welding device

Abstract

Welding device (1), in particular for joining sheet metal elements (2) for motor vehicles by welding, comprising a welding gun device (3), in particular a servo welding gun, which has a displacement detection device (9) designed to detect displacement information, in particular a displacement traveled, of at least one welding gun element (4, 5) of the welding gun device (3) and a force detection device (10) designed to detect force information relating to a force acting on at least one welding gun element (4, 5) of the welding gun device (3), wherein the welding device (1) is designed to determine a force-displacement relationship based on a first displacement information realized at a first force value and a second displacement information realized at a second force value and to determine a target displacement information for a specific welding force in a welding process based on the force-displacement relationship.

Description

[0001] The invention relates to a welding device, in particular for joining sheet metal elements for motor vehicles by means of welding, comprising a welding gun device, in particular a servo welding gun, which has a displacement detection device designed to detect displacement information, in particular a distance traveled, of at least one welding gun element of the welding gun device and a force detection device designed to detect force information, which relates to a force acting on at least one welding gun element of the welding gun device.

[0002] Welding devices used to join sheet metal elements, for example for motor vehicles, by means of welded joints, wherein these have a welding clamp device, for example a servo welding clamp, with which the sheet metal elements to be welded are gripped and subjected to a welding force and are welded together by applying a welding current that flows between the welding clamp elements through the sheet metal elements, are generally known from the prior art.

[0003] Such welding devices typically include a force detection unit designed to detect and monitor the welding force applied to the sheet metal elements by the welding gun elements. Additionally, displacement information can be recorded, describing the path traveled by at least one welding gun element during the welding process. However, such displacement detection units usually have a comparatively low resolution or accuracy with respect to the displacement being measured.

[0004] When loading the welding machine with sheet metal components, for example, when a worker feeds them in or a robot removes them, multiple removals can occur due to the relatively small sheet thickness, especially <1 mm. This can lead to at least one sheet metal component being picked too many for a specific joint. Alternatively, it is also possible, for example, when three or more sheet metal components are being welded together, that one of the components is missing, for instance, if too few components were fed in.

[0005] This can lead to an inadequate weld, for example, if the required boundary conditions cannot be met for the weld point in question. It is generally understood that each weld point is welded with defined parameters, such as a specific welding force and current. If a sheet metal element is gripped too much or too little, the weld will be faulty. If such a defect goes unnoticed, it can lead to costly rework or even the loss of the partially manufactured product, such as a motor vehicle, if rework is no longer possible.

[0006] Separate detection devices are also known that are designed to monitor the number of sheet metal elements, for example, by means of a comparatively high-resolution or precise measurement of the total sheet thickness. However, such detection devices represent an additional expense for the welding equipment and thus an increase in the associated costs, maintenance, and the like, and may potentially slow down the process if additional time is required for measuring the sheet thickness or the number of sheet metal elements. Another possibility is to monitor the welding current to determine whether the number of sheet metal elements corresponds to the desired number. However, this approach typically does not allow for the determination of an exact sheet thickness and therefore also does not provide a clear indication of the number of sheet metal elements between the welding gun elements.

[0007] The invention is based on the objective of providing an improved welding device in which monitoring of the welding process is less costly.

[0008] The problem is solved by a welding device according to claim 1. The dependent claims relate to possible embodiments.

[0009] As described, the invention relates to a welding device specifically designed for joining sheet metal components for motor vehicles by welding. The welding device comprises a welding gun assembly, for example, a servo welding gun. The welding gun assembly, in turn, includes a force sensing device and a displacement sensing device. The force sensing device and displacement sensing device can be integrated into an assembly or unit. For example, the force sensing device and the displacement sensing device can be integrated into an adjusting device, for example, an adjusting cylinder, of the welding gun assembly, which is designed to move the welding gun elements of the welding gun assembly, for example, to open and close them with an adjustable force.

