JP7678647B2 - Method for polishing spot welding electrodes - Google Patents

Description

The present invention relates to a method for polishing electrodes for spot welding.

For example, in the assembly process of automobile bodies, spot welding is performed by placing electrodes on multiple steel plates and passing an electric current through them, melting the contact points between the steel plates through resistance heating and forming a nugget as a joint.

Here, the electrodes used in spot welding are subjected to a large pressure at high temperatures and a large current flows during welding, so it is expected that the tip of the electrode will wear and change shape with continued use, or that metal components of the object to be welded will adhere to it. If welding work is continued in this state, the current density will decrease, and there is a risk of poor welding, such as an inability to sufficiently heat the welded area. For this reason, at welding sites, the tip of the electrode is polished, for example, every time it is used a certain number of times, in order to return the tip of the electrode to its shape at the start of welding.

The above-mentioned electrodes are usually polished using a polishing device located near the welding robot. Here, as described in Patent Document 1, for example, the polishing device has a cutter holder with a cutter attached to a recess into which the tip of the electrode can be inserted, and the tip of the electrode can be polished by pressing a pair of electrodes attached to the tip of the welding gun against the recess to clamp the cutter holder and rotating the cutter holder in a fixed direction by the driving force of a motor.

In addition, when the electrode is polished as described above, a specified inspection device is used to inspect the condition of the electrode tip after polishing, and the quality of the polished state of the electrode is judged (see, for example, Patent Document 2).

If the inspection determines that the electrode is in a good polished state, the polished electrode is used for the next spot welding, but if it determines that the electrode is not in a good polished state (not polished enough), the electrode is re-polished using the above-mentioned polishing device (see, for example, Patent Document 3).

On the other hand, Patent Document 4 describes a method of grinding an electrode using a grinding device equipped with a grinding count measuring means for counting the number of times the electrode has been ground, and a grinding count abnormality display means for displaying an abnormality when the number of times the electrode has been ground exceeds a preset maximum number of times the electrode has been ground. It also describes that when an operator visually recognizes the abnormality display described above, the operator recognizes that the number of times the electrode has been ground exceeds the maximum number of times the electrode has been ground, and replaces the grinding blade currently in use with a new grinding blade.

JP 2018-167302 A JP 2002-273535 A JP 2017-87221 A JP 2008-73715 A

In this type of grinding process, attention must be paid not only to the electrodes for spot welding, but also to the wear and tear of the tools (usually grinding blades) that grind the electrodes. In other words, the tools wear out with repeated use, and the grinding ability of the tools also declines. Therefore, if the grinding condition is not deemed to be good even after the inspection after regrinding, a grinding abnormality is detected and the line including the welding process is stopped, and the grinding abnormality is confirmed and dealt with (for example, the grinding time is extended or the grinding blade is replaced, assuming that the cause of the abnormality is a decline in the grinding ability of the tool). However, as described above, if a problem is dealt with after some abnormality occurs, it becomes necessary to stop the line at a time when it is not necessary to stop it, which raises concerns about a decrease in productivity. In addition, it is not desirable in terms of human costs, as it requires the worker to check the abnormality and consider how to deal with it every time an abnormality occurs.

Patent Document 4 describes replacing the grinding blade when the number of times the electrode is ground exceeds a specified number (maximum number of times). However, the degree of wear of the grinding blade depends on the type of plate assembly, the welding state, or the state of wear of the electrode. Therefore, even if the grinding blade is replaced at the predetermined replacement time (when the maximum number of times of grinding is exceeded), if the grinding blade is grounded more frequently than initially expected and the grinding blade is more worn than initially expected, there is a high probability that grinding abnormalities will occur before the blade is replaced.

In light of the above, the technical problem to be solved in this specification is to perform electrode polishing at low cost while maintaining productivity by accurately grasping the wear state of the tools used in electrode polishing.

