STRETCHING-BENDING-STRAIGHTENING SYSTEM AND METHOD OF THE ACTUATION THEREOF

Abstract

In a stretching-bending-straightening system and a method for the actuation thereof, material in strip form is fed to a high-tension region (50) and a low-tension region (52), wherein the low-tension region (52) is arranged downstream of the high-tension region (50). A bending-straightening unit is arranged in the high-tension region (50). A measuring system determines first measured values in the high-tension region (50). A controller (C) is intended and suitable for determining a deviation of the first measured values from a setpoint value of the bending-straightening result and for determining at least one manipulated variable for the bending-straightening unit in dependence on the determined deviation within a first closed control loop. By additionally providing at least one measuring system for determining second measured values in the low-tension region, by having a controller (C) intended and suitable for determining a deviation of the second measured values from the setpoint value of the bending-straightening result and for determining the at least one manipulated variable in dependence on the determined deviation within a second closed control loop, and by providing selecting means that are intended and suitable for selecting the first or second closed control loop for reducing the deviation of the first and/or second measured values from the predetermined or predeterminable setpoint value, a stretching-bending-straightening system and a method for the actuation thereof are designed in such a way that the quality of the strips processed thereby is increased.

Description

REFERENCE TO RELATED APPLICATIONS

The present application relates to, and claims the priority of, the German patent application 10 2018 101 501.1, filed on Jan. 23, 2018, and of the German patent application 10 2018 111 627.6, filed on 15 May 2018, the disclosure of which is hereby expressly incorporated by reference into the subject matter of the present application.

FIELD OF THE INVENTION

The invention relates to a stretching-bending-straightening system according to the preamble of claim 1 and to a method for the actuation thereof according to the preamble of claim 10.

PRIOR ART

Stretching-bending-straightening systems as illustrated schematically in FIG. 3 are systems that are used to minimize internal stresses in ferrous and non-ferrous metallic strips and thus to attain an improved flatness. The term “metallic strips” is understood to mean any materials in strip form. The term “metallic” includes metals per se, and also their alloys. The straightening process is performed since the strips have areas of unflatness after the preceding rolling process. These areas of unflatness are created by fibers of differing length in the material and are manifested by undulations in the strip. This is shown by way of explanation in FIGS. 4a, 4b and 5a to 5d. If the material 10 in strip form has undulations 12 according to FIG. 4a, this is caused by different fiber lengths according to FIG. 4b. In relation to the reference fiber length Lref, the adjacent fibers have a different length difference ΔL. These undulations may be formed in the material 10 in strip form as middle undulations 13 according to FIG. 5a, as edge undulations 14 according to FIG. 5b, as edge undulations on one side according to FIG. 5c, or as a combination of edge undulations 14 and middle undulations 13.

For the finishing process, a brake S-block 16 and a tension S-block 18 are used to produce a high-tension region in the stretching-bending-straightening system shown in FIG. 3 for the material 10 in strip form fed in the movement direction 24 from a coil arranged on a decoiler, and the material 10 in strip form is stretched in the high-tension region. (The letter “S” is used to indicate that the strip in these regions is guided around rollers in an S shape.) The tension that occurs is measured using a measuring device 22. In addition, the strip is subjected in the bending-straightening apparatus 26 to alternating bending. As a result of these two measures, the shorter fibers are adapted to the longer fibers, and internal stresses are eradicated. The material in strip form straightened in this way is then rolled up again on a recoiler 28.

In order to produce alternating bending in the bending-straightening apparatus 26, according to FIG. 6, 7a, 7b precise straightening rollers are used from above and below over the entire strip width. These straightening rollers 30 are supported by shorter support rollers 32 in order to avoid sagging. Since areas of unflatness in the material 10 in strip form only occur in part, for example in the edge region, the supports of the lower straightening rollers 30 are adjustable. It is thus possible to adjust the straightening rollers 30 to a bending contour so as to produce a targeted stretching of the shorter fibers. In the case of edge undulations 14 on both sides, the inner supports for example are raised, so as to stretch the shorter fibers situated in the middle of the strip.

