Method for processing metal sheets

Abstract

In various embodiments, a method for processing metal sheets (11) is provided, comprising: determining a quantity and / or a distribution of a substance on a metal sheet (11), wherein the result corresponds to first information; determining a detected roughness of the metal sheet (11), wherein the result corresponds to second information; transmitting (24) the first information and the second information to a forming device (23); calculating an actual roughness of the metal sheet (11) based on the first information and the second information; and forming the metal sheet (11) by means of the forming device (23), wherein the forming is adjusted based on the calculated actual roughness.

Description

[0001] The present invention relates to a method for processing metal sheets, in particular for processing metal sheets in the context of vehicle body production.

[0002] When metal sheets, also called blanks, are processed into body components in the automotive industry, they are processed into body components in press shops using pressing tools in a press line. To facilitate the forming and cutting process of these metal sheets, aluminum sheets are already oiled with a dry lubricant during production in the rolling mill. In the case of steel sheets, conventional lubricants are usually used.

[0003] Fluctuations in the oiling process and the storage of the blanks in the form of a wound coil (roll / spool) lead to the oiling pattern, i.e. the surface distribution of the lubricant, varying from blank to blank. The rolling process in the rolling mill, on the other hand, leads to the surface structure of the sheets being uneven due to manufacturing-related deviations on the rolls. This results in unevenness in the surface height of the blanks, i.e. fluctuating surface roughness. Since the forming and cutting tools in the press line are currently machined to a certain process window, these fluctuations can potentially lead to surface defects, thinning, or even cracks in the finished parts. The resulting rejects and downtimes in the press line have a negative impact on the economic efficiency of the process. Targeted measurement of the lubricant distribution and surface roughness is therefore desirable.

[0004] Currently, in modern press shops that perform both roughness and lubricant measurements, these measurements are only performed at specific points prior to blank cutting. A traversing measuring head moves across the unwound coil perpendicular to the unwinding direction and measures the roughness and lubricant quantity at specific points. The random distribution of the measurement points on the blanks subsequently cut from the coil, as well as their storage after the laser cutting process, which distorts the previously obtained measurement results of the lubricant distribution due to a sometimes considerable storage time, makes individual process control using the recorded measurement data impossible.

[0005] For example, optical measuring devices for detecting the amount of oil applied to a metal surface or the thickness of the lubricating film are known from the documents JP H07-243 970 A and DE 10 2015 007 054 A1.

[0006] Furthermore, a method for detecting the surface of a steel plate is known from JP H11-118 471 A. For this purpose, a preservative oil is applied to the surface of the steel plate, which emits fluorescent light when exposed to light, which is recorded and analyzed by a spectrometer.

[0007] Document DE 10 2006 057 476 A1 discloses a method for analyzing a layer of an auxiliary material on the surface of a forming material, in particular a metal strip, before and / or after a forming process, in particular a rolling process, by means of a spectral analysis.

[0008] Document DE 10 2021 125 661 A1 discloses a method for forming a sheet metal component in a pressing device, comprising the steps of: providing a sheet metal blank as the base material for the sheet metal component; detecting at least one parameter currently characterizing the sheet metal blank by means of a detection device of the pressing device prior to a forming process of the sheet metal component; transmitting the detected characterizing parameter to an electronic computing device of the pressing device; and forming the sheet metal component from the sheet metal blank taking into account the characterizing parameter.

[0009] Document DE 10 2023 116 057 B3 discloses a method for reading a marking and comprises the following steps: A) providing the marking on a substrate, wherein the marking is formed with at least one marking material, B) providing at least one opaque cover layer covering the marking, C) briefly irradiating the at least one cover layer with electromagnetic radiation to which the at least one cover layer is opaque, and D) reading the marking by means of thermal imaging.

[0010] The object of the present invention can therefore be seen in providing a processing method, in particular a forming method for metal sheets, by means of which the reject rate can be reduced.

