Welding apparatus and welding method

Abstract

In order to provide a welding device which enables an uninterrupted welding with as high a welding quality as possible using a plurality of welding devices in a plurality of simultaneously performed welding processes in the vicinity of one another, it is provided according to the invention that, in a normal operating mode, the control unit of the welding device ignores the first welding voltage signal of a first voltage measuring device and uses the second welding voltage signal of a second voltage measuring device, which detects the arc more closely, for determining the control parameters, that the control unit recognizes a fault condition in the second welding voltage signal from the second welding voltage signal and, in the event of a recognized fault condition, changes over to an emergency operating mode without interrupting the welding process, and that, in the emergency operating mode, the control unit ignores the second welding voltage signal of the second voltage measuring device and uses the first welding voltage signal of the first voltage measuring device for determining the control parameters.

Description

Technical Field

[0001] This invention relates to a welding apparatus for performing a welding process on a workpiece using electrodes. The welding apparatus includes a welding current source having a first connection socket for electrically connecting a welding torch via a welding line and a second connection socket for electrically connecting a workpiece via a grounding line. The welding apparatus includes a first voltage measuring device for detecting a first welding voltage signal between the connection sockets. The welding apparatus also includes a voltage measuring socket for connecting a measuring line or two voltage measuring sockets for connecting the measuring line respectively. A second voltage measuring device is provided in the welding apparatus for detecting a second welding voltage signal between one of the voltage measuring sockets and one of the connection sockets, or between the two voltage measuring sockets. The welding apparatus includes a control unit configured to use at least one of the welding voltage signals to determine control parameters for controlling the welding process and to control the welding current source using the determined control parameters.

[0002] The present invention also relates to a method for performing a welding process on a workpiece using an electrode, wherein the electrode is connected to a welding current source via a welding circuit, and the workpiece is connected to the welding current source via a grounding circuit, wherein the welding circuit is closed after an arc is ignited between the electrode and the workpiece, wherein a first welding voltage signal and a second welding voltage signal are detected in the welding circuit, wherein the second welding voltage signal is detected closer to the arc than the first welding voltage signal, wherein the detected welding voltage signal is transmitted to a control unit, and wherein the control unit uses at least one of the welding voltage signals to determine control parameters for controlling or adjusting the welding process, and the control unit uses the determined control parameters to control the welding current source. Background Technology

[0003] Traditional MIG / MAG or WIG welding equipment typically requires a welding voltage signal from the welding circuit as an actual parameter to regulate the welding process. Here, the welding circuit is known to be constructed such that a welding torch is connected to the electrode (usually the positive terminal) of a welding current source, the torch having (molten or non-molten) electrodes arranged on it, and the other electrode (usually the negative terminal) is connected to the workpiece. Typically, a first and a second connection socket are provided for this purpose; the welding torch can be connected to the first connection socket via a welding line, and the workpiece can be connected to the second connection socket via a grounding line. After an arc is ignited between the electrode and the workpiece in a known manner, the welding circuit is closed, and the desired welding process (e.g., pulsed arc process, short arc process, etc.) can be performed with certain welding parameters (welding current, welding voltage, etc.).

[0004] Here, the welding voltage in the welding circuit is typically measured using a voltage measuring unit, which is usually located within the welding equipment. However, this means that, structurally, only the welding voltage between the connection sockets of the current source can be measured. However, to achieve the most precise control over the welding process, the arc voltage directly on the arc is of interest. However, due to voltage drops in the welding and grounding lines, the arc voltage differs from the socket voltage measured at the connection socket. Therefore, adjusting the welding process based on the measured socket voltage leads to inaccurate control and consequently, unsatisfactory weld quality.

[0005] Therefore, it is known in the prior art to use a model to determine the voltage drop and accordingly correct the measured socket voltage. This can be done, for example, by means of a so-called RL-comparison, in which the welding circuit is modeled by resistance and inductance, as disclosed in EP 1 183 125 B1. This method provides satisfactory results when the welding process is performed using welding equipment. However, if, for example, multiple welding processes are performed in parallel in a common welding unit, it may occur that the grounding lines and / or welding lines of different welding devices are laid directly near each other in space, for example, in parallel sections. This can lead to electromagnetic influences between the voltage-guiding lines, especially voltage induction, which cannot be considered by the model or can only be insufficiently considered.

[0006] Therefore, another feasible approach is known: to determine the welding voltage as close as possible to the arc. Here, voltage measurement is performed directly near the arc, for example, on the electrode (WIG) or on the contact tube in the welding torch (MIG / MAG), and on or as close as possible to the workpiece. Voltage measurement is typically performed using a separate sensor circuit, and the measuring circuit for the actual voltage measurement is, for example, located within the welding equipment. While this type of measurement provides reliable results even in multiple parallel welding processes, it has a disadvantage compared to socket voltage measurement using RL compensation: the sensor circuit must always be connected to the measurement point. If, during the welding process, one of these sensor circuits becomes disconnected or another electrical interruption occurs, the voltage is no longer measured, and arc regulation ceases to function. The welding process then typically must be interrupted because sufficient weld quality can no longer be achieved.

[0007] JP 201451355 A discloses a method for identifying anomalies in wiring within a flexible hose package or in external voltage measurement circuits. The method identifies which measurement circuit exhibits the anomaly. Voltage measurements from two measurement circuits are compared, and when an anomaly is determined to exist in the form of a certain deviation between the two voltage measurements, the current source is stopped and the welding process is interrupted. However, this does not eliminate the possibility of having to interrupt the welding process. Summary of the Invention

[0008] Therefore, the objective of this invention is to provide a welding apparatus and a welding method that can achieve uninterrupted welding with the highest possible welding quality even in multiple welding processes performed simultaneously in a spatially adjacent area.

