Method for monitoring and / or diagnosing a welding gun device and computer system

Abstract

The invention relates to a method for monitoring and / or diagnosing a welding gun device (1), wherein the welding gun device (1) comprises a gun body (4) with two gun arms (6) each having an electrode (7) and a drive unit (5) with a drive element (9) that can be moved into a drive element movement, by which the gun arms (6) can be moved relative to each other in a gun arm movement, comprising the steps of: determining a spring effect quantity, namely a spring stiffness and / or a spring work, of the gun body (4) based on a detected drive element position, a detected drive unit force and / or a detected drive unit pressure, and, based on the determined spring effect quantity, providing diagnostic information about the welding gun device (1) and / or calculating a monitoring quantity related to the welding gun device (1).

Description

[0001] The invention relates to a method for monitoring and / or diagnosing a welding gun device, wherein the welding gun device comprises a gun body with two gun arms, each having a respective electrode, and a drive unit with a drive member that can be set into a drive member movement, by means of which the gun arms can be set into a gun arm movement relative to one another.

[0002] An object of the invention is to improve monitoring and / or diagnosis of the welding gun device.

[0003] The problem is solved by a method according to claim 1.

[0004] The method comprises the steps of: determining a spring effect variable, namely a spring stiffness and / or a spring work, of the gun body based on a detected drive member position, a detected drive unit force and / or a detected drive unit pressure, and, based on the determined spring effect variable, providing diagnostic information about the welding gun device and / or calculating a monitoring variable related to the welding gun device.

[0005] The gun body is elastically deformable and acts as a spring. The gun body's spring-like properties can be characterized by the spring effect parameter, particularly the spring stiffness. The spring effect parameter determines how the gun body acts as a spring on the drive unit. The spring effect parameter can be determined by measured variables recorded on or in the drive unit, namely the drive link position, the drive unit force, and / or the drive unit pressure. The spring effect parameter depends on the condition of the welding gun device, particularly the gun body, so that monitoring and / or diagnosis of the welding gun device is possible based on the spring effect parameter.

[0006] Advantageous further training is defined in the dependent claims.

[0007] The invention further relates to a computer device for monitoring and / or diagnosing a welding tong device, wherein the welding tong device comprises a tong body with two tong arms, each having a respective electrode, and a drive unit with a drive member that can be set into a drive member movement, by means of which the tong arms can be set into a tong arm movement relative to one another, wherein the computer device is designed to determine a spring effect variable, in particular a spring stiffness and / or a spring work, of the tong body on the basis of a detected drive member position, a detected drive unit force and / or a detected drive unit pressure, and, on the basis of the determined spring effect variable, to provide diagnostic information about the welding tong device and / or to calculate a monitoring variable related to the welding tong device.

[0008] Further exemplary details and exemplary embodiments are explained below with reference to the figure. Fig. 1 a schematic representation of a system with a welding gun device, a cloud server and a user device.

[0009] The Fig. 1 shows an exemplary embodiment of a system 10 comprising a welding gun device 1 and optionally a cloud server 2 and / or a user device 3.

[0010] The welding tong device 1 comprises a particularly elastically deformable tong body 4 and a drive unit 5.

[0011] The forceps body 4 comprises two forceps arms 6, for example a first forceps arm 6A and a second forceps arm 6B. Each forceps arm 6 has a respective electrode 7. Preferably, each forceps arm 6 has a respective forceps arm body 8. Each electrode 7 is arranged, in particular fastened, for example at a respective first end of the respective forceps arm body 8.

[0012] By way of example, the pliers body 4 has an X-shape. Alternatively, the pliers body can be designed in a C-shape.

[0013] The drive unit 5 comprises a drive member 9 that can be set into a drive member movement. The drive unit 5 comprises a drive unit body 11, relative to which the drive member 9 can be set into the drive member movement. The welding gun device 1 is preferably designed to be servo-electric or servo-pneumatic.

[0014] By way of example, the drive unit 5 is designed as a drive cylinder, in particular as a pneumatic drive cylinder. By way of example, the drive element 9 is a piston of the drive cylinder. The drive unit 5 can also be designed as an electric drive unit, for example as an electric linear drive, and in particular have an electric motor.

[0015] The welding gun device 1, for example the drive unit 5, expediently comprises a sensor arrangement for detecting a drive member position, a drive unit force, and / or a drive unit pressure. The sensor arrangement comprises, for example, a position sensor device 12, a force sensor device 13, and / or a pressure sensor device 14.

