Method for generating a weld seam by means of a robot-guided friction stir welding tool, friction stir welding device and computer program product

Abstract

The invention relates to a method for generating a weld seam by means of a robot-guided friction stir welding tool (8) with an upright shoulder (9) along a join (10) of a joint of a first component (11) and a second component (12), inter alia comprising the steps of automatically measuring a physical variable characterizing the actual temperature (T) in the region of the plasticized material, of reducing the process pressing force of the friction stir welding tool (8) on the first component (11) and / or on the second component (12) by actuating the robot (2a) which guides the friction stir welding tool (8), and of automatically increasing the input of supplementary process heat in the region of the plasticized material by increasing the conductive resistance heating by increasing the input of electrical energy, in such a way that the actual temperature (T) of the plasticized material remains within a predefined setpoint temperature range. The invention also relates to an associated friction stir welding device (1) and to a corresponding computer program product.

Description

[0001] Method for producing a weld seam using a robot-guided friction stir welding tool, friction stir welding device and computer program product

[0002] The invention relates to a method for producing a weld seam using a robot-guided friction stir welding tool with a stationary shoulder along a joint of a first component and a second component. The invention also relates to an associated friction stir welding device and a corresponding computer program.

[0003] The process for producing a weld using a robot-guided friction stir welding tool with a stationary shoulder deals with friction stir welding. Friction stir welding itself is described in DIN EN ISO 4063 under process number 43. Friction stir welding is also referred to as FSW welding (English: Friction Stir Welding). In a basic application, two separate components, for example in a butt joint with two opposing end faces, are placed together and held in position by means of a clamping device. A friction stir welding tool comprises a stirring pin that rotates during the welding process and a shoulder surrounding the rotating stirring pin, which covers the plasticized material from above during welding in the form of a ring-shaped covering surface surrounding the stirring pin.The shoulder can either be designed to rotate with the stirring pin or, as a stationary shoulder, not rotate with the stirring pin. Stationary shoulder friction stir welding is also known as SSFSW welding (Stationary Shoulder Friction Stir Welding).

[0004] In the first process step, the stirring pin of the friction stir welding tool is set in rotation and pressed against at least one of the two clamped components in the immediate vicinity of the joint. Friction effects generate heat in the contact area between the rotating stirring pin and the component, causing the at least one component to plasticize in the area of ​​the rotating stirring pin. Due to this plasticization, the rotating stirring pin can penetrate deeper into the component. Subsequently, the rotating stirring pin is moved along the joint to be welded in a direction perpendicular to its axis of rotation. During this process, material from both components is successively plasticized, mixed in the joining zone, and then solidified by cooling in the direction of movement behind the rotating stirring pin, forming the finished weld.Furthermore, the compaction of the weld seam by the process force in the axial direction of the rotating stirring pin is an essential component for the formation of the weld. Finally, at the end of the weld seam or further away from the fully formed weld seam, the rotating stirring pin is withdrawn from the still plasticized zone on the stirring pin and out of the welded components.

[0005] Friction stir welding processes are already known in which heat input into the components to be welded occurs not only in the form of frictional heat from the rotation of the stirring pin of the friction stir welding tool, but also through conductive resistance heating using electrical energy. In this process, electrical energy is introduced into the components to be welded via the rotating stirring pin and / or the shoulder of the friction stir welding tool and, in particular, dissipated again via the component clamping device, thus creating a closed circuit with an electrical energy source. Such friction stir welding with additional conductive resistance heating is also referred to as EFSW welding (Electrically Assisted Friction Stir Welding).

[0006] CN 101 323 054 A, for example, describes an EFSW welding process in which the friction stir welding method is characterized by the fact that, during friction stir welding, an electric current is directed towards the weld seam of the workpiece, and the current and the contact resistance of the weld seam and the friction stir welding zone through which the current flows generate resistance heat. The resistance heat and the friction stir heat form a combined heat source for the friction stir welding, thus realizing the EFSW welding process.

[0007] Specifically, such an EFSW welding process can also be performed with the shoulder of the friction stir welding tool stationary. This type of friction stir welding with a stationary shoulder and additional conductive resistance heating is also referred to as ESSFSW welding (Electrically Assisted Stationary Shoulder Friction Stir Welding). Such an ESSFSW welding process is mentioned, for example, in CN 112 247 337 A.

[0008] DE 10 2021 121 367 describes a welding device and a welding process in which a friction stir welding tool is automatically guided by a robot. In the welding device described therein for friction stir welding of workpieces with different melting and plasticizing temperatures, the welding device consists of a welding tool with a driven and moving, in particular rotating, welding element and a detection device. The detection device is configured to detect frictional contact between the welding element and the workpiece with the higher melting point at the welding point during the welding process. The detection device includes a thermoelectric measuring device that detects frictional contact between the welding element and the workpiece with the higher melting point by measuring the friction temperature, in particular a change in the friction temperature, on the workpieces.

