WELDING CONTROL FOR A WELDING SYSTEM, WELDING SYSTEM AND WELDING PROCESS FOR REGULATING THE QUALITY OF A WELDED JOINT PRODUCTION

Abstract

Welding control (10) for a welding system (2), comprising a control device (12) for controlling a welding transformer (24) and a welding tool (21) of the welding system (2), wherein the welding tool (21) is provided for producing at least one welded joint (7) on at least one workpiece (5; 5, 6) and the welding transformer (24) is provided for supplying the welding tool (21) with a welding current (I) for producing the welded joint (7), and a monitoring device (15) for monitoring at least one welding parameter by comparing an actual welding process with a first target welding process (131A; 131B) of the at least one welding parameter when producing a welded joint (7) with the welding tool (21), wherein the first target welding process (131A;131B) was not created under the operating conditions of the welding system (2), wherein the monitoring device (15) is also designed to evaluate the at least one welding parameter to be monitored additionally on the basis of at least one second target welding process (131C) created under the operating conditions of the welding system (2) in order to assess whether the welded joint produced (7) meets the quality requirements or not.;

Description

[0001] The present invention relates to a welding control system for a welding system and a welding process for controlling the quality of the production of a welded joint, which may be, for example, a weld spot, a weld seam, etc.

[0002] Welding systems are used in automated vehicle manufacturing for welding components such as the body of a vehicle, such as a car, truck, or aircraft. Here, as in other manufacturing facilities, such as furniture production lines, metallic parts are joined by welding using a welding tool in a welding system. The vehicle manufacturer must ensure that each weld meets quality standards so that one or more defective welds, for example on a vehicle body, do not pose a danger to vehicle occupants or render the vehicle unusable in the event of an accident.

[0003] Currently, a welding process is being monitored for deviations from target specifications, which are typically determined in the laboratory. Should deviations occur, a controller intervenes to keep the welding process within an acceptable range.

[0004] The problem is that current control mechanisms for welding processes exhibit significant deviations between laboratory and field environments. Consequently, depending on the circumstances, substantial control intervention is required to achieve the required weld quality in a production facility. Even if the resulting weld meets the necessary quality standards, monitoring of the welding system will likely flag it as defective due to the significant control intervention. This can lead to a shutdown of the welding system and ultimately the entire production line, even if the weld itself technically meets the quality requirements.

[0005] One solution would be to increase the overall monitoring tolerance range, or even just for individual welds. However, changing the regulations would mean that the entire welding process would have to be requalified. This would obligate the vehicle manufacturer to re-verify the quality and stability of their welding process. Due to the stringent regulations, this would require a significant investment of time and money from the vehicle manufacturer.

[0006] Alternatively, another controller could be used, but this would also require ensuring the quality and stability of the welding process performed by the vehicle manufacturer. Furthermore, this would necessitate the maintenance of an additional controller. This would result in even greater disadvantages for the vehicle manufacturer in terms of time and cost.

[0007] German patent application DE 103 31 617 A1 discloses a method for recording and monitoring the properties of components in the secondary circuit of resistance welding systems, in particular for determining the milling result of electrode caps, by determining two reference values ​​(welding current values) by short-circuit welding without a workpiece and comparing them in order to detect material fatigue, impurities or altered contact surfaces.

[0008] Another patent application DE 10 2006 038 786 A1 discloses a method for operating a welding device in which a reference data set (e.g. a reference curve) for a welding process is determined by acquiring several raw data sets under real conditions, analyzed (e.g. by removing outliers and averaging) and then stored in the welding control system to enable improved adaptation to different system conditions and to achieve more precise control.

[0009] Another utility model patent application, DE 20 2011 000 875 U1, concerns a control device for process quality, particularly in resistance spot welding, which detects quality deviations and, if necessary, automatically adjusts or readjusts process parameters by storing and evaluating process and quality data in order to achieve a specified process and machining quality and to minimize anomalies such as weld spatter.