[0009] According to the present invention, this task is accomplished using the welding apparatus described at the beginning in the following manner: A control unit is configured to ignore the first welding voltage signal from the first voltage measuring device and use the second welding voltage signal from the second voltage measuring device to obtain control parameters in normal operation mode. The control unit is also configured to identify a fault condition in the second welding voltage signal based on the second welding voltage signal and, upon identification of a fault condition, switch to an emergency operation mode without interrupting the welding process. Furthermore, the control unit is configured to ignore the second welding voltage signal from the second voltage measuring device and use the first welding voltage signal from the first voltage measuring device to obtain the control parameters in the emergency operation mode. Thus, the second welding voltage signal can be used to regulate the welding process, and is measured closer to the arc than the first welding voltage signal. Consequently, the measured voltage value of the second welding voltage signal better corresponds to the actual arc voltage of interest on the arc because, on the one hand, voltage drops in the welding line and / or grounding line are not measured together, and on the other hand, potentially induced voltages are not measured together with other welding devices. As soon as a fault in the second welding voltage signal is determined, for example because the measuring line has become loose or broken, the process is automatically switched to the first welding voltage signal without interrupting the welding process. Therefore, the welding process does not need to be interrupted in the event of a fault and can be completed with a slightly reduced welding quality if necessary. After the welding process is completed, defects can be eliminated and a second welding voltage signal with better quality can be reused to control or regulate the welding process.

[0010] According to an advantageous embodiment, the welding torch is electrically connected to the first connection socket via a welding line, and a grounding line connected to or capable of being connected to the workpiece is electrically connected to the second connection socket. A first measuring line is connected to the voltage measuring socket, and this first measuring line is electrically connected to a first voltage measuring point in the welding line located between the first connection socket and the electrode of the welding torch. A second voltage measuring device is configured to detect a second welding voltage signal between the voltage measuring socket and the second connection socket. Alternatively, a second measuring line is connected to the voltage measuring socket, and this second measuring line is electrically connected to a second voltage measuring point in the grounding line or is capable of being electrically connected to the workpiece. This second voltage measuring device is configured to detect a second welding voltage signal between the voltage measuring socket and the first connection socket. Thus, the second welding voltage signal can also be measured using only one measuring line that is closer to the arc than the first welding voltage signal.

[0011] According to a particularly advantageous embodiment, the welding torch is connected to the first connection socket via a welding line, and a grounding line, which is connected to or can be connected to the workpiece, is connected to the second connection socket. A first measuring line is connected to one of the two voltage measuring sockets, and this first measuring line is electrically connected to a first voltage measuring point in the welding line located between the first connection socket and the electrode of the welding torch. A second measuring line is connected to the other voltage measuring socket, and this second measuring line is electrically connected to a second voltage measuring point in the grounding line or can be electrically connected to the workpiece. This allows the second welding voltage signal to be measured advantageously closer to the arc than the first welding voltage signal.

[0012] Preferably, the first and second measuring lines are at least partially twisted. This prevents voltages from being induced in the measuring lines, for example, by other welding devices (whose wiring is laid out nearby), which could distort the measured voltage.

[0013] In the welding apparatus, a feed unit for supplying welding wire to the welding torch can be advantageously provided, wherein the second voltage measuring device and the one or two voltage measuring sockets are disposed on the feed unit, and wherein the second voltage measuring device is connected to the control unit via a communication connection for transmitting the second welding voltage signal. Thus, a separate feed unit spatially separated from the welding current source can be used. The second voltage measuring device can, for example, be integrated into the feed unit and the voltage measuring socket can be arranged on the feed unit. The communication connection can, for example, be configured as a data bus to transmit the second welding voltage signal to the control unit of the welding apparatus with the least possible time delay, which is preferably arranged in the area of ​​the welding current source and therefore also spatially separated from the feed unit.

[0014] Furthermore, it is advantageous to include an additional measuring voltage source in the welding apparatus, which is connected to either two voltage measuring sockets or to one of the voltage measuring sockets and a connection socket, wherein the control unit is configured to identify a fault condition in the second welding voltage signal based on the measuring voltage generated by the measuring voltage source. Particularly advantageous here is that the measuring voltage source has an polarity opposite to that of the welding current source. This simplifies and, in particular, accelerates the identification of fault conditions, as the reversal of polarity can be detected more easily.

[0015] Advantageously, the measuring voltage source is connected to at least one voltage measuring socket with high resistance, and / or the measuring voltage source is connected to at least one voltage measuring socket via at least one known ohmic resistor. With this high-resistance connection, the measured voltage is negligible for detecting the second welding voltage signal in the welding circuit during normal operation, thus preventing distortion of the second welding voltage signal. Alternatively or additionally, when the ohmic resistance of the measuring voltage source is known, the voltage drop across the resistor can be calculated and taken into account when detecting the second welding voltage signal, and the second welding voltage signal can be corrected if necessary.

[0016] Furthermore, a welding circuit model can be stored in the control unit, and the control unit can be configured to identify fault states in the second welding voltage signal based on the welding circuit model. Here, the welding circuit model preferably includes at least one model of a welding circuit, wherein the welding circuit model preferably includes at least one ohmic resistor and at least one inductor. Preferably, the model parameters of this welding circuit model can be adapted to the welding circuit of a real-world welding apparatus. Thus, by means of this model, it is preferably possible to continuously calculate the expected model value for the second welding voltage signal and compare this model value with the currently actually detected second welding voltage signal. Deviations can be detected as fault states.

[0017] Advantageously, a welding robot can be incorporated into the welding apparatus, wherein the welding torch is arranged on the welding robot and is movable by the welding robot, and wherein the first voltage measuring point is arranged on the welding robot, preferably in the area of ​​the welding torch. This also allows for the detection of the welding voltage as close as possible to the arc in an automated welding method and enables switching between normal operation mode and emergency operation mode according to the invention.

[0018] Furthermore, this task is solved using the method according to the present invention. Attached Figure Description

[0019] The following reference Figures 1 to 3 The invention will be described in more detail here. These figures exemplify, schematically and not limitingly, advantageous designs of the invention. Herein, it is shown that:

[0020] Figure 1 The diagram shows a welding apparatus for performing the welding process.

[0021] Figure 2 The measurement circuitry used to identify fault conditions is shown, and

[0022] Figure 3 A welding circuit model is shown for identifying fault conditions. Detailed Implementation

[0023] exist Figure 1 The diagram schematically presents a welding apparatus 1 for performing a welding method. The presented welding apparatus 1 is configured to perform a welding method utilizing a molten electrode, i.e., the known MIG / MAG method or the general metal shielding gas method (MSG). Of course, this is only to be understood as exemplary, and the invention can also be used in welding methods utilizing a non-molten electrode (WIG). The presented welding apparatus 1 has a welding device 2 and a welding robot 3, on which a welding torch 4 is arranged. The welding torch 4 can be moved by the welding robot 3 with available degrees of freedom to produce a weld (not shown) with a specific geometry on the workpiece W. However, the welding robot 3 is only optional, and the welding torch 4 can of course also be guided by hand by the user.

