Method for shape correction of an assembly

Abstract

The invention relates to a method for shape correction of an assembly (1), in particular a sheet metal assembly, which is formed from at least two planar components (2), in particular formed sheet metal components, each made from at least one flat semi-finished product. In this process, by means of at least one forming step, the overall actual shape (3) of the assembly (1), which exhibits a shape deviation outside specified tolerances from an overall target shape (4), is brought at least into conformity with the target shape (4) such that the actual shape (3) lies within specified tolerances. This is achieved by bringing an effector (5) into point contact with the assembly (1) in each forming step and deforming the assembly (1) by a relative movement of the effector (5) and the assembly (1) such that the shape deviation resulting from the respective forming step is at least minimized.

Description

[0001] The invention relates to a method for shape correction of an assembly, in particular a sheet metal assembly, which is formed from at least two planar components, in particular formed sheet metal components, each made from at least one flat semi-finished product. In this process, by means of at least one forming step, the overall actual shape of the assembly, which exhibits a shape deviation from the overall target shape that lies outside specified tolerances, is brought into conformity with the target shape at least to such an extent that the actual shape lies within specified tolerances.

[0002] In car body manufacturing, clamping devices are regularly used to precisely fix individual body panels during assembly into body components, such as vehicle doors. To compensate for dimensional deviations of the body panels that occur during production and to ensure that the assembled body components meet specified tolerances, shims, also called shims or spacers, are placed between the clamping device and the body panels. These shims force the body panels into the desired shape, so that the assembled body component meets the required tolerances after assembly.

[0003] These shims can have different thicknesses and be used in various combinations to compensate for the previously determined shape deviation of the body panels, which can also vary depending on the joining process.

[0004] A disadvantage of such clamping devices, when using shims, is that they can over-constrain the body assembly, potentially leading to residual stresses and subsequent deformations. Furthermore, inserting and adjusting shims is generally a manual process, which can slow down production and increase costs. Any correction to a body assembly requires careful inspection and adjustment, which can negatively impact production efficiency. If a clamping device cannot accommodate the specific dimensional deviations of the sheet metal used to assemble a body assembly, there is a risk that geometrically correct body assemblies, already within tolerance, will be forced into a shape that exhibits an unacceptable deviation.

[0005] Solutions to address these problems, at least in part, are already known from the state of the art.

[0006] German patent DE 10 2011 116 808 A1 discloses a semi- or fully automatic clamping device with multiple clamping units for holding a sheet metal component. The clamping device measures the sheet metal components and / or their positional deviations, calculates corresponding adjustment or clamping points, and specifies adjustment values ​​or target positions for these clamping points, including, in particular, the positions of the adjustment means associated with the clamping units. These adjustment means displace a clamped component within the clamping unit. The clamping units consist of clamps with a clamping element and a clamping point, adjustable via adjustment cylinders. Several of these clamps can be controlled by a common electro-hydraulic drive, which is part of a semi- or fully automatic control system.The adjusting cylinders allow the clamping element to be adjusted in three spatial axes, while the clamping point is preferably positioned in two spatial axes.

[0007] DE 10 2007 002 320 A1 also describes a method and a clamping device for correcting the shape of a sheet metal part or assembly. This clamping device comprises a measuring device, at least one straightening device, a system control unit, a computer, an artificial neural network, a data storage unit, and a safety circuit control unit. The straightening device is equipped with straightening clamps and electrically controlled actuators. The system control unit also controls both the data acquisition by the measuring device and the actuators. For straightening, the sheet metal part or assembly is first placed in the straightening module, and the straightening clamps are closed. The sheet metal part or assembly is then measured by sensors of the measuring device to determine an initial measurement value, which is stored in the data storage unit.The system then moves to a current position, determines a setting for the actuators using an artificial neural network, and transmits this value to the machine control system. The straightening process is then carried out, during which the sheet metal part is overpressured using the straightening clamps. After straightening, the system moves to a target position, opens the straightening clamps, and releases the sheet metal part or assembly. The sheet metal part or assembly is then measured again. The new measurement is compared with the stored values ​​in the computer, and if a dimensional deviation is detected, the artificial neural network determines a new setting for the actuators. If no deviation is detected, the sheet metal part is removed from the system.

[0008] However, such solutions are disadvantageously highly complex, leading to high costs for the clamping devices, increased susceptibility to errors, and high maintenance costs.

[0009] Furthermore, the joining of the body panels to form the body assembly is largely achieved by welding, especially spot welding. Welding is, as is well known, a widely used joining process employed in a multitude of industries in a wide variety of forms.