In addition, according to the prior art, an unflatness measuring system (UMS) according to FIG. 8, which can be procured from Ungerer Technology GmbH, may be used for the straightening process. This unflatness measuring system was designed especially for measuring the unflatness of strips with relatively low specific strip tensions. It determines the areas of unflatness over the entire strip width of the product after the tension S-block 18 and is able to adjust the individual supports of the bending-straightening apparatus 26 such that an optimal straightening result is attained. In order to identify the areas of unflatness, sensitive force sensors are used for the UMS and are mounted on a stationary axis. A measuring roller 36 is preferably used for this purpose. Over adjacently arranged segments, different forces from the strip or material 10 in strip form which are caused by the areas of unflatness are directly transferred to the sensors. Two force sensors are preferably used for each segment. These measured values are processed by an analysis unit 34 and are forwarded to the controller C. The controller C calculates the optimal parameters for the straightening process and thus controls the adjustment of the supports, that is to say the support rollers 32, by way of a memory-programmable control assembly SPS by means of a position control unit 28. The UMS is arranged directly after the tension S-block 18, in the low-tension region as close as possible to the straightening process, so as to keep the dead space 42 as small as possible. The dead space is the distance needed by the material in order to pass from the bending-straightening apparatus 26 to the measuring roller 36 before an unflatness can be determined at the measuring roller, which then starts a control process in a closed control loop.

From document DE 35 24 382 A1 there is known a stretching-bending-straightening system for a strip material, the system having a low-tension region and a high-tension region. Areas of unflatness are measured in both regions, and on that basis setpoint values for the slipping of the rollers are calculated by processors so as to thereby achieve the most uniform tension possible and thus a uniform quality of the strip. Specifically, the stress is measured on both sides equally, and the setpoint values are determined on that basis; there is no selection means for choosing selectively between low-tension region or high-tension region.

In document DE 22 03 911 A1 there is disclosed a method and a device for controlling the flatness of a metal strip. Areas of unflatness are detected by spacing sensors and there is then an appropriate adjustment of the penetration depth of the straightening rollers. This is achieved by use of a control system, not by a selection of high-pressure region or low-tension region.

From document DE 10 2004 043 150 A1 there is known a measurement system in FIG. 9 which is used in a high-tension region. A roller of the tension S-block 18 arranged after the bending-straightening apparatus 26 is replaced by a measuring roller 40. This roller consists of a solid body. The sensors are arranged at the circumference of the solid roller body, and the entire running surface of the measuring roller 40 is coated with a PU coating. The sensors are able to detect the smallest of force differences in the strip. The determined force values are then transmitted to an analysis electronics unit as analysis unit 34, are processed there accordingly, and are transmitted to a controller C for calculating optimal parameters for the straightening process in a closed control loop. The advantage lies in a much shorter dead space 42 as compared to the above-mentioned UMS system.

OBJECT OF THE INVENTION

Proceeding from this prior art, the object of the present invention is to arrange a stretching-bending-straightening system and a method for the actuation thereof such that the quality of the strips processed by the system is increased.

This is achieved with a stretching-bending-straightening system having the features of claim 1 and by a method for the actuation thereof having the features of claim 10. Advantageous developments are the subject of the dependent claims. The features described individually in the claims are combinable with one another in a technically feasible manner and can be supplemented by explanatory information from the description and by details from the drawings, thus providing further variants of the invention.

