WO2008119090A1

WO2008119090A1 - Method for establishing a setup parameter value for a bending press

Info

Publication number: WO2008119090A1
Application number: PCT/AT2008/000104
Authority: WO
Inventors: Burkhard Heller
Original assignee: Trumpf Maschinen Austria Gmbh & Co. Kg.
Priority date: 2007-03-30
Filing date: 2008-03-25
Publication date: 2008-10-09
Also published as: EP2134483B1; AT505743A1; EP2134483A1; AT505743B1

Abstract

The invention relates to a method for establishing a setup parameter value (14) for a bending press (2), according to which at least one setup parameter value (14) for the bending press (2), particularly the immersion depth of a die (23) of the bending press (2), is established by a control device (3) from at least one characteristic (7) of a workpiece to be bent in a bending process and a specified value (10) for a target variable (11) on the bent workpiece (6), whereby a characteristic (7) is formed by the electromagnetic reaction of the workpiece (4) to an alternating electromagnetic field generated by an exciter unit (21) and penetrating the workpiece (4), said reaction being determined as a measured value (9) by eddy current measurement using a sensor unit (22). After partial or complete performance of the bending process, when the workpiece (6) is relieved of load, an actual value (16) of the target variable (11), particularly the bend angle (12), is measured and linked to the measured value (9) of the eddy current measurement and to the setup parameter value (14) in effect prior to relieving the load.

Description

Method for determining a setting parameter value of a bending press

The invention relates to a method for establishing an adjustment parameter value of a bending press according to the preamble of claims 1, 8 and 11 and to a production device according to the preamble of claim 25, in particular suitable for carrying out the method according to the invention.

A fundamental problem with all forming processes is the springback of the workpiece at the end of the forming process by the elastic portion of the deformation of an elasto-plastic material. When bending workpieces, in most cases sheet metal blanks, on bending presses between a punch and a die with a V-die, the workpiece must be deformed beyond the desired bending angle to be achieved after relief, because after elimination of the forming force, the bending angle on the workpiece changed by the springback against the pressed state.

The advantage of this bending process, to be able to achieve different bending angles by different immersion depths of a punch or different bending forces with a single tool set, is faced with the disadvantage that the angular accuracy depends on many different influencing factors. These are on the one hand workpiece-related influences or parameters, such as Sheet thickness, yield strength, tensile strength, uniform elongation, modulus of elasticity, solidification exponent, rolling direction, etc., but also process-related or machine-related influences, such as. Die width, run-in radius, punch radius, stamping force, machine deformation, forming speed, etc. In particular, the workpiece properties are subject to relatively high fluctuations due to the production, which have a direct effect on the achievable bending angle.

An additional complication in the free-bending process is that excessive deformation, ie too sharp a bending angle, must be avoided at all costs, since a correction by bending back is generally not possible. In the adjustment of the bending angle, in practice, one usually approaches the desired bending angle with caution, in that the deformation is carried out to a lesser extent for the time being, ie by a less deep dipping of the stamp into the die or a lower bending force a rather blunt bending angle is adjusted after opening the bending tools of the actual reached bending angle is measured and then, if necessary, a Nachbiegevor- with deeper immersion of the punch in the die or higher bending force is performed. The requisite readjustment of the machine setting parameters is in many cases based on the experience of the operators, who estimate and manually adjust the correction value for setting the bottom dead center of the punch movement or the bending force to be applied on the basis of the measured deviation from the setpoint angle, or programmed correction values in the machine control be used for post bending. Since information about the forming behavior of the workpiece is already available from the first bending process, in most cases a single bending is sufficient to achieve the required bending angle.

In order to avoid post bending operations as much as possible by already achieving the required set bending angle in the first bending operation, it is therefore attempted to incorporate as much information as possible about the workpiece properties when determining the setting value of the bending machine.

EP 1 401 593 B1 describes a method for controlling the stroke of a press brake, in which the difference in thickness between the real thickness of a workpiece and the nominal thickness of a workpiece is calculated by the actual position of the movement of the punch, in which there is a predetermined change of a Parameters, eg of the pressure at the pressing cylinders is compared with the theoretical position of said movement, in which it should come to this change of the parameter. Further, during the bending operation by an electronic control device, the measured values of the movement of the punch and the parameter, e.g. the pressure of the pressing cylinder, processed during the phase of plastic deformation of the just bent workpiece. These

Measurement data are compared during the bending process with the data of a reference bending process, in which the target bending angle was achieved, and calculated for deviations from the electronic control device, a correction value for the bottom dead center of the movement of the punch. By the simultaneous measurement of the punch movement as well as the pressure correlating with the bending force on the press cylinder and the resulting Umformkraft-Umformweg- course on the one hand, the thickness of the workpiece, and the elastic behavior (modulus of elasticity) of the workpiece can be determined and the set values of the press be corrected if necessary. The disadvantage of this method is that the determination of the Umformkraft-Umformweg- course, for example, by vibrations in the drive system of the press bar or unpredictable slip-stick effects between the press tool and workpiece is fraught with uncertainties and to carry out the required measurements, a reduction in the pressing beam speed is required.

From DE 37 81 887 T2 an electronic control system for a press brake is known, which also measures the position of the press ram and scans the force acting on the workpiece, can detect deviations from a model formed by measurements based on curved test workpieces and optionally correction values for determines the stamp movement. The control system works adaptively by relating data determined on test workpieces on the deformation force profile, workpiece thickness and bending angle obtained at certain setting values and then calculates the bottom dead center of the punch movement required for achieving a specific desired bending angle in production workpieces after determining the deformation force profile and the workpiece thickness. Also in this method, the determination of the Umformkraft-Umformweg-course for the same reasons is subject to uncertainty, which in turn leads to deviations of the actual bending angle of the target value.

From the field of material testing is known to inspect non-destructive material defects but also mechanical-technological material properties of conductive, especially metallic workpieces by means of magnetic inductive eddy current testing. The determination of material characteristics is based on experimentally determined correlations between electromagnetic and mechanical-technological properties of the workpieces. From WO 2004/101193 a spring coiling machine is known in which a measured variable, which is detected by a measuring sensor of a measuring device arranged in front of the wire transducer, can influence the wire-forming machine in order to keep the geometry of produced springs within a predetermined desired range. In one embodiment, the measuring device comprises means for detecting measured variables that can be influenced by induction or eddy currents.

The Research Disclosure "Adaptive Correction During Forming" (Database Number 471002) reports on a method for adapting the parameters of a forming process to the actual properties of the starting material, using a vortex Current / induction measurement method, the formability or the deformation behavior of the starting material is determined. It also correlations between electromagnetic and mechanical-technological properties of the starting material are used. For example, an eddy current / induction meter is used to check the starting material and read the measured value into a model that describes the relationship between the measured and set values of the forming process. The model then supplies the adjustment values suitable for the currently determined formability of the starting material, which are forwarded to a machine control and automatically adjusted on a forming machine. This method can also be used, for example, for bending sheet metal or sheet metal strips.

The object of the invention is to provide a bending method which can achieve a particularly high bending angle accuracy by determining fluctuations in the properties of the starting material and taken into account in the bending process and, if appropriate, can be subsequently introduced on existing systems with only minor structural measures.

This object of the invention is achieved by a method with the measures of the characterizing part of claim 1. The essential advantage here is that, according to the eddy current measurement on the workpiece, which is carried out to determine workpiece properties and subsequent establishment of the setting parameter value, the estimation of the deformation behavior of the workpiece carried out by means of the model of the bending process is checked for correctness by a concrete measurement of the actual value of the target becomes. The validity or validity of the model used to determine the adjustment parameter can thereby be monitored and, if necessary, refined or corrected. This is particularly advantageous if the model of the bending operation is still in the production phase and the application without the measurement of the target size in the production still gives rise to uncertain setting parameter values for the bending machine.

After prolonged use of the method according to the invention, the model has a high prediction accuracy and the setting parameter values determined therewith result in actual values of the target variable which are very close to the setpoint value. In this mature state of the model, the number of measurements of the actual values of the target size can be reduced and in particular, the workpieces can be bent with high accuracy solely on the basis of the setting parameter values determined with the model for the respective workpiece.

In this determination of the setting parameter value for achieving the target value of the target quantity, e.g. the desired bending angle, without measurement of the actual value, the final determination of the setting parameter value takes place before the actual bending process, whereby it can be carried out at full speed and without interruption. The invention makes use of the insight that the electromagnetic properties of a workpiece accessible via the eddy current measurement with geometrically and / or mechanically technological workpiece properties, such as, for example, Sheet thickness, yield strength,

Tensile strength, uniformity, modulus of elasticity, solidification exponent or rolling direction of the workpiece correlate and the electromagnetic properties can therefore be used as a parameter of the workpiece for a determination of a Einstellparameterwertes for a bending operation. From a deviation of the measurement result of the vortex flow measurement from a nominal value, it is possible to deduce a corresponding deviation of a mechanical parameter from a nominal value and thereby to correct the setting parameter value with respect to a nominal setting value.