The above-mentioned problem is solved by the method for grinding a spot welding electrode according to the present invention. That is, this grinding method includes a grinding step for grinding a spot welding electrode with a specified tool, an inspection step for inspecting the grinding state of the electrode ground in the grinding step, and a re-grinding step for re-grinding the electrode based on the inspection results of the grinding state of the electrode obtained in the inspection step, and is characterized in that it further includes a prediction step for counting the number of times re-grinding has been performed and predicting the wear state of the tool based on the count number.

The inventors of the present invention have focused on the number of times that an electrode has been re-ground, and as a result of intensively studying the relationship between the number of times that the electrode has been re-ground and the wear state of the grinding tool, they have found that there is a stronger correlation between the number of times that the electrode has been re-ground and the wear state of the tool than the correlation between the number of times that the electrode has been re-ground and the wear state of the tool. Therefore, as in the present invention, by counting the number of times that the electrode has been re-ground and predicting the wear state of the tool based on the count, the wear state reflecting the usage status of the individual tool can be accurately predicted. According to this, for example, the grinding conditions can be automatically changed according to the predicted degree of wear state of the tool, so that it is possible to maintain a good grinding state for the electrode in the grinding process without the worker having to actually check the condition of the tool and change the grinding conditions. Therefore, excellent productivity can be maintained. In addition, since it is sufficient to only count the number of times that the electrode has been re-ground, it is possible to easily and inexpensively predict the wear state of the tool and maintain a good grinding state of the electrode in the subsequent grinding process, compared to the case where the wear state of the tool is directly detected by a sensor, camera, etc.

In addition, in the method for grinding a spot welding electrode according to the present invention, the prediction process may count the cumulative number of times regrind occurs, and predict the wear state of the tool based on the cumulative count.

In this way, by counting the cumulative number of times regrind has occurred and predicting the wear state of the tool based on the cumulative count, the wear state of the tool can be predicted easily and accurately. Therefore, it becomes possible to accurately make various decisions based on the predicted wear state results, such as whether or not the electrode grinding conditions need to be changed.

In addition, in the method for grinding a spot welding electrode according to the present invention, the prediction process may count the number of consecutive times that regrinding has occurred, and predict the wear state of the tool based on the number of consecutive counts.

During the post-grinding inspection process, due to factors such as the limited inspection methods that can be used within the limited inspection time, a certain number of erroneous judgments (judging the grinding state to be poor when it is actually good) are inevitable. For this reason, by predicting the tool wear state based on the number of consecutive occurrences of regrinding rather than the cumulative number of occurrences of regrinding, it is possible to more accurately predict the tool wear state. Therefore, with this configuration, it becomes possible to make various judgments more accurately based on the results of the prediction of the tool wear state.

The method for grinding a spot welding electrode according to the present invention may further include an extension determination step for determining whether or not it is necessary to extend the grinding time of the electrode in the grinding step, based on the prediction result regarding the wear state of the tool obtained in the prediction step.

As the tool wear progresses, the tool's polishing ability decreases. Therefore, when it is determined (predicted) that the tool wear has progressed to a certain extent, the decrease in the polishing ability of the tool itself can be compensated for by extending the time the tool spends polishing the electrode. Therefore, with this configuration, it is possible to easily maintain a good polished state of the electrode after the polishing process without changing other polishing conditions (such as the tool rotation speed or electrode pressure).

The method for grinding spot welding electrodes according to the present invention may further include a replacement determination step for determining whether or not a notice is required to replace the tool based on the prediction result regarding the wear state of the tool obtained in the prediction step.

On the other hand, even if the decrease in the polishing ability of the tool is compensated for by extending the polishing time, etc., it is inevitable that the tool will reach the end of its useful life (the time when the tool substantially loses the minimum polishing ability required for a polishing tool). In consideration of this point, as in this configuration, it is preferable to determine whether or not to give a notice that the tool should be replaced based on the prediction result regarding the tool wear state obtained in the prediction process. By predicting the tool wear state based on the number of re-grinding counts as in the present invention, the wear state reflecting the individual tool usage status can be accurately predicted. Therefore, the tool's useful life can also be predicted with high accuracy according to the individual usage status, and by determining whether or not to give a notice that the tool should be replaced as described above, it is possible to replace the tool at the appropriate time. Therefore, it is possible to reliably prevent the occurrence of electrode polishing defects after re-grinding and maintain high productivity.