The stretching-bending-straightening system has a feed means for feeding a material in strip form into a high-tension region and a low-tension region, wherein the low-tension region is arranged downstream of the high-tension region in the movement direction of the material in strip form. A bending-straightening apparatus is situated in the high-tension region. In addition, a measuring system for determining first measured values is provided in the high-tension region, and a measuring system for determining second measured values is provided in the low-tension region. A controller is provided for determining the deviation of the first measured values from a predefined or predefinable desired value of the bending-straightening result, as well as a controller for determining the deviation of the second measured values from said desired value. Manipulated variables are determined by the one or more controllers so as to minimize the deviations within closed control loops. In other words, at least two measuring systems are thus provided: one in a high-tension region and one in a low-tension region, so as to optimize the quality of the material to be processed, as necessary. Selection means may be used to decide whether the first or the second closed control loop is used for optimization. A selection of this kind may be made depending on certain criteria, which are based either on empirical values or material characteristic values, but also can be created for the first time during the course of the process itself, since, in each closed control loop, measurements are taken in the high-tension region and in the low-tension region at the same time, so that an optimization can be selected on the basis of the characteristic values thus determined. A strip of higher quality can thus be produced easily and conveniently.

It must be considered that a measuring device for the high-tension region was used previously generally only in rolling mills, whereas the solutions known in the prior art excluding rolling mills detect measured values and in particular detect areas of unflatness of the material in the low-tension region, the material having been straightened already coming from the coil by the bending-straightening apparatus situated in the high-tension region. Only the combination of both measuring devices, however, allows an optimal influence depending on the conditions of the strip, the requirements of the material to be manufactured and/or the material properties.

A single controller is preferably provided in order to simultaneously determine the deviation of the first and the second measured values from the desired value, so that the selection means choose the first or the second control loop alternatively. An optimization may thus be implemented in the controller even in the case of slight deviations, such that a switch is made from one control loop to the other, without further synchronization between different control assemblies.

An analysis unit for analyzing the first and/or the second measured values is expediently provided, that is to say more than one analysis unit may also be provided. The selection means are thus enabled to select the first or the second closed control loop depending on the analysis. Both a manual and a semi-automatic or automatic selection constitute potential selection means, depending on what specifications are given to the controller and the analysis unit.

It is furthermore advantageous if display means for displaying the first and second measured values are provided and/or the selection means are provided for manual selection performed by an operator. An operator, on the basis of the display, is thus able to identify at a glance the direction in which the measured values of the two measuring devices are heading and is thus able to decide whether preference should be given to the first or the second control loop.

The measuring system in the high-tension region is preferably formed by a measuring roller arranged after the bending-straightening apparatus. It is advantageous in particular if, to this end, a roller of a tension S-block, which is usually situated after the bending-straightening apparatus, is replaced by a measuring roller having sensors deployed on its circumference, the running surface of the measuring roller being covered by a resilient coating. It is thus possible to determine, practically immediately after the bending-straightening apparatus, whether there is a result of good quality in the high-tension region, so that the dead space between bending-straightening apparatus and measuring system is reduced. If the measuring roller in a preferred embodiment is formed as part of the tension S-block, there is no need for a separate mount for such a roller, and instead the roller provided anyway in the tension S-block may be replaced by the measuring device, which further reduces the costs of the overall structure.

The measuring system for determining the second measured values in the low-tension region should advantageously be arranged after the tension S-block, wherein it is arranged as close as possible to this block. An arrangement of this kind contributes to reducing the dead space, and thus the amount of waste, for this measuring system as well.

It is particularly preferred if the measuring roller used for this purpose has adjacently arranged measuring segments having at least one sensor, preferably having two force sensors, since it is important particularly in the low-tension region to detect the differences over the strip width as exactly as possible over the entire area. Whereas some deformations are not perceptible in the high-tension region on account of the forces occurring there, these deformations are intensified under lower tensile forces in the low-tension region after elastic recovery and may be clearly identifiable there. To this end, a higher resolution is advantageous and may be achieved by the arrangement of the measuring segments.

It is advantageous if storage means for storing operating parameters are additionally provided so as to use previously determined operating parameters for future processes. These operating parameters, for this purpose, are stored in a database, in which the operating parameters are stored together with data regarding the processed material. In this way a data bank and, possibly also supplemented by expert knowledge, a data record may be stored which may be used from the start for comparable materials so as to work on the system from the outset with the best possible approximation. The result may thus be optimized more quickly, and in general the amount of waste may be reduced.