The measurement of the actual value of the target variable, for example the bending angle, can be carried out in particular even after a relief of the workpiece before complete completion of the bending process, ie at an intermediate relief. For example, with a nominal value of the bending angle of 90 °, the bending process at a Bending angle of about 100 ° (obtuse angle) are interrupted and after the withdrawal of the force exerted by the punch on the workpiece bending force, ie in the unloaded state, the actual value of the previously achieved bending angle measured and with the effective before the relief Einstellparameterwert, eg The immersion depth of the punch and the measured value of the eddy current measurement are combined to form a value group. If the measurement results in a bending angle of 102 ° instead of the expected 100 °, this means that the actual formability of the workpiece is smaller than would be expected from the parameters used to determine the setting parameter value.

As possible setting parameters for the bending process, at this point, for example, the stroke or immersion depth of a punch, the maximum hydraulic pressure in the press s cylinders, a maximum applied bending force, forming force or pressing force and a deflection compensation parameter so called a correction value for the crowning of the lower tool to compensate for the deflection of the press beam, the method is not limited to the determination of a single of these adjustment parameters, but also several as well as others Setting parameter values can be set.

The measurement of the actual value of the target variable can be carried out with an automatic measuring device on the bending press, for example, with an integrated into the punch angle measuring device similar to a Innenmesstaster. The time required to carry out the measurement can thereby be kept as low as possible since the workpiece does not have to be removed from the bending press for the purpose of measurement.

The information from the measurement of the target size can now be used to reset the setting parameter value, e.g. in such a way that the measured value is fed to the control device and the bending process is continued with corrected settings, taking into account the deviation of the workpiece from the nominal deformability originally assumed, characterized by nominal values of the workpiece characteristics, by the actual value of the target variable very close to the setpoint. It is thus possible, based on the actual value of the target variable measured after the unloading of the workpiece, to reset the value of the setting parameter value for the continuation of the bending operation by the control device and thereby to carry out an inline correction of the setting parameter value.

A further advantageous variant of the method consists in adapting the model of the bending process based on the actual value of the target variable measured after the unloading of the workpiece and the measured value of the eddy current measurement representing a parameter of the workpiece and the setting parameter immediately before the unloading. The correlations contained in the model from the value of the setting parameter, characteristic of the workpiece from the eddy current measurement and respectively caused thereby value of the target size are quasi supplemented by the relationship determined on the current workpiece, the model thereby subjected to a learning process and thus further improved with each workpiece and, so to speak trained.

For this purpose, it is advantageous if the measured on the workpiece actual value of the target size, the Measured value of the eddy current measurement, possibly further known or determined characteristic of the workpiece and the immediately before the relief acting setting parameter value in the control device are stored in the form of a data set. The model of the bending process is composed of the information of the individual data sets and can be present as a database, or also by analytical methods in a calculation rule that maps the relationship between the result of the eddy current measurement, setting parameter value, possibly further known parameters of the workpiece and value of the target size, be convicted.

The model of the bending operation in the control device may be formed by a multi-data set table or database and serve as a look-up table, by means of which the setting parameter value is determined essentially by searching and evaluating data records having similar values to the current workpiece becomes.

In addition to or instead of data records from setting parameter values and measured target value values used on concrete workpieces, the value table can also include data records that were created using numerical methods, in particular simulation calculation, finite element methods, regression calculation or interpolation calculation. Thus, the model can be built with few measured workpieces and the effort to create the model can be reduced.

The object of the invention is also achieved by a method with the measures of independent claim 8, according to which an estimated value of a characteristic of the workpiece is derived from the measured value of the eddy current measurement and this estimated value is used by the control device in the setting of the setting parameter value. Thus, the result of the eddy current measurement can also be used for the indirect determination of further characteristics of the workpiece, which are used in the definition of the setting parameter value. For example, the result of the eddy current measurement can be used for estimating a mechanical characteristic such as the yield strength used as a characteristic of the workpiece by the controller for establishing the setting parameter value, such as control devices of conventional bending machines with nominal values, for example supplier information, of the workpiece characteristics is performed by default. The determination of this estimate is based on a model The material properties, which include a correlation between the measurement result of the eddy current measurement and mechanical-technological parameters of the workpiece, for example, come from series of tests of material testing in which the results of non-destructive eddy current measurement with results of destructive testing methods of mechanical material properties are related. The model can advantageously be included as a calculation rule or look-up table in a memory of the control device and the evaluation of the eddy current measured value as an estimated value of a mechanical parameter can also be carried out by the latter.

A further development of the aforementioned method consists in linking the estimated value to a nominal value of the same parameter of the workpiece, in particular by forming a weighted mean value, and using this as a parameter for determining the setting parameter value. As a nominal value of the material parameter, for example, the thickness as the geometrical parameter of the workpiece or the proportionality limit RpO, 2 as the mechanical-technological parameter of the workpiece are mentioned at this point. While geometric characteristics such as thickness can still be determined metrologically with manageable effort, the direct determination of mechanical-technological workpiece characteristics on a specific workpiece either not at all or only with disproportionately high effort possible, which is why as a workpiece characteristic for the determination of a setting parameter value for a bending process In most cases, the nominal values announced by a supplier are used, whereby these are always to be regarded as parameters subject to uncertainty, which is why the concrete values of individual workpieces can deviate considerably therefrom. By combining the estimated value derived from the result of the eddy current measurement with the nominal value of the characteristic variable, it is possible to use the information about the workpiece from two different sources and to specify the actual value of the characteristic more accurately, at least statistically speaking.

A determined by means of an eddy current measurement mechanical characteristic of a workpiece can also be used as a parameter of a workpiece for the control of any bending press, beyond also for subsequent processing steps on other processing machines, where this parameter has significant influence, are used. The relationship between results of eddy current measurements and the mechanical characteristics can be determined, for example, by eddy current measurements and subsequent destructive or non-destructive material testing on Probewerkstücken.

Through the formation of a weighted average, each of the two values subject to certain uncertainty - estimated value or nominal value of the parameter - can be included in the calculation with a value, in particular between 0 and 1, depending on the value given to higher significance. For example, in the case of workpieces with known small material fluctuations, the nominal value of 0.75 can be given a higher weight in the formation of the mean value than the estimated value of 0.25 determined from the eddy current measurement.

The object of the invention is further achieved by a method with the measures of independent claim 11, according to which during the bending process a course of a bending force or directly related to this Biegekraftpara- meters, for example, acting in the press beam drive hydraulic pressure, and the control device is fed, wherein the bending force, the bending force parameter or a calculated from the course calculation of a mechanical characteristic of the workpiece selected from a group comprising yield strength, Proportionalitätsgrenze, elongation at break, uniform strain, elastic modulus as a parameter used to reestablish the Einstellparameterwerts before completion of the bending process becomes. As a result of this measurement of the bending force curve, information about the workability of the workpiece can be derived and the actual value of the target variable can be better approximated to the desired value on the basis of the additional information about the forming behavior which is included in the new setting of the setting parameter value. For the mathematical determination of the mechanical-technological parameter from a Umformkraftverlauf there are solutions in the art with which deviations of the material properties of specified nominal values can be well established and therefore can be used for an in-line correction of Einstellparameterwerts.

The respective measured bending force can for example be used directly without calculation of mechanical-technological characteristics of the workpiece to one or more set based on the measured value of the eddy current measurement Einstellparameterwerte for example, in determining a deflection parameter value which is used to adapt the curvature of the lower tool or of the fixed press beam to the deflection of the movable press beam occurring with each bending force exerted. The deformation can be adjusted by actively changing its curvature at the fixed pressing bar, z. Example by adjusting cooperating wedge elements in construction of the fixed press beam or by changing the bending stiffness of the fixed press beam, for example by weakening slots whose effective length is variable by adjustable pressure pieces.

The Umformweg, in the case of a bending press the path of the punch from the

Contacting the still unbent workpiece or the immersion depth is preferably removed by means of displacement sensors in the region of the adjusting device for the movable beam; the forming force or bending force can be measured directly by means of load cells and taking into account the dead weight of the press beam and pressing tools, or indirectly determined by a hydraulic pressure acting in the adjustment or detected in an electric press beam drive power consumption.

A further variant of this method consists in linking the calculated value of the mechanical parameter determined from the course of the bending force with an estimated value of the same mechanical parameter of the workpiece derived from the measured value of the eddy current measurement, in particular by forming a weighted mean value and as a corrected parameter for the renewed Setting the setting parameter value before the end of the bending operation is used to again perform a form of inline correction, whereby the target size is better approximated to the target value

The determination of the estimated value is based, as already described above, on a model of the material properties, which contains a correlation between the measurement result of the eddy current measurement and mechanical-technological parameters of the workpiece, which originate, for example, from test series of material testing. In a similar manner to the above for determining the setpoint parameter value of the workpiece characteristic parameter estimate derived from the eddy current measurement and a nominal value of the same workpiece parameter, in this method variant the calculated value of the workpiece parameter is linked to the estimated parameter of the workpiece parameter in order to determine the setting parameter value. The tax Direction can calculate the link in particular by a weighted average, depending on the choice of weights, the validity of the eddy current measurement or Umformkraftmessung can be rated higher.