As described above, the method for polishing spot welding electrodes according to the present invention makes it possible to accurately grasp the wear state of the tool used to polish the electrodes, thereby making it possible to polish the electrodes at low cost while maintaining productivity.

2 is a flowchart showing a series of steps from a grinding step to a re-grinding step in a grinding method for a spot welding electrode according to an embodiment of the present invention. 2A to 2C are diagrams illustrating the polishing process shown in FIG. 1 . FIG. 2 is a diagram illustrating the inspection process shown in FIG. 1 . 4 is a flowchart showing a series of steps from a re-grind counting step to a replacement determination step in a grinding method according to one embodiment of the present invention. 5 is a flowchart showing the flow of the regrinding counting step shown in FIG. 4 . FIG. 1A is a graph showing the relationship between the cumulative number of polishings and the cumulative number of re-polishing counts, (b) a graph showing the relationship between the cumulative number of polishings and the number of consecutive re-polishing counts, and (c) a graph showing the relationship between the cumulative number of polishings and polishing time, when a polishing method according to one embodiment of the present invention is carried out. 4 is a flowchart showing a flow of a prediction step and an extension determination step in a polishing method according to one embodiment of the present invention. 1 is a graph showing the relationship between the cumulative number of polishing operations and polishing time when a polishing method according to one embodiment of the present invention is carried out. 3 is a flowchart showing a series of steps from a prediction step to a replacement determination step in a polishing method according to one embodiment of the present invention.

The following describes the method for polishing a spot welding electrode according to one embodiment of the present invention with reference to the drawings.

Figure 1 shows a flowchart illustrating a series of steps from the grinding process to the re-inspection process in a method for grinding a spot welding electrode according to one embodiment of the present invention. As shown in this chart, the grinding method according to this embodiment includes an electrode grinding process S1, an inspection process S2, a re-grinding process S3, and a re-inspection process S4. Each of the processes S1 to S4 will be described in detail below.

(S1) Polishing step In this step, the tip of an electrode that has been used a predetermined number of times (for example, 1 to 5×10 ² times) for spot welding is polished. Here, as an example of an electrode to be polished, an electrode 10 having a partially spherical tip, as shown in FIG. 2, can be given. Of course, the shape of the tip of the electrode 10 is not limited to this, and may be, for example, an electrode having a tip shape consisting of one or more partially spherical surfaces, or an electrode having a known shape, such as an electrode having a flat surface at the tip and a tapered surface continuing from the outer periphery of this flat surface, although both are omitted from the illustration.

The grinding device 20 used in this case has a grinding blade 21 that can be rotated by a motor (not shown). In this case, the grinding blade 21 corresponds to the grinding tool of the present invention. In grinding using this grinding device 20, as shown in FIG. 2, for example, a pair of electrodes 10, 10 and the grinding blade 21 are arranged coaxially, and the pair of electrodes 10, 10 are pressed against the grinding blade 21 while the grinding blade 21 is rotated to grind the tip of each electrode 10. This causes the tip of each electrode 10 to be processed into the shape it will have when it is first used in welding work.

(S2) Inspection Step In this step, the polished state of the electrodes 10 polished in the polishing step S1 is inspected. For example, in this embodiment, an inspection device 30 is disposed between a pair of electrodes 10, and based on the amount of reflected light of light irradiated from the inspection device 30 toward the tip of each electrode 10, it is determined whether or not an unpolished portion such as black skin remains at the tip of the electrode 10, thereby inspecting the polished state of each electrode 10.

If the inspection results show that no unpolished portions remain, the electrodes 10 are in a good polished state (determined as "Yes" in FIG. 1), and the welding operation is resumed (step S21). That is, although not shown, when each electrode 10 is attached to the tip of the arm of a welding robot, the above-mentioned polishing process S1 and inspection process S2 are performed in this attached state, so for electrodes 10 that are determined to be in a good polished state, the arm of the welding robot is moved toward the welding process, and welding of the specified plate assembly is resumed.