[0024] A molten electrode E in the form of welding wire is commonly provided on the welding torch 4. The welding wire can be supplied to the welding torch 4 by means of a feed unit 6, and the welding wire is stored, for example, in a wire reservoir 5. The feed unit 6 may have a drive unit 6a to supply the welding wire to the welding torch 4 or the (not shown) molten pool on the workpiece W at a desired feed rate. The drive unit 6a can be operated by a suitable control unit to control or adjust the feed rate as a welding parameter according to the welding process being performed. In the presented example, the feed unit 6 is part of the welding robot 3; therefore, a robot control unit 11 that controls the drive unit 6a in a suitable manner can be used as the control unit for controlling the feed rate.

[0025] To control the welding method, the robot control unit 11 can communicate with the control unit 7, preferably arranged in the welding equipment 2, of the welding apparatus 1, so as to synchronize the robot's feed speed with other welding parameters (welding current I, welding voltage U, etc.) of the welding process being performed. Through the robot control unit 11, not only the welding process performed by the robot control unit but also the movement of the robots 3 can be controlled and coordinated with each other. Of course, this is again merely exemplary; the propulsion unit 6 can also be part of the welding equipment 2, for example, integrated into it. This can be the case, for example, when the welding robot 3 is not used and the welding torch 4 is manually guided by the user.

[0026] Of course, multiple feed units 6 can also be provided on the welding torch 4, such as additional (not shown) feed units, so that the feed speed can be dynamically controlled or adjusted. This can be particularly advantageous for performing known CMT welding processes, so as to change the wire feed between a positive wire feed in the direction towards the workpiece W and a negative wire feed in the direction away from the workpiece W as quickly as possible. The control unit 7 and / or the robot control unit 11 can also be operated by a (not shown) higher-level control unit, for example, to centrally control the welding methods and processes of multiple welding devices 1 and to synchronize these welding methods and processes with each other.

[0027] In welding apparatus 1, for example in welding equipment 2, a welding current source 8 having a first connecting socket AB1 and a second connecting socket AB2 is provided in a known manner. The first connecting socket AB1 and the second connecting socket AB2 are electrically connected to the welding current source 8. A welding torch 4 can be connected to the first connecting socket AB1 via a welding line 9. The second connecting socket AB2 can be connected to the workpiece W via a grounding line M. Within the scope of this invention, connecting sockets AB1 and AB2 can be understood not only as detachable connections but also as fixed, i.e., non-detachable connections. However, detachable, preferably standardized couplers are typically used as connecting sockets AB1 and AB2. Generally, the first connecting socket AB1 is configured as the positive terminal, and the second connecting socket AB2 is configured as the negative terminal, as in... Figure 1 As presented in the diagram. However, in principle, it is also possible to reverse the polarity of the connecting sockets AB1 and AB2 via the welding current source 8. The welding current source 2 supplies the required welding current I to the welding torch 4 in a known manner via the welding circuit 9. Figure 2 For this purpose, for example, a contact sleeve 4a can be provided on the welding torch 4, which is connected to the welding line 9 and makes electrical contact with the welding wire through the contact sleeve.

[0028] As is well known, welding line 9 can also be guided in hose package P, which may contain additional lines besides welding line 9, which are necessary or advantageous for the welding process. To perform the welding process, a shielding gas (active or inert) is typically used to isolate the molten pool from the environment and prevent oxidation. The shielding gas can be supplied to the welding torch 4, for example, from a (not shown) shielding gas container via a suitable shielding gas line, which can also be guided in hose package P. Alternatively, it can be supplied separately. A pressure regulator, for example in the form of a bottle device arranged on the shielding gas container, can also be provided here, controlled, for example, by control unit 7, to control the flow rate of the shielding gas. Furthermore, a cooling medium for cooling the welding torch 4 can be supplied through hose package P if necessary. Additionally, a control line can be provided in hose package P, for example, to control the aforementioned propulsion unit, which can be additionally arranged on the welding torch 4 if necessary.

[0029] In the presented example, the hose pack P connects the first connection socket AB1 of the welding equipment 2 to the robot connection socket 10 of the welding robot 3. Between the robot connection socket 10 of the welding robot 3 and the welding torch 4, the welding line 9 and, if necessary, additional lines are guided within the robot arm 3a. Of course, the hose pack P can also be directly connected to the welding torch 4, as in... Figure 1As shown by the dotted hose p', in the manual welding apparatus 1, where the welding torch 4 is guided by hand (rather than by the welding robot 3), the torch 4 can be connected, for example, directly via the hose p to the welding equipment 2 equipped with the welding current source 8. This is typically the case in WIG welding apparatuses or MIG / MAG welding apparatuses, where the propulsion unit 6 is integrated into the welding equipment 2.

[0030] However, in most manual MIG / MAG welding apparatuses, the welding torch 4 is connected to a separate propulsion unit 6, for example, via a first hose pack, and the propulsion unit 6 is connected to the welding device 2, for example, via a second hose pack. Therefore, the system structure is similar to... Figure 1 The welding apparatus with a welding robot is presented. In the presented example, the propulsion unit 6 is arranged on the welding robot 3. Therefore, in the example shown, the molten electrode E (welding wire) is supplied to the welding torch 4 separately, not through the hose package P. On or within the robot arm 3a, the welding wire can be guided again, for example, along with the welding line and additional lines if necessary. On the contact bushing 4a, the welding wire can be electrically contacted by the welding line 9.

[0031] To perform a welding process (e.g., pulse welding, CMT welding, jet arc welding, etc.), a first potential (usually negative) is applied to the workpiece W via grounding line M, and a second potential (usually positive) is applied to the welding wire, which serves as the electrode E, via welding line 9. An arc LB is formed between the free end of the welding wire (or the non-melting electrode in the WIG welding method) and the workpiece W. Figure 2 After ignition, the welding circuit is closed and the welding current I flows. Through the arc LB, the welding wire and a portion of the workpiece W melt, thereby creating a material-locked connection between the welding wire and the workpiece W.