[0010] The object of the present invention is to provide a welding control system, a welding system, and a welding process for controlling the quality of a welded joint, with which the aforementioned problems can be solved. In particular, a welding control system, a welding system, and a welding process are to be provided in which individual adjustment of the monitoring of the welded joint production is possible for each welded joint without significant effort.

[0011] This problem is solved by a welding control system for a welding system according to claim 1. The welding control system comprises a control device for controlling a welding transformer and a welding tool of the welding system, wherein the welding tool is provided for producing at least one weld joint on at least one workpiece and the welding transformer is provided for supplying the welding tool with a welding current for producing the weld joint, and a monitoring device for monitoring at least one welding parameter by comparing an actual welding process with a first target welding process of the at least one welding parameter when producing a weld joint with the welding tool, wherein the first target welding process was not generated under the operating conditions of the welding system, and wherein the monitoring device is further configuredThe at least one welding parameter to be monitored is to be additionally evaluated using at least one second target welding process created under the operating conditions of the welding system, in order to assess whether the welded joint produced meets the quality requirements or not.

[0012] The welding control system reliably allows for the monitoring of weld production to be individually adjusted for each weld joint with minimal effort. As a result, while maintaining consistent weld quality, the monitoring of weld quality can be improved. In particular, the desired weld diameter can be achieved for each individual weld point.

[0013] This minimizes downtime of the welding system due to welds that are actually of good quality but are mistakenly classified as defective in a conventional welding system. Thus, the system's error rate can be reduced without the operator having to change their error tolerances or interfere with their already qualified process (minimum spot diameter).

[0014] In particular, the operator of the welding system is not forced to increase the error tolerance for individual weld points or to have the entire welding process of the welding system requalified. This represents a significant time and cost advantage for the vehicle manufacturer.

[0015] Advantageous further embodiments of the welding control system are specified in the dependent claims.

[0016] The monitoring device may be designed to issue a message to the control device if the welded joint produced does not meet the quality requirements.

[0017] It is conceivable that the quality requirements include that a weld point produced as a weld joint has a predetermined weld point diameter, or that a weld seam produced as a weld joint has a predetermined weld seam width and / or a predetermined weld seam length.

[0018] In a special embodiment, the monitoring device is designed to monitor at least one welding parameter during the production of a welded joint with respect to a predetermined tolerance band, in which a deviation of at least one welding parameter from the first target welding path or from the at least one second target welding path is tolerable.

[0019] In another special embodiment, the control device is designed to interrupt the supply of welding current to the welding transformer if a result of the monitoring by the monitoring device shows that the produced welded joint does not meet the quality requirements.

[0020] The at least one welding parameter to be monitored by the monitoring device during the production of a weld joint can be a time-dependent profile of the welding current or the welding voltage or the phase angle or the force exerted by the tool on the at least one workpiece.

[0021] The aforementioned problem is further solved by a welding system for an industrial plant according to claim 7. The welding system comprises a welding tool for producing at least one weld joint on at least one workpiece, a welding transformer for supplying the welding tool with a welding current for producing the weld joint, a control device for controlling the welding transformer and the welding tool of the welding system, and a monitoring device for monitoring at least one welding parameter by comparing an actual welding process with a first target welding process of the at least one welding parameter when producing a weld joint with the welding tool, wherein the first target welding process was not generated under the operating conditions of the welding system, and wherein the monitoring device is further configuredThe at least one welding parameter to be monitored is to be additionally evaluated using at least one second target welding process created under the operating conditions of the welding system, in order to assess whether the welded joint produced meets the quality requirements or not.

[0022] According to one embodiment, the monitoring device is located externally from the control unit. Additionally or alternatively, an operating device is provided to output the message regarding the monitoring result as an output perceptible to human senses. Additionally or alternatively, the welding system is designed to allow parameterization of the monitoring to be performed by the monitoring device via an operating device.

[0023] The welding system described above may also include a device comprising an arm for moving the welding tool in space and a control unit for controlling the arm, the control unit being subordinate to the welding control system. Additionally or alternatively, the detection device may be configured to detect welding parameters during the welding process, with the welding control system being configured to take these detected welding parameters into account when controlling the welding tool.