[0016] The drive member position describes a position of the drive member 9 relative to the drive unit body 11. The drive member position is expediently detected by the position sensor device 12. The position sensor device 12 can, for example, comprise a magnetic field sensor, for example as part of a position measuring system.

[0017] 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 pliers body 4. The drive unit force is expediently a drive force that the drive unit 5 applies to the pliers body 4, in particular to move the pliers arms 6 relative to one another (i.e., in particular, to set the pliers arm movement) and / or to press them against one another. The drive unit force is expediently detected by the force sensor device 13 and / or calculated based on the drive unit pressure detected by the pressure sensor device 14.

[0018] The drive unit pressure describes a pressure associated with the drive unit 5, for example, a pressure of a pressure chamber of the drive unit 5 (configured as a drive cylinder), preferably a differential pressure between two pressure chambers of the drive unit 5. The drive unit pressure causes the drive element movement. The drive unit pressure is expediently detected by the pressure sensor device 14. The pressure sensor device 14 comprises one or two pressure sensors. For example, each pressure sensor is associated with a respective pressure chamber.

[0019] The sensor arrangement, 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.

[0020] 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 not present. 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 not present.

[0021] By way of example, each tong arm 6 has a respective force introduction point 15 at which the drive unit 5 introduces the drive force into the tong body 4. Each electrode 7 is arranged, by way of example, at a respective second end of the respective tong arm body 8. By way of example, the drive unit body 11 is coupled to a force introduction point 15 of the first tong arm 6a, in particular fastened thereto, and / or the drive member 9 is coupled to a force introduction point 15 of the second tong arm 6b, in particular fastened thereto.

[0022] By means of the drive member 9, in particular by the drive member movement, the gun arms 6 can be set into a gun arm movement relative to one another. During the gun arm movement, the electrodes 7 are moved relative to one another. For example, the welding gun device 1 comprises a bearing 16, designed in particular as a pivot bearing, via which the gun arms 6, in particular the gun arm bodies 8, are mounted so that they can move relative to one another, for example pivot relative to one another.

[0023] For example, the tong arms 6 can be displaced relative to one another by a first drive member movement 17 in a first tong arm movement 18. During the first drive member movement 17, the drive member 9 is expediently moved away from the drive unit body 11, in particular extended therefrom. Preferably, the electrodes 7 are moved toward one another during the first tong arm movement 18. For example, the first drive member movement 17 is a linear movement and / or the first tong arm movement 18 is a pivoting movement, in particular around the bearing 16.

[0024] For example, the tong arms 6 can be moved relative to one another by a second drive member movement. During the second drive member movement, the drive member 9 is expediently moved toward the drive unit body 11, in particular retracted into it. Preferably, the electrodes 7 are moved away from one another during the second tong arm movement. The second drive member movement is opposite to the first drive member movement 17. The second tong arm movement is opposite to the first tong arm movement 18.

[0025] The welding gun device 1 can be moved into a contact position, which can also be referred to as a closed position, by the first drive member movement (and the resulting first gun arm movement). In the contact position, the electrodes 7 expediently contact one another or contact a contact object, for example a pair of sheets. In the contact position, no further first gun arm movement 18 is possible. In the first contact position, the gun arms 6 cannot be moved further in the direction of the first gun arm movement 18 relative to one another, in particular due to the contact of the electrodes against one another or against the contact object. In particular, the gun body 4 cannot be closed any further in the contact position.

[0026] Particularly in the contact position, the forceps body 4, in particular the two forceps arms 6, acts as a spring, in particular on the drive unit 5 and / or between the two force introduction points 15. Particularly in the contact position, the first drive element movement 17 - thus, for example, an extension of the drive element 9 - leads to an elastic deformation of the forceps body 4, in particular the forceps arms 6, and in particular to no movement of the electrodes 7 relative to each other. Fig. In Figure 1, the elastic deformation is indicated by dashed lines. The state in which the pliers body 4 is elastically deformed due to a position of the drive member 9 relative to the drive unit body 11, in particular due to the first drive member movement 17, shall also be referred to as the deformation state.

