Method for determining a pressure distribution of a moulding tool device as well as reshaping apparatus and composite sheet metal component

Abstract

A method for determining a pressure distribution / pressure pattern of a moulding tool 1 for reshaping a sheet metal 2, the pressure distribution representing a load on the sheet metal 2 caused by the reshaping in the moulding tool. Piezoelectric material, preferably piezoelectric particles, is added into raw material of the sheet metal to create a composite sheet metal 4. The composite sheet metal is placed into the moulding tool and is reshaped. As load presses on the composite sheet metal, during reshaping, the piezoelectric particles produce voltage signals. A sensor 5 detects spatially resolvable voltage signals preferably by having upper 15 and lower 25 sensor units above and below the composite sheet metal. Preferably an algorithm calculates pressure from the detected voltages and maps where the pressure originated from in the composite metal sheet to determine pressure distribution. Preferably optimum pressure distribution maybe determined using the method and when a desired result is achieved a sheet metal component which may be an outer skin of a motor vehicle body may be introduced into the mould. Also a reshaping apparatus 10.

Description

The present invention relates to a method for determining a pressure distribution of a moulding tool device for reshaping a sheet metal component. The pressure distribution represents a load on the sheet metal component caused by the reshaping in the moulding tool device (so-called pressure pattern). The present invention also relates to a reshaping apparatus and a composite sheet metal component. Such pressure patterns are most commonly used as part of the testing process of a cutting and / or reshaping tool, e.g. for the production of complex body parts. In addition, pressure patterns are also used in order to monitor the serial process. In tool production, during the testing phase, sheet metal components are systematically pressed and analysed for different criteria (dimensional accuracy, burr, pressure pattern, etc.). The particularly relevant assessment criterion is usually the pressure pattern. For example, a pressure pattern is necessary in order to compensate for the production-related tolerances of a milling of the tool surface. In addition, this often regulates the sheet thinning. For a pressure pattern assessment, the sheet metal component is usually covered with blue marking ink prior to pressing. After the reshaping or the pressing stroke, it can now be examined at which points the tool had contact with the sheet metal. This is discernible via the colour distribution or brightness of the colour. The brighter the colour distribution, the harder the pressure band or contact between tool and sheet metal. In other words, the brighter the colour distribution, the higher is the spatial compressive load on the sheet metal component in the moulding tool. The actual assessment or evaluation of the pressure pattern is thus a subjective process, as it is estimated by human sensation what proportion of the relevant surfaces is OK. In light of the foregoing, the present invention seeks to provide an improved method for determining the pressure distribution. Preferably, it should be possible to assess the pressure distribution as objectively as possible. 19 08 24 A first aspect of the invention provides a method having the features of claim 1. A second aspect of the invention provides a reshaping apparatus which is the subject-matter of claim 9. Preferred further developments of the invention are the subject-matter of the subclaims. Additional advantages and features of embodiments of the present invention are disclosed in the general description and the description of the embodiment example. The method according to aspects of the invention is used in order to determine a pressure distribution of a moulding tool device. The moulding tool device is used in order to reshape a sheet metal component. The pressure distribution represents a load on the sheet metal component caused by the reshaping in the moulding tool device, in particular in a spatially resolved manner. The pressure distribution can also be referred to as a pressure pattern. The method comprises at least the following steps in this or another executable sequence: introducing a piezoelectric material into a raw material of the sheet metal component such that a composite sheet metal component is created, which provides an electrical voltage under mechanical loads (in particular a compressive load in the course of its reshaping); arranging the composite sheet metal component in the moulding tool device; reshaping the composite sheet metal component with the moulding tool device (in particular so that the composite sheet metal component receives the shape that is producible in accordance with the specification with the moulding tool); detecting spatially resolved electric voltage signals, which emanate from the composite sheet metal component during the reshaping, by means of at least one sensor device; determining the pressure distribution using the detected spatially resolved voltage signals. The method according to aspects of the invention offers many advantages. A significant advantage is provided by the composite sheet metal component with the piezoelectric material. A manual tinting can be omitted entirely. It is also particularly advantageous that the pressure distribution is determined based on the spatially resolved voltage signals. As a result, it can be evaluated particularly objectively and based on measurements whether the moulding tool device has undesirable imperfections. In addition, this pressure distribution provides a significantly greater information content than, for example, a pressure pattern obtained by marking. Thus, with aspects of the invention, it can be reliably determined where a