[0010] In other words, the welding gun is used to weld sheet metal elements at predetermined welding points. For this purpose, the sheet metal elements to be welded are positioned between the welding gun elements of the welding gun. The welding gun elements are then closed and moved against each other, applying the welding force. The sheet metal elements are positioned between the welding gun elements and are thus also subjected to the welding force. Once the welding force is applied, the welding current can flow through the welding gun elements and thus through the sheet metal elements to weld them together. Specifically, the welding device described herein can be used for resistance spot welding, or it can be configured for resistance spot welding.Accordingly, the resistance spot welding method described herein can be carried out, in particular using the welding device described herein.

[0011] The invention is based on the understanding that the welding device is designed to determine a force-displacement relationship based on a first displacement information realized at a first force value and a second displacement information realized at a second force value, and to determine a target displacement information for a specific welding force in a welding process based on this force-displacement relationship. In principle, it is therefore proposed that the force and displacement measuring devices, which are already provided for the operation of the welding gun, be used to monitor the welding process in the welding device described herein. By establishing and determining the force-displacement relationship, the force and displacement measuring devices can thus be used for a purpose for which they were not originally designed.

[0012] As described at the outset, the displacement measurement device alone typically lacks the accuracy required to ensure that the correct number of sheet metal elements are gripped between the welding gun elements. Since the displacement information also changes with the applied welding force, as the welding gun elements can deform under this force, the displacement information alone, or as the sole criterion, is unsuitable for determining whether the total sheet thickness corresponds to the required number of sheet metal elements.

[0013] It is therefore proposed to first establish or determine a force-displacement relationship for the welding gun assembly. For this purpose, the welding gun assembly is closed at an arbitrary initial force value, for example, 500 to 1500 N, specifically 1000 N. This determines the first displacement information, which, as described, can describe the distance between the welding gun elements, the position of the welding gun elements relative to each other, or indirectly, the position or state of an adjusting cylinder.

[0014] In a further step, the welding clamp is closed with a second force value, which differs from the first. This second force value can also be chosen arbitrarily and can, for example, correspond to the highest welding force occurring during operation of the welding device. The second force value can also be above or below such a welding force. By way of example, the second force value could be between 3000 N and 5000 N, specifically 4000 N. Once the second force value is applied, the second position information is determined. The first and second position information are determined, in particular, when the welding clamp is empty, i.e., when no sheet metal elements are gripped.

[0015] Accordingly, when the first and second force values ​​are applied, the displacement information will change, resulting in a difference between the first and second displacement information. The invention therefore proposes to determine the force-displacement relationship based on the relationship between the first force value and the first displacement information, and the second force value and the second displacement information. In particular, a linear relationship can exist or be determined, such that the larger the realized force value, the greater the corresponding displacement information. Applying the first force value can, for example, also account for a basic bending or initial deformation of the welding gun elements, or for idle operation. Advantageously, the first force value can be lower than all welding forces that occur during the operation of the welding device.

[0016] Based on the defined or established force-displacement relationship, it is then possible to determine target displacement information for any welding forces occurring in the welding process. In other words, knowing the force-displacement relationship for a specific welding force—which, for example, lies between the first and second force values, or is arbitrarily relative to them—it is possible to determine the target displacement information that should be achieved when this specific welding force is applied. Advantageously, it is therefore possible to verify during the welding process whether the target displacement information is actually being realized or whether a deviation occurs, which could be caused, for example, by an incorrect number of sheet metal elements to be welded together, such as an extra sheet metal element being included or a sheet metal element being missing.

[0017] The welding device can further be configured so that the target position information includes a specific total sheet thickness of the sheets arranged between the welding clamp elements during the welding process. The welding device is designed to compare actual position information acquired by the position detection device for the welding process with the target position information for the welding process. In other words, when the welding process is carried out with the welding device, the actual position information resulting at a weld point under a specific welding force can be determined by the position detection device. In this case, the at least two sheet metal elements are gripped between the welding clamp elements.

