Method and computer device for monitoring and / or diagnosing welding clamp device

Abstract

The invention relates to a method for monitoring and / or diagnosing a welding plier device (1), the welding plier device (1) comprising a plier body (4) having two plier arms (6), each having a respective electrode (7), and a drive unit (5) having a drive (9) which can be brought into a drive movement, by means of which the plier arms (6) can be brought into a plier arm movement relative to one another, the method comprises the steps of determining a spring effect variable, i.e. A spring stiffness and / or spring work, of the caliper body (4) on the basis of the detected drive position, the detected drive unit force and / or the detected drive unit pressure, and determining the caliper body (4) on the basis of the determined spring effect variable, i.e. The spring stiffness and / or spring work. Diagnostic information relating to the electrode holder device (1) is provided and / or monitoring variables relating to the electrode holder device (1) are calculated.

Description

Technical Field

[0001] The present invention relates to a method for monitoring and / or diagnosing a welding tongs device, wherein the welding tongs device comprises a tongs body having two tongs arms and a drive unit having a drive element, wherein the tongs arms each have a corresponding electrode, the drive element can be placed in a drive element movement, and the tongs arms can be placed in a tongs arm movement relative to each other via the drive element. Background Art

[0002] The object of the present invention is to improve the monitoring and / or diagnosis of welding tongs devices. Summary of the invention

[0003] This object is achieved by a method according to claim 1. The method comprises the steps of determining a spring effect variable of the tongs body, i.e. a spring stiffness and / or a spring work, based on a detected drive element position, a detected drive unit force and / or a detected drive unit pressure and providing diagnostic information about the welding tongs device and / or calculating monitoring variables associated with the welding tongs device based on the determined spring effect variable.

[0004] The pliers body is elastically deformable and acts as a spring. The pliers body can be characterized in its properties as a spring by means of a spring effect variable, in particular the spring stiffness. The spring effect variable determines how the pliers body acts as a spring on the drive unit. The spring effect variable can be determined by means of a measurement variable, which is detected at or in the drive unit, i.e. by means of a drive element position, a drive unit force and / or a drive unit pressure. The spring effect variable depends on the state of the welding tongs device, in particular the pliers body, so that monitoring and / or diagnosis of the welding tongs device is possible based on the spring effect variable.

[0005] Advantageous developments are defined in the dependent claims.

[0006] The present invention further relates to a computer device for monitoring and / or diagnosing a welding tongs device, wherein the welding tongs device comprises a tongs body having two tongs arms and a drive unit having a drive element, the tongs arms each having a corresponding electrode, the drive element being placeable in a drive element movement, via which the tongs arms can be placed in a tongs arm movement relative to one another, wherein the computer device is constructed to determine spring effect parameters of the tongs body, in particular spring stiffness and / or spring work, based on a detected drive element position, a detected drive unit force and / or a detected drive unit pressure, and to provide diagnostic information about the welding tongs device and / or calculate monitoring parameters related to the welding tongs device based on the determined spring effect parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Further exemplary details and exemplary embodiments are explained below with reference to the figures. Figure 1A schematic diagram of a system including a welding tongs device, a cloud server and a user device is shown. DETAILED DESCRIPTION

[0008] Figure 1 An exemplary embodiment of a system 10 is shown, which comprises a welding tongs device 1 and optionally a cloud server 2 and / or a user device 3 .

[0009] The welding tongs device 1 comprises a tongs body 4 , which is in particular elastically deformable, and a drive unit 5 .

[0010] The pliers body 4 comprises two pliers arms 6, namely exemplarily a first pliers arm 6A and a second pliers arm 6B. Each pliers arm 6 has a corresponding electrode 7. Each pliers arm 6 preferably has a corresponding pliers arm body 8. Each electrode 7 is exemplarily arranged, in particular fastened, at a corresponding first end of a corresponding pliers arm body 8.

[0011] Exemplarily, the pliers body 4 has an X-shape. Alternatively, the pliers body may be embodied in a C-shape.