Alternatively, if the inspection reveals that there are unpolished areas remaining, it is determined that the polishing condition is not satisfactory (determined as "No" in Figure 1), and the electrode 10 that received the inspection result is polished again.

The above-mentioned inspection method in the inspection process S2 is merely one example. Of course, any known inspection device capable of inspecting the polished state of the tip of the electrode 10 based on criteria other than the amount of reflected light can be widely applied.

(S3) Re-polishing step In this step, re-polishing is performed only on the electrodes 10 that are determined in the inspection step S2 to be in an unsatisfactory polished state. The polishing device used in this step can be the polishing device 20 used in the polishing step S1. For example, the arm of the welding robot is moved from the inspection device 30 toward the polishing device 20, and the electrode 10 is polished by the polishing device 20. The polishing conditions (the number of rotations of the polishing blade 21, the pressure applied to the electrode 10, the polishing time, etc.) are set to be the same as the polishing conditions performed in the immediately preceding polishing step S1, for example. In addition, as described later, when the polishing conditions (here, the polishing time) of the electrode 10 in the polishing step S1 are changed, the polishing conditions in the re-polishing step S3 may be set to be the same as the polishing conditions after the change in the polishing step S1. Of course, the polishing conditions in the re-polishing step S3 may be different from the polishing conditions in the polishing step S1.

(S4) Re-inspection step In this step, inspection of the polished state is performed only on the electrode 10 that has been re-polished in the re-polishing step S3. The inspection device used in this step may be the inspection device 30 used in the inspection step S2, and for example, the arm of the welding robot is moved from the polishing device 20 toward the inspection device 30, and the electrode 10 is inspected by the inspection device 30. In other words, based on the amount of reflected light, it is determined whether or not an unpolished portion remains at the tip of the electrode 10 after re-polishing.

If the reinspection reveals that no unpolished portions remain, it is determined that the electrodes 10 have been properly ground (determined as "Yes" in FIG. 1), and the welding operation is resumed (step S21). That is, as described above, if each electrode 10 is attached to the tip of the arm of the welding robot, the arm of the welding robot is moved toward the welding process, and welding of the specified plate assembly is resumed.

Alternatively, if the reinspection reveals that an unpolished portion remains, it is determined that the re-polishing state of the electrode 10 is not good (determined as "No" in FIG. 1), in other words, it is determined that there is a polishing abnormality, and the line including the welding process is stopped (step S41). In this case, the operator checks, for example, the state of the polishing device 20 including the polishing blade 21, which is a polishing tool, and the state of the inspection device 30, and considers the reason why a good polishing state cannot be obtained even after re-polishing and how to deal with it.

As described above, each time the electrode 10 is used for spot welding a certain number of times, a series of steps from the grinding step S1 to the reinspection step S4 are performed as necessary. That is, in this embodiment, re-grinding (regrinding step S3) is performed once for each grinding (grinding step S1), and based on the inspection result of the inspection after each re-grinding (reinspection step S4), it is determined whether the electrode should be returned to welding work or whether there is a welding abnormality. In this way, spot welding is repeatedly performed using the electrode 10 whose grinding ability has been restored.

Next, the method for managing the grinding tool (here, the grinding blade 21) will be described in detail, mainly based on Figures 4 to 9.

The method for grinding a spot welding electrode according to this embodiment includes the grinding step S1, inspection step S2, re-grinding step S3, and re-inspection step S4 described above, as well as a re-grinding counting step S5, a prediction step S6, an extension determination step S7, and a replacement determination step S8, as shown in FIG. 4. In this case, the re-grinding counting step S5 and the prediction step S6 according to this embodiment correspond to the prediction step according to the present invention. Details of each step will be described in order below.

