Laser wire welding process and laser wire welding system

Abstract

A method for laser wire welding using a laser wire welding system is described, comprising the following steps: controlling a wire feed device of the laser wire welding system to change the wire feed; controlling a laser beam device of the laser wire welding system to change a laser beam, wherein controlling the wire feed device to start the wire feed and controlling the laser beam device to switch on the laser beam, taking into account a latency time of the laser beam device and / or a latency time of the wire feed device, such that the change time of the wire feed and the change time of the laser beam have a predetermined time interval from each other. Furthermore, a laser wire welding system configured to carry out the method is described.

Description

[0001] The present invention relates to a method for laser wire welding, in particular for laser wire cladding, and to a laser wire welding system, in particular a laser wire cladding system. Technical background

[0002] Laser wire welding, particularly laser wire cladding, is an additive manufacturing process in which a wire-shaped (cladding) material is melted by a laser beam and bonded to at least one workpiece (also called a substrate). Multiple workpieces can be welded together using the same material. A laser welding head directs a laser beam, emitted from a laser source or the end of a laser fiber, onto a processing zone on the workpiece. A wire feeder guides the wire (also called welding wire) to the processing zone. The wire feeder can be located on or within the laser processing head, or even be part of it.

[0003] Fig. Figures 5a-5c show possible positions of the wire tip 2a relative to the focal point 10a of the laser beam during laser wire welding. Fig. 5a The wire tip is located at the focal point of the laser beam. If the control of the laser beam power and the control of the wire or wire tip feed are not sufficiently synchronized or coordinated, various problems can occur. For example, if the wire is advanced too early or the laser beam power is increased too late, the wire tip will be located above or in front of the focal point of the laser beam (illustrated in Fig. 5c). In this process, it can happen that the front part of the wire is not sufficiently melted, which can lead to an inadequate bond between the wire and the workpiece. Conversely, if the wire is advanced too late or the laser beam is switched on too early, the wire tip will be below or after the focal point of the laser beam (illustrated in Fig. 5b). In this process, the wire may melt too early and migrate upwards or away from the workpiece as a molten bead, which, in addition to the aforementioned poor bonding, can also lead to the destruction of the wire guide nozzle of the wire feed device (so-called "balling"). If the workpiece is relatively thin, a lack of synchronization or poor timing of the laser beam power control and wire feed can also lead to excessive heat input into the workpiece material.

[0004] These problems are particularly important when only small and / or discrete structures are to be applied to the workpiece, such as cylinders with a diameter of 1 mm to 5 mm and a height of 2 mm to 10 mm, since the welding defects are very large in relation to the overall structure. Summary of the invention

[0005] The purpose of the present disclosure is to specify an improved method for laser wire welding, in particular for laser wire cladding welding.

[0006] Furthermore, it is an objective of the present disclosure to specify a method for laser wire welding which can prevent or at least reduce welding defects due to insufficient or missing synchronization or timing coordination between the control of the wire feed and the control of the laser beam.

[0007] Furthermore, it is an object of the present disclosure to specify a method for laser wire welding with which a change in the wire supply, in particular starting and / or stopping, and a change in the laser beam, in particular switching on and / or off, can be carried out in a time-coordinated manner, i.e. at a precise time interval from each other, in particular synchronously.

[0008] Furthermore, it is an object of the present disclosure to specify a method for laser wire welding with which the position of the tip of the welding wire can be determined simply, quickly and precisely.

[0009] Furthermore, it is an object of the present disclosure to specify a laser wire welding system which is set up to carry out the laser wire welding process.

[0010] Further tasks, technical advantages and effects arise for the expert from studying the description, the drawings and the requirements.

[0011] Within the scope of this disclosure, "changing the laser beam" means changing a laser beam setting, e.g., changing the laser beam power and / or changing the focus position of the laser beam. Changing the laser beam power can include increasing the laser beam power, in particular ramping up the laser beam power to a predetermined value from a current value that is lower than the predetermined value, and / or decreasing the laser beam power, in particular ramping down the laser beam power to a predetermined value from a current value that is higher than the predetermined value. The predetermined value and / or the current value can be greater than or equal to 0 watts. "Turning on the laser beam" means ramping up the laser beam power from 0 watts to a predetermined value greater than 0 watts."Switching off the laser beam" refers to reducing the laser beam power from a value greater than 0 watts to 0 watts. Changing the laser beam or laser beam power therefore includes both switching the laser beam on and switching it off. Changing the laser beam can also include changing the focus position of the laser beam along its direction of propagation.

[0012] In the context of this disclosure, “changing the wire feed” means changing a wire feed setting, e.g., changing the wire feed speed and / or changing the wire feed direction. “Starting the wire feed” may include increasing the wire feed speed from 0 m / s to a predetermined value greater than 0 m / s, for example, between 15 mm / s and 120 mm / s. “Stopping the wire feed” means decreasing the wire feed speed from a value greater than 0 m / s to 0 m / s. In particular, changing the wire feed speed may include increasing the wire feed speed to a predetermined value from a current value that is lower than the predetermined value, or decreasing the wire feed speed to a predetermined value from a current value that is higher than the predetermined value. The predetermined value and / or the current value may be greater than or equal to 0 m / s.Changing the wire feed can therefore include starting and / or stopping the wire feed. A wire feed can include or be the extension of the wire, i.e., into a machining zone or out of the wire feed device. A wire feed speed greater than 0 m / s can be described as wire feeding into a predefined machining zone of a workpiece. A wire feed speed less than 0 m / s can be described as retracting or removing the wire from the machining zone of a workpiece.

[0013] Changing the wire feed can therefore involve not only changing the wire feed velocity, i.e., changing the magnitude of the wire feed velocity, but also changing the sign of the wire feed velocity, i.e., changing the direction of the wire feed (reversing the wire feed). Changing the direction of the wire feed means changing the wire feed velocity from a value equal to or greater than 0 m / s to a negative value, or changing the wire feed velocity from a negative value to a value equal to or greater than 0 m / s.