[0012] The drive unit 5 comprises a drive 9 which can be put into a drive movement. The drive unit 5 comprises a drive unit body 11 relative to which the drive 9 can be put into a drive movement. The welding tongs device 1 is preferably embodied as a servo-electric or servo-pneumatic device.

[0013] Exemplarily, the drive unit 5 is configured as a drive cylinder, in particular as a pneumatic drive cylinder. Exemplarily, the drive member 9 is a piston of the drive cylinder. The drive unit 5 can also be implemented as an electric drive unit, for example as an electric linear drive device, and in particular has an electric motor.

[0014] The welding tongs device 1 , exemplarily the drive unit 5 , expediently comprises a sensor device for detecting a drive position, a drive unit force and / or a drive unit pressure. The sensor device comprises, for example, a position sensor device 12 , a force sensor device 13 and / or a pressure sensor device 14 .

[0015] The drive member position describes the position of the drive member 9 relative to the drive unit body 11. The drive member position is expediently detected by means of a position sensor device 12. The position sensor device 12 may, for example, comprise a magnetic field sensor, for example as part of a path measurement system.

[0016] The drive unit force describes a force occurring in the drive unit 5, for example a force occurring between the drive unit body 11 and the drive member 9 and / or a force occurring between the drive unit 5 and the caliper body 4. The drive unit force is expediently a drive force, which the drive unit 5 applies to the caliper body 4, in particular in order to move the caliper arms 6 relative to one another (i.e. in particular to place them in a caliper arm movement) and / or to press them against one another. The drive unit force is expediently detected by means of a force sensor device 13 and / or calculated based on a drive unit pressure detected by means of a pressure sensor device 14.

[0017] The drive unit pressure describes the pressure assigned to the drive unit 5, for example the pressure of a pressure chamber of the drive unit 5 implemented as a drive cylinder, preferably the pressure difference between two pressure chambers of the drive unit 5. The drive unit pressure causes the drive member to move. The drive unit pressure is suitably detected by means of a pressure sensor arrangement 14. The pressure sensor arrangement 14 comprises one or more pressure sensors. For example, each pressure sensor is assigned to a corresponding pressure chamber.

[0018] The sensor devices, in particular the position sensor device 12 , the force sensor device 13 and / or the pressure sensor device 14 , can also be provided separately from the drive unit 5 .

[0019] If the drive unit 5 is designed as an electric drive unit, the position sensor device 12 and the force sensor device 13 are preferably present and the pressure sensor device 14 is preferably absent. If the drive unit 5 is designed as a drive cylinder, the position sensor device 12 and the pressure sensor device 14 are preferably present and the force sensor device 13 is preferably absent.

[0020] Exemplarily, each pliers arm 6 has a corresponding force transmission position 15, at which the drive unit 5 introduces the driving force into the pliers body 4. Each electrode 7 is exemplarily arranged at a corresponding second end of a corresponding pliers arm body 8. Exemplarily, the drive unit body 11 is coupled to the force transmission position 15 of the first pliers arm 6a, in particular fastened to the force transmission position, and / or the drive member 9 is coupled to the force transmission position 15 of the second pliers arm 6b, in particular fastened to the force transmission position.

[0021] The tongs arms 6 can be placed in a tongs arm movement relative to one another by means of the drive 9, in particular by means of a drive movement. During the movement of the tongs arms, the electrodes 7 are moved relative to one another. Exemplarily, the welding tongs device 1 comprises a bearing 16, in particular in the form of a pivot bearing, by means of which the tongs arms 6, in particular the tongs arm body 8, are mounted so that they can move relative to one another, in an exemplary manner so that they can pivot relative to one another.

[0022] For example, the arms 6 can be placed in a first arm movement 18 relative to each other by means of a first drive movement 17. Suitably, during the first drive movement 17, the drive element 9 is moved away from the drive unit body 11, in particular extended from said drive unit body. Preferably, the electrodes 7 are moved towards each other during the first arm movement 18. Exemplarily, the first drive movement 17 is a linear movement and / or the first arm movement 18 is a rotational movement, in particular around the bearing 16.