In accordance with the method, the material in strip form is fed to the high-tension region and low-tension region. First and second measured values are determined in the high-tension region and also in the low-tension region, and a deviation from a desired value is determined. On the basis of this deviation, a manipulated variable for the bending-straightening apparatus is calculated for both measuring systems which are able to contribute to an optimization of the result. On the basis of predefined or predefinable criteria, such as a deviation from the desired value, but also empirical values or material characteristic values, a selection is then made between the first and the second closed control loop in order to attain the desired result. Both the advantages of a measurement in the high-tension region and the advantages of a measurement in the low-tension region may thus be considered simultaneously, such that it is possible to decide at all times in which of the control loops an improved result should be attained. Depending on the provided information and the features of the device, the system may then be switched over manually, semi-automatically, or automatically to the relevant control loop so as to attain an optimal result.

The deviation of the first and second measured values is preferably determined by means of a single controller simultaneously for both measuring systems, such that the first or second closed control loop is selected alternatively. In accordance with the method, all information is thus provided at the same time so as to be able to make an informed decision.

The first and second measured values are expediently analyzed on the basis of predetermined criteria in view of achieving a good result, wherein the appropriate control loop is then selected depending on the analysis. Such criteria may be constituted by determined requirements on the sought quality of the strip to be processed, but also may be constituted by material characteristic values or empirical values, which are predefined by the operator or are deducible from expert knowledge, which potentially is stored in a data bank.

For manual selection, the first and second measured values are advantageously displayed to an operator simultaneously, such that the operator may use selection means 48 to choose the control loop optimal for the result that is to be attained. The operator may thus decide, at a glance, which is currently the optimal solution. Since this may change over the course of time, even within the same coil, this process may also be automated and monitored, such that an indication of a suitable switchover time may be output to the operator as necessary.

Since the material to be processed firstly passes through the high-tension region and then through the low-tension region, it is particularly advantageous if the method is operated initially on the basis of the first measured values from the high-tension region in a first closed control loop, until the straightened material in strip form reaches the measuring roller in the low-tension region, such that it is then possible to switch to the second closed control loop in the low-tension region. Whether or not it is actually necessary to switch over at that moment, may be determined on the basis of the determined measured values. The dead space may be further reduced by such a configuration.

It is particularly advantageous if operating parameters already determined on the stretching-bending-straightening system are stored in a data bank jointly with data regarding the material to be processed and may be used again at a later time for the processing of comparable materials. This reduces the tooling and set-up time and optimizes the process such that a good result may be achieved quickly. The knowledge provided in the data bank may optionally be supplemented by expert knowledge, which contains information regarding certain material properties, and thus detailed operating parameters for the stretching-bending-straightening system.

Both the stretching-bending-straightening system and the method may be operated with a program, which is configured and/or programmed with a program code, in order to achieve the desired results and advantages if the program code is executed on a computer, a processor or a programmable hardware component.

Further advantages will become clear from the dependent claims and from the following description of a preferred exemplary embodiment.

SHORT DESCRIPTION OF THE DRAWINGS

The invention will be explained in greater detail hereinafter with reference to an exemplary embodiment of the invention illustrated in the drawings, in which:

FIG. 1 shows a schematic illustration of the arrangement according to the invention of the components of the invention;

FIG. 2 shows a schematic course of the method according to the invention;

FIG. 3 shows a schematic course of a stretching-bending-straightening system according to the prior art;

FIG. 4a, 4b show a three-dimensional illustration of edge undulations and associated fiber lengths on a material to be processed;

FIGS. 5a to 5d show illustrations of middle undulations, edge undulations, edge undulations on one side, and a combination of edge and middle undulations on a material to be processed;

FIG. 6 shows a schematic illustration of a straightening process according to the prior art;

FIG. 7a, 7b show an end-side view and a side view of straightening rollers and support rollers in a straightening process according to FIG. 6;

FIG. 8 shows a schematic illustration of an unflatness measuring system for the low-tension region according to the prior art;

FIG. 9 shows a schematic illustration of a flatness measuring system according to DE 10 2004 043 150 A1.