In particular, the weighting factors may each assume values between zero and one, i. the determination of the setting parameter value can in extreme cases also depend entirely on one of the two values. In general, however, an equivalent weighting of 0.5 each in the formation of the weighted average will be beneficial.

Furthermore, if the measurement of the bending force takes place accurately and reliably, the calculated value of the mechanical parameter determined from the course of the bending force can be linked to the measured value of the eddy current measurement, and the model of the workpiece properties can be supplemented by this pair of values and thereby adapted the eddy current measurement based estimates of the mechanical characteristic are improved. This influence on the relationship can be effective for a single bending operation, however, the connection can also be adapted permanently and the method can also be performed self-learning, if with each bent workpiece the result of an eddy current measurement and the setting parameter value with the actual, measured value of the target size is linked. This can e.g. be carried out by measuring the actual bending angle achieved on a workpiece after completion of the bending process and added to the measurement results of the eddy current measurement or the Einstellparameterwerten this workpiece.

In addition, the model of the forming operation can be further refined if the estimated value of the mechanical characteristic and the measured value of the eddy current measurement determined on the same workpiece is stored in the control device in the form of a data set, in particular one containing data sets from other workpieces, the model of the bending process forming table of values or database is added. Thus, with each bent and simultaneously measured workpiece, the bending model based on a correlation between eddy current measurement and workpiece properties can be further improved.

In this way, the development of the forming force during the bending process can be calculated. nete mechanical characteristic of the used to determine the Einstellparameterwerts connection between the result of the eddy current measurement and the value of the target size on the workpiece - the model of the bending process - influence or adapt. For example, the relationship between results of the vortex flow measurement and yield strengths measured by methods of material testing can be supplemented by pairs of values from eddy current measurements and yield strengths or yield strengths calculated during bending operations. By means of these additional value pairs, the meaningfulness of the previously determined relationship and thus also the quality of the setting parameter values increases statistically.

An advantageous development of the previously described method is according to another claim in that at least one characteristic of the workpiece selected from a group comprising workpiece thickness, weight or workpiece surface determined by a measurement before or during the bending process and the control device is supplied and in the determination of the setting parameter value is used. For example, since the thickness of the workpiece as well as mechanical-technological material characteristics directly influence the target size, e.g. has the bending angle, it is advantageous to detect deviations from the nominal thickness before or during the bending process and to take into account when setting the setting parameter value. As a method for thickness measurement, all measuring methods known to the person skilled in the art can be used, using contact or non-contact measuring methods which can be carried out independently of the bending press but also inside the bending press or during the bending process. To minimize the measurement effort while the thickness measurement can be limited to those sections of the workpiece that are mechanically stressed during the bending process. Depending on the setting options of the bending press, it is also possible to carry out several thickness measurements per workpiece and, if the bending press permits, several, optionally different setting parameter values can be defined over the workpiece width.

An expedient embodiment of the method according to the invention is according to another claim in that the eddy current measurement is largely limited to zones in the workpiece which are deformed during the bending process. This can be accomplished by selecting exciter units and multiple sensor units having a high local measurement point resolution and arranged along a straight line. There- the measurement can be essentially limited to the forming zone and thus more accurate setting parameter values can be determined.

It is particularly advantageous if the eddy current measurement is carried out according to a further claim with at least two different, in particular at least ten different excitation frequencies of the electromagnetic alternating field. Since the electromagnetic alternating field influenced by the workpiece and thus also the reaction to the sensor unit is strongly dependent on the excitation frequency of the electromagnetic alternating field and depending on the microstructural properties and thus also the mechanical technological properties of the workpiece at different excitation frequencies for each

Material type results in a typical electromagnetic reaction on the sensor unit, the relationship between results of the eddy current measurement and mechanical characteristics of the workpiece using multiple excitation frequencies can be determined more accurately. By applying at least ten, preferably twenty to thirty different exciter frequencies, a wide frequency spectrum can be covered and the

Estimates for the mechanical characteristic and thus also the accuracy of the achieved bending angle can be improved. In addition, a very high number of excitation frequencies can be used for eddy current measurement, for example, by the exciter frequency is continuously changed from a minimum frequency to a maximum frequency, so a frequency range is traversed, which also results for each material characteristic a typical measurement result that with the interesting parameter of the workpiece can be related. The eddy current measurement is performed, for example, such that the sensor unit comprises a sensor coil and in the eddy current measurement, the change in the impedance of the sensor coil caused by the reaction of the workpiece is determined. For this purpose, the flowing in the sensor coil

Current measured by amplitude and phase, from the change of these values by the approach of the workpiece to be measured to the sensor coil, the electromagnetic properties of the material of the workpiece can be deduced. Since the electromagnetic reaction of the workpiece also acts on the exciter unit, it is also possible for the exciter unit to simultaneously act as a sensor unit, i. the sensor coil is formed by an exciting coil itself.

Another advantageous implementation of the method according to the invention is that the target size used is a geometric parameter obtained on the workpiece selected from a group comprising bending angle, side length, radius of curvature at the bending zone, parallelism or crowning of the workpiece after the bending process. Thereby, the results of the eddy current measurements are directly related to the target of the bending process, allowing the adjustment parameter value required for achieving a particular target value of a target to be identical to those of the eddy current measurement in the case of the workpiece and the bending press identical to previous bending operations can be determined. However, in order to increase the accuracy of the result, it is also advantageous to take other influencing variables, in particular the workpiece thickness, into account in determining the setting parameter value.

A favorable variant of the method is that the relationship between eddy current measurement and the target size of the workpiece - the model of the bending process - is produced by regression calculation and / or correlation calculation from results of previous eddy current measurements on several workpieces and values of the target size measured on the respective workpiece , With the aid of these calculation methods, a large number of measurement results can also be combined and stored, for example. be incorporated into a calculation rule for the setting parameter value. The implementation of this calculation method is easily possible with the electronic control devices used on today's bending machines.

A further advantageous implementation of the method is given by the fact that, according to two further claims, the relationship depicted in the model of the bending process is produced with the aid of a neural network, in particular using a backpropagation process from results of a sequence of bending operations. With the aid of a neural network, nonlinear, multi - parameter relationships, as they are effective in a bending process, can be mapped in a self - learning model, which is also able to take into account deviations of individual workpiece parameters in the determination of the setting parameter value, without the physical relationships between The individual workpiece parameters must be specified in terms of formula or as a calculation rule the calculation system. As an alternative or in addition to a neural network, the definition of the setting parameter value can also be made with the aid of Fuzzy logic control can be used to determine the required corrections in the determination of the setting parameter value to deviations in the characteristics of the workpiece over the values in one or more bending operations on specimens.

It may also be expedient, according to a further claim, to obtain information about the setting parameter value of the bending machine after the eddy current measurement has been carried out on the workpiece, in particular in machine-readable form, e.g. as a barcode. The information relating to the workpiece to be bent, which is obtained from the eddy current measurement, thus reliably remains connected to it, and the method step for carrying out the eddy current measurement can be decoupled from the bending process without time and space, without having to take additional measures for storing measured values and workpiece identification. The attachment of the information may be e.g. done with an inkjet printer or with laser radiation.

Particularly expediently, the method proves to be carried out according to a further claim, the bending process as a free-bending process on a bending press in the form of a press brake. Due to the widespread use of this method and the high number of workpieces processed with it, it is possible in this method within a short time to collect a large amount of data for establishing a correlation between results of the eddy current measurement and values of the target size.

The eddy current measurement, the comparison of the result of the eddy current measurement with the relationship between the results of the eddy current measurements and the values of the target size, the handling of the model of the bending process or the material properties, the setting of the Einstellparameterwertes or the calculation of the mechanical characteristic is advantageous with the electronic control device carried out. The electronic control devices used on modern bending presses offer in many cases sufficient memory and computing power to perform the required calculations in sufficient speed, or are at least prepared for expansion with suitable calculation modules. In principle, these calculations can also be performed without automated computer support, which, however, only makes sense in the initial phase during the development and initial parameterization of the calculation algorithms. A further object of the invention is to provide a production device for bending, with which a sufficiently precise bending angle of workpieces to be bent is achieved already during the first bending operation.

This object of the invention is achieved by a manufacturing device according to the characterizing features of claim 25. The surprising advantage of this production device is that the Wirbelstrommesseinrichrung coupled to an electronic control device of a bending press can be spatially arbitrarily arranged and automatically taken over the results of the eddy current measurement on a workpiece to be bent by the electronic control device of the bending press and by estimating the forming properties by an eddy current measurement and based on fixing a setting parameter value of the bending press, the angular accuracy of the bending press is increased. For example, the eddy current measuring device may be located away from the bending press, e.g. in the area of an upstream laser cutting machine, in which the process-related lying time for the eddy current measurement is used. By a correspondingly small structural design of the eddy current measuring device but this can also be arranged directly in the field of bending tools, whereby the eddy current measurement takes place immediately before the actual bending operation.

To carry out reliable eddy-current measurements, it is advantageous if according to a further claim the eddy-current measuring device comprises an excitation unit for generating an electromagnetic alternating field acting on the workpiece and a sensor unit for detecting the reaction to the alternating field caused by the workpiece. In general, these are two separate elements which, in addition, may be largely shielded from one another electromagnetically, whereby the sensor unit essentially only picks up or measures the electromagnetic alternating field influenced by a workpiece. However, as already mentioned above, it is also possible for the excitation unit and the sensor unit to be formed by one and the same element.