[0024] The problem is further solved by a welding process for controlling the quality of a welded joint according to claim 10. This process includes a welding tool for producing at least one welded joint on at least one workpiece.

[0025] The procedure comprises the following steps: Control, using a control device, a welding transformer and the welding tool, so that the welding transformer is supplied with a welding current to produce the weld joint; Monitoring, using a monitoring device, of at least one welding parameter by comparing an actual welding profile with a first target welding profile of the at least one welding parameter when producing a weld joint with the welding tool, wherein the first target welding profile was not produced under the operating conditions of the welding system; Evaluation, using the monitoring device, of the at least one welding parameter to be monitored additionally by means of at least a second target welding profile produced under the operating conditions of the welding system, in order to assess whether the produced weld joint meets the quality requirements or not.

[0026] The welding process achieves the same advantages as previously mentioned in relation to welding control.

[0027] Other possible implementations of the invention also include combinations of features or embodiments described previously or subsequently with respect to the exemplary embodiment, even if not explicitly mentioned. In such cases, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention.

[0028] The invention is described in more detail below with reference to the accompanying drawing and by means of exemplary embodiments. The drawing shows: Fig. 1 a highly simplified schematic view of an industrial plant according to a first embodiment with a welding plant which uses a device for guiding a welding tool; Fig. 2 a time course of a welding current I and a resistance R according to a first target welding course, which was determined with a uniform welding current in the operation of the welding system according to the first embodiment; Fig. 3. A representation of a first target curve of another welding parameter during a welding process that was not carried out under the operating conditions of the welding system, as well as several second target curves of the other welding parameter during a welding process that was carried out under the operating conditions of the welding system; Fig. 4 a time course of a welding current I and a resistance R according to a setpoint for a welding process with uniform welding current during intermittent operation of the welding system according to a second embodiment.

[0029] In the figures, identical or functionally equivalent elements are provided with the same reference symbols unless otherwise specified.

[0030] Fig. Figure 1 shows an industrial plant 1 with a welding plant 2. The industrial plant 1 is, for example, a production line for vehicles, furniture, buildings, etc., in which metallic workpieces 5, 6 are joined by welding to create a weld joint 7. In particular, a weld joint 7 can also be created on only one workpiece 5 by joining two edges of the workpiece 5 with the weld joint 7. The workpieces 5, 6 can be made of any weldable material, for example, steel, aluminum, alloys thereof, etc. Any combination of materials is possible.

[0031] The welding system 2 comprises a welding control unit 10, a device 20 for guiding a welding tool 21, a detection device 30, an operating device 40, and a higher-level control device 50, which can control the welding system 2 and / or other components of the industrial plant 1 not shown. Such components include, for example, a transport device for transporting, in particular, at least one of the workpieces 5, 6, one or more further welding systems, one or more other tools, such as a screwdriver, a riveting tool, a drilling tool, a punching tool, etc.

[0032] Welding system 2 is, in particular, a resistance welding system. In this case, welding tool 21 is, in particular, a resistance welding tool.

[0033] The welding control unit 10 comprises a converter 11, a control unit 12, a storage unit 13 for storing data 31, 131 to 133, a communication unit 14 with an input interface 141 and an output interface 142, a monitoring unit 15, and a housing 16. The housing 16 can, in particular, be a control cabinet in which the welding control unit 10 is installed. A cooling device (not shown) is provided, if required, to dissipate heat from the housing 16 of the welding control unit 10.

[0034] The device 20 of Fig. 1 can in particular be a robot. The device 20 moves the welding tool 21 to a joining point on at least one workpiece 5, 6 and holds or moves the welding tool 21 at the joining point accordingly in order to produce, for example, a weld spot and / or a weld seam as a welded joint 7. The welding tool 21 is, for example, a welding gun with at least one electrode cap 22, 23, which is supplied with an electric current for welding, the so-called welding current I, via the inverter 11 and a welding transformer 24. For this purpose, the inverter 11 is supplied by a three-phase voltage network with network phases N1, N2, N3 with an electrical voltage U. NThe inverter 11 is supplied with a three-phase alternating current with a frequency of 50 Hz and a voltage of 400 V or 690 V. Other frequencies, such as 60 Hz, etc., and / or other voltages, such as 110 V, etc., are of course also conceivable. The electrode cap 22, 23 can, for example, be made of copper-chromium-zirconium (CuCrZr), but other materials are also possible.

