Welding quality control equipment

Abstract

The purpose herein is to be able to apply the present disclosure to existing spot welding guns without the use of a dedicated external sensor, and to assist a user in determining the presence or absence of welding defects. This welding quality management device comprises: a storage unit 13 that stores a plurality of welding data files relating to the position of movable electrodes and a current value flowing between the electrodes during a welding period, which are commonly acquired by a plurality of welding robots and are received from the main bodies of the plurality of welding robots or controllers 50 thereof, together with part numbers that individually identify parts to be welded, welding numbers that individually identify the welding points of the parts to be welded, program IDs that identify programs used when welding the parts to be welded, and date and time information; and a retrieval unit 17 that retrieves the plurality of stored welding data files in accordance with retrieval conditions relating to at least one of the part numbers, the welding numbers, the program IDs, and the date and time information, and extracts a plurality of specific welding data files matching the retrieval conditions.

Description

[Technical Field]

[0001] The present invention relates to a welding quality control device. [Background technology]

[0002] In recent years, the use of robotic devices equipped with spot welding guns for welding car bodies and the like has become widespread. In welding operations using spot welding guns, two workpieces to be welded are sandwiched between a movable electrode tip and a fixed electrode tip, and a voltage is applied to the movable electrode tip and the fixed electrode tip while a predetermined pressure is applied, thereby welding the two workpieces. As welding operations become more automated, it has become important to detect welding defects. For example, a technology is known that determines abnormalities in a welded portion based on data acquired by an external sensor (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-10925 Summary of the Invention [Problem to be solved by the invention]

[0004] Methods of detecting abnormalities using external sensors, etc., may not obtain accurate data because the accuracy and sensitivity of the sensors vary depending on the usage environment, which can lead to abnormalities being overlooked. Furthermore, because welding robots must be equipped with external sensors to detect abnormalities, this method may not be applicable to existing welding robots, and if the external sensors are expensive, it can lead to increased costs. If people become accustomed to relying solely on external sensors for abnormality detection, it can lead to a decline in their technical ability to look at the data and determine whether or not an abnormality is truly present. Thus, there is significant room for improvement when it comes to detecting abnormalities such as poor welding in welding robots, and a technology that can be applied universally is particularly desirable. [Means for solving the problem]

[0005] A welding quality control device according to one aspect of the present disclosure includes a receiving unit that receives from a plurality of welding robots or their control devices a plurality of welding data files relating to the position of a movable electrode and the value of a current flowing between the electrodes during a welding period, which are commonly acquired by a plurality of welding robots, along with part numbers that individually identify the parts to be welded, welding numbers that individually identify the welding points of the parts to be welded, program IDs that specify the programs used when welding the parts to be welded, and date and time information; a memory unit that stores the plurality of welding data files in association with the part numbers, welding numbers, program IDs, and date and time information; and a search unit that searches the stored plurality of welding data files according to search conditions related to at least one of the part numbers, welding numbers, program IDs, and date and time information, and extracts a plurality of specific welding data files that match the search conditions. [Effects of the Invention]

[0006] According to this aspect, the present invention can be applied to existing spot welding guns without equipping them with a dedicated external sensor, and can assist users in determining whether or not there is a welding defect through graphs based on welding data files collected from multiple welding robots. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing a welding system including a welding quality control device according to this embodiment. [Figure 2] FIG. 2 is a functional block diagram of the welding robot of FIG. [Figure 3] FIG. 3 is a functional block diagram of the welding quality control device of FIG. [Figure 4] FIG. 4 is a diagram showing an example of a welding quality control page provided by the welding quality control device of FIG. [Figure 5] FIG. 5 is a diagram showing an example of a graph showing the change over time of the electrode position displayed on the welding quality control page of FIG. [Figure 6]FIG. 6 is a diagram showing an example of a graph relating to the amount of variation in plate thickness for each component, which is displayed on the welding quality control page of FIG. [Figure 7] FIG. 7 is a diagram showing an example of a graph showing the change over time in the gun shaft current value displayed on the welding quality control page of FIG. [Figure 8] FIG. 8 is a diagram showing a graph based on welding data files extracted using the date and time associated with the welding data file designated by the user as a search condition. [Figure 9] FIG. 9 is a diagram showing an example of how a graph is displayed when there is a welding data file with an abnormality flag attached. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, a welding quality control device according to this embodiment will be described with reference to the drawings. In the following description, components having substantially the same functions and configurations are designated by the same reference numerals, and redundant description will be given only when necessary.