[0018] For the corresponding weld point, the target displacement information can be determined, for example, calculated, based on the force-displacement relationship as described previously. This calculation can take into account how many sheet metal elements are being welded, so that the total sheet thickness, for example, of two or three sheet thicknesses, is included in the target displacement information. In other words, it is possible to predict what target displacement information should be set for a specific weld point when the correct number of sheet metal elements are used.

[0019] By comparing the target path information with the actual path information, it is possible to determine whether the total sheet thickness is correct, whether a sheet metal element is missing, or whether an extra sheet metal element has been gripped. If deviations occur, for example, if the actual path information is greater than the target path information, especially above a certain threshold, it can advantageously be detected that an additional sheet metal element has been gripped. In this case, as described in detail below, at least an inspection or rework of the product can be carried out.

[0020] The welding device can, in a further embodiment, be configured to determine different target displacement information for at least two different welding processes, in particular for welding points. As described, individual welding points, where sheet metal elements are to be welded together using the welding device, can differ with respect to the welding force to be applied by the welding gun. Based on the described force-displacement relationship, different target displacement information can be determined for these points using the welding device. This means that the change in the welding gun's position at different welding forces can be taken into account in the force-displacement relationship.This allows the corresponding target path information to be determined at each of the different welding points based on the welding force applied at that welding point and compared with the actual path information recorded during the execution of the welding point.

[0021] In one embodiment of the welding device, the device can be configured to acquire the actual displacement information and / or the force information within a specific time interval of less than 100 ms. Advantageously, monitoring the number of sheet metal elements or the welding process itself, ensuring that the number of elements used does not deviate from the desired number, can therefore be performed relatively quickly. Thus, the monitoring described herein, particularly based on the force-displacement relationship, does not result in any additional effort, as no additional acquisition devices are required, and the execution of the welding process is not, or at least not significantly, prolonged. Specifically, the force-displacement relationship can be determined even before the actual welding process begins.After closing the welding gun, a defined holding time is typically observed in the prior art to ensure the correct build-up of welding force. This holding time can be, for example, 100 ms. Only after this holding time can the current flow and thus the welding process usually be started.

[0022] Advantageously, the lead time can be reduced, in particular to zero, with the welding device described herein, since the sheet thickness measurement or the determination of the actual path information described herein can be used as lead time, or rather, this lead time has already been "waited for." The execution of the sheet thickness measurement thus allows the lead time to be fully or partially compensated, and the sheet thickness measurement therefore does not lengthen or delay the process.

[0023] As described, a limit value can generally be defined, above which a measure is implemented in the welding process or in the operation of the welding equipment. The limit value can be defined, for example, as a band or range of values ​​around a target position of the actual position information, such as the target position information. Multiple limit values ​​can also be defined, above which different measures are implemented.

[0024] In one embodiment of the welding device, the welding device can be configured to compare the actual position information and / or a difference between the actual position information and the target position information with a warning limit and to rereference the welding device if the warning limit is exceeded. The term "exceeding" refers to leaving the value range or exceeding the warning limit, regardless of the direction in which such a limit is exceeded.

[0025] As a purely illustrative example, a warning threshold of 0.2 mm could be set for the difference between the actual and target displacement information. This means that if the actual displacement information exactly matches the target displacement information, the difference is zero. The warning threshold can therefore be set symmetrically or arbitrarily around this ideal case, so that the corresponding range of values ​​for the warning threshold can extend from -0.2 mm to +0.2 mm around the target displacement information. If the warning threshold is exceeded, i.e., deviated from above or below the target, the welding fixture can be rereferenced. To rereference, the previously described steps can be repeated, in particular determining the first displacement value at the first force value, determining the second displacement value at the second force value, and determining the force-displacement relationship, and the values ​​can be updated if necessary.

