Welding device having wire-play detection, and method for determining a wire-play value

Abstract

The invention relates to a welding device (100) and to a method for determining a wire-play value of a welding device (100), which welding device comprises a welding torch (140) and a movement means (110) having a forward mode (V) for moving a wire electrode (1) of the welding device (100) in the forward direction, and having a reverse mode (R) for moving the wire electrode (1) in the reverse direction. The method comprises at least the following automated steps: moving (S20) the wire electrode (1) in the forward mode (V) until a short circuit is detected between the wire electrode (1) and a workpiece; subsequently moving (S30) the wire electrode (1) in the reverse mode (R); - then starting (S40) a measurement of the wire feed length (s); - terminating (S50) the measurement of the wire feed length (s) as soon as a break-up of the short circuit is detected; and - outputting (S60) a wire-play value (D1) on the basis of the measured wire feed length (s).

Description

[0001]Welding device with wire play detection and method for determining a wire play value Technical field The present invention relates to a welding device with wire play detection and a method for determining a wire play value. The invention also provides a method for operating a welding device, as well as an associated computer program product and data storage medium. Background of the invention Welding devices are composed of several components that can usually be exchanged, for example to perform different welding tasks. For example, different wire cores are used for different wire electrode diameters, or entire hose packages are exchanged depending on their length. In each welding device, the wire electrode (or: the welding wire), as explained in Figs. 9 and 10, has between a conveyor device 110 for conveying the wire electrode and theContact tube at the end of the welding torch 140 has a certain amount of wire play. Fig. 9 schematically shows the wire play of a wire electrode 1 within a wire core 3 during forward operation V of the conveyor device 110. Fig. 10 shows the wire play during reverse operation R of the conveyor device 110. The arrows indicate bends within the wire core or the welding torch 140 that can contribute to the wire play of the wire electrode. In this case, the wire electrode 1 tends to bear against the outer radii of bends with substantial wire play during forward operation V (see arrows to the bends in Fig. 9), while in reverse operation R it tends to bear against the inner radii of bends (see arrows to the bends in Fig. 10) after the wire play has been eliminated. The exact value of the wire play present at any given time, or in other words, the wire feed length by which a wire electrode must be fed through the conveyor before it reaches theThe fact that the wire electrode end actually changes from a standstill can influence many processes on the welding device. In particular, there are welding processes that function better the more precisely the position of the wire electrode end is known at all times. The lack of knowledge about the current wire clearance value makes it difficult to carry out such welding processes precisely. KR 102186 992 B1 relates to a method for controlling arc welding. The method comprises a motor that can feed a welding wire forwards and backwards in order to detect and remove excess material caused by the bending of the wire using a voltage measurement, thereby maintaining a stable arc during a welding process. EP 1677 941 B1 discloses a method for determining the position of a welding wire relative to the workpiece after the ignition of an arc during aWelding process. The welding wire is used as a sensor in order to be able to carry out a mechanical adjustment process for determining the position of the welding wire. Summary of the Invention It is therefore an object of the present invention to provide a welding device with wire play detection, a method for determining a wire play value and a method for operating a welding device, which overcome the above-mentioned difficulties. Accordingly, according to a first aspect of the present invention, a welding device is provided comprising: a conveyor device with a forward operation for conveying a consumable wire electrode of the welding device in the forward direction and with a reverse operation for conveying the wire electrode in the reverse direction; a welding torch with a contact tube which is electrically connected or connectable to a defined electrical potential and by means of which an electricalContact can be made with the wire electrode; an electrical parameter measuring device which is set up to measure an electrical parameter between the wire electrode and a workpiece; a control device which is set up to carry out a wire play measuring method: - to control the conveyor device to feed the wire electrode in forward operation until a short circuit between the wire electrode and the workpiece is detected by means of the electrical parameter measuring device; - then (in particular immediately) to control the conveyor device to feed the wire electrode in reverse operation; - then (in particular upon the occurrence of a predetermined event) to start a measurement of the wire feed length and to end this measurement as soon as the electrical parameter measuring device detects that the short circuit has broken down; and - to output a wire play value based on the measured wire feed length.When "devices" are mentioned here, it is understood that this does not necessarily mean that such devices must be designed as separate devices. Different functionalities can be referred to as different devices, even though they may possibly be implemented