[0023] For example, the arms 6 can be placed in a second clamp arm movement relative to each other by a second drive member movement. During the second drive member movement, the drive member 9 is suitably moved towards the drive unit body 11, in particular retracted into the drive unit body. Preferably, the electrodes 7 are moved away from each other during the second clamp arm movement. The second drive member movement is opposite to the first drive member movement 17. The second clamp arm movement is opposite to the first clamp arm movement 18.

[0024] The welding tongs device 1 can be placed in a contact position (Anlagestellung), which can also be referred to as a closed position, by means of a first drive movement (and the resulting first tongs arm movement). In the contact position, the electrodes 7 are suitably in contact with each other or with a contact object (Anlageobjekt), for example a sheet metal counterpart (Blechpaarung). In the contact position, a further first tongs arm movement 18 is not possible. In particular, due to the electrodes being in contact with each other (Anlage) or with the contact object, in the first contact position, the tongs arms 6 cannot be moved further relative to each other in the direction of the first tongs arm movement 18. In particular, the tongs body 4 cannot be closed further in the contact position.

[0025] In particular, in the contact position, the pliers body 4, in particular the two pliers arms 6, act as a spring, in particular for the drive unit 5 and / or between the two force transmission points 15. In particular, in the contact position, the first drive movement 17, i.e., the extension of the drive element 9, for example, leads to an elastic deformation of the pliers body 4, in particular the pliers arms 6, and in particular to no movement of the electrodes 7 relative to one another. Figure 1 The state in which the caliper body 4 is elastically deformed due to the position of the drive member 9 relative to the drive unit body 11, in particular due to the first drive member movement 17, should also be referred to as a deformed state.

[0026] Due to the elastic deformation, the caliper body 4 in the deformed state exerts a spring force on the drive unit 5, in particular on the drive member 9. The spring force resists the first drive member movement 17, in particular in the opposite direction to the first drive member movement 17. The spring force is suitably proportional to the position of the drive member 9 relative to the drive unit body 11. The further the drive member 9 is moved relative to the drive unit body 11 in the direction of the first drive member movement 17, the greater the spring force becomes.

[0027] The welding tongs device 1, in particular the tongs body 4, comprises, by way of example, two electrical connections 19, between which a voltage source or a current source can be connected in order to cause a current to flow through the electrode 7 (in particular when the electrode 7 is in contact with an object to be welded, such as a sheet metal counterpart). By way of example, a corresponding electrical connection 19 is present at each tongs arm 6.

[0028] The welding tongs device 1 expediently comprises a control device 20, which is used in particular to control the drive unit 5. The control device 20 expediently comprises a computer unit 21, for example a microprocessor. Optionally, the control device 20 comprises a valve device 22 in order to supply compressed air to the drive unit 5 (when the drive unit 5 is embodied as a pneumatic drive unit). The valve device 22 can expediently supply compressed air to the drive unit 5 and / or exhaust the drive unit 5.

[0029] By way of example, the cloud server 2 is communicatively connected to the welding tongs device 1 , in particular to the control device 20 .

[0030] The user device 3 is preferably implemented as a mobile device, for example, a mobile phone or a tablet computer. In addition, the user device 3 can be implemented as a computer, for example, a desktop computer or a laptop computer. The user device 3 is exemplarily communicatively connected to the welding tongs device 1, in particular the control device 20 and / or to the cloud server 2.

[0031] How the welding tongs device 1 can be monitored and / or diagnosed will be discussed in more detail below. The monitoring and / or diagnosis is performed in particular by a computer device 23. In particular, all calculations or determinations explained below are performed by the computer device 23. The computer device 23 is preferably part of the system 10. The computer device 23 is in particular formed by the control device 20 and / or the cloud server 2 and / or by the user device 3. For example, the computer device 23 is the control device 20, the cloud server 2 or the user device 3.

[0032] The monitoring and / or diagnosis of the welding clamp device 1 is carried out in particular by the following steps, which are preferably executed by the computer device 23: determining the spring effect parameters of the clamp body 4, i.e. the spring stiffness and / or the spring work, based on the detected drive member position, the detected drive unit force and / or the detected drive unit pressure, and providing diagnostic information about the welding clamp device 1 and / or calculating monitoring parameters related to the welding clamp device 1 based on the determined spring effect parameters.