[0027] Due to the elastic deformation, the pliers body 4, in the deformed state, exerts a spring force on the drive unit 5, in particular the drive member 9. The spring force counteracts the first drive member movement 17, in particular counter to the direction of the first drive member movement 17. The spring force is expediently proportional to the position of the drive member 9 relative to the drive unit body 11. The further the drive member 9 is moved in the direction of the first drive member movement 17 relative to the drive unit body 11, the greater the spring force becomes.

[0028] The welding gun device 1, in particular the gun body 4, comprises, by way of example, two electrical connections 19, between which a voltage source or a current source can be connected to cause an electric current to flow through the electrodes 7 (in particular in a state in which the electrodes 7 are in contact with an object to be welded, for example, a sheet metal pair). By way of example, a respective electrical connection 19 is provided on each gun arm 6.

[0029] The welding gun device 1 expediently comprises a control device 20, which serves 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 for supplying compressed air to the drive unit 5 (in the case where the drive unit 5 is designed as a pneumatic drive unit).

[0030] Conveniently, the valve device 22 can supply compressed air to the drive unit 5 and / or vent the drive unit 5.

[0031] By way of example, the cloud server 2 is communicatively connected to the welding gun device 1, in particular the control device 20.

[0032] The user device 3 is preferably embodied as a mobile device, for example, a mobile phone or a tablet computer. Furthermore, the user device 3 can be embodied as a computer, for example, a desktop computer or notebook. The user device 3 is communicatively connected, for example, to the welding gun device 1, in particular to the control device 20, and / or to the cloud server 2.

[0033] The following will discuss in more detail how monitoring and / or diagnosis of the welding gun device 1 can be performed. 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 formed, in particular, by the control device 20 and / or the cloud server 2 and / or the user device 3. For example, the computer device 23 is the control device 20, the cloud server 2, or the user device 3.

[0034] The monitoring and / or diagnosis of the welding tong device 1 is carried out in particular by the following steps, which are preferably carried out by the computer device 23: determining a spring effect variable, namely a spring stiffness and / or a spring work, of the tong body 4 on the basis of the detected drive member position, the detected drive unit force and / or the detected drive unit pressure, and, on the basis of the determined spring effect variable, providing diagnostic information about the welding tong device 1 and / or calculating a monitoring variable related to the welding tong device 1.

[0035] As already mentioned above, each tong arm 6 expediently has a respective force introduction point 15 for introducing the drive force provided by the drive unit 5. The spring effect variable expediently refers to the elastic deformability of the tong body 4 between the force introduction points 15. The spring effect variable therefore refers in particular to the spring effect experienced by the drive unit 5 (particularly in the contact position of the tong body 4) between the two force introduction points 15. In particular, the spring effect variable is the spring stiffness of the tong body 4 acting as a spring on the drive unit 5 (particularly in the contact position).

[0036] Optionally, a force build-up spring stiffness and / or a force reduction spring stiffness is determined as the spring effect variable. The force build-up spring stiffness is the spring stiffness of the pliers body 4 that exists when the drive force exerted by the drive unit 5 on the pliers body 4 is increased (particularly in the contact position). The force reduction spring stiffness is the spring stiffness of the pliers body 4 that exists when the drive force exerted by the drive unit 5 on the pliers body 4 is reduced (particularly in the contact position). Preferably, the diagnostic information and / or the monitoring variable is provided based on the force build-up spring stiffness and / or the force reduction spring stiffness.

[0037] Preferably, during the force build-up, there is a substantially linear relationship between an increase in force on the drive unit 5 (e.g. the drive force and / or the detected drive unit force) and the deflection or deformation of the pliers body 4 (which corresponds in particular to the drive member position).

[0038] This linear relationship can be described by the following equation (1): FZylUp=CUp⋅dx+FRefUp

[0039] F ZylUp is the driving unit force or the driving force. C Up is the spring stiffness of the pliers body during force buildup—i.e., the force buildup spring stiffness. dx is a position difference of the drive element 9 (which is accompanied by a corresponding elastic deformation of the pliers body 4) and is determined based on the detected drive element position. F Refupis a force at a reference position of the drive element and should also be referred to as reference force; for example, F Refup a starting force for building strength.

[0040] Due to frictional forces acting on the drive unit 5 and / or the pliers body 4, a hysteresis behavior can occur (particularly in the contact position) with respect to a force-displacement diagram, i.e., with respect to a relationship or dependency between the drive unit force and the drive element position. In particular, the spring stiffness of the pliers body 4 during force reduction—i.e., the force reduction spring stiffness—can be smaller than the force buildup spring stiffness.