[0009] As shown in FIG. 1, a welding quality control device 10 according to this embodiment is connected to a plurality of welding robots 20 (20a, 20b) via a network 70 such as a LAN. The welding robots 20 (20a, 20b) are comprised of a welding robot main body and a control device that controls the welding robot main body. The welding robot main body is provided by an articulated arm mechanism 30 (30a, 30b) equipped with a spot welding gun 40 (40a, 40b). The control device is comprised of a robot control device 60 (60a, 60b) that controls the articulated arm mechanism 30, and a welding gun control device 50 (50a, 50b) that controls the spot welding gun 40. The robot control device 60 and the welding gun control device 50 are connected to each other so that they can communicate with each other.

[0010] 2, spot welding gun 40 has a fixed electrode tip 44, a movable electrode tip 45 provided at a position facing fixed electrode tip 44, a fixed arm 42 supporting fixed electrode tip 44, a movable arm 43 supporting movable electrode tip 45 movably along the gun axis, a servo motor 48 generating power for driving the movement of movable arm 43, and an encoder 47 detecting the rotational position of the drive shaft of servo motor 48. Output data from encoder 47 is sent to welding gun control device 50.

[0011] Welding gun control device 50 includes a drive control unit 51, a welding current control unit 52, a current detection unit 53, an electrode position identification unit 54, a storage unit 55, and a communication unit 56. The drive control unit 51 controls the driving of the servo motor 48. Specifically, the drive control unit 51 transmits a pressing force command specified in a welding program to a motor control unit (not shown) at a timing specified in the welding program. The motor control unit supplies a current to the servo motor 48 for generating a torque corresponding to the pressing force command received from the drive control unit 51. As a result, the servo motor 48 is driven with a predetermined torque to achieve the commanded pressing force, and the movable electrode tip 45 is moved along the gun axis in a direction toward or away from the fixed electrode tip 44. The drive control unit 51 may be incorporated into the robot control device 60.

[0012] Welding current control unit 52 controls the welding current supplied to fixed electrode tip 44 and movable electrode tip 45. Specifically, welding current control unit 52 supplies a welding current of a value according to a welding current command specified in a welding program to electrode tips 44, 45 at a timing specified in the welding program.

[0013] The current detection unit 53 detects the value of the current (hereinafter referred to as the gun shaft current value) that flows when electricity is applied between the fixed electrode tip 44 and the movable electrode tip 45. The gun shaft current value can be detected by using an existing method, such as a current sensor.

[0014] The electrode position determining unit 54 determines the position (electrode position) of the movable electrode tip 45, which moves along the gun axis during the welding period, at a predetermined sampling period based on the output of the encoder 47. The welding period here refers to the period from when the movable arm 43 starts moving from a predetermined initial position until the welding is completed and the movable arm 43 returns to the initial position. Because the electrode position is based on the output of the encoder 47, it corresponds to the amount of rotation of the drive shaft of the servo motor 48 and is not a parameter that guarantees the absolute position of the movable electrode tip 45. From the time the movable electrode tip 45 starts moving from its initial position toward the fixed electrode tip 44 until it contacts the workpiece, the electrode position corresponds to a physical absolute position. However, while the movable electrode tip 45 contacts and is being pressed into the workpiece, the electrode position does not correspond to a physical absolute position. The electrode position determining unit 54 may be incorporated into the robot control device 60.

[0015] The storage unit 55 stores information relating to the electrode position identified by the electrode position identifying unit 54 and information relating to the gun shaft current value detected by the current detecting unit 53 .

[0016] Communication unit 56 controls the transmission and reception of various information to and from robot control device 60. Through processing by communication unit 56, welding gun control device 50 sequentially transmits information relating to the electrode position and information relating to the gun shaft current value to robot control device 60, and receives control signals for spot welding gun 40, such as a welding force command and a welding current command, from robot control device 60.