certain 19 08 24 compressive load occurred during the reshaping or where and how many and how large imperfections are present in the moulding tool device. As a result, a targeted post-processing of the moulding tool can be carried out so that aspects of the invention can also be used for optimization of the moulding tool. At the same time, the sheet metal components produced therewith are significantly more precise and have fewer tolerances, so that the waste can also be reduced. In addition, with aspects of the invention, monitoring in serial production can be designed significantly simpler and more reliably. With aspects of the invention, the subjective (human) component can be supplemented or even replaced by objective measurement in the assessment of the moulding tool device. It is preferred that the voltage signals are registered as a function of time. In particular, a temporal progression of the compressive load (has occurred during the reshaping) can be determined. In particular, in addition to the spatial distribution, the pressure distribution determined also comprises a temporal distribution of the compressive load that occurs during the reshaping. Preferably, the pressure distribution also comprises a temporal progression of the compressive load. Such a design offers considerable advantages over the pressure pattern by means of a marking, in which only the end result is visible and the temporal progression of the loads remains invisible. With this embodiment of the invention, on the other hand, it can be precisely determined at what point in time a particular compressive load has occurred and where. The information content of the determined pressure distribution is thereby significantly expanded, such that, for example, post-processing of the moulding tool can be carried out in an even more targeted manner. Preferably, the introduction of the piezoelectric material into the raw material of the sheet metal component is carried out in that the material is cohesively embedded in the raw material of the sheet metal component. Preferably, the material is embedded in a near-surface region or in a surface layer of the sheet metal component. Particularly preferably, the introduction of the piezoelectric material into the raw material of the sheet metal component takes place at least by way of edge layer dispersion. Other suitable and comparable methods are also possible for introducing 19 08 24 the additional raw material, in particular, into an edge layer of the sheet metal component or even deeper. In one advantageous further development, the piezoelectric material comprises (piezoelectric) particles. Preferably, the particles embedded in the composite sheet metal component each provide at least one measurement point. In particular, at least one voltage signal proceeds from the measurement point (during the reshaping). In particular, the respective voltage signals of the measurement points are tapped at least partially individually (and / or spatially grouped) with the sensor device during the reshaping. In other words, the respective voltage signal of at least a part of the measurement points is individually detected. It is also possible that not every measurement point is tapped individually. The number of measured points depends, for example, on the concentration or surface density of the particles and / or desired resolution of the pressure distribution. In particular, the voltage signal of each measurement point is dependent on the level of the compressive load at the location of the measurement point. In particular, the number of measurement points is adjusted according to the desired resolution. In particular, the concentration of the particles is adjusted in order to achieve a desired resolution. The sensor device is in particular suitable and configured so as to detect the voltage signals individually and / or spatially grouped of at least a part of the measurement points. In particular, the sensor device comprises a plurality of sensor elements, which respectively detect at least the voltage signal of at least one measurement point. In particular, the number of sensor elements is aligned with the concentration of the particles and / or the number of measurement points. Preferably, the particles are smaller than 1 micrometre, and preferably smaller than 0.5 micrometres, and particularly preferably smaller than 200 nanometres. In particular, the particles are formed as nanoparticles. Then, preferably, the particles are smaller than 110 nanometres. In particular, the nanoparticles are between 1 nanometre and 100 nanometres in size. In an advantageous further development, the moulding tool device comprises at least 19 08 24 two (opposing) moulding tools. In particular, the composite sheet metal component faces the at least two moulding tools with at least one respective region. It is preferred that the voltage signals emanating from the at least two regions are detected in a spatially resolved manner. In particular, the regions comprise at least one upper side and at least one lower side. In particular, one moulding tool is a tool upper part and the other moulding tool is a tool lower part. In particular, the regions each have embedded piezoelectric material. In particular, at least one sensor unit is respectively associated with the moulding tools of the sensor device. In particular, the sensor device comprises at least two sensor units. In particular, the sensor units are each equipped with a plurality of sensor elements. The reshaping apparatus according to an aspect of the invention is used in particular for the method according to aspects of the invention. Preferably, the reshaping apparatus comprises at least one moulding tool device for reshaping a sheet metal component. In particular, the reshaping apparatus comprises at least one sensor device for the detection of spatially resolved electric voltage signals that emanate from a composite sheet