Electric arc welding system and method for operating an electric arc welding system

Abstract

The invention relates to an electric arc welding system (1) for joining metal workpieces (4, 5), wherein a hand-held welding torch (3) having a welding electrode (10) and having a measuring device is provided. The measuring device has multiple sensors (15a to 15d, 27a to 27d) which can be arranged at a distance from one another on a workpiece (4) and by means of which the signals occurring on a workpiece (4), preferably in the vicinity of a weld seam (6), during the welding process can be captured. The measuring device also has an evaluation device (16) which is coupled to the sensors (15a to 15d, 27a to 27d) for signal transmission, and a modulation-signal-generating device is provided which generates targeted modulated signals during the welding process. The evaluation device (16) is able to identify a modulated signal and to determine the arc position (11) and / or the welding speed on the basis of the time interval between two modulated signals.

Description

[0001] Description

[0002] Electric arc welding system and method for operating an electric

[0003] arc welding system

[0004] The invention relates to an electric arc welding system and a method for operating such an electric arc welding system.

[0005] Electric arc welding systems for joining metallic workpieces using a handheld welding torch with a welding electrode to generate an arc during the welding process, and methods for operating such arc welding systems, are generally known. In particular, manual arc welding systems with stick electrodes are well known. Furthermore, metal inert gas (MIG) welding systems, metal active gas (MAG) welding systems, tungsten inert gas (TIG) welding systems, and plasma welding systems are also well known. Modern welding machines, especially in the MIG / MAG and TIG welding sectors, increasingly rely on pulse technologies, as this allows for significantly higher-quality welding results while simultaneously preventing spatter contamination.

[0006] In commonly used automated welding systems with welding robots, particularly in series production, the movements of the welding head, including path and speed, as well as other welding parameters, are programmed to ensure consistently high-quality welds. In manual welding processes, where a welder moves the welding head along the weld seam at a subjectively chosen speed, the quality of the weld depends largely on the welder's skill and experience. This can result in inconsistent weld quality, especially for safety-critical welds, and can lead to unsatisfactory results. The lack of process stability also necessitates extensive weld inspections, particularly in manual welding.Since it is no longer possible to determine the speed at which a manual welding process was carried out, the actual energy applied cannot be determined during a subsequent weld inspection, which makes it extremely difficult to determine non-destructively whether the workpieces were sufficiently melted.

[0007] Furthermore, a welding device is known as an arc welding device (WO 2006 / 042572 A1) with a welding head for delivering welding energy to the workpieces to be welded and with sensor means for sensing the position and / or changes in position, and thus the speed, of the welding head, wherein at least one characteristic parameter of the welding process can be controlled and regulated as a function of the sensed position and / or change in position. The welding head should be controllable by a welding robot or manually. Specifically, mechanical sensors are presented as the sensors of the sensor means for detecting rotations and / or translations of the welding head, in which the current position of media that can be displaced by movement is electrically scanned at offset points within a sensor housing. Such sensors can be arranged on the hand or arm of a welder or on the welding head.The position or change in position of the welding head can only be determined relatively imprecisely with such sensors. However, for precise control processes and documentation purposes, it is not the position or change in position of the welding head that is relevant, but rather an accurate measurement of the current position and speed of the arc or weld pool and the welding tip. In addition to the measurement inaccuracies of the mechanical sensors used here, a further measurement inaccuracy regarding the position of the arc is introduced due to the considerable distance between the sensor points and the arc.

[0008] Furthermore, an arc welding system is known (US RE 45,398 E) as a manual arc welding system, which includes a measuring device for measuring the welding speed as the speed of the arc position during the welding process along a weld seam. The measuring device has vibration sensors that can be fixedly mounted on a workpiece at intervals in the vicinity of a weld seam, each with acoustic coupling for recording structure-borne sound signals, in order to record welding noises generated at the current arc position during the welding process and transmitted through structure-borne sound in the workpiece. The measuring device also includes an evaluation unit. An electric arc welding system can thus determine the position and speed of the current arc position by measuring and evaluating the time-of-flight differences of welding noises transmitted through structure-borne sound in the workpiece.Since the welding noises are generated directly at the arc position, the current arc position and arc speed are measured directly, not the position of the welding head. A method for operating an electric arc manual welding system is known from DE 35 43 681 C2.

[0009] Furthermore, DE 10 2018 009 536 B4 discloses an electric arc welding system and a method for operating such an arc welding system, wherein the arc welding system, as a manual arc welding system, includes a measuring device for measuring the welding speed as the speed of the arc position during the welding process along a weld seam. The measuring device has at least two vibration sensors, which can be fixedly mounted on a workpiece in the vicinity of a weld seam, spaced apart from each other, with acoustic coupling for recording structure-borne sound signals, and thus enable the recording of welding noises generated at the current arc position during the welding process and transmitted through structure-borne sound in the workpiece.The measuring device also includes an evaluation unit to which at least two vibration sensors are connected. This unit analyzes and evaluates the transit-time differences of the welding noise in the workpiece relative to the at least two stationary vibration sensors, allowing the current arc position to be determined. Furthermore, it allows the welding speed to be determined by evaluating the process-related, progressive displacement of the arc position along the weld seam. The evaluation unit then generates an associated, transmittable speed signal, optionally in conjunction with a corresponding current arc position signal.Furthermore, a control device is connected to the output side of the evaluation unit, which has a setpoint adjuster for a predefinable target welding speed, or with which an initial, possibly variable, welding speed can be predefinable as the target welding speed, to which a specific welding voltage or a specific welding current is assigned, whereby control is carried out in such a way that if an actual welding speed signal is smaller than the target welding speed, the...