[0014] The position of the wire can be defined as the position of the wire end in a three-dimensional, particularly Cartesian, coordinate system. For example, the position of the wire can be specified or defined relative to the TCP (tool center point) or with respect to a world coordinate system.

[0015] A "wire feed control point" or a "laser beam control point" can refer to the point in time at which a wire feed device receives a corresponding control signal to change the wire feed, or a laser beam device receives a control signal to change the laser beam, from a control device, e.g., via a bus or bus system, or wirelessly. This can also be referred to as "applying the control signal" to the wire feed device or the laser beam device. In the case of real-time control, the wire feed control point or the laser beam control point can essentially correspond to the point in time at which the control device sends the control signal to change the wire feed to the wire feed device or the control signal to change the laser beam to the laser beam device. An (actual) "laser beam change point" orAn (actual) "wire feed change point" can refer to the point in time at which the change in the laser beam or wire feed has actually occurred or is complete. The (actual) switch-on point of the laser beam can be defined as the point in time at which the laser beam reaches a predetermined laser beam power. The (actual) start point of the wire feed can be defined as the point in time at which the wire feed reaches a predetermined wire feed speed.

[0016] The latency of a laser beam device can be defined as the time interval between receiving the control signal to change the laser beam and the actual change of the laser beam, specifically the completion of the change, i.e., reaching the desired laser setting. Similarly, the latency of a wire feed device can be defined as the time interval between receiving the control signal to change the wire feed and the actual change of the wire feed, specifically the completion of the change, i.e., reaching the desired wire feed setting.

[0017] The present invention is based on the finding that in laser wire welding, latency times exist when changing the wire feed and when changing the laser beam between the application of the control signals to the wire feed device or to the laser beam device and the actual time of change of the wire feed or the laser beam.

[0018] The core of the present invention is to take these latency times into account when controlling the wire feed device to change the wire feed (for example, starting the wire feed) and the laser beam device to change the laser beam (for example, switching on the laser beam), so that the change in wire feed and the change in laser beam are carried out with a predetermined time interval, for example, synchronously. This ensures an optimal welding result.

[0019] According to one aspect of the present disclosure, a method for laser wire welding using a laser wire welding system is specified, comprising the following steps: controlling a wire feed device of the laser wire welding system to change the wire feed (in particular, starting the wire feed, stopping the wire feed, changing the wire feed speed and / or changing the direction of the wire feed), controlling a laser beam device of the laser wire welding system to change a laser beam (in particular, switching on the laser beam, switching off the laser beam, changing the laser beam power and / or changing the focus position of the laser beam), wherein controlling the wire feed device and controlling the laser beam device is carried out taking into account a latency of the laser beam device and / or a latency of the wire feed device,that a change in the wire feed and a change in the laser beam have a predetermined time interval from each other. Here, a wire feed control point and a laser beam control point can be determined or coordinated in such a way that a change in the wire feed and a change in the laser beam have a predetermined time interval from each other, or are separated by a predetermined time interval.

[0020] According to another aspect of the present disclosure, a method for laser wire welding using a laser wire welding system is specified, comprising the following steps: controlling a wire feed device of the laser wire welding system to start the wire feed (for example, from a predetermined starting position of the wire), controlling a laser beam device of the laser wire welding system to switch on a laser beam for melting the wire, wherein the control of the wire feed device to start the wire feed and the control of the laser beam device to switch on the laser beam are carried out taking into account a latency time of the laser beam device and / or a latency time of the wire feed device such that a start time of the wire feed and a switch-on time of the laser beam have a predetermined initial time interval from each other.

[0021] According to another aspect of the present disclosure, a method for laser wire welding using a laser wire welding system is specified, comprising the following steps: controlling a wire feed device of the laser wire welding system to start the wire feed of a wire (for example, from a predetermined starting position of the wire), controlling a laser beam device of the laser wire welding system to switch on at least one laser beam to melt the wire, wherein a time of wire feed control and a time of laser beam control are determined or coordinated such that a start time of the wire feed and a switch-on time of the laser beam have a predetermined (first) time interval from each other or are at a predetermined (first) time interval from each other.

[0022] According to another aspect of the present disclosure, a method for laser wire welding using a laser wire welding system is specified, comprising the following steps: controlling a wire feed device of the laser wire welding system to stop the wire feed, controlling a laser beam device of the laser wire welding system to switch off a laser beam, wherein a time of wire feed control to stop the wire feed and a time of laser beam control to switch off the laser beam are determined or coordinated such that a stop time of the wire feed and a switch-off time of the laser beam have a predetermined (second) time interval from each other or are at a predetermined (second) time interval from each other.

[0023] According to a further aspect of the present disclosure, a laser wire welding system is disclosed, comprising: a laser beam device configured for generating a laser beam and / or for directing the laser beam into a predetermined processing zone, a wire feed device configured for feeding a wire into the predetermined processing zone, and a control device, in particular a real-time control device, configured for controlling the laser beam device and the wire feed device, wherein the laser wire welding system is configured to perform a method according to one of the aspects or embodiments disclosed herein. The control device may be configured to control elements of the laser wire welding system to perform a method according to one of the aspects or embodiments disclosed herein.The laser wire welding system may further comprise a bus or bus system to which the control device, the wire feed device and / or the laser beam device are connected, or through which the control device is connected to the wire feed device and / or the laser beam device.

[0024] Aspects and embodiments of the present disclosure may include one or more of the following optional features: The wire feed device can be controlled by a control device of the laser wire welding system. This control device can be a real-time capable device. The control device can have a latency of less than 5 ms, e.g., 1 ms. The control device can be connected to the wire feed device and / or the laser beam device via a bus or bus system. The bus or bus system can be a real-time capable bus or bus system. The bus or bus system can have a latency of less than 5 ms, e.g., 1 ms.