[0033] As already mentioned above, each caliper arm 6 expediently has a corresponding force transmission point 15 for introducing the drive force provided by the drive unit 5. The spring effect parameter expediently relates to the elastic deformability of the caliper body 4 that is given between the force transmission points 15. Thus, the spring effect parameter relates in particular to the spring effect experienced by the drive unit 5 (in particular in the contact position of the caliper body 4) between two force transmission points 15. In particular, the spring effect parameter is the spring stiffness of the caliper body 4 (in particular in the contact position) acting as a spring on the drive unit 5.

[0034] Optionally, a force accumulation spring stiffness and / or a force reduction spring stiffness is determined as the spring effect parameter. The force accumulation spring stiffness is that spring stiffness of the caliper body 4 which is present when the driving force applied by the drive unit 5 to the caliper body 4 is increased, in particular in the contact position. The force reduction spring stiffness is that spring stiffness of the caliper body 4 which is present when the driving force applied by the drive unit 5 to the caliper body 4 is reduced, in particular in the contact position. Preferably, diagnostic information and / or monitoring parameters are provided based on the force accumulation spring stiffness and / or based on the force reduction spring stiffness.

[0035] During force accumulation, there is preferably a substantially linear relationship between the force increase at the drive unit 5 (eg the drive force and / or the detected drive unit force) and the bending or deformation of the caliper body 4 (which corresponds in particular to the drive position).

[0036] This linear relationship can be described by the following equation (1):

[0037] F ZylUp =C Up ·dx+F RefUp (1)

[0038] F ZylUp is the driving unit force or driving force. C Up is the spring rate of the caliper body during force accumulation, ie the force accumulation spring rate. dx is the position difference of the drive member 9 (which occurs with a corresponding elastic deformation of the caliper body 4) and is determined based on the detected drive member position. F RefUp is the force at the reference position of the drive member and should also be referred to as the reference force; for example, F RefUp It is the starting force when the force accumulates.

[0039] Due to the friction forces effective in the drive unit 5 and / or the caliper body 4, hysteresis characteristics may occur (especially in the contact position) with respect to the force path diagram, i.e. with respect to the ratio or dependency between the drive unit force and the drive element position. In particular, the spring rate of the caliper body 4 during force dissipation, i.e. the force dissipation spring rate, may be lower than the force accumulation spring rate.

[0040] In particular, the following equation (2) applies to the force reduction:

[0041] F ZylDw =C Dw ·dx+F RefDw (2)

[0042] F ZylDw is the driving unit force or driving force. C Dw is the spring rate of the caliper body during force reduction, ie the force reduction spring rate. dx is the position difference of the drive element 9 (which occurs with a corresponding elastic deformation of the caliper body 4) and is determined based on the detected drive element position. F RefDw is the force at the reference position of the drive member and should also be referred to as the reference force; for example, F RefDw It is the stopping force or unloading force when the force is reduced.

[0043] Determining both the force accumulation spring rate and the force reduction spring rate enables a more precise monitoring of the spring rate of the caliper body 4. Preferably, the hysteresis characteristic of the force path diagram is detected and used, for example, to calculate the friction during force accumulation.

[0044] In the following, it will be discussed in more detail how the spring effect variable, in particular the spring stiffness, can be determined.

[0045] In order to determine the spring effect parameter, a deformation procedure is preferably performed, in which the elastic deformation of the caliper body 4 is changed by means of the drive unit 5, and during the change of the elastic deformation, the drive member position, the drive unit pressure and / or the drive unit force are detected. The execution of the deformation procedure is controlled, for example, by a computer device 23, in particular the control device 20. The deformation procedure suitably comprises a force accumulation procedure and / or a force reduction procedure. In the case of the force accumulation procedure, the drive unit force and / or the driving force are increased by means of the drive unit 5, for example by means of the first drive member movement 17 (especially in the contact position and / or in the deformed state). In the case of the force accumulation procedure, the elastic deformation of the caliper body 4 is suitably increased. In the case of the force reduction procedure, the drive unit force and / or the driving force are reduced by means of the drive unit 5, for example by means of the second drive member movement (especially in the contact position and / or in the deformed state). In the case of the force reduction procedure, the elastic deformation of the caliper body 4 is suitably reduced.