[0010] The welding voltage or welding current is reduced, and if the actual welding speed signal is greater than the target welding speed, the

[0011] The welding voltage or current is increased, and / or, in welding systems with automatic wire feed, the wire feed rate is also adjustable to ensure a consistent, and in particular, uniform, supply of filler material corresponding to the welding speed. This allows for very good welding results with high weld quality even in manual welding processes.

[0012] In contrast, the object of the invention is to propose an electric arc welding system and a method for operating such an arc welding system, with which the quality of a welded joint with a hand-held welding torch can be further improved and made more flexible.

[0013] This problem is solved using the features of independent patent claims.

[0014] According to a first solution according to the invention as claimed in claim 1, an electric arc welding system for joining metallic workpieces is provided, comprising a handheld welding torch with a welding electrode for generating an arc during the welding process. Furthermore, a measuring device is provided, wherein the measuring device comprises several vibration sensors that can be spaced apart and arranged on a workpiece, with which the welding noises occurring at the current arc position on a workpiece, preferably in the vicinity of a weld seam, and transmitted as structure-borne sound in a workpiece, can be detected as a structure-borne sound signal.The measuring device includes an evaluation unit that is coupled to the vibration sensors for signal transmission. A modulation signal generation unit, preferably formed by a control unit designed as an adjustable welding current source, is provided, which is suitable and configured to generate targeted modulated signals during the welding process. Furthermore, the evaluation unit is suitable and configured to identify a modulated signal and, based on the change in the time interval between two modulated signals detected by different sensors or vibration sensors, to determine the arc position and / or the welding speed.

[0015] The determination of the arc position and / or the welding speed according to the invention, based on the acquisition and analysis of signals, not only enables precise monitoring of the welding process, but also leads to improved weld quality and consistency. This allows for targeted adjustment of the welding process to minimize defects or irregularities and thus improve the quality and consistency of the welds.

[0016] The targeted generation of modulated signals makes it easier to measure and analyze the signals. Furthermore, finely tuned control of the modulated signals allows the welding process to be optimally adapted to different materials, welding conditions, and requirements.

[0017] This combination of precise monitoring and targeted control enables optimal system performance in various working environments and contributes to increased efficiency and improved quality in welding production. For example, the evaluation unit is capable of identifying characteristic signal features using various techniques and algorithms, such as pattern recognition, where the unit searches for specific patterns in the acquired signals that indicate the presence of modulated signals. These patterns can point to specific frequency ranges, amplitude variations, or temporal sequences of signal events that are characteristic of the welding process. Alternatively or additionally, the evaluation unit can also be configured to react to the exceeding of certain threshold values ​​in the acquired signals.For example, if the signal amplitude or frequency rises above a predefined threshold, this can be interpreted as an indication of the presence of a modulated signal. Alternatively or additionally, the evaluation unit can also isolate or filter out specific frequency ranges by applying filters to better identify the characteristic signal features. Furthermore, the evaluation unit can alternatively or additionally use learned or predefined reference signals and compare the acquired signals with them. If similarities are found between the acquired signals and the reference signals, this can serve as an indication of the presence of modulated signals.

[0018] The same applies to a further, alternative solution according to the invention as claimed in claim 2, which claims an electric arc welding system for joining metallic workpieces, in which a hand-held welding torch with a welding electrode for generating an arc during the welding process and a measuring device are provided, wherein the measuring device has at least one vibration sensor with which the welding noises occurring on a workpiece, preferably in the vicinity of a weld seam, during the welding process at the current arc position and transmitted as structure-borne sound in a workpiece can be detected as a structure-borne sound signal, and has at least one voltage and / or current sensor with which the electrical voltages occurring on a workpiece, preferably in the vicinity of a weld seam, during the welding process can be detected as a voltage signal and / or the electrical currents as a current signal.The measuring device includes an evaluation unit that is coupled to the at least one vibration sensor and to the at least one voltage and / or current sensor. Furthermore, a modulation signal generation device, preferably formed by a control device designed as an adjustable welding current source, is provided. This device is suitable and configured to generate targeted modulated signals during the welding process. The evaluation unit is suitable and configured to identify a modulated signal and to determine the arc position and / or the welding speed based on the change in the time interval between two modulated signals detected by the at least one vibration sensor and the at least one voltage and / or current sensor.