[0041] The following equation (2) applies in particular to force reduction: FZylDw=CDw⋅dx+FRefDw

[0042] F ZylDw is the driving unit force or the driving force. C Dwis the spring stiffness of the pliers body during force reduction—i.e., the force reduction spring stiffness. dx is a position difference of the drive element 9 (which is accompanied by a corresponding elastic deformation of the pliers body 4) and is determined based on the detected drive element position. F RefDw is a force at a reference position of the drive element and should also be referred to as reference force; for example, F RefDw a stopping force or relaxation force when reducing force.

[0043] The determination of both the force build-up spring stiffness and the force reduction spring stiffness enables more precise monitoring of the spring stiffness of the pliers body 4. Preferably, the hysteresis behavior of the force-displacement diagram is recorded and used, for example, to calculate friction during force build-up.

[0044] In the following we will discuss in more detail how the spring effect size, in particular the spring stiffness, can be determined.

[0045] To determine the spring effect magnitude, a deformation procedure is preferably carried out in which an elastic deformation of the pliers body 4 is changed by means of the drive unit 5, and during the change in the elastic deformation, the drive element position, the drive element pressure, and / or the drive element force are recorded. The execution of the deformation procedure is controlled, for example, by the computer device 23, in particular the control device 20. The deformation procedure expediently comprises a force build-up procedure and / or a force reduction procedure. During the force build-up procedure, the drive element force and / or the drive force is increased by means of the drive unit 5, for example, by means of the first drive element movement 17 (in particular in the contact position and / or in the deformation state). Expediently, the elastic deformation of the pliers body 4 increases during the force build-up procedure.During the force reduction procedure, the drive unit force and / or drive force is reduced by means of the drive unit 5, for example, by means of the second drive element movement (particularly in the contact position and / or in the deformation state). Advantageously, the elastic deformation of the forceps body 4 decreases during the force reduction procedure.

[0046] Preferably, during the deformation procedure, in particular during the force build-up procedure and / or during the force reduction procedure, a respective temporal profile 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 variable is expediently determined based on one or more of the recorded temporal profiles. For example, the spring effect variable is determined based on the temporal profile of the drive member position and the temporal profile of the drive unit force.

[0047] Furthermore, the spring effect size can be determined based on the time course of the drive member position and the time course of the drive unit pressure.

[0048] Preferably, the spring stiffness is calculated using a linear regression based on the time course of the drive member position and the time course of the drive unit force (which is preferably detected by the force sensor device 13 or calculated based on the time course of the drive unit pressure). For example, the spring stiffness is calculated according to the following equation (3), in particular by the computer device 23: Czk=sFZylsdx⋅rdxFZyl

[0049] C zk is the spring stiffness. S FZyl is the standard deviation of the drive unit force (in particular the time course of the drive unit force). S dxis the standard deviation of the drive element position (in particular the temporal course of the drive element position), in particular the difference between the drive element position and a start position or reference position of the drive element (in particular given at the beginning of the deformation procedure) 9. r dx,FZyl is the correlation between the drive unit force (in particular the temporal course of the drive unit force) and the drive link position (in particular the temporal course of the drive link position), in particular the difference between the drive link position and the start position or reference position.

[0050] In connection with the calculation of the spring stiffness (or other quantities), the term “drive element position” refers in particular to one or more values ​​of the temporal progression of the drive element position and / or the term “drive unit force” refers to one or more values ​​of the temporal progression of the drive unit force.

[0051] Optionally, a reference force F is calculated ref (which, for example, is the reference force F Refup or F RefDw represents) by means of a linear regression based on the time course of the drive member position and the time course of the drive unit force (which is 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 according to the following equation (4), in particular by the computer device 23: FRef=−SFZylsdx⋅rdxFZyl⋅dx¯+FZyl¯

[0052] Regarding sizes S Fzyl , S dx , and r dx FZyl reference is made to the above explanation. FZyl¯ is an average value of the drive unit force. dx is an average value of the drive link position, specifically the difference between the drive link position and the starting or reference position.

[0053] Optionally, the spring stiffness C zk and / or the reference force F Refcalculated using a linear function (for example, equation (1) or (2)) with two data points. A data point is to be referred to as a pair consisting of a value of the drive member position and an associated value of the drive unit force (i.e. the value of the drive unit force at which the value of the drive member position was recorded). The drive member position and the drive unit force are expediently recorded at two different positions of the drive member 9, in particular while the pliers body 4 is in the contact position and / or in the deformation state. Based on equation (1) or (2), for example, a system of equations with two unknowns is set up and solved for the spring stiffness and / or the reference force.