[0009] The object of the invention is to provide a method for producing a weld seam using a robot-guided friction stir welding tool with a stationary shoulder along a joint of a butt joint of a first component and a second component, which can perform an improved ESSFSW welding process with reduced process contact forces.

[0010] The problem is solved by a method for producing a weld seam using a robot-guided friction stir welding tool with a stationary shoulder along a joint of a butt joint of a first component and a second component, comprising the steps:

[0011] - Immersion of a stirring pin of the friction stir welding tool into the first component and / or into the second component with an immersion pressure directed in the rotational axis direction of the stirring pin towards the first component and / or towards the second component, in order to plasticize component material in a plasticization zone in the area of ​​the joint into a plasticized material, until the stationary shoulder of the friction stir welding tool rests against the first component and / or the second component,

[0012] - during automatic movement of the friction stir welding tool along the joint by automatically controlling a robot guiding the friction stir welding tool, applying a predetermined process contact force of the friction stir welding tool to the first component and / or to the second component,

[0013] - During the automatic movement of the friction stir welding tool along the joint, by automatically controlling the robot that guides the friction stir welding tool, additional process heat is generated in the area of ​​the plasticized material through conductive resistance heating using electrical energy, in addition to the process heat introduced into the plasticized material by friction through the rotation of the stirring pin of the friction stir welding tool.

[0014] - Automatic detection of a physical quantity characterizing the actual temperature in the area of ​​the plasticized material, - Reduction of the process contact force of the friction stir welding tool on the first component and / or on the second component by controlling the robot that guides the friction stir welding tool,

[0015] - Automatic increase of the input of supplementary process heat in the area of ​​the plasticized material by increasing the conductive resistance heating by increasing the input of electrical energy, such that the actual temperature of the plasticized material remains within a predetermined target temperature range.

[0016] There can be various reasons, even apart from simply parameterizing the process contact forces to optimize the process parameters for achieving high weld quality, that make it desirable to be able to reduce the process contact forces.

[0017] For example, relatively high process contact forces result in the rotating stir pin of the friction stir welding tool wearing out relatively quickly and therefore needing to be replaced more often. If a long service life is required for the rotating stir pin of the friction stir welding tool, it would be advantageous to reduce the process contact forces.

[0018] Especially with robot-guided friction stir welding tools, there may be a requirement that the process contact forces do not exceed a maximum permissible value. This is because, compared to friction stir welding tools guided by gantry systems or gantry robots, for example, very high process contact forces cannot be exerted on the friction stir welding tool. Gantry systems, for instance, can transmit process contact forces of approximately 20 to 50 kN, whereas robot arms, especially articulated robots with serial kinematics, can only transmit process contact forces of up to approximately 10 kN. Furthermore, with friction stir welding tools guided by articulated robots with serial kinematics, different maximum process contact forces can be transmitted depending on the axis configuration.Thus, in a relatively compact axis configuration of the robot arm, higher maximum process contact forces can be transmitted than in extended axis configurations, where the friction stir welding tool is located in a working space position far from the base frame of the robot arm.

[0019] Reducing the process contact forces during machining can also be advantageous, for example if one or both of the components to be welded have sections of lower component stiffness along the weld joint, such as due to differences in thickness or if the components have gaps or material thinnings on the back side along the weld, for example between ribs or other stiffeners to be formed on the back.

[0020] Reducing the process contact forces can also be advantageous if, in a weld seam being formed, a higher feed rate of the stirring pin is required or necessary in certain sections. The inventive method uses a friction stir welding tool that has a stationary shoulder. Accordingly, the stationary shoulder does not rotate with the stirring pin, but remains at least essentially stationary relative to the components to be welded. However, it is possible to reorient the stationary shoulder, for example, if the weld joint is not straight but has a curved section and the stationary shoulder is to remain in the same orientation relative to the weld seam.

[0021] The stationary shoulder covers the plasticizing zone from above along the entire weld seam. With its respective contour shape, the stationary shoulder thus forms the surface of the resulting weld seam. The stationary shoulder contacts the first component and / or the second component during the automatic movement of the friction stir welding tool or during the automatic movement of the rotating stir pin of the friction stir welding tool along the joint to be welded, and transmits a portion of the process contact forces to the first component and / or the second component.

[0022] The robot can comprise a robot arm and a robot controller. The robot controller is designed and configured to adjust the joints of the robot arm automatically or manually, thus changing the joint angle configuration of the robot arm's joints and moving the tool flange along a planned path to guide the friction stir welding tool to form a weld along the joint of the first and second components. The generation of supplementary process heat in the area of ​​the plasticized material through conductive resistance heating using electrical energy, in addition to the process heat introduced into the plasticized material by friction from the rotating stir pin of the friction stir welding tool, is achieved by conductively introducing electrical energy into the first and / or second component via the stationary shoulder.The standing shoulder is therefore made of an electrically conductive material, i.e., a metallic material.