[0035] When the welding tool 21 is guided by an arm 25 of the device 20, the device 20 is controlled by its control unit 26. For this purpose, the control unit 25 is connected to the welding controller 10 via a communication device 27 using a first connecting line 28 and a second connecting line 29. Relevant data for carrying out a welding process with the welding tool 21 can be exchanged between the welding controller 10 and the device 20, more precisely, the control unit 25, via the connecting lines 28 and 29. Furthermore, parameters of the control unit 26, with which the welding tool 21 is controlled, can be internal basic parameters or setpoints 131 stored in the memory device 13. Any other internal basic parameters and / or setpoints 131 are conceivable.

[0036] The acquisition device 30 acquires acquisition data 31 during the operation of the welding system 2. This data is transmitted via a connecting line 32 to the welding control 10 and stored in the storage device 13. The acquisition data 31 results from the continuous acquisition of data from the welding transformer 24 and / or the welding tool 21 and / or the at least one workpiece 5, 6. This acquisition can be performed either continuously or at a predetermined sampling rate during the creation of a weld joint 7. In the present embodiment, the predetermined sampling rate is selected such that an almost continuous acquisition of the welding process is achieved during the creation of the weld joint 7.

[0037] The operating device 40 is, for example, a keyboard and / or a mouse, a laptop, a touchscreen or non-touchscreen, etc., or combinations thereof. The at least one operating device 40 is used in particular for operating the welding system 2 and for parameterizing the electrode maintenance and adjustment of the welding tool 21. Furthermore, the operating device 40 can provide information to a user regarding the status of the welding system 2 and / or one of its aforementioned components. The status of the welding system 2 includes, among other things, at least one error message 401 about a fault that may occur during the operation of the welding system 2. In addition, the acquisition data 31 can be displayed as an operating indicator 402 using the operating device 40. Furthermore, monitoring results 403 of the welding process can be displayed.Both the error message 401 and the operating indicator 402 and the monitoring results 403 of the welding process are messages on the operating device 40.

[0038] The control unit 12 can access the storage unit 13 and store data 133 in the storage unit 13 or retrieve data 31, 131 to 133 from it. The control unit 12 stores as data 133, for example, the operating data specified by the control unit 12, such as the phase angle of the welding current I and a resistance R of the welding tool 21 when performing a weld or producing a weld joint 7. Any other specified operating data is conceivable.

[0039] During operation of the welding system 2, the inverter 11 supplies the welding transformer 24 with a welding current I based on a corresponding control by the control unit 12. In the present embodiment, the control unit 12 performs a constant current control (CCC) method. With this method, a welding current I ideally establishes itself over time t, as shown in Fig. 2 shown. In the one in Fig. In the example shown, the properties of the respective welding tool 21 and the at least one workpiece 5, 6 ideally result in a resistance R over time t. Consequently, a corresponding voltage U is established between the electrode caps 22, 23.

[0040] The in Fig. 2 The reference welding sequence or first target welding sequence 131A shown with uniform welding current I and the corresponding resistance R for the respective welding tool 21 is in the storage device 13 of Fig. 1 is stored in the data 131. The first target welding process 131A represents a verified quality from the laboratory for controlling a welding process, or the good case, which results in the desired, in particular the best possible, quality for a weld joint 7. The target welding process 131A can, for example, be created in the laboratory under ideal conditions. The first target welding process 131A does not include the actual conditions under which the weld joint is produced in the industrial plant 1.

