Method and measuring system for determining surface loads, deformations on forming machines and / or the quality of a formed workpiece

Abstract

Methods for determining surface loads, deformations on forming machines and / or the quality of a formed workpiece, in which with at least one forming tool (1) which is force-fitted to a force transmission element (3) of a forming machine or to a table of a forming machine, a mechanical forming force is applied to a workpiece to be processed during a forming process, which causes a surface load and / or a deformation on at least one contact surface (5) between the at least one forming tool (1) and the force transmission element (3) or between the at least one forming tool (1) and the table, and with at least one sensor (4) designed to detect a physical quantity and attached in or on the tool clamping element (2) at a defined position, detects at least one physical quantity in or on the tool clamping element (2) and transmits measurement data of the at least one physical quantity to an electronic evaluation device, and in the electronic evaluation device the surface load on the at least one contact surface (5) and / or the deformation of the at least one contact surface (5) is determined depending on the respective position and the measurement data of the at least one sensor (4) and / or the quality of a workpiece formed in the process is determined; wherein the surface load and / or deformation of the contact surface (5) is / are determined with an evaluation model with which the measurement data of the at least one sensor (4) for a known position of the at least one sensor (4) in or on the tool clamping element (2) is mathematically mapped to the surface load and / or deformation of the contact surface (5) or the quality is determined by the course of at least one recorded physical quantity as a function of time or of the distance traveled during the forming process of at least one forming tool (1).

Description

[0001] The present invention relates to a method and a measuring system for determining surface loads, deformations on forming machines, and / or the quality of a formed workpiece. Forming machines can preferably be designed for deep drawing, cutting, bending, embossing, and forging.

[0002] In forming machines, a forming force or torque is applied to the workpiece using a forming tool. The components of the forming machine involved in the force transmission undergo elastic deformation due to this mechanical load. This deformation can lead to undesirable effects, such as positional or shape deviations of the components, which in turn can negatively impact the forming process. Therefore, a common goal is to reduce or compensate for the deformations occurring during the forming process. To achieve this, however, the shape deviations occurring on the forming machine must be sufficiently known.

[0003] Currently, surface loads and deformations in forming machines during the forming process can only be determined by compromising machine properties or with very high equipment costs. Measurement can be achieved, for example, using integrated measuring plates clamped between the machining tool and the contact surface of a force transmission element or a table in the forming machine. These measuring plates are equipped, for example, with strain sensors that directly measure the reaction forces at the contact surface with a defined spatial resolution. However, such measuring systems with integrated measuring plates significantly influence the stiffness behavior of the forming machine, which can also negatively affect the forming process.

[0004] Another option is to equip the forming tool with sensors. This allows contact forces between the tool surface and the workpiece to be measured directly in specific areas. While this enables high accuracy, the setup effort is very high, as each tool must be individually equipped with sensors. Furthermore, each tool must be calibrated within the overall forming machine system, making tool changes very time-consuming.

[0005] R. Kurth et al. in “Forming 4.0 Smart machine components applied as a hybrid plain bearing and a tool clamping system”; Procedia Manufacturing, Vol. 27, 2019, pp. 65-71, refer to possibilities for the use of sensors in conjunction with a tool clamping system.

[0006] DE 39 02 918 C1 discloses a clamping device for securing tools.

[0007] Under the name Unidor, TR-Electronic GmbH Campus Trossinger, 2016, p. 1-12 company publication, URL: https: / / www.unidor.info / assets / unidor-messquader_ihp_web.pdf has offered a tool clamping device for process control with sensor technology.

[0008] The present invention is therefore based on the objective of overcoming the disadvantages of the prior art. This objective is achieved according to the invention by the method of claim 1 and a measuring system according to claim 15. Advantageous embodiments and further developments are described in the dependent claims.

[0009] In a method for determining surface loads, deformations on forming machines, and / or the quality of a formed workpiece, a mechanical forming force is applied to a workpiece during a forming process using at least one forming tool, which is positively locked to a force transmission element or to a table of a forming machine by means of at least one tool clamping element. This forming force causes a surface load and a deformation at at least one contact surface between the at least one forming tool and the force transmission element, and between the at least one forming tool and the table. That is, the contact surface between the at least one forming tool and the force transmission element, or between the at least one forming tool and the table, is a surface located within the force path of the forming force.During the forming process, a measuring system, comprising at least one sensor designed to detect at least one physical quantity and attached to or within the tool clamping element at a defined position, detects at least one physical quantity at the respective position and transmits the measurement data of this at least one physical quantity to an electronic evaluation unit of the measuring system. Depending on the respective position of the at least one sensor and the measurement data from the at least one sensor, the electronic evaluation unit determines the surface load and / or the deformation of the contact surface.

