MULTI-PULSE WELDING PROCESS

Description

[0001] The present invention relates to a method for synchronizing at least two pulse welding processes for carrying out a multi-pulse welding process, wherein a pulse welding process consists of welding cycles with a pulse current phase and a base current phase, repeated periodically at a pulse frequency, wherein each pulse welding process is carried out with a welding machine, wherein the welding machines are connected to each other by means of a communication link and synchronization information is sent via the communication link from a sending welding machine to at least one receiving welding machine and this synchronization information is used in the receiving welding machine to synchronize the pulse welding process carried out with the receiving welding machine to the pulse welding process carried out with the sending welding machine.wherein the sending welding device transmits a synchronization pulse to at least one receiving welding device as synchronization information, the synchronization pulse being in a defined temporal relationship to the welding cycle of the pulse welding process of the sending welding device, and the welding cycle of the pulse welding process of the receiving welding device being synchronized to the received synchronization pulse. Furthermore, the invention relates to an arrangement for carrying out a multi-pulse welding process.

[0002] The present invention relates to pulse welding with a consumable or non-consumable welding electrode and a pulsed arc. In this welding process, a base welding current and a higher pulse welding current alternate regularly at a predetermined pulse frequency. During the base welding current phase, the arc burns at low power to keep the weld pool molten. During the pulse welding current phase, a large droplet of welding wire forms as filler material, which is eventually detached and falls into the weld pool. The welding wire can simultaneously serve as a consumable welding electrode, for example in MIG (Metal Inert Gas) or MAG (Metal Active Gas) welding, or it can be fed to an arc burning between a non-consumable welding electrode and the workpiece, for example in TIG (Tungsten Inert Gas) welding.In the case of TIG welding, the welding process is often also referred to as DC pulse or TIG AC. Depending on the wire diameter and the material of the welding wire, the wire feed speed and the pulse frequency in MIG / MAG welding must be selected and adjusted so that a droplet is generated and detached with each current pulse. Wire feed speed and pulse frequency are interdependent. If the wire feed speed and pulse frequency are not appropriately selected, a stable welding process cannot be achieved and / or good weld quality cannot be obtained. Pulse welding reduces and controls the heat input into the workpiece, thus enabling the welding of thinner workpieces. Additionally, pulse welding produces high-quality weld results; for example, it significantly reduces spatter.

[0003] To increase welding performance, multiple pulse welding processes, such as a tandem pulse welding process, are also known, in which at least two pulse welding processes are operated simultaneously. Preferably, at least two welding wires melt into a common weld pool. However, the individual pulse welding processes can also each have their own weld pool. For this, separate welding equipment is required for each pulse welding process, i.e., a power source, a welding torch, and, if necessary, a welding wire feed unit. Each welding unit is used to implement one pulse welding process. Such multiple pulse welding processes are known, for example, from US 2015 / 0343549 A1 (basis for the preamble of claims 1 and 9), US 2008 / 0011728 A1, US 2002 / 0190045 A1, and WO 2014 / 140772 A2.Multi-pulse welding for MIG / MAG can be operated in such a way that the welding processes are started and run independently of each other, meaning that the welding wire feed speed and pulse frequency are set separately for each welding process. With TIG welding, usually only the pulse frequencies are set, although the welding wire feed speed of the filler material could also be adjusted. However, this is more complex for the welder, as the welding parameters must be set accordingly in all welding machines. Furthermore, this offers little to no control over any potential mutual interference from the simultaneously running welding processes, which can reduce weld quality.

[0004] Therefore, a tandem pulse welding process with synchronized welding processes has already become known, in which one welding machine is given a pulse frequency, which the other welding machine follows. Both welding processes are thus synchronized and weld at the same pulse frequency. However, this can lead to problems in MIG / MAG welding if the welding wire of the following welding process is fed at a different wire feed rate than in the other welding process, which is often desirable to increase process stability. Synchronized welding processes are also the goal in TIG welding. However, a lower wire feed rate usually also requires a lower pulse frequency because the power balance of wire feed and welding current must be coordinated.If there is too great a difference between the welding wire feed speed in the leading pulse welding process and in the following pulse welding process, it can happen that the following pulse welding process is operated with too high a pulse frequency (which was adopted from the leading welding process), which may result in an unstable welding process or a poorer welding result (e.g. weld spatter).