[0023] In the inventive method, by automatically increasing the input of supplementary process heat in the area of ​​the plasticized material by increasing the conductive resistance heating, such that the actual temperature of the plasticized material remains within a predetermined target temperature range, the process contact force of the friction stir welding tool or the process contact force of the rotating stir pin of the friction stir welding tool can be reduced without disturbing the plasticization of the material required for weld formation.

[0024] The automatic increase of the input of supplementary process heat in the area of ​​the plasticized material by increasing the conductive resistance heating, by increasing the input of electrical energy, such that the actual temperature of the plasticized material remains within a predetermined target temperature range, thus occurs depending on the reduction of the process contact force of the friction stir welding tool on the first component and / or on the second component by controlling the robot that guides the friction stir welding tool.

[0025] If the process contact force of the friction stir welding tool on the first component and / or on the second component is increased again during the further course of the weld seam production by controlling the robot that guides the friction stir welding tool, the input of additional process heat in the area of ​​the plasticized material through conductive resistance heating can be reduced again within the framework of the control of the welding process, namely by reducing the input of electrical energy, whereby the actual temperature of the plasticized material can continue to be kept within a specified target temperature range.

[0026] In a first variant of the process, the actual temperature of the plasticized material can be automatically recorded immediately before the plasticization zone, immediately after the plasticization zone and / or in the plasticization zone using at least one temperature sensor.

[0027] Temperature measurement can be performed at specific points, leading, trailing, or laterally to the stationary shoulder of the friction stir welding tool. Temperature fields or gradients also optionally allow for predictive control, meaning that events can be predicted and countermeasures can be applied before the event occurs to prevent it from happening in the first place.

[0028] One possibility is to use a thermal imaging camera for data acquisition. In this case, temperature fields, temperature gradients, and especially point-based data acquisitions can be defined. Alternatively or additionally to the first option, if an automatically detected increase in the actual temperature would lead to exceeding a predefined maximum value of the target temperature range if the increased electrical energy input during the automatic movement of the friction stir welding tool along the joint were maintained, the electrical energy input in the area of ​​the plasticized material can be reduced again, such that the actual temperature of the plasticized material remains within a predefined target temperature range.

[0029] Since the change in the actual temperature in the plasticization zone is rather slow, model predictive control can be used instead of direct control via the current actual temperature as the reference variable.

[0030] In a second variant of the process, the actual temperature of the plasticized material can be determined indirectly, based on an automatic measurement of the torque applied to the rotating stirring stick.

[0031] The torque required to maintain the specified rotational speed of the stirring pin is directly related to the instantaneous temperature in the plasticizing zone. An increase in the temperature in the plasticizing zone, while maintaining the specified rotational speed, results in a decrease in the torque required at the rotating stirring pin.

[0032] Determining the actual temperature of the plasticized material by automatically measuring the torque applied to the rotating stirring stick is easier to perform using sensors, and changes in the torque curve are detected more quickly than temperature increases in the vicinity of the plasticization zone, since heat conduction through the material is generally slower than spontaneous changes in the torque curve directly in the plasticization zone.

[0033] The automatic measurement of the torque applied to the rotating stirring stick can be carried out directly, for example, by means of torque sensors that are arranged in the drive train between the drive motor and the rotating stirring stick.

[0034] In the second variant of the process, the friction stir welding tool can optionally have a drive motor that rotates the stirring pin of the friction stir welding tool. The drive motor of the friction stir welding tool can be automatically controlled by a process controller, and the torque generated by the drive motor and acting on the rotating stirring pin can be determined indirectly from at least one control variable of the process controller that controls the drive motor. The process controller can be a component of the robot controller. Alternatively, the process controller can be a separate control device from the robot controller.

[0035] For example, the current draw of the drive motor can be electrically measured and evaluated. The current draw of the drive motor is directly proportional to the transmitted torque. Therefore, the torque at the stirring stick can be measured by measuring the current draw of the drive motor. This current draw can be measured electrically by the robot controller without the need for dedicated torque sensors.

[0036] By automatically detecting an increase in the torque acting on the rotating stirring pin, the input of electrical energy in the area of ​​the plasticized material can be increased during the automatic movement of the friction stir welding tool along the joint.

[0037] At process-optimal temperatures in the plasticization zone, sufficient, i.e., optimal, plasticization of the material occurs. However, if the torque acting on the rotating stirrer pin increases during its movement along the joint to be welded, this indicates that the material adheres too strongly to the rotating stirrer pin and cannot be sufficiently guided around it. This is therefore an indication of insufficient plasticization of the material in the plasticization zone. Accordingly, increasing the temperature in the plasticization zone can further plasticize the material, thereby reducing the torque required to rotate the stirrer pin at the specified speed.According to the inventive method, such an increase in temperature is achieved by increasing the input of supplementary process heat in the area of ​​the plasticized material by increasing the conductive resistance heating.