[0032] During the welding process, the control unit 7 controls the welding current source 8 to set specific welding parameters, such as welding voltage U, welding current I, frequency f, etc. Additionally, the control unit 7 can manipulate other units to set other non-electric welding parameters, such as one or more feed units 6 and the pressure regulator of the shielding gas container, to control the wire feed rate and shielding gas volume. The welding parameters to be set are largely dependent on the welding process to be performed and can generally be considered known. Depending on the welding process being performed, the welding parameters can, of course, vary in quality and quantity.

[0033] In the welding apparatus 1, such as on the welding equipment 2, a (not shown) user interface may also be provided, which communicates with the control unit 7. The user can make specific settings through the user interface. For example, a specific welding process can be selected, and specific welding parameters can be selected and / or set. For example, a predefined welding plan with specific preset welding parameters can also be stored in the control unit 7, which can be selected by the user through the user interface. In the welding apparatus 1 with the welding robot 3 presented, a superior robot control unit 11 can also be provided, which communicates with the control unit 7 of the welding equipment 7 in a suitable manner. In this case, the control of the welding process and the setting of welding parameters can also be performed by the user through the robot control unit 11 or the user interface connected to it.

[0034] In welding apparatus 1, here in welding equipment 2, a first voltage measuring device 12 is also provided to measure a first welding voltage signal U1 between connecting sockets AB1 and AB2. Furthermore, in the welding apparatus 1 presented in the example, two voltage measuring sockets MB1 and MB2 are also provided for connecting measuring lines ML1 and ML2 respectively, and a second voltage measuring device 13 is provided for measuring a second welding voltage signal U2 between voltage measuring sockets MB1 and MB2. The first and / or second voltage measuring devices 12 and 13 can be constructed as separate units, as in... Figure 1 As shown in the diagram, it can also be integrated into the control unit 7 in a suitable manner.

[0035] The control unit 7 and / or voltage measuring devices 12, 13 can be constructed in suitable hardware and / or software form. In the presented example, the second voltage measuring device 13 is integrated, for example, into the welding equipment 2, and the two voltage measuring sockets MB1, MB2 are also disposed on the welding equipment 2, for example, disposed on the housing of the welding equipment 2. Thus, the measuring lines ML1, ML2 can be directly connected to the welding equipment 2. However, in principle, it is sufficient to provide only one voltage measuring socket MB1 or MB2 in the welding apparatus 1. In this case, the second voltage measuring device 13 is configured to detect a second welding voltage signal U2 between one of the available voltage measuring sockets MB1, MB2 and connecting sockets AB1, AB2.

[0036] like Figure 1As shown, the welding apparatus 1 may include an external propulsion unit 6 for supplying welding wire to the welding torch 4, which is spatially separated from the welding current source 8. This can be used not only in the welding robot 3 shown, but also in manual welding. A second voltage measuring device 13 and two voltage measuring sockets MB1, MB2 (or one voltage measuring socket MB1 or MB2) may also be provided on the propulsion unit 6, and the voltage measuring device 13 can be connected to the control unit 7 via a suitable communication connection to transmit the second welding voltage signal U2. A known data bus can be used as the communication connection to transmit the second welding voltage signal U2 with the smallest possible time delay. However, the propulsion unit 6 may also be structurally integrated with the welding current source 8 in a known manner and, for example, integrated together with the welding current source 8 and, if necessary, other components (control unit 7, voltage measuring devices 12, 13, etc.) within the housing of the welding equipment 2.

[0037] The control unit 7 is configured to determine control parameters for controlling the welding process using at least one of the welding voltage signals U1 and U2, and to control the welding current source 8 based on the determined control parameters. For example, a suitable regulator can be provided in the control unit 7 that uses at least one of the welding voltage signals U1 and U2 as the actual value for this regulation. As a rated value, for example, a welding voltage U preset by the welding circuit corresponding to the desired welding process can be used. Thus, the regulator calculates the regulation parameter as the control parameter according to a determined regulation law. The control unit 7 can then manipulate the welding current source 8 with the determined regulation parameter, for example, to set the rated value of the welding voltage U.

[0038] According to the present invention, in normal operation mode, control unit 7 ignores the first welding voltage signal U1 of the first voltage measuring device 12 and uses the second welding voltage signal U2 of the second voltage measuring device 13 to obtain control parameters. Control unit 7 is also configured to identify a fault condition in the second welding voltage signal U2, as will be described in more detail below. If control unit 7 identifies a fault condition in the second welding voltage signal U2, control unit 7 automatically switches to emergency operation mode in the shortest possible time without interrupting the welding process. In emergency operation mode, control unit 7 now ignores the second welding voltage signal U2 of the second voltage measuring device 12 and instead uses the first welding voltage signal U1 of the first voltage measuring device 12 to obtain control parameters.

[0039] Therefore, to perform the welding process, the second welding voltage signal U2 is used according to standard, and the emergency operation mode is automatically activated and the first welding voltage signal U1 is used only in the event of a fault. No user intervention is required to identify the fault state and switch from the normal operation mode to the emergency operation mode. Of course, in the emergency operation mode, the aforementioned RL-comparison can also be performed by means of a suitable welding circuit model, which can be implemented, for example, in the control unit 7. For example, a fault state exists in the second welding voltage signal U2 of the second voltage measuring device 13 when the measuring lines ML1, ML2 are disconnected from the corresponding voltage measuring sockets MB1, MB2, or when the measuring lines ML1, ML2 are broken or partially damaged. Within the scope of this invention, the fault state of the second welding voltage signal U2 can generally be understood as a state in which the welding voltage signal U2 is no longer detected at least temporarily, or the detected welding voltage signal U2 deviates at least temporarily from the value expected according to the welding process being performed. "Temporarily" can be understood, for example, as a defined, preset, or settable time period.

