece 31 Air pressure sensor 32 Cooling water flow sensor 46 Blade

Claims (6)

[Claims] 1. A welding tip management device, which is mounted on a welding gun as a pair and performs spot welding by pressing and sandwiching an object to be welded, comprising: a point number counting means for counting the number of points of the welding tip; Tip tip diameter measuring means for measuring the tip diameter of the tip, change characteristic extracting means for extracting the change characteristic of the tip diameter with respect to the number of welding points of the welding tip, and the upper limit of the tip diameter measured by the tip tip diameter measuring means. When compared with this, when the tip dresser commanding means for shaping the tip of the welding tip by the tip dresser is exceeded, the change characteristic extracted by the change characteristic extracting means is compared with the reference characteristic and deviates from this. Welding tip management device, which is provided with an alarming means for analyzing the cause when it is present and giving an alarm. 2. The change characteristic extracting means detects the number of hit points when the tip diameter of the welding tip reaches an upper limit value as the change characteristic of the tip diameter with respect to the number of hit points of the welding tip. The welding tip management device according to claim 1, which is characterized in that. 3. The welding tip management device according to claim 1, wherein the change characteristic extraction means detects a curve as a change characteristic of the tip diameter with respect to the number of hit points of the welding tip. 4. Initial tip diameter measuring means for measuring the tip diameter of the welding tip after tip dressing, and initial tip diameter determining means for determining the tip diameter of the welding tip after tip dressing by comparing it with an upper limit value and a lower limit value. As a result of the judgment, the chip dressing re-instruction means for performing the chip dressing again when the value is out of the upper limit value to the lower limit value, and it is judged that the chip dresser is abnormal when the chip dressing is out of the range even if it is repeated a predetermined number of times. The welding tip management device according to any one of claims 1 to 3, further comprising: a tip dresser abnormality determination means for performing the above. 5. Tip length measuring means for measuring the length of the welding tip, and tip exchange command means for comparing the length of the welding tip with a lower limit value and exchanging the welding tip when the length exceeds the lower limit value. The welding tip management device according to any one of claims 1 to 4, further comprising: 6. A tip length measuring means for measuring the length of a welding tip, and upper and lower limit values for varying an upper limit value and a lower limit value for comparison in the initial tip diameter determining means according to the length of the welding tip. The welding tip management device according to claim 4, further comprising: a variable unit.