[0054] The calculation of the monitoring variable will be discussed in more detail below. Optionally, several monitoring variables are calculated based on the spring effect variable, in particular based on the spring stiffness. The one or more monitoring variables are calculated, in particular, by the computer unit 23.

[0055] For example, an electrode force and / or a drive unit force estimate and / or the spring work is calculated as the monitoring quantity.

[0056] 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 each other in the contact position and / or the force that an electrode 7 exerts on a contact object, for example, a pair of sheet metal pieces, in the contact position. Conveniently, no sensor is present during operation of the system 10 with which the electrode force can be directly measured.

[0057] Preferably, the electrode force is calculated based on the spring stiffness and a reference spring stiffness. The reference spring stiffness is a spring stiffness that is calculated (particularly before commissioning of the system 10) based on a force measured directly at one or both electrodes 7 using an external force sensor.

[0058] Optionally, the electrode force can be determined based on a force-displacement curve relative to a reference force-displacement curve. The force-displacement curve describes the relationship between the drive unit force detected (particularly during the deformation procedure) and the drive member position. The reference force-displacement curve is expediently determined using the external force sensor and / or preferably describes the relationship between the force detected with the external force sensor (at one or both electrodes 7) and the drive member position.

[0059] For example, the electrode force F Elc calculated according to the following equation (5), in particular by the computer device 23: FElc=cSenUpCZkUp⋅(FZyl−FRefZkUp)+FRefSenUp

[0060] C SenUp is the spring stiffness measured by the external force sensor. C ZkUp is the spring stiffness already explained above. FZyl is the drive unit force. F RefZkUp is the reference force. F RefSenUp is a reference force measured with the external sensor.

[0061] Optionally, a friction value is calculated that describes the friction of the drive unit 5 and / or the friction of the pliers body 4. In particular, the friction value is composed of the friction of the drive unit 5 and the friction of the pliers body 4.

[0062] Preferably, the friction value is calculated on the basis of the drive unit force, for example on the basis of a difference between a value of the drive unit force detected during a force build-up (for example during the force build-up procedure) and a value of the drive unit force detected during a force reduction (for example during the force reduction procedure), in particular at the same drive member position and preferably with the computer device 23.

[0063] For example, the friction value F Rcalculated according to the following equation (6): FR=12⋅(FRefUp−FRefDw)

[0064] F RefUp is a value of the drive unit force recorded during force buildup, for example, a starting force during force buildup. F RefDw is a value of the drive unit force recorded during force reduction, for example a relaxation force during force build-up.

[0065] Furthermore, the friction value can be calculated as the shift in a force-displacement curve between the force buildup and the force reduction. The force-displacement curve describes the relationship between the drive unit force and the drive link position.

[0066] Optionally, an average spring stiffness is calculated, in particular by the computer device 23. The average spring stiffness C zk is calculated in particular according to the following equation (7): Czk=12⋅(CUp+CDw)

[0067] C Upis the force build-up spring stiffness explained above. C Dw is the force reduction spring stiffness explained above. For practical purposes, the diagnostic information is based on the mean spring stiffness C zk For example, in response to the fact that the mean spring stiffness changes to a certain extent, it is concluded that wear is present, and corresponding diagnostic information indicating this wear is generated, in particular by the computer device 23.

[0068] The drive unit force estimate represents an estimate of the drive unit force and is conveniently calculated using equation (1) or (2) (as F ZylUp or F ZylDw). The drive unit force estimate can then be compared with the drive unit force detected by the force sensor device 13 (or the pressure sensor device 14). If a deviation between the drive unit force estimate and the drive unit force exceeds a predetermined threshold, a defect in the force sensor device 13 (or the pressure sensor device) can be concluded, and corresponding diagnostic information indicating the defect can be generated, in particular by the computer device 23.

[0069] Optionally, a spring work is calculated, in particular by the computer unit 23. Preferably, the spring work W Zk calculated based on the drive unit force and the drive link position, in particular according to the following equation (8) WZk=12⋅dFZk⋅dx

[0070] dF Zkis a change in the drive unit force, and dx is a change in the drive link position. Preferably, the spring work is calculated based on two or more values ​​of the drive link position and the drive unit force, which are recorded during the deformation procedure, in particular during the force build-up procedure and / or during the force reduction procedure. The diagnostic information is expediently determined based on the spring work. For example, the computer device 23 checks whether a 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.