[0010] In addition to or solely for determining the surface load and / or deformation of the contact surface, information about the quality of the workpiece being machined and / or information about the forming process on the workpiece, such as the process quality of the forming process itself, can also be derived from the measurement data. This information can be determined dependently or independently of the respective surface load(s) and / or deformation(s) of the contact surface. In the simplest case, a pass / fail assessment can be made.

[0011] When determining quality, the progression of at least one measured physical quantity is considered, for example, as a function of time or the distance traveled by at least one forming tool during the forming process. For instance, a deviation from a continuous measurement curve indicates that the workpiece has likely not achieved, or will not achieve, the desired quality. The rate of change of the respective physical quantity can be determined. If this rate changes during the forming process, this change can be taken into account for quality assessment. The specific time or distance traveled during the feed movement of a forming tool up to this change in rate can also be considered. The magnitude of this rate of change can also serve as a criterion for the achieved or achievable quality.This can be too small or too large in relation to a given increase in the measured quantity at which a certain predetermined quality can be maintained.

[0012] The method can thus be used to monitor process forces and / or elastic deformations at the interface between machine and tool, as well as to detect changes in these quantities during operation of the forming machine, i.e., during the forming process. This leads to a significant increase in the transparency of the processes and machine responses. The method offers the advantage that the determination of surface loads and deformations is carried out within a machine-integrated system. By integrating or arranging at least one sensor in or on at least one tool clamping element, no additional installations or time-consuming modifications are necessary for measurements during machine operation. Therefore, measurements of real loads during machine operation can be performed without significant setup costs or impairment of machine properties, such as stiffness.

[0013] The sensor (at least one) can remain in or on the tool clamping element even during tool changes, allowing the determination of surface loads and / or deformations to be carried out independently of the tool type. This measurement method can therefore be used particularly when introducing new tools, during production start-up, and for root cause analysis of events occurring during the operation of forming machines, in order to provide information about the components involved.

[0014] This method can be used in particular to determine surface loads and / or deformations on forming machines for sheet metal processing or bulk metal forming, for example, for deep drawing, bending, embossing, cutting, forging, or press hardening. The forming machine can be, for example, a mechanical, electromechanical, hydraulic, or pneumatic press with a ram as the force transmission element.

[0015] The forming tool can consist of an upper and / or lower tool. This means the process can be carried out with at least one tool clamping element in or on at least one upper tool and / or at least one tool clamping element in or on at least one lower tool, with the use on the upper tool being advantageous. The tool clamping element can be a mechanical, electromechanical, hydraulic, or pneumatic clamping element, in particular a spring clamping element, an insert clamping element, a wedge clamping element, an angle clamping element, a pull clamping element, a screw, or a clamping jaw, whereby the clamping process can be carried out manually or, preferably, automatically. It can also be moved manually, but preferably automatically, to the clamping position.

[0016] The physical quantity detected by the sensor can be a physical quantity or parameter suitable for determining or obtaining a surface load on the contact surface, an elastic deformation of the contact surface, information about the quality of the workpiece being processed during the forming process, and / or information about the forming process itself. Preferably, the physical quantity can be a geometric and / or mechanical and / or electromagnetic quantity, such as a distance, an angle, a pressure, a compressive force, a tensile force, a strain, a deflection, a magnetic field, and / or a change in such a quantity. The sensor can be configured to detect the physical quantity using an optical, piezoelectric, capacitive, resistance-based, or electromagnetic measurement method.In this method, a sensor can be, in particular, a piezoresistive pressure sensor, at least one strain gauge, a piezoelectric pressure sensor, a capacitive pressure sensor, an inductive pressure sensor, an eddy current sensor, a displacement probe, an accelerometer or a Hall sensor.