(S5) Regrinding Counting Step In this step, each time the grinding step S1 is performed, it is determined whether or not regrind has been performed (step S51). If it is determined that regrind has been performed (regrinding step S3), the cumulative number of times regrind has occurred is counted (step S52). This increases the cumulative number of regrinds by one.

When the cumulative number of times regrind has occurred has been counted in this manner, it is then determined whether or not regrind has been performed in the immediately preceding grinding step S1. In other words, it is determined whether or not the above-mentioned regrinds have occurred consecutively (step S53). Then, if regrinds (regrinding step S3) have occurred consecutively, the number of consecutive occurrences of regrinds is counted (step S54). This increases the number of consecutive regrinds counted by one.

On the other hand, if it is determined in step S51 that regrind has not been performed, then process S5 is terminated without counting either the cumulative number of regrinds or the number of consecutive occurrences. Also, if it is determined in step S53 that regrind has not been performed in the immediately preceding grinding process S1, then process S5 is terminated without counting the number of consecutive occurrences of regrind. In this way, each time grinding process S1 is performed once, it is determined whether or not there has been an increase in the cumulative number of regrinds and the consecutive count. Of these, the consecutive count is reset (returns to zero) if not counted.

(S6) Prediction step (S7) Extension determination step When at least one of the cumulative number of occurrences of regrinding and the number of consecutive occurrences is counted in the regrinding count step S5 as described above, the wear state of the grinding blade 21 as a tool is predicted. In this embodiment, as shown in Fig. 7, first, each time the consecutive count number of regrinding increases, it is determined whether or not the consecutive count number is equal to or greater than a preset threshold value (first threshold value) (step S71).

If it is determined that the continuous count number of resharpening is equal to or greater than the first threshold value, it is predicted (determined) that the grinding blade 21 has worn down to the point where it no longer has sufficient grinding ability for the electrode 10, and the grinding conditions are changed. Here, the grinding time is extended (step S72).

Alternatively, if it is determined that the number of consecutive regrinds is less than the first threshold, the process proceeds to a next step of determining whether or not an extension is necessary based on the cumulative count. Then, it is determined whether or not the cumulative count of regrinds is equal to or greater than a preset threshold (second threshold) (step S73).

Here, if it is determined that the cumulative number of resharpening counts is equal to or greater than the second threshold value, it is predicted (determined) that the grinding blade 21 has worn down to the point where it no longer has sufficient grinding ability for the electrode 10, and the grinding conditions are extended (step S72).

Alternatively, if it is determined that the cumulative regrind count is less than the second threshold, i.e., if it is determined that both the continuous count and the cumulative count are less than the corresponding threshold (first threshold, second threshold), steps S6 and S7 are terminated without extending the grinding time.

Figure 6(a) is an example of a graph showing the relationship between the cumulative number of times the electrode 10 has been sharpened (the total number of times the sharpening step S1 has been performed since the sharpening blade 21 was first used) and the number of times re-sharpening has occurred for each sharpening step S1, and the relationship between the cumulative number of times sharpening has occurred and the cumulative number of times re-sharpening has occurred (the cumulative count number). Figure 6(b) is an example of a graph showing the relationship between the cumulative number of times the electrode 10 has been sharpened and the number of times re-sharpening has occurred for each sharpening step S1, and the relationship between the cumulative number of times sharpening has occurred and the number of consecutive times re-sharpening has occurred (the consecutive count number). Figure 6(c) is an example of a graph showing the relationship between the cumulative number of times the electrode 10 has been sharpened and the number of times re-sharpening has occurred for each sharpening step S1, and the relationship between the cumulative number of times sharpening has occurred and the sharpening time.