[0017] The robot control device 60 has a processor composed of a CPU, a GPU, etc., a RAM that functions as the processor's main memory, work area, etc., and a storage device in which various programs, various setting information, etc. are stored. The storage device stores a welding program for causing the welding robot 20 to perform a predetermined welding operation. A welding program is prepared for each type of welding object. The welding program describes the positions of the welding points, the order of the welding points, commands for the welding force at the points, commands for the welding current, etc. The welding current contains information on the position of the movable electrode and the value of the current flowing between the electrodes.

[0018] By executing the welding program by the processor, the robot control device 60 functions as a welding robot control unit 61, a plate thickness fluctuation calculation unit 63, an abnormality determination unit 64, a welding data file creation unit 65, an input unit 66, a memory unit 67, and a communication unit 68.

[0019] Welding robot control unit 61 controls welding robot 20. Specifically, welding robot control unit 61 controls articulated arm mechanism 30 in accordance with the welding point positions and welding point order specified in the welding program. Welding robot control unit 61 also transmits welding force commands and welding current commands specified in the welding program to welding gun control device 50 at the timing specified in the welding program. As a result, welding robot 20 performs the welding work specified in the welding program.

[0020] Plate thickness fluctuation calculation unit 63 calculates the amount of fluctuation in plate thickness before and after welding of the welding object based on the change over time in the electrode position received from welding gun control device 50. For example, the amount of fluctuation in plate thickness can be calculated based on the difference between the electrode position when it comes into contact with the welding object and the electrode position when welding of the welding object is completed.

[0021] The input unit 66 inputs user operations to the robot control device 60 via input devices such as a keyboard, mouse, or teaching console. Specifically, the user inputs setting information required for the welding robot 20 to perform a predetermined welding operation into the robot control device 60. The setting information includes a part type ID that identifies the type of welding target and a program ID that identifies the welding program to be used for welding. The memory unit 67 stores various information (electrode position, gun shaft current value) received from the welding gun control device 50 and a welding data file created by the welding data file creation unit 65 (described later). The communication unit 68 controls the transmission and reception of various information between the welding gun control device 50 and the welding quality control device 10. Through processing by the communication unit 68, the robot control device 60 transmits a welding data file related to a welding point to the welding quality control device 10 based on the completion of welding at the welding point. The robot control device 60 also transmits command values ​​specified in the welding program to the welding gun control device 50 and receives information related to the electrode position and the gun shaft current value from the welding gun control device 50.

[0022] The welding data file creation unit 65 compiles data related to the gun shaft current value during the welding period, data related to the electrode position during the welding period, and data related to the amount of variation in the plate thickness of the welding target before and after welding into a data body, and creates a welding data file in which the data body is associated with a robot ID that identifies the welding robot 20, a part type ID that identifies the type of part to be welded, a part number that individually identifies the part to be welded, a welding number that individually identifies the welding point of the part to be welded, a program ID that identifies the welding program used to weld the part, and date and time information. The welding data file is created by the welding data file creation unit 65 each time welding at a welding point is completed, stored in the memory unit 67, and transmitted to the welding quality control device 10. The part type ID and program ID are input by a user. The part number is assigned to each part to be welded as a serial number since welding began. The welding number is specified in the welding program. The date and time information typically includes information related to the welding start date and time and the welding end date and time.

[0023] The abnormality determination unit 64 determines whether the welding was successful. For example, when a power outage or the like occurs during welding, the abnormality determination unit 64 determines that an abnormality occurred during the welding operation and that there is a possibility that the welding has failed. An abnormality flag indicating that the welding was performed under the abnormality determination is attached to the welding data file corresponding to the welding point for which the abnormality determination unit 64 has determined that an abnormality occurred during the welding operation.

[0024] The welding quality control device 10 includes hardware similar to that of a general PC, such as a processor, ROM, RAM, storage device, and input / output interface. A welding quality control program is stored in the storage device. When the processor executes the welding quality control program, the welding quality control device 10 functions as a control unit 11, an input unit 12, a storage unit 13, a communication unit 14, a display unit 15, a search condition setting unit 16, a search unit 17, a graph creation unit 18, and a welding quality control page creation unit 19.

