Method and analysis system for locating a weld spatter on a workpiece

Abstract

Method for locating a weld spatter on a workpiece (14), comprising the steps - Welding (S10) of the workpiece (14) by means of a welding device (12) which automatically controls processing positions on the workpiece (14) and which performs a welding process at the respective processing positions according to specified electrical welding parameters; - Determine (S12) by means of a calculating device (16) whether a deviation from the specified electrical welding parameter is detected during the welding process; - if a deviation is detected, determine (S12) the processing position by the calculating device (16) at which the deviation of the specified electrical welding parameter is determined; - Defining (S14) a region (20) around the determined machining position on the workpiece (14) by the calculating device (16) for localizing the weld spatter; where the weld spatter is classified according to the determined deviation, and wherein a dimension of the area (20) around the determined processing position is adjusted depending on the classification of the weld spatter.

Description

[0001] The invention relates to a method for locating a weld spatter on a workpiece and an analysis system for locating a weld spatter on a workpiece and / or for reworking a workpiece.

[0002] When welding workpieces, especially in car body construction, steel is primarily used alongside aluminum. Reasons for this include its higher resistance, higher load-bearing capacity, and lower cost. During welding, particularly resistance spot welding, weld spatter can occur depending on the welding parameters chosen. Despite continuous monitoring and optimization of welding parameters, occasional weld spatter can still occur. To prevent corrosion caused by protruding weld spatter, to avoid cutting cables, and to prevent employee injuries from the spatter's protruding tips, weld spatter is reworked, primarily by grinding it down. Often, the weld spatter is identified and removed manually.A disadvantage of this method is that the resulting grinding dust and the need for rework place high demands on occupational safety and ergonomics. Furthermore, the processing results are not reproducible without variations due to the subjective influence of the employee.

[0003] From DE 10 2015 119 240 B3, a method for the automated detection of defects in a workpiece surface and the generation of a robot program for machining the workpiece is known. The method comprises locating defects in a workpiece surface, determining a three-dimensional topography of the localized defects, and categorizing at least one localized defect based on its topography. Depending on the defect category, a machining process is selected, and a robot program for robot-assisted machining of the defect is generated by computer according to the selected machining process.

[0004] From DE 10 2017 208 102 A1 a method for the fully automated correction of coating defects of a hardened coating of a substrate is known.

[0005] From CN 112 692 418 A, a quality control device and a machine vision-based method for spot welding are known. The method comprises the following steps: recording data associated with the resistance spot welding process, detecting parameters from the recorded data associated with spatter, analyzing the detected parameters, recording the spatter conditions during spot welding using an industrial high-speed camera, determining the number of spatters produced, the spatter morphology, and the spatter direction by image processing, and creating a database for monitoring spatter generation events in resistance spot welding.

[0006] From US patent 3,591,764, a method and device for detecting metal ejection during resistance welding are known, wherein a mechanical or electrical change occurring in the welding zone is used to estimate time and quantity parameters of the metal ejection.

[0007] AT 508 696 A1 specifies a monitoring module for monitoring an arc welding process, comprising a camera, a flash lamp, and a control unit that operates the flash lamp so that it illuminates at the time the camera captures the image. The aforementioned components are arranged in a common housing.

[0008] The object of the invention is to provide an improved defect localization and / or classification process and thus improved automation.

[0009] This problem is solved by the independent patent claims. Advantageous embodiments of the invention are disclosed in the dependent patent claims, in the following description, and in the figures.

[0010] The invention is based on the idea that during welding processes, such as spot welding, data from the welding process, such as current and / or voltage, can be recorded. This data can be stored with correlation to a specific component or workpiece and its corresponding coordinates. By analyzing the recorded data, deviations, such as the formation of weld spatter, and thus the need for rework can be determined. This eliminates the need for subsequent visual inspection, particularly by personnel.

[0011] The invention provides a method for locating weld spatter on a workpiece. The method can be carried out, for example, by an analysis system or welding system with a welding device and comprises the following steps: welding the workpiece using a welding device that automatically controls processing positions on the workpiece and performs a welding process at each processing position according to predetermined electrical welding parameters; determining whether a deviation from the predetermined electrical welding parameters is detected during the welding process; and, if a deviation is detected, determining the processing position at which the deviation of the predetermined electrical welding parameter is detected.Subsequently, an area around the determined machining position on the workpiece can be defined to locate the weld spatter.