[0071] The diagnostic information will be discussed in more detail below. The diagnostic information is preferably determined by the computer device 23.

[0072] Preferably, the diagnostic information relates to electrode force monitoring and / or gun arm breakage detection and / or a cap press-on error and / or a welding gun bearing error and / or a verification of a drive unit measurement variable and / or a calibration error.

[0073] Preferably, the computer device 23 is designed to perform the electrode force monitoring based on the spring stiffness. For example, the computer device 23 is designed to perform the electrode force monitoring based on the electrode force calculated (in particular as explained above). In particular, during the electrode force monitoring, it is checked whether the electrode force changes over time. For example, for this purpose, the electrode force and / or a change in the electrode force is compared with one or more limit values. Preferably, the computer device 23 provides diagnostic information indicating whether an impermissible deviation in the electrode force exists, in particular based on the calculated electrode force and / or the aforementioned comparison. Expediently, the computer device 23 calculates the electrode force repeatedly for the purpose of electrode force monitoring, for example periodically.For example, the computer device repeatedly initiates the deformation procedure and, for each deformation procedure, calculates a current electrode force and / or a change in the calculated electrode force compared to a previously calculated electrode force. For example, the computer device 23 has, in particular, user-definable limit values ​​for assessing whether an impermissible deviation in the electrode force exists and uses these limit values ​​to generate the diagnostic information.

[0074] Preferably, the computer device 23 performs a forceps arm breakage detection based on the spring effect variable, in particular the spring stiffness and / or the spring energy, in order to detect a breakage of a forceps arm 6. For example, the monitored forceps arm 6 is bow-shaped, and the forceps arm breakage detection can also be referred to as bow breakage detection. The computer device 23 expediently checks whether there is a reduction in spring stiffness (in particular during force buildup and / or force reduction) and / or monitors the spring energy and, based on this check and / or monitoring, provides the diagnostic information that expediently indicates that a forceps arm breakage has occurred.

[0075] Preferably, the computer device 23 checks, based on the spring stiffness, whether a cap press-on error is present. In the case of a cap press-on error, one or both electrodes 7 are not sufficiently pressed onto the respective tong arm body 8. The computer device 23 expediently checks whether there is a reduction in spring stiffness (in particular compared to, for example, a previously determined reference spring stiffness) during a force buildup and / or whether there is no change in spring stiffness (in particular compared to, for example, a previously determined reference spring stiffness) during a force reduction. Based on this check, it provides the diagnostic information that expediently indicates that a cap press-on error is present.

[0076] The computer device 23 preferably checks whether a welding gun bearing fault is present, in particular based on the spring stiffness and / or the friction value. The welding gun bearing fault includes, for example, a bearing looseness fault, in which the bearing 16 is loose, and / or an increased friction fault, in which there is increased friction at the bearing. The computer device 23 is in particular designed to detect the bearing looseness fault based on the presence of a reduction in spring stiffness, in particular during force build-up and / or force reduction, and / or the presence of a reduction in friction, in particular during force build-up and / or force reduction, and / or the presence of a reduction in average friction, in particular the friction value. The computer device 23 is designed to provide diagnostic information indicating the bearing looseness fault in response to the detection of the bearing looseness fault.The computer device 23 is particularly configured to detect the increased friction error based on the presence of increased friction, in particular an increased friction magnitude, and / or an increased average stiffness. The computer device 23 is configured to provide diagnostic information indicating the increased friction error in response to the detection of the increased friction error.

[0077] Preferably, the computer device 23 is configured to perform a verification of a drive unit measured variable. A measured variable detected by the sensor arrangement, in particular the drive unit force, the drive unit pressure, and / or the drive unit position, is referred to as a drive unit measured variable. For example, the computer device 23 performs a plausibility check of the drive unit force measured by the sensor arrangement based on a force calculated from a deflection of the pliers body 4 (for example, according to equation (1) or (2)) and, based on the plausibility check, provides diagnostic information that preferably displays the result of the plausibility check.

[0078] Preferably, the computer device 23 is configured to detect a calibration error of the welding gun device 1. In the case of a calibration error, for example, a cap is not pressed on and / or sensor values ​​recorded with the sensor arrangement are not plausible. The computer device 23 is configured to check a force-displacement diagram of the force sensor device 13 for plausibility and to provide corresponding diagnostic information based on the check.