[0019] This solution according to the invention exploits the fact that structure-borne sound signals can be very well detected by sensors and are therefore well suited for carrying out the evaluation according to the invention. In a metallic material, such a structure-borne sound signal propagates at a speed of sound which, for example, is around 5100 meters per second for steel. In contrast, an electric field propagates in metallic conductors at almost the speed of light. An identifiable modulation signal is discernible in both the structure-borne sound and the electric field.In an electric arc welding system, where the measuring device has at least one voltage and / or current sensor in addition to at least one vibration sensor, with which the electrical voltages occurring on a workpiece, preferably in the vicinity of a weld seam, during the welding process can be detected as a voltage signal (with a voltage sensor) and / or the electrical currents as a current signal (with a current sensor), the speed can be evaluated particularly easily and unambiguously by the transit time differences between the voltage or current signal (which is detected in principle in real time) and the acoustic signal arriving at the sensor with a delay.

[0020] According to a particularly preferred embodiment, the at least one vibration sensor can function as a combined sensor and simultaneously also as the at least one voltage and / or current sensor, thus being suitable and configured to detect both structure-borne sound signals and voltage and / or current signals. In principle, it would then even be possible to equip a single combined sensor electronically in such a way that it can autonomously detect the time-of-flight difference between the electrical signal and the sound signal and transmit only the difference to the evaluation unit, although according to a particularly preferred embodiment, several spaced-apart combined sensors are arranged on the workpiece.The invention thus makes it possible to determine the distance to an electric arc using only a single combined sensor that detects both structure-borne sound signals and voltage and / or current signals. This can be illustrated by imagining the electric arc on a circle of known circumference around the sensor. With two sensors that detect both structure-borne sound and voltage signals, there are two possible intersection points of this circle; with three or more sensors, there is only one possible position on a given area. With each additional sensor, the accuracy of the position determination improves, similar to a GPS system.

[0021] Alternatively, it is also possible to provide for the at least one vibration sensor and the at least one voltage and / or current sensor to be provided by separate sensors. In this case, for example, several separate vibration sensors and several separate voltage and / or current sensors can be arranged at intervals on the workpiece.

[0022] In principle, all known manual arc welding systems with stick electrodes or as gas metal arc welding systems can be equipped with the measuring device according to the invention. According to a particularly preferred embodiment, the arc welding system is a pulsed welding system with the capability for pulse modulation of the welding process and / or the arc welding system is a manual arc welding system with stick electrodes or a gas metal arc welding system as a metal inert gas welding system (MIG) or as a metal active gas welding system (MAG) or a tungsten inert gas welding system (TIG) or a plasma welding system.

[0023] The arc welding system is preferably a pulsed welding system with the capability of pulse modulation of the welding process. A pulsed welding system is defined as one that uses a pulse function or pulse modulation in its welding process. This pulse function can be implemented in various welding processes such as MIG welding, MAG welding, TIG welding, or plasma welding. The pulse function enables more precise control of the welding process and offers advantages such as reduced heat input and improved weld quality. The term "pulse modulation" in the context of the welding process describes the adjustment or control of the welding parameters during welding. In pulse welding, a base current is used, which is superimposed with peak currents or pulses.These pulses can have different amplitudes, frequencies, and widths, depending on the requirements of the welding process and the desired results.

[0024] Welding noises, as well as electrical voltage and current, are characterized by a specific frequency structure. A regularly repeating frequency structure arises, for example, in an arc welding system where the arc is generated with alternating current, the frequency of which is also recognizable in the welding noise, voltage, and current. Particularly in pulsed welding systems, the pulsed peak currents influence the welding noise in a very characteristic way; the pulsing frequency is clearly audible in the welding noise. By evaluating this frequency structure, the time-of-flight measurement and assignment to individual sensors in the evaluation unit become highly reliable and accurate.Similarly, a modulation signal generation device can be used to modulate the welding voltage or welding current in both AC and DC welding systems in order to generate clearly identifiable signals in both the electrical and acoustic domains.

[0025] According to a particularly preferred embodiment, the modulation signal generation device is therefore suitable and designed to generate modulated signals by at least one of the following measures:

[0026] - by modulating the welding current,

[0027] - by modulating at least one pulse characteristic of the welding current, preferably by manipulating the frequency and / or the pulse width and / or the pulse shape and / or the pulse amplitude of the welding current, in a pulsed welding system,

[0028] - by introducing at least one external signal and / or at least one external disturbance.

[0029] As previously stated, the modulation signal generation device is preferably formed by an adjustable welding power source, which, however, is expressly not limited to current regulation, since modern welding power sources regularly offer a variety of functions and control options that go beyond mere power supply. As already mentioned, modern welding power sources can also control other parameters, such as voltage, wire feed rate (in MIG / MAG welding), gas flow rate, and any other desired parameter.