[0010] EP 4 004 978 B1, for example, describes in an unrelated context the gap-free contacting of an electronic component via its terminals, where a free end of the terminals is bent towards a carrier of the electronic component. This allows for gap-free welding of the terminal and the terminal clip when a flat contacting partner, such as a connecting clip, is placed against it, even without a counter-support, since the necessary counterforce originates from the bending of the free end of the terminals. The gap-free state is achieved by applying force, e.g., by placing a welding mask on the terminal and connecting clip, and the terminal and connecting clip are then joined together by laser welding.

[0011] Furthermore, EP 1 414 610 B1 describes a method and a device for controlling an electric resistance welding gun, specifically used for welding workpieces, particularly car body shells. In this process, the workpieces and the welding gun are moved relative to each other by a robot. The welding gun is equipped with two movable arms, each carrying an electrode at its end and moved by a drive mechanism. Optimal resistance spot welding is achieved when the electrodes act on the workpiece, which typically consists of two or more layers of sheet metal, from both sides at the correct time, in the correct position, and with the correct force. The method establishes an optimal relative position between the welding gun and the workpiece by detecting the contact or distance between an electrode and the workpiece in a searching movement.After contact is established, the actual thickness of the sheet metal layers can also be measured. For this, the second electrode is moved by the welding gun drive until it makes contact with the component. With poor sheet metal fit or soft materials, the deviation from the theoretical sheet thickness is small, while it can be larger with rigid components and hard materials. In this case, too, the thickness of the sheet metal layers is measured at the weld point, and the drive is adjusted so that a gap between the sheet metal layers is closed. Due to the drive's control, the restoring force or stiffness of the sheet metal layers is irrelevant. The drive simply needs to be strong enough to overcome the resistance.

[0012] Furthermore, DE 683 411 C describes a method for joining sheet metal parts by deformation and electric spot or roller welding. The introduction explains that in conventional spot welding, the deformation of the sheet metal parts occurs simultaneously with the welding process. This is achieved by the electrodes of a spot welding machine, which are designed similarly to the punch and die of an embossing tool. This creates an annular weld at the edge of the shallow indentation produced in the sheet metal parts by the electrodes. However, such joints have disadvantages: If mechanical vibrations are transmitted through the joint, the material tends to fracture in the annular zone around the weld under the combined effect of the vibrational forces and the static forces to be transmitted, without the weld itself failing.As an improved alternative, it is proposed that the sheet metal parts be provided with indentations before welding using a tool consisting of a punch and die. One or more weld points are then placed in these indentations in such a way that the edge zones around the weld points, which are affected by the welding heat, do not expand beyond the bottom of the indentations.

[0013] Against this background, the invention is based on the objective of carrying out a method of the type mentioned at the outset in such a way that a shape correction of an assembly is made possible even without a complex clamping device and thus with reduced costs.

[0014] This problem is solved by a method according to the features of claim 1. The dependent claims relate to particularly advantageous further developments of the invention.

[0015] According to the invention, a method for shape correction of an assembly, in particular a sheet metal assembly, preferably a body assembly, is provided, wherein the assembly is formed from at least two planar components, in particular formed sheet metal components, preferably body panels. The components are each manufactured from at least one flat semi-finished product, in particular a sheet. Thus, it is provided that the components have already been processed by at least one manufacturing process, for example cutting and / or forming, and thereby have a basic shape that differs from that of a flat semi-finished product. Due to the manufacturing from a flat semi-finished product, the components have a significantly smaller thickness compared to the two other component dimensions and are therefore planar.The components are preferably joined together to form an assembly, for which purpose the components are at least placed against each other and, in particular, fixed relative to each other by means of a clamping device. The clamping device used for this purpose can have a comparatively simple design.

[0016] Furthermore, according to the invention, by means of at least one forming step, an overall actual shape of the assembly, which exhibits a deviation from the overall target shape that lies outside the specified tolerances, is brought into conformity with the target shape at least to such an extent that the actual shape lies within the specified tolerances. The at least one forming step thus adapts the actual shape of the assembly to the target shape. This enables a correction of the shape deviation so that the finished assembly conforms to the specified tolerances, thereby ensuring high quality and dimensional accuracy.