[0025] The control unit 11 controls each unit constituting the welding quality control device 10 in an integrated manner. The input unit 12 inputs user operations via an input device such as a keyboard, a mouse, or a teaching operation panel to the welding quality control device 10. Specifically, search conditions are input in accordance with the user operations to the welding quality control device 10. The search conditions include at least one value of a part type ID, a part number, a welding number, a program ID, and date and time information.

[0026] The communication unit 14 transmits and receives various information to and from the robot control device 60. Through processing by the communication unit 14, the welding quality control device 10 receives a welding data file from the robot control device 60. As already explained, the data body of the welding data file includes data on the electrode position during the welding period, the amount of variation in plate thickness of the parts to be welded before and after welding, and the gun shaft current value during the welding period, and the data body is accompanied by a robot ID, part type ID, part number, weld number, program ID, and date and time information. The welding data file received from the robot control device 60 is stored in the memory unit 13.

[0027] The search condition setting unit 16 sets search conditions by various methods. Specifically, the search condition setting unit 16 sets search conditions in accordance with a user operation via the input unit 12. The search condition setting unit 16 also sets at least one of a robot ID, a part type ID, a part number, a welding number, a program ID, and date and time information associated with a welding data file to which an abnormality flag has been added as a search condition. The search condition setting unit 16 sets at least one of a part type ID, a part number, a welding number, a program ID, and date and time information associated with a welding data file arbitrarily designated by the user as a search condition.

[0028] Search unit 17 searches through a plurality of welding data files stored in storage unit 13 in accordance with the search conditions set by search condition setting unit 16, and extracts a plurality of specific welding data files that match the search conditions.

[0029] Graph creation unit 18 creates multiple graphs showing the change in electrode position over time during the welding period, a graph showing the amount of variation in plate thickness before and after welding for each component, and multiple graphs showing the change in gun shaft current value over time during the welding period, based on the multiple specific welding data files extracted by search unit 17. When a welding data file with an abnormality flag attached is included among the multiple specific welding data files, graph creation unit 18 creates graphs (plots) based on the welding data file with the abnormality flag attached so that they can be distinguished from graphs (plots) based on welding data files without the abnormality flag attached.

[0030] The welding quality control page creation unit 19 creates data for a welding quality control page, which will be described later. The welding quality control page created by the welding quality control page creation unit 19 is displayed on the display unit 15.

[0031] 4 to 9, the welding quality control page created by the welding quality control page creation unit 19 will be described below. The welding quality control page is a page for the user to check the welding quality for each welding point. As shown in FIGS. 4 to 7 , the welding quality control page displays multiple search conditions for the user to input. The search conditions include a “robot ID,” a “part type ID,” a “part number,” a “program ID,” a “welding number,” and a “welding date and time.” For example, if the user wants to check the welding quality of a specific welding point for each part, the user can enter the search conditions “part type ID” and “welding number.” If the user wants to further limit the time of welding, the user can enter the search condition “welding date and time.” If the user wants to further limit the welding robot 20, the user can enter the search condition “robot ID.” If the user wants to further limit the welding program used, the user can enter the search condition “program ID.” In this way, the user can set search conditions by entering search conditions according to the welding point to be checked.

[0032] When a user enters search criteria, the welding quality control page displays a list of data based on multiple specific welding data files that match the search criteria in table format. The user can review the data table and determine whether or not there is a possibility of a welding defect at a specific welding point. Then, when a command to display a graph is entered, such as by clicking the graph output button, graphs showing the time change in electrode position, the amount of plate thickness variation for each component, and the time change in gun shaft current value are displayed, as shown in Figures 4 to 7. In the graph showing the time change in electrode position shown in Figure 4, the vertical axis represents electrode position and the horizontal axis represents time. On the welding quality control pages shown in Figures 4 to 7, these graphs can be displayed by changing the data displayed on the vertical axis or by switching between tabs.