by one and the same hardware. Likewise, overlaps between different devices can exist, whereby one or more devices can also be implemented wholly or partially as software executed by a computing device. A wire feed speed is understood here to be a speed at which a wire electrode of the welding device moves, regardless of whether it moves forwards or backwards. A wire feed length is understood to be a length by which the conveyor device has moved a part of the wire electrode that is in contact with it. Due to the alwaysDue to the existing and partially unknown wire play, as explained above, the wire feed length does not (always) correspond to a movement of the wire electrode end. This description describes various high-precision measuring methods based on physical measurement processes of times and speeds, as well as on the control of actuators (e.g., the conveyor device). It is understood that signal propagation times and reaction times to signals, measurement inaccuracies, inertia, and the like occur. Unless these are explicitly discussed, it is also understood that the person skilled in the art can provide appropriate corrections if they wish to achieve increased accuracy at any point. Likewise, it is understood that when it is mentioned herein that something is carried out "immediately" or "immediately thereafter" or the like, the aforementioned effects and similar effects are to be taken into account. According to someIn some embodiments, variants, or refinements of embodiments, the measurement of the wire feed length is started (exactly) when the wire feed speed passes through a zero crossing from positive to negative. In this way, the wire feed length measured at that time corresponds particularly precisely to the wire play value to be measured. Alternatively, the wire feed length can also be measured beforehand, for example immediately after the feed device has been controlled (or activated) to feed the wire electrode in reverse operation, i.e., with the start of the deceleration of the then still positive wire feed speed. The output wire play value can be corrected for the resulting error, since the control device has knowledge of the wire feed speed at the time of the activation at the time of the detected short circuit, as well as information about the deceleration exerted or exercisable by theConveyor device. With this information, the additional wire feed length can be calculated, which is still caused by the inertia of the conveyor device after the short circuit has occurred, and which can thus still be deducted from the measured wire play value. A corresponding procedure can also be followed for other times of starting the measurement and ending the measurement. According to some embodiments, variants, or refinements of embodiments, the control device is also configured to carry out a welding process using the output wire play value. For example, the control device can be configured to calculate a time at which a welding current is increased using the output wire play value and to output a corresponding control command, that is, to output a control command which causes or instructs that the welding current at the calculated timeis increased. In particular, the control device can be configured to calculate a point in time at which the welding current is increased during conveying of the wire electrode in reverse operation of the conveying device after a short circuit (e.g., to reignite an arc) using the output wire play value and to output a corresponding control command, that is, to output a control command which causes or instructs that the welding current is increased at the calculated point in time. The control device can also be configured to calculate other welding parameters of the welding device (in particular, the welding power source) or of a welding process using the output wire play value and to output a corresponding control command. Such welding parameters can, for example, be further ignition parameters (or: start parameters) of an ignition process or reignition process, comprising, for example: - aWelding voltage value, - a welding current value and / or - a wire feed speed, as well as times at which changes in these welding parameters are to be made. According to some embodiments, variants, or refinements of embodiments, the control device is configured to automatically carry out the wire clearance measurement method in a rule-based manner. In this way, it can be avoided that the wire clearance value currently used for controlling welding processes or other settings deviates too much from an actual wire clearance value (which changes over time). For example, the wire clearance measurement method can be carried out after each weld seam. According to some embodiments, variants, or refinements of embodiments, the control device is also configured to receive information about a predefined length over which the wire electrode end extends over one end of the contact tube.should protrude (so-called "contact tip to workpiece distance, CTWD), and to control the conveyor to feed the wire electrode based on the output wire play value such that the wire electrode end protrudes beyond the end of the contact tube by the predefined length. The precise setting of a desired stickout length is important, for example, for automated welding processes, for example using linear travel gears, wherein, for example, a robot that guides the welding torch can precisely bring the wire electrode tip to a desired distance from the workpiece. The welding device according to the invention can thus also comprise a robot that is configured to guide the welding torch. According to some embodiments, variants, or refinements of embodiments, the wire feed length is measured using a timer and / or a speed