[0038] If the torque acting on the rotating stirring pin is automatically detected, the input of electrical energy in the area of ​​the plasticized material can then be reduced again if necessary during the automatic movement of the friction stir welding tool along the joint.

[0039] In a third variant of the process, the actual temperature of the plasticized material can be determined indirectly, based on an automatic measurement of the feed force applied to the rotating stirring stick.

[0040] Determining the actual temperature of the plasticized material by automatically measuring the feed force acting on the rotating stirring stick is easier to perform using sensors, and changes in the feed force are detected more quickly than temperature increases in the vicinity of the plasticization zone, since heat conduction through the material is generally slower than spontaneous changes in the feed force on the stirring stick.

[0041] The automatic measurement of the feed force acting on the rotating stirring pin can be carried out directly, for example, by means of force sensors that are arranged in the area of ​​the bearing of the rotating stirring pin.

[0042] Alternatively, a force transducer can be inserted between the friction stir welding tool and the robot's tool flange, allowing the forces transmitted by the robot to the friction stir welding tool to be measured, for example, in the X, Y, and Z directions. By general definition, the forces in the X direction are the feed forces, the forces in the Z direction are the process contact forces, and the forces in the Y direction are the transverse forces acting on the stir pin, perpendicular to the feed direction.In the third variant of the method, the friction stir welding tool can optionally be guided by a robot arm force / torque controlled by a robot control in a force / torque controlled operating mode, and the feed force applied to the rotating stir pin can be determined from at least one control variable of the robot control that controls the joint drives of joints of the robot arm and / or from sensor values ​​of joint sensors of the robot arm.

[0043] In this specific implementation, the torque values ​​in all axis joints of the robot arm can be used to calculate the resulting forces at the tool flange of the robot arm, depending on the current axis position configuration. Instead of using separate joint sensors, the individual torques in the axis joints of the robot arm can also be determined from the drive torques of the individual joint drives of the robot arm. These instantaneous values ​​of the drive torques of the individual joint drives are available to the robot controller as control variables, for example, in the form of electrical current consumption, and therefore do not need to be measured separately.

[0044] Alternatively or additionally, by automatically detecting an increase in the feed force applied to the rotating stirring pin during the automatic movement of the friction stir welding tool along the joint, the input of electrical energy in the area of ​​the plasticized material can be increased.

[0045] The feed force, at a given feed rate, adjusts itself depending on the resistance of the insufficiently plasticized material. If the material in the plasticization zone is not yet sufficiently plasticized, the feed force is comparatively high. A very high feed force, in this respect, indicates an insufficient temperature in the plasticization zone. Accordingly, as the feed force increases during the automatic movement of the rotating stirring pin along the joint, the temperature in the plasticization zone must be increased. According to the inventive method, this temperature increase is achieved by further increasing the input of supplementary process heat in the area of ​​the plasticized material through an increase in conductive resistance heating.

[0046] By automatically detecting a reduction in the feed force applied to the rotating stirring pin during the automatic movement of the friction stir welding tool along the joint, the input of electrical energy in the area of ​​the plasticized material can be reduced again.

[0047] In a fourth variant of the method, a change in the actual temperature of the plasticized material can be determined indirectly, based on a change in the position of the stationary shoulder of the friction stir welding tool in the direction of the process contact force during the automatic movement of the friction stir welding tool along the joint at a constant process contact force.

[0048] A change in the position of the stationary shoulder in the direction of the process pressure force represents a deviation of the current actual position of the stationary shoulder in the direction of the process pressure force from the target position of the stationary shoulder in the direction of the process pressure force, which determines the desired process pressure force. Determining the actual temperature of the plasticized material by automatically measuring the current actual position of the stationary shoulder is simpler from a sensor technology perspective, and changes in the current actual position of the stationary shoulder are detected more quickly than temperature increases in the vicinity of the plasticizing zone, since heat conduction through the material is generally slower than the spontaneous changes in the feed force on the stirring pin.

[0049] The automatic measurement of the current actual position of the standing shoulder can be carried out directly, for example, using position sensors that are arranged in the area of ​​the standing shoulder.

[0050] In the fourth variant of the method, the friction stir welding tool can optionally be guided by a robot arm force / torque controlled by a robot controller in a force / torque controlled operating mode, and the change in the position of the stationary shoulder of the friction stir welding tool can be determined during the automatic movement of the friction stir welding tool along the joint with a constant target process contact force from at least one control variable of the robot controller that controls the joint drives of joints of the robot arm and / or from sensor values ​​of joint sensors of the robot arm.