[0033] As shown in Figures 4 and 5, multiple graphs representing the time change in electrode position created by the graph creation unit 18 are time-aligned and displayed together in an overlapping manner. As shown in Figure 6, multiple plots representing the amount of thickness variation are displayed together with the part number on the horizontal axis and the amount of thickness variation on the vertical axis so that specific welding data files can be compared at once. As shown in Figure 7, multiple graphs representing the time change in gun shaft current value created by the graph creation unit 18 are time-aligned and displayed together in an overlapping manner.

[0034] The welding quality control device 10 according to this embodiment provides the following effects. That is, by inputting search criteria displayed on the welding quality control page provided by the welding quality control device 10, a user can extract welding data files that match at least one of the following: the type of welding robot, the type of part to be welded, each part, welding point, date and time, and a combination thereof. The user can then view graphs showing the time variation of electrode position, the amount of plate thickness variation, and the time variation of gun shaft current value based on multiple welding data files that share at least some of the search criteria. By viewing these graphs, the user can determine whether or not there is a possibility of a welding defect at a given welding point. In other words, the welding quality control device 10 according to this embodiment can assist the user in determining whether or not there is a welding defect.

[0035] Multiple graphs showing the time-varying changes in electrode position and multiple graphs showing the time-varying changes in gun shaft current are time-aligned and displayed together, and the amount of variation in plate thickness for each component is also displayed together. This allows users viewing these graphs to more easily determine whether or not there is a welding defect. For example, as shown in Figure 4, when multiple graphs showing the time-varying changes in electrode position all show the same trend, the user can determine that there is no welding defect. On the other hand, as shown in Figure 5, when one of the multiple graphs showing the time-varying changes in electrode position shows a trend that is clearly different from the other multiple graphs, the user can determine that a welding defect may have occurred.

[0036] Of course, the presence or absence of a welding defect can also be determined by viewing other types of graphs. As shown in Figure 6, the variation in plate thickness for part number "005" is clearly smaller than that for other part numbers. Therefore, it can be determined that welding was not performed properly for part number "005" and that an abnormality may have occurred. Furthermore, it may be possible to determine that welding work was performed under abnormal conditions for part numbers "005" and subsequent parts. As shown in Figure 7, when one of multiple graphs showing the time variation of gun shaft current values ​​shows a clearly different trend from the other graphs, the user can determine that a welding defect may exist.

[0037] The possibility of a welding defect can be determined from three types of graphs: a graph showing the change in electrode position over time, a graph showing the amount of variation in plate thickness for each component, and a graph showing the change in gun shaft current over time. This allows for a more accurate determination of the possibility of a welding defect, and also allows for the causes of the welding defect to be analyzed from various perspectives. In addition, the user can obtain knowledge from the trends in the graphs when there is a welding defect and when there is no welding defect.

[0038] In this embodiment, the electrode position, the amount of variation in plate thickness, and the gun shaft current value are used as parameters for determining the possibility of a welding defect. The electrode position and the amount of variation in plate thickness are calculated based on the output of the encoder 47 already equipped in the spot welding gun 40. The gun shaft current value is calculated based on the output of the current detection unit 53 already equipped in the welding gun control device 50 that controls the spot welding gun 40. Because these parameters are used that can be commonly obtained by existing spot welding guns 40, there is no need to equip the welding robot 20 with a dedicated external sensor just for determining the possibility of a welding defect. This method can be applied to existing spot welding guns 40 and is therefore very versatile.

[0039] If an abnormality occurs in the welding robot 20 itself, collecting welding data files from a single welding robot 20 may result in the difference between the graphs not being visible, and the abnormality may go unnoticed and be overlooked. The welding quality control device 10 according to this embodiment can collect multiple welding data files from multiple welding robots 20. As a result, if there are multiple welding robots 20 that perform welding work using the same welding program on the same type of parts, comparing data between the multiple welding robots 20 makes it possible to reliably detect abnormalities in welding by the welding robots 20.

[0040] The welding quality control device 10 according to this embodiment centrally manages multiple welding data files generated by multiple welding robots 20, so that the user does not need to go to the site and operate the welding robot 20 to check the welding data files. The user can access the welding quality control device 10 via the network 70 even from a remote location and check the welding data files.