[0005] To address this problem, DE 10 2007 016 103 A1 already proposed that the pulse frequency of the trailing pulse welding process in a tandem pulse welding process be set as an integer multiple of the pulse frequency of the leading pulse welding process. The pulse frequencies of the two pulse welding processes should be selected so that the pulse current phases do not overlap. However, it is not explained how the synchronization of the two pulse welding processes can be achieved.

[0006] It is therefore an object of the present invention to provide a method for synchronizing several simultaneously occurring pulse welding processes in a multi-pulse welding process.

[0007] This problem is solved according to the invention with the characterizing features of the independent claims.

[0008] The synchronization pulse enables the receiving welding machine to synchronize its pulse welding process with the pulse welding process in the sending welding machine, ensuring the desired alignment of the two processes. To prevent the two processes from drifting apart, such a synchronization pulse could also be repeated at regular intervals.

[0009] The communication link allows for the simple transmission of synchronization information required for synchronizing the pulse welding processes. This enables automated synchronization without the need for welder intervention or setting welding parameters.

[0010] For a simple implementation of the multiple pulse welding process, the pulse frequency of the pulse welding process of the receiving welding machine can be known in the receiving welding machine or determined from a known welding characteristic curve.

[0011] According to the invention, the pulse frequency of the sending welding machine is additionally transmitted as synchronization information. In the receiving welding machine, the pulse frequency to be set by the receiving welding machine is determined from the received pulse frequency of the sending welding machine using a known frequency divider. This makes it possible to synchronize the pulse welding process in the receiving welding machine with the pulse welding process in the sending welding machine.

[0012] A further embodiment of the invention arises when the transmitting welding machine continuously sends synchronization pulses with the pulse frequency of the transmitting welding machine to the receiving welding machine as synchronization information, at least during synchronization. The receiving welding machine determines the pulse frequency of the transmitting welding machine from the period of the received synchronization pulses and uses a known frequency divider to determine the pulse frequency to be set in the receiving welding machine. This makes it possible to synchronize the pulse welding process in the receiving welding machine with the pulse welding process in the transmitting welding machine.

[0013] Particularly advantageously, the frequency divider in the receiving welding machine is determined from a known welding characteristic curve, and the pulse frequency to be set by the receiving welding machine is determined from the pulse frequency of the sending welding machine and the frequency divider. Preferably, a pulse frequency required for the pulse welding process is determined from the welding characteristic curve based on a set welding wire feed speed of the pulse welding process of the receiving welding machine. The frequency divider is then determined from the required pulse frequency and the pulse frequency received from the sending welding machine. This allows the pulse frequency of the receiving welding machine to be optimally set, taking into account a stored welding characteristic curve, thus considering the welding process when determining the pulse frequency.

[0014] For multi-pulse welding processes, it can be advantageous if the synchronization pulse is sent with a predetermined phase shift at the beginning of the welding cycle in the sending welding machine and / or if the welding cycle in the receiving welding machine is started with a predetermined phase shift after receiving the synchronization pulse. This ensures the desired phase alignment of the pulse welding processes.

[0015] The present invention is described below with reference to the Figuren 1 bis 7 In more detail, the invention is explained, and exemplary, schematic, and non-restrictive embodiments are shown. This includes showing Fig.1 an arrangement for carrying out a multi-pulse welding process, Fig.2 the welding cycles in a multi-pulse welding process, Fig.3 the synchronization of the pulse welding processes by means of a communication link between the welding devices involved, Fig.4 synchronization using synchronization pulses, Fig.5 a possible welding characteristic curve of an impulse welding process, Fig.6 Pulse welding processes with intermediate pulses and Fig.7 a switching of the synchronization during welding.

[0016] The invention is explained below using a tandem pulse welding process, i.e., with two pulse welding processes, as an example of a multi-pulse welding process. However, it is of course conceivable to extend the following explanations to a multi-pulse welding process with more than two pulse welding processes. A multi-pulse welding process is characterized in particular by the fact that at least two pulse welding processes run simultaneously; consequently, in a tandem pulse welding process, two pulse welding processes run simultaneously. The multiple pulse welding processes can all operate in the same weld pool, but different pulse welding processes can also operate in partially separate weld pools.