According to another claim, the sensor unit may comprise a sensor coil and / or a Hall sensor for measuring the magnetic field, wherein the measurement sensitivities are selected according to the material groups to be measured. For carrying out reliable eddy current measurements, it is advantageous if the exciter unit and the sensor unit are mounted in a flexible manner, in particular also with a movable suspension, in particular with a cardan suspension on the eddy current measuring device. This measurement errors are largely avoided by undefined air gaps between the workpiece and the eddy current measuring device, which can easily occur in a rigid suspension, if the positioning of the workpiece is not quite accurate or this form deviations.

The measuring sensitivity of the eddy current measuring device can be further improved by the suspension consists essentially of non-magnetic material and the measuring fields are essentially influenced only by the workpiece and not by the eddy current measuring device itself.

An expedient embodiment of the invention is according to another claim in that the eddy current measuring device is arranged in the region of the machine frame, the fixed beam, a positioning device or a depositing station for workpieces. This arrangement in the immediate area of the bending press provides short paths for the operator of the machine as well as for the workpieces and also allows easy connection of the eddy current measuring device to the electronic control and monitoring device, which is also arranged on the bending press in most cases.

In order to also be able to measure a bending force curve with the production device if necessary, the bending press comprises a force measuring device for measuring the bending force exerted on the workpiece by the bending tools, and the force measuring device is communicatively connected to the control device. In this case, the force measuring device

Force sensors for direct measurement of the bending force or pressure sensors for indirect measurement of the bending force in a fluidic pressure bar drive comprise, these measuring methods are already known from the prior art.

For direct, in particular automatic measurement of the bending angle as the actual value of the target size on the workpiece, the production device, in particular the bending tool of the bending press advantageously comprises an angle measuring device connected to the control device, with which the bending angle can be determined in the unloaded state of the workpiece. The handling of the workpieces on the production facility often means a high repetition rate for the operating personnel with a high level of required attention. It is therefore economically advantageous especially for larger batch sizes, if according to another claim in the field of bending press arranged with a gripping device handling device for handling the workpieces is arranged. As a result, on the one hand strenuous and highly repetitive activity for the operating personnel can be avoided and on the other hand the product quality can be ensured reliably at a high level, since errors due to fatigue and concentration errors are avoided.

For reasons of flexibility, the handling device is preferably designed like an industrial robot with a programmable robot arm, wherein a balanced compromise between sufficient stability to achieve a high repeat accuracy, as well as a slim, space-saving design, so that even small workpieces reliably detected by the gripping device and can be brought to the bending tool. The gripping device can be designed as a gripper gripper, which detects the edge of a workpiece, or as a vacuum suction device, which detects a workpiece by one or more vacuum elements on a surface.

In the event that the production device is equipped with a handling device, it is expedient according to another claim to arrange the eddy current measuring device in the working space of the handling device, whereby the handling of the workpieces can be carried out automatically even when performing the eddy current measurement.

It may also be expedient, according to another claim, to arrange the eddy current measuring device on the handling device, in particular in the region of the gripping device. Thereby, the eddy current measurement can be performed while the workpiece is held by the gripping device, e.g. that is, during feeding from a ready position to the bending tool.

To increase the measuring accuracy of the eddy current field measuring device, an advantageous development of the invention consists in that the eddy current measuring device comprises a holding device for a workpiece. By means of this holding device, a positioning which is the same for all workpieces with respect to the exciter unit and sensor unit is ensured. and random measurement errors, eg by fluctuating air gaps between the workpiece and eddy current measuring device are avoided.

Another advantage is also an embodiment of the production device according to a further claim, according to which the production device, in particular the eddy-current measuring device, comprises a thickness measuring device. As a result, it is possible for the thickness of the workpiece to be measured within the production device and used to determine the setting parameter value of the bending press. In particular, the thickness measurement can take place simultaneously with the eddy current measurement, if the thickness measuring device is structurally connected to the magnetic field measuring device.

According to another claim, it may be advantageous to couple the eddy-current measuring device with a separating device for workpieces to be bent, provided in stacks. In particular, in the case of a production device which is equipped with a handling device, it is advantageous to separate the workpieces to be bent with a separate separating device and thereby to prevent the unscheduled, simultaneous feeding of two or more workpieces into the bending press. Separation can be effected, for example, by means of a special suction head extraction, pneumatically, with the aid of magnetic force, stripping elements or the like. Furthermore, the separation can be facilitated by blowing devices or vibrating devices, which act on the stack. In addition, the separating device can also be equipped with a device for detecting double withdrawals. It is particularly expedient in this case if the provision position for the individual workpieces is formed by the magnetic field measuring device, since this makes it possible to perform the eddy current measurement during the berth time prior to feeding into the bending press with no effect on the time of day.

The invention will be explained in more detail below with reference to the embodiments illustrated in the drawings.

Show it:

1 shows a simplified, schematic illustration of the method according to the invention for determining an adjustment parameter value; 2 shows a simplified flow chart of the method for determining a setting parameter value with two method variants;

3 shows a modification of the method for determining a setting parameter value;

4 shows a simplified view of a production device according to the invention;

5 shows a view of an eddy-current measuring device used in the method according to the invention and in a production device according to the invention with a workpiece to be measured in a simplified, schematic representation;

6 shows an example of a model of a bending process

By way of introduction, it should be noted that in the differently described embodiments, the same parts are provided with the same reference numerals or the same component names, wherein the disclosures contained in the entire description can be mutatis mutandis to the same parts with the same reference numerals or component names. Also, the location information chosen in the description, such as top, bottom, side, etc. related to the immediately described and illustrated figure and are to be transferred to the new situation mutatis mutandis when a change in position. Furthermore, individual features or combinations of features from the different exemplary embodiments shown and described can also represent independent, inventive or inventive solutions.

Fig. 1 shows schematically a manufacturing device 1, comprising at least one bending press 2 and a control device 3, which is connected to the bending press 2 wired or wireless communication via radio. With the production device 1, a workpiece 4 to be bent can be processed by the action of force of a bending tool 5 arranged on the bending press 2 to form a bent workpiece 6. The workpiece 4, 6 consists of sheet metal, which is usually present as a board or blank. The workpiece 4 may consist of any material suitable for bending forming and may be made of semifinished product by any suitable method such as laser cutting, knife cutting, shearing, biting, punching, nibbling, etc. For carrying out the bending operation, the control device 3 uses control signals to transmit setting parameters, which influence the execution of the bending process, to the bending press 2, such as an immersion depth of a bending punch or a bending force exerted on the workpiece 4. In the so-called free-bending method, the actual values of a target variable on the bent workpiece 6 can be influenced by varying a setting parameter value. A main task of the control device 3 is therefore to define one or more setting parameter values in order to approximate one or more actual values of target variables on the bent workpiece 6 as closely as possible to predetermined set values. From practical experience values and / or also from analytical considerations of the forming process, the relationships between the choice of a setting parameter value and the actual values of a target variable that can be achieved are more or less known. An important factor that makes it difficult to adhere to narrow tolerances for the target variables are the unavoidable fluctuations of characteristics of a workpiece 4 to be bent, which can influence the result of a bending process. While, for example, geometric parameters such as thickness or dimensions of a workpiece 4 can still be determined with relatively little effort with sufficient accuracy, the determination of mechanical-technological characteristics, such as flexural strength, yield strength or modulus of elasticity of a concrete workpiece 4 in most applications is much too expensive or impossible.

The parameters of a workpiece 4 to be bent 4 fed to the control device 3 are therefore more or less subject to uncertainties, for which reason it is attempted to take into account as much relevant information as possible about a workpiece 4 when setting a bending process. In the method according to the invention, therefore, a workpiece 4 to be bent is subjected to an eddy-current measurement with the aid of an eddy-current measuring device 8 and the measured value 9 of the eddy-current measurement is fed to the control device 3 as a further parameter 7, the eddy-current measuring device 8 being discussed in more detail below.

Furthermore, the controller 3 is supplied as information about the bent workpiece 6, a target value 10 of a target size 11, which can be influenced by the choice of the settings of the bending press 2. The target size 11 is given in the exemplary embodiment by the bending angle 12 on the bent workpiece 6. Since the setpoint 10 of the bending angle 12 before represents the bending process only a desired state of the bent workpiece 6, this is shown in the control device 3 information shown in dotted lines.

With the aid of a model 13 of the bending process contained in the control device 3, based on the characteristics 7 of a workpiece 4 to be bent, in particular based on the measured value 9 of the eddy current measurement, and the target value 10 of the target 11, a setting parameter value 14, for example an immersion depth 15 of a Bending punch, transferred to the bending press 2. As a result of the subsequently performed bending process, an actual value 16 of the target variable 11, for example of the bending angle 12, is effected on the bent workpiece 6, then the actual value 16 is measured and supplied to the control device 3. The measurement of the target size 11, or its actual value 16 takes place after a discharge of the workpiece 6, whereby the elastic portion of the deformation degrades and the actual value 16 remaining on the bent workpiece 6 can be measured. In the control device 3, a correlation of the measured value 9 of the eddy current measurement, of the setting parameter 14 effective immediately before the relief of the bent workpiece 6 and of the actual value 16 of the target 11 on the bent workpiece 6 takes place, in the exemplary embodiment therefore a combination of measured value 9 of the eddy current measurement The linkage can consist, for example, in merging these values into a data record which maps a relationship between these three values and is used as information about the forming behavior of the workpiece 4, 6 can.

