Forming tool with testing device for testing the sheet metal material used.

Abstract

Forming tool (100) for the press-based production of sheet metal components by forming a sheet metal material (M), comprising at least two mutually movable tool parts (110, 120) between which the sheet metal material (M) to be formed can be arranged and formed by performing a closing stroke (D) generated by the press, characterized in that this forming tool (100) has a testing device (200) with which the sheet metal material (M) located between the tool parts (110, 120) can be tested with regard to its forming properties during a closing stroke (D), comprising - a test stamp (210) which is pressed into the sheet metal material (M) during the closing stroke (D) in an area (A) outside the sheet metal component geometry, and - an eddy current test sensor (240) with which the deformation of the sheet metal material (M) brought about by the test punch (210) can be detected simultaneously.

Description

[0001] The invention relates to a forming tool for the press-based production of sheet metal components by forming a sheet metal material.

[0002] A forming tool of this type comprises at least two tool parts that are movable relative to each other, between which the sheet metal material to be formed can be arranged and formed by executing a closing stroke generated by the press. The tool parts are, in particular, a lower tool part, which rests on the press table, and an upper tool part, which is attached to the press ram. The forming of the sheet metal material takes place with corresponding working surfaces on the tool parts.

[0003] The mechanical material properties of the sheet metal used (such as strength and ductility, but also grain size, anisotropy, dislocation density, and the like) and the associated forming properties (referring in particular to the suitability of the sheet metal for forming) have a decisive influence on the forming process and the quality of the sheet metal components. In particular, the process parameters for the forming process and the mechanical material properties must be coordinated.

[0004] However, the sheet metal material used often does not conform to the supplier's specifications and / or is subject to variations in properties, including, for example, batch variations and aging effects. These variations can only be partially detected by regular inspections, such as tensile tests, which are also time-consuming and expensive. DE 10 2011 016 536 A1 describes a device with which the sheet metal material used can be non-destructively inspected during feeding into a press.

[0005] DE 103 12 458 B3 describes a method and a device for determining the degree of compression of a positive-locking connection between at least two components, which can be produced by means of a cold forming clinching process, in which the components to be joined are placed between a punch and a die which determines the spatial shape of the positive-locking connection and are pressed together by lowering the punch relative to the die, wherein the entire positive-locking connection is penetrated by an eddy current field by means of at least one eddy current sensor and the measurement signals obtained by means of the eddy current sensor are used to determine the degree of compression of the positive-locking connection.

[0006] Regarding the state of the art, reference is also made to DE 11 2005 000 314 T5 and AT 505 743 A1.

[0007] The invention is based on the objective of demonstrating a way in which the forming properties of a sheet metal material used for forming, in particular by deep drawing, can be reliably and unambiguously tested while avoiding or reducing at least one disadvantage associated with the prior art.

[0008] This problem is solved by a forming tool according to the invention having the features of claim 1. Preferred further developments and embodiments of the forming tool according to the invention are evident both from the dependent claims and from the following explanations.

[0009] The forming tool according to the invention is characterized in that it has (at least) one testing device with which the sheet metal material located between the tool parts can be tested with regard to its forming properties during a closing stroke, for which purpose this testing device - a test stamp that is pressed into the sheet metal material during the closing stroke in an area outside the sheet metal component geometry, and - (at least) an eddy current test sensor, with which the deformation of the sheet metal material brought about by this test stamp can be detected or recorded simultaneously.

[0010] The forming tool according to the invention is preferably a production tool for the series production of sheet metal body components for motor vehicles in a press shop. In particular, it is a deep-drawing tool. The forming of the sheet metal material in the forming tool according to the invention can be preceded and / or followed by further forming operations in other forming tools (especially within a press line) to complete the production of the sheet metal components. It is particularly provided that the input tool (in which the first forming operation is carried out) is a forming tool according to the invention. Cutting operations can optionally also be carried out in a forming tool according to the invention. In particular, it can also be a pure cutting tool, preferably press-mounted, the construction of which essentially corresponds to a forming tool as described above.

[0011] The invention provides for the integration of (at least) one testing device directly into a forming tool, with which the sheet metal material used can be tested with regard to its forming properties. Integration into the forming tool enables, on the one hand, time-saving, process-integrated inline tests and, on the other hand, direct conclusions to be drawn about the forming properties and the associated formability of the sheet metal material used. The forming properties of the sheet metal material are thus tested virtually at the point of operation under the prevailing conditions.