[0017] According to the invention, the actual shape is brought into conformity with the desired shape by engaging an effector at a specific point, i.e., in a point-like area, with the assembly in each forming step and deforming the assembly through a relative movement of the effector and the assembly, so that the shape deviation resulting from the respective forming step is at least minimized. By using an effector that is preferably designed as a robot-guided gripper, a robot-guided finger, for example, a robot-guided bolt, or a finger of a robot-guided gripper, the shape correction can advantageously be carried out without the use of a complex clamping device, especially one that would need to be adapted to a specific assembly, e.g., the doors or front of a vehicle body.The effector, preferably mounted on a robot, particularly an industrial robot, can be an existing piece of equipment already in place, for example, for further processes to be carried out on the assembly, so that no additional costs are incurred for shape correction. In principle, it could be provided that the shape deviation is eliminated in just one forming step, so that the actual shape of the assembly is within the specified tolerances. However, more than one forming step is preferably provided, and several forming steps are particularly preferred, in which the shape deviation is corrected or eliminated step by step, so that the actual shape of the assembly, as a result of a final forming step, is within the specified tolerances and thus essentially corresponds to the target shape of the assembly.

[0018] In an advantageous embodiment of the invention, the effector is engaged at a predetermined position on the assembly, particularly for each forming step. Further elaborating on this, the position depends on the shape deviation. In this way, the shape correction can advantageously be carried out taking into account the shape features or geometric features of the target shape of the assembly, for example, according to a test feature plan. For this purpose, the shape deviation of the assembly is preferably determined at at least one position, but preferably at several positions of the assembly, and corrected accordingly at the position or positions. In the case of multiple positions, the correction is preferably carried out in at least one forming step per position.Furthermore, targeted correction at predetermined positions depending on the shape deviation can achieve a more even distribution of stresses within the assembly, which increases the durability and structural integrity of the product.

[0019] An embodiment of the invention is also advantageous if the assembly is deformed, particularly in each forming step, into an intermediate shape that differs from the actual shape and / or the target shape. By specifically deforming into the intermediate shape, optimal consideration of the various deformation components of the assembly can be achieved. This results in the assembly assuming the target shape after a final forming step when the effector is disengaged. Additionally, this approach allows for increased flexibility in adapting the deformation processes, which is particularly advantageous for complex shape deviations. For example, the actual shape of assemblies can be brought into conformity with the target shape even if the deviations are not easily corrected, but rather complex or irregular.

[0020] Furthermore, a further development of the invention proves advantageous if the effector is removed from the assembly, particularly after each forming step and / or preferably indirectly following the deformation, for example, into the intermediate mold. The indirect removal of the effector can optimize the dynamic aspects of the deformation by allowing the assembly to be stabilized in the intermediate mold before additional processes are carried out on the assembly. Moreover, the indirect removal of the effector allows the assembly, and in particular its components, to be processed in the intermediate mold using further processes, such as manufacturing processes, and the effector is only subsequently removed from the assembly.

[0021] The invention also proves advantageous when the components are joined together after deformation, e.g., in an intermediate form of the assembly and / or preferably before the assembly and effector are disengaged. In this way, joining, and in particular joining, the components to form the assembly can be combined very advantageously with aligning the actual and target forms of the assembly. Shape correction and joining are thus optimized, leading to more efficient production and lower production costs. It would also be conceivable, in principle, for the joining, i.e., the joining of the components, to be carried out using a separate joining tool that differs from the effector.

[0022] In a preferred embodiment of the invention, it proves advantageous if the components are joined together by means of the effector in a specific configuration of the invention, at least in one forming step, preferably in several forming steps, and particularly preferably in all forming steps. This contributes to further optimizing the shape correction and joining process, since the shape correction and joining are thus not performed using separate tools. The effector can also be adapted for various joining techniques and requirements. This offers flexibility in the processing and joining of different components to form an assembly and enables adaptation to specific production requirements.

[0023] A further development of the invention can also be considered advantageous in which the effector is designed as a joining tool, e.g., a welding tool, in particular a resistance and / or resistance spot welding gun, via which the components are joined, preferably welded, together. Besides resistance and / or resistance spot welding guns, all types of resistance welding tools, for example, those used for roll seam or resistance element welding, i.e., welding rollers or resistance elements or spot welding electrodes, are conceivable as effectors. Furthermore, it is also possible to use clinching or riveting pliers or other joining tools with a mechanical component as effectors. Joining tools, such as...Resistance spot welding guns, due to their geometry, regularly offer the possibility of rotary movement, which, in combination with the deformation of the assembly, especially into the intermediate shape, can advantageously reduce the complexity of the process.