[0051] Instead of measuring the change in position of the stationary shoulder of the friction stir welding tool, the actual process contact force applied via the stationary shoulder can also be used. If the actual process contact force applied via the stationary shoulder into the first component and / or the second component begins to deviate from the desired target process contact force, this can indicate a change in the position of the stationary shoulder of the friction stir welding tool. If the material in the plasticization zone yields too much due to the actual process contact force applied via the stationary shoulder, and the stationary shoulder sinks more than expected into the first component and / or the second component, this indicates excessive plasticization of the material, i.e., it suggests an excessively high temperature in the plasticization zone.If, however, the material in the plasticization zone remains too stiff during an actual process contact force introduced via the standing shoulder, and the standing shoulder does not sink into the first component and / or the second component to the expected extent, this suggests insufficient plasticization of the material, i.e., this suggests a temperature that is too low in the plasticization zone.

[0052] If the stationary shoulder does not sink to the expected extent during the automatic movement of the friction stir welding tool along the joint, but less than expected, the temperature in the plasticization zone is increased. According to the inventive method, this temperature increase is achieved by increasing the input of supplementary process heat in the area of ​​the plasticized material through an increase in conductive resistance heating.

[0053] However, if the stationary shoulder sinks more than expected during the automatic movement of the friction stir welding tool along the joint, the temperature in the plasticizing zone is reduced. According to the inventive method, this temperature reduction is achieved by reducing the input of additional process heat in the area of ​​the plasticized material by decreasing the conductive resistance heating.

[0054] Thus, if the position of the stationary shoulder is automatically detected in the opposite direction to the process pressure directed towards the first component and / or the second component, moving away from the first component and / or the second component during the automatic movement of the friction stir welding tool along the joint, the input of electrical energy in the area of ​​the plasticized material can be increased.

[0055] However, if the position of the stationary shoulder is automatically detected in the direction of the process contact force directed towards the first component and / or the second component during the automatic movement of the friction stir welding tool along the joint, the input of electrical energy in the area of ​​the plasticized material can be reduced again.

[0056] In all variants of the process, the reduction of the process contact force of the friction stir welding tool on the first component and / or on the second component can also be carried out automatically by controlling the robot that guides the friction stir welding tool, by force / torque controlled control of a robot arm of the robot, to whose tool flange the friction stir welding tool is attached, by means of a robot controller of the robot.The problem is also solved by a friction stir welding device for carrying out a method according to one of the described embodiments, comprising a robot arm with several links and the links automatically adjustable joints relative to each other, wherein the joints are adjustable by electric motors which are controlled automatically by a robot controller or in a manual operation, wherein the robot arm has a tool flange to which a friction stir welding tool is attached, so that by controlling the joints of the robot arm by the robot controller the friction stir welding tool can be controlled and moved according to a method according to one of the described embodiments.

[0057] Furthermore, the task is also solved by a computer program product comprising a machine-readable carrier on which program code is stored, which can be read by a robot controller of a robot that guides a friction stir welding tool and which trains and / or sets up the robot controller to carry out a procedure according to one or more implementations as described when the program code is executed by the robot controller.

[0058] The computer program product can be, for example, a CD, a DVD, or a USB flash drive. It can also be a control board with integrated microprocessors. Alternatively, the computer program product can be implemented as a download, which can be offered and sold via the internet or another network. The machine-readable medium can therefore be a CD, a DVD, or a microprocessor on which the program code is stored. However, the machine-readable medium can also be a hard drive or an SSD onto which the program code has been downloaded, for example, via a download, particularly in the form of data packets.

[0059] The program code can be represented by an edited program and / or data stored on the machine-readable medium.

[0060] By reading the edited program and / or the data, the reading robot control is trained and / or set up to be able to execute the inventive method by controlling the robot arm to move the friction stir welding tool accordingly.

[0061] The method according to the invention is carried out when the robot control actually executes the program code, i.e. the edited program, accordingly and / or actually processes the data accordingly.

[0062] Specific embodiments of the invention are explained in more detail in the following description with reference to the accompanying figures. Specific features of these exemplary embodiments can, regardless of the specific context in which they are mentioned, and optionally also individually or in further combinations, represent general features of the invention.

[0063] Figure 1 shows a flowchart of the steps in the basic method according to the invention.

[0064] Fig. 2 shows a schematic representation of an exemplary friction stir welding device according to the invention, comprising a robot controller, a robot arm controlled by the robot controller, and a friction stir welding tool guided by the robot arm.

[0065] Fig. 3 shows a diagram of an exemplary, principle-based automatic control of current density during the automatic increase of the input of supplementary process heat in the area of ​​the plasticized material by increasing the conductive resistance heating as a function of the directly measured actual temperature of the plasticized material.

[0066] Fig. 4 shows a diagram of an exemplary, principle-based automatic control of current density during the automatic increase of the input of supplementary process heat in the area of ​​the plasticized material by increasing the conductive resistance heating as a function of the applied feed force and as a function of the torque acting on the rotating stirring stick, and

[0067] Fig. 5 shows a diagram of an exemplary, principle-based automatic control of current density during the automatic increase of the input of supplementary process heat in the area of ​​the plasticized material by increasing the conductive resistance heating as a function of the change in the position of the stationary shoulder of the friction stir welding tool.