[0017] In Fig.1 A possible configuration for a tandem pulse welding process is shown schematically. Two separate welding machines 1a, 1b are provided, each with a power source 2a, 2b, a welding wire feeder 3a, 3b (in TIG welding, the welding wire feeder 3a, 3b is also used without a welding wire feeder 3a, 3b), and a welding torch 4a, 4b. The power sources 2a, 2b each provide the required welding voltage, which is applied to the welding wire 5a, 5b, the consumable welding electrode of the welding process. For this purpose, a contact sleeve can be provided in one of the welding torches 4a, 4b, to which the welding voltage is applied, e.g., via a welding cable 6a, 6b, and which is contacted by the welding wire 5a, 5b. Alternatively, a welding torch 4a, 4b with a non-consumable welding electrode can be used, to which the welding voltage is applied via the welding cable 6a, 6b.In this case, the welding wire 5a, 5b is fed into the arc burning in the light bed between the non-consumable welding electrode and the material.

[0018] This ensures that a specific welding current flows through the welding electrode, for which, of course, a [missing word] is required. Fig.1 A second welding line (not shown) is provided for contacting the workpiece. The welding wire 5a, 5b is fed by the welding wire feed unit 3a, 3b at a specific feed rate. The welding wire feed unit 3a, 3b can be integrated into the welding machine 1a, 1b, or it can be a separate unit. The welding wire 5a, 5b and the welding line 6a, 6b of a welding machine 1a, 1b, and optionally other lines between the power source 2a, 2b and the welding torch 4a, 4b (for example, a control line or a coolant line), can also be routed in a common hose assembly, or multiple hose assemblies. The hose assembly can be connected to the welding torch 4a, 4b and to the power source 2a, 2b via suitable couplings. A welding machine 1a, 1b also includes a control unit 7a, 7b which controls and monitors the pulse welding process.For this purpose, the welding parameters required in the control unit 7a, 7b, such as the pulse frequency, the welding wire feed speed, the welding current values, the pulse current duration, the base current duration, etc., are predefined or adjustable. An input / output unit 8a, 8b may also be provided for entering or displaying certain welding parameters or a welding status. Such a welding machine 1a, 1b is, of course, well known and does not need to be described in detail here. For a multi-pulse welding process with more than two pulse welding processes, a correspondingly larger number of welding machines 1a, 1b are naturally provided. Several welding machines 1a, 1b of a multi-pulse welding process, possibly also with the associated welding wire feed units 3a, 3b, can also be arranged in a common housing.

[0019] To implement a tandem welding process, the two welding torches 4a, 4b are arranged relative to each other in the illustrated embodiment, so that they work in a common weld pool 11 on a workpiece 10. This arrangement relative to each other can be fixed, for example, by arranging both welding torches 4a, 4b on a welding robot 12, which guides both welding torches 4a, 4b (as in Fig.1 (indicated). However, the arrangement can also be variable, for example, by having each welding torch 4a, 4b guided by a welding robot 12. It is also irrelevant whether the welding torches 4a, 4b are arranged one behind the other, side by side, or otherwise offset from each other with respect to the welding direction. Likewise, it is irrelevant whether a joining weld, a surfacing weld, or any other welding process is carried out using an impulse welding process. These statements naturally apply analogously to a multi-impulse welding process with more than two impulse welding processes.

[0020] Based on the Fig.2 The well-known pulse welding process is explained using the profile of the welding current IS over time t. During pulse welding, a base current ISG and a correspondingly higher pulse current ISI alternate periodically at a predetermined pulse frequency fD. The pulse frequency fD is naturally the reciprocal of the period tD of a welding cycle SZ, consisting of a base current phase with the base current ISG and a pulse current phase with the pulse current ISI. During the pulse current phase, a weld droplet is to be deposited into the respective weld pool 11. During a welding operation, the pulse frequency fD and / or the value of the base current ISG or the pulse current ISI can also change.

[0021] The time courses of the welding currents IS1, IS2 are shown in Fig.2 This is, of course, an idealized and simplified representation. In reality, certain current ramps will naturally occur at the edges. It is also often intended that the welding current IS decreases in steps, or with a different current profile, during the transition from the pulse current I SI to the base current I SG, in order to support droplet detachment. Short intermediate current pulses are also often included in the base current phase to increase process stability, as described in more detail below. However, this does not change the period t D of a welding cycle SZ and the resulting pulse frequency f D.

[0022] In a tandem pulse welding process according to the invention, the two pulse welding processes are synchronized by having the pulse frequencies fD1 = 1 / tD1, fD2 = 1 / tD2 of the two pulse welding processes in a specific predetermined relationship to each other, and by having the resulting welding cycles SZ1, SZ2 have a specific predetermined phase relationship to each other. Preferably, one pulse frequency is an integer multiple of the other pulse frequency. This naturally applies analogously to a multi-pulse welding process in which the individual pulse welding processes are synchronized to each other. In the example of the Fig.2 The pulse frequency fD2, for example of the trailing pulse welding process, is twice as high as the pulse frequency fD1, for example of the leading pulse welding process, but the reverse can also be true. Additionally, the welding current profile with the higher pulse frequency fD2 can be shifted in time by a phase shift tP compared to the welding current profile with the lower pulse frequency fD1, meaning that the pulses with pulse current ISI begin at different times. The phase shift can, of course, also be specified as a phase angle relative to the pulse frequency fD1 of the leading pulse welding process.