[0030] In practice, either individual pulse characteristics or combinations of different characteristics can be used to generate specific modulated signals for measuring the welding speed or to selectively influence the welding process in response to the measured speed. The selection of suitable pulse characteristics depends on the requirements of the welding process and the specific objectives of the modulation signal generation. According to a particularly preferred embodiment, a documentation unit consisting of a storage unit and / or a printer unit can be connected to the evaluation unit. This documentation unit is suitable and configured to document, store, and / or print the determined arc position, welding speed, and / or the position of potential disturbances along the weld seam.The documentation includes, for example, the recording of timestamps in conjunction with the determined speed and position data to enable precise analysis and tracking. Documenting this data allows for a detailed analysis of the welding process as well as the precise identification of problem areas and their causes. Knowing the exact location of specific events during the welding process allows any necessary additional investigations, such as X-ray inspections or rework, to be limited to these areas of the weld, thus avoiding the need to examine the entire weld in safety-critical applications. Furthermore, the precise documentation of the actual speed in conjunction with all other welding parameters allows for subsequent verification that sufficient energy was applied at all points along the weld to adequately melt the workpieces.This is particularly advantageous when the root of the weld is located in an area that is no longer accessible for subsequent inspection, such as in the case of welding on a pipeline.

[0031] According to a further particularly advantageous embodiment, a display device and / or an assistance device for the welder is connected to the evaluation unit, preferably with an optical and / or acoustic and / or haptic sensor device for signaling deviations from predefined target welding parameters. Advantageously, this allows, for example, a welder to be directly informed of deviations from predefined target welding parameters during the welding process, for instance by optical and / or acoustic and / or haptic signals, and to be prompted to comply with them. A haptic signal can be generated, for example, by the vibration of the welding head. An optical signal can also be, in particular, a message or display projected onto a lens of the welding helmet.This would be a particularly elegant method of signaling, using the visor of the protective helmet to display information or a message directly in the field of vision, similar to a head-up display.

[0032] The vibration sensors required for the measurement can, for example, be attached to a workpiece using acoustic coupling. Since a ground wire must also be connected to each workpiece for the electric arc welding system, an acoustic coupling device of a vibration sensor can advantageously be designed to simultaneously connect the ground wire, allowing both operations to be performed in a single step. With suitable measuring technology, the welding current flowing through the ground wire and / or the associated voltage can also be directly measured without requiring a separate measuring connection.

[0033] According to a further particularly preferred embodiment, the evaluation device is coupled, preferably on the output side, with a control device of the arc welding system, preferably formed by a controllable welding power source, which enables a particularly advantageous and flexible control of the welding process:

[0034] According to a particularly preferred embodiment, especially to increase metrological and design flexibility, the control device of the arc welding system may have a setpoint adjuster for a predefinable target welding speed, to which a specific welding voltage or welding current is assigned, wherein control is carried out such that if the actual welding speed signal is less than the target welding speed, the

[0035] The welding voltage or welding current is reduced, and if the actual welding speed signal is greater than the target welding speed, the

[0036] Welding voltage or welding current is increased, and / or that, in the case of pulsed welding systems, the control device changes the pulse parameters in such a way that the average energy input is increased when the actual welding speed signal is greater than the target welding speed and decreased when the actual welding speed signal is less than the target welding speed, and / or that, in the case of welding systems with automatic welding wire feed, the control device adjusts the wire feed in such a way that a feed of filler material corresponding to the welding speed, in particular a uniform one, takes place.

[0037] The control device can also be used in an advantageous dual function not only for controlling the pulsed welding current, but also be suitable and designed to not only generate the basic pulses in a pulsed welding process, but also to vary the pulse characteristics, such as the frequency or the pulse shape, preferably with regard to the length and / or geometry of the pulses, at regular intervals for signal generation, for example by adjusting individual pulses, adding additional pulses or removing existing pulses.Furthermore, a second pulse signal can be superimposed on the pulsed welding current, which consists of a constant base current with a superimposed pulsed peak current. For example, the base pulse could have a frequency of one hundred hertz, and every hundredth pulse could be superimposed with another, high-frequency signal at ten kilohertz. This second pulse signal (which in the described case would consist of a sequence of 100 pulses) could, in turn, have a gap of two pulses in the middle, making this signal clearly identifiable with very high resolution. Given the expected small differences in propagation time, sufficiently high accuracies could be achieved to reach measurement accuracy in the millimeter range.

[0038] Furthermore, the evaluation device can be suitable and designed to detect a pause by the absence of movement of the arc and to transmit the signal or command to the adjustable welding power source to automatically activate an end crater filling program with which the weld seam is completely filled at the end of the welding process.