[0012] In other words, a welding device can weld at least one workpiece by automatically moving the device to the processing position and performing the welding process there. This welding process can be carried out using predefined electrical welding parameters. These parameters can refer to a voltage and / or current used to operate an electrode of the welding device during the welding process.

[0013] During the welding process, it can be checked whether a deviation from the specified electrical welding parameter is detected at the respective processing position. In particular, the formation of weld spatter can cause a drop in resistance, which can be identified as a deviation. If this deviation is detected, the processing position at which this deviation from the specified electrical welding parameter occurred can be saved. A zone can then be defined around this processing position to help locate the weld spatter. For example, experience may show that when weld spatter forms, a zone with a radius of, say, 10 cm around the processing position is affected. The origin of the weld spatter is known because the coordinates of the welding point are available.

[0014] The welding device preferably includes a robot that performs the welding process and controls the machining positions on the workpiece. Preferably, a specific electrical welding parameter can be predefined for each machining position on each workpiece. The electrical welding parameter can, for example, be predetermined from previous measurements with similar workpieces, and the deviation can be a difference from the welding parameters of the previous measurements. That is, a target value, predetermined from several measurements of previous welding processes for the component as a normal state without weld spatter, can be compared with an actual value of the current welding process to determine the deviation. Welding parameters can include one or more explicit values ​​or a curve over time.

[0015] Furthermore, the weld spatter is classified based on the determined deviation. In other words, the magnitude and / or duration of the deviation from the specified electrical welding parameter can be determined, allowing the weld spatter to be classified. A waveform of the current and / or voltage signal can also provide information about the type of weld spatter. For example, the size of the weld spatter and / or its expected distance from the welding position can be estimated or classified based on the determined deviation. This offers the advantage of improved localization and / or the degree of post-processing.

[0016] Furthermore, the system is designed to define the dimensions of the area around the identified machining position based on the classification of the weld spatter. This means, for example, that the classification might indicate that the weld spatter could have originated in a large area around the machining position. Based on this classification, the dimensions of the area around the identified machining position can then be adjusted. For instance, the dimensions can be increased. This has the advantage of reducing the number of weld spatters that are overlooked, as a larger area can be inspected for rework.

[0017] The invention offers the advantage that subsequent optical inspection can be eliminated, thereby optimizing cycle times during rework, such as grinding. Furthermore, automating previously manual and / or optical inspection and rework reduces the workload for production personnel. In addition, objective detection and rework of deviations leads to increased reproducibility. Overall, this improves the rework process.

[0018] The invention also includes embodiments that offer additional advantages.

[0019] One embodiment provides that, to determine whether a deviation is detected, a current signal and / or a voltage signal from the welding device is monitored as an electrical welding parameter. The deviation is detected if the current signal and / or voltage signal changes by a predetermined value. This means that a current signal and / or a voltage signal can be monitored, which the welding device uses to perform the welding process. If the current signal and / or voltage signal changes by a predetermined value, which could be specified, for example, for the machining position and the workpiece, this can be detected as a deviation, with the formation of weld spatter being indicated by the deviation. In particular, the formation of weld spatter can be accompanied by a drop in the resistance of the electrical welding parameters, which can be measured in this way.This design offers the advantage that no additional optical inspection of the component is necessary, thus saving costs.

[0020] Another embodiment provides that the electrical welding parameter is predefined depending on the workpiece and / or the respective machining position on the workpiece. For example, a predefined electrical welding parameter, such as a current and / or a voltage, can be specified for each workpiece and / or each machining position on the respective workpiece, with which the welding process is to be carried out. This embodiment offers the advantage of improved differentiation between weld spatter and spatter formation.

[0021] Another embodiment involves inspecting the defined area using an optical sensor device. This optical inspection improves the localization of the weld spatter and / or allows for optical classification of the weld spatter. In other words, an optical sensor device can be provided to inspect the previously defined area. This optical sensor device could be, for example, a camera and / or a laser, particularly a lidar, which captures the surface of the workpiece in the identified area. This allows the precise position of the weld spatter to be determined and / or the weld spatter to be optically classified. Through optical classification, such as the size of the weld spatter, a post-processing strategy can be individually adapted to the severity of the spatter.

[0022] In a further embodiment, it is particularly preferred that the workpiece with the at least one weld spatter undergoes automatic rework in the defined area. For example, workpieces or components on which a weld spatter has been detected can be removed and transported to a rework station, such as an autonomous grinding station. At the autonomous grinding station, a processing strategy to compensate for the defect can be developed, for example, using a robot. In particular, the previously identified area with the weld spatter can be ground down. This embodiment offers the advantage of eliminating manual rework and achieving improved process automation.