[0041] Depending on the welding system 2 and the work it performs, corresponding target welding profiles 131A for further workpieces 5, 6 or combinations of workpieces 5, 6 and / or electrode caps 22, 23 are stored in the data 131 in the storage device 13. For example, the welding process parameters of different sheet metal pairings as workpiece combinations can be determined and qualified in the laboratory in order to define predetermined quality requirements or assessments. Various target welding process profiles are stored for each welding process parameter, as for example in Fig. Figure 2 shows that target welding profiles 131A are possible for the voltage U, the phase angle, and the force F. If this parameterization is transferred to a real system 2 and the adaptive control is activated, an (adaptive) controller attempts to regulate the welding process to the profile of the resulting reference resistance profile or target resistance profile, or the reference force profile or target force profile.

[0042] Fig. Figure 3 shows, as a further example of a first target welding profile 131A of a welding parameter during the production of a weld joint 7, a target welding profile of the resistance R during the welding of iron / steel over time t. If it is an aluminum weld, the principle can also be applied to a force profile of a force F over time t, or corresponds to a target welding profile for the force F exerted by the tool 21 on the at least one workpiece 5, 6. The first target welding profile 131A can alternatively represent the welding parameters force F or phase control. The phase control is selected accordingly to set the required welding current I. A tolerance band TA can be arranged around the first target welding profile 131A, which is Fig. 3 is shown very schematically and is described in more detail below.

[0043] Furthermore, in Fig. Figure 3 shows several second target welding profiles 131C for the welding resistance R. The second target welding profiles 131C were previously created, for example, with welding system 2 in industrial plant 1 and resulted in a weld joint that meets the quality requirements 7. Thus, each of the second target welding profiles 131C takes into account the actual conditions under which the weld joint is produced in industrial plant 1. A tolerance band TB can be arranged around the second target welding profiles 131C, which is defined in Fig. Figure 3 is also shown very schematically and is described in more detail below.

[0044] The quality requirements for weld joint 7 include, for example, that a weld point produced as weld joint 7 has a predetermined weld point diameter, or that a weld seam produced as weld joint 7 has a predetermined weld seam width and / or a predetermined weld seam length. Another quality requirement could be that the weld joint 7 is located in a predetermined position, etc.

[0045] As from Fig. 3. The second target welding paths 131C can deviate significantly from the first target welding path 131A.

[0046] The monitoring device 15 is designed to monitor both deviations of the actual welding process, supplied by the acquisition data 31, from the first target welding process 131C, and deviations of the actual welding process from the second target welding processes 131C. Depending on the result, the monitoring device 15 issues a corresponding message to the control device 12. The control device 12 can terminate the supply of welding current I to the welding transformer 24 and thus the welding process if the monitoring device 15 indicates that the weld joint 7 produced does not meet the quality requirements.

[0047] The data 131 according to Fig. 1 include, in addition to the first target welding process 131A of Fig. 2 and Fig. 3 and the second target welding paths 131C from Fig. 3 and / or their characteristics, further internal basic parameters or setpoints of a welding process with the welding tool 21, which can be entered either at the factory or later by a user using the operating device 40. These further internal basic parameters or setpoints can be parameters of the welding tool 21, in particular the maximum contact force to be exerted by the welding tool 21 during welding, the maximum secondary current and / or the minimum secondary current and / or the rated secondary current of the welding transformer 24, etc. In addition, data 132 from the monitoring device 15 can be stored in the storage device 13, as described in more detail below.

[0048] Like the first and second target welding processes 131A, 131C of Fig. 2 are also the recording data 31 welding processes, as previously also in relation to Fig. 3 described. The recorded data are thus 31 actual welding processes, which are compared with the first and second target welding processes 131A, 131C of Fig. 2 or Fig. 3 are comparable.

[0049] During operation of the welding system 2, settings required for the welding processes or welds are set at the operating device 40. During welding, the control unit 12 and / or the storage unit 13 receives the acquisition data 31 from the acquisition unit 30 relating to welds performed with the welding tool 21.