[0023] Typically, the leading pulse welding process will have the higher pulse frequency fD1, and the trailing pulse welding process will have a lower or the same pulse frequency fD2. In the case of a multi-pulse welding process, there is one leading pulse welding process and several trailing pulse welding processes, whereby, again, the leading pulse welding process preferably has the highest pulse frequency, and the trailing pulse welding processes have lower or the same pulse frequencies. However, the pulse frequencies of the trailing pulse welding processes do not necessarily have to be the same.

[0024] To carry out the described tandem pulse welding process, the respective pulse frequencies fD1 and fD2, as well as any phase shift tP, must be known in both welding machines 1a and 1b, or in the control units 7a and 7b. The temporal profiles of the welding currents IS1 and IS2 must therefore be synchronized. To achieve this, the two welding machines 1a and 1b must be synchronized.

[0025] For this purpose, the welding machines 1a, 1b, 1c of the multi-pulse welding process are connected to each other via the control units 7a, 7b, 7c of the welding machines 1a, 1b, 1c, via a communication link 15, which can be either wired or wireless, as shown in Fig.3 As shown, at the beginning of the multi-pulse welding process, a synchronization information SI is sent via communication link 15 from one welding device 1a, preferably of the leading pulse welding process, to the other welding device 1b, 1c, preferably of the trailing pulse welding processes. This synchronization information SI is used in the receiving welding device 1b, 1c to adapt, in particular to synchronize, the pulse welding process carried out by this welding device 1b, 1c with the pulse welding process carried out by the sending welding device 1a.

[0026] In the simplest case not according to the invention, the synchronization information SI is a single synchronization pulse SP, which is sent by a transmitting welding machine 1a via the communication link 15. The synchronization pulse SP is in a defined temporal relationship to the welding cycle SZ1 in the transmitting welding machine 1a. Preferably, the synchronization pulse SP is sent at the beginning of a welding cycle SZ1 (for example, the beginning of a base current phase) with the pulse frequency f D1 in the transmitting welding machine 1a. The synchronization pulse SP can also be sent with a specific stored or set phase shift t P. To achieve more precise synchronization, known delay times, for example, transmission time or a reaction time of the receiving welding machine 1b, 1c, etc., can also be taken into account in the phase shift t P.

[0027] The synchronization pulse SP can be sent as a current or voltage pulse over a wired communication link 15 between the two welding machines 1a, 1b. Alternatively, the communication link 15 can be implemented as a data bus on which bus messages are sent. In this case, the synchronization pulse SP can be sent as a bus message, which can be implemented both wired (cable, fiber optic, etc.) and wirelessly (Wi-Fi, Bluetooth, etc.). In the receiving welding machine 1b, 1c, the welding current profile IS is synchronized to the received synchronization pulse SP, for example, by starting a welding cycle SZ2 in the receiving welding machine 1b with the pulse frequency f D2 upon receipt of the synchronization pulse (e.g., with the base current phase). The respective pulse frequencies f D1, f D2 can be stored or set in the welding machines 1a, 1b, 1c.

[0028] Similarly, a phase shift t P can be stored or set in a welding machine 1b, usually the tracking welding machine. This allows the welding cycle SZ2 in the receiving welding machine 1b to be started with a phase shift t P after receiving the synchronization pulse SP.

[0029] Other required welding parameters, such as the welding currents I SI1 , I SG1 , I SI2 , I SG2 , the pulse current durations, basic current durations, etc., are of course also stored or set in the welding machines 1a, 1b, 1c, so that the welding machines 1a, 1b, 1c can perform the pulse welding processes.

[0030] In principle, it is irrelevant to the invention which welding machine 1a, 1b is the transmitting machine, i.e., the one that initiates synchronization, and which is the receiving machine, i.e., the one that follows the synchronization. This can, for example, be stored or set in the welding machines 1a, 1b, 1c involved in the multi-pulse welding process. This setting can, of course, also change, even during welding. This setting can be made by the welder, for example, via the respective input / output unit 8a, 8b.