[0011] This object is achieved by the subject matter of the independent patent claim. Further preferred embodiments can be found in the dependent patent claims.

[0012] The invention provides a method for processing metal sheets (blanks). The metal sheets can, for example, be metal sheets that are processed in a press line to form suitable body parts.

[0013] The method according to the invention comprises determining or detecting a quantity and / or distribution of a substance on a metal sheet, wherein the result corresponds to a first piece of information or is stored as such for further processing. The substance can be a lubricant, for example, a lubricating oil with which the corresponding metal strip was coated during winding in the rolling mill.

[0014] Determining the quantity and / or distribution of a substance on the metal sheet can mean, in particular, detecting inhomogeneities in the distribution of the substance, i.e., whether the distribution is considered to be uniformly coated with the substance within a certain tolerance. This can be done, for example, based on a thermal image, in which it can be deduced from detected inhomogeneities whether these are caused by an excess or insufficient amount of the applied substance.

[0015] The method according to the invention further comprises determining or detecting a detected roughness of the metal sheet, wherein the result corresponds to a second piece of information or is recorded as such for further processing. The roughness of the blank can be determined, for example, using a light-section method or a laser speckle photometry method.

[0016] The method according to the invention comprises, in a further step, transmitting the first information and the second information to a forming device. The forming device can, in particular, be a press that is part of a press line. The transmission of the first and second information to the forming device can take place directly or via a central control device.

[0017] The method according to the invention comprises, in a further step, calculating an actual roughness of the metal sheet based on the first information and the second information. The combination of the two measuring methods, i.e. the determination of the quantity and / or distribution of the substance on the metal sheet and its detected roughness, has the advantage that the superposition of the two measured variables can be taken into account. This is a frequently occurring problem because the substance or lubricant accumulates in areas of high roughness, also known as pockets. Due to the viscous properties of the substance, a rather smooth surface results for the optical detector. It is therefore advantageous if both determination methods are considered together. By evaluating the detected roughness and the substance quantity or substance distribution, the actual roughness of the metal sheet can be calculated using a calculation method.

[0018] In a further step, the method according to the invention comprises forming the metal sheet by means of the forming device, wherein the forming is adjusted on the basis of the calculated actual roughness.

[0019] The present method is based on the fundamental idea of obtaining two pieces of information via two information channels prior to the forming process of the metal sheet: first, information about the distribution and / or quantity of the substance, and second, information about the roughness distribution. Both pieces of information are used to adjust control parameters of the forming process on the forming device, such as a press, such as the press force. By adjusting the control parameters during further processing of the metal sheet, potential scrap can be prevented before it becomes actual scrap.

[0020] The quotient of lubricating oil layer thickness and roughness defines a forming parameter that influences the production result. By adjusting the forming parameters on the forming device while taking the forming parameter into account, potential scrap can be prevented or at least minimized. By recording the first and second pieces of information for the metal sheet being processed immediately before the forming process, the process can be adapted (to a certain extent) to the specific properties of the metal sheet. In particular, this can prevent a metal sheet characterized by measured values recorded before storage from being processed suboptimally and thus leaving the forming process as scrap.

[0021] The method according to the invention can be integrated as an inline measurement, i.e. as an automated measurement directly into the production process line and carried out at an appropriately configured measuring station.

[0022] According to further embodiments of the method according to the invention, the determination of the quantity and / or distribution of the substance on the metal sheet and / or the determination of the roughness of the metal sheet can be carried out essentially over the entire surface. It can be taken into account that the roughness usually does not vary as much as the quantity and distribution of the substance on the metal sheet, since the manufacturing process in the rolling mill is generally constant. Fundamentally, however, roughness and the quantity of substance and their distribution are interdependent. For example, it has been experimentally observed that lubricant accumulates to a greater extent within waves / valleys of a rough surface. Therefore, a detected roughness of the surface due to the applied lubricant may not correspond to the actual roughness. By knowing the substance distribution and / or quantity, the actual roughness can be determined from the detected roughness.