[0046] Preferably, during the deformation procedure, in particular during the force accumulation procedure and / or during the force reduction procedure, the corresponding time course of the drive member position and / or the drive unit force and / or the drive unit pressure is recorded, in particular by the computer device 23. The spring effect parameter is suitably determined based on one or more of the recorded time courses. For example, the spring effect parameter is determined based on the time course of the drive member position and the time course of the drive unit force. In addition, the spring effect parameter can be determined based on the time course of the drive member position and the time course of the drive unit pressure.

[0047] The spring rate is preferably calculated by means of linear regression based on the time course of the drive element position and the time course of the drive unit force (preferably detected by the force sensor device 13 or calculated based on the time course of the drive unit pressure). For example, the spring rate is calculated, in particular, by the computer device 23 according to the following equation (3):

[0048]

[0049] C zk is the spring stiffness. is the standard deviation of the drive unit force (especially the time variation of the drive unit force). dx is the standard deviation of the drive element position (in particular the time course of the drive element position), in particular the difference between the drive element position and a starting position or reference position of the drive element 9 (in particular given at the beginning of a deformation program). It is the correlation between the drive unit force (especially its time course) and the drive element position (especially its time course), especially the difference between the drive element position and a starting position or reference position.

[0050] In conjunction with the calculation of the spring stiffness (or other parameters), the term "drive member position" refers in particular to one or more values ​​of the time variation of the drive member position and / or the term "drive unit force" refers to one or more values ​​of the time variation of the drive unit force.

[0051] Optionally, the reference force F is calculated by linear regression based on the time course of the drive element position and the time course of the drive unit force. Ref (The reference force, for example, represents the reference force F RefUp or F RefDw ) (preferably detected by the force sensor device 13 or calculated based on the time course of the drive unit pressure). For example, the reference force is calculated by the computer device 23 according to the following equation (4):

[0052]

[0053] About parameters s dx and See explanation above. is the average value of the drive unit force. It is the average value of the drive element position, in particular the difference between the drive element position and the starting position or reference position.

[0054] Alternatively, the spring stiffness C can be calculated using a linear function with two data points, such as equation (1) or (2) zk and / or reference force F Ref The pair consisting of a value of the drive element position and an assigned value of the drive unit force (i.e. the value of the drive unit force at which the value of the drive element position is detected) is referred to as a data point. In particular, the drive element position and the drive unit force are expediently detected at two different positions of the drive element 9 while the caliper body 4 is in the contact position and / or in the deformed state. For example, based on equation (1) or (2), a system of equations with two unknowns is established and solved according to the spring stiffness and / or the reference force.

[0055] The calculation of the monitoring variable will be discussed in more detail below. Optionally, a plurality of monitoring variables are calculated based on the spring effect variable, in particular on the spring stiffness. In particular, one or more monitoring variables are calculated by the computer unit 23 .

[0056] For example, electrode forces and / or drive unit force estimation variables and / or spring work are calculated as monitoring variables.

[0057] The electrode force is in particular the force acting on one or both electrodes 7 in the contact position. For example, the electrode force is the force that the electrodes 7 exert on one another in the contact position and / or the force that the electrodes 7 exert on a contact object, such as a sheet metal counterpart, in the contact position. In the operation of the system 10, there is preferably no sensor with which the electrode force can be directly measured.

[0058] The electrode force is preferably calculated based on the spring stiffness and a reference spring stiffness. The reference spring stiffness is a spring stiffness that is calculated (especially before putting the system 10 into operation) based on the forces measured directly at one or both electrodes 7 using external force sensors.