[0031] However, a higher-level control unit, such as a robot controller or process controller, can also be provided, which is connected to the welding machines 1a, 1b, 1c and specifies this setting. For this purpose, the welding machines 1a, 1b, 1c and the higher-level control unit can be connected to each other via a data bus, either in parallel or serially, to enable this setting. If the communication link 15 is implemented as a data bus, then this data bus can also be used for this setting.

[0032] It is also conceivable that the setting determining which welding machine 1a, 1b, 1c leads in the synchronization process is stored depending on a welding parameter, for example, the pulse frequency f D or the welding wire feed speed v D. Here, for instance, it could be stipulated that the welding machine 1a, 1b, 1c performing the pulse welding process with the highest pulse frequency f D is always the sending welding machine, and the others are the receiving welding machines.

[0033] An extension allows 15 additional pieces of information to be transmitted via the communication link.

[0034] According to one embodiment of the invention, the welding machine 1a transmitting the synchronization information SI also sends its own pulse frequency f D1 as synchronization information SI, or, not according to the invention, the pulse frequency f D2 to be set by the receiving welding machine 1b, for example in a separate or identical bus message. If the welding machine's own pulse frequency f D1 is sent, then a frequency divider F can be stored or set in the receiving welding machine 1b (as in Fig.3 (As indicated). The frequency divider F then allows the pulse frequency fD2 to be easily determined from the received pulse frequency fD1 as fD2 = fD1 / F. It is advantageous if the two pulse frequencies fD1 and fD2 are in an integer ratio (e.g., ½, ½, ¼) to each other, meaning the frequency divider F is an integer. This also makes it possible to change the pulse frequencies fD1 and fD2 during the multi-pulse welding process. For example, it is sufficient for the leading welding machine 1a to send a new pulse frequency fD1 to the following welding machine 1b, which then uses the frequency divider F to recalculate and adjust the pulse frequency fD2. The pulse frequency fD2 of the receiving welding machine 1b thus follows the pulse frequency fD1 of the sending welding machine 1a.In the other case, the receiving welding machine 1b receives the set pulse frequency f D2 directly from the sending welding machine 1a, meaning that no settings are required on the receiving welding machine 1b in this regard. In both cases, the handling of the multi-pulse welding process is simplified for the welder.

[0035] The same procedure can be used for the desired phase shift tD. The phase shift tD, which can also be zero, can be stored or set in a welding machine 1a, 1b, or it can be sent from a welding machine 1a to the other welding machine 1b as synchronization information SI, for example in a separate bus message or in a shared bus message with other synchronization information SI.

[0036] The phase shift tD can also be variably set on a welding machine 1a, 1b, for example as a time or as a percentage. Preferably, the phase shift tD can be variably set between 0 and 100% in individual percentage steps, e.g., in 1% increments. For example, 25% corresponds to a phase shift of 90° and 50% to a phase shift of 180°. The phase shift tD can be set by the welder or can be specified by a higher-level control unit, for example, again via a data bus as described above.

[0037] It would also be conceivable that the desired phase shift tD is synchronized via the timing of the transmission of the synchronization information SI. For example, the sending welding machine 1a could send the synchronization information SI to the receiving welding machine 1b with the phase shift tD shifted after the start of the pulse current phase. In this case, the desired phase shift tD would be stored or set in the sending welding machine 1a. The receiving welding machine 1b then begins its own pulse current phase or base current phase (depending on the synchronization) upon receiving the synchronization information SI, which automatically sets the desired phase shift tD. Thus, a change / adjustment of the phase shift tD during the welding process is possible.

[0038] In a further embodiment according to the invention, the transmitting welding device 1a, for example the leading welding device in the tandem pulse welding process, continuously sends synchronization pulses SP as synchronization information SI at its own pulse frequency f D1, i.e. with a time period t D1, as in Fig.4 The synchronization pulses SP are shown. These synchronization pulses are in turn linked to the welding cycle SZ1 in the transmitting welding machine in a defined temporal relationship. For example, a synchronization pulse SP is sent at the beginning of each welding cycle SZ1, here at the beginning of the pulse current phase, taking into account a phase shift t P. These synchronization pulses SP can in turn be sent as electrical current or voltage pulses on an electrical line as a communication link 15 or as bus messages on a wired or wireless data bus as a communication link 15.The receiving welding machine 1b, for example the welding machine tracked in the tandem pulse welding process, determines in an evaluation unit (hardware and / or software) in the control unit 7b, from the period t D1 of the received synchronization pulses, simply the pulse frequency f D1 of the sending welding machine 1a, for example in a comparator circuit with counter or from a timestamp of the received bus messages.