[0026] This makes it possible, in particular, to account for drift or changes during the operation of the welding fixture. For example, the welding gun elements may have caps that can wear out or shift, especially during operation of the welding fixture. After a certain number of welding processes, such caps on the welding gun elements may require mechanical machining, in particular milling or polishing. Since this results in material removal, it is advisable to rereference the welding fixture afterward. Similarly, after a further number of welding processes, the caps described may need to be replaced. Here, too, rereferencing is recommended.

[0027] In a further embodiment, the welding device can be configured to compare the actual position information and / or a difference between the actual position information and the target position information with an error limit. If the error limit is exceeded, an error routine is executed, in particular, the welding process is interrupted and an error message is issued. As already described with regard to the warning limit, the error limit can also be set arbitrarily. In particular, the error limit can also be set symmetrically or arbitrarily around a difference between the actual position information and the target position information of zero. The error limit is, in particular, greater than the warning limit.

[0028] For example, the error limit can be set to +0.3 mm to -0.3 mm around an actual path value that exactly matches the target path value. If the error limit is exceeded, the described error routine is executed. If the error limit is exceeded, it is assumed that an additional sheet metal element has been picked up or a sheet metal element is missing. In this case, the welding process is stopped or interrupted. Subsequently, it can be checked automatically or manually whether the correct number of sheet metal elements is present. A new referencing can then be performed, or the error can be corrected. This means that, depending on whether the error limit is exceeded, rework can also be triggered. The terms "error limit range" and "warning limit range" can be used instead of "error limit" and "warning limit range," respectively.

[0029] The welding device can be further developed such that, particularly for verification purposes, it can be configured to detect the welding current flowing through at least one welding gun element during a welding process. This welding current can also be used to verify whether the result of monitoring the actual path information with respect to the number of sheet metal elements is conclusive. The welding current flowing during the welding process also depends on the individual welding point. For example, if a sheet metal element is added, removed, or omitted, this affects the welding current, as it changes due to resistance. By additionally verifying the result described above, the inspection and monitoring of the welding device, especially regarding the number of sheet metal elements used, can be made even more robust and reliable.

[0030] Furthermore, the welding device may be designed, particularly for verification purposes, to check actual path information by means of a further welding process with a different welding gun on the same sheet metal element and / or the same welding gun on a different sheet metal element. The described configuration makes it possible, in particular, to introduce a change in the welding process with which the preceding welding process can be verified. For example, if a different weld point is performed on the same sheet metal joint with a different welding gun, and the welding gun produces the same result as the welding gun performing the preceding welding process, a fault in either of the two welding guns can be ruled out as far as possible. If the results differ, the welding guns can be checked or...A review can be triggered.

[0031] Alternatively or additionally, a welding gun can be used on a different sheet metal component to ensure that no defect goes undetected. In principle, any combination of welding processes with different welding guns on different combinations of sheet metal components is possible to generate the greatest possible variation between individual welding processes. This advantageously prevents errors in the acquisition of the actual path information from going undetected, or ensures that the acquisition of the actual path information can be verified by at least one other welding gun or at least one further combination of sheet metal components.

[0032] In addition to the described welding device, the invention relates to a control device for a welding device, in particular a previously described welding device, comprising a welding gun device, in particular a servo welding gun, which has a displacement detection device designed to detect position information, in particular a distance traveled, of at least one welding gun element of the welding gun device, and a force detection device designed to detect force information relating to a force acting on at least one welding gun element of the welding gun device, wherein the control device is designed toThe purpose is to determine a force-displacement relationship based on a first displacement value realized at a first force value and a second displacement value realized at a second force value, and to determine a target displacement value for a specific welding force in a welding process based on this force-displacement relationship. The control unit can be an integral part of a robotic device that performs the welding process, or of a welding gun device, or it can be designed as a separate control unit that is assigned to, or connectable to, the welding device.