FIG. 2 shows the sequence of the method according to the invention even more precisely in the form of a flow chart. The control device 3 - shown as a block with dashed lines - are supplied before the start of a bending process characteristics 7 of the workpiece 4 to be bent and one or more set points 10 of a target size 11, for example, the bending angle 12. The control device 3 comprises a machine control with the hardware and software usually contained, ie components such as arithmetic unit, memory unit, interfaces for data input output and will not be explained in detail at this point. In addition, the control device 3 comprises the model 13 of the forming process with the bending press 3 in the form of software and data. The model 13 is shown in Fig. 3 as a functional diagram, whereby the relationship between the set Einstellparameterwert 14, for example, the immersion depth 15 of the bending tool 5 of the bending press 2 and their effect on the actual value 16 of the target size 11, for example, the bending angle 12 is illustrated.

The characteristics 7 of the workpiece 4 to be bent in their entirety provide the information about the forming behavior of the workpiece 4, which can not be described by a simple value. Characteristics 7 are the bending process directly or indirectly influencing characteristics such as thickness, yield strength, proportionality limit, Young's modulus, rolling direction, uniform strain, solidification exponent, etc. and the results of the eddy current measurement usable.

A first parameter 7a is predetermined, for example, by a nominal value 17 of a mechanical-technological parameter 7. For example, from supplier information a yield strength of 400 N / mm ² for the workpiece 4 is known. Due to the production-technological fluctuations, however, such information is always associated with a fuzziness, since the cost of the exact determination would be much too high for each workpiece, and therefore always assume a nominal value 17 with a probable range of variation. The nominal values are usually based on one production lot, ie correspondingly many workpieces 4 A yield point on a concrete workpiece 4, which however deviates from the nominal value 17 by about 5%, is not uncommon, for example 380 N / mm ² or 420 N / mm ² However, in a bending process, fluctuating actual values 16 of the target quantity 11 are often not permissible in the case of high accuracy requirements with respect to the permissible deviation of the actual value 16 of the target quantity 11 from the nominal value 10.

Therefore, where it is technically feasible and economically feasible, one or more characteristic values 7b of workpieces 4 to be bent are used in the setting of the setting parameter value 14, which are determined by a measurement on the workpiece 4 to be bent, ie one or more measured values 18 of a parameter 7. As indicated in FIG. 2, a thickness 19 of the workpiece 4 is measured by means of a thickness measuring device 20. The thickness measuring device 20 may comprise measuring means or measuring arrangements with mechanical, electrical, magnetic or optical measuring principle such as laser, as well as combinations thereof and the thickness 19 of the workpiece 4 touching or contactless measure and the control device 3 are supplied. Another parameter 7c, which is supplied to the control device 3, is formed by a measured value 9 of an eddy current measurement carried out on the workpiece 4 to be bent. For this purpose, the workpiece 4 is exposed to an eddy current measuring device 8 an electromagnetic alternating field and measured the reaction of the workpiece 4 to the alternating field. The eddy current measuring device 8 comprises an excitation unit 21 with an excitation coil through which AC current flows and a sensor unit 22 with a sensor coil exposed to the alternating field and is provided with an electronic evaluation device for measuring at least the currents occurring in the sensor coil according to amplitude and phase position or Phase angle and processing of Messsig- signals connected to further processed readings 9, which can be arranged directly in the eddy current measuring device 8, but also other assemblies of the manufacturing device 1 can be assigned. As an alternative to a sensor coil, it is also possible to provide a Hall sensor for measuring the magnetic field caused by the eddy current or influenced by the workpiece 4. The preparation can consist in particular in an amplification of the measurement signals. As a result of the eddy current measurement in the exemplary embodiment, the change in the impedance of the sensor coil based on the change in amplitude and phase of the alternating current in the sensor coil by the reaction of the workpiece 4 against an initial state of the alternating electromagnetic field without workpiece 4 is used.

In eddy current measurement, the excitation unit 21 alternately excites the alternating electromagnetic field with a plurality of, preferably thirty, different frequencies, and measures the corresponding retroactivity of the workpiece 4 to the electromagnetic alternating field with the sensor unit 22 for each exciter frequency. Due to the frequency dependence of the electromagnetic properties, a typical frequency-dependent electromagnetic feedback is obtained for each type of material and its microstructure, based on the previously carried out eddy current measurements and measured actual values 16 of the target 11, e.g. an achieved bending angle 12, a setting parameter value 14 for the bending process of the workpiece 4 can be set.

The implementation of an eddy current measurement requires that the workpiece 4 can influence the magnetic field due to its material properties, in particular its electrical conductivity and its magnetic permeability, which is why the application of the method is particularly suitable for electrically conductive workpieces 4. The application of the Method is not limited to metals or composites of metals and non-metals, as other materials, such as plastics, although small, but effective and thus measurable changes in the measured magnetic field can cause.

The measurement results of the eddy current measuring device 8 and the thickness measuring device 20 are transferred to the electronic control device 3 of the bending press 2, with which in particular the tool movements during the bending process and / or the bending force exerted by the bending tool 5 on the workpiece 4 are controlled and monitored. Furthermore, the control device 3 can be used to control the crowning of a lower tool to compensate for the deflection of the upper, movable press beam. The control device 3 includes, as already mentioned, one or more computing units, memory units, input and output units with interfaces for signal input and signal output, as they are usually used for the control and monitoring of manufacturing equipment, in particular bending presses 2.

The control device 3 and the model 13 of the bending process can be arranged in a common housing, but also spatially removed and data-related, e.g. when the model 13 is included in a separate control of the eddy current measuring device 8.

The target size 11 used in this method is the bending angle 12 obtained on a bent workpiece 6 after a bending operation. In the bending operation, the workpiece 4 in the bending press 2 is pressed by means of a punch 23 into a die 24 with a V-die 25 , The degree of deformation and thus also the achieved bending angle 12 is dependent on the given workpiece properties and tool geometry primarily of the immersion depth 15 of the punch 23 in the die 24. As adjustment parameter value 14, which influences and determines the achieved bending angle 12, in this exemplary embodiment a certain insertion depth 15, ie the deformation away between the first contact point 26 between punch 23 and workpiece 4 and bottom dead center 27 is selected. Alternatively to this, the bending force applied by the punch 23 to the workpiece 4, 6 at the end of the deformation can also be used as the setting parameter value 14 since, like the insertion depth 15, this directly influences the bending angle 12 achieved after the bending process has been carried out, since the punch 23 with higher bending force, continue into the die 24 penetrates and the workpiece 4, 6 is correspondingly more deformed.

The setting of the setting parameter value 14 -in this case the immersion depth 15, which causes the achievement of a specific bending angle 12 -is effected according to the invention as follows:

The result of the eddy current measurement on a workpiece 4 is taken from the eddy current measuring device 8 by the control device 3 and between results of eddy current measurements previously performed on other workpieces 4 and respectively known setting parameter values 14 - in this case dipping depths 15 - achieved actual values 16 of the target size 11, in this case bending angles 12 a Einstellparameterwert 14 to achieve the desired target value 10 of the target size 11, determined in the example of the bending angle 12 of the workpiece 4 to be bent. Due to the known correlation between electromagnetic properties and mechanical-technological properties such. Modulus of elasticity and yield strength

Elongation limit of metallic materials is also a correlation between the measured values 9 of the eddy current measurements, the used Einstellparameterwert 14 and the achievable bending angle 12th

Analogously, the result of the eddy current measurement can be used to determine the bending force or a deflection compensation on the bending press 2 as setting parameter value 14.

To improve the bending accuracy, the actual value 16 of the target 11, measured in the example of the bending angle 12, is also supplied to the control device 3 and in this with the measured value after performing a bending operation, either after complete completion or at an intermediate relief on curved workpiece 6 9 of the eddy current measurement as well as the effective immediately before the discharge of the bent workpiece 6 on the bending press 2 setting parameter value 14 linked.

This feedback of the result of the bending operation can now be used, in the case of an intermediate relief for the rest of the bending process, the setting parameter value 14 with the now additional information about the forming behavior of the workpiece 4, 6 redetermine, especially if the actual value 16 of the target size 11 deviates significantly from the expected actual value based on the original characteristics.

In addition to this feedback for the purpose of possibly redefining the setting parameter value 14, the linkage can also be to adapt the model 13 of the forming operation to the eddy current measurement on the basis of the actual value 16, the immediately before the relief effective setting parameter value 14 and the measured value 9 these values will be added to from previous bends or an assumed relationship between these values. These values can be used as data points to analyze and correct the correlations and dependencies used so far between them.