[0039] The welding cycle SZ2 in the receiving welding machine 1b is synchronized again in time to the synchronization pulses SP, for example by synchronizing the start of a welding cycle SZ2 in the receiving welding machine 1b to the reception of a synchronization pulse SP.

[0040] The receiving welding machine 1b can contain a frequency divider F, from which the pulse frequency f D2 in the receiving welding machine 1b can then be determined as f D2 = f D1 / F. It is advantageous if the two pulse frequencies f D1 and f D2 are in an integer ratio to each other. Since the synchronization pulses SP are continuously transmitted, at least during synchronization, the pulse frequency f D2 of the receiving welding machine 1b automatically follows the pulse frequency f D1 of the transmitting welding machine 1a.

[0041] The transmitting welding machine 1a can send the set value of the pulse frequency f D2 to the receiving welding machine 1b in addition to the synchronization pulses SP, for example, again in a separate or the same bus message. In this case, the synchronization pulses SP can be used to ensure and monitor the synchronization of the two welding machines 1a and 1b.

[0042] By shifting the synchronization pulses SP relative to the welding cycle SZ1 in the transmitting welding machine 1a, a phase shift t P of the two current waveforms in the two welding machines 1a and 1b can, of course, be set. The receiving welding machine 1b synchronizes the time course of the welding current I S2 to the received synchronization pulses SP, as shown in Fig.4 As shown. Alternatively, a desired phase shift tP can be stored or set as a welding parameter in the receiving welding machine 1b. In this case, the receiving welding machine 1b would shift the welding cycle SZ2 in time by the phase shift tD to the reception of the synchronization pulse SP. However, both are also possible simultaneously.

[0043] The pulse frequency fD1, fD2, or a frequency divider F, required for the pulse welding process can be set by the welder on the welding machines 1a, 1b. However, this requires in-depth process knowledge on the part of the welder, which cannot be assumed. Therefore, it may be possible to derive a pulse frequency fD1, fD2 from other set welding parameters, in particular from a welding wire feed rate vD (which is usually dependent on the welding current) or a welding current IS. A welding characteristic curve for various welding wires, as shown in [reference to relevant figure], can be stored in the welding machine 1a, 1b, for example in the control unit 7a, 7b or a storage unit. Fig.5 The welding wire feed rate vD is used as an example and is stored in the system. Depending on the set welding wire feed rate vD, the required pulse frequency fD can be derived. For synchronization, it is advantageous to set a pulse frequency fD determined in this way to the nearest integer ratio to the other pulse frequency fD. From this, a required frequency divider F can then also be derived, which is preferably set to the nearest integer. It follows that, instead of the pulse frequency fD1, the welding wire feed rate vD1 could also be sent to the receiving welding machine 1b in an equivalent manner if the welding characteristic curve is stored in both welding machines 1a and 1b.

[0044] In Fig.6 A tandem pulse welding process is represented with fD1 = fD2 (i.e., frequency divider F = 1) and a phase shift tP of 90°. Additionally, short intermediate pulses ZP1, ZP2, i.e., short increases in the welding current IS1, IS2, are provided in the base current phases of both pulse welding processes. The duration and rise time of the intermediate pulses ZP1, ZP2 can, of course, be stored or configured in the welding machines 1a, 1b. It is possible that intermediate pulses ZP1, ZP2 are not provided in all pulse welding processes of the multi-pulse welding process. Likewise, it is conceivable that such intermediate pulses ZP1, ZP2 are not provided in every welding cycle SZ1, SZ2, but only in every xth welding cycle, which can also be stored or configured. Preferably, the intermediate pulses ZP1, ZP2 in one pulse welding process are set so that they lie in the pulse current phase of the other pulse welding process.This can be achieved very easily, for example, with a phase shift of 180°, where a basic current phase and a pulse current phase overlap in the two pulse welding processes.

[0045] The synchronization of the pulse welding processes of a multi-pulse welding process according to the invention can be started and stopped as needed during welding. Preferably, the synchronization is only started after the arcs of the individual pulse welding processes have stably burned, i.e., after the arcs have been ignited or when the set welding wire feed speed v D has been reached. Synchronization is also preferably stopped in the final phase of the multi-pulse welding process, for example, when the welding wire feed speed v D is reduced. This can be done automatically by the welding machines 1a, 1b, or manually by the welder.