[0040] In the operation of welding apparatus 1, it is advantageous that the first measuring line ML1 is connected to the first voltage measuring socket MB1, and the second measuring line ML2 is connected to another voltage measuring socket MB2, as in... Figure 1 As shown in the diagram. Connecting sockets AB1, AB2 and voltage measuring sockets MB1, MB2 can, for example, be installed on the housing of welding equipment 2, as shown in... Figure 1 As presented in the diagram. When the external propulsion unit 6 is provided, as described above, voltage measurement sockets MB1, MB2 (or one voltage measurement socket MB1, MB2) can also be directly provided on the propulsion unit 6. If the second voltage measuring device 13 is provided in the welding equipment 2, the measuring lines ML1, ML2 can circulate through the propulsion unit 6. If the second voltage measuring device 13 is provided in the propulsion unit 6, then the second welding voltage signal U2 can be directly transmitted to the control unit 7 via a communication connection, which is preferably also arranged in the welding equipment 2. Similar to the connection sockets AB1, AB2, within the scope of the invention, the voltage measurement sockets MB1, MB2 can be understood not only as detachable couplers or plug connectors, but also as fixed, that is, non-detachable connectors.

[0041] The first measuring line ML1 is preferably electrically connected to the first voltage measuring point MP1 in the welding line 9, located between the first connecting socket AB1 and the electrode E of the welding torch 4. The second measuring line ML2 is preferably electrically connected to the second voltage measuring point MP2 in the grounding line M or directly to the workpiece. Thus, compared to the first welding voltage signal U1 measured between the two connecting sockets AB1 and AB2, the second welding voltage signal U2 can be measured closer to the arc LB. In principle, the closer the second welding voltage signal U2 is to the arc LB, the more accurately the measured voltage corresponds to the arc voltage of interest, because the voltage drop in the welding line 9 is smaller. The connection between the measuring lines ML1 and ML2 and the voltage measuring points MP1 and MP2 can be fixed or detachable.

[0042] As described above, the welding apparatus 1 may also include only one voltage measurement socket MB1 or MB2; in the example shown, for instance, only the first voltage measurement socket MB1 or the second voltage measurement socket MB2 may be provided. As shown, the first voltage measurement socket MB1 may be connected to the first voltage measurement point MP1 of the welding line 9 via the first measurement line ML1. In this case, the second voltage measuring device 13 measures the second welding voltage signal U2 between the first voltage measurement point MP1 and the second connection socket AB2, which is connected to the workpiece W via the grounding line M. However, only the second voltage measurement socket MB2 may be provided, and this second voltage measurement socket may be electrically connected to the second voltage measurement point MP2 in the grounding line M via the second measurement line ML2, or directly to the workpiece W, as presented.

[0043] In this configuration, the second voltage measuring device 13 measures the second welding voltage signal U2 between the second voltage measuring point MP2 and the first connecting socket AB1, which is connected to the welding torch 4 via the welding line 9. Thus, the second welding voltage signal U2 can also be measured using only one voltage measuring socket MB1, MB2 and measuring lines ML1, ML2 near the arc ground. However, according to the embodiment, the voltage drop in the welding line 9 or the grounding line is not considered. Therefore, it is advantageous that in the welding apparatus 1, as in... Figure 1 As shown in the figure, there are two voltage measurement sockets MB1 and MB2, which are connected to welding line 9 or grounding line M or workpiece W via measurement lines ML1 and ML2 respectively.

[0044] In the example shown, the first voltage measurement point MP1 is located, for example, near the welding torch 4 on the robot arm 3a and is therefore inaccessible or only poorly accessible from the outside. Therefore, it is advantageous to provide a suitable measurement line connection socket 16 on the welding robot 3, to which the first measurement line ML1 can be easily connected. The section of the first measurement line ML1 extending between the measurement line connection socket 16 and the first voltage measurement point MP1 is here part of the welding robot 3 and can be arranged in or on the robot arm 3a. The second voltage measurement point MP2 is here directly on the workpiece W and can be constructed, for example, as a suitable terminal.

[0045] However, the first voltage measurement point can also be located in a position easily accessible from the outside, such as on the robot connection socket 10, as... Figure 1 As shown by the voltage measurement point MP1' in the diagram. However, in this case, the second welding voltage signal U2 is measured further away from the arc LB compared to the first voltage measurement point MP1 on the robotic arm 3a. This also results in a larger voltage drop due to the greater length of the welding line 9, and thus a larger deviation between the measured welding voltage and the actual arc voltage. Advantageously, the first voltage measurement point MP1 is therefore as close as possible to the arc LB. When a suitable grounding line M is provided, the second voltage measurement point MP2 can also be arranged directly on the grounding line M. Here, it is also advantageous that the second voltage measurement point MP2 is as close as possible to the arc LB. In a manual welding device with a separate propulsion unit 6, the first voltage measurement point MP1' can also be similarly arranged on the propulsion unit 6, for example, similar to the method used in the diagram. Figure 1 As shown in the diagram. The second voltage measurement point MP2 can, for example, be located directly on the workpiece W.

[0046] It is preferable to use special measuring lines ML1 and ML2 with the smallest possible, preferably less than 0.5 ohmic resistance. Because no current or only a negligible current flows into the measuring lines during voltage measurement, the voltage drop through measuring lines ML1 and ML2 is very small compared to the voltage drop through welding line 9 and can therefore be ignored. Therefore, the length of measuring lines ML1 and ML2 contributes only insignificantly to the voltage drop. Furthermore, it is advantageous that the first measuring line ML1 and the second measuring line ML2 are at least partially twisted. Thus, it is well known that inductive coupling can be reduced, i.e., voltage induced into measuring lines ML1 and ML2 by other current-carrying lines (e.g., welding line 9, grounding line M) near measuring lines ML1 and ML2. Figure 1In this context, this is indicated by the dotted-line twisted area B, which connects to the voltage measurement sockets MB1 and MB2. Similarly, it is advantageous for the measurement lines ML1 and ML2 to be twisted over as much of their length as possible. In the presented example, the twisted area B ends where the measurement lines ML1 and ML2 separate towards the robot arm 3a or towards the workpiece W. If necessary, the grounding potential can be further directed to the vicinity of the robot arm 3a or the welding torch 4, thereby achieving the twisting of the measurement lines ML1 and ML2 over a larger range of their length.