In this illustrated example, if the threshold value of the continuous count number (first threshold value) is, for example, 5 times and the threshold value of the cumulative count number (second threshold value) is, for example, 10 times, as shown in Figures 6(a) to (c), when the cumulative number of polishing times is 10, the continuous count number of re-polishing is 3 times and the cumulative count number is 4 times, both of which are below the threshold value, so the polishing time is not extended (maintained). When the cumulative number of polishing times is 16 times, the continuous count number of re-polishing is 4 times and the cumulative count number is 8 times, both of which are below the threshold value, so the polishing time is not extended yet. On the other hand, when the cumulative number of polishing times is 17 times, the continuous count number of re-polishing is 5 times, which reaches the threshold value (first threshold value), so the polishing time is extended from Ta to Tb. Note that the extension amount (Tb-Ta) at this time is basically arbitrary and is set appropriately within a range of, for example, 10 to 20% of the polishing time Ta before the extension.

When the sharpening time is extended in this manner, the continuous and cumulative counts of resharpening in the wear state prediction step S6 and the extension determination step S7 are both reset, and the above-mentioned steps S5 to S7 are repeated. Then, after one or more extensions of the sharpening time, a determination is made as to whether or not the sharpening blade 21 needs to be replaced based on the extended sharpening time (replacement determination step S8). Details of the replacement determination step S8 are described below.

(S6) Prediction Step (S8) Replacement Judgment Step In this step, when the sharpening time is extended as described above, it is judged whether or not the sharpening blade 21 as a tool needs to be replaced. In this embodiment, when the sharpening time in the sharpening step S1 is extended in the extension judgment step S7, it is judged each time whether or not the sharpening time is equal to or greater than a preset threshold value (third threshold value) as shown in Fig. 9 (step S81).

If it is determined that the extended sharpening time is equal to or greater than the third threshold value, it is predicted (determined) that the sharpening blade 21 has worn down to the point where it no longer has the minimum sharpening ability required for continued use on the electrode 10, and a warning is given that the sharpening blade 21 should be replaced (step S82).

Alternatively, if it is determined that the extended sharpening time is less than the third threshold, the process proceeds to the next step of determining whether or not the tool needs to be replaced based on the cumulative number of sharpenings. Then, it is determined whether or not the cumulative number of sharpenings since the start of use of the tool (sharpening blade 21) is equal to or greater than a preset threshold (fourth threshold) (step S83).

Here, if it is determined that the cumulative number of times sharpening is equal to or greater than the fourth threshold value, it is predicted (determined) that the sharpening blade 21 has worn down to the point where it no longer has the minimum sharpening ability required for continued use on the electrode 10, and a notice is given to the effect that the sharpening blade 21 should be replaced (step S82).

If a notice is given that the grinding blade 21 should be replaced, the grinding blade 21 will be replaced, for example, at the next equipment operation shutdown (usually at the scheduled equipment operation shutdown, such as for regular line maintenance).

The notice to replace the part can be given in a manner that is visually recognizable to the worker, for example by displaying the notice on a specified monitor or by turning on a lamp indicating that the part should be replaced. Alternatively, the notice to replace the part can be given by voice, so that the worker can hear it.

In addition, if it is determined in step S82 that the cumulative number of sharpening cycles is less than the fourth threshold value, i.e., if it is determined that both the extended sharpening time and the cumulative number of sharpening cycles are less than the corresponding threshold values (third threshold value, fourth threshold value), this process S8 is terminated without giving a notice that the sharpening blade 21 should be replaced (step S84).

Figure 8 is an example of a graph showing the relationship between the cumulative number of times the electrode 10 has been sharpened before and after replacement of the sharpening blade 21, the number of times it has been re-sharpened for each sharpening step S1, and the relationship between the cumulative number of times sharpening has been performed and sharpening time. Note that in Figure 8, the vertical dashed dotted line indicates the point in time when the sharpening blade 21 as a tool was replaced in terms of the cumulative number of times sharpening has been performed. Therefore, at that point in time, the cumulative number of times sharpening has been reset (returned to zero).