[0025] The specified time interval (e.g., the first and / or second) can be greater than or equal to 0 ms. If the specified time interval is 0 ms, the wire feed activation and the laser beam activation occur simultaneously, i.e., the laser beam activation and the wire feed activation are synchronous.

[0026] The start time of the wire feed and the switch-on time of the laser beam can be the same or simultaneous. In other words, the start of the wire feed and the switch-on of the laser beam can occur simultaneously or synchronously. The stop time of the wire feed and the switch-off time of the laser beam can be the same or simultaneous. In other words, the stopping of the wire feed and the switch-off of the laser beam can occur simultaneously or synchronously. The change time of the wire feed and the change time of the laser beam can be the same or simultaneous. In other words, the change in the wire feed and the change in the laser beam can occur simultaneously or synchronously.

[0027] The timing of the wire feed control can be determined taking into account a latency of the wire feed device. The timing of the laser beam control can be determined taking into account a latency of the laser beam device. The timing of the wire feed control and the timing of the laser beam control can be coordinated taking into account a latency of the wire feed device and / or a latency of the laser beam device.

[0028] The latency of the wire feed device can be determined (e.g., experimentally) or based on a manufacturer's specification. The latency of the laser beam device can also be determined (e.g., experimentally) or based on a manufacturer's specification. The latency of the wire feed device can be greater than the latency of the laser beam device.

[0029] The method may include determining the latency of the laser beam device and / or the latency of the wire feed device. Alternatively, the latency of the laser beam device and / or the latency of the wire feed device may be predetermined, e.g., by a manufacturer's specification. The method may also include storing the latency of the laser beam device and / or the latency of the wire feed device, e.g., in the control device of the laser wire welding system.

[0030] The latency of the laser beam device can specify or encompass a time period between the time the laser beam device receives a control signal from the control device to change the laser beam (change control signal) and the (actual) time of change of the laser beam.

[0031] The latency of the laser beam device can include a turn-on latency. The turn-on latency can be defined as the time between the laser beam device receiving a control signal from the control device to turn on the laser beam (turn-on control signal) and the actual turn-on time of the laser beam. In other words, the turn-on latency of the laser beam device can be defined as the time between the laser beam control signal being sent to turn on the laser beam and the actual turn-on time of the laser beam. The latency of the laser beam device can also include a turn-off latency. The turn-off latency can be defined as the time between the laser beam device receiving a control signal from the control device to turn off the laser beam (turn-off control signal) and the actual turn-off time of the laser beam.In other words, the switch-off latency of the laser beam device can be defined as the time between the point in time when the laser beam is switched off and the (actual) point in time when the laser beam is switched off. The switch-on latency and the switch-off latency of the laser beam device can be the same or different from each other.

[0032] The latency of the wire feed device can specify the time interval between the time a control signal is received by the wire feed device of the control device to change the wire feed and the actual time the wire feed is changed.

[0033] The wire feeder latency can include a start latency. The start latency can be defined as the time between the wire feeder receiving a control signal from the control device to initiate wire feeding and the actual start time of wire feeding. In other words, the wire feeder start latency can be defined as the time between the wire feeder's control signal to initiate wire feeding and the actual start time of wire feeding. The wire feeder latency can also include a wire feeder stop latency. The wire feeder stop latency can be defined as the time between the wire feeder receiving a control signal from the control device to initiate wire feeding and the actual stop time of wire feeding.In other words, the stop latency of the wire feed device can be defined as the time between a signal to stop the wire feed and the actual stop time. The start latency and the stop latency of the wire feed device can be the same or different. The same applies to the speed change latency with respect to increases and decreases in speed (or speed magnitude) and / or the direction change latency.

[0034] The timing of the laser beam activation to switch on the laser beam can be determined by taking into account the switch-on latency of the laser beam device. The timing of the laser beam activation to switch off the laser beam can be determined by taking into account the switch-off latency of the laser beam device.

[0035] The timing of the wire feed control signal to start the wire feed can be determined by taking into account the start latency of the wire feed device. The timing of the wire feed control signal to stop the wire feed device can be determined by taking into account the stop latency of the wire feed.

[0036] The timing of the wire feed control to change the wire feed speed can be determined by taking into account the speed change latency of the wire feed device. The timing of the wire feed control to change the direction of the wire feed can also be determined by taking into account the direction change latency of the wire feed device.

[0037] The timing of the wire feed control and / or the laser beam control can further be determined taking into account a control device latency. The control device latency can include a processing latency of the control device. Alternatively or additionally, the control device latency can include a latency of a bus or bus system of the laser wire welding system, in particular a bus or bus system between the control device and the wire feed device and / or between the control device and the laser beam device. The latency of the bus or bus system can be 1 ms or less.

[0038] The laser beam device can be configured to change the laser beam, in particular to switch the laser beam on and / or off and / or to change the laser power. The wire feed device can be configured to change the wire feed, in particular to start the wire feed, to stop the wire feed, to change the wire feed speed and / or to change the wire feed direction.

[0039] The control device can be a real-time capable control device. The control device can actuate the wire feed device and / or the laser beam device in real time. This actuation can be performed via the bus or bus system of the laser wire welding system.

[0040] The bus system can be or include a fieldbus system. The bus system can be or include a bus system selected from the following group: EtherCAT®, PROFINET®, Ethernet-IP®.

[0041] The method can further include the following steps: advancing the wire from an unknown position using the wire feed device, determining the point of contact at which the wire touches an object, particularly a workpiece, and determining the wire's position at that point of contact, specifically the position of the wire tip, as the wire's starting position. The wire's starting position can be determined relative to a tool center point (TCP) of the laser wire welding system. These steps can be performed before starting the wire feed or before the actual laser wire welding process. This allows the wire's starting position to be determined simply, quickly, reliably, and precisely.