The bending accuracy increases enormously by this return of the bending result with the effect of a control process and the model 13 of the bending process is thereby constantly improved.

After a sufficient number of bending operations with the described method, the model 13, that is to say the relationship between measured values 9 of the vortex current measurements, setting parameters 14 and actual values 16 of the bending process, is so mature that the measurement of the actual values 16 can be dispensed with and the bending operations can be carried out even more economically. Bending to correct the bend angle 12 is generally unnecessary at this stage.

The model 13 with the relationship between measured values 9 of the eddy current measurements and the actual values 16 of the target variable 11 on the workpieces 4, 6 - in this case the bending angles 12 - can be contained in the control device 3 in various ways.

The measurement results of previously performed bending processes, for example in a test or training phase on trial workpieces, are stored together with the respective adjustment parameter values in data records from which the model 13 is determined by regression calculation and / or correlation calculation and used to determine the adjustment parameter value 14. Another possibility of constructing the model 13 is, after bending operations on workpieces 4, 6, to transmit measured values 9 of the eddy-current measurements, the setting parameter values used and the measured actual values 16 of the target variable 11, ie the bending angle 12, to a self-learning neural network, that is trained with the use of a back-propagation process in such a way that the measured parameter value 14 can be determined by the electronic control and monitoring device 3 from measured values 9 of an eddy-current measurement.

A modification of the previously described method for determining a setting parameter value 14 is to detect a bending force profile 28 during the bending process - shown in dashed lines in FIG. 2, whereby information about the forming behavior of the workpiece 4, 6 can likewise be obtained , The measure to further increase the bending angle accuracy thereby consists in detecting the course of the bending force as a function of the workpiece deformation during the bending process and from this a calculated value of a mechanical parameter 7 of the workpiece 4, 6, in particular the yield strength of the workpiece 4, 6 and take into account in the determination of the setting parameter value 14. The bending force may e.g. be measured directly by load cells, strain gauges, piezosensors in the pressing beam drive or calculated by a hydraulic pressure of the pressing beam drive or the power consumption of an electric pressing beam drive; the workpiece deformation by a displacement measuring device, which measures the displacement of the movable press beam relative to the machine frame. This information about the deformation behavior obtained directly from the workpiece 4, 6 to be bent can be used to establish the setting parameter value 14. This metrologically determined yield strength is often more meaningful than the nominal values 17 of the strength announced by the supplier of the material, and the setting of the setting parameter value 14 is therefore possible with higher accuracy. This measure can be used according to the invention alternatively for returning the actual value 16 of the target size 11, but also be used in addition.

In addition, this information obtained directly from the bending process can be used to modify the relationship between measured values 9 of eddy current measurements and the target variable 11, ie the method can be designed to be self-learning by evaluating the individual bending processes. For this purpose, the actually achieved bending angle 12 is after measured by a suitable angle measuring device installed in the bending tool 5, and together with the measured values 9 from the eddy current measurement and the other machine settings determined on the basis of the parameters, the previously used model 13 between measured values 9 of the eddy current measurement, Setting parameter value 14 and actual values 16 of the target size 11 - the bending angle 11 - added.

3 shows a further method for determining an adjustment parameter value 14, which uses an alternative use of the measured values 9 of the eddy current measurement in comparison to the previously described methods. In this case, these are used to determine an estimated value 29 for a mechanical characteristic 7, in particular the yield strength or yield strength, and to use this for determining the input parameter value 14 for the control device 3. By means of a calculation algorithm contained in the control device 3 then the setting parameter value 14 - in this case, the immersion depth 15 - set. The relationship between measured values 9 of the eddy current measurement and the mechanical parameter 7, in particular the yield strength or the yield strength used for determining the estimated value 29, is defined by a material model 30. This can be determined like the model 13 of the bending process on trial workpieces or based on analytical considerations. The actual yield strength is determined, for example, by destructive tensile testing. The estimated value 29 is calculated in

Sequence with a nominal value 17 of a workpiece characteristic 7 linked, in particular from both a weighted average value formed as a characteristic 7d and the control device 3 supplied or calculated by this itself.

FIG. 4 shows a production device 1 for the angularly accurate bending of workpieces, in particular according to the method described above. This comprises a bending press 2, in particular in the form of a press brake for freeing workpieces 4, 6 between a punch 23 and a die 24 with a V-die 25. The bending press 2 consists essentially of a machine frame 31, a machine frame 31 on the ho arranged horizontally, the die 24 carrying, fixed pressing beam 32, a horizontally disposed, the punch 23 carrying, movable pressing beam 33, by means of at least one adjusting device, such as a fluidic pressing beam drive 34, relative to the machine frame 31 and in the direction of the fixed press beam 32. The adjusting device 34 comprises a guide arrangement, by means of which the movable pressing beam 33 is guided on the machine frame 31 and an adjusting drive, which is preferably designed as a hydraulic drive, but also designed as an electrically driven Hubspindelantrieb can. Furthermore, the adjusting device 34 comprises a displacement measuring device 35, with which the

Position of the movable press beam 33 with respect to the machine frame 31 and the fixed press beam 32 can be measured and transmitted to the control device 3.

For positionally accurate alignment of the workpieces 4 in the bending press 2, a positioning device 36 is arranged in the region of the fixed press beam 32, which has numerically controlled stops for the workpieces 4 to be bent by the control device 3, so that these when inserting the correct position with respect to punch 23 and die 24. The positioning device 36 is preferably arranged as a back stop, on the rear side of the pressing bars 32, 33 facing away from the operator of the bending press 2.

The manufacturing device 1 further comprises a handling device 37, e.g. in the form of a programmable robot arm, the movement space of which is dimensioned so as to grasp workpieces 4 individually from a supply position 39 by means of a gripping device 38, to the bending press 2, to guide the workpieces 4 to be bent during the bending operations, and to workpieces 6 bent after the bending operation Remove bending press 2 and move to a storage position, not shown. The gripping device 38 brings the required holding force on the workpieces 4, 6 in the embodiment by vacuum suction, but there are also grippers used, the choice is influenced by the position of the bending edges on the workpiece 4, and the surface of the workpieces. 4

Furthermore, the production device 1 comprises at least one eddy-current measuring device 8 connected to the control device 3, on which a workpiece 4 to be bent is measured prior to the bending process or at least before the bending process is completed in order to determine an adjustment parameter value 14 of the bending press 2 based on the measured value 9 of the eddy-current measurement , In order to determine the setting parameter value 14, an accessory produced at a previous time and contained in a model 13 of the bending process is determined. Relationship between measured values 9 of eddy current measurements carried out on workpieces 4, actual values 16 of a target variable 11 measured on these workpieces 4 and adjustment parameter values 14 used in the process are used.

As already described above, the eddy-current measurement (see also FIG. 5) consists in detecting the electromagnetic reaction of the workpiece 4 to a defined electromagnetic alternating field. In this case, a workpiece 4 is penetrated by an alternating electromagnetic field generated by an exciter unit 21 of the eddy current measuring device 8, which is influenced by the workpiece 4, e.g. in the case of a ferromagnetic workpiece 4 by the eddy currents induced in the workpiece, which themselves cause an electromagnetic alternating field which is superimposed on the exciter alternating field. With the help of a sensor unit 22, this effect of the workpiece 4 can be measured on the alternating field. The excitation unit 21 and the sensor unit 22 preferably comprise coil elements with which the required magnetic field strengths for excitation or measurement sensitivities are easily realized. The measured variable or measured value 9 of the eddy-current measurement is preferably the current intensity occurring in a coil element of the sensor unit 22 and the phase angle in the coil element relative to the phase angle of the exciter field, ie a reaction by an electromagnetic impedance of the workpiece 4.

Notwithstanding the embodiment described above, it is also possible, for example, to equip the sensor unit 22 with a Hall sensor with which the resulting alternating field is measured.

Since the electromagnetic effects in a workpiece 4 and thus also measured values 9 of the eddy current measurement show a strong dependence on the frequency of the excitation field, the eddy current measurement is carried out at several, for example, at thirty different excitation frequencies of the electromagnetic alternating field to provide a meaningful relationship between measured values 9 of the eddy current measurements and to obtain the target size (s) 11 of the workpieces 4, and possibly to be able to determine a further relationship between measured values 9 of the eddy current measurement and mechanical characteristics 7 of the workpieces 4.

For establishing the relationship by means of the magnetic field measuring device 8, the control Device 3, as well as the determination of the setting parameter value 14 of the bending press 2, in particular the immersion depth 15 on the workpiece 4 and the bottom dead center 27 of the movement of the punch 23 and the bending force to be transmitted from the punch 23 to the workpiece 4 at this point to the referenced above description of the method.

An electronic evaluation device for processing the measurement results of the eddy current measurement may be contained in the eddy current measuring device 8 itself, but may also be formed in the control device 3, which is connected to the magnetic field measuring device 8 via interfaces 40. The transmission of the measured values 9 or of the processed measurement results from the eddy current measuring device 8 to the control device 3 can be conducted between the interfaces 40 in a wired manner, but also wirelessly via a transmitting and receiving device with a transmission technology such as transmission. Bluetooth, wireless LAN, infrared or similar.