sensor. Bothcan be integrated into a measuring device (or an encoder) of the conveyor device so that it outputs a numerical value corresponding to a wire feed length (e.g., in millimeters). This wire feed length can be accumulated to obtain a cumulative wire feed length, so that, for example, a wire feed length of +3 mm followed by a wire feed length of -2 mm results in a cumulative wire feed length of +1 mm. According to some embodiments, variants, or refinements of embodiments, the welding device is connectable to a plurality of components and has a data memory configured to store each wire feed value determined for a component or combination of components and to provide the stored wire feed values ​​for welding processes using one of the plurality of components. The plurality of components can, for example, include at least one further welding torch,at least one further conveyor device and / or at least one hose assembly. The rule-based execution of the wire clearance measurement method can include that it is always executed when at least one component is replaced, or at least when at least one component is replaced for which it is stored that this can cause a change in the wire clearance value. Thus, the wire clearance measurement method would be carried out, for example, when a hose assembly is replaced, but not when a gas supply or the like is replaced. A user interface of the welding device can also be configured to give a user the option of triggering the wire clearance measurement method on request, for example, to check core wear. The wire clearance measurement method can also be triggered via a remote maintenance interface of the welding device. Furthermore, according to a second aspect, the invention provides a methodfor determining a wire play value of a welding device, which has a welding torch and a conveyor device with a forward operation for conveying a wire electrode of the welding device in the forward direction and with a reverse operation for conveying the wire electrode in the reverse direction, comprising at least the following (in particular automated) steps: - conveying the wire electrode in the forward operation until a short circuit between the wire electrode and a workpiece is detected; - then conveying the wire electrode in the reverse operation until the wire feed speed undergoes a zero crossing from positive to negative; - then starting a measurement of the wire feed length, - ending the measurement of the wire feed length as soon as a break in the short circuit is detected; and - outputting a wire play value based on the measured wire feed length. The invention also provides, according to a third aspect, aA method for operating a welding device is provided, comprising at least the steps of: providing the output wire play value according to the method according to an embodiment of the second aspect of the present invention; and adjusting a position of a wire electrode end of a wire electrode of the welding device using the provided wire play value and / or adjusting a time at which a control signal is output using the provided wire play value. According to some embodiments, variants, or refinements of embodiments, the time to be set at which the control signal is output is a time at which a welding current of the welding device and / or a welding voltage of the welding device is increased or decreased. According to a fourth aspect, the invention provides a computer program product comprising executable program code, which is configured toit is executed to carry out the method according to an embodiment of the second or third aspect of the present invention. The computer program product can, for example, be designed for execution by a computing device in a welding power source or a wire feeder box, such as a microprocessor, an application-specific integrated circuit (ASIC), a programmable logic controller (PLC), and / or the like. According to a fifth aspect, the invention provides a non-transitory, computer-readable data storage medium comprising executable program code which, when executed, is designed to carry out the method of an embodiment of the second or third aspect of the present invention. The data storage medium can, for example, be a hard disk, a solid-state memory, a CD, a DVD, a memory card, and the like. According to a sixth aspect, the invention provides aA data stream or a data structure is provided which comprises executable program code or is designed to generate executable program code, and wherein the executable program code is designed, when executed, to carry out the method according to an embodiment of the second or third aspect of the present invention. Further preferred embodiments, variants, and developments of embodiments emerge from the subclaims and from the description with reference to the figures. Brief description of the figures The invention is explained in more detail below using exemplary embodiments in the figures of the drawings. The partially schematic representation shows: Fig. 1 a schematic block diagram for explaining a welding device according to an embodiment of the present invention; Fig. 2 the functioning of the welding device in three graphs lying one above the other on the same time axisfrom Fig. 1; Fig. 3 is a schematic flow diagram for explaining the method steps of a method according to one embodiment of the present invention; Fig. 4 is a schematic flow diagram for explaining the method steps of a method according to a further embodiment of the present invention; Fig. 5 is a graph for illustrating an advantageous welding method using the present invention; Fig. 6 is a graph for illustrating the welding method from Fig. 5 without using the present invention; Fig. 7 is a schematic block diagram for explaining a computer program