[0046] It is also possible that the synchronization of the pulse welding processes changes during welding. For example, a different frequency divider F may be set or occur during welding. The welding wire feed speed of the subsequent pulse welding process may also be changed, which can likewise result in a different pulse frequency f D2 or frequency divider F. Likewise, a different phase shift t P between pulse welding processes may be required or set. Such changes can be caused, for example, by the multiple pulse welding process (e.g., an automated welding program) and / or by the welder.

[0047] For example, the deviation between a pulse frequency f D1 required by the leading pulse welding process, to which the following pulse welding process synchronizes, and a pulse frequency f D2, which results from the stored welding characteristic curve (e.g. as in Fig.5 ) would result from the set welding parameters exceeding a limit value configured or stored in the welding machine 1a, 1b. In this case, the control unit 7a, 7b of the welding machine 1a, 1b can, for example, switch to the next frequency divider F, for example from F = 1 to F = 2 or in the other direction, i.e., from F = 2 to F = 1. A phase shift t P can also be adjusted as needed.

[0048] In Fig.7 The diagram illustrates, for example, the switching between synchronization with identical pulse frequencies fD1 and fD2 in a tandem pulse welding process, fD1 = fD2, and a phase shift tP of 180° to a halved pulse frequency fD2 of the trailing pulse welding process, i.e., fD2 = fD1 / 2 or frequency divider F = 2, and a phase shift tP of 0°. The welding current IS1 of the leading pulse welding process and the welding current IS2 of the trailing pulse welding process (dashed lines) are shown over time t. The switching occurs at time tU. The switching process changes to the new pulse frequency fD2. The new phase angle is adjusted, if necessary, within a few welding cycles SZ1, SZ2, depending on the control system implementation. (See example below.) Fig.2 The new phase position is set within four welding cycles SZ1 of the leading impulse welding process.

Claims

1. Method for synchronizing at least two pulse welding processes for carrying out a multiple pulse welding process, whereas a pulse welding process consists of periodically at a pulse frequency (fD1, fD2) repeated welding cycles (SZ1, SZ2) having a pulse current phase and a base current phase, each pulse welding process being performed by a welding device (1a, 1b), wherein the welding devices (1a, 1b) are connected to one another by a communication link (15) and a synchronization information (SI) is transmitted via the communication link (15) from a transmitting welding device (1a) to at least one receiving welding device (1b), to synchronize the pulse welding process performed by the receiving welding device (1b) with the pulse welding process performed by the transmitting welding device (1a), wherein the transmitting welding device (1a) transmits at least one synchronization pulse (SP) as synchronization information (SI) to at least one receiving welding device (1b), wherein the at least one synchronization pulse (SP) is in a defined temporal relation to the welding cycle (SZ1) of the pulse welding process of the transmitting welding device (1a), and the welding cycle (SZ2) of the pulse welding process of the receiving welding device (1b) is synchronized based on the received synchronization pulse (SP), characterized in that either the pulse frequency (fD1) of the transmitting welding device (1a) is additionally transmitted as synchronization information (SI), and that the pulse frequency (fD2) to be set by the receiving welding device (1b) is determined in the receiving welding device (1b) from the received pulse frequency (fD1) of the transmitting welding device (1a) using a known frequency divider (F) or the transmitting welding device (1a) continuously transmits synchronization pulses (SP) as synchronization information (SI) at the pulse frequency (fD1) of the transmitting welding device (1a) to the receiving welding device (1b), and that the receiving welding device (1b) determines the pulse frequency (fD1) of the transmitting welding device (1a) from the period of the received synchronization pulses (SP) and from this determines the pulse frequency (fD2) to be set in the receiving welding device (1b) using a known frequency divider (F).

2. Method according to claim 1, characterized in that the frequency divider (F) is determined in the receiving welding device (1b) from a known welding characteristic curve of at least one welding parameter, and the pulse frequency (fD2) to be set by the receiving welding device (1b) is determined from the pulse frequency (fD1) of the transmitting welding device (1a), or the associated welding wire feed speeds (vD), and from the frequency divider (F).

3. Method according to claim 2, characterized in that a pulse frequency (fD2) required for the pulse welding process is determined from the welding characteristic curve of the pulse welding process of the receiving welding device (1b), wherein the frequency divider (F) is determined from the required pulse frequency (fD2) and the received pulse frequency (fD1) of the transmitting welding device (1a), or the associated welding wire feed speeds (vD).

4. Method according to claim 3, characterized in that the ratio between the received pulse frequency (fD1) of the transmitting welding device (1a) and the required pulse frequency (fD2), that is set to the nearest smaller or larger integer, is used as the frequency divider (F).