[0050] The acquisition data 31 are monitored and evaluated by the monitoring device 15. For this purpose, the monitoring device 15 accesses the storage unit 13 to monitor and evaluate the acquisition data 31 in relation to the data 131 to 133 stored in the storage unit 13. In particular, the monitoring device 15 evaluates the characteristics of the first and second target welding processes 131A, 131C to check whether the currently performed welding process is proceeding as desired.

[0051] If the monitoring device 15 detects that the current welding process, as recorded in the data 31, deviates from the first target welding process 131A and the second target welding processes 131C, and / or from at least one characteristic of the first target welding process 131A and the second target welding processes 131C, a corresponding message 401 is issued to the operating device 40. Furthermore, the monitoring device 15 can send a corresponding message 401 to the control unit 12 to adjust the control of the welding transformer 24 and / or the welding tool 21. In addition, the monitoring results of the monitoring device 15 can be stored as data 133 in the storage device 13 and also made available to the control unit 25 for the control and, in most cases, regulation of the welding tool 21 and / or the inverter 11 and / or the welding transformer 24.

[0052] If the welding process deviates from the first and second target welding processes 131A, 131C, the monitoring device 15 can also evaluate whether the acquisition data 31 exhibits at least one characteristic of the second target welding processes 131A, 131C and / or corresponds to one of the second target welding processes 131A, 131C. If this is the case, the monitoring device 15 outputs a corresponding error message 401 to the operating device 40. Depending on the error message, the control unit 12 can abort the welding process.

[0053] The monitoring device 15 optionally performs the monitoring taking into account a predetermined tolerance range. The predetermined tolerance range can allow a deviation of the acquisition data 31 within a predetermined range from the first target welding path 131A and / or the second target paths 131C. The predetermined tolerance range can be a predetermined tolerance band between whose upper and lower tolerance limits the target welding paths 131A and 131C lie. Thus, in the example of Fig. 3. It is conceivable to place a predetermined tolerance band around the first target welding path 131A and a second predetermined tolerance band 131C around the second target welding paths 132B.

[0054] This ensures that the welding system 2 is designed, and the control of the welding transformer 24 and the welding tool 21 is implemented in such a way that the operation of the welding system 2 in the industrial plant 1 results in high-quality welded joints 7. Furthermore, genuinely good welded joints are not mistakenly classified as poor.

[0055] According to a modification of the first embodiment, the welding control unit 10, in particular its control device 12, executes an adaptive current control method (ASR) as required instead of a constant current control method (CRC), in which the welding current is automatically adjusted to the current process conditions at the weld joint, especially at the weld point. The aforementioned control methods CRC and ASR ensure improved and more stable weld quality. Monitoring by the monitoring device 15 is performed both in the constant current control method (CRC) mode and when using the adaptive current control method (ASR). Accordingly, corresponding reference curves 131 are also stored. Alternatively or additionally, the monitoring device 15 is designed to detect whether a current increase or decrease originates from the currently active control method or not.Therefore, an increase or decrease in current specified by the adaptive current control procedure (ASR) does not lead to an interruption of the production of the weld joint 7.

[0056] Fig. Figure 4 shows a reference welding process or target welding process 131B, which can be used instead of the reference welding process or target welding process 131A in the welding system 2 according to a second embodiment. Here, the temporal profile of the welding current I and the associated resistance R is only recorded in predetermined time windows T1, which are interrupted by time intervals T2. During the time intervals T2, no profile of the welding current I and the associated resistance R is recorded. Consequently, the detection device 30 also performs a detection operation in the welding system 2 such that detection data 31 are obtained that are comparable to the reference welding process 131A.

[0057] Furthermore, the second target welding profiles 131C are recorded according to the target welding profile 131B, and their characteristics and / or at least one target welding profile itself are stored. In addition, further reference welding profiles or target welding profiles 131B for further electrode caps 22, 23 and / or workpieces 5, 6 or combinations of workpieces 5, 6 may be stored in the data 131.

[0058] This also prevents a weld joint 7 of actually good quality from being mistakenly identified as faulty.

[0059] Otherwise, the welding system 2 is constructed according to the present embodiment as described in relation to the welding system 2 according to the first embodiment.