according to a further embodiment of the present invention; Fig. 8 is a schematic block diagram for explaining a data storage medium according to yet another embodiment of the present invention; Fig. 9 is a possible source of wire play in a forward operation of a conveyor device of a welding device; and Fig. 10 is a possible source of wire playin a reverse operation of a conveyor device of a welding device. In all figures, identical or functionally equivalent elements and devices - unless otherwise stated - have been provided with the same reference numerals. The designation and numbering of the method steps does not necessarily imply a sequence, but serves to better distinguish them, although in some variants the sequence may also correspond to the numbering sequence. Detailed Description of the Figures Fig. 1 first shows a schematic block diagram to explain a welding device 100 according to the present invention. The operation of this welding device 100 will be explained, among other things, with reference to the following figures. According to Fig. 1, the welding device 100 comprises a conveyor device 110 with a forward operation V (not shown; see Fig. 9) for conveying a consumable wire electrode 1 of the welding device 100.in the forward direction, i.e. in the direction from a wire feed towards a welding torch 140 of the welding device 100, and with a reverse operation R (not shown; see Fig. 10) for conveying the wire electrode 1 in the reverse direction, i.e. from the welding torch 140 in the direction of the wire feed (not shown). The conveying device 110 can, for example, be implemented as part of a wire feed case, as indicated in Fig. 1. It comprises a wire feed 112, which can be either a wire storage device (e.g. for a wire spool within the wire feed case) or a threading device for threading a wire from an external wire storage device, e.g. a barrel, as a wire electrode 1. Between the welding torch 140 and the conveying device 110, the wire electrode 1 typically runs within a hose package 5, specifically within an inner wire guide or wire core 3, which is arranged in an outer hose 4. The welding torch 140comprises a contact tube 141 with a contact tube length L, which is or can be connected electrically to a defined electrical potential (welding potential) and by means of which an electrical contact can be established with the wire electrode 1, so that an arc can be formed between the wire electrode 1 and a workpiece 170 to be welded, which is at a second electrical potential. The welding device 100 also comprises an electrical parameter measuring device 120, which is designed to measure an electrical parameter between the wire electrode 1 and the workpiece 170. This can in particular be a voltage measuring device, which is designed to measure an existing voltage between the wire electrode 1 and the workpiece 170, and in particular to detect a short circuit between the wire electrode 1 and the workpiece. The welding device 100 further comprises a control device 130, which is designed toCarrying out a wire play measuring method is configured. For this purpose, the welding device 100 can have additional measuring devices or have access to the measurement results of such measuring devices. The additional measuring devices can include, in particular, a measuring device 150 of the conveyor device 110, which advantageously has a speed sensor 152 and / or a timer 154. Such a measuring device 150 can be configured to output a wire feed length signal by combining the measurement signals of the speed sensor 152 and the timer 154, which signal indicates a (particularly cumulative) wire feed length, i.e., a length (e.g., in millimeters) by which the wire electrode 1 was conveyed by the conveyor device 110. As shown in Fig. 1, the electrical parameter measuring device 120 and / or the control device 130 can be integrated into a welding power source 190 of the welding device 100. The welding power source 190has the task of controlling welding processes, which can also be performed by the control device 130. Secondly, it provides a welding potential at a first electrical connection 161, which can be applied to the contact tube 141 and thus to the wire electrode 1 via an electrical line 163. Finally, it provides a second electrical potential (e.g., ground, GND) at a second electrical connection 162, which can be applied to the workpiece 170, so that a welding current can then flow between the wire electrode end 2 and the workpiece 170 according to the potential difference. The control device 130 is configured to carry out the wire play measuring method: - to control the conveyor device 110 to convey the wire electrode 1 in the forward mode V until a short circuit between the wire electrode 1 and the workpiece 170 is detected by the electrical parameter measuring device 120; - then to stop the conveyor device 110to control the feeding of the wire electrode 1 in reverse operation R until the wire feed speed on the feed device 110 makes a zero crossing from positive to negative; - to then start a measurement of the wire feed length and to end this (only or exactly when) as soon as the electrical parameter measuring device 120 detects that the short circuit has broken; and - to output a wire play value D1 based on the measured wire feed length. Fig. 2 illustrates, in three graphs arranged one above the other on the same time axis t, how the device 100 according to the invention can carry out the wire play measuring method. The top graph in Fig. 2 shows the welding voltage U as a function of time. The middle graph shows the wire feed speed Vd on the feed device 110 as a function of time. Here, a positive wire feed speed, +Vd, means feeding of the wire electrode 1 in the direction ofContact tube 141 in forward