Here, if the grinding time is extended according to the same criteria as in the case shown in FIG. 6, the maximum number of times the grinding time is extended is, for example, four times, and the threshold value (third threshold value) of the extended grinding time is Td (the grinding time immediately before the extension to the maximum grinding time Tm), for example, at the time point after the first grinding time extension (at the time point when the grinding time is extended from Ta to Tb), the grinding time Tb after the extension is less than the third threshold value (Td), so no notice is given that the grinding blade 21 should be replaced. Similarly, at the time point after the second grinding time extension (at the time point when the grinding time is extended from Tb to Tc), the grinding time Tc after the extension is less than the third threshold value (Td), so no notice is given that the grinding blade 21 should be replaced. On the other hand, at the time point after the third grinding time extension (at the time point when the grinding time is extended from Tc to Td), the grinding time Td after the extension reaches the third threshold value (Td), so a notice is given at this point that the grinding blade 21 should be replaced. Therefore, when the equipment stops operating after the fourth extension of the grinding time (as shown by the vertically extending dashed line in FIG. 8), the grinding blade 21 is replaced with a new grinding blade. At this point, the cumulative number of grinding operations is reset (to zero), and the above-described steps S1 to S8 are repeated. In this way, the grinding state of the electrode 10 is managed, and the wear state of the grinding blade 21 can be appropriately managed.

As described above, according to the method for sharpening the spot welding electrode of this embodiment, the number of times the electrode 10 has been re-ground is counted, and the wear state of the grinding blade 21 as a tool is predicted based on the count number, so that the wear state reflecting the individual usage status of the grinding blade 21 can be accurately predicted. According to this, for example, the grinding conditions can be automatically changed according to the predicted degree of wear of the grinding blade 21, so that it is possible to maintain a good grinding state for the electrode 10 in the grinding process S1 without the worker having to stop the line, etc., to check the state of the grinding blade 21 and change the grinding conditions. Therefore, excellent productivity can be maintained. In addition, since it is sufficient to only count the number of re-grounds, it is possible to easily and inexpensively predict the wear state of the tool and maintain a good grinding state of the electrode 10 in the subsequent grinding process S1, compared to the case where the wear state of the grinding blade 21 is directly detected by a sensor, camera, etc., for example.

In addition, as in this embodiment, the re-sharpening step S3 is performed once for each grinding step S1, and the wear state of the grinding blade 21 is predicted based on the count number of each re-sharpening, so that the wear state can be predicted more accurately. That is, if the grinding conditions during re-sharpening are set relatively gentle (shorter in the case of grinding time), over-grinding can be suppressed, but the number of re-sharpenings may vary greatly (for example, 0 to 3 times) depending on the state of the electrode 10. In such a case, since the amount of grinding may vary for each re-sharpening, if the re-sharpenings are counted uniformly, the correlation between the count number and the wear state of the grinding blade 21 is likely to be relatively low. In contrast, if the re-sharpening step S3 is performed once for each grinding step S1, the grinding conditions during re-sharpening are set relatively strict (longer in the case of grinding time). In this case, the amount of grinding for each re-sharpening is stable, so a high correlation can be obtained between the various count numbers of re-sharpenings and the wear state of the grinding blade 21. Therefore, by determining whether or not the sharpening conditions need to be changed (here, extending the sharpening time) or whether or not the sharpening blade 21 needs to be replaced based on preset thresholds (first to fourth thresholds) for various resharpening count numbers, it is possible to accurately determine whether or not these needs need to be changed.

In addition, in this embodiment, in the extension judgment step S7, first, it is judged whether or not the grinding time needs to be extended based on the continuous re-grinding count number (step S71), and if it is judged in step S71 that extension is not necessary, it is judged whether or not the grinding time needs to be extended based on the cumulative re-grinding count number. In this way, by first judging whether or not the grinding time needs to be extended based on the continuous count number, it is possible to more accurately predict the wear state of the grinding blade 21 while removing noise such as erroneous detection in the inspection step S2. Also, if it is judged that the grinding time does not need to be extended in the necessity judgment based on the continuous count number, it is possible to detect the state where the grinding blade 21 is significantly worn without fail, and to reliably improve the grinding conditions.

Although one embodiment of the present invention has been described above, the method for polishing spot welding electrodes according to the present invention can have configurations other than those described above without departing from the spirit of the invention.