[0059] Optionally, the electrode force can be determined based on the force path curve with respect to a reference force path curve. The force path curve describes the relationship between the drive unit force detected (especially in the case of a deformation program) and the drive member position. The reference force path curve is suitably determined using an external force sensor and / or preferably describes the relationship between the force (at one or both electrodes 7) detected using an external force sensor and the drive member position.

[0060] For example, the electrode force F is calculated by the computer device 23 according to the following equation (5): Elc :

[0061]

[0062] C SenUp is the spring stiffness detected by means of an external force sensor. C ZkUp is the spring rate explained above. Zyl is the driving unit force. F RefZkUp is the reference force. RefsenUp It is the reference force detected by an external sensor.

[0063] Optionally, a friction variable is calculated, which describes the friction of the drive unit 5 and / or the friction of the caliper body 4 . In particular, the friction variable is composed of the friction of the drive unit 5 and the friction of the caliper body 4 .

[0064] Preferably, the friction parameter is calculated based on the drive unit force, for example based on the difference between the value of the drive unit force detected during force accumulation (for example in the case of a force accumulation procedure) and the value of the drive unit force detected during force reduction (for example in the case of a force reduction procedure), especially in the case of the same drive member position and preferably using a computer device 23.

[0065] For example, the friction parameter F is calculated according to the following equation (6): R :

[0066]

[0067] F RefUp is the value of the drive unit force detected during force buildup, for example the starting force during force buildup. RefDw It is the value of the drive unit force detected when the force is reduced, for example, the unloading force during force accumulation.

[0068] Furthermore, the friction variable can be calculated as a displacement of a force path curve between force build-up and force dissipation. The force path curve describes the relationship between the drive unit force and the position of the drive element.

[0069] Optionally, an average spring rate is calculated, in particular by the computer device 23. Average spring rate C zk In particular, it is calculated according to the following equation (7):

[0070]

[0071] C Up is the force accumulation spring rate explained above. C Dwis the force reduction spring rate explained above. Based on the average spring rate C zk The diagnostic information is expediently determined. For example, in response to a certain change in the average spring rate, wear is inferred and corresponding diagnostic information is generated, in particular by the computer device 23, which indicates this wear.

[0072] The drive unit force estimation variable represents an estimate of the drive unit force and is preferably calculated with the aid of equation (1) or (2) (as F ZylUp or F ZylDw ). The drive unit force estimation variable can then be compared with the drive unit force detected by means of the force sensor device 13 (or the pressure sensor device 14). As long as the deviation between the drive unit force estimation variable and the drive unit force exceeds a predetermined threshold value, a defect of the force sensor device 13 (or the pressure sensor device) can be inferred and, in particular, corresponding diagnostic information can be generated by the computer device 23, which indicates this defect.

[0073] Optionally, the spring work is calculated, in particular by the computer unit 23. Preferably, the spring work W is calculated based on the drive unit force and the drive member position, in particular according to the following equation (8): Zk :

[0074]

[0075] dF Zk is the change in the drive unit force, and dx is the change in the drive element position. The spring work is preferably calculated based on two or more values ​​of the drive element position and the drive unit force, respectively, which are detected during the deformation routine, in particular during the force accumulation routine and / or during the force reduction routine. Diagnostic information is expediently determined based on the spring work. For example, the computer device 23 checks whether the change in the spring work exceeds a predetermined threshold value. If this is the case, the computer device 23 provides corresponding diagnostic information, which indicates, for example, that the bearing 16 is loose or that there is increased system friction.

[0076] The diagnostic information will be discussed in more detail below. The diagnostic information is preferably determined by the computer device 23 .

[0077] The diagnostic information preferably relates to electrode force monitoring and / or tong arm fracture detection and / or cover contact pressure errors and / or welding tongs bearing errors and / or verification and / or calibration errors of drive unit measurement variables.