5 shows a view of an eddy-current measuring device 8 used in the method according to the invention and in a production device 1 according to the invention.

The workpiece 4 is in the illustrated embodiment on the top of the eddy current measuring device 8 and directly above the exciter unit 21 and the sensor unit 22 contained therein. Thus, the measured workpieces 4 always lie flat on the eddy current measuring device 8 during measurement and random measurement errors due to fluctuating distances to Excitation unit 21 and the sensor unit 22 are avoided, the eddy current measuring device 8 at least one holding device 41 for fixing the workpieces 4. This can e.g. be formed by vacuum suction 42 and / or magnets 43, which ensure the uniform and reliable contact between eddy current measuring device 8 and workpiece 4. The exciting unit 21 and the sensor unit 22 can be mounted on elastically yielding or gimbals movable suspensions to the eddy current measuring device 8, which can be achieved even with thick metal blanks as a workpiece 4 a good investment.

In the described embodiment, the thickness measuring device 20 is arranged on the eddy current measuring device 8, whereby the two measurements can be carried out simultaneously, but the thickness measuring device 20 can also be at a different position within the Manufacturing device 1, in particular be arranged in the movement space of the handling device 37.

FIG. 5 further shows that the measurement results of the eddy-current measurement can be transmitted from the interface 40 via the line 40, but also additionally or alternatively via a transmitting and receiving device 44 to the interface 40 on the control device 3. The transmitting and receiving device 44 can use the already mentioned above wireless transmission technologies Bluetooth, wireless LAN, infrared or the like.

As illustrated in FIG. 4, the eddy current measuring device 8 can form the provisioning position 39 on which workpieces 4 for the operator or a handling device 37 are provided. Thus, only one workpiece 4 is introduced into the bending press 2, it is advantageous to perform a separation of the workpieces 4. This is performed by a singulator 45, which removes a workpiece 4 from a stack and transfers them to the ready position 39. To monitor the singulation process, the singulator 45 may comprise means for detecting double picks, e.g. in the form of a thickness measurement for the separated workpiece or a device for measuring the height of the stack or its change after removal of a workpiece. 4

FIG. 6 shows an example of a model 13 or its use for defining an adjustment parameter value 14 of a bending press 2 in the form of a relationship represented in a Cartesian coordinate system. On the horizontal abscissa, the variable setting parameter 11, for example the immersion depth 15 of the punch 23, is plotted, while the target variable 11, for example the bending angle 12, is plotted on the vertical ordinate. Based on a nominal forming characteristic curve 46, which is determined on the basis of the characteristics 7 of a workpiece present before the bending process, a nominal setting parameter value 47 is required to achieve a predetermined target value 11. However, the bending process is not performed with this nominal setting parameter value 47, but instead with a measuring setting parameter value 48 in which the target variable 11 still has a clear distance from the setpoint value 10. With this measurement setting parameter value 48, a nominal actual value 49 of the target quantity 11 would result on the basis of the assumed nominal deformation characteristic 46. If the measuring However, if the actual value results in a deviating measurement actual value 50 of the target variable, it is concluded that the nominal deformation characteristic 46 only insufficiently describes the actual formability of the workpiece 4, and with the nominal setting parameter value 47 the setpoint value 10 is missed at the end of the bending process will be.

In order to set or correct the setting parameter value 14 for the remaining bending process in such a way that the setpoint value 10 of the target size 11 approximates as closely as possible, a corrected actual forming characteristic 51 is now determined on the basis of the measured actual value 50 obtained with the measured setting parameter value 48 Help of which the corrected setting parameter value 14 is determined. This deviation of the actually determined formability from the originally expected formability of the workpiece can be assumed in a simplified manner as a parallel displacement of nominal deformation characteristic 46 by the data point determined from measurement setting parameter value 48 and measured actual value 50, from which the actual deformation characteristic 51 arises.

In addition to the correction of the setting parameter value 14 described here after a partially completed bending process, the actual deformability of the workpiece 4 actually determined in the form of the measured data parameter 48 and actual measured value 50 can be added to the previously used model of the bending operation and at - For example, after a new calculation of the nominal forming characteristic 46 for subsequent bending operations into account and the model 13 improved and adapted.

All information on ranges of values in the description of the subject should be understood to include any and all sub-ranges thereof, e.g. the indication 1 to 10 should be understood to include all sub-ranges, starting from the lower limit 1 and the upper limit 10, i. all subregions begin with a lower limit of 1 or greater and end at an upper limit of 10 or less, e.g. 1 to 1.7, or 3.2 to 8.1 or 5.5 to 10.

The exemplary embodiments show possible embodiments of the method for determining a setting value of a bending press for a bending operation on an electrically conductive workpiece and a production device for bending conductive workpieces. It should be noted at this point that the invention is not limited to the specifically illustrated embodiments of the same, but also various combinations of the individual variants with each other are possible and this possibility of variation due to the doctrine of technical action by representational düng in the skill of skilled in the art. There are therefore also all possible embodiments, which are possible by combinations of individual details of the illustrated and described embodiment, the scope of protection.

For the sake of order, it should finally be pointed out that for better understanding, the measures of the method for determining a setting value of a bending press for a bending process on an electrically conductive workpiece or the components of a manufacturing device for bending of conductive workpieces simplified, sometimes uneven and / or enlarged and / or reduced in size.

The problem underlying the independent inventive solutions can be taken from the description.

Above all, the individual in Figs. 1; 2; 3; 4; FIGS. 5 and 6 form the subject of independent solutions according to the invention. The relevant objects and solutions according to the invention can be found in the detailed descriptions of these figures.

REFERENCE NUMBERS

1 workpiece

2 sheet metal plate

3 thickness

4 thickness gauge

5 magnetic field measuring device

6 exciter unit

7 sensor unit

8 control device

9 Control 10 related

11 bending angle

12 stamps

13 die 14 V die

15 Forming away

16 touch point

17 dead center 18 manufacturing facility

19 bending press

20 machine frame

21 Press beams 22 Press beams

23 adjusting device

24 displacement measuring device

25 positioning device 26 handling device

27 gripping device

28 deployment position

29 interface

30 holding device

31 vacuum suction

32 magnet

33 transmitting and receiving device

34 singling device

Claims

Patent claims

Anspruch [en] A method for determining a setting parameter value (14) of a bending press (2) in which a characteristic (7) of a workpiece (4) to be bent in a bending operation is fed by a control device (3) from at least one control device (3) at least one adjustment parameter value (14) of the bending press (2), in particular an immersion depth (15), of a target value (11) on the bent workpiece (6) on the basis of a model (13) of the bending process Stamper (23) of the bending press (2) or one of the punch (23) on the workpiece (4, 6) to be applied bending force or a deflection compensation parameter on the bending press (2) is set, wherein a characteristic (7) by the vortex current measurement before Completion of the bending process, by means of a sensor unit (22) as a measured value (9) determined, electromagnetic reaction of the workpiece (4) on one of an exciter unit (21) generated, the workpiece (4) alternating electromagnetic field is formed, characterized in that after partial or complete implementation of the bending process at a relief of the workpiece (6) an actual value (16) of the target size (11), in particular the bending angle (12), measured and with the Measured value (9) of the eddy current measurement and the pre-discharge acting setting parameter value (14) is linked.

2. The method according to claim 1, characterized in that the measurement of the actual value (16) of the target size (11) with an automatic measuring device on the bending press (2) is performed.

3. The method according to claim 1 or 2, characterized in that after partially carrying out the bending operation after the discharge of the workpiece (6) measured actual value

(16) is supplied to the target quantity (11) of the control device (3) and the setting parameter value (14) for the continuation of the bending operation is newly set by the control device (3).

4. The method according to any one of claims 1 to 3, characterized in that based on the measured after the discharge of the workpiece (6) actual value (16) of the target size (11) and the measured value (9) of the eddy current measurement and the immediately before the relief acting setting parameter value (14) the model (13) of the bending operation is adapted.

5. The method according to any one of claims 1 to 4, characterized in that the measured on the workpiece (6) actual value (16) of the target size (11), the measured value (9) of the eddy current measurement and the immediately before the discharge acting setting parameter value ( 14) are stored in the control device (3) in the form of a data record.

6. The method according to claim 5, characterized in that the model (13) of the bending process in the control device (3) is formed by a multiple data sets comprehensive value table or database.

7. The method according to claim 6, characterized in that the value table with numerical methods, in particular simulation calculation, finite element methods, regression calculation or interpolation calculation, comprises calculated data sets.

8. A method for determining a Einstellparameterwerts (14) of a bending press (2), in which by a control device (3) from at least one of the control device (3) supplied characteristic (7) to be bent in a bending operation workpiece (4) and one of Control value (10) for a target size (11) on the bent workpiece (6) based on a model (13) of the bending process at least one adjustment parameter value (14) of the bending press (2), in particular a penetration depth (15) of a punch ( 3) of the bending press (2) or a bending force to be applied by the punch (23) on the workpiece (6) or a deflection compensation parameter on the bending press (2), wherein a characteristic (7) by the in an eddy current measurement before termination of the Bending operation, by means of a sensor unit (22) as a measured value (9) determined, electromagnetic reaction of the workpiece (4) on one of an exciter unit (21) generated, the workpiece (4) an alternating electromagnetic field is formed, characterized in that from the measured value (9) of the eddy current measurement on the basis of a model (30) of the material properties an estimated value (29) of a parameter (7) of the workpiece (4) is derived and this from the control device (3) is used in setting the setting parameter value (14).