[0023] According to further embodiments of the method, the specific heat capacity of the substance may differ from the specific heat capacity of the material of the metal sheet. Determining the quantity and / or distribution of the substance on the metal sheet may then comprise the following steps: heating the metal sheet, detecting the heated metal sheet using a thermal imaging sensor, and determining the quantity and / or distribution of the substance on the metal sheet based on a thermal image of the metal sheet. For this purpose, the metal sheet may be heated uniformly over its entire surface to be measured. The surface to be measured may comprise a partial surface or the entire surface of the metal sheet. The surface may be heated uniformly by exposing it to an environment with a predetermined temperature. For this purpose, the metal sheet may be placed in a heating chamber.An infrared radiation source can be used for heating, for example in the form of a targeted distribution of infrared radiators and / or an infrared heater. The metal sheet can be heated only to the extent that the material properties of the sheet do not change permanently, yet a temperature change is detectable. Heating the metal sheet also heats the substance arranged on top. Since the specific heat capacity of the two materials (substance and metal sheet) differs, a temperature gradient can be measured during heating depending on the substance distribution. A higher concentration of the substance (≈greater substance thickness) results in a more pronounced temperature gradient.The determination of the quantity and / or distribution of the substance based on the thermal image can be carried out at a correspondingly configured measuring station, which can have a heating chamber for heating the metal sheet, at least one thermal image sensor, preferably two thermal image sensors, a data evaluation unit for evaluating the thermal images captured by the thermal image sensors, and a control unit configured to control the measuring station.

[0024] However, by calibrating the detection method in advance, absolute measurement values can also be determined, particularly the thickness of the applied substance. For this purpose, tests can be conducted in advance using comparative measurement methods to empirically determine which temperature gradient corresponds to a corresponding amount of lubricant.

[0025] According to further embodiments of the method, the amount and / or distribution of the substance on the metal sheet can be determined based on temperature gradients in the thermal image.

[0026] It should be noted that the thermographic method can be an exemplary method that can be used within the scope of the present invention. Instead, a fluorescence scanner, for example, can be used. This sensor utilizes the fluorescent behavior of most mineral oils. Upon irradiation with UV light, these emit fluorescent radiation, which can be captured by a suitable measuring device. This method is capable of performing the required measurement both over a large area and within the required cycle time. Furthermore, IR spectroscopy can be used.

[0027] According to further embodiments of the method, the method can be performed with respect to both surfaces of the metal sheet. In other words, both the top and bottom sides of the metal sheet can be examined for the oiling pattern.

[0028] According to further embodiments of the method, this may further comprise separating the metal sheet from a stack of multiple metal sheets. The separation of the metal sheet to be processed may occur immediately at the beginning of its processing in a press line, i.e., in particular, before the first and second pieces of information are determined. Thus, the first and second pieces of information reflect the actual or true condition of the metal sheet after its storage and immediately before its processing.

[0029] According to further embodiments of the method, the separated metal sheet can be fed to a measuring station which is located upstream of the forming device in terms of process technology, i.e. with regard to the sequence of processing steps in the entire processing process of the metal sheet, and at which the first and second information are determined.

[0030] According to further embodiments of the method, this may further comprise applying the substance to at least one region of the metal sheet at least based on the first information. This step involves a compensatory application of the substance or a repeated application of the substance in regions of the metal sheet which have an insufficient amount of the substance. In particular, the step may be a re-oiling step in order to return the forming parameters of a metal sheet to the target range. In other words, the substance may be applied to at least one region of the metal sheet for which the determination has shown that the amount of substance is below a target value. In the industrial processing of metal sheets in a press line, this step may be carried out in a re-oiling station.

[0031] According to further embodiments of the method, the substance can be applied before the metal sheet is formed. In other words, after the substance application step, the metal sheet can be fed to the forming device without intermediate storage. For the application of the substance, the metal sheet in question can be fed to a system equipped for this purpose and then first undergo the measurement process of the quantity and / or distribution of the substance again to verify the success of the post-treatment with the substance.