[0047] The following uses Figure 2 and Figure 3 Two variant schemes for identifying fault states in the second welding voltage signal U2 are described. These two variant schemes can be used alternatively, but of course, they can also be used redundantly. Figure 2 Presented in Figure 1 The equivalent circuit diagram of the welding circuit. The welding circuit closes after the arc LB between electrode E and workpiece W is ignited, allowing the welding current I supplied by welding current source 8 to flow. During the welding process, welding parameters (welding current I, welding voltage U, etc.) are set, and particularly adjusted, by control unit 7. The first welding voltage signal U1 is measured by the first voltage measuring device 12 of the welding apparatus 1. Figure 2 Connection sockets AB1 and AB2 not shown in the image (see...) Figure 1 The second welding voltage signal U2 is measured between the first voltage measurement point MP1 in the welding line 9 and the second voltage measurement point MP2 in the grounding line M (or directly on the workpiece W) by means of the second voltage measuring device 13 of the welding apparatus 1. The second voltage measuring device 13 is exemplarily arranged inside the welding equipment 2. Additionally, a suitable current measuring device 15 for measuring the welding current I in the welding apparatus 1, such as in the welding equipment 2, can also be provided. Figure 2 and Figure 3 As shown in the image.

[0048] To identify fault conditions in the second welding voltage signal U2, a measuring voltage source 14 can be attached to the welding current source 8 in the welding apparatus 1. The measuring voltage source 14 is electrically connected to two voltage measuring sockets MB1 and MB2 to apply a measuring voltage UM to the measuring lines ML1 and ML2. If only one voltage measuring socket MB1 or MB2 is provided, the measuring voltage source 14 is connected to the corresponding voltage measuring socket MB1 or MB2 and one of the connecting sockets AB1 and AB2. Here, the control unit 7 can identify fault conditions in the second welding voltage signal U2 of the second voltage measuring device 13 based on the measuring voltage UM generated by the measuring voltage source 14. When a fault condition occurs during the welding process, for example, due to the measuring lines ML1 and ML2 becoming loose from the respective voltage measuring sockets MB1 and MB2 or the respective measuring points MP1 and MP2, or due to the measuring lines ML1 and ML2 breaking, the second voltage measuring device 13 only measures the measuring voltage UM provided from the measuring voltage source 14. The measuring voltage UM is advantageously different in quality and quantity from the welding voltage U and is known. The measured voltage UM can be preset with a known characteristic voltage signal, such as a constant voltage or alternating voltages at a specific frequency. Thus, the control unit 7 can easily identify when a fault condition exists, since only the characteristic voltage is measured during a fault condition.

[0049] To enable the simplest and fastest possible identification of fault conditions, it is advantageous that the measuring voltage source 14 has polarity opposite to that of the welding current source 8, as in... Figure 2 As presented in the diagram. Therefore, in the event of a fault, the sign of the second welding voltage signal U2 detected by the second voltage measuring device 13 is changed. Here, fault condition identification can, for example, be performed within 20 μs to 50 μs.

[0050] Furthermore, it is advantageous that the voltage measuring source 14 is connected to at least one voltage measuring socket MB1, MB2 with high resistance. Additionally or alternatively, it may be advantageous that the voltage measuring source 14 is connected to at least one voltage measuring socket MB1, MB2 via at least one known ohmic resistor RM. High resistance is understood to mean the highest possible ohmic resistance, for example, >100kΩ. According to... Figure 2In the circuit, for example, a 100kΩ ohmic resistor RM is arranged between the positive terminal of the measuring voltage source 14 and the first voltage measuring socket MB1, and a 100kΩ ohmic resistor RM is arranged between the negative terminal of the measuring voltage source 14 and the second voltage measuring socket MB2. Through this high-impedance connection, the measuring voltage UM is negligible for detecting the second welding voltage signal U2 in the welding circuit during normal operation (no fault condition), thus preventing significant distortion of the second welding voltage signal U2. Alternatively or additionally, when the ohmic resistor RM of the measuring voltage source 14 is known, the voltage drop across the resistor RM can be calculated and considered when detecting the second welding voltage signal U2, so that the second welding voltage signal U2 can be corrected if necessary.

[0051] However, in principle, fault conditions in the second welding voltage signal U2 of the second voltage measuring device 13 can also be identified without the additional measuring voltage source 14. For this purpose, for example, a welding circuit model can be stored in the control unit 7, through which fault conditions can be identified. Figure 3 An exemplary welding circuit model is presented. The welding circuit model preferably includes at least one model of welding line 9, wherein the model of welding line 9 includes at least one ohmic resistor Ri and at least one inductor Li. Figure 3 In the example presented, the model of soldering circuit 9 has, for example, two ohmic resistors R1, R2 and two inductors L1, L2. The first resistor R1 and the first inductor L1 constitute the portion of soldering circuit 9 between the first connection socket AB1 and the first measuring point MP1 (see also...). Figure 1 and Figure 2 The second resistor R2 and the second inductor L2 constitute the portion of the welding circuit 9 between the first measurement point MP1 and the electrode E. The electric arc LB can also be depicted in the form of an ohmic resistance RLB.

[0052] Of course, other components can also be considered in the welding circuit model, such as measurement lines ML1, ML2, connection sockets AB1, AB2, voltage measurement sockets MB1, MB2, and measurement points MP1, MP2, in order to depict the actual structure of the welding apparatus 1 as realistically as possible. For this purpose, corresponding ohmic resistors R, inductors L, and other electrical equivalent elements can be set as needed. Furthermore, to make the welding circuit model fit as well as possible to the welding circuit of the actual constructed welding apparatus 1, it is advantageous that the model parameters of the welding circuit model are settable or automatically identifiable. For example, variable ohmic resistors R, inductors L, etc., can be set, which can be changed by the user according to the specific implementation structure, for example, via the user interface on the welding equipment 2 or via a higher-level control unit, such as the robot control unit 11.

[0053] For example, the model parameters of the welding circuit model can be automatically identified through a comparison before the welding process is executed. However, in this comparison, no welding is actually performed; only the welding torch 4 is moved to the workpiece W, so that the contact tube 4a contacts the welding position of the workpiece W. Here, a comparison algorithm is executed by means of the control unit 7 to obtain the model parameters (e.g., inductance and ohmic resistance) of the welding circuit model. During the welding process, where the magnitude of the welding current I changes with time (e.g., in pulse welding), the inductance can also be determined as a model parameter if necessary during the welding process. Here, the current value of the inductance is determined during the phase in which the current changes, and the model parameters can be directly updated if necessary.