[0078] The computer device 23 is preferably configured to perform electrode force monitoring based on spring stiffness. For example, the computer device 23 is configured to perform electrode force monitoring based on (especially as explained above) calculated electrode force. In particular, it is checked whether the electrode force changes over time during electrode force monitoring. For example, the electrode force and / or the change of the electrode force is compared with one or more limit values ​​for this purpose. Preferably, in particular based on the calculated electrode force and / or the mentioned comparison, the computer device 23 provides diagnostic information, which indicates whether there is an inadmissible deviation of the electrode force. For the purpose of electrode force monitoring, the computer device 23 suitably calculates the electrode force repeatedly, for example periodically. For example, the computer device repeatedly initiates deformation procedures and calculates the change of the current electrode force and / or the calculated electrode force relative to the previously calculated electrode force during each deformation procedure. Exemplarily, the computer device 23 has, in particular, user-definable limit values ​​for evaluating whether there is an inadmissible deviation of the electrode force, and uses these limit values ​​for generating diagnostic information.

[0079] Preferably, the computer device 23 performs a pliers arm fracture detection based on a spring effect parameter, in particular a spring stiffness and / or a spring work, in order to detect a fracture of the pliers arm 6. For example, the monitored pliers arm 6 is arc-shaped, and the pliers arm fracture detection can also be referred to as arc fracture detection. The computer device 23 expediently checks (in particular during force accumulation and / or force reduction) whether there is a reduction in the spring stiffness, and / or monitors the spring work, and based on this checking and / or monitoring provides diagnostic information, which expediently indicates the presence of a pliers arm fracture.

[0080] The computer device 23 preferably checks whether a cover pressing error exists based on the spring stiffness. In the case of a cover pressing error, one or both electrodes 7 are not pressed sufficiently onto the corresponding clamp arm body 8. The computer device 23 expediently checks whether there is a reduction in the spring stiffness during force accumulation (in particular relative to a reference spring stiffness determined previously, for example) and / or whether there is no change in the spring stiffness during force reduction (in particular relative to a reference spring stiffness determined previously, for example), and based on this check provides diagnostic information, which expediently indicates the presence of a cover pressing error.

[0081] The computer device 23 preferably checks whether a welding gun bearing error is present, in particular based on the spring stiffness and / or the friction parameter. A welding gun bearing error comprises, for example, a loose bearing error, in which the bearing 16 is loose, and / or an increased friction error, in which an increased friction is present at the bearing. The computer device 23 is particularly designed to detect a loose bearing error based on a reduction in spring stiffness, in particular during force build-up and / or force reduction, and / or a reduction in friction, in particular during force build-up and / or force reduction, and / or a reduction in average friction, in particular a friction parameter. The computer device 23 is designed to provide diagnostic information in response to the detection of a loose bearing error, the diagnostic information indicating a loose bearing error. The computer device 23 is particularly designed to detect an increased friction error based on the presence of increased friction, in particular an increased friction parameter and / or an increased average stiffness. The computer device 23 is designed to provide diagnostic information in response to the detection of an increased friction error, the diagnostic information indicating an increased friction error.

[0082] The computer device 23 is preferably designed to perform a verification of the drive unit measured variables. The measured variables detected by means of the sensor device, in particular the drive unit force, the drive unit pressure and / or the drive unit position, shall be referred to as drive unit measured variables. For example, the computer device 23 performs a plausibility check on the drive unit force measured by means of the sensor device based on the force calculated from the bending of the caliper body 4 (for example according to equation (1) or (2)) and provides diagnostic information based on the plausibility check, which preferably indicates the result of the plausibility check.

[0083] The computer device 23 is preferably designed to detect calibration errors of the welding tongs device 1. In the case of a calibration error, for example, the cover is not pressed tightly and / or the sensor values ​​detected by the sensor device are not plausible. The computer device 23 is designed to check the plausibility of the force path diagram of the force sensor device 13 and to provide corresponding diagnostic information based on the check.

[0084] In particular, the corresponding spring effect parameters, in particular the corresponding spring stiffness, are preferably determined for a plurality of welding tongs devices by means of the computer device 23. The spring stiffness is preferably stored in a database and / or the welding tongs devices are grouped or separated by their spring stiffness, in particular by means of the computer device 23, for example when calling up data from the database. In particular, an abnormality detection is preferably performed by means of the computer device 23 based on the spring stiffness in order to identify abnormal welding tongs devices 1. For example, the computer device 23 detects that the spring stiffness of a welding tongs device is significantly different from the spring stiffness of other welding tongs devices of the same structure, identifies the welding tongs device as abnormal and appropriately outputs corresponding diagnostic information.