metal component arranged in the moulding tool device during reshaping. In particular, the moulding tool device and the sensor device and the composite sheet metal component are at least partially configured as previously described. The reshaping apparatus according to an aspect of the invention is suitable and configured so as to carry out the method according to aspects of the invention described above. For this purpose, the features formulated in a method-like manner here can in particular be read as apparatus features. The composite sheet metal component according to an aspect of the invention is used in particular for the method described above. Preferably, the composite sheet metal component comprises at least one sheet metal component and at least one piezoelectric material incorporated into a raw material of the sheet metal component (preferably cohesively). In particular, the composite sheet metal component is suitable and configured so as to provide an electrical voltage under mechanical loads (in 19 08 24 particular a compressive load in the context of its reshaping in the moulding tool device). With the composite sheet metal component according to aspects of the invention, a moulding tool device can be particularly reliably and inexpensively adapted or monitored during the testing phase or even during serial operation. In particular, the composite sheet metal component is configured so that it can be used in the method according to aspects of the invention and preferably also in its configurations in accordance with the specification. The sheet metal component according to an aspect of the invention is preferably produced by reshaping in the reshaping apparatus according to an aspect of the invention as described above. Preferably, the sheet metal component is produced by means of a moulding tool device, the pressure distribution of which is or was determined according to the method according to an aspect of the invention. The sheet metal component is preferably an outer skin part of a body of a motor vehicle. The detected spatially resolved voltage signals are in particular converted into a pressure distribution. In particular, the pressure distribution represents a load on the composite sheet metal component during the reshaping process in the moulding tool device in a spatially resolved manner. In particular, the pressure distribution on the sheet metal component (without the introduced piezoelectric material) can be derived from this pressure distribution. Spatially resolved means that at least one defined position on the composite sheet metal component and / or on the moulding tool device can be derived from at least a (single) voltage signal. In particular, for determining the pressure distribution, at least one detected voltage signal is respectively associated with at least one spatial load. The voltage signals correspond in particular to the voltage and / or at least one characteristic parameter for a voltage. In particular, the detection of the voltage signals takes place over at least a part of a tool surface of the moulding tool device. In particular, the voltage signals are detected at least when the composite sheet metal component is under a compressive load in the moulding tool device. In particular, the voltage signal (for example, the amount of the voltage) is dependent on the level of the compressive load. In particular, the voltage increases with 19 08 24 increasing load. In particular, the voltage is provided only as long as a load on the composite sheet metal component by the moulding tool device occurs. In particular, the detection of the voltage signals takes place at least during the compressive load. In particular, the voltage signals depend on the load and preferably on a pressure acting on the composite sheet metal component. In particular, the pressure distribution describes a plurality of spatial loads in the moulding device and / or in the composite sheet metal component. The spatial loads are in particular pressures or another suitable parameter. In particular, the voltage signals correspond to at least one spatial load each. In particular, the spatial load is calculated from at least one detected voltage signal using a mapping algorithm. The mapping algorithm describes in particular the relationship between a parameter of the voltage signal, for example a level of the voltage, and the load. The allocation algorithm is in particular stored in a control device. In particular, at least one position datum for the spatial allocation is respectively assigned to the voltage signals. The detected voltage signals are in particular registered together with the respective position datum. In particular, the position datum represents the spatial occurrence of the voltage signal and / or the spatial arrangement of the particle or measurement point with respect to the moulding tool device and / or the composite sheet metal component. In particular, the reshaping apparatus comprises at least one control device, which is suitable and configured so as to carry out the determination of the pressure distribution using the detected, spatially resolved voltage signals and / or a temporal progression of the compressive load. In particular, the reshaping apparatus is suitable and configured so as to at least partially carry out the steps of the method presented here. In particular, the production of the composite sheet metal component takes place outside of the reshaping apparatus. In particular, the sensor device comprises a plurality of sensor elements, which respectively detect at least one voltage signal. In particular, the spatial position where the sensor elements detect their respective voltage signal is stored. In particular, the pressure distribution is displayed and / or stored by means of an output device. For 19 08 24 example, the pressure distribution can be graphically visualized and / or numerically represented. The composite