[0054] To identify fault conditions in the second welding voltage signal U2 of the second voltage measuring device 13, the control unit 7 compares the second welding voltage signal U2 actually measured by the second voltage measuring device 13, preferably continuously or at preset time steps, with the calculated second welding voltage signal U2 from the welding circuit model. If a preset or settable deviation is identified, for example, due to the measurement lines ML1, ML2 being loose, broken, or damaged, the control unit 7 automatically switches from the normal operation mode to the emergency operation mode, during which the welding process continues. In the emergency operation mode, the control unit 7 uses the first welding voltage signal U1 instead of the second welding voltage signal U2 to obtain control parameters. Therefore, the welding process can continue and end without interruption. After the process ends (when the arc LB is extinguished), fault diagnosis can be performed on the welding apparatus 1 and the fault can be eliminated.

[0055] For example, if the fault is caused by a loose measuring line ML1, ML2, the corresponding measuring lines ML1, ML2 can be reconnected to the corresponding voltage measuring sockets MB1, MB2 or measuring points MP1, MP2, and a new welding process can start again in normal operating mode. For this purpose, for example, it can be specified that the control unit 7 stores the normal operating mode as an initial setting after each start of the welding process, i.e., after the arc LB is ignited. To avoid large faults in the weld (which could be caused by an incorrect or missing second welding voltage signal U2 during the switching period), the switch from normal operating mode to emergency operating mode is performed in the shortest possible time, preferably within 25 μs to 100 μs. As already mentioned, a known RL-comparison can also be performed in emergency operating mode, in which the first welding voltage signal U1 is used to adjust the welding voltage, and the voltage drop in welding line 9 is considered when the welding voltage is detected, determined by a model in the RL-comparison.

[0056] Therefore, voltage drop in welding line 9 can also be considered in emergency operation mode. Of course, welding can continue for a longer period in emergency operation mode; however, this may lead to a decrease in welding quality. As mentioned at the beginning, this could be the case, for example, when performing multiple parallel welding processes, where welding line 9 and grounding line M are spatially located. Undesirable voltage induction may occur in adjacent lines due to the time-varying welding current in one line, which could cause distortion of the first welding voltage signal U1 measured at connectors AB1 and AB2. Because the first welding voltage signal U1 is used to regulate the welding process in emergency operation mode, this can lead to undesirable deviations from the preset welding process and, if necessary, insufficient welding quality. To avoid these problems, it is therefore advantageous to switch back to normal operation mode as quickly as possible, in which the second welding voltage signal U1 is considered for regulating the welding process, which is substantially unaffected by the inductive coupling of the lines.

[0057] Finally, it should be reiterated that the present invention is not limited to the welding apparatus 1 with welding robot 3 and MSG welding method. Of course, the present invention can also be applied to welding apparatus 1 without welding robot 3, which is configured for manual welding by hand. Similarly, the present invention is not limited to MSG welding method, but can certainly be applied to other welding methods, such as WIG welding using non-melting electrodes.

Claims

1. A welding apparatus (1) for performing a welding process on a workpiece (W) using electrodes (E), wherein, A welding current source (8) is provided in the welding apparatus (1), the welding current source having a first connection socket (AB1) for electrically connecting the welding torch (4) by means of a welding line (9) and a second connection socket (AB2) for electrically connecting the workpiece (W) by means of a grounding line (M), wherein a first voltage measuring device (12) is provided in the welding apparatus (1) for detecting a first welding voltage signal (U1) between each connection socket, wherein a voltage measuring socket (MB1, MB2) for connecting one measuring line (ML1, ML2) or two voltage measuring sockets (MB1, MB2) for connecting one measuring line (ML1, ML2) is provided in the welding apparatus (1), wherein a second voltage measuring device (13) is provided in the welding apparatus (1) for detecting a second welding voltage signal (U2) between the one voltage measuring socket (MB1, MB2) and one of the connection sockets or between the two voltage measuring sockets (MB1, MB2), wherein a first voltage measuring device (12) is provided in the welding apparatus (1) for detecting a first welding voltage signal (U2) between the one voltage measuring socket (MB1, MB2) and one of the connection sockets or between the two voltage measuring sockets (MB1, MB2), wherein a second voltage measuring device (13) is provided in the welding apparatus (1) for detecting a second welding voltage signal (U2) between the one voltage measuring socket (MB1, MB2) and one of the connection sockets or between the two voltage measuring sockets (MB1, MB2), wherein a second voltage measuring device (13) is provided in the welding apparatus (1) for detecting a first welding voltage signal (U2) between the one voltage measuring socket (MB1, MB2) and one of the connection sockets or between the two voltage measuring sockets (MB1, MB2), wherein a second voltage measuring device (1) is provided in the welding apparatus (1) for detecting a second welding voltage signal (U2) between the one voltage measuring socket (MB1, MB2) and one of the connection sockets. The system includes a control unit (7) configured to use at least one of the welding voltage signals to obtain control parameters for controlling or adjusting the welding process and to control the welding current source (8) by means of the obtained control parameters. The control unit (7) is configured to ignore the first welding voltage signal (U1) of the first voltage measuring device (12) and use the second welding voltage signal (U2) of the second voltage measuring device (13) to obtain the control parameters in a normal operating mode. The control unit (7) is also configured to identify a fault state in the second welding voltage signal (U2) based on the second welding voltage signal (U2) and, upon identifying a fault state, switch to an emergency operating mode without interrupting the welding process. Furthermore, the control unit (7) is configured to ignore the second welding voltage signal (U2) of the second voltage measuring device (13) and use the first welding voltage signal (U1) of the first voltage measuring device (12) to obtain the control parameters in the emergency operating mode.