[0060] According to a third embodiment, the monitoring is configurable with the monitoring device 15. The configuring can be carried out according to a previously set rule, depending on the current settings of the welding system 2. Alternatively, the configuring can be performed by a user at the operating device 40. More generally, the welding system 2 can be configured to query the configuring parameters of the monitoring to be performed by the monitoring device 15 via the operating device 40. The query can be initiated by the monitoring device 15. Alternatively, the query can be initiated by the control unit 12. This allows the intensity of the monitoring to be configurable via a parameter at the operating device 40. The monitoring can also be deactivated via this parameter.

[0061] The parameterization of the present embodiment relates in particular to a tolerance band TA, TB for the aforementioned welding parameters, as shown in Fig. Figure 3 illustrates this schematically. If the measured data 31 lies outside the respective relevant tolerance band TA, TB, the weld joint is of insufficient quality. In this case, it is possible to set the upper limit of the tolerance band TA, TB for the welding current I or the other previously mentioned welding parameters by a predetermined percentage above the first target welding path 131A, 131B and / or the second first target welding path 131C, and to set the lower limit of the tolerance band TA, TB by the same percentage or another predetermined percentage below the respective target welding path 131A to 131B.

[0062] Furthermore, the parameterization of the present embodiment relates in particular to the sensitivity of the movement of the welding tool 21 during the creation of the weld joint. A percentage can be parameterized here, selectable from 0% to, for example, 10%. It is conceivable that the percentage is only adjustable within a predefined range, such as 0% to 5%.

[0063] The percentage values ​​for the aforementioned parameters depend on the respective quality criteria that must be met.

[0064] This method also effectively prevents a weld joint 7 from being mistakenly identified as faulty when it is actually of good quality and can therefore be assessed as acceptable by the monitoring device 15. The monitoring can thus be set separately for each weld joint 7.

[0065] Otherwise, the welding system 2 is constructed according to the present embodiment as described in relation to the welding system 2 according to the first embodiment.

[0066] According to a fourth embodiment, the monitoring device 15 is arranged externally from the welding control 10. In this case, the monitoring device 15 can, for example, access the control unit 12 and the storage unit 13 via a communication device. However, direct access to the storage unit 13 and / or the control unit 12 is also optionally possible.

[0067] All previously described configurations of the welding system 2 and the process it performs can be used individually or in any possible combination. In particular, all features and / or functions of the previously described embodiments can be combined as desired. Additionally, the following modifications are particularly conceivable.

[0068] The parts shown in the figures are schematic and may differ in their exact design from the forms shown in the figures, as long as their previously described functions are guaranteed.

[0069] The industrial plant 1 may have a hand tool instead of the welding tool 21 guided by the device 20. Alternatively, the device 20 may be designed such that the welding tool 21 is a hand-held tool. In addition to one of the aforementioned embodiments for the welding tool 21, it is also conceivable that the industrial plant 1 has at least one other tool, such as a screwdriver, drill, milling tool, riveting tool, cutting tool, punching tool, or stamping tool.

[0070] Industrial system 1 can be a programmable logic controller (PLC). Industrial system 1 can be a CNC (computerized numerical control) controller. Industrial system 1 can be or include a motion logic controller for, for example, transport systems or tool guidance, etc.