[0032] The method according to the invention described here can be implemented at the beginning of an industrial press line and upstream of a re-oiling system. The corresponding measuring station can be positioned immediately after the blank separation and thus correspond to a SOL (start-of-line) measuring station. After any re-oiling of a blank detected as deficient in oil, it can be processed in the press line, essentially including deep drawing, re-forming, trimming / punching.

[0033] On the one hand, this allows the obtained measurement result of the lubricant distribution to be subsequently influenced by the relubricator. By positioning the measuring stand after the blanks have been separated from their stacked storage arrangement, the factors influencing the lubricant distribution can be taken into account. Furthermore, it is also possible to measure blanks that were not cut in the press shop but were purchased pre-cut.

[0034] Using the method according to the invention, which can be carried out on an appropriately configured inline measuring station, the lubricant quantity and / or its distribution on the blank, as well as its roughness, can be detected. The detection method or the appropriately configured measuring station is capable of maintaining the cycle time of the press line. Another advantage is that material parameters and properties of the blank are not impaired by the method according to the invention, as it is a non-destructive testing method. By using, for example, a high-resolution thermal imaging sensor, the measurement resolution can be selected such that detailed re-oiling of the blank can be carried out using the grid of a spray lubrication system.

[0035] The measuring station set up and operating according to the method according to the invention can preferably not sort the blanks into good parts and rejects / rework based on the measured material parameters, but rather transmit the recorded data "just-in-time" to a control unit of the press line. This allows every blank to be utilized, since the subsequent manufacturing process, i.e., the one following the re-oiling system, can be individually adapted to each blank. This allows a significant increase in process stability.

[0036] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0037] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings. Fig. Figure 1 illustrates a conventional method for measuring the distribution of a substance on a roll of material and its roughness. Fig. 2 illustrates an embodiment of the method according to the invention for processing metal sheets.

[0038] In Fig. Figure 1 illustrates a conventional method for measuring the distribution of a substance on a material roll and its roughness. The conventional approach is that the measurement is performed before the blank is cut. For this purpose, a sheet metal strip 10 wound into a coil and comprising the blanks 11 is first unwound, which is indicated by an arrow 15. The unwound sheet metal strip 10 is measured using a measuring head. Since the measuring method only has a small measuring range, the measuring head must be mounted on a cyclically moving traverse in order to be able to cover the full width of the sheet metal strip 10. This traversing of the measuring head over the sheet metal strip 10 is indicated by an arrow 14, from which the Fig. The trajectory 12 of the measuring head shown in Figure 1 results. Since the cycle time in modern press shops is significantly higher than the required measuring time of such systems, only point measurements 13 can be recorded along the unwound sheet metal strip 10. After the point measurements of the unwound sheet metal strip 10 have been completed, it is trimmed, which is indicated by arrow 16. The cut blanks 11 are then stacked together in stacks 17 and stored.

[0039] The Fig. The measurement outlined in Figure 1 reflects both the determination of a quantity and / or distribution of the substance on the sheet metal strip 10, as well as a determination of the roughness of the sheet metal strip 10. For this purpose, the corresponding measuring heads can be mounted on the same traverse and carried out simultaneously, or mounted on different traverses and carried out sequentially.

[0040] In the Fig. From the process outlined in Figure 1, it can be seen that the measuring points 13 arranged on the sheet metal strip 10 allow, on the one hand, a relatively rudimentary recording of the data relating to the blanks 11, since only a few measuring points 13 are generated per blank 11. On the other hand, the measuring points 13 are each located at different locations on the sheet metal strip 10, since the measurement is carried out before the blanks 11 are cut from the sheet metal strip 10. As a result, the measuring points 13 per blank 11 are unevenly distributed.