[0033] Furthermore, the invention relates to a method for operating a welding device, in particular a welding device described above, comprising a welding gun device, in particular a servo welding gun, which has a displacement detection device designed to detect displacement information, in particular a distance traveled, of at least one welding gun element of the welding gun device and a force detection device designed to detect force information, which relates to a force acting on at least one welding gun element of the welding gun device, wherein a force-displacement relationship is determined based on a first displacement information realized at a first force value and a second displacement information realized at a second force value, and a target displacement information is determined for a specific welding force in a welding process based on the force-displacement relationship.The method can be carried out in all its details and with all its features on a welding apparatus described above, for example, by means of the control device described above. In other words, the welding apparatus and / or the control device described above is configured to carry out the method described herein.

[0034] All advantages, details, designs and / or features described in relation to the welding device are fully transferable to the control device and the process, and vice versa.

[0035] The invention is explained with reference to exemplary embodiments and the figures. The figures are schematic representations and show: Fig. 1 a schematic representation of a welding device according to an exemplary embodiment; Fig. 2. A schematic representation of a flowchart of a method for operating a welding device; and Fig. 3 A schematic representation of a diagram of path information according to an exemplary embodiment.

[0036] Fig. Figure 1 shows a schematic diagram of a welding device 1, which is designed in particular for joining sheet metal elements 2. Two sheet metal elements 2 are shown by way of example, but the number of sheet metal elements 2 can be changed as desired; for example, three or more sheet metal elements 2 can also be joined by welding. The welding device 1 comprises a welding gun assembly 3, which is designed, for example, as a servo welding gun. The welding gun assembly 3 has two welding gun elements 4, 5, which are movably arranged. For example, the welding gun assembly 3 has an adjustment device 6, for example, an adjustment cylinder, with which the welding gun elements 4, 5 can be moved, as indicated by arrow 7.

[0037] Specifically, a welding force can be applied to the sheet metal elements 2 by means of the welding tongs 4 and 5. Once the sheet metal elements 2 are pressed together by the welding tongs assembly 3, a welding current can flow between the caps 8 of the welding tongs 4 and 5, allowing the sheet metal elements 2 to be welded together at the specified welding point. The adjusting device 6, or more generally the welding tongs assembly 3, has a displacement detection device 9 and a force detection device 10, which can, for example, be integrated into or connected to the adjusting device 6. The welding tongs assembly 3 can have its own control device, or, as illustrated by way of example, a control device 11 of the welding device 1 can be used, or a control device 11 can be connected to or is connected to the welding device 1.The description can also be applied to an integrated control unit 11.

[0038] To monitor the welding process 1 and, in particular, to ensure that the correct number of sheet metal elements 2 are welded together, a force-displacement relationship can be determined. The execution of the procedure is also described below with regard to Fig. 2 explained.

[0039] To determine the force-displacement relationship, the welding gun assembly 3 in block 12 is first closed without the sheet metal elements 2. The welding gun elements 4 and 5 can then be moved relative to each other with a first force or force value. This can be controlled, for example, by the force detection device 10, or the force detection device 10 can record the force information to ensure that the first force value is reached. At this first force value 10, a first displacement value is determined in block 12, namely via the displacement detection device 9. The first force value can, in principle, be chosen arbitrarily, in particular below the minimum welding force used with the welding device 1 to weld the sheet metal elements 2. The first force value could, for example, be 1000 N.

[0040] Subsequently, a second force value can be realized in block 13 by closing the welding clamp elements 4 and 5 with a second closing force, as described previously. The second force value can be higher than the first, for example, corresponding to or exceeding the highest force value achievable with the welding device 1 or the actual welding force. In principle, the second force value can also be set independently of the welding forces applied in the welding process with the welding device 1. By way of example, the second force value could be 4000 N. The sequence of blocks 12 and 13 can also be reversed, for example, the second force value being realized before the first.

[0041] In block 13, the second position information is also determined when the second force value is realized. This position information can, for example, relate to the positions of the welding gun elements 4 and 5, a distance between the welding gun elements 4 and 5, or, more generally, other position information or a distance within the adjusting device 6.