[0042] Determining the contact point can involve sensing or detecting an electrical signal. This electrical signal can be generated when the wire, particularly the wire tip, touches the object or workpiece. Determining the contact point can also include sensing the force required to feed the wire. Alternatively or additionally, the wire's position can be determined as its starting position, preferably using a camera unit of the laser wire welding system.

[0043] The determined initial position can be compared to a predetermined starting position. If the determined initial position coincides with the predetermined starting position, the determined initial position can be defined or used as the predetermined starting position. Alternatively, starting from the determined initial position, the wire can be retracted or advanced by a defined length to bring it to the predetermined starting position. The defined length can be determined by comparing or subtracting the determined initial position from the predetermined starting position.

[0044] Laser cladding, or laser wire cladding, can be a coaxial laser cladding process. The at least one laser beam can travel coaxially along at least one section of the wire. The at least one laser beam can be annular, particularly in a plane perpendicular to the wire. This plane is preferably located in the section of the wire along which the at least one laser beam travels coaxially. The at least one laser beam can have a rotationally symmetric and / or twist-symmetric shape, particularly in the specified plane perpendicular to the wire. The plane perpendicular to the wire and / or the wire section can be located in a predefined processing zone.

[0045] The method can include generating the laser beam and directing the laser beam into the predetermined processing zone. The method can also include feeding the wire into the predetermined processing zone. According to embodiments, the method can include directing one or more laser beams into the predetermined processing zone. The one or more laser beams can be fed axially. The multiple laser beams can be arranged rotationally symmetrically and / or rotationally symmetrically to each other, and preferably relative to the wire.

[0046] The process can include generating and / or emitting a continuous laser beam. The process can also include continuously feeding the wire. The term "continuous" here can be understood as "constant over time" or as the opposite of "pulsed."

[0047] The laser beam can be a pulsed laser beam. The process can involve generating and / or emitting a pulsed laser beam. Therefore, the process can involve repeatedly switching the laser beam on and off.

[0048] The method can involve pulsed wire feeding. This means the wire feed can be repeatedly started and stopped. With each start and stop of the wire feed, the laser beam can be switched on and off. The starting and stopping of the wire feed and the switching on and off of the laser beam can be timed such that the start time of the wire feed and the switch-on time of the laser beam have a predetermined first time interval, and / or that the stop time of the wire feed and the switch-off time of the laser beam have a predetermined second time interval. The predetermined first time interval and the predetermined second time interval can be the same or different.

[0049] The process can involve alternating or repeated advance and retraction of the wire. The distance traveled back can be less than the distance the wire was advanced in the preceding step.

[0050] The laser wire welding process can be a laser wire cladding process. The process, according to the aspects and embodiments described, can be used for laser wire cladding and / or laser wire brazing. The system, according to the aspects and embodiments described, can be used for laser wire cladding and / or laser wire brazing. The process can be used for laser wire welding and / or laser wire brazing of a metallic workpiece and / or a metallic wire. The system can be configured for laser wire welding and / or laser wire brazing of a metallic workpiece and / or a metallic wire.

[0051] The process can be used for laser cladding to deposit the wire material onto a workpiece. The wire and / or the workpiece can be made of or consist of a material comprising at least one of the following: titanium (Ti), aluminum (Al), TiAl, a titanium alloy, and an aluminum alloy, in particular an aluminum alloy of the 5000 series, 6000 series, or 7000 series.

[0052] The method can be used for 3D printing and / or for the stepwise application of the wire material to a workpiece. Stepwise application can involve repeatedly switching the laser beam on and off, and correspondingly starting and stopping the wire feed multiple times. A step duration can be defined as the time between switching the laser beam on and off, or between starting and stopping the wire feed. Alternatively, the step duration can be defined as the time between two switching-on cycles of the laser beam or between two starting cycles of the wire feed. In this case, the step duration can also include the cooling time, for example, of the applied material. The step duration can be between 100 ms and 2 s, preferably between 300 ms and 500 ms, and particularly preferably 400 ms. The limits are included in each case.

[0053] The method can be used alternatively or additionally for applying a structure to a workpiece, in particular a cylindrical structure, for example, with a diameter of 1 mm to 5 mm, preferably 3 mm, and / or a height between 2 mm and 10 mm, preferably between 5 mm and 10 mm, particularly preferably 6 mm, or between 5 mm and 15 mm, preferably 10 mm. The method can also be used alternatively or additionally for applying a structure to a workpiece with a wall thickness of between 1 mm and 3 mm, preferably 2 mm, and a height between 2 mm and 10 mm, preferably between 5 mm and 10 mm, particularly preferably 6 mm, or between 5 mm and 15 mm, preferably 10 mm. The limits are inclusive in each case.

[0054] A predefined processing zone can specify a defined area in which the material of the wire tip is to be melted by the laser beam. The predefined processing zone can be located above and / or on the surface of a workpiece. The predefined processing zone can be variable over time. The processing zone can correspond to a tool center point. The system can also be referred to as a plant. The control device can also be referred to as a plant controller. The workpiece can also be referred to as a substrate.

[0055] The laser beam device may include a laser source and / or a laser welding head. The wire feed device may be located on or within the laser processing head. In particular, the wire feed device may be permanently connected to the laser beam device or the laser processing head.

[0056] The change in laser radiation can occur before the change in wire feed, or vice versa. The changes can also occur simultaneously. The first and / or the second time interval can be equal. The time interval, e.g., the first and / or the second time interval, can be between 0 ms and 10 ms, preferably between 0 ms and 5 ms, and particularly preferably between 0 ms and 1 ms. If the time interval, e.g., the first and / or the second time interval, is between 0 ms and 1 ms, the laser beam and the wire feed can be described as "synchronous".