sheet metal component comprises, in particular, the sheet metal component and the piezoelectric material. The sheet metal component can comprise an aluminium raw material or a steel raw material or a plastic raw material. In particular, the aluminium raw material comprises aluminium or an aluminium alloy. In particular, the steel raw material comprises steel or a steel alloy. The sheet metal component can be made of a composite raw material, which comprises at least one of the aforementioned raw materials. Further advantages and features of the present invention follow from the embodiment examples, which are described below with reference to the accompanying drawings. The drawings show: Fig. 1 a purely schematic illustration of a reshaping apparatus for use in the method according to an embodiment of the invention; and Fig. 2 a purely schematic illustration of a composite sheet metal component for use in the method according to the embodiment of the invention in a sectioned side view. Fig. 1 shows a reshaping apparatus 10 according to an embodiment of the invention for use with the method according to an aspect of the invention. The reshaping apparatus 10 here comprises a moulding tool device 1 with an upper moulding tool 11 and a lower moulding tool 21. The reshaping apparatus 10 also comprises a sensor device 5 having two sensor units 15, 25. The one sensor unit 15 is associated with the upper moulding tool 11. The other sensor unit 25 is associated with the lower moulding tool 21. The reshaping apparatus here comprises a control device 20. 19 08 24 A composite sheet metal component 4 is located in the moulding tool device 1, which here comprises a sheet metal component 2 and a piezoelectric material 3 embedded in the raw material 12 of the sheet metal component 2. In Fig. 2, the composite sheet metal component 4 is shown in further detail. For better illustration, the dimensions shown here are not shown to scale. The raw material 12 of the sheet metal component 2 is here an aluminium alloy, for example. However, a steel alloy or a plastic can also be used as a raw material 12 in an equally advantageous manner. The material 3 here comprises piezoelectric particles 13. The particles 13 here provide at least one measurement point 6. With reference to Figs. 1 and 2, the performance of the method according to the embodiment of the invention and the reshaping apparatus 10 as well as the composite sheet metal component 4 are now presented in detail by way of example. When the moulding tool device 1 is closed, the composite sheet metal component 4 is formed by the two moulding tools 11, 21. As a result of this load, the piezoelectric material 3 emits an electrical voltage. These voltages are detected with the sensor device 5 as voltage signals in a spatially resolved manner and evaluated in order to determine a spatial and temporal pressure distribution. For this purpose, a corresponding algorithm is stored in the control device 20, for example. The sheet metal component 2 is enriched with the piezoelectric material 3 by surface layer dispersion (or a similar method in which an additional raw material is introduced into the base raw material). This creates a hybrid composite raw material of a nonferrous metal and the piezoelectric nanoparticles, namely the composite sheet metal component 4. These are characterized by the fact that a mechanical load of the moulding tool device 1 or press produces an electrical voltage. The concentration of the piezoelectric particles 13 or nanoparticles in the composite sheet metal component 4 are set here so that the prevailing loads in the moulding tool device 1 are also electrically distinguished. The resulting voltage can be detected by means of the sensor device 5 accordingly. The electrical voltage increases with the mechanical load. In addition, only one electric voltage is produced as long as a mechanical load is applied to the composite sheet metal component 4. Thus, the load 19 08 24 exerted on the composite sheet metal component 4 can be represented as a temporal progression. Each particle 13 or nanoparticle serves as measurement point 6 here, which ultimately results in a cloud of points depending on the particle concentration. The denser this point cloud, the more meaningful the pressure pattern is. Sensor elements and, for example, finely tuned current sensors are present here in both the upper moulding tool 11 and the lower moulding tool 11. These detect the electrical voltage in a contactless manner and can determine the position of each measurement point 6 due to the path-based voltage drop from the actuator to the sensor and thereby represent a "digital board" (e.g. graphics of the composite sheet metal component 4 with voltages or pressures in false colours). The voltage is ultimately reverse-calculated to a pressure. The pressure pattern can thus be detected without additional marking ink and thus only by the material properties. Based on one or more pressure progressions or pressure patterns, the surface of the moulding tool device 1 can then be optimized until a desired pressure progression has been achieved. After testing or in serial operation, a sheet metal component 2, which is intended to be used in accordance with the specification, is then introduced into the moulding tool device 1 instead of the composite sheet metal component 4. For monitoring, a composite sheet metal component 4 can be reshaped as needed, such that an up-to-date pressure pattern is present. Aspects of the invention presented here completely replaces the manual covering of a piece of sheet metal with marking ink. The pressure pattern on the component is made directly detectable via the material properties of the composite sheet metal component 4. Aspects of the invention not only provides a snapshot of the pressure distribution, but also makes the entire reshaping process visible in the form of a pressure distribution or pressure curve.