[0023] Preferably, post-processing parameters can be set depending on the defined area on the workpiece. These parameters can include, for example, path and process parameters, in particular a path, contact pressure, feed rate, angle of attack, and / or rotational speed. Preferably, a reachability can be calculated based on the defined area, which can then be used to control a robot for the post-processing.

[0024] It is particularly preferred that post-processing parameters are set depending on the classification of the weld spatter and / or the optical classification of the weld spatter. For example, the aforementioned post-processing parameters can be adjusted based on the classification of the weld spatter, which is determined by the optical sensor device based on the deviation from the electrical welding parameter and / or the optical classification. This offers the advantage of improved weld spatter removal.

[0025] A further aspect of the invention relates to an analysis system or welding system for locating and / or reworking weld spatter on a workpiece, particularly in vehicle body construction, wherein the analysis system is configured to perform a method according to one of the preceding embodiments. The analysis system can, in particular, include a welding device and / or an autonomous grinding station for reworking. Preferably, the analysis system can include a computing device that controls the process steps for carrying out the method. This offers the same advantages and possibilities for variation as the method itself.

[0026] The invention also includes the computing device for the analysis system. The computing device can comprise a data processing device or a processor unit configured to perform an embodiment of the method according to the invention. For this purpose, the processor unit can comprise at least one microprocessor and / or at least one microcontroller and / or at least one FPGA (Field Programmable Gate Array) and / or at least one DSP (Digital Signal Processor). Furthermore, the processor unit can comprise program code configured to perform the embodiment of the method according to the invention when executed by the processor unit. The program code can be stored in a data memory of the processor unit.

[0027] The invention also includes further developments of the analysis system according to the invention, which have features already described in connection with the further developments of the method according to the invention. For this reason, the corresponding further developments of the analysis system according to the invention are not described again here.

[0028] The invention also includes combinations of the features of the described embodiments. The invention therefore also includes realizations that each exhibit a combination of the features of several of the described embodiments, provided that the embodiments have not been described as mutually exclusive.

[0029] The following are exemplary embodiments of the invention described. This is illustrated by: Fig. 1. A schematic representation of an analysis system according to an exemplary embodiment; and Fig. 2 a schematic process diagram according to an exemplary embodiment.

[0030] The exemplary embodiments described below are preferred embodiments of the invention. In these exemplary embodiments, the described components each represent individual features of the invention, which can be considered independently of one another and each further develops the invention independently. Therefore, the disclosure is intended to include combinations of features of the embodiments other than those shown. Furthermore, the described embodiments can also be supplemented by further features of the invention already described.

[0031] In the figures, identical reference symbols denote functionally equivalent elements.

[0032] In Fig. Figure 1 is a schematic representation of an analysis system 10 according to an exemplary embodiment. The analysis system 10 can have at least one welding device 12, wherein the welding device 12 in this example can be configured as a welding robot 12. The welding robot 12 can be configured to perform a welding process on a workpiece 14, wherein in this example the workpiece 14 can be a vehicle body 14 during a motor vehicle manufacturing process. To control the welding device 12, a control program can be executed in a computing device 16 of the analysis system 10, wherein the computing device 16 can, for example, comprise a computer configured to control at least the welding robot 12. Here, respective processing positions for the workpiece 14 can be specified, which are to be welded according to specified electrical welding parameters.For example, specific currents and voltages can be stored as electrical welding parameters for spot welding, which are to be used for the respective processing position.

[0033] In addition, the analysis system 10 for post-processing the vehicle body 14 can include a post-processing device 18, which in this example can be a grinding robot 18. Preferably, the grinding robot 18 can also be configured by the computing device 16 to repair welding defects, in particular weld spatter.

[0034] The following describes a method for locating and / or repairing weld spatter from analysis system 10 based on the information provided in Fig. The two process steps shown are described, whereby the process steps can be controlled, for example, by the computing device 16.

[0035] In step S10, the welding device 12 can perform a welding process at a processing position on the vehicle body 14 according to predefined electrical welding parameters. For example, current and / or voltage can be specified, by means of which the welding device 12 creates a weld spot.