2. The welding apparatus (1) according to claim 1, characterized in that, The welding torch (4) is electrically connected to the first connection socket (AB1) via the welding line (9), and the grounding line (M) connected to or capable of being connected to the workpiece (W) is electrically connected to the second connection socket (AB2). A first measuring line (ML1) is connected to the voltage measuring socket, which is electrically connected to a first voltage measuring point (MP1) in the welding line (9) between the first connection socket (AB1) and the electrode (E) of the welding torch (4). A second voltage measuring device (13) is configured to detect a second welding voltage signal (U2) between the voltage measuring socket and the second connection socket (AB2). Alternatively, a second measuring line (ML2) is connected to the voltage measuring socket, which is electrically connected to the second voltage measuring point (MP2) in the grounding line (M) or capable of being electrically connected to the workpiece (W). The second voltage measuring device (13) is configured to detect a second welding voltage signal (U2) between the voltage measuring socket and the first connection socket (AB1).

3. The welding apparatus (1) according to claim 1, characterized in that, The welding torch (4) is connected to the first connection socket (AB1) via the welding line (9), and the grounding line (M) connected to or capable of being connected to the workpiece (W) is connected to the second connection socket (AB2). A first measuring line (ML1) is connected to one of the two voltage measuring sockets. The first measuring line is electrically connected to a first voltage measuring point (MP1) in the welding line (9) between the first connection socket (AB1) and the electrode (E) of the welding torch (4). A second measuring line (ML2) is connected to the other voltage measuring socket. The second measuring line is electrically connected to a second voltage measuring point (MP2) in the grounding line (M) or can be electrically connected to the workpiece (W). The first measuring line (ML1) and the second measuring line (ML2) are at least partially twisted.

4. The welding apparatus (1) according to any one of claims 1 to 3, characterized in that, The welding device (1) is provided with a propulsion unit (6) for supplying welding wire to the welding torch (4). A second voltage measuring device (13) and one voltage measuring socket (MB1, MB2) or two voltage measuring sockets (MB1, MB2) are provided on the propulsion unit (6). The second voltage measuring device (13) is connected to the control unit (7) via a communication connection in order to transmit the second welding voltage signal (U2).

5. The welding apparatus (1) according to any one of claims 1 to 3, characterized in that, An additional measuring voltage source (14) is provided in the welding apparatus (1), which is connected to the two voltage measuring sockets (MB1, MB2) or to one voltage measuring socket (MB1, MB2) and one of the connection sockets, wherein the control unit (7) is configured to identify a fault state in the second welding voltage signal (U2) based on the measuring voltage (UM) generated by the measuring voltage source (14).

6. The welding apparatus (1) according to claim 5, characterized in that, The measuring voltage source (14) has the opposite polarity to the welding current source (8).

7. The welding apparatus (1) according to claim 5, characterized in that, The voltage measuring source (14) is connected to at least one voltage measuring socket (MB1, MB2) with high resistance, and / or the voltage measuring source (14) is connected to at least one voltage measuring socket (MB1, MB2) via at least one known ohmic resistor (RM).

8. The welding apparatus (1) according to any one of claims 1 to 3, characterized in that, The control unit (7) stores a welding circuit model and is configured to identify a fault state in a second welding voltage signal (U2) based on the welding circuit model, wherein the welding circuit model includes at least one model of a welding line (9), wherein the model of the welding line (9) includes at least one ohmic resistor (R1, R2) and at least one inductor (L1, L2).

9. The welding apparatus (1) according to claim 8, characterized in that, The model parameters of the welding circuit model can be adapted to the welding circuit of the actual constructed welding device (1).

10. The welding apparatus (1) according to claim 2 or 3, characterized in that, A welding robot (3) is provided in the welding device (1), wherein a welding torch (4) is arranged on the welding robot (3) and can be moved by the welding robot (3), and a first voltage measurement point (MP1) is provided on the welding robot (3).

11. The welding apparatus (1) according to claim 10, characterized in that, The first voltage measurement point on the welding robot is set in the area of ​​the welding torch (4).

12. A method for performing a welding process on a workpiece (W) using an electrode (E), wherein, The electrode (E) is connected to the welding current source (8) via welding line (9), and the workpiece (W) is connected to the welding current source (8) via grounding line (M). The welding circuit is closed after the arc (LB) between the electrode (E) and the workpiece (W) is ignited. A first welding voltage signal (U1) and a second welding voltage signal (U2) are detected in the welding circuit. The second welding voltage signal (U2) is detected closer to the arc (LB) than the first welding voltage signal (U1). The detected welding voltage signals are transmitted to the control unit (7), and the control unit (7) uses at least one of the welding voltage signals to determine the parameters for controlling or regulating the welding process. The control parameters are obtained by the control unit (7) to control the welding current source (8). The control unit (7) ignores the first welding voltage signal (U1) and uses the second welding voltage signal (U2) to obtain the control parameters in the normal operation mode. The control unit (7) identifies the fault state in the second welding voltage signal (U2) according to the second welding voltage signal (U2) and switches to the emergency operation mode without interrupting the welding process when the fault state is identified. In the emergency operation mode, the control unit (7) ignores the second welding voltage signal (U2) and uses the first welding voltage signal (U1) to obtain the control parameters.

13. The method according to claim 12, characterized in that, If a fault condition is detected, switch to emergency operation mode within 100μs.

14. The method according to claim 12 or 13, characterized in that, The fault state in the second welding voltage signal (U2) is identified based on the welding circuit model stored in the control unit (7).

15. The method according to claim 14, characterized in that, The welding circuit model includes at least one model of the welding line (9), wherein the model of the welding line (9) includes at least one ohmic resistor (R1, R2) and at least one inductor (L1, L2).

16. The method according to claim 14, characterized in that, The model parameters of the welding circuit model are adapted to the welding circuit of the actual constructed welding device (1).

17. The method according to claim 12 or 13, characterized in that, A measuring voltage (UM) is applied to the welding circuit by means of an additional measuring voltage source (14), and the control unit (7) identifies the fault state in the second welding voltage signal (U2) according to the measuring voltage (UM), wherein the measuring voltage source (14) is connected to the welding circuit and polarity is set on the measuring voltage source (14).

18. The method according to claim 17, characterized in that, The measuring voltage source (14) is connected to the welding circuit via a high-resistance ground and / or through a known ohmic resistor (RM).

19. The method according to claim 17, characterized in that, The electrode polarity of the measuring voltage source (14) is opposite to that of the welding current source (8).

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