[0057] The wire thickness can be between 0.5 mm and 2 mm, preferably between 0.8 mm and 1 mm, including the limits. Brief description of the characters

[0058] Aspects and embodiments of the present disclosure are described in detail below with reference to figures. The figures show: Fig. 1a schematic view of a laser wire welding system according to embodiments of the present disclosure; Fig. 2 a flowchart of a method for laser wire welding using a laser wire welding system according to embodiments of the present disclosure; Fig. 3 a flowchart of a method for determining latency times according to embodiments of the present disclosure; Fig. 4a-c a flowchart of a method for determining an initial position of a wire according to embodiments of the present disclosure; Fig. 5a-c Positions of the wire tip relative to the focal point of the laser beam. Detailed description

[0059] Unless otherwise noted, the same reference symbols are used for identical and equivalent elements in the following text. Redundant descriptions of recurring features are avoided. The various embodiments and features of the figures described below are expressly combinable and should not be understood as complete embodiments.

[0060] The directions x, y, and z shown in the figures are coordinate axes of a Cartesian coordinate system. A direction along the z-direction can be called a vertical direction, and a direction along the x- or y-direction can be called a horizontal direction.

[0061] Fig. Figure 1 shows a schematic view of a laser wire welding system according to embodiments of the present disclosure.

[0062] The laser wire welding system 100 is designed to carry out the process of laser wire brazing or laser wire welding, in particular laser wire cladding, according to aspects and embodiments of the present disclosure. However, the present disclosure is not limited thereto.

[0063] The laser wire welding system 100 comprises a laser beam device 106, a wire feed device 102, and a control device 105. The laser wire welding system 100 can include a laser processing head 101, in particular a laser welding head, in which optical elements for guiding and / or shaping the laser beam are arranged. The laser beam device 106 can be a laser source 103 or comprise the laser source 103. The laser beam device 106 can further comprise adjustable collimation optics 110. The laser source 103 can be provided for generating the at least one laser beam 10. The laser source 103 can generate a laser beam 10 (processing beam), which is supplied to the laser processing head 101, for example, by means of an optical fiber 310.

[0064] In laser wire welding or brazing, the wire feed device 102 supplies the filler material in the form of a welding wire 2, or simply wire, to a processing zone 31 on or to a workpiece 3. The laser beam device 106 generates a laser beam 10 and shines it into the processing zone 31. This melts the material of the supplied wire and fuses it with the material of the workpiece 3. The wire is guided along a predetermined wire guide direction. Fig. 1. The wire guide direction runs vertically in a region of the welding wire 2 after exiting a housing 140 of the laser processing head 101 and before the processing zone 31. The processing zone 31 can include a tool center point, or the tool center point can define the processing zone 31.

[0065] The application of the welding wire material can also be carried out in stages. For example, the laser beam 10 can be pulsed, i.e., it can be repeatedly switched on and off alternately, whereby the feed of the wire 2 is started and stopped accordingly, or the wire 2 is moved back and forth in reverse.

[0066] Using the laser wire welding system 100, structures, in particular cylindrical structures or a weld seam, can be created on the surface of the workpiece 3, illustrated by the dashed line 32 in Fig. 1. During an application step and / or between two application steps, the processing zone 31 can be repositioned by moving the laser processing head 101 and / or the workpiece 3. A step duration can range from 100 ms to 2 s, for example, 400 ms. The structures can have a diameter of 1 mm to 5 mm, for example, 3 mm, and a height, measured from the workpiece surface, of 2 mm to 15 mm, for example, 6 mm or 10 mm.

[0067] The laser wire welding system 100 shown can be used for 3D printing on the workpiece 3 by appropriately controlling the laser processing head 101, the wire feed device 102 and the laser source 103.

[0068] The material of the wire 2 and the workpiece 3 can each consist of titanium or aluminum or an alloy with at least one of these materials.

[0069] The laser processing head 101 is configured to direct the laser beam 10 onto the workpiece 3. The laser processing head 101 can have one or more optical elements 110, 120, 130, 131, such as lenses, objectives, mirrors, prisms, axicons, etc. The optical elements serve to guide and shape the laser beam 10. The optical elements can be transmitting and / or reflective. For example, the laser processing head 101 has collimating optics 110, focusing optics 120, and zoom optics or a zoom lens (not shown). The optical elements allow, for example, the adjustment of the focus position and / or focus diameter of the laser beam 10. The laser processing head 101 can also have a deflecting mirror 131 for deflecting the laser beam 10. For example, the deflecting mirror 131 can change the direction of propagation of the laser beam 10 by 90 degrees.The deflecting mirror 131 can have an opening for guiding the wire 2 through it. Furthermore, the laser processing head 101 can have optical elements 130, for example axicons and prisms, for generating an annular laser beam 10. The optical elements 130 are in . Fig. Figure 1 illustrates the laser beam as a single optical element, but the present disclosure is not limited to this. "Annular" can also mean that the laser beam 10 has a rotationally symmetric, in particular a rotationally symmetric, shape with respect to the direction of beam propagation.

[0070] According to further embodiments not shown, the laser wire welding system can also generate and direct multiple laser beams into the processing zone. The multiple laser beams can be arranged rotationally symmetrically and / or rotationally symmetrically to each other and to the wire.

[0071] The laser beam 10 or the arrangement of several laser beams can be ring-shaped at least in one section along the wire 2, in particular after exiting the housing of the laser processing head 101 and / or before entering the processing zone 31 and / or in the processing zone 31.

[0072] The wire feed device 102 is configured to feed the wire 2 into the processing zone 31. For this purpose, the wire feed device 102 can be configured to feed the wire 2 from a wire reservoir, e.g., a wire spool (not shown), to the processing zone 31 at a predetermined speed. Furthermore, the wire feed device 102 can be configured to retract the wire 2 from the processing zone 31 or, after it has passed through the wire guide device 104. The wire feed device 102 can be arranged on or in the laser processing head 101. In particular, the wire feed device can be rigidly connected to the laser beam device 106 or the laser processing head 101. However, the present disclosure is not limited to this.