[0041] In the welding quality control device 10 according to this embodiment, search criteria can be set to at least one of the robot ID, part type ID, part number, welding number, program ID, and date / time information included in the welding data file that is the source of the data for a graph arbitrarily selected by the user from among multiple graphs displayed on the welding quality control page. For example, if a graph (welding point) indicating a possible welding defect is found on the welding quality control page, the welding defect is likely caused by at least one of the welding robot type, part type, part, welding point, welding program, and date / time information specified by the welding information included in the welding data file that is the source of the graph. Furthermore, welding points that were welded under conditions that share at least some of the conditions with the welding point with the possible welding defect may also be defective. For example, if a welding defect is caused by a power outage, welding points that were welded during a similar time period may also have been affected by the power outage. Furthermore, if a welding defect occurs in a specific welding robot 20, other welding points welded by that specific welding robot 20 may also be defective.

[0042] As shown in Figure 7, by selecting a graph that is suspected to be a defective weld from among the multiple graphs displayed on the welding quality control page, the welding information for the welding point corresponding to that graph is displayed. Furthermore, at least one of this welding information can be set as a search condition. This eliminates the need for the user to set search conditions and enables the extraction of welding data files that are likely to have defective welds. Managing welding quality when multiple welding robots are in operation places a heavy burden on managers. In this way, being able to extract and check welding data files that may have defective welds from a single defective weld makes welding quality management easier and reduces the possibility of overlooking defective welds.

[0043] As shown in Figure 7, by specifying date and time information among the search conditions, it is possible to extract welding data files that match or are close to the same date and time "2022 / 09 / 18 11:35" as a specific graph that is suspected to be a welding defect. Then, as shown in Figure 8, it is possible to overlay and display a graph based on the extracted welding data file (extracted graph) and multiple graphs (comparison graphs) based on multiple specific welding data files whose part type ID, welding number, and program ID match those of the extracted welding data file.

[0044] As shown in Fig. 8, by viewing graphs based on welding data files collected from each welding robot 20 on a specific date and time, the user can check whether the graph corresponding to the welding points that were welded around the same time as the date and time when the welding defect occurred shows a similar trend to the other graphs or a clearly different trend, and determine whether there is a welding defect. Here, as shown in Fig. 7, the graphs corresponding to the welding points that were welded around the same time for the welding robot 20 with robot ID "RO1" and the welding robot 20 with robot ID "RO2" show a different trend from the other graphs, so it can be inferred that an abnormality such as a power outage occurred throughout the factory on that date and time.

[0045] In this way, when checking a graph (dot) that indicates a possible welding defect on the welding quality control page, by checking multiple graphs (dots) that share some welding conditions with that graph (dot), it is possible to efficiently determine the cause of the welding defect. Furthermore, when determining the possibility of a welding defect, it is easy to check for similar welding defects by part type, part, dot, program, and date and time, which prevents welding defects from being overlooked.

[0046] When a specific welding data file with an abnormality flag attached is included among the multiple specific welding data files extracted by search unit 17, it is desirable that graphs based on the specific welding data file with the abnormality flag attached be distinguishable from graphs based on specific welding data files without the abnormality flag attached. Therefore, for example, as shown in FIG. 9, graphs based on welding data files with the abnormality flag attached are represented by solid lines, and graphs based on welding data files without the abnormality flag attached are represented by dashed lines. Of course, the graphs may be distinguishable not by the type of line but by the color of the line, or the like. This allows the user to easily identify graphs with abnormality flags attached.

[0047] The form of the welding quality control device 10 according to this embodiment is not limited to this embodiment as long as it can collect welding data from the welding robot 20. For example, the welding quality control device 10 may be directly connected to the welding robot 20 via a cable. Furthermore, the welding quality control device 10 may be connected wirelessly or by wire to an overall control device such as a PLC that controls a plurality of welding robots 20 in an overall manner.