[0017] The contact surface between the at least one forming tool and the force transmission element, or between the at least one forming tool and the table, is a surface located within the force path of the forming force. In particular, the contact surface can be a surface whose surface normal is parallel to the force path or parallel to the direction of the forming force. The at least one sensor can be located in or on the at least one tool clamping element at a position located within the force path of the forming force. Preferably, however, it can also be located at a position outside the force path of the forming force, thus preventing potential damage to the at least one sensor caused by high forming forces.Particularly preferably, the sensor can be arranged and / or oriented in or on the at least one tool clamping element at a position such that, under different load distributions on the force transmission element or different basic load cases in the forming machine, the at least one sensor detects a sufficiently variable physical quantity depending on the load case, which can provide a measurement signal that can be evaluated for a reliable determination of the respective physical quantity. These positions can be determined, for example, experimentally or with a finite element simulation.

[0018] It can be provided that the at least one sensor is configured to detect the respective physical quantity, such as pressures, strains, compressive and / or tensile forces, in three independent spatial directions in or on the tool clamping element. This can also be achieved with multiple sensors. Preferably, several sensors can be arranged in or on the tool element such that a deformation force acting on the tool clamping element can be determined from the sensor measurement data, taking into account their positions and / or orientation in or on the tool clamping element. For determining the surface load and / or deformation, the deformation forces of one or more tool clamping elements can be considered individually or in correlation with each other; that is, the surface load and / or deformation of the contact surface can also be determined as a function of these deformation forces.

[0019] In clamping elements with a structural component in the form of a tension anchor, for example, several strain gauges can be arranged around the circumference of the tension anchor's outer surface in the direction of a clamping force and measure deformation in the direction of the tension. From the measured values, positions, and orientations of the sensors, a deformation force acting on the tension anchor during a forming process can be determined, and with this, in turn, a surface load and / or deformation of the contact surface can be calculated. In a slide-in clamp, for example, at least one sensor can be arranged in or on an end face of a clamping jaw and / or at least one sensor in the area of ​​a groove on the clamping jaw's bearing surface against the tool.

[0020] In this method, the surface load and / or the deformation of the contact surface are preferably determined using an evaluation model that mathematically maps the measurement data from the at least one sensor, for a known position of the at least one sensor in or on the tool clamping element, to a surface load and / or deformation of the contact surface. The forces acting locally on the contact surface and / or the elastic deformations of the contact surface can be evaluated in terms of their magnitude and direction of action depending on the time course of the measurement data and / or also depending on their individual values, for example, minima or maxima. Depending on the evaluation model, further machine parameters can also be taken into account.The surface load and / or deformation of the contact surface can be determined, for example, depending on the position and measurement data of the at least one sensor, the position of the force transmission element, and / or the acceleration of the force transmission element. Preferably, the surface load and / or deformation can also be determined depending on a calibration or calibration function for the at least one sensor and / or the at least one tool clamping element, so that when the at least one sensor and / or the at least one tool clamping element is replaced, no new model creation is necessary, but only the respective calibration function in the evaluation model needs to be adjusted.

[0021] In this process, the evaluation model can advantageously be created before the workpiece is processed. With such a pre-created or pre-trained evaluation model, the sensor's measurement data can be evaluated with minimal delay during the forming process, enabling the determination of surface loads and / or deformations in real time.

[0022] The electronic evaluation unit can typically be configured to store the evaluation model, optimize it if necessary, and calculate a surface load and / or deformation of the contact surface according to the evaluation model. The electronic evaluation unit can also be configured to perform preprocessing, such as filtering, conversion, or error correction, and / or correlation of the measurement data and other parameters of the evaluation model, either decentrally at individual sensors or tool clamping elements, or centrally within the electronic evaluation unit itself.

[0023] The modeling, i.e., the creation of the evaluation model, can be carried out mathematically, empirically, or physically. For example, an evaluation model might be created using a finite element simulation of the surface loads and / or deformations in the forming machine, as well as the local pressures, strains, compressive and / or tensile forces within the tool clamping element. Alternatively, an evaluation model could be created based on calibration measurements performed in the forming machine with defined surface loads and / or deformations at the contact surface.

[0024] In such calibration measurements, defined surface loads and / or deformations can be applied to the contact surface using a flat measuring plate, at least one loading device, and / or at least one deformation measuring device designed to detect deformations on the measuring plate or the table. The measuring plate can, for example, replicate a forming tool body. It can be clamped to the force transmission element by friction using at least one tool clamping element instead of an upper tool, and the at least one loading device can be attached to the table at a defined position by positive and / or frictional locking. Alternatively, the measuring plate can be clamped to the table at least once by friction using at least one tool clamping element instead of a lower tool, and the at least one loading device can be arranged on the measuring plate at a defined position by positive and / or frictional locking.