DETAILED DESCRIPTION OF PREFERRED EXEMPLARY EMBODIMENTS

The invention will now be explained in greater detail with reference to the accompanying drawings. The exemplary embodiments, however, are merely examples not intended to limit the inventive concept to a certain arrangement. Before the invention is described in detail, it is noted that the invention is not limited to the various components of the device or the various method steps, since these components and methods may vary. The terms used here are merely intended to describe particular embodiments and are not used in a limiting sense. In addition, if the singular or an indefinite article are used in the description or in the claims, this also refers to the plurality of these elements, provided the overall context does not clearly indicate otherwise.

In accordance with the invention, both measuring systems for the high-tension and low-tension regions are combined for the first time. This system is characterized preferably by the use of a single controller C, however a plurality of controllers may be used in principle. This, preferably one, controller C is able to analyze the flatness measured values of the measuring roller 40 in the high-tension region 50 and of the measuring roller 36 in the low-tension region 52. The supports of the straightening movement are adjusted on the basis of these values.

The analysis units 34 of the two measuring units are connected to the controller. This receives the flatness values of the two units and, using the measured values of the active measuring unit, calculates the optimal parameters for the straightening process. The system operator preferably determines which of the two measuring units should be used as a basis for controlling the straightening process. The operator is therefore able to use the measuring unit that is better suited according to the requirements and material and may also change the measuring unit during a process. So as to be able to compare the two units with one another for the process currently underway, it is possible to visualize the flatness measured values. To this end, the measured values of the measuring roller 36 in the low-tension region and of the measuring roller 40 in the high-tension region 50 are displayed in graphic form and/or as numerical values, preferably at the same time on a display unit 46.

A more precise adaptation of the supports to the areas of unflatness of the strip is thus achieved by the system according to the invention. In addition it is now possible to use the system that is better suited according to material requirements, material alloy and/or material thickness, and thus to attain optimal straightening results.

In the case of very thin and soft materials, such as aluminum, it could be that areas of unflatness may not be clearly detected due to the high tension. This may be caused by the resilient properties of the strips. If the strip is stretched with the high tension to such an extent that it appears to be flat, areas of unflatness at this moment might not be measurable and might reappear after reduction of the tension as a result of the elastic recovery. In this case it would be possible to change the measuring system during the process and thus improve the process.

A further advantage is that the waste of materials with which better straightening results are attained with the measuring roller 36 in the low-tension region 52 may be permanently reduced. To this end the measuring roller 40 in the high-tension region 50 is firstly activated and is switched over to the measuring roller 36 in the low-tension region 52 after the dead space.

The measuring roller 40 in the high-tension region, by contrast, is suitable for example for high-strength materials. Since the strip is much stronger, the areas of unflatness are not falsified by the high tension. Thus, the measuring roller 40 in the high-tension region 50 may be used for this situation, and the advantage of the much shorter dead space also utilized.

Once the material 10 in strip form has been threaded in, the system may be started. The controller C initially operates with the values of the high-tension measuring roller 40, since the dead space thereof is much smaller. The dead space is understood here to mean the material length that is necessary, due to the control system from an adjustment means, i.e. the bending-straightening apparatus 26, to the measuring point, before a detected unflatness leads to an influencing of the detected unflatness as a result of a control intervention at the bending-straightening apparatus 26. The controller C adjusts the bending-straightening apparatus 26 in accordance with the calculated parameters so as to attain the optimal straightening result. Once the straightened strip has reached the low-tension measuring roller 36, the controller C automatically switches over from the high-tension measuring roller 40 to the low-tension roller 36 and controls the support rollers 32 of the bending-straightening apparatus with the measured values of the low-tension measuring roller 36, provided no other adjustment is specified by the operator by way of the input means 49 or by the stretching bending-straightening system, for example on the basis of results already made known to the movement earlier.