[0024] In an advantageous embodiment of the invention, it is further provided that, particularly in each forming step, the deformation takes into account, for example, a plastic component and an elastic component in the intermediate shape, and / or a component of the assembly's deformation caused by joining the components. This enables an extremely precise alignment of the assembly's actual shape, which may lie outside specified tolerances, with the target shape, since both permanent deformations and reversible elastic deformations, i.e., any return of the assembly to its original shape, are specifically included. Including a deformation component potentially caused by joining helps to better predict and control the assembly's actual shape after the effector is disengaged, i.e., the reduction of the shape deviation, particularly in each forming step.This is particularly useful for complex assemblies where joining the components can cause significant changes in the mechanical properties, such as the stiffness of the assembly.

[0025] An embodiment of the invention is also advantageous if the assembly is deformed so far beyond the desired shape, particularly into an intermediate shape, that the elastic component of the deformation is at least partially compensated after the effector is disengaged, so that the desired shape is at least partially formed and / or the shape deviation is at least minimized. The assembly is thus pressed into an intermediate shape in which at least the superposition of the elastic and plastic components of the deformation is taken into account, with the elastic component causing the assembly to spring back after disengagement. After this springback, depending on the number of forming steps required, the desired shape of the assembly is then at least partially, or even completely, present.When the components are joined to form the assembly after deformation, especially into the intermediate shape, and before the effector is deactivated, the return to its original shape is at least minimized, so that at least part of the elastic deformation contributes to bringing the actual shape into line with the target shape.

[0026] In this context, a design feature of the invention proves particularly advantageous if the elastic deformation resulting from the joining of the components is compensated only partially, i.e., exclusively partially and / or not at all, and persists at least partially, i.e., exclusively partially or completely, as a permanent deformation in the assembly. At least part of the elastic deformation is thus fixed after forming, particularly in the intermediate shape, as a quasi-pseudoplastic deformation. It would therefore also be advantageous for the intermediate shape to already form the desired shape, or at least the desired shape for each forming step.

[0027] The invention allows for numerous embodiments. To further illustrate its basic principle, some of these are shown in the drawing and described below. The drawing shows in Fig. 1a to 1d a first embodiment of the method with a gripper or finger as effector; Fig. 2a to 2e describe a second embodiment of the method with a joining tool as the effector.

[0028] From the Fig. Figures 1a to 1d show a highly simplified representation of a first embodiment of the method for shape correction of assembly 1, here a sheet metal assembly, which is formed from two planar components 2, here formed sheet metal components. The components 2 are each made from a flat semi-finished product and have already been processed by at least one manufacturing process, for example cutting and / or forming. Due to the highly simplified representation of the components 2, this already formed shape is not shown. Fig. However, information from 1a to 1d cannot be obtained.

[0029] When the two components 2 are joined to form assembly 1, manufacturing variations inherent in the manufacturing processes used to process the components 2 result in a discrepancy between the overall actual form 3 of assembly 1 and the overall target form 4 of assembly 1, which is particularly evident in the Fig. 1a are shown, one preferably also of the Fig. 1a Deviation in shape to be taken, which lies outside specified tolerances.

[0030] In order to bring the actual form 3 into conformity with the target form 4 so that it lies within specified tolerances, the effector 5 is generally formed by means of at least one forming step, in this exemplary embodiment in only a single forming step, as described above. Fig. As can be seen from Figure 1b, the effector 5 engages with the assembly 1 at specific points, i.e., in the point-like surface area 9. This point-specific engagement of the effector 5 takes place at the predetermined position 6 on the assembly 1, where position 6 depends on the shape deviation. The effector 5 is also designed as a robot-guided gripper or a finger, e.g., of the gripper.

[0031] Subsequently, assembly group 1, as described in the Fig. 1b and Fig. Figure 1c shows that the effector 5 and the assembly 1 are deformed into an intermediate form 7, which differs from the actual form 3 and the desired form 4, by a relative movement indicated by an arrow. In this embodiment, the relative movement consists of a movement of the effector 5 against the assembly 1, which is held stationary.

[0032] The deformation into intermediate shape 7 takes into account both a plastic and an elastic component, such that the assembly 1 is deformed into intermediate shape 7 far beyond the target shape 4, in such a way that the elastic component of the deformation is compensated and / or balanced after the effector 5 is disengaged. Thus, as in the Fig. As shown in Figure 1d, the target form 4 is fully formed after the effector 5 is disengaged (indicated by an arrow), and the actual form 3 is brought into complete conformity with the target form 4. Thus, the shape deviation of assembly 1 is also completely eliminated and its shape corrected.