[0039] Previously, for example, in connection with vibration sensors, a uniform speed of sound within the workpiece was always assumed, as this leads to sufficiently accurate results in the practical implementation of the invention. Under real-world conditions, however, a workpiece heats up considerably during welding, but not uniformly. Unlike gases, the speed of sound in solids such as steel decreases with increasing temperature. In steel, this decrease is approximately 1% per 55 Kelvin. During the welding process, the workpiece is heated locally at the edge of the weld pool to approximately 1500°C. Transversely to the weld seam, the temperature decreases across the so-called heat-affected zone to a few hundred degrees, depending on the component thickness and the amount of energy applied; the energy is then distributed throughout the rest of the workpiece.The movement of the welding torch creates a longitudinal heat trail, as the workpiece has significantly higher temperatures in the already welded area than in the unwelded area. Generally speaking, due to the negative temperature dependence of the speed of sound on temperature, sensors located closer to the starting point of the welding process receive signals later and later as the welding process progresses, thus distorting the measurement result. In principle, the evaluation unit would therefore conclude that the welding process is moving faster than it actually is, even though the distance between the sensors is increasing. The propagation times of the electric field are not measurably affected. To avoid this, it would theoretically be possible to measure and incorporate the temperatures in real time, but the measurement effort required would be immense.A simpler solution would instead be to determine correction factors and store them in the evaluation unit. Accordingly, a particularly preferred embodiment provides that correction factors, preferably to compensate for the dependence of the speed of sound on the workpiece temperature, are stored in the evaluation unit, by means of which the measurement result of the at least one vibration sensor can be corrected as a function of the distance of the at least one vibration sensor to the current position of the welding torch.Specifically, thermographic images of welding processes can be used for this purpose, from which actual temperature distributions are determined and the necessary correction factors are derived depending on selected parameters, in particular the duration of the welding process and / or the alloy of the workpiece and / or the workpiece thickness and / or the workpiece dimensions and / or the type and / or the geometry of the weld seam, and stored in the evaluation unit. In principle, corresponding correction factors could also be generated using artificial intelligence (AI), but this requires extensive welding tests.

[0040] Another, additional, or alternative configuration involves the inclusion of computational models in the evaluation unit for temperature compensation during signal acquisition during a welding process. These models are used in welding technology to estimate the cooling times of the material in the heat-affected zone within the metallurgically important range for steel materials between 800°C and 500°C (for example, so-called t8 / 5 models). The evaluation unit is designed and configured to estimate, based on the cooling times in conjunction with the determined welding speeds, which workpiece areas the signal has passed through at what temperature to reach the respective sensor. For this purpose, known t8 / 5 models would be extended to also consider further cooling below the 500°C threshold.Knowing the cooling times in conjunction with the previously determined welding speeds allows us to estimate which workpiece areas, at what temperature, the respective sound signal passed through to reach the respective sensor. Accordingly, the evaluation unit can correct the determined transit times and thus significantly increase the measurement accuracy.

[0041] Furthermore, especially in a design using voltage and / or current sensors, it would be conceivable to use precise knowledge of the signal generation time for temperature compensation, allowing not only consideration of signal propagation time differences but also of changes in the absolute propagation times of the signals. Due to the reduction in the speed of sound in warmer areas of the workpiece, the absolute propagation time of the sound signal increases in these areas. Since it can be assumed that sensors positioned, for example, in the direction of movement receive signals through material that is not significantly heated, a decrease in propagation times compared to these sensors is solely attributable to movement of the welding head. In contrast, an increase in propagation times compared to sensors past which the weld spot has already moved is due to both movement and temperature increase.However, since the actual distance between the sensors does not change during the welding process, any increase in the total cumulative runtimes for all sensors is due to a temperature increase and can therefore be taken into account by the evaluation unit.

[0042] The object of the invention is further achieved by means of the methods for operating an electric arc welding system. The advantages arising here are identical to those of the arc welding system described above, so reference is made to the previously stated explanations to avoid repetition.

[0043] An exemplary embodiment of an electric arc welding system according to the invention is explained in more detail with reference to a drawing.

[0044] The single figure shows, in a highly schematic form, a manual arc welding system 1 as a metal inert gas welding system with a welding torch 3 guided by a welder's hand 2.

[0045] In the present schematic joining example, a vertically oriented metal web 5 is to be joined to a workpiece 4, a metal plate, by means of a weld seam 6. For this purpose, an electrode 10 protruding from the welding torch 3 (the electrode is formed by the automatically fed welding wire in MIG / MAG processes) is supplied with welding energy via a control device 8 formed by an adjustable welding power source, with which, for example, a welding voltage and / or a welding current can be regulated, and via a (schematically represented) line 9. This generates an arc 11 at the tip of the electrode 10 during the welding process, melting the edges 12 of the weld seam 6. The weld seam 6 is produced by the manual movement of the welding torch 3, or rather the electrode tip, and thus the arc 11, along the edges 12.An essential parameter for producing a uniform weld seam 6 with high quality of the weld joint is a uniform welding speed with welding parameters adapted to it, i.e. a uniform hand guidance of the electrode 10 at a uniform speed along the edges 12 of the weld seam 6.

[0046] Welding noises are generated during the welding process. These noises are shown schematically and exemplarily in diagram 13 over time t, with noise peaks 14 occurring at equal time intervals. These peaks can be attributed, for example, to the operation of the welding torch 3 with alternating voltage or to modulation of the welding voltage or welding current. The welding noise 14 generated at the arc position 11 during the welding process is used, as explained below, to determine the welding speed of the hand-held electrode 10 along the weld seam 6.