For example, in the above embodiment, a case has been described in which it is determined whether or not to extend the polishing time based on both the cumulative count number and the continuous count number of repolishing (see FIG. 7), but of course this is not limited to this. For example, it may be determined whether or not to extend the polishing time based on either the cumulative count number or the continuous count number of repolishing. Alternatively, it may be determined whether or not to extend the polishing time based on a count number related to a type of repolishing that is different from both the cumulative count number and the continuous count number.

In the above embodiment, when the polishing time is extended, the continuous and cumulative counts of repolishing in the wear state prediction step S6 and the extension determination step S7 are both reset, and the above-mentioned steps S5 to S7 are repeated. However, this is not necessarily limited to this. For example, multiple thresholds (second thresholds) for extending the polishing time based on the cumulative counts of repolishing may be set, and the polishing time may be extended each time the cumulative count reaches each threshold.

In the above embodiment, the case where the need to extend the grinding time is determined based on the count number for regrind has been described, but of course other conditions may be changed. That is, for example, the rotation speed of the grinding blade 21 may be increased or the pressure applied by the electrode 10 to the grinding blade 21 may be increased based on the count number for regrind.

In the above embodiment, the case was described where the need to replace the sharpening blade 21 was determined based on the extended sharpening time, and the need to give a notice to replace the sharpening blade 21 was determined based on the cumulative number of sharpenings (see FIG. 9), but this is of course not limited to this. For example, step S83 for determining the need to replace the sharpening blade 21 based on the cumulative number of sharpenings may be omitted. Alternatively, the need to replace the sharpening blade 21 may be determined based on a count number related to a type of re-sharpening different from both the extended sharpening time and the cumulative sharpening time, or a numerical value resulting from the count number, for example the cumulative number of occurrences of re-sharpening.

10 Electrode 20 Polishing device 21 Polishing blade 30 Inspection device S1 Polishing process S2 Inspection process S3 Re-polishing process S4 Re-inspection process S5 Regrinding counting process S6 Prediction process S7 Extension determination process S8 Replacement determination process Ta, Tb, Tc, Td Polishing time Tm Maximum polishing time

Claims (5)

a polishing step of polishing the electrode for spot welding with a predetermined tool;
an inspection step of inspecting the polished state of the electrode polished in the polishing step;
and a re-polishing step of re-polishing the electrode based on an inspection result regarding a polished state of the electrode obtained in the inspection step,
a prediction step of counting a cumulative number of times that the regrinding has been performed with respect to a plurality of the electrodes using the same tool , and predicting a wear state of the tool based on the count number. 2. The method for grinding a spot welding electrode according to claim 1, wherein the prediction step includes counting a cumulative number of times the tool has been regrind since the tool was first used, and predicting the wear state of the tool based on the cumulative count number. a polishing step of polishing the electrode for spot welding with a predetermined tool;
an inspection step of inspecting the polished state of the electrode polished in the polishing step;
and a re-polishing step of re-polishing the electrode based on an inspection result regarding a polished state of the electrode obtained in the inspection step,
A prediction step of counting the number of times the regrinding has been performed and predicting a wear state of the tool based on the counted number,
a step of counting the number of times that the regrinding has occurred consecutively in the prediction step, and predicting the wear state of the tool based on the number of consecutive counts. a polishing step of polishing the electrode for spot welding with a predetermined tool;
an inspection step of inspecting the polished state of the electrode polished in the polishing step;
and a re-polishing step of re-polishing the electrode based on an inspection result regarding a polished state of the electrode obtained in the inspection step,
a prediction step of counting the number of times the regrinding has been performed and predicting a wear state of the tool based on the count number, and an extension determination step of determining whether or not it is necessary to extend the grinding time of the electrode in the grinding step based on a prediction result regarding the wear state of the tool obtained in the prediction step. The method for polishing a spot welding electrode according to any one of claims 1 to 4 further includes a replacement determination step for determining whether or not a notice is required to replace the tool based on the prediction result regarding the wear state of the tool obtained in the prediction step.

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