[0042] In Block 14, the force-displacement relationship can then be determined. For example, a linear relationship can be established between the first displacement value at the first force value and the second displacement value at the second force value. Based on this, target displacement values ​​for specific welding forces during the operation of welding device 1 can be determined or calculated in Block 15. In Block 15, for example, the sheet thickness required for applying the welding forces, such as for performing a weld spot, can be taken into account, for instance, based on the number of sheet metal elements 2.

[0043] In block 16, during the execution of the welding points or the operation of the welding device 1, actual position information is recorded by means of the position detection device 9. The actual position information can be compared with the previously calculated or determined target position information; in particular, a difference can be calculated.

[0044] Optionally, the results can be verified in Block 17. For example, a different welding gun 3 (not shown) can be used to perform the same steps at a different welding point on the same sheet metal element 2, and the actual path information can be compared with the target path information for that welding point. Alternatively, the same welding gun 3 can be used at a different welding point in Block 17. Additionally or alternatively, the welding current at the specific welding point can be recorded and evaluated. Depending on the verification result, the welding gun 3 can be checked, or the result can be confirmed.

[0045] Based on the comparison between the actual path information and the target path information, the following steps can then be taken with regard to: Fig. As explained in section 3, a branch will occur from block 16 or 17 to block 18, 19, or 20. For this purpose, a warning limit 21 and an error limit 22 will be defined. The diagram in Fig. Figure 3, for example, shows the difference between the target path information and the actual path information. This difference is plotted on the vertical axis (ordinate). Individual comparisons or measurements are shown on the horizontal axis (abscissa). These individual measurements or results are purely illustrative and serve to explain the procedure.

[0046] An initial result 23 is shown as an example, which lies within the warning limit 21, for example, showing a difference of less than + / - 0.2 mm between the actual displacement information and the target displacement information. In this case, the process can branch from block 16 or 17 to block 18, where the operation of the welding device 1 can continue without further action.

[0047] The position measurement can drift during the operation of the welding device 1, for example, due to wear on the caps 8. This is illustrated in results 24 and 25. Result 24 is still within the warning limit 21, so block 16 and 17 can branch to block 18. Result 25 exceeds the warning limit 21, so the process branches from block 16 and 17 to block 19, where an action is performed. Action 21 can trigger a new referencing, meaning that the process starts again from block 12, and the first and second force values ​​are applied as described, and corresponding position information is determined. This allows the force-position relationship to be checked or updated. Subsequently, result 26 is again within the warning limit 21.

[0048] If errors occur in the welding process, for example, if a sheet metal element 2 is omitted and only two sheet metal elements 2 instead of three are gripped by the welding gun 3, this is illustrated by result 27. In this case, for example, with a sheet metal thickness of 0.7 mm, not only is the warning limit 21 of, for example, 0.2 mm in each direction exceeded, but the error limit 22, which is larger than the warning limit 21, is also exceeded. The error limit 22 can, for example, be 0.3 mm in both directions. If the error limit 22 is exceeded, the process branches from block 16, 17 to block 20, where the error routine can be executed. Accordingly, it can be determined that an error has occurred and the welding process of the welding device 1 can be stopped to identify the problem.

[0049] Result 28, for example, represents the case in which an additional sheet metal element 2 was caught. Therefore, the error limit 22 is exceeded, and the process can branch from block 16, 17 to block 20, where the welding process can also be stopped and the problem identified. Further measures, such as rework, can be triggered in block 20. Following such an error, a new referencing can then be initiated, as already described.

[0050] The welding device 1 is designed to perform the procedure described herein. The procedure can, for example, be carried out on the control device 11. This means that, with regard to Fig. 2, Fig. The 3 described methods can be carried out by means of the control device 1 or the control unit 11 and are therefore designed to carry out the method.