[0047] For this purpose, four vibration sensors 15a, 15b, 15c, 15d, designed here as microphones, are attached to the workpiece 4, which is exemplified here as a rectangular metal plate, in the corner areas with acoustic coupling. The welding noise generated during the welding process is transmitted in the form of structure-borne sound signals within the workpiece 4 to the vibration sensors 15a to 15d. The structure-borne sound signals received by the individual vibration sensors 15a to 15d are fed to an evaluation unit 16 via cables, so that the recorded structure-borne sound signals can be assigned to individual vibration sensors 15a to 15d.Due to the varying distances of the vibration sensors 15a to 15d from the current arc position 11, differences in the transit times of the structure-borne sound signals arise. These signals are recorded in the evaluation unit 16 and, particularly during pre-calibration, allow the current position of the arc to be determined. Furthermore, when the arc position 11 is moved manually, the transit times of the recorded structure-borne sound signals to the vibration sensors 15a to 15d also change. These changes in transit time differences can be evaluated in the evaluation unit 16 to determine a change in the position of the arc 11 and, in conjunction with a recorded welding time, processed into a velocity signal. This velocity signal is then available at the output of the evaluation unit 16 for various further applications.

[0048] As an example, the output speed signal is fed via line 17 to a display device 18 in the form of a screen, on which the welding speed v is displayed analogously and / or digitally, optionally in conjunction with the display of the current arc position. As an example, the output speed signal is also fed via line 19 to an assistance unit 20, which can support the welder in his welding work and to which optical and / or acoustic and / or haptic sensor devices are connected on the output side for signaling deviations from predefined target welding parameters, in particular deviations from a target welding speed.

[0049] Furthermore, a speed signal output by the evaluation unit 16 is supplied to a documentation unit 22 by means of a line 21, which here consists of a storage unit 23 and a printer unit 24 connected to it, with which documentation, here of weld quality, can be carried out in the usual way.

[0050] The evaluation unit 16 also allows for further analysis of the structure-borne sound signals or welding noises 14 recorded by the vibration sensors 15a to 15d, enabling the detection, display, and documentation of specific welding events. Such events, which can particularly affect weld quality, include, for example, temporary interruptions of the welding process, the formation of voids, and / or lateral arc breakout with uneven melting of the corresponding weld edges. These analyses can be performed, in particular, by comparing and matching the current noise patterns to previous noise patterns, especially using self-learning units.

[0051] Furthermore, the speed signal provided at the evaluation unit is supplied to the control unit 8 via a line 25, optionally together with a current, associated arc position signal. A target welding speed can be set at the control unit 8 using a setpoint adjuster 7, which is only schematically indicated here. Alternatively, an initial welding speed can be specified as the target welding speed by the evaluation unit 16, to which a specific welding voltage or welding current is assigned.The control unit 8 can intervene, for example, by reducing the welding voltage or current if the detected actual welding speed is lower than the target welding speed, and by increasing the welding voltage or current, as well as any wire feed, if the detected actual welding speed is higher than the target welding speed, in order to ensure the most uniform possible melting of the edges of the weld seam 6. In the case of pulsed welding processes, the control unit 8 can also adjust the pulse parameters depending on the actual welding speed. The vibration sensor 15a is acoustically coupled to the workpiece 4 by means of a coupling device (not shown in detail), such as a clamp or a magnetic holder for steel materials, which also provides a connection for a ground wire 26 to the workpiece 4.

[0052] The embodiment described above essentially corresponds to that of DE 10 2018 009 536 B4, which, according to a particularly preferred embodiment of the present invention, is extended by way of example by an additional functionality, which of course can also be used on its own and according to which the vibration sensors 15a to 15d simultaneously also form a voltage and / or current sensor 27a to 27d, which is suitable and designed to detect voltage and / or current signals in addition to the structure-borne sound signals.

[0053] The voltage and / or current sensors 27a to 27d can detect the electrical voltages occurring at the workpiece 4 during the welding process at the current arc position as a voltage signal and / or the flowing currents and transmit them to the evaluation unit 16.

[0054] The evaluation unit 16 is also designed in such a way that it is able to identify a modulated signal generated by means of a modulation signal generation device and to determine the arc position and / or the welding speed based on the change in the time interval between two modulated signals from different sensors.

[0055] The modulated signals are preferably generated by the control device 8, for example by modulating the welding current and / or by modulating the frequency of the welding current.

[0056] In this embodiment according to the invention, the ability of the evaluation unit to detect targeted modulated signals is thus utilized. In other words, deliberately modulated signals are generated during the otherwise uniform welding process, which can be detected as sound, voltage, and / or current signals, but at different times. Reference numeral list