[0079] Preferably, a respective spring effect variable, in particular a respective spring stiffness, is determined for a plurality of welding tong devices, in particular by the computer device 23. Preferably, the spring stiffnesses are stored in a database and / or the welding tong devices are grouped or separated based on their spring stiffness, in particular by the computer device 23, for example when data is retrieved from the database. Preferably, anomaly detection is carried out on the basis of the spring stiffnesses in order to identify an abnormal welding tong device 1, in particular by the computer device 23. For example, the computer device 23 detects that a spring stiffness of a welding tong device deviates significantly from the spring stiffnesses of other identically constructed welding tong devices and identifies this welding tong device as abnormal and expediently outputs corresponding diagnostic information.

[0080] The welding tong device 1 is used, for example, in a resistance pressure welding process for welding sheet metal parts. In particular, the welding tong device 1 enables both force and current conduction to a sheet metal pair. For example, in the production of car bodies, the welding tong device is transported within a room by an industrial robot and positioned toward a welding object.

[0081] Optionally, a diagnostic tool is provided, which is executed in particular on the computer device 23 and preferably uses the spring stiffness and one or more of the monitoring variables for the diagnosis of the welding gun device 1. The spring stiffness and / or the monitoring variables are recorded and evaluated, for example, on the control device 20 and / or transmitted to the cloud server 2 and evaluated there.

[0082] The calculations required to determine the spring effect size, the monitoring sizes and / or the diagnostic information are preferably carried out by means of linearizations, observers or machine learning, for example on the control device 20 and / or the cloud server 2. Optionally, the spring effect size, the monitoring sizes and / or the diagnostic information are transmitted to the user device 3 and displayed there, for example visually, e.g. on a graphic display.

Claims

[1] Method for monitoring and / or diagnosing a welding tong device (1), wherein the welding tong device (1) comprises a tong body (4) with two tong arms (6), each having a respective electrode (7), and a drive unit (5) with a drive member (9) that can be set into a drive member movement and by means of which the tong arms (6) can be set into a tong arm movement relative to one another, comprising the steps of: determining a spring effect variable, namely a spring stiffness and / or a spring work, of the tong body (4) on the basis of a detected drive member position, a detected drive unit force and / or a detected drive unit pressure, and, on the basis of the determined spring effect variable, providing diagnostic information about the welding tong device (1) and / or calculating a monitoring variable related to the welding tong device (1). [2] Method according to claim 1, wherein each tong arm (6) has a respective force introduction point (15) for introducing a drive force provided by the drive unit (5), and the spring effect size relates to an elastic deformability of the tong body (4) present between the force introduction points (15). [3] Method according to claim 1 or 2, wherein a deformation procedure is carried out in which an elastic deformation of the pliers 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 is detected. [4] Method according to any preceding claim, wherein an electrode force, a drive unit force estimate and / or a spring work is calculated as the monitoring variable. [5] Method according to one of the preceding claims, wherein the diagnostic information relates to an electrode force monitoring, a gun arm breakage detection, a cap press-on error, a welding gun bearing error, a verification of a drive unit measurement variable and / or a calibration error. [6] Method according to one of the preceding claims, wherein a respective spring effect value, in particular a respective spring stiffness, is determined for a plurality of welding gun devices. [7] Method according to claim 6, wherein the spring stiffnesses are stored in a database and the welding gun devices are grouped or separated by their spring stiffness. [8] Method according to claim 6 or 7, wherein anomaly detection is carried out on the basis of the spring stiffnesses in order to identify an abnormal welding gun device. [9] Computer device (23) for monitoring and / or diagnosing a welding tong device (1), wherein the welding tong device (1) comprises a tong body (4) with two tong arms (6), each having a respective electrode (7), and a drive unit (5) with a drive member (9) that can be set into a drive member movement, by means of which the tong arms (6) can be set into a tong arm movement relative to one another, wherein the computer device (23) is designed to determine a spring effect variable, namely a spring stiffness and / or a spring work, of the tong body (4) on the basis of a detected drive member position, a detected drive unit force and / or a detected drive unit pressure, and, on the basis of the determined spring effect variable, to provide diagnostic information about the welding tong device (1) and / or to calculate a monitoring variable related to the welding tong device (1).

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