9. The method according to claim 8, characterized in that the estimated value (29) is linked to a nominal value (17) of the same parameter (7) of the workpiece (4), in particular from which a weighted average is formed, and as a parameter (7) for Setting the setting parameter value (14) is used.

10. The method according to claim 9, characterized in that two for the formation of a weighted average of the estimated value (29) of the characteristic (7) of the workpiece (4) and a nominal value (17) of the same characteristic (7) of the workpiece (4) , required weighting factors, which add up to 1, are selected from a range of values with a lower limit of 0 and an upper limit of 1.

11. A method for determining a setting parameter value of a bending press, in which a characteristic quantity of a workpiece to be bent in a bending process is delivered by a control device from at least one of the control device a desired value (19) for a target variable (11) on the bent workpiece (6) supplied to the control device (3) based on a model (13) of the bending process contained in the control device (3) at least one setting parameter value (14) of the bending press (2), in particular, an immersion depth (15) of a punch (23) of the bending press (2) or a bending force to be applied by the punch (23) to the workpiece (4, 6) or a deflection compensation parameter on the bending press (2) is determined, a characteristic variable (7 ) by the in an eddy current measurement before completion of the bending operation, by means of a sensor unit (22) as the measured value (9) determined, electromagnetic reaction of the workpiece (4) to one of Erre formed during the bending process, a curve (28) of the bending force or a directly related therewith Biegekraft- parameters depending on the immersion depth (B) of the (4) passing through the workpiece (4). 15) and supplied to the control device (3), the bending force, the bending force parameter or a calculated value (28) of a mechanical parameter (7) of the workpiece (4) selected from a group comprising yield strength, proportionality limit, elongation at break , Elongation, Young's modulus, is used as a parameter (7) to redetermine the setting parameter value (14) before the end of the bending process.

12. The method according to claim 11, characterized in that the calculation value of the mechanical parameter (7) determined from the profile (28) of the bending force or the bending force parameter is derived from a measured value (9) of the eddy current measurement using a model (30) of the material properties Estimate (29) of the same mechanical characteristic (7) of the workpiece (4) is linked, in particular from a weighted average is formed and used as a corrected characteristic (7d) for reestablishing the setting parameter value (14) before completion of the bending operation.

13. The method according to claim 12, characterized in that two for the formation of a weighted mean value from the calculated value of the mechanical characteristic variable (7) and from the measured value (7) determined from the curve (28) of the bending force or the bending force parameter 9) of the mechanical characteristic quantity (7) derived from the vortex current measurement, required weighting factors which result in a sum of 1, are selected from a value range with a lower limit of 0 and an upper limit of 1.

14. The method according to any one of claims 11 to 13, characterized in that the curve (28) of the bending force or the bending force parameter or from the course (28) calculated value of the mechanical characteristic (7) with the measured value (9) of the eddy current measurement linked and enters the model (30) of the workpiece properties and adapts this.

15. The method according to any one of claims 11 to 14, characterized in that the curve (28) of the bending force or the bending force parameter or from the curve (28) of the bending force calculated value of the mechanical characteristic (7) and the same workpiece (4) the measured value (9) of the vortex current measurement is stored in the control device (3) in the form of a data set, in particular a value table or database containing data sets of other workpieces (4) forming the model (13) of the bending process.

16. The method according to any one of claims 1 to 15, characterized in that at least one characteristic (7) of the workpiece (4) selected from a group comprising workpiece thickness, weight or workpiece surface determined by a measurement before or during the bending process and the control device (3 ) and used in setting the setting parameter value (14).

17. The method according to any one of claims 1 to 16, characterized in that the eddy current measurement is largely limited to zones in the workpiece (4), which are deformed during the bending process.

18. The method according to any one of claims 1 to 17, characterized in that the eddy current measurement is performed with at least two different, in particular at least ten different excitation frequencies of the electromagnetic alternating field.

19. The method according to any one of claims 1 to 18, characterized in that as a target size (11) obtained after the bending process geometric actual size on the workpiece (6) selected from a group comprising bending angle (12), leg length, radius of curvature at the bending zone , Parallelism or crowning of the workpiece (6) is used.

20. Method according to claim 1, characterized in that a relationship contained in the model (13) of the bending process between measured values (9) of a plurality of eddy current measurements and actual values (16) of the target variable (11) on the workpieces (6 ) is produced by means of regression calculation and / or correlation calculation from measured values (9) of previous eddy current measurements on a plurality of workpieces (4, 6) and actual values (16) of the target variable (11) measured on the respective workpiece (6).

21. The method according to any one of claims 1 to 20, characterized in that in the model (13) of the bending process contained relationship between measured values (9) of the eddy current measurements and actual values (16) of the target size (11) on the workpieces (6) with the help a neural network is produced from results of a series of multiple bending operations.

22. Method according to claim 21, characterized in that a relationship contained in the model (13) of the bending process is produced by using a back-propagation process from results of a sequence of several bending operations.

23. The method according to any one of claims 1 to 22, characterized in that the measured value (9) of the eddy current measurement or derived therefrom value of a characteristic (7) of the workpiece (4) on the workpiece (4), in particular in machine-readable form is attached ,

24. The method according to any one of claims 1 to 23, characterized in that the Bending process is performed as a free-bending process on a bending press (2) in the form of a press brake.

25 manufacturing device (1) for bending a workpiece (4, 6), in particular with a method according to one of claims 1 to 25, comprising a bending press (2) with two relatively adjustable, with bending tools (5) provided with pressing bars ( 32, 33) and an electronic control device (3), characterized in that the control device (3) is communicatively connected to an eddy-current measuring device (8) for the workpiece (4) to be bent and an interface (40) for receiving a measured value (9) the eddy current measuring device (8) or a derived value of the characteristic

(7) of the workpiece (4).

26. Production device (1) according to claim 25, characterized in that the eddy-current measuring device (8) is arranged on the bending press (2).

27. Production device (1) according to claim 25 or 26, characterized in that the eddy current measuring device (8) an exciter unit (21) for generating an on the workpiece (4) acting electromagnetic alternating field and a sensor unit (22) for detecting the by the workpiece (4) caused retroactivity on the electromagnetic alternating field.

28. Production device (1) according to claim 27, characterized in that the sensor unit (22) comprises a sensor coil.

29. Production device (1) according to claim 27 or 28, characterized in that the sensor unit (22) comprises a Hall sensor.

30. Manufacturing device (1) according to one of claims 27 to 29, characterized in that the exciter unit (21) and the sensor unit (22) with a movable suspension, in particular with a gimbal on the eddy current measuring device

(8) are stored.

31 manufacturing device (1) according to claim 30, characterized in that the suspension consists essentially of non-magnetic material.

32. Manufacturing device (1) according to any one of claims 27 to 31, characterized in that the excitation unit (21) and the sensor unit (22) resiliently resiliently mounted on the eddy current measuring device (8) are mounted.

33. Manufacturing device (1) according to one of claims 25 to 32, characterized in that the eddy-current measuring device (8) in the region of the machine frame (31), the fixed beam (32), a positioning device (36) or a depositing station for workpieces (4 , 6) is arranged.

34. Manufacturing device (1) according to one of claims 25 to 33, characterized in that the bending press (2) comprises a force measuring device for measuring the bending tools (5) on the workpiece (4, 6) applied bending force and the force measuring device with the Control device (3) is communicatively connected.

35. Manufacturing device (1) according to claim 34, characterized in that the force measuring device comprises force sensors for direct measurement of the bending force or sensors for the indirect measurement of the bending force in a fluidic or electric pressing beam drive (34).

36. Manufacturing device (1) according to one of claims 25 to 35, characterized in that the manufacturing device (1), in particular the bending tool (5) of the bending press (2) connected to the control device (3) angle measuring device for measuring the bending angle (12 ) on the bent workpiece (6).

37. Manufacturing device (1) according to one of claims 25 to 36, characterized in that in the region of the bending press (2) with a gripping device (38) provided handling device (37) for handling the workpieces (4, 6) is arranged.

38. Manufacturing device (1) according to claim 37, characterized in that the eddy current measuring device (8) in the working space of the handling device (37) is arranged.

39. Manufacturing device (1) according to claim 37 or 38, characterized in that the eddy-current measuring device (8) on the handling device (37), in particular in the region of the gripping device (38) is arranged.

40. Manufacturing device (1) according to one of claims 25 to 39, characterized in that the eddy-current measuring device (8) comprises a holding device (41) for a workpiece (4).

41. Manufacturing device (1) according to any one of claims 25 to 40 characterized gekennzeich- net that the manufacturing device (1), in particular the eddy current measuring device (8) comprises a Dickeninesseinrichtung (20).

42. Manufacturing device (1) according to one of claims 25 to 41, characterized in that the eddy-current measuring device (8) is coupled to a separating device (45) for the workpieces (4) to be bent.