[0068] Fig. 1 illustrates a process for producing a weld seam using a robot-guided friction stir welding tool 8 with a stationary shoulder 9 along a joint 10 of a butt joint of a first component 11 and a second component 12 as a flow diagram.

[0069] In a first step S1 of the process, a stirring pin 13 of the friction stir welding tool 8 is immersed into the first component 11 and / or into the second component 12 with an immersion pressure directed in the rotational axis direction of the stirring pin 13 towards the first component 11 and / or the second component 12 in order to plasticize component material in a plasticization zone in the area of ​​the joint 10 until the stationary shoulder 9 of the friction stir welding tool 8 rests against the first component 11 and / or the second component 12.

[0070] In a second step S2 of the process, during automatic movement of the friction stir welding tool 8 along the joint 10, a predetermined process contact force of the friction stir welding tool 8 is applied to the first component 11 and / or to the second component 12 by automatically controlling a robot 2a guiding the friction stir welding tool 8.

[0071] In a third step S3 of the process, during the automatic movement of the friction stir welding tool 8 along the joint 10, an additional process heat is generated in the area of ​​the plasticized material by means of conductive resistance heating using electrical energy, in addition to the process heat introduced into the plasticized material by friction in the form of frictional heat by the rotation of the stirring pin 13 of the friction stir welding tool 8.

[0072] In a fourth step S4 of the process, a physical quantity characterizing the actual temperature in the area of ​​the plasticized material is automatically recorded.

[0073] In a fifth step S5 of the process, the process contact force of the friction stir welding tool 8 on the first component 11 and / or on the second component 12 is reduced by controlling the robot 2a, which guides the friction stir welding tool 8.

[0074] In a sixth step S6 of the process, the input of supplementary process heat in the area of ​​the plasticized material is automatically increased by increasing the conductive resistance heating by increasing the input of electrical energy, such that the actual temperature of the plasticized material remains within a predetermined target temperature range.

[0075] Fig. 2 shows a friction stir welding device 1 for carrying out a method according to one of the described embodiments, comprising a robot arm 2 with several links 3 and the links 3 automatically adjustable joints 4 relative to each other, wherein the joints 4 are adjustable by electric motors 5 which are controlled automatically or manually by a robot controller 6, wherein the robot arm 2 has a tool flange 7 to which a friction stir welding tool 8 is attached, so that by controlling the joints 4 of the robot arm 2 by the robot controller 6 the friction stir welding tool 8 can be controlled and moved according to a method according to one of the described embodiments.

[0076] The friction stir welding tool 8 comprises a drive motor 14, which is designed and configured to rotate the stir pin 13. Furthermore, an electrical resistance welding generator 15 is connected to the stationary shoulder 9, through which electrical energy can be introduced into the stationary shoulder 9 and consequently into the first component 11 and / or the second component 12. The resistance welding generator 15 can either be part of the friction stir welding tool 8 and thus be carried along when the friction stir welding tool 8 is automatically moved by the robot arm 2, or the resistance welding generator 15 can be arranged separately from the friction stir welding tool 8 and thus be positioned in a stationary position.

[0077] Fig. 2 illustrates the stirring pin 13 in an axial position before it is immersed in the first component 11 and / or the second component 12, so that the stirring pin 13 is also visible in Fig. 2. Therefore, the stationary shoulder 9 does not yet contact the first component 11 and / or the second component 12. However, during the welding process, the stationary shoulder 9 rests against the first component 11 and / or the second component 12 from above.

[0078] In the embodiment shown in Fig. 2, the first component 11 and / or the second component 12 are shown in a butt joint arrangement, in which two opposing end faces of the first component 11 and the second component 12 are at least largely flush with each other in the area of ​​the joint 10. The first component 11 and the second component 12 are held in position by clamping means 16 and are placed on a clamping table 17.

[0079] Figure 3 shows a diagram of an exemplary, principle-based automatic control of a current density S during the automatic increase of the input of supplementary process heat in the area of ​​the plasticized material by increasing the conductive resistance heating as a function of the actual temperature T of the plasticized material.

[0080] The actual temperature of the plasticized material can be automatically recorded immediately before the plasticization zone, immediately after the plasticization zone and / or in the plasticization zone using at least one temperature sensor.

[0081] If the actual temperature T is automatically detected and would lead to an exceedance of a predetermined maximum value of the target temperature range while maintaining the increased input of electrical energy during the automatic movement of the friction stir welding tool 8 along the joint 10, the input of electrical energy (current density S) in the area of ​​the plasticized material can be reduced again, such that the actual temperature T of the plasticized material remains within a predetermined target temperature range.