operation V of the conveyor device 110, and a negative wire feed speed, -Vd, conveys the wire electrode 1 in the direction away from the contact tube 141 (i.e., toward the wire electrode supply) in reverse operation R of the conveyor device 110. The lower graph shows a wire clearance value in units of length stored in the control device 130. At the beginning of the illustrated time axis t, the wire electrode end 2 is separated from the workpiece by a distance that is unknown or not exactly known and is conveyed forward at a constant speed Vv. Until then, the previous wire clearance value D0 is still stored in the control device 130, which was determined, for example, before a wire electrode change or a change of the hose package 5 or another component of the welding device 100. At time t1, the electrical parameter measuring device 120 detects a short circuit, evident from the voltage drop.in the welding voltage in the top graph. As mentioned, the electrical parameter measuring device 120 can comprise or consist of a voltage measuring unit for this purpose. The control device 130, after receiving the information about the short circuit from the electrical parameter measuring device 120, immediately controls the conveyor device 110 to switch from forward operation V to reverse operation R. In particular, the conveyor device 110 should convey the wire electrode 1 at the negative speed Vr instead of the positive speed Vv. Vr is preferably smaller in magnitude than Vv, for example |Vr|<0.5 Vv (or: -Vr<0.5Vv), |Vr|<0.3 Vv, |Vr|<0.2 Vv or the like. In particular, Vv can be in the range from 0.5 m / min to 30 m / min and / or Vr in the range from -10 m / min to -2 m / min. Preferably Vv is between 2-5m / min and Vr between -5 to -2m / min. As can be clearly seen in the middle graph of Fig. 2, it takes some time toSpeed ​​from Vv to Vr, since the conveyor device 110 cannot decelerate (or "accelerate backwards") indefinitely. However, the conveyor device 110 has information, for example from a speed sensor 152 of the conveyor device 110, as to the point in time t2 at which the conveyor device 110 (with further deceleration or acceleration backwards exerted by the conveyor device 110) comes to a standstill, i.e., the wire feed speed has dropped to exactly zero. At this point in time t2, the control device 130 starts a measurement of the wire feed length, for example by starting a timer 154 and optionally (immediately or further) reading the speed sensor 152 of the conveyor device 110. It is understood that from a speed measurement and a time measurement, as well as a conversion factor, how much wire feed length corresponds to one full revolution of the conveyor device 110, an actually conveyedWire feed length is calculable. It is also understood that other techniques can be used when using a different conveyor device 110. Advantageously, the measuring device 150 already outputs a signal which (e.g., using the speed sensor 152 and the timer 154) indicates the wire feed length itself. Since the speed Vr is known to the control device 130, the concurrent reading of the speed sensor 152 can, in principle, be dispensed with at this point, resulting in only a minor measurement error at the beginning of the measurement (see below). At time t2, the wire play value recorded in the lower graph of Fig. 2 is thus initially provisionally set to zero, and from then on, continuously increased by the control device 130 with ongoing measurement of the wire feed length. The speed Vr can be selected in relation to the maximum deceleration that can be exerted by the conveyor device 110 such thata measurement error, which arises because the wire feed speed has not yet reached the value Vr at time t2, remains below a predetermined limit, e.g., below 10%, below 5%, or the like. Alternatively or additionally, this measurement error can also be compensated mathematically, for example, using a formula determined by experiments as a function of the ultimately determined wire play value D1. As can be seen further in Fig. 2, the measurement of the wire feed length is continued until a time t3, at which the breaking of the short circuit is detected by the electrical parameter measuring device 120, because the breaking of the short circuit means that the wire electrode end 2 has just detached from the workpiece. At this time t3, the control device 130 thus instructs the conveyor device 110 to stop the wire feed, i.e., to set Vd=0, which then occurs at time t4. The time between t2 and t3The (indirectly) measured (in terms of amount) wire feed length in the reverse direction thus represents the newly measured wire play value D1. Whenever the wire electrode 1 is now moved backwards, in particular after a short circuit (i.e. after contact with the workpiece), the measured wire play value D1 can be used to improve welding processes that benefit from precise knowledge of the time of the short circuit breaking, since these welding processes can now be carried out using the accurately determined wire play value D1. For this purpose, Fig. 3 shows a schematic flow diagram to explain the method steps of a method according to an embodiment of the present invention in an abstract manner. It is understood that the method steps can also be carried out independently of the welding device 100 according to the invention, but also according to all options, variants andrefinements and vice versa. In a step S10, a control command is received to carry out the wire clearance measurement method. This control command can be rule-based, for example, every time a component of the welding device 100 is changed, which can entail a change in the wire clearance value D0, D1. Such a component can be, for example, the welding torch 140, a hose package 5 between the welding