The system operator may at any time intervene manually by way of input means 49 and may adjust the controller C as needed. The operator may also use the input means 49 to input and specify process data. Furthermore, the system operator may create a data bank 44, in which parameters for the process may be stored, for example for specified materials or materials already straightened before on the system. The controller C may thus select the optimal measuring roller 36 or measuring roller 40 automatically in the case of repeated jobs.

Besides the data regarding processes already performed on the system, further data may also be stored in the data bank 44, for example an allocation of certain operating parameters to certain materials or also expert knowledge. Expert knowledge constitutes information relating to how an experienced operator would operate the stretching-bending-straightening system and with which parameters the operator would work in order to attain a good result. Further physical properties may also be specified here, such as the operating speed or temperature-dependent properties.

Since both the measuring roller 40 in the high-tension region 50 and the measuring roller 36 in the low-tension region 52 are engaged and display their measured values, it is possible to interpolate the measured values of the two measuring devices and to compare them with one another by the software. This is made possible for example by forming a mean value for each measuring device and determining this mean value with defined limits with an interval of 50 control cycles, for example. Depending on the result and analysis of the software, the controller C may then decide independently which measuring system is the more suitable one. This switchover may be implemented automatically, or a recommendation may be expressed to the system operator.

FIG. 2 shows schematically a method sequence. In the step 100, material 10 in strip form is fed to a high-tension region 50 and to a low-tension region 52. The material thus fed is measured in step 101 by means of a measuring device in the high-tension region, wherein flatness deviations are determined as first measured values. After the high-tension region the material in strip form passes into the low-tension region 52, and the flatness deviations are likewise measured there in step 102. This leads to the second measured values.

In step 103 the flatness deviations are compared with a desired value for the flatness deviations. If the flatness deviation is less than or equal to the desired value, the stretching bending-straightening system is operated with these operating parameters. If the desired value is not observed, a choice is made in step 104, preferably on the basis of predefined criteria, whether the result, and thus the flatness deviation, should be influenced with the control system in the high-tension region or in the low-tension region. Depending on which system is selected, the manipulated variable for the high-tension region 50 or the low-tension 52 is calculated either in step 105 or in step 106. The manipulated variable is then applied in step 107 to the bending-straightening apparatus 26, and the method then jumps back to step 101 and 102, so as to measure the flatness deviations in the high-tension region 50 or in the low-tension region 52. The method then starts again.

Information originating from a data bank 44, into which operating parameters from earlier processes, material characteristic values or also expert knowledge have been input, may also be applied for the selection of the control system in step 104 and the determination of the manipulated variable in steps 105 and 106.

It is self-evident that this description may be subject to a very wide range of modifications, alterations and adaptations which lie within the scope of equivalents to the accompanying claims.

LIST OF REFERENCE NUMERALS

• 10 material in strip form
• 12 undulation
• 13 middle undulation
• 14 edge undulation
• 16 brake S-block
• 18 tension S-block
• 20 decoiler
• 22 measuring device
• 24 movement direction
• 26 bending-straightening apparatus
• 28 recoiler
• 30 straightening roller
• 32 support roller
• 34 analysis unit
• 36 measuring roller
• 36 a measuring segment
• 38 position control unit
• 40 measuring roller in the high-tension region
• 42 dead space
• 44 data bank
• 46 display unit
• 48 selection means
• 49 input unit
• 50 high-tension region
• 52 low-tension region
• L_ref reference length
• ΔL length difference
• C controller
• SPS memory-programmed control assembly
• 100 to 108 method steps

Claims

1.-16. (canceled)

17. A stretching-bending-straightening system, having a feed means for feeding a material in strip form in a movement direction into a high-tension region and a low-tension region, wherein the low-tension region is arranged downstream of the high-tension region in the movement direction,a bending-straightening apparatus, which is situated in the high-tension region,at least one measuring system for determining first measured values in the high-tension region,a controller, which is intended and suitable for determining a deviation of the first measured values from a predefined or predefinable desired value of the bending-straightening result and for determining at least one manipulated variable for the bending-straightening apparatus depending on the determined deviation within a first closed control loop,an adjustment means for influencing the manipulated variable,wherein there is provided in addition at least one measuring system for determining second measured values in the low-tension region,

18. A stretching-bending-straightening system in accordance with claim 17, wherein the controller is one single controller, which is intended and suitable for determining simultaneously the deviation of the first and the second measured values from the predefined or predefinable desired value, and in that the selection means are intended and suitable for selecting the first or the second closed control loop alternatively.