[0082] In the diagram of Fig. 3, the current density is shown as a reference variable, once resulting from the empirically determined relationship (emp) to the actual temperature T and once resulting from the simulation (sim) determined relationship to the actual temperature T.

[0083] The relationship can be linear, quadratic, or similar. The latter is more likely, since the influence of the current on the joules of heat is semantically quadratic.

[0084] However, the temperature difference between both sides of a butt or lap joint can be used. For example, the average of both temperatures or the temperature of one side can be used as a higher-level parameter. Additionally, event-driven path control is possible.

[0085] Figure 4 shows a diagram of an exemplary, principle-based automatic control of the current density S during the automatic increase of the input of supplementary process heat in the area of ​​the plasticized material by increasing the conductive resistance heating as a function of the applied feed force F. xand shown as a function of the torque M acting on the rotating stirring pin 13. The actual temperature T of the plasticized material can be determined indirectly, based on an automatic measurement of the torque M applied to the rotating stirring pin 13 or the feed force F. x .

[0086] In the diagram of Fig. 4, the current density S is used as a reference variable, resulting from the empirically or by simulation-determined relationship to the feed force F. x and moment M represented.

[0087] The relationship can be linear, quadratic, or similar. The latter is more likely, since the influence of the current on the joules of heat is logically quadratic.

[0088] Fig. 5 shows a diagram of an exemplary, principle-based automatic control of a current density S during the automatic increase of the input of supplementary process heat in the area of ​​the plasticized material by increasing the conductive resistance heating as a function of the change in the position of the stationary shoulder 9 of the friction stir welding tool 8.

[0089] The change in the actual temperature T of the plasticized material can be determined indirectly, based on a change in the position Z of the stationary shoulder 9 of the friction stir welding tool 8 in the direction of the process contact force during the automatic movement of the friction stir welding tool 8 along the joint 10 at a constant process contact force.

[0090] In the diagram according to Fig. 5, the current density S is shown as the reference variable, resulting from the empirically or by simulation-determined relationship to the sinking of the standing shoulder 9. The relationship can be linear, quadratic, or similar. The latter is more likely, since the influence of the current on the joules of heat is logically quadratic.

Claims

Patent claims 1. Method for producing a weld seam using a robot-guided friction stir welding tool ( 8 ) with a stationary shoulder ( 9 ) along a joint ( 10 ) of a butt joint of a first component ( 11 ) and a second component ( 12 ), comprising the steps: - Immersion of a stir pin (13) of the friction stir welding tool (8) into the first component (11) and / or into the second component (12) with an immersion pressure directed in the rotational direction of the stir pin (13) towards the first component (11) and / or the second component (12) in order to plasticize component material in a plasticizing zone in the area of ​​the joint (10) to a plasticized material, until the stationary shoulder (9) of the friction stir welding tool (8) rests against the first component (11) and / or the second component (12), - during automatic movement of the friction stir welding tool ( 8 ) along the joint ( 10 ) by automatically controlling a robot ( 2a ) guiding the friction stir welding tool ( 8 ), applying a predetermined process contact force of the friction stir welding tool ( 8 ) to the first component ( 11 ) and / or to the second component ( 12 ), - during the automatic movement of the friction stir welding tool ( 8 ) along the joint ( 10 ) by automatically controlling the robot ( 2a ) , which the friction stir welding tool ( 8 ) generates additional process heat in the area of ​​the plasticized material by conductive resistance heating using electrical energy, in addition to the process heat introduced into the plasticized material by friction through the rotation of the stirring pin ( 13) of the friction stir welding tool ( 8 ). - automatic detection of a physical quantity that characterizes the actual temperature in the area of ​​the plasticized material, - Reducing the process contact force of the friction stir welding tool ( 8 ) on the first component ( 11 ) and / or on the second component ( 12 ) by controlling the robot (2a) which guides the friction stir welding tool ( 8 ), - automatic increase of the input of supplementary process heat in the area of ​​the plasticized material by increasing the conductive resistance heating by increasing the input of electrical energy, such that the actual temperature (T) of the plasticized material remains within a predetermined target temperature range.

2. Method according to claim 1, characterized in that the actual temperature (T) of the plasticized material is measured immediately before the plasticization zone, immediately after the plasticization zone and / or in the The plasticization zone is automatically detected by means of at least one temperature sensor.

3. Method according to claim 1 or 2, characterized in that, in the event of an automatically detected increase in the actual temperature (T), which would lead to an exceedance of a predetermined maximum value of the target temperature range if the increase in the input of electrical energy is maintained during the automatic movement of the friction stir welding tool ( 8 ) along the joint ( 10 ), the input of electrical energy in the area of ​​the plasticized material is reduced again, such that the actual temperature (T) of the plasticized material remains within a predetermined target temperature range.

4. Method according to claim 1, characterized in that the actual temperature (T) of the plasticized material is determined indirectly, on the basis of an automatic measurement of the torque applied to the rotating stirring stick ( 13 ).