power source and the welding torch, the wire electrode 1 itself, or the like. The control command can also, alternatively or additionally, be issued periodically, for example, when it is known that the wire clearance value D0, D1 usually changes by more than x% within a certain period of time, where x% represents a selectable threshold value. Depending on the specific implementation, in an optional step S15, the wire electrode 2 can first be retracted far enough to ensure that it is no longer in contact with theWorkpiece 170, for example, by a value that is greater than the distance from the contact tube end 142 to the workpiece 170, optionally increased by an estimated (or preset, or maximum measured) wire clearance value. In a step S20, the wire electrode 1 is conveyed in the forward mode V until a short circuit between the wire electrode 1 and a workpiece 170 is detected. In a step S30, the wire electrode 1 is then conveyed in the reverse mode R until the wire feed speed undergoes a zero crossing from positive to negative. For this purpose, sensor data or the like of the conveying device 110 (in particular of the measuring device 150) can be determined, as already explained in detail above. In a step S40, an (indirect) measurement of the wire feed length is started, in particular based on a time measurement, optionally based on a time measurement in combination with speed dataof the conveyor device 110. This measurement is continued until the measurement of the wire feed length is terminated in a step S50, namely as soon as a break in the short circuit is detected. As described above, step S40 can be carried out (i.e. the measurement can be started) exactly when the wire feed speed undergoes a zero crossing from positive to negative. Alternatively, steps S40 and / or S50 can also be carried out at earlier or later times, whereby corresponding deviations from the actual wire play value D1 can advantageously be mathematically calculated out. In a step S60, a wire play value D1 is output based on the measured wire feed length. In particular, the measured wire feed length itself can be output as the wire play value D1, or the measured wire feed length, which has been further adjusted using a correction function, for example to compensate forInertia effects, signal propagation times and / or the like. Fig. 4 shows a schematic flow diagram for explaining a method according to a further embodiment of the present invention, namely a method for operating a welding device 100. This method can also be carried out by means of the welding device 100 according to the invention, in particular by the control device 130, but also separately therefrom. In a step S70, the wire play value D1 output according to steps S10 to S60 is provided. Steps S60 and S70 can take place simultaneously or be identical. However, a data memory 131 can also be provided or present (shown in Fig. 1 by way of example as part of the control device 130), in which one or more provided wire play values ​​D1 are stored and can be retrieved when needed. For example, the welding device 100 to be operated can be designed to be equipped with many different componentsto be operated. Such components can be, for example, welding torches 140, conveyor devices 110, hose packages 5 and / or the like. Each such component, or even certain combinations of components, can be associated with a different wire play value D1, which can also change each time at least one component is replaced. The type of components currently used is usually known to the welding power source 190, since the components are identified - typically via a bus system - on the welding power source 190 at least with their type number or the like. Thus, it can be provided that when the components used (i.e., connected to the welding device 100) are changed, a check is first carried out (for example by the control device 130) to determine whether a wire play value for the components currently used (or the currently connected combination ofcomponents) is stored, and, if so, this wire clearance value is provided. Alternatively, it can be provided that whenever at least one new component (or at least one new component known to cause a change in the wire clearance) is connected, the method according to Fig. 2 is carried out to provide a new wire clearance value D1. In a step S80, a position of a wire electrode end 2 of a wire electrode 1 of the welding device 100 is set using the provided wire clearance value D1. For example, a length x over which the wire electrode end 2 protrudes beyond a contact tube end 142 of the contact tube 141 (so-called CTWD, see also Fig. 1) can be set using the provided wire clearance value D1. Alternatively or additionally, in a step S90, a time at which a control signal (e.g., by the control device 130)output, using the provided wire clearance value D1. An example of this is explained with reference to the following figures, Fig. 5 and Fig. 6. Fig. 5 illustrates an advantageous welding method in which an ignition or re-ignition of the welding arc is to take place after the short circuit with the wire electrode 1 retracting. The following Fig. 6 shows a comparable welding method from the prior art. From top to bottom, the individual graphs in Fig. 5 show the welding voltage U, the wire feed speed Vd at the conveyor device 110 (not: of the wire electrode end 2), a cumulative wire feed length s through the conveyor device 110, and the welding current I, each in a situation in which the wire electrode end 2 is initially conveyed to the workpiece without an arc in order to ignite a new arc, i.e., to carry out a re-ignition. In Fig. 6, the thirdGraph, i.e., the graph of the cumulative (or: accumulated) wire feed length s. A good timing of the control commands, i.e., a