Claims

1. A method of determining a pressure distribution of a sheet metal component reshaping apparatus comprising a moulding tool device, wherein the pressure distribution represents a load on the sheet metal component caused by the reshaping in the moulding tool device, comprising at least the following steps: - introducing a piezoelectric material into a raw material of the sheet metal component such that a composite sheet metal component is created, which provides an electrical voltage under mechanical loads;- arranging the composite sheet metal component in the moulding tool device; - reshaping the composite sheet metal component with the moulding tool device;- detecting spatially resolved electric voltage signals, which emanate from the composite sheet metal component during the reshaping, by means of at least one sensor device associated with the moulding tool device;- determining the pressure distribution using the detected spatially resolved voltage signals, such that a targeted post-processing of the moulding tool can be carried out;- reshaping a sheet metal component in the moulding tool device.

2. The method according to the preceding claim, wherein the voltage signals are registered as a function of time, for determining a temporal progression of a compressive load during the reshaping.

3. The method according to one of the preceding claims, wherein the introduction of the piezoelectric material into the raw material of the sheet metal component occurs in that the material is cohesively embedded in the raw material of the sheet metal component.

4. The method according to any one of the preceding claims, wherein the introduction of the piezoelectric material into the raw material of the sheet metal component occurs by surface layer dispersion.19 08 245. The method according to any one of the preceding claims, wherein the piezoelectric material comprises particles and wherein the particles each provide at least one measurement point from which a voltage signal emanates, and wherein the voltage signals of the measurement points are at least partially individually tapped with the sensor device during the reshaping.

6. The method according to the preceding claim, wherein the particles are smaller than 1 micron.

7. The method according to the preceding claim, wherein the particles are smaller than 0.5 microns.

8. The method according to any one of the preceding claims, wherein the moulding tool device comprises at least two opposing moulding tools and wherein the composite sheet metal component faces the at least two moulding tools with at least one respective region and wherein the voltage signals emanating from the at least two regions are detected in a spatially resolved manner.

9. A reshaping apparatus, in particular for use in the method according to any one of the preceding claims, comprising at least one moulding tool device for reshaping a sheet metal component and at least one sensor device for detecting spatially resolved electric voltage signals, which emanate from a composite sheet metal component arranged in the moulding tool device during the reshaping, for determining a pressure distribution of the reshaping apparatus.

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