[0085] The welding tongs device 1 is used, for example, in a resistance pressure welding method for welding sheet metal parts. In particular, the welding tongs device 1 enables force transmission and current transmission to a sheet metal counterpart. For example, in the production of a car body, the welding tongs device is transported in space by an industrial robot and positioned toward a welding object.

[0086] Optionally, a diagnostic tool is provided, which is executed, in particular, on the computer device 23 and preferably uses one or more of the spring stiffness and the monitoring variable for diagnosing the welding tongs device 1. The spring stiffness and / or the monitoring variable are detected and evaluated, for example, on the control device 20 and / or transmitted to the cloud server 2 and evaluated there.

[0087] The calculations required for determining the spring effect variable, the monitoring variable and / or the diagnostic information are preferably performed with the aid of linearization, an observer or machine learning, for example on the control device 20 and / or on the cloud server 2. Optionally, the spring effect variable, the monitoring variable and / or the diagnostic information are transmitted to the user device 3 and displayed there, for example visually, for example on a graphic display.

Claims

1. A method for monitoring and / or diagnosing a welding tongs device (1), wherein the welding tongs device (1) comprises a tongs body (4) having two tongs arms (6) and a drive unit (5) having a drive element (9), the tongs arms each having a corresponding electrode (7), the drive element being capable of being placed in a drive element movement, by means of which the tongs arms (6) can be placed in a tongs arm movement relative to one another, the method comprising the steps of determining a spring effect parameter of the tongs body (4), i.e. a spring stiffness and / or a spring work, based on a detected drive element position, a detected drive unit force and / or a detected drive unit pressure, and providing diagnostic information about the welding tongs device (1) and / or calculating a monitoring parameter related to the welding tongs device (1) based on the determined spring effect parameter.

2. A method according to claim 1, wherein each pliers arm (6) has a corresponding force transmission position (15) for introducing the driving force provided by the drive unit (5), and the spring effect parameter relates to the elastic deformability of the pliers body (4) between the force transmission positions (15).

3. The method according to claim 1 or 2, wherein a deformation procedure is performed, wherein the elastic deformation of the caliper body (4) is changed by means of the drive unit (5), and the drive member position, drive unit pressure and / or drive unit force are detected during the change of the elastic deformation. 4 . The method according to claim 1 , wherein an electrode force, a drive unit force estimation variable and / or a spring work / the spring work is calculated as the monitoring variable.

5. The method according to any of the preceding claims, wherein the diagnostic information relates to electrode force monitoring, tong arm fracture detection, cover clamping errors, welding tongs bearing errors, verification of drive unit measurement variables and / or calibration errors. 6 . The method according to claim 1 , wherein corresponding spring effect variables, in particular corresponding spring stiffnesses, are determined for a plurality of welding tongs devices. 7 . The method according to claim 6 , wherein the spring stiffness is stored in a database and the welding clamp devices are grouped or separated by their spring stiffness.

8. The method according to claim 6 or 7, wherein anomaly detection is performed based on the spring stiffness in order to identify an abnormal welding clamp device.

9. A computer device (23) for monitoring and / or diagnosing a welding tongs device (1), wherein the welding tongs device (1) comprises a tongs body (4) having two tongs arms (6) and a drive unit (5) having a drive member (9), wherein the tongs arms respectively have corresponding electrodes (7), and the drive member can be placed in a drive member movement, through which the tongs arms (6) can be placed in a tongs arm movement relative to each other, wherein the computer device (23) is constructed to determine the spring effect parameters of the tongs body (4), that is, the spring stiffness and / or the spring work, based on the detected drive member position, the detected drive unit force and / or the detected drive unit pressure, and based on the determined spring effect parameters, provide diagnostic information about the welding tongs device (1) and / or calculate monitoring parameters related to the welding tongs device (1).

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