re-ignition shortly before the wire electrode loses contact with the workpiece and the short circuit is removed, reduces weld spatter and thus significantly improves the welding result. If the ignition current I2 (a welding current with a specific current value intended for re-ignition) is started too early for the re-ignition, stickout overheating, i.e., overheating of the wire electrode end 2, can occur. If the ignition current I2 is ignited too late, this can lead to an arc break. However, due to the wire play, the time at which the short circuit is removed is not identical to the time at which the conveyor device 110 is in reverse operation R, since the existing wire play must first be "used up." As Fig. 5 shows, the wire electrode end 2 initially approachesconstant wire feed speed (Vd=const., thus linearly increasing wire feed length s) to the workpiece, at I=0. At a time t5, a short circuit is detected (in particular by the electrical parameter measuring device 120) (voltage dip), whereupon the wire feed is immediately decelerated (slowed down), and the increase in the cumulative wire feed length s levels off accordingly. With the short circuit, a first, non-vanishing, welding current I1 begins to flow, corresponding to the voltage 0 which has not completely dropped to zero. At a time t6, the deceleration of the conveyor device 110 has caused the wire feed speed Vd to drop to zero, so that a further deceleration (ie, negative acceleration) of the conveyor device 110, now in reverse operation R, reduces the cumulative wire feed length s again from now on. In the prior art (see Fig. 6), shortly before the time t6 (which the control device 130, for example, determines via theSpeed ​​sensor 152 or a known deceleration force of the conveyor device 110 can roughly predict) sets the welding current I to the ignition current I2. Due to the wire play—unknown in the prior art—the start of the ignition current is, as already explained, subject to some uncertainty. As shown in Fig. 5, with the present invention, in contrast, the ignition current I2 can be switched on (time t7) precisely when the cumulative wire feed length s has reached a predetermined value s0. This value s0 can, for example, be a value at which the difference between the maximum cumulative wire feed length s1 at time t6 and the current cumulative wire feed length corresponds exactly to the determined wire play value D1, or to a wire play value D2 increased by a safety buffer. The increased wire play value D2 can, for example, be calculated by D2=D1+d, where d is a predetermined safety buffer value.for example, 1 mm, 2 mm, 3 mm, or the like. The safety buffer value can be adjusted by the control device 130, for example, based on a known wire electrode 1 used, a known welding torch 140 used, and / or the like. The increased wire clearance value D2 can also be calculated using a relative safety buffer from the determined wire clearance value D1, for example, D2=D1*(l+d%), where d% can be, for example, between 5% and 30%, in particular between 10% and 20% (limit values ​​are included in each case). When the short circuit breaks at time t8, the wire feed is accelerated forward again by the conveyor device 110, and the welding current I is set to its maximum value I3, or an increase in the welding current I from the ignition current I2 to the maximum value I3 is started or instructed. Fig. 7 shows a schematic block diagram for explaining a computer program product 200 according to aEmbodiment of the present invention. The computer program product 200 comprises executable program code 250, which, when executed, is designed to carry out the method according to an embodiment of the present invention, in particular the method described with reference to Fig. 3 and / or Fig. 4. Fig. 8 shows a schematic block diagram for explaining a non-transitory computer-readable data storage medium 300 according to an embodiment of the present invention. The data storage medium 300 contains executable program code 350, which, when executed, is designed to carry out the method according to an embodiment of the present invention, in particular the method described with reference to Fig. 3 and / or Fig. 4. In the preceding detailed description, various features have been summarized in one or more examples to improve the stringency of the presentation. However, it should be clear,that the above description is merely illustrative and not restrictive in nature. It is intended to cover all alternatives, modifications, and equivalents to the various features and embodiments. Many other examples will be immediately and readily apparent to those skilled in the art based on their technical knowledge in light of the above description. The embodiments were chosen and described in order to best illustrate the principles underlying the invention and their possible practical applications. This will enable those skilled in the art to optimally modify and utilize the invention and its various embodiments with respect to the intended use. It is further understood that units described as separate units may be partially integrated with one another. List of Reference Symbols 1 Wire electrode 2 Wire electrode end 3 Wire core 4 Hose 5 Hose package 100 Welding device 110 Conveyor device 120Electrical parameter measuring device 130 Control device 131 Data storage device 140 Welding torch 141 Contact tube 142 Contact tube end 150 Measuring device 152 Speed ​​sensor 154 Timer 161 Electrical connection 162 Electrical connection 163 Electrical cable 170 Workpiece 190 Welding power source D0, D1 Wire clearance values ​​I Welding current I1, I2, I3 Current values ​​L Contact tube length s Wire feed length s0, s1 Wire feed length values ​​S10..S90 Process steps t1,..t8 Times x Stickout length