[0073] A wire guide 104 can be provided to guide the wire 2 to the processing zone 31. The wire guide 104 ensures that the wire 2 is guided to the processing zone 31 substantially along the predetermined wire guide direction. The wire guide 104 can be arranged or attached to the housing 140 of the laser processing head 101, for example, at a lower end. Preferably, the wire guide 104 is arranged downstream of the last optical element, for example, a focusing optic 120, or downstream of the last protective glass (not shown) with respect to the propagation direction of the laser beam 10; however, the present disclosure is not limited to this. According to other non-limiting embodiments, and as described in Fig. As shown in Figure 1, the wire 2, starting from the wire feed device 2, can first pass through the laser processing head 101 before exiting the laser processing head 101 or the wire guide device 104. The wire guide device 104 can be part of the wire feed device 2 and / or part of the laser processing head 101.

[0074] The laser beam 10, or the previously described arrangement of multiple laser beams, can propagate coaxially with the predetermined wire guidance direction of the welding wire 2, at least along a section of the wire 2. This means that the beam propagation direction and the wire guidance direction of the welding wire 2 can be coaxial and / or parallel to each other and / or coincide, at least for a certain distance. For example, the laser beam 10 can propagate coaxially with the wire 2 after passing the deflecting mirror 131 and / or after exiting the housing 140 of the laser processing head 101 and / or shortly before or upon entering the processing zone 31 and / or within the processing zone 31. Furthermore, the laser beam 10 can be directed coaxially with the wire 2 into the processing zone 31.

[0075] The laser source 103 is configured to change the laser beam, in particular to switch it on and / or off and / or to change the laser power of the laser beam 10. The wire feed device 102 is configured to change the wire feed, in particular to start the wire feed, to stop the wire feed, to change the wire feed speed and / or to change the wire feed direction.

[0076] The control device 105 can be real-time capable. The control device 105 is configured to control the laser beam device 106 of the wire feed device 102, in particular to carry out a laser wire welding method according to one of the aspects or embodiments disclosed herein. Furthermore, the laser wire welding system 100 can include a bus or bus system 107, which can be real-time capable. The bus 107 serves to transmit control signals from the control device 105 to the laser beam device 106 and the wire feed device 104 of the laser wire welding system 100. Alternatively, the control device can be connected to the laser beam device 106 and the wire feed device 104 for wireless communication, e.g., via Bluetooth, WLAN, or similar technology.

[0077] The laser wire welding system 100 can include a camera unit 109. The camera unit 109 can be configured to observe the laser wire welding process and / or to detect the position of the wire 2 or the tip of the wire.

[0078] The workpiece 3 or workpieces can be designed as a plate-shaped and / or metallic workpiece.

[0079] Fig. Figure 2 shows a flowchart of a method for laser wire welding using a laser wire welding system according to embodiments of the present disclosure. The method can be carried out using the laser wire welding system 100 according to Fig. 1 will be carried out.

[0080] Method 200 comprises a first step 201 in which the wire feed device of the laser wire welding system is controlled by the control device to change the wire feed. This change can, for example, include starting the wire feed. "Control" means that a corresponding control signal is received from the control device, possibly via the bus, by the wire feed device.

[0081] Method 200 comprises a second step 202 in which the laser beam device of the laser wire welding system is controlled by the control device to change the laser beam. This change can, for example, include switching the laser beam on. "Control" means that a corresponding control signal is received from the control device, possibly via the bus, by the laser beam device.

[0082] The timing of the wire feed control in step 201 and the timing of the laser beam control in step 202 are determined in such a way that a change time of the wire feed and a change time of the laser beam have a predetermined time interval from each other.

[0083] In particular, the control of the wire feed and the control of the laser beam can be determined or carried out taking into account a latency time of the wire feed device and / or a latency time of the laser beam device.

[0084] The latency of the laser beam device can be defined as the time between the control signal to change the laser beam, in particular the time of receipt of the control signal to change the laser beam, and the time at which the laser beam has been changed accordingly.

[0085] The latency of the laser beam device can include, in particular, a switch-on latency. The switch-on latency describes the time between the reception of the control signal to switch on the laser beam and the switch-on time of the laser beam itself. Thus, the timing of the laser beam control signal to switch on the laser beam can be determined by taking the switch-on latency of the laser beam device into account.

[0086] The latency of the wire feed device can be defined as the time between the activation to change the wire feed, in particular the time of receipt of the control signal to change the wire feed, and the time at which the wire feed has been changed accordingly.

[0087] The latency of the wire feed device can include, in particular, a start latency. The start latency describes the time between the reception of the control signal to start the wire feed and the actual start of the wire feed. Therefore, the timing of the wire feed control signal to start the wire feed can be determined by taking the start latency of the wire feed device into account.

[0088] In some embodiments, changing the wire feed can mean stopping the wire feed, and changing the laser beam can mean switching the laser beam off. The above statements apply accordingly.

[0089] Furthermore, the timing of the wire feed control and the laser beam control can be determined taking into account the latency of the control device. The control device latency can include a processing latency of the control device itself and / or a latency of the bus or bus system of the laser wire welding system. The control device latency can also be referred to as the "system control latency." When selecting a real-time capable control device or bus, the latency is usually known in advance. Control can be achieved, for example, via an EtherCAT® bus, where the latency is typically 1 ms in a standard configuration. If the control device is real-time capable, it also has a defined processing latency within which the control of the individual elements of the laser wire welding system takes place.

[0090] The described method allows for a precisely defined time interval between the actual moment the wire feed changes (starting in the example) and the actual moment the laser beam changes (switching on in the example). This time interval can be chosen arbitrarily. In particular, the time interval can be set to zero, so that the changes in wire feed and laser beam occur synchronously.

[0091] Depending on the application or process, it can be advantageous to first heat only the workpiece with the laser beam and then melt the wire. In this case, the laser beam device would first be activated to switch on the laser beam or increase its power. Then, at a defined interval, the wire feed device would be activated to start the wire feed and advance the wire tip into the processing zone or into the laser beam. If necessary, the laser beam can be switched off again before the wire feed begins, so that it is switched back on when the wire tip reaches the focal point of the laser beam.