Claims

[1] Welding control (10) for a welding system (2), comprising a control device (12) for controlling a welding transformer (24) and a welding tool (21) of the welding system (2), wherein the welding tool (21) is provided for producing at least one welded joint (7) on at least one workpiece (5; 5, 6) and the welding transformer (24) is provided for supplying the welding tool (21) with a welding current (I) for producing the welded joint (7), and a monitoring device (15) for monitoring at least one welding parameter by comparing an actual welding process with a first target welding process (131A; 131B) of the at least one welding parameter when producing a welded joint (7) with the welding tool (21), wherein the first target welding process (131A;131B) was not created under the operating conditions of the welding system (2), wherein the monitoring device (15) is also designed to evaluate the at least one welding parameter to be monitored additionally on the basis of at least one second target welding process (131C) created under the operating conditions of the welding system (2) in order to assess whether the welded joint produced (7) meets the quality requirements or not.; [2] Welding control (10) according to claim 1, wherein the monitoring device (15) is configured to issue a message (401) to the control device (12) if the welded joint (7) produced does not meet the quality requirements. [3] Welding control (10) according to claim 1 or 2, wherein the quality requirements include that a weld point produced as a weld joint (7) has a predetermined weld point diameter or a weld seam produced as a weld joint (7) has a predetermined weld seam width and / or a predetermined weld seam length. [4] Welding control (10) according to one of the preceding claims, wherein the monitoring device (15) is configured to monitor the at least one welding parameter during the production of a welded joint (7) with respect to a predetermined tolerance band (TA, TB) in which a deviation of the at least one welding parameter from the first target welding path (131A; 131B) or from the at least one second target welding path (131C) is tolerable. [5] Welding control (10) according to one of the preceding claims, wherein the control device (12) is configured to interrupt the supply of the welding current (I) to the welding transformer (24) if a result of the monitoring by the monitoring device (15) shows that the produced welded joint (7) does not meet the quality requirements. [6] Welding control (10) according to one of the preceding claims, wherein the at least one welding parameter to be monitored by the monitoring device (15) during the production of a weld joint (7) is a time course of the welding current (I) or the welding voltage (U) or the phase angle or the force (F) exerted by the tool (21) on the at least one workpiece (5; 5, 6). [7] Welding system (2) for an industrial plant (1), comprising a welding tool (21) for producing at least one welded joint (7) on at least one workpiece (5; 5, 6), a welding transformer (24) for supplying the welding tool (21) with a welding current for producing the welded joint (7), a control device (12) for controlling the welding transformer (24) and the welding tool (21) of the welding system (2), and a monitoring device (15) for monitoring at least one welding parameter by comparing an actual welding process with a first target welding process (131A; 131B) of the at least one welding parameter when producing a welded joint (7) with the welding tool (21), wherein the first target welding process (131A;131B) was not created under the operating conditions of the welding system (2), wherein the monitoring device (15) is also designed to evaluate the at least one welding parameter to be monitored additionally on the basis of at least one second target welding process (131C) created under the operating conditions of the welding system (2) in order to assess whether the welded joint produced (7) meets the quality requirements or not.; [8] Welding system (2) according to claim 7, wherein the monitoring device (15) is provided externally from the control device (12), and / or furthermore with an operating device (40) for outputting the message (401) in respect of the monitoring result as an output perceptible by human senses, and / or wherein the welding system (2) is further configured to allow parameterization of the monitoring to be carried out by the monitoring device (15) via an operating device (40). [9] Welding system (2) according to claim 7 or 8, further comprising a device (20) comprising an arm (25) for moving the welding tool (21) in space and a control device (26) for controlling the arm (25), wherein the control device (26) of the device (20) is subordinate to the welding control (10), and / or a detection device (30) for detecting welding parameters when producing a welded joint (7) with the welding tool (21), wherein the welding control (10) is configured to take the detected welding parameters into account when controlling the welding tool (21). [10] Welding method for controlling the quality of a weld joint (7) during the production of the weld joint (7), in which a welding tool (21) is provided for producing at least one weld joint (7) on at least one workpiece (5; 5, 6), the method comprising the steps of controlling, with a control device (12), a welding transformer (24) and the welding tool (21), such that the welding transformer (24) is supplied with a welding current for producing the weld joint (7), and monitoring, with a monitoring device (15), at least one welding parameter by comparing an actual welding profile with a first target welding profile (131A; 131B) of the at least one welding parameter when producing a weld joint (7) with the welding tool (21), wherein the first target welding profile (131A;131B) not created under the operating conditions of the welding system (2), evaluate, with the monitoring device (15), the at least one weld parameter to be monitored additionally on the basis of at least one second target weld path (131C) created under the operating conditions of the welding system (2) in order to assess whether the weld produced (7) meets the quality requirements or not.;

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