[0033] The Fig. Sections 2a to 2e further describe, again in a highly simplified manner, a second embodiment of the method for shape correction of assembly 1. Fig. 2a again shows the overall actual form 3 of assembly 1, which exhibits a form deviation outside specified tolerances from the form also shown in the Fig. 2a shows the overall target form 4.

[0034] Bringing the actual form 3 into conformity with the target form 4, so that it lies within specified tolerances, is again carried out in this exemplary embodiment in just a single forming step, whereby the effector 5, as in the Fig. As can be seen from Figure 2b, the assembly is initially brought into contact with the component 1 at the predetermined position 6, i.e., in the point-like surface areas 9. In contrast to the embodiment of the Fig. In figures 1a to 1d, the effector 5 is configured as the joining tool 8, specifically an electric resistance welding gun. The two electrodes 10 of the joining tool 8 engage the assembly 1 on both sides, as indicated by two arrows.

[0035] Thus, after deformation, components 2 are formed into the intermediate shape 7 of assembly 1, which is in the Fig. 2c, as shown and indicated by two arrows, are connected to each other by means of effector 5. The connection is shown in the Fig. 2d shown, wherein the components 2 are welded together in particular due to the design of the effector 5 as the joining tool 8 designed as a resistance welding pliers.

[0036] The deformation into intermediate shape 7 is again carried out taking into account both a plastic and an elastic component. In this embodiment, the deformation component resulting from joining the components 2 in the assembly 1 is also considered. The assembly 1 is deformed into intermediate shape 7 to such an extent beyond the target shape 4 that the elastic component of the deformation, due to the joining of the components 2 and the associated stiffening of the assembly 1, is partially compensated after the effector 5 is disengaged, and partially persists as a permanent deformation in the assembly 1. Fig. Figure 2e shows the assembly 1 formed from the connected, here welded, components 2 in the actual form 3 corresponding to the target form 4. Reference symbol list 1 assembly 2 components 3 Current state 4 Target form 5 effector 6th position 7 Intermediate Form 8 Joining tool 9 Area 10 electrode QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2011 116 808 A1

[0006] DE 10 2007 002 320 A1

[0007] EP 4 004 978 B1

[0010] EP 1 414 610 B1

[0011] DE 683 411 C

[0012]

Claims

[1] Method for shape correction of an assembly (1), in particular a sheet metal assembly, which is formed and / or is formed from at least two planar components (2), in particular formed sheet metal components, each made from at least one flat semi-finished product, wherein, by means of at least one forming step, an overall actual shape (3) of the assembly (1), which has a shape deviation outside specified tolerances from an overall target shape (4), is brought into conformity with the target shape (4) at least in such a way that the actual shape (3) lies within specified tolerances, characterized by , that the actual shape (3) is brought into conformity with the target shape (4) by bringing an effector (5) into point contact with the assembly (1) in each forming step and deforming the assembly (1) by a relative movement of effector (5) and assembly (1) so that the shape deviation as a result of the respective forming step is at least minimized. [2] Method according to claim 1, characterized by , that the effector (5) is brought into engagement at a predetermined position (6) on the assembly (1), wherein the position (6) depends on the shape deviation. [3] Method according to claim 1 or 2, characterized by , that the assembly (1) is deformed into an intermediate shape (7) that differs from the actual shape (3) and / or the target shape (4). [4] Method according to at least one of the preceding claims, characterized by , that the effector (5) is brought out of engagement with the assembly (1), preferably indirectly by deformation, for example into the intermediate shape (7). [5] Method according to at least one of the preceding claims, characterized by , that the components (2) are joined together after deformation, e.g. in a respective intermediate form (7) of the assembly (1). [6] Method according to at least one of the preceding claims, characterized by , that the components (1) are connected to each other by means of the effector (5). [7] Method according to at least one of the preceding claims, characterized by , that the effector (5) is designed as a joining tool (8) via which the components (2) are joined together. [8] Method according to at least one of the preceding claims, characterized by , that each deformation, for example into the intermediate shape (7), takes into account a plastic component and an elastic component and / or a component of the deformation of the assembly (1) caused by joining the components (2). [9] Method according to at least one of the preceding claims, characterized by, that the assembly (1) is deformed so far beyond the target shape (4), in particular into a respective intermediate shape (7), that the elastic component of the deformation is at least partially compensated after the effector (5) is disengaged, so that the target shape (4) is at least partially formed and / or the shape deviation is at least minimized. [10] Method according to at least one of the preceding claims, characterized by , that the elastic deformation due to the joining of the components (2) is at most partially compensated and persists at least partially as a permanent deformation in the assembly (1).

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