[0025] During calibration, the sensor signals of at least one sensor in a forming process can correlate with the component properties resulting from the forming process on the respective workpiece (e.g., quality-determining component properties) and thus enable, for example, a good / bad comparison and / or an envelope curve evaluation.

[0026] A loading device can be active or passive and may be, for example, a ram, a gas spring, or a hydraulic cushion. However, devices or tools designed to introduce a known force or surface load into the table and / or the measuring plate can also be used as loading devices in the process. The loading device can be configured to detect the pressure or compressive force acting between the loading device and the measuring plate and / or the table. These pressure or compressive force measurements can be used to calibrate the forming process, for example, the forming force of the forming machine. Furthermore, an evaluation model can be determined based on the pressure or compressive force measurements; that is, the surface load and / or deformation at the contact surface can be determined based on the pressure or compressive force measurements at the loading device.

[0027] By moving the force transmission element along the direction of the forming force, the measuring plate and the at least one loading device, or the force transmission element and the at least one loading device, can be brought into contact with each other, thus applying pressure or a compressive force to the measuring plate and / or the table at a defined position. Depending on the respective position of the force transmission element and the respective position of the at least one loading device, the physical quantity, for example, local pressures, strains, compressive and / or tensile forces, in or on the at least one tool clamping element can now be detected with the at least one sensor, and / or the local deformations on the measuring plate and / or the table and / or the force transmission element can be detected with the at least one deformation measuring device.The measured surface loads and / or deformations can then be used to determine the respective surface loads and / or deformations at the contact surface. The deformations at the measuring plate and / or the table can be determined, for example, using optical or tactile measuring methods.

[0028] The surface loads and / or resulting deformations acting on the contact surface can be varied depending on the position of the force transmission element and the position and number of loading devices. This allows for the generation of various basic load cases at the contact surface between the tool and the machine. Machine deformations in real production processes can be derived from the superposition of these cases. From the surface loads and / or deformations and the associated measurement data from one or more sensors, a set of calibration measurement data is obtained for the respective position of each sensor in or on the tool clamping element. This data can then be used, for example, to create an evaluation model using regression analysis. One or more sets of calibration measurement data can also serve as training data for a supervised learning process. This supervised learning process can involve training an artificial neural network.The trained artificial neural network can also form an evaluation model.

[0029] The spatial resolution with which the surface load and / or deformation can be determined depends on both the number and respective position of the sensors and tool clamping elements, as well as on the evaluation model. It may be provided that at least one sensor for detecting at least one physical quantity is arranged on each of the tool clamping elements in the forming machine, where the forming tool is clamped to the force transmission element or table of the forming machine. It is also advantageous to perform the calibration measurements for model building with a deformation measuring device designed to detect the deformations on the clamping surfaces of the table and / or force transmission element, for example, a press ram, due to the load.

[0030] A measuring system for determining deformations on forming machines comprises at least one sensor and an evaluation unit. The at least one sensor is attached, or can be attached, at a defined position in or on at least one tool clamping element of the forming machine. At least one forming tool is frictionally attached to a force transmission element of the forming machine or to a table of the forming machine by means of the at least one tool clamping element, such that a forming force can be applied to a workpiece during a forming process using the at least one forming tool. This force causes a surface load and / or deformation of a contact surface between the at least one forming tool and the force transmission element or between the at least one forming tool and the table of the forming machine.

[0031] The at least one sensor is also configured to detect at least one physical quantity, in particular local pressures, compressive forces, tensile forces, deformations, strains, and / or changes in these quantities, at the respective position in or on the at least one tool clamping element and to transmit this data as measurement data to the electronic evaluation unit of the measuring system. Depending on the position and measurement data of the at least one sensor, the electronic evaluation unit is configured to determine the surface load on the contact surface and / or deformation of the contact surface. Information about the quality of the workpiece being machined and / or information about the forming process can also be obtained and taken into account.

[0032] The described measuring system is particularly suitable for carrying out the described procedure, that is, the described procedure can be carried out with the described measuring system.

[0033] Exemplary embodiments of the invention are shown in the drawings and are described below with reference to the Fig. 1 to 3 explained.