[0036] During the welding process, step S12 can determine whether a deviation from the specified electrical welding parameter is detected. At least one current and / or voltage signal from the welding device 12 can be monitored to check whether the current and / or voltage signal changes by a predetermined value during the welding process. In particular, a resistance dip can occur when weld spatter forms, which can be detected in the respective signal. If this change exceeds a threshold, weld spatter can be indicated. The deviation can depend on the specific machining position on the vehicle body 14. This means that the value indicating the deviation of the current and / or voltage signal for weld spatter detection can vary depending on the machining position.If such a deviation is detected, the processing position at which this deviation, and thus the weld spatter, occurred can also be saved in this step.

[0037] In step S14, a region 20 can then be defined around the determined machining position on the vehicle body 14 to locate the weld spatter. This region 20 can represent an area around the machining position where the weld spatter was detected. Preferably, the weld spatter can also be classified based on the previously determined deviation, and the region 20 can be adjusted according to this classification. That is, the size of the region 20 can be defined based on the classification. This has the advantage that the position of the weld spatter can be restricted to this region 20. The position of the weld spot, and thus the origin of the weld spatter, is known.

[0038] Optionally, in a further step S16, the area 20 can be recorded by an optical sensor device 22, whereby a further improvement in the localization of the weld spatter and / or an optical classification, for example a size and extent of the weld spatter, can be carried out.

[0039] Finally, in step S18, automatic post-processing can be carried out by the post-processing device 18, i.e., the grinding robot 18, within the defined area 20. Here, depending on the defined area 20 and, alternatively or additionally, depending on the previously performed classification of the weld spatter, one or more post-processing parameters of the grinding robot 18 can be set. Specifically, the path, contact pressure, feed rate, rotational speed, and angle of attack can be changed. For this purpose, the computing device 16 can, for example, generate a robot program that can be composed of linked, statically programmed robot programs. Thus, any weld spatter that may occur can then be removed by the grinding robot 18.

[0040] Overall, the examples show how the invention can provide a method for autonomous actuator coupling through automated detection of deviations by recording and analyzing data from value-adding processes during value creation and needs-based autonomous processing.

Claims

[1] Method for locating a weld spatter on a workpiece (14), comprising the steps - Welding (S10) of the workpiece (14) by means of a welding device (12) which automatically controls processing positions on the workpiece (14) and which performs a welding process at the respective processing positions according to specified electrical welding parameters; - Determine (S12) by means of a calculating device (16) whether a deviation from the specified electrical welding parameter is detected during the welding process; - if a deviation is detected, determine (S12) the processing position by the calculating device (16) at which the deviation of the specified electrical welding parameter is determined; - Defining (S14) a region (20) around the determined machining position on the workpiece (14) by the calculating device (16) for localizing the weld spatter; where the weld spatter is classified according to the determined deviation, and wherein a dimension of the area (20) around the determined processing position is adjusted depending on the classification of the weld spatter. [2] Method according to claim 1, wherein, to determine whether a deviation is detected, a current signal and / or a voltage signal of the welding device is monitored as an electrical welding parameter, wherein the deviation is detected if the current signal and / or the voltage signal changes by a predetermined value. [3] Method according to one of the preceding claims, wherein the electrical welding parameter is specified depending on the workpiece (14) and / or the respective machining position on the workpiece (14). [4] Method according to one of the preceding claims, wherein the defined area (20) is checked by means of an optical sensor device (22) (S16) and the localization of the weld spatter is improved and / or an optical classification of the weld spatter is carried out on the basis of the optical check. [5] Method according to one of the preceding claims, wherein the workpiece (14) with the at least one weld spatter undergoes automatic post-processing at the defined area (20) (S18). [6] Method according to claim 5, wherein post-processing parameters of the post-processing are set depending on the defined area (20) on the workpiece. [7] Method according to one of claims 5 or 6 with reference to claim 1 and / or 4, wherein post-processing parameters are set depending on the classification of the weld spatter and / or the optical classification of the weld spatter.[8] Analysis system (10) for locating a weld spatter on a workpiece (14), particularly in car body construction, wherein the analysis system (10) comprises a welding device (12) which is configured to weld the workpiece (14) by automated control of processing positions on the workpiece (14) and by a welding process according to predetermined electrical welding parameters at respective processing positions, wherein a computing device (16) of the analysis system (10) comprises a processor unit with program code and is configured to determine whether a deviation from the predetermined welding parameter occurs during the welding process, and if the deviation occurs, to determine the processing position at which the deviation of the predetermined electrical welding parameter occurred and to define an area around the determined processing position on the workpiece for locating the weld spatter,wherein the calculating device (16) is further configured to classify the weld spatter depending on the determined deviation, and to adjust a dimension of the area around the determined machining position depending on the classification of the weld spatter.

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