5. Method according to any of the claims 1 to 4, characterized in that the synchronization pulse (SP) is transmitted with a predetermined phase shift (tP) at the start of the welding cycle (SZ1) in the transmitting welding device (1a) and / or the welding cycle (SZ2) is started in the receiving welding device (1b) with a predetermined phase shift (tP) after the synchronization pulse (SP) is received.

6. Method according to claim 5, characterized in that the phase shift (tP) to be set by the receiving welding device (1b) is transmitted as additional synchronization information (SI) from the transmitting welding device (1a) to at least one receiving welding device (1b).

7. Method according to any of claims 1 to 6, characterized in that the synchronization is started or stopped during the multiple pulse welding process.

8. Method according to any of claims 1 to 7, characterized in that the pulse frequency (fD1) of the pulse welding process of the transmitting welding device (1a) or the pulse frequency (fD2) of the pulse welding process of a trailing pulse welding process and / or a phase shift (tP) is changed during the multiple pulse welding process.

9. An arrangement for carrying out a multiple pulse welding process with at least two welding devices (1a, 1b) designed to carry out at least two pulse welding processes, wherein a pulse welding process consists of periodically at a pulse frequency (fD1, fD2) repeated welding cycles (SZ1, SZ2) having a pulse current phase and a base current phase, wherein the welding devices (1a, 1b) each comprise a control unit (7a, 7b) and they are connected to one another by a communication link (15) and the control unit (7a) of a transmitting welding device (1a) is configured to transmit a synchronization information (SI) via the communication link (15) to at least the control unit (7b) of a receiving welding device (1b), wherein the control unit (7b) of the receiving welding device (1b) is configured to use said synchronization information (SI) to synchronize the pulse welding process performed by the receiving welding device (1b) with the pulse welding process performed by the transmitting welding device (1a), wherein the control unit (7a) of the transmitting welding device (1a) is configured to transmit at least one synchronization pulse (SP), which is in a defined temporal relation to the welding cycle (SZ1) of the pulse welding process of the transmitting welding device (1a), as synchronization information (SI) to at least one receiving welding device (1b), and the control unit (7b) of the receiving welding device (1b) is configured to synchronize the welding cycle (SZ2) of the pulse welding process of the receiving welding device (1b) based on the received synchronization pulse (SP), characterized in that the control unit (7a) of the transmitting welding device (1a) is configured to transmit, as synchronization information (SI), either additionally the pulse frequency (fD1) of the transmitting welding device (1a) and the control unit (7b) of the receiving welding device (1b) is configured to determine the pulse frequency (fD2) to be set by the receiving welding device (1b) from the received pulse frequency (fD1) of the transmitting welding device (1a) using a known frequency divider (F), or that the control unit (7a) of the transmitting welding device (1a) is designed to continuously transmit synchronization pulses (SP) with the pulse frequency (fD1) of the transmitting welding device (1a) to the receiving welding device (1b) as synchronization information (SI), and the control unit (7b) of the receiving welding device (1b) is configured to determine the pulse frequency (fD1) of the transmitting welding device (1a) from the period of the received synchronization pulses (SP) to determine the pulse frequency (fD1) of the transmitting welding device (1a) and, from this, to determine the pulse frequency (fD2) to be set in the receiving welding device (1b) using a known frequency divider (F).

10. The arrangement according to claim 9, characterized in that the control unit (7b) of the receiving welding device (1b) is configured, to determine the frequency divider (F) from a known welding characteristic curve of at least one welding parameter, and from the pulse frequency (fD1) of the transmitting welding device (1a) or the associated welding wire feed speeds (vD), and to determine the pulse frequency (fD2) to be set by the receiving welding device (1b) from frequency divider (F).

11. The arrangement according to claim 10, characterized in that the control unit (7b) of the receiving welding device (1b) is configured, to determine a pulse frequency (fD2) required for the pulse welding process from the welding characteristic curve of the pulse welding process of the receiving welding device (1b) and to determine the frequency divider (F) from the required pulse frequency (fD2) and the received pulse frequency (fD1) of the transmitting welding device (1a), or the associated welding wire feed speeds (vD).

12. The arrangement according to claim 11, characterized in that the control unit (7b) of the receiving welding device (1b) is configured, to use the ratio, being set to the nearest smaller or larger integer between the received pulse frequency (fD1) of the transmitting welding device (1a) and the required pulse frequency (fD2), as the frequency divider (F).