[0034] They show: Fig. 1: In a schematic side sectional view, an example of a measuring system for determining surface loads and / or deformations on forming machines, Fig. 2: in a schematic flowchart an example of the implementation of the procedure for determining surface loads and / or deformations on forming machines, and Fig. 3: an example of surface loads that can occur in a method for determining surface loads and / or deformations on forming machines.

[0035] In Fig. Figure 1 shows a schematic side sectional view of an example of a measuring system for determining surface loads and / or deformations on forming machines. The described measuring system is used to carry out the procedure for determining surface loads and / or deformations on forming machines, such as in Fig. The measuring system, as shown in Figure 2, is suitable. It comprises at least one sensor 4 and an electronic evaluation unit (not shown). The at least one sensor 4 is arranged at a defined position in or on at least one tool clamping element 2, wherein a forming tool 1 is positively and / or non-positively attached to a force transmission element 3 or a table of the forming machine by means of the at least one tool clamping element 2, such that a mechanical forming force can be applied to a workpiece to be processed in the forming machine during a forming process. This force can cause a surface load and deformation at at least one contact surface 5 between the forming tool 1 and the force transmission element 3 and / or between the forming tool 1 and the table. The workpiece to be processed can typically be clamped between the force transmission element 3 and the table in the forming machine.

[0036] The at least one sensor 4 is configured to detect at least one physical quantity at the respective position in or on the at least one tool clamping element 2 and to transmit measurement data of the at least one physical quantity to the electronic evaluation unit of the measuring system. Depending on the respective position and the measurement data of the at least one sensor 4, the electronic evaluation unit is configured to determine a surface load and / or a deformation of the at least one contact surface 5 between the forming tool 1 and the force transmission element 3 or between the forming tool 1 and the table.The evaluation device can also be designed to determine information about the quality of the workpiece to be processed and / or information about the forming process on the workpiece to be processed, such as the process quality of the forming process, whereby this information can also be determined depending on the surface load and / or the deformation of the contact surface 5.

[0037] In the example shown, the Fig. 1. The force transmission element 3 is a ram of a forming machine for sheet metal processing or bulk metal forming, for example, a mechanical, electromechanical, hydraulic, or pneumatic press. The tool clamping element 2 can be a mechanical, electromechanical, hydraulic, or pneumatic clamping element. The forming tool can be an upper or lower tool. That is, the process can be carried out with at least one tool clamping element in or on at least one upper tool and / or at least one tool clamping element in or on at least one lower tool, with the use on the upper tool being advantageous.

[0038] The contact surface 5 can be arranged in the force flow of the forming force such that the surface normal of the contact surface 5, as in the example of the Fig. As shown in Figure 1, the sensor 4 is aligned parallel to the direction of the forming force. The at least one sensor 4 can preferably be positioned in or on the at least one tool clamping element 2 such that it detects a sufficiently variable physical quantity under different load distributions on the force transmission element 3 or under different basic load cases. The sensor 4 can be configured to detect the physical quantity, for example, a distance, an angle, a pressure, a compressive force, a tensile force, a strain, a deflection, and / or a change in these quantities, using an optical, piezoelectric, capacitive, resistance-based, or electromagnetic measuring method.Sensor 4 can in particular be a piezoresistive pressure sensor, at least one strain gauge, a piezoelectric pressure sensor, a capacitive pressure sensor, an inductive pressure sensor, an eddy current sensor, a displacement probe, an accelerometer or a Hall sensor.

[0039] In a tension clamp as a tool clamping element 2, for example, six strain gauges can be arranged as sensors 4 on the circumference of the tension clamp's outer surface in the direction of a tensile stress on the tension clamp to measure deformation in the direction of the tensile stress. From the measurement data, positions, and orientations of the strain gauges, a deformation force acting on the tension clamp during a forming process can be determined, and with this, in turn, a surface load and / or deformation of the contact surface 5 can be determined. In a slide-in clamp as a tool clamping element 2, at least one sensor 4 can be arranged in or on an end face of a clamping jaw and / or a groove on the clamping jaw's bearing surface for the forming tool. The one or more sensors 4 can be configured, for example, to measure the physical quantity, e.g.To detect pressures, compressive and / or tensile forces and / or deformations in three independent spatial directions.