Claims

Patent claims 1. Welding device (100), comprising: a conveyor device (110) with a forward operation (V) for conveying a consumable wire electrode (1) of the welding device (100) in the forward direction and with a reverse operation (R) for conveying the wire electrode (1) in the reverse direction; a welding torch (140) with a contact tube (141) which is or can be electrically connected to a defined electrical potential and by means of which an electrical contact to the wire electrode (1) can be established; an electrical parameter measuring device (120) which is for measuring an electrical parameter between the wire electrode (1) and a workpiece; a control device (130) which is designed to carry out a wire play measuring method: - to control the conveying device (110) to convey (S20) the wire electrode (1) in the forward operation (V) until a A short circuit is detected between the wire electrode (1) and the workpiece; - then to control the conveying device (110) to convey the wire electrode (1) in the reverse operation (R) (S30); - to then start (S40) a measurement of the wire feed length (s) and to terminate this measurement (S50) as soon as the electrical parameter measuring device (120) detects that the short circuit has broken down; and - to output a wire play value (Dl) based on the measured wire feed length (s) (S60).

2. Welding device (100) according to claim 1, wherein the measurement of the wire feed length (s) is started (S40) when the wire feed speed performs a zero crossing from positive to negative.

3. Welding device (100) according to claim 1 or 2, wherein the control device (130) is further configured to perform a welding process using the output wire play value (Dl).

4. Welding device (100) according to one of claims 1 to 3, wherein the control device (130) is configured to calculate a time (t7) at which a welding current (I) is increased using the output wire play value (Dl) and to output a corresponding control command.

5. Welding device (100) according to one of claims 1 to 4, wherein the control device (130) is configured to calculate a time (t7) at which the welding current (I) is increased during conveying of the wire electrode (1) in the reverse operation (R) of the conveying device (110) after a short circuit, using the output wire play value (Dl) and to output a corresponding control command.

6. Welding device (100) according to one of claims 1 to 5, wherein the control device (130) is configured to automatically carry out the wire play measuring method in a rule-based manner, in particular after each weld seam.

7. Welding device (100) according to one of claims 1 to 6, wherein the control device (130) is further configured to receive information about a predefined length over which the wire electrode end (2) is to protrude beyond an end of the contact tube (141), and to control the conveying device (110) to convey the wire electrode (1) based on the output wire play value such that the wire electrode end (2) protrudes beyond the end of the contact tube (141) by the predefined length.

8. Welding device (100) according to one of claims 1 to 7, wherein the measurement of the wire feed length (s) is carried out under Use of a timer (154) and / or a speed sensor (152).

9. Welding device (100) according to one of claims 1 to 8, wherein the welding device (100) is connectable to a plurality of components (5, 110, 140) and has a data memory (131) which is configured to store each wire play value (Dl) determined for a component (5, 110, 140) or combination of components (5, 110, 140) and to provide the stored wire play values ​​(Dl) for welding processes using one of the plurality of components (5, 110, 140).

10. Welding device (100) according to claim 9, wherein the plurality of components comprises at least one further welding torch (140), at least one further conveyor device (110) and / or at least one hose package (5).

11. Method for determining a wire play value (D0, Dl) of a welding device (100) which comprises a welding torch (140) and a conveyor device (110) with a Forward operation (V) for conveying a wire electrode (1) of the welding device (100) in the forward direction and with a reverse operation (R) for conveying the wire electrode (1) in the reverse direction, comprising at least the following automated steps: - feeding (S20) the wire electrode (1) in the forward operation (V) until a short circuit is detected between the wire electrode (1) and a workpiece; - then conveying (S30) the wire electrode (1) in the reverse operation (R); - then starting (S40) a measurement of the wire feed length (s); - Terminating (S50) the measurement of the wire feed length (s) as soon as a break in the short circuit is detected; and - Output (S60) a wire play value (Dl) based on the measured wire feed length (s).

12. A method for operating a welding device (100), comprising at least the steps: Providing (S70) the output wire play value (Dl) according to the method according to claim 11; and Setting (S80) a position of a wire electrode end (2) of a wire electrode (1) of the welding device (100) using the provided wire play value (Dl) and / or setting (S90) a time (t7) at which a control signal is output using the provided wire play value (Dl).

13. The method according to claim 12, wherein the time to be set (t7) at which the control signal is output is a time at which a welding current (I) of the welding device (100) and / or a welding voltage (U) of the welding device (100) is increased or decreased.

14. A computer program product (200) comprising executable program code (250) which, when executed, is designed to carry out the method according to any one of claims 11 to 13.

15. Non-transitory, computer-readable data storage medium (300) with executable program code (350) which, when executed, is designed to carry out the method according to one of claims 11 to 13.

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