[0092] In other cases, it is advantageous if the workpiece is not heated, but the wire tip is completely and precisely melted. For this purpose, the laser beam should be switched on or the laser beam power increased at the moment the wire tip reaches the processing zone or a focal position of the laser beam. The precise timing required for this, between changes in the wire feed and changes in the laser beam, is possible using the method according to aspects and embodiments of the present disclosure.

[0093] The laser wire welding process can incorporate additional control of the laser wire welding, which is performed, for example, by the control device. The control system can use signals from a sensor selected from: an OCT sensor, a camera, a photodiode, a lidar sensor, a pyrometric sensor, a thermal imaging camera, or a heat sensor, particularly one with spatial resolution.

[0094] Furthermore, an electrical contact signal can be used to switch off the laser beam if contact between the wire and the workpiece is lost. This contact signal can also be used to determine the wire tip position.

[0095] Fig. Figure 3 shows a flowchart illustrating a method for determining latency times according to embodiments of the present disclosure. This is based on the following: Fig. The method described in section 3 can be part of the laser wire welding method according to aspects and embodiments of the present disclosure. For example, the method for determining the latency times prior to steps 201 and 202 of method 200 according to Fig. 2 take place.

[0096] Using the reference to Fig. The latency of the laser beam device can be determined using the method described in section 3.

[0097] Method 300 is described with reference to the switch-on latency of the laser beam device, but applies to any change of the laser beam by the laser beam device, for example also to switching off and changing (starting up or shutting down) the laser beam power.

[0098] According to embodiments, the switch-on latency specifies a time period between the time of receipt of a control signal by the laser beam device to switch on the laser beam and the actual time of switch-on of the laser beam.

[0099] In a first step (301), for example, the time interval between the laser beam activation and the laser beam's activation time—that is, the actual response of the laser beam device, known as laser delay—is measured. The actual activation time of the laser beam can be defined as the point at which the laser beam reaches a predetermined power level. This time interval can then be stored or saved as the activation latency in the control device (step 302).

[0100] The laser beam control time can refer to the time at which the laser beam device receives the control signal to switch on the laser beam.

[0101] There are various methods for measuring the latency of a laser beam device. One method involves moving the laser processing head at a constant speed relative to a reference plate. Once the laser processing head reaches a specific position, the control signal to switch on the laser beam ("laser-on" signal) is sent. Upon reaching a second position, the control signal to switch off the laser beam ("laser-off" signal) is sent. This creates a mark with the laser, which, however, is shifted relative to the start and end points; that is, it begins after the start position and ends after the end position. The switch-on latency ("laser-on delay") can be determined from the speed and the lateral offset between the first position and the starting point of the mark.The laser-off delay can be determined from the lateral offset between the second position and the marking endpoint.

[0102] Method 300, described for the laser beam device, can be used accordingly to determine the latency of the wire feed device. This refers to the time delay between receiving the wire feed start signal ("wire feed start signal") and the actual start of the wire feed. The wire movement can be detected using a camera, with the start signal acting as the trigger. Alternatively, the latency of the wire feed device can be determined based on specifications provided by the manufacturer.

[0103] The laser wire welding process, which refers to Fig. As described in section 2, the wire can be fed from a defined and / or predetermined starting position. In other words, the wire feed is started from a defined and / or predetermined starting position.

[0104] Fig. Figure 4a shows a flowchart to illustrate a procedure for determining an initial position of the wire and, if necessary, for guiding the wire into the specified starting position. Fig. Figure 4a illustrates the positions of a wire tip in this procedure. The procedure can be performed before starting the wire feed. This allows the starting position of the wire to be determined simply, quickly, reliably, and precisely.

[0105] Fig. 4b and Fig. Figure 4c shows different positions of the wire. The position of the wire is subsequently equated with the position of the wire tip, but the present disclosure is not limited to this. Furthermore, in Fig. 4b and Fig. 4c shows only the positions of the wire tip for better illustration. Fig. 4b illustrates steps 401-403. Fig. Figure 4c illustrates step 404.

[0106] First, the starting position of the wire is determined. For this purpose, the wire is advanced from an unknown position 410 using the wire feed device (step 401), and a contact point is determined at which the wire, in particular the wire tip, touches an object 411, for example, a workpiece for the laser wire welding process (step 402). The wire can therefore be advanced in step 401 until it makes contact with the object 411 (step 402).

[0107] Determining the contact time can involve capturing or detecting an electrical signal. This electrical signal can be generated by contact between the wire, particularly the wire tip, and the object. Alternatively or additionally, determining the contact time can involve capturing the force required to feed the wire, and the resulting increase in force from contact with the object can be evaluated to determine the contact time.

[0108] The position of the wire at the time of contact is then determined as the starting position of wire 420 (step 403).

[0109] Alternatively or additionally, the starting position of the wire can be determined using the camera unit 109 of the laser wire welding system or by a camera-based method.

[0110] The determined initial position can be compared with a predefined starting position 430. The determined initial position can be set as or used as the predefined starting position. As in Fig. As shown in Figure 4b, the wire can alternatively be retracted from the determined starting position 420 by a defined length or distance (illustrated by a dashed arrow) to bring it to the specified starting position 430 (optional step 404). The defined length can be determined by comparing or subtracting the determined starting position from the specified starting position. The specified starting position can be located within a predefined processing zone and / or correspond to a tool center point of the laser wire welding system.

[0111] This allows the distance between the workpiece (e.g., item 411) and the wire tip or the focal point of the laser beam to be defined and precisely adjusted for the respective laser wire welding process, and thus ideally set for the specific process. Depending on the application, it may also be advantageous for the wire to always be in contact with the workpiece. This is also possible with the method for determining the wire's starting position and guiding the wire into the starting position.