[0040] In Fig. Figure 2 shows a schematic flowchart illustrating an example of the procedure for determining surface loads and / or deformations on forming machines. Before procedure part B for determining surface loads and / or deformations is executed, both a calibration K of the at least one tool clamping element 2 and a calibration A of the entire system of forming machine and sensor 4 can be performed to create an evaluation model or a substitute model for the respective determination of surface loads and / or deformations. Procedure part B for determining surface loads and / or deformations allows surface loads and / or deformations to be recorded on a contact surface 5 between the forming tool 1 and the force transmission element 3 or between the forming tool 1 and the table during a real production process.In the process, at least one forming tool 1, which is force-fitted to at least one tool clamping element 2, is used. Fig. 2, referred to as a clamping element, is attached to a force transmission element 3 of a forming machine or to a table of a forming machine, and a mechanical forming force is applied to a workpiece.

[0041] The sensor information is acquired during this forming process using at least one sensor 4, which is designed to detect at least one physical quantity and is attached to or within the tool clamping element 2 at a defined position. The physical quantity can be a physical quantity or characteristic value suitable for determining an area load on the contact surface 5, an elastic deformation of the contact surface 5, information about the quality of the workpiece being machined during the forming process, and / or information about the forming process itself. The at least one sensor 4 detects the at least one physical quantity at the respective position in or within the tool clamping element 2. The measurement data (sensor information) of the at least one physical quantity thus detected are transmitted to an electronic evaluation unit, where an area load, i.e.,a force distribution, and / or a deformation of the contact surface 5 between the at least one forming tool 1 and the force transmission element 3 or between the at least one forming tool 1 and the table of the forming machine can be determined depending on the position and the measurement data.

[0042] The evaluation model or replacement model was used in the example of the Fig. 2. Before determining the surface load and / or based on calibration measurements A, which are recorded at defined surface loads and / or deformations on the contact surface 5, a clamping system was applied in the forming machine and deformed with defined surface loads and / or deformations, i.e., basic load cases were reproducibly generated on the contact surface 5. For these basic load cases, a physical quantity was recorded at a defined position in or on the tool clamping element 2 using at least one sensor 4, and an evaluation model was created based on this calibration measurement data. This evaluation model mathematically maps the measurement data of the at least one physical quantity for a known position of the at least one sensor 4 in or on the tool clamping element 2 to a surface load and / or deformation of the contact surface.The evaluation model can be created based on purely mathematical functional relationships, empirical findings, or physical principles. Alternatively or additionally, the evaluation model or substitute model can also be created using finite element simulations of the physical quantity as well as surface loads and / or deformations in the forming machine.

[0043] The calibration measurements can be performed, in particular, with a flat measuring plate, at least one loading device, and at least one deformation measuring device designed to detect deformations on the measuring plate and / or the table and / or the force transmission element. The measuring plate can be attached to the force transmission element in place of the forming tool, and the loading device can be mounted at a defined position on the table of the forming machine. Subsequently, by translationally moving the force transmission element 3 along the direction of the forming force, the measuring plate and the at least one loading device can be brought into contact with each other. At the position of the loading device, pressure or a compressive force is applied to the measuring plate and the table and / or the force transmission element, thus generating a basic load case for the calibration measurement at the contact surface 5.

[0044] For this basic load case, depending on the position of the force transmission element 3 and the position of the at least one loading device with the at least one sensor 4, the pressure, compressive force, tensile force, and / or deformation in or on the tool clamping element 2, and the deformations on the measuring plate and / or the table, can be recorded using the deformation measuring device. The surface loads and / or deformations of the basic load case can be determined from the deformations recorded on the measuring plate and / or the table by the deformation measuring device. Thus, calibration measurement data sets for different basic load cases can be generated for various positions and numbers of loading devices, and the machine deformations in real production processes can be derived from the superposition of these data sets.

[0045] An evaluation model can be created from the calibration measurement data sets, for example, through regression analysis and / or supervised learning with an artificial neural network. Depending on the evaluation model, the surface load and / or deformation of the contact surface 5 can also be determined based on further parameters or additional external information. For example, it may be possible to determine the surface load and / or deformation based on the position and measurement data of at least one sensor 4, the position of the force transmission element 3, and / or the acceleration of the force transmission element 3.