19. A stretching-bending-straightening system in accordance with claim 17, wherein at least one analysis unit for analysing at least one of the first or the second measured values is provided, and wherein the selection means are intended and suitable for selecting the first or the second closed control loop depending on the analysis.

20. A stretching-bending-straightening system in accordance with claim 17, wherein display means for displaying the first and second measured values are provided.

21. A stretching-bending-straightening system in accordance with claim 17, wherein the selection means are provided for manual selection by an operator.

22. A stretching-bending-straightening system in accordance with claim 17, wherein the at least one measuring system for determining the first measured values in the high-tension region is formed by a measuring roller arranged after the bending-straightening apparatus.

23. A stretching-bending-straightening system in accordance with claim 22, wherein a roller of a tension S-block is replaced by the measuring roller having sensors deployed on its circumference, the running surface of the measuring roller being covered by a resilient coating.

24. A stretching-bending-straightening system in accordance with claim 17, wherein the at least one measuring system for determining the second measured values is formed by a measuring roller arranged after the bending-straightening apparatus and after the tension S-block in the low-tension region).

25. A stretching-bending-straightening system in accordance with claim 24, wherein the measuring roller has adjacently arranged measuring segments having at least one sensor.

26. A stretching-bending-straightening system in accordance with claim 25, wherein the at least one sensor comprises two force sensors.

27. A stretching-bending-straightening system in accordance with claim 17, wherein storage means for storing the operating parameters adjusted as a result of the first or second closed control loop are provided, and wherein a data bank is provided, which is intended and suitable for storing these operating parameters together with data regarding the material processed by these operating parameters.

28. A method for operating a stretching-bending-straightening system, said method comprising the steps: feeding a material in strip form in a movement direction into a high-tension region and a low-tension region, wherein a bending-straightening apparatus is arranged in the high-tension region, and wherein the low-tension region is arranged downstream of the high-tension region in the movement direction,determining first measured values in the high-tension region,determining a deviation of the first measured values from a predefined or predefinable desired value of the bending-straightening result,determining at least one manipulated variable for the bending-straightening apparatus depending on the determined deviation within a closed control loop,determining second measured values in the low-tension region,determining a deviation of the second measured values from the predefined or predefinable desired value of the bending-straightening result,determining the at least one manipulated variable depending on the determined deviation within a second closed control loop,selecting the first or the second closed control loop in order to reduce the deviation of at least one of the first or second measured values from the predefined or predefinable desired value.

29. A method in accordance with claim 28, wherein the deviation of the first and the second measured values from the predefined or predefinable desired value is determined simultaneously by means of one single controller, and wherein the first closed control loop or the second closed control loop is selected alternatively.

30. A method in accordance with claim 28, wherein the first and the second measured values are analyzed on the basis of predetermined criteria in view of achieving a bending-straightening result, and wherein the first or the second closed control loop is selected depending on the analysis.

31. A method in accordance with claim 28, wherein the first and second measured values are displayed to an operator simultaneously.

32. A method in accordance with claim 28, wherein the first closed control loop or the second closed control loop is selectable manually by an operator.

33. A method in accordance with claim 28, wherein the method is operated initially on the basis of the first measured values from the high-tension region in the first closed control loop, until the straightened material in strip form reaches the measuring roller in the low-tension region, and wherein a switch is then made to the second closed control loop in the low-tension region.

34. A method in accordance with claim 28, including storing, in a data bank, operating parameters already determined in advance during operation of the stretching bending-straightening system, jointly with data regarding the material processed with said operating parameters, and using the stored data for the processing of comparable materials.