[0041] Fig. Figure 2 illustrates an embodiment of the method according to the invention for processing metal sheets 11 in the context of processing metal sheets 11 in a press line. In contrast to the conventional approach, the method according to the invention is carried out after the storage of the already cut metal sheets 11, preferably immediately at the beginning of the processing of the metal sheets 11 in a press line. For this purpose, the stack of metal sheets 17 is first separated, which is indicated by an arrow 20. The metal sheets 11 are then measured according to the method according to the invention on a suitably equipped measuring or test stand 22, both with regard to the distribution and / or quantity of the substance distributed on their surface and also with regard to the roughness of the surface. After the measurement has been carried out, the metal sheets 11 can be re-oiled if necessary (the corresponding station is shown in Fig.2 not explicitly shown) before the metal sheets 11 are fed to a press 23 for deep drawing.

[0042] The measurements carried out at the measuring stand 22 can be carried out over the entire surface or at least in a network-like manner with a significantly higher density and in particular with a uniform, comparable distribution of the measuring points 13 per metal sheet 11. In addition, the measurement is carried out before the metal sheets 11 are formed and in particular after they have been stored in the stack 17, whereby the influence of storage can be taken into account during processing.

[0043] For each metal sheet 11, a data set comprising the first information and the second information can be recorded at the measuring station 22 and transmitted "just-in-time" to a central control system of the press line, which can be used to control the press 23. The transmission of the recorded data and its use in setting the working parameters of the press 23 is indicated by an arrow 24. The control unit (not explicitly shown) can, in particular, be configured to directly adapt the control parameters within the press line to the metal sheet 11 currently being processed. Automated adjustment of the actuators within the presses and, if necessary, area-specific relubrication by the spray lubrication system are possible in order to influence any deviation of the lubricant distribution from the target process window. The control unit can be trained on the basis of neural networks or machine learning algorithms.In general, this can lead to a reduction in rejects, reworked parts and downtimes of the press line.

Claims

[1] Method for processing metal sheets (11), comprising: Determining a quantity and / or a distribution of a substance on a metal sheet (11), the result corresponding to a first piece of information; Determining a detected roughness of the metal sheet (11), the result corresponding to a second piece of information; Transmitting (24) the first information and the second information to a forming device (23); Calculating an actual roughness of the metal sheet (11) based on the first information and the second information; and Forming the metal sheet (11) by means of the forming device (23), wherein the forming is adjusted on the basis of the calculated actual roughness. [2] Method according to claim 1, wherein the determination of the amount and / or the distribution of the substance on the metal sheet (11) and / or the determination of the detected roughness of the metal sheet are carried out substantially over the entire surface. [3] Method according to claim 1 or 2, wherein the specific heat capacity of the substance differs from the specific heat capacity of the material of the metal sheet (11); and wherein determining the amount and / or distribution of the substance on the metal sheet (11) comprises: Heating the metal sheet (11); Detecting the heated metal sheet (11) by means of a thermal imaging sensor; Determining the quantity and / or distribution of the substance on the metal sheet (11) based on a thermal image of the metal sheet (11). [4] Method according to claim 3, wherein the amount and / or distribution of the substance on the metal sheet (1) is determined on the basis of temperature gradients in the thermal image. [5] Method according to one of claims 1 to 4, further comprising: Separating (20) the metal sheet (11) from a stack (17) of several metal sheets (11). [6] Method according to claim 5, wherein the singulation (20) of the metal sheet (11) takes place from the point of view of the processing of the metal sheets (11) before determining the first and second information. [7] Method according to claim 5 or 6, wherein the separated metal sheet (11) is fed to a measuring station (22) which is located upstream of the forming device (23) in terms of process technology and at which the first and second information are determined. [8] Method according to one of claims 1 to 7, further comprising: Applying the substance to at least one area of the metal sheet (11) at least on the basis of the first information. [9] Method according to claim 8, wherein the application of the substance takes place before the forming of the metal sheet (11).

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