[0046] If several sensors 4 are used in or on one or more tool clamping elements 2, it may also be possible to determine deformation forces acting on the tool clamping element 2 due to the forming force from the measurement data of the sensors 4 and to determine the surface load and / or deformation of the contact surface 5 in the evaluation model from the deformation forces of individual tool clamping elements 2 or several tool clamping elements 2 in correlation to each other. Preferably, the surface load and / or deformation can also be determined as a function of known calibration functions for the at least one sensor 4 or the at least one tool clamping element 2, as in the example of Fig. 2 shown, can be determined so that when replacing at least one sensor 4 or at least one tool clamping element 2, no new model creation is necessary, but only the respective calibration function in the evaluation model can be adjusted.

[0047] In Fig. Figure 3 represents surface loads or a basic load case that can occur in a method for determining surface loads and / or deformations on forming machines. The surface loads were applied using a press with four punches, which were used as a loading device (the punch surfaces are shown in Figure 3). Fig. 3 indicated by circular areas with dashed lines), onto a measuring plate (XY plane in Fig. 3) applied. For this purpose, the measuring plate was clamped to the ram 3 of the press using clamping elements 2 instead of a forming tool 1 and pressed against the loading device with the nominal pressing force of the forming machine. The resulting deformations on the measuring plate (measuring points are in Fig. 3 marked with black dots) are recorded and the deflection of the measuring plate and thus the deformation at the contact surface 5 between the forming tool and the ram are determined from this measurement data.

[0048] Only features of the various embodiments disclosed in the exemplary embodiments can be combined with one another and claimed individually, independently of the respective example shown.