[0057] 1 manual arc welding machine

[0058] 2 Hand

[0059] 3 welding torches

[0060] 4 workpieces

[0061] 5 metal bridge

[0062] 6 weld seam

[0063] 7 Setpoint adjusters

[0064] 8 Welding power source / control unit

[0065] 9 Management

[0066] 10 electrode

[0067] 11 arcs

[0068] 12 edge

[0069] 13 Diagram

[0070] 14 noise peaks

[0071] 15a Vibration sensor

[0072] 15b Vibration sensor

[0073] 15c vibration sensor

[0074] 15d vibration sensor

[0075] 16 Evaluation unit

[0076] 17 Management

[0077] 18 Display device

[0078] 19 Management

[0079] 20 Assistance Unit

[0080] 21 Management

[0081] 22 Documentation facility

[0082] 23 storage units

[0083] 24 printer units

[0084] 25 Management

[0085] 26 Ground wire

[0086] 27a Voltage and / or current sensor

[0087] 27b Voltage and / or current sensor

[0088] 27c Voltage and / or current sensor

[0089] 27d Voltage and / or current sensor

Claims

Patent claims 1. Electric arc welding system (1) for joining metallic workpieces (4, 5), wherein a hand-held welding torch (3) with a welding electrode (10) is provided for generating an arc during the welding process, wherein a measuring device is provided, wherein the measuring device has several vibration sensors (15a to 15d) that can be arranged at intervals on a workpiece (4), with which the welding noises (14) occurring on a workpiece (4), preferably in the vicinity of a weld seam (6), during the welding process at the current arc position (11) and transmitted as structure-borne sound in a workpiece (4) can be detected as a structure-borne sound signal, wherein the measuring device has an evaluation device (16) that is coupled to the vibration sensors (15a to 15d) for signal transmission, wherein a modulation signal generation device, preferably formed by a control device (8) designed as an adjustable welding current source, is provided.which is suitable and designed to generate targeted modulated signals during the welding process, wherein the evaluation device (16) is suitable and designed to identify a modulated signal and to determine the arc position (11) and / or the welding speed based on the change in the time interval between two modulated signals detected by different vibration sensors (15a to 15d).

2. Electric arc welding system (1) for joining metallic workpieces (4, 5), wherein a handheld welding torch (3) with a welding electrode (10) is provided for generating an arc during the welding process, wherein a measuring device is provided, wherein the measuring device has at least one vibration sensor (15a to 15d) with which the welding noises (14) occurring at a workpiece (4), preferably in the vicinity of a weld seam (6), during the welding process at the current arc position (11) and transmitted as structure-borne sound in a workpiece (4) can be detected as a structure-borne sound signal, wherein the measuring device has an evaluation device (16) which is coupled to the at least one vibration sensor (15a to 15d) for signal transmission, wherein the measuring device has at least one voltage and / or current sensor (27a to 27d) with which the welding noises (14) occurring at a workpiece (4), preferably in the vicinity of a weld seam (6), can be detected as a structure-borne sound signal.The electrical voltages occurring during the welding process can be detected as a voltage signal and / or the electrical currents as a current signal, wherein the at least one voltage and / or current sensor (27a to 27d) is coupled to the evaluation unit (16) for signal transmission, wherein a modulation signal generation device, preferably formed by a control device (8) designed as an adjustable welding current source, is provided, which is suitable and configured to generate targeted modulated signals during the welding process, wherein the evaluation unit (16) is suitable and configured to identify a modulated signal and to determine the arc position (11) and / or the welding speed based on the change in the time interval between two modulated signals detected by the at least one vibration sensor (15a to 15d) and the at least one voltage and / or current sensor (27a to 27d).

3. Electric arc welding system according to claim 2, characterized in that the at least one vibration sensor (15a to 15d) as a combined sensor also simultaneously the at least one voltage and / or current sensor (27a to 27d) is trained and is thus suitable and trained to detect both structure-borne sound signals and voltage and / or current signals.

4. Electric arc welding system according to claim 2, characterized in that the at least one vibration sensor (15a to 15d) and the at least one voltage and / or current sensor (27a to 27d) are formed by separate sensors.

5. Electric arc welding system according to one of the preceding claims, characterized in that the arc welding system (1) is a pulsed welding system with the capability for pulse modulation of the welding process and / or that the arc welding system (1) is a manual welding system with stick electrodes or a metal inert gas welding system as a metal inert gas welding system (MIG) or as a metal active gas welding system (MAG) or a tungsten inert gas welding system (TIG) or a plasma welding system.

6. Electric arc welding system according to one of the preceding claims, characterized in that the modulation signal generation device is suitable and configured to generate modulated signals by at least one of the following measures: - by modulating the welding current, - by modulating at least one pulse characteristic of the welding current, preferably by manipulating the frequency and / or the pulse width and / or the pulse shape and / or the pulse amplitude of the welding current, in a pulsed welding system, - by introducing at least one external signal and / or at least one external disturbance.

7. Electric arc welding system according to one of the preceding claims, characterized in that a documentation device (22) consisting of a storage unit (23) and / or a printer unit (24) is connected to the evaluation device (16), which is suitable and designed to document and / or store and / or print the determined arc position and / or the determined welding speed (v) and / or the position of potential disturbances along the weld seam (6).

8. Electric arc welding system according to one of the preceding claims, characterized in that a display device (18) and / or an assistance device (20) for the welder, preferably with an optical and / or acoustic and / or haptic sensor device for signaling deviations from predetermined target welding parameters, is connected to the evaluation device (16).