5. Method according to claim 4, characterized in that the friction stir welding tool (8) has a drive motor (14) which rotates the stirring pin (13) of the friction stir welding tool (8), the drive motor (14) of the friction stir welding tool (8) is automatically controlled by a process control system, and the torque (M) generated by the drive motor (14) and acting on the rotating stirring pin (13) is used to indirectly determine the actual temperature (T) of the plasticized material from at least one of the drive motors. ( 14) controlling variable of the process control is determined.

6. Method according to claim 4 or 5, characterized in that, when the torque (M) acting on the rotating stir pin (13) is automatically detected during the automatic movement of the friction stir welding tool (8) along the joint, the input of electrical energy in the area of ​​the plasticized material is increased and / or when the torque (M) acting on the rotating stir pin (13) is automatically detected during the automatic movement of the friction stir welding tool (8) along the joint (10), the input of electrical energy in the area of ​​the plasticized material is reduced again.

7. Method according to claim 1, characterized in that the actual temperature (T) of the plasticized material is determined indirectly, on the basis of an automatic measurement of the feed force (Ex) applied to the rotating stirring stick ( 13 ).

8. Method according to claim 7, characterized in that the friction stir welding tool ( 8 ) is guided by a robot arm (2 ) force / torque controlled by a robot controller ( 6) in a force / torque controlled operating mode and the feed force (Ex) applied to the rotating stir pin ( 13) is determined from at least one control variable of the robot controller ( 6) controlling the joint drives (5) of joints (4 ) of the robot arm (2 ) and / or from sensor values ​​of joint sensors of the robot arm (2 ).

9. Method according to claim 7 or 8, characterized in that, when the feed force (Fx) applied to the rotating stir pin (13) is automatically detected during the automatic movement of the friction stir welding tool (8) along the joint (10), the input of electrical energy in the area of ​​the plasticized material is increased and / or when the feed force (Fx) applied to the rotating stir pin (13) is automatically detected during the automatic movement of the friction stir welding tool (8) along the joint (10), the input of electrical energy in the area of ​​the plasticized material is reduced again.

10. Method according to claim 1, characterized in that a change in the actual temperature (T) of the plasticized material is determined indirectly, based on a change in the position of the stationary shoulder (9) of the friction stir welding tool (8) in the direction of the process contact force during the automatic movement of the friction stir welding tool (8) along the joint (10) at a constant process contact force.

11. Method according to claim 10, characterized in that the friction stir welding tool (8) is guided by a robot arm (2) force / torque controlled by a robot controller (6) in a force / torque controlled operating mode and the change in the position of the stationary shoulder (9) of the friction stir welding tool (8) during the automatic movement of the friction stir welding tool (8) along the joint (10) at a constant target value The process contact force is determined from at least one control variable of the robot control (6) controlling the joint drives (5) of joints (4) of the robot arm (2) and / or from sensor values ​​of joint sensors of the robot arm (2).

12. The method according to claim 10 or 11, characterized in that, upon an automatically detected change in the position of the stationary shoulder (9) opposite to the direction of the process contact force directed towards the first component (11) and / or the second component (12), away from the first component (11) and / or the second component (12), during the automatic movement of the friction stir welding tool (8) along the joint (10), the input of electrical energy in the area of ​​the plasticized material is increased, and / or upon an automatically detected change in the position of the stationary shoulder (9) towards the first component (11) and / or the second component (12), during the automatic movement of the friction stir welding tool (8) along the joint (10). ) ,the input of electrical energy in the area of ​​the plasticized material is reduced again.

13. Method according to one of claims 1 to 12, characterized in that the reduction of the process contact force of the friction stir welding tool (8) on the first component (11) and / or on the second component (12) is achieved by controlling the robot (2a) which guides the friction stir welding tool (8) by force / torque-controlled control of a robot arm (2) of the The welding process is carried out automatically by means of a robot control (6) of the robot (2a) on the tool flange (7) of which the friction stir welding tool (8) is attached.

14. Friction stir welding device for carrying out a method according to one of claims 1 to 13, comprising a robot arm (2 ) with several links (3) and the links (3) automatically adjustable joints (4 ) relative to each other, wherein the joints (4 ) are adjustable by electric motors (5) which are controlled automatically or manually by a robot controller (6), wherein the robot arm (2 ) has a tool flange (7 ) to which a friction stir welding tool (8 ) is attached, so that by controlling the joints (4 ) of the robot arm (2 ) by the robot controller (6) the friction stir welding tool (8 ) can be controlled and moved according to a method according to one of claims 1 to 13.

15. Computer program product comprising a machine-readable carrier on which program code is stored, which is readable by a robot controller (6) of a robot (2a) which guides a friction stir welding tool (8) and which forms and / or sets up the robot controller (6) to carry out a method according to one of claims 1 to 13 when the program code is executed by the robot controller (6).

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