Claims

[1] Method for determining surface loads, deformations on forming machines and / or the quality of a formed workpiece, in which with at least one forming tool (1) which is force-fitted to a force transmission element (3) of a forming machine or to a table of a forming machine, a mechanical forming force is applied to a workpiece to be processed during a forming process, which causes a surface load and / or a deformation on at least one contact surface (5) between the at least one forming tool (1) and the force transmission element (3) or between the at least one forming tool (1) and the table, and with at least one sensor (4) designed to detect a physical quantity and attached in or on the tool clamping element (2) at a defined position, detects at least one physical quantity in or on the tool clamping element (2) and transmits measurement data of the at least one physical quantity to an electronic evaluation device, and in the electronic evaluation device the surface load on the at least one contact surface (5) and / or the deformation of the at least one contact surface (5) is determined depending on the respective position and the measurement data of the at least one sensor (4) and / or the quality of a workpiece formed in the process is determined; wherein the surface load and / or deformation of the contact surface (5) is / are determined with an evaluation model with which the measurement data of the at least one sensor (4) for a known position of the at least one sensor (4) in or on the tool clamping element (2) is mathematically mapped to the surface load and / or deformation of the contact surface (5) or the quality is determined by the course of at least one recorded physical quantity as a function of time or of the distance traveled during the forming process of at least one forming tool (1). [2] Method according to claim 1, characterized by , that in the electronic evaluation unit information about the quality of the workpiece to be processed and / or information about the forming process is / are determined depending on the respective position and the measurement data of the at least one sensor (4). [3] Method according to any one of the preceding claims, characterized by, that a pressure, force, strain, deformation and / or an electromagnetic quantity is measured at the respective position as a physical quantity. [4] Method according to any one of the preceding claims, characterized by , that a mechanical, electro-mechanical, hydraulic or pneumatic press with one or more rams as a force transmission element (3) is used as a forming machine. [5] Method according to any one of the preceding claims, characterized by , that as tool clamping element (2) a mechanical, electromechanical, hydraulic or pneumatic clamping element, in particular a spring clamping element, a slide-in clamping element, a wedge clamping element, an angle clamping element, a pull clamping element or a clamping jaw is used, wherein the tool clamping element (2) is designed to apply the clamping force automatically or manually and to be movable manually or automatically to the clamping position. [6] Method according to any of the preceding claims characterized by , that the sensor (4) is a piezoresistive pressure sensor, at least one strain gauge, a piezoelectric pressure sensor, a capacitive pressure sensor, an inductive pressure sensor, an eddy current sensor, a displacement probe, an accelerometer, a fibre bragg sensor or a Hall sensor. [7] Method according to any of the preceding claims characterized by , that the at least one sensor (4) is arranged in or on the at least one tool clamping element (2) in a position that is not in the force flow of the forming force. [8] Method according to any one of the preceding claims, characterized by, that the surface load and / or deformation of the contact surface (5) and / or the information about the quality of the workpiece to be machined and / or the information about the forming process is / are determined depending on the position and the measurement data of the at least one sensor (4) and the position of the force transmission element (3). [9] Method according to any one of the preceding claims, characterized by , that the surface load on the contact surface (5) and / or the deformation of the contact surface (5) and / or the information about the quality of the workpiece to be processed and / or the information about the forming process are determined in the electronic evaluation unit with an evaluation model that is / was created before the forming force is applied to the respective workpiece to be processed. [10] Method according to claim 9 characterized bythat the evaluation model is created using a finite element simulation or analytical description of the physical quantity, the surface loads and / or deformations in the forming machine. [11] Method according to claim 9 characterized by , that the evaluation model is created by means of calibration measurements at defined surface loads and / or defined deformations at the respective contact surface (5). [12] Method according to claim 11 characterized by , that at least one physical quantity is determined at times when the existing surface load is known and / or has been determined metrologically and / or by simulation on at least one loading device with at least one sensor (4), and the deformations occurring on the force transmission element (3) and / or the table are measured and, if necessary, information about the quality of the workpiece to be machined and / or about the forming process is provided. [13] Method according to claim 11 characterized by , that surface loads and / or deformations are applied to the contact surface (5) by means of a preferably planar measuring plate replicating a forming tool base body, at least one loading device and at least one deformation measuring device designed to detect deformations on the measuring plate and / or the table, wherein the measuring plate has been clamped force-fit to the force transmission element (3) with the at least one tool clamping element (2) instead of an upper tool (1) and the at least one loading device has been attached to the table at a defined position, or the measuring plate has been clamped to the table in a force-fit manner with the at least one tool clamping element (2) instead of a lower tool (1) and the at least one loading device has been arranged on the measuring plate at a defined position, and by translational process of the force transmission element (3) along the direction of the forming force, the measuring plate and the at least one loading device or the force transmission element (3) and the at least one loading device are brought into contact with each other and a pressure or a compressive force is applied to the measuring plate and / or the table and / or the force transmission element (3) at the position of the respective loading device, and Depending on the position of the force transmission element (3) and the position of the at least one loading device with the at least one sensor (4), the physical quantity in or on the tool clamping element (2) and / or with the deformation measuring device, deformations on the measuring plate and / or the table and / or the force transmission element (3) are detected, and The surface loads and / or deformations at the contact surface (5) are determined from the deformations recorded by the deformation measuring device on the measuring plate and / or the table. [14] Method according to claim 9 or 11 to 13, characterized by that the evaluation model is created from the calibration measurement data using mathematical optimization, regression analysis and / or supervised learning with an artificial neural network. [15] Measuring system for determining surface loads and / or deformations on a forming machine and / or the quality of a formed workpiece, comprising at least one tool clamping element (2) with which at least one forming tool (1) is force-fitted to a force transmission element (3) of the forming machine or to a table of the forming machine in such a way that a forming force can be applied to a workpiece to be processed with the forming tool (1) in a forming process, which causes a surface load and / or deformation of a contact surface (5) between the at least one forming tool (1) and the force transmission element (3) and the at least one forming tool (1) and the table, comprising at least one sensor (4) and an electronic evaluation device, wherein the at least one sensor (4) is attached at a defined position in or on the at least one tool clamping element (2) of the forming machine, and the at least one sensor (4) is designed to detect a physical quantity at the respective position in or on the at least one tool clamping element (2) and to transmit it as measurement data to the electronic evaluation unit of the measuring system, and the electronic evaluation device is designed to determine, depending on the respective position and the measurement data of the at least one sensor (4), the surface load and / or deformation of at least one contact surface (5) between the forming tool (1) and the force transmission element (3) or between the forming tool (1) and the table, which is / are caused by a forming force applied to the workpiece to be machined by means of the force transmission element (3), wherein the surface load and / or deformation of the contact surface (5) is / are determined with an evaluation model with which the measurement data of the at least one sensor (4) for a known position of the at least one sensor (4) in or on the tool clamping element (2) are mathematically applied the surface load and / or deformation of the contact surface (5) can be represented or the quality can be determined by the course of at least one recorded physical quantity as a function of time or of the distance traveled during the forming process of at least one forming tool (1).

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