[0051] The advantages, details and features described in the exemplary embodiments can be combined, interchanged and transferred to one another as desired. REFERENCE MARK LIST 1 welding device 2 sheet metal elements 3 Welding tong device 4, 5 Welding tongs element 6 Adjustment device 7 Arrow 8 caps 9 Path recording device 10 Force detection device 11 Control unit 12-20 Block 21 Warning threshold 22 Error limit

Claims

[1] Welding device (1), in particular for joining sheet metal elements (2) for motor vehicles by welding, comprising a welding gun device (3), in particular a servo welding gun, which has a displacement detection device (9) designed to detect displacement information, in particular a displacement traveled, of at least one welding gun element (4, 5) of the welding gun device (3) and a force detection device (10) designed to detect force information relating to a force acting on at least one welding gun element (4, 5) of the welding gun device (3), characterized by, that the welding device (1) is designed to determine a force-displacement relation based on a first displacement information realized at a first force value and a second displacement information realized at a second force value, and to determine a target displacement information for a specific welding force in a welding process based on the force-displacement relation. [2] Welding device (1) according to claim 1, characterized by , that the target position information includes a specific total sheet thickness of the sheets arranged between the welding tongs elements (4, 5) in the welding process, wherein the welding device (1) is designed to compare actual position information acquired by means of the position detection device (9) for the welding process with the target position information determined for the welding process. [3] Welding device (1) according to claim 1 or 2, characterized by, that the welding device (1) is designed to determine different target path information for at least two different welding processes, in particular welding points. [4] Welding device (1) according to any one of the preceding claims, characterized by , that the welding device (1) is designed to acquire the actual displacement information and / or the force information in a specific time interval < 100ms. [5] Welding device (1) according to any one of the preceding claims, characterized by , that the welding device (1) is designed to compare the actual path information and / or a difference between actual path information and target path information with a warning limit (21) and to perform a referencing of the welding device (1) when the warning limit (21) is exceeded. [6] Welding device (1) according to one of the preceding claims, characterized by, that the welding device (1) is designed to compare the actual path information and / or a difference between actual path information and target path information with an error limit (22) and, if the error limit (22) is exceeded, to execute an error routine, in particular to interrupt the welding process and to issue an error message. [7] Welding device (1) according to one of the preceding claims, characterized by , that the welding device (1), in particular for verification, is designed to detect a welding current flowing over at least one welding tong element (4, 5) in a welding process. [8] Welding device (1) according to any one of the preceding claims, characterized by, that the welding device (1), in particular for verification, is designed to check actual path information by means of a further welding process of another welding gun device (3) on the same sheet metal element (2) and / or the same welding gun device (3) on another sheet metal element (2). [9] Control device (11) for a welding device (1), in particular a welding device (1) according to one of the preceding claims, comprising a welding gun device (3), in particular a servo welding gun, which has a displacement detection device (9) designed to detect displacement information, in particular a displacement traveled, of at least one welding gun element (4, 5) of the welding gun device (3) and a force detection device (10) designed to detect force information relating to a force acting on at least one welding gun element (4, 5) of the welding gun device (3), characterized by, that the control device is designed to determine a force-displacement relationship based on a first displacement information realized at a first force value and a second displacement information realized at a second force value, and to determine a target displacement information for a specific welding force in a welding process based on the force-displacement relationship. [10] Method for operating a welding device (1), in particular according to one of claims 1 to 8, comprising a welding gun device (3), in particular a servo welding gun, which has a displacement detection device (9) designed to detect displacement information, in particular a displacement traveled, of at least one welding gun element (4, 5) of the welding gun device (3) and a force detection device (10) designed to detect force information relating to a force acting on at least one welding gun element (4, 5) of the welding gun device (3), characterized by , that a force-displacement relation is determined based on a first displacement information realized at a first force value and a second displacement information realized at a second force value, and that a target displacement information is determined for a specific welding force in a welding process based on the force-displacement relation.

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