[0112] The laser power and wire feed can now be controlled synchronously or with a defined time interval, also known as a time offset, according to the method described in this disclosure, in order to achieve an optimal welding result. This is now easily possible within the latency times of the system.

Claims

[1] Method for laser wire welding using a laser wire welding system (100), comprising the steps: - Controlling (201) a wire feed device (102) of the laser wire welding system to change the wire feed, - Controlling (202) a laser beam device (106) of the laser wire welding system to change a laser beam (10), wherein controlling (201) the wire feed device (102) to start the wire feed and controlling (202) the laser beam device (106) to switch on the laser beam (10) taking into account a latency time of the laser beam device (106) and / or a latency time of the wire feed device (102) such that a change time of the wire feed and a change time of the laser beam have a predetermined time interval from each other. [2] Method according to claim 1, wherein the time interval is greater than or equal to zero. [3] Method according to claim 2, further comprising determining (301) the latency of the laser beam device (106) and storing (302) the latency of the laser beam device (106), and / or further comprising determining (301) the latency of the wire feed device (102) and storing (302) the latency of the wire feed device (102). [4] Method according to any of the preceding claims, wherein changing the wire feed comprises starting the wire feed, stopping the wire feed, changing the wire feed speed and / or changing the direction of the wire feed; and / or wherein changing the laser beam comprises turning on the laser beam, turning off the laser beam, changing the laser beam power and / or changing the focus position of the laser beam. [5] Method according to one of the preceding claims, wherein changing the wire feed includes starting the wire feed and the latency of the laser beam device (106) includes a switch-on latency, wherein the switch-on latency specifies a time period between a time of laser beam control to switch on the laser beam (10) and a switch-on time of the laser beam (10), and / or wherein changing the laser beam includes switching on the laser beam and the latency of the wire feed includes a start latency, wherein the start latency specifies a time period between a time of wire feed control to start the wire feed and a start time of the wire feed. [6] A method according to any of the preceding claims, further comprising the steps of: Advance (401) the wire (2) from an unknown position (410), Determine (402) a contact time at which the wire (2) touches an object (411), Determine (403) a position of the wire (2) at the time of contact, in particular a position of the wire tip, as the starting position (420) of the wire (2). [7] Method according to claim 6, wherein determining the contact time (402) comprises detecting an electrical signal which is generated when the wire (2), in particular the wire tip, touches the object (411), and / or wherein determining (4029) the contact time comprises detecting a force required for the wire supply. [8] Method according to any one of claims 1 to 5, further comprising determining (403) a position of the wire (2) as a starting position of the wire (420) using a camera unit (109) of the laser wire welding system (100). [9] Method according to any one of claims 6 to 8, further comprising one of the following steps (404): Setting the determined initial position (420) as the starting position (430), or Retracting the wire (2) from the determined starting position (420) of the wire (2) to bring the wire to a predetermined starting position (430). [10] Method according to any of the foregoing claims, further comprising: - Controlling (201) the wire feed device (102) to stop the wire feed, - Controlling (202) the laser beam device (106) to switch off the laser beam (10), wherein controlling (201) the wire feed device (102) to stop the wire feed and controlling (202) the laser beam device (106) to switch off the laser beam (10) taking into account the latency of the laser beam device (106) and / or the latency of the wire feed device (102) is such that a stop time of the wire feed and a switch-off time of the laser beam (10) have a predetermined second time interval from each other. [11] Method according to claim 10, wherein the latency of the laser beam device (106) comprises a switch-off latency, wherein the switch-off latency specifies a time period between a time of laser beam control to switch off the laser beam (10) and a switch-off time of the laser beam (10), and / or wherein the latency of the wire feed comprises a stop latency, wherein the stop latency specifies a time period between a time of wire feed control to stop the wire feed and a stop time of the wire feed. [12] Method according to any of the preceding claims, wherein the laser beam (10) is coaxial to the wire (2) at least along a section of the wire (2), and / or wherein the laser beam (10) is ring-shaped, and / or wherein the laser beam (10) has a rotationally symmetric and / or rotationally symmetric shape or wherein a plurality of laser beams are arranged rotationally symmetric and / or rotationally symmetric around the wire (2). [13] Method according to any of the preceding claims, wherein the wire (2) and / or the workpiece consists of or comprises the following material: titanium (Ti), aluminum (Al), TiAl, a titanium alloy, and / or an aluminum alloy, in particular an aluminum alloy of the 5000 series, the 6000 series or the 7000 series. [14] Method according to any one of the preceding claims, wherein the laser beam (10) and / or the wire feed is pulsed, and / or wherein the wire (2) is alternately advanced and retracted, and / or wherein the laser beam (10) is repeatedly switched on and off and the wire feed is repeatedly started and stopped accordingly such that each start time of the wire feed and each switch-on time of the laser beam (10) have a predetermined first time interval from each other, and that each stop time of the wire feed and the switch-off time of the laser beam (10) have a predetermined second interval from each other. [15] Method according to any of the preceding claims, wherein the method is a laser cladding method, and / or the procedure further includes: stepwise application of the wire material (2) onto a workpiece (3), wherein a step duration is between 100 ms and 2 s, preferably between 300 ms and 500 ms, particularly preferably 400 ms, and / or Applying the wire material (2) in a structure onto a workpiece (3), wherein the structure is a cylindrical structure and / or has a diameter between 1 mm and 5 mm and / or a height between 5 mm and 15 mm, in particular between 2 mm and 10 mm, and / or a wall thickness between 1 mm and 3 mm. [16] Laser wire welding system (100), comprising: - a laser beam device (106), configured to generate a laser beam (10), - a wire feed device (102) configured to feed a wire (2) into a predetermined processing zone (31), and - a control device (105) configured to control the laser beam device (106) and the wire feed device (105); wherein the control device (105) is configured to perform a method according to any one of the preceding claims.

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