[0048] In this embodiment, the functions of electrode position specifying unit 54 and plate thickness variation amount calculation unit 63 are provided on the welding robot 20 side. However, as long as the electrode position and plate thickness variation amount can be calculated based on the output of encoder 47, all or part of these functions may be provided by welding quality control device 10. Also, some or all of the functions of welding quality control device 10 may be provided by welding robot 20. Furthermore, some of the functions of robot control device 60 and welding quality control device 10, for example, the functions of memory unit 13 of welding quality control device 10, may be provided by an external device.

[0049] In this embodiment, the welding data file contains three parameters: electrode position, plate thickness variation, and gun shaft current value, and three types of graphs based on each parameter can be displayed. However, if the user can determine welding points that may have welding defects, the welding data file only needs to contain at least one of the three parameters.

[0050] In this embodiment, the welding data file includes a robot ID, a part type ID, a part number, a welding number, a program ID, and date and time information. However, because the part type can be uniquely identified once the welding program is determined, the part type ID need not be included as additional information. Furthermore, even if the part type is the same, performance may vary depending on the factory where it was produced. Therefore, the welding data file may include a rod ID for identifying the production rod of the part type. Furthermore, the spot welding gun 40 attached to the articulated arm mechanism 30 may be changed for maintenance or other reasons. Therefore, the welding data file may include a gun ID for identifying the spot welding gun 40. In addition to these, the welding data file may include various parameters that may affect the welding operation, such as weather, temperature, humidity, the installation location of the welding robot 20, and the elapsed time since maintenance of the welding robot 20. These parameters may be set as search conditions.

[0051] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention described in the claims and their equivalents. [Explanation of symbols]

[0052] 10...welding quality control device, 11...control unit, 12...input unit, 13...memory unit, 14...communication unit, 15...display unit, 16...search condition setting unit, 17...search unit, 18...graph creation unit, 19...welding quality control page creation unit.

Claims

1. A welding quality control device connected to a plurality of welding robots, a receiving unit that receives, from the plurality of welding robots or their control devices, a welding data file relating to the position of a movable electrode and the value of a current flowing between the electrodes during a welding period obtained by the plurality of welding robots, together with part numbers that identify parts to be welded, weld numbers that identify welding points on the parts to be welded, program IDs that identify programs used when welding the parts to be welded, and date and time information; a search unit that searches the welding data files according to search conditions related to at least one of the part number, the welding number, the program ID, and the date and time information, and extracts welding data files that match the search conditions; a graph creation unit that creates at least one of a plurality of graphs showing a change in the position of the movable electrode over time and a plurality of graphs showing a change in the current value over time based on the extracted welding data file; a display unit that displays a plurality of graphs created by the graph creation unit in an overlapping manner; A welding quality control device equipped with:

2. The welding quality control device according to claim 1 , further comprising a search condition setting unit that sets, as the search condition, a value relating to at least one of the welding number, the part number, the program ID, and the date and time information in accordance with a user operation.

3. a search condition setting unit that sets, as the search condition, a value related to at least one of the welding number, the part number, the program ID, and the date and time information associated with a welding data file arbitrarily designated by a user; 2. The welding quality control device according to claim 1, wherein the welding data file extracted by the search unit has at least one of the welding number, the part number, the program ID, and the date and time information in common with the specified welding data file.

4. a search condition setting unit that sets, as the search condition, a value related to at least one of the welding number, the part number, the program ID, and the date and time information associated with a welding data file to which information indicating an abnormality during welding work is added; 2. The welding quality control device according to claim 1, wherein the welding data file extracted by the search unit has at least one of the welding number, the part number, the program ID, and the date and time information in common with a welding data file to which information indicating an abnormality during the welding work is attached.

5. 2. The welding quality control device according to claim 1, wherein the welding data file includes data relating to a variation in plate thickness of the welding object before and after welding.

6. The graph creation unit creates a graph showing the amount of thickness variation of the welding object before and after the welding, together with at least one of a plurality of graphs showing the time change in the position of the movable electrode and a plurality of graphs showing the time change in the current value, based on the extracted welding data file, The welding quality control device according to claim 5 , wherein the display unit displays at least one of the plurality of graphs and a graph showing a thickness variation of the welding object before and after welding.

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