9. Electric arc welding system according to one of the preceding claims, characterized in that the evaluation device (16), preferably on the output side, is coupled with a control device (8) of the arc welding system (1), preferably formed by a controllable welding current source, with which predetermined welding process parameters of the arc welding system, preferably for controlling the arc and / or the wire feed speed and / or the gas composition, can be controlled.

10. Electric arc welding system according to claim 9, characterized in that the control device (8) has a setpoint adjuster for a predefinable target welding speed, to which a specific welding voltage or a specific welding current is assigned, wherein control is carried out such that, in the case of an actual welding speed signal that is less than the target welding speed, Welding speed reduces the welding voltage or welding current and, in the case of an actual welding speed signal, is greater than the target value. welding speed, the welding voltage or the welding current is increased and / or that the control device (8) in the case of pulsed welding systems changes the pulse parameters in such a way that the average energy input is increased when the actual welding speed signal is greater than the target welding speed and is decreased when the actual welding speed signal is less than the target welding speed and / or that the control device (8) in welding systems with automatic feed of welding wire adjusts a wire feed in such a way that a feed of filler material corresponding to the welding speed, in particular a uniform one, takes place.

11. Electric arc welding system according to claim 9 or 10, characterized in that the control device (8) is suitable and designed to vary the pulse characteristics, preferably the frequency and / or the pulse shape, for generating modulation signals in a pulsed welding process.

12. Electric arc welding system according to one of claims 9 to 11, characterized in that the evaluation device (16) is suitable and designed to detect the stopping process at the end of the weld seam by the absence of movement of the arc and to transmit the signal to the controllable welding power source to automatically activate an end crater filling program with which the weld seam is completely filled at the end of the welding process.

13. Electric arc welding system according to one of the preceding claims, characterized in that correction factors, preferably for compensating for the dependence of the speed of sound on the workpiece temperature, are stored in the evaluation device (16), by means of which the measurement result of the sensors (15a to 15d, 27a to 27d) can be corrected as a function of the distance of the sensors (15a to 15d, 27a to 27d) to the current position of the welding torch (3).

14. Electric arc welding system according to one of the preceding claims, characterized in that the evaluation unit (16) contains computational models for temperature compensation when acquiring signals during a welding process, which also take into account cooling below the 500°C limit, wherein the evaluation unit is suitable and designed to estimate, based on the cooling times in conjunction with the determined welding speeds, which workpiece areas at which temperature the signal has passed through in order to arrive at the respective sensor.

15. Electric arc welding system according to one of the preceding claims, characterized in that the evaluation device (16) is suitable and designed to take into account the change in the absolute transit times of the signals for temperature compensation.

16. Method for operating an electric arc welding system for joining metallic workpieces, in particular by means of an electric arc welding system according to any one of the preceding claims 1 to 15, wherein a hand-held welding torch (3) with a welding electrode (10) is provided for generating an arc during the welding process, wherein a measuring device is provided, wherein the measuring device comprises several vibration sensors (15a to 15d) that can be arranged at intervals on a workpiece (4), with which the welding noises (14) occurring on a workpiece (4), preferably in the vicinity of a weld seam (6), during the welding process at the current arc position (11) and transmitted as structure-borne sound in a workpiece (4) are detected as a structure-borne sound signal, wherein the measuring device comprises an evaluation device (16) that is coupled to the vibration sensors (15a to 15d) for signal transmission, wherein a modulation signal generation device, preferably formed by a control device (8) designed as an adjustable welding current source, is provided, which generates targeted modulated signals during the welding process, wherein the evaluation device (16) identifies a modulated signal and, based on the change in the time interval between two modulated signals,which are detected by various vibration sensors (15a to 15d), determine the arc position (11) and / or the welding speed.

17. Method for operating an electric arc welding system for joining metallic workpieces, in particular by means of an electric arc welding system according to any one of the preceding claims 1 to 15, wherein a hand-held welding torch (3) with a welding electrode (10) is provided for generating an arc during the welding process, wherein a measuring device is provided, wherein the measuring device has at least one vibration sensor (15a to 15d) with which the welding noises (14) occurring at a workpiece (4), preferably in the vicinity of a weld seam (6), during the welding process at the current arc position (11) and transmitted as structure-borne sound in a workpiece (4) are detected as a structure-borne sound signal, wherein the measuring device has an evaluation device (16) which is coupled to the at least one vibration sensor (15a to 15d) for signal transmission. wherein the measuring device comprises at least one voltage and / or current sensor (27a to 27d) with which the electrical voltages occurring on a workpiece (4), preferably in the vicinity of a weld seam (6), during the welding process are detected as a voltage signal and / or the electrical currents as a current signal, wherein the at least one voltage and / or current sensor (27a to 27d) is coupled to the evaluation device (16) for signal transmission, wherein a modulation signal generation device, preferably formed by a control device (8) designed as an adjustable welding current source, is provided which generates targeted modulated signals during the welding process, wherein the evaluation device (16) identifies a modulated signal and, based on the change in the time interval between two modulated signals,which are detected by the at least one vibration sensor (15a to 15d) and by the at least one voltage and / or current sensor (27a to 27d), which determine the arc position (11) and / or the welding speed.

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