[0012] The local deformation of the sheet metal material, induced by the testing device and detected by the eddy current sensor, enables clear and reliable statements about the forming properties of the sheet metal material used. This allows for better and simpler verification of supplier specifications (verification and evaluation of the material quality of the starting material). Furthermore, the existing process parameters for the forming process can be more easily assessed and, if necessary, better adjusted, i.e., adapted more precisely to the forming properties of the sheet metal material. If a critical condition is detected, or if a critical change in the forming properties is registered during successive tests, corrective action can be taken by varying the process parameters for the subsequent forming process or the next press stroke.In particularly critical cases, further processing of the current batch can be stopped. This invention can increase productivity and efficiency.

[0013] Since this is a destructive test of the sheet metal material, the test die belonging to the testing device is pressed onto or into the sheet metal material in an area outside the geometry of the sheet metal component, and in particular within a residual area resulting from the manufacturing process that is not part of the sheet metal component. Preferably, this residual area outside the actual geometry of the sheet metal component is a scrap piece to be cut out later, such as a window or sunroof cutout, or a scrap piece to be cut off, such as an attached structure.

[0014] The local deformation induced by the test die is simultaneously (i.e., during the deformation and thus with the forming tool closed) automatically detected by at least one eddy current testing sensor, enabling rapid inline testing. The eddy current testing sensor is, for example, an eddy current probe. Such an eddy current testing sensor or probe has at least one excitation coil with which eddy currents can be induced in the sheet metal material, and at least one measuring coil with which the resulting magnetic field can be measured, allowing conclusions to be drawn about the characteristic values ​​and properties of the sheet metal material (reference is made to relevant technical literature and to the aforementioned DE 10 2011 016 536 A1). With such an eddy current testing sensor or probe,Eddy current probes are particularly well-suited for qualitative and / or quantitative force and stress determination in ferromagnetic sheet materials (for which further reference is made to relevant technical literature). Preferably, the eddy current test sensor is a so-called 3MA test sensor, which enables 3MA testing techniques (micromagnetic, multiparameter, microstructure, and stress analysis) based on electromagnetic interactions. Such a 3MA test sensor can also be referred to as an eddy current multi-test sensor. The 3MA testing technique can be used for both qualitative and quantitative testing of the sheet material (again, reference is made to relevant technical literature).

[0015] The test punch belonging to the testing device is located in one of the tool parts, e.g., in an upper tool part. A test die corresponding to the test punch can be located in the other tool part, e.g., in a lower tool part. Typically, the test punch does not have a separate drive. The test punch can be rigidly attached to the respective tool part or, if necessary, moved independently relative to the respective tool part via a draw cushion mechanism.

[0016] Preferably, the test device is provided with a hold-down device, in particular operable separately or together with the test punch, for fixing the sheet metal material in the area of ​​the test die and / or at least one braking or shut-off bead (or drawing or shut-off bead) for influencing the sheet metal material flow, in particular for influencing the sheet metal material flow into the test die, by means of appropriate tool design measures.

[0017] Preferably, the test punch has a spherical or at least spherical segment-shaped punch head at its free end that comes into contact with the sheet metal. It is particularly preferred that the test punch also has a circular cylindrical cross-section. The diameter of the punch head can be in the range of 8 mm to 50 mm, and preferably in the range of 8 mm to 20 mm. The local deformation of the sheet metal material produced by such a punch is based on a cupping test according to Erichsen (for which reference is made to relevant technical literature). However, the detection is not carried out by visual inspection and manual measurement, but simultaneously with the aid of the eddy current test sensor.

[0018] It is particularly preferred that the eddy current testing sensor is arranged in the test punch and especially in the area of ​​the punch head. This arrangement of the eddy current testing sensor enables very good detection of the local deformation of the sheet metal material caused by the test punch, preferably as a function of the punch stroke and especially the associated press ram stroke.

[0019] The forming tool according to the invention is, in particular, a deep-drawing tool. It is especially preferred that the testing device in this deep-drawing tool is designed to verify the consistent suitability of the sheet metal material for forming by deep drawing. To verify the consistent suitability of the sheet metal material for forming by deep drawing, a qualitative measurement of characteristic values ​​is not strictly necessary. Instead, a relative analysis or evaluation (to register changes) is sufficient, with which changes or fluctuations in properties during continuous press strokes or closing strokes (possibly also based on statistical evaluations) can be detected, so that appropriate action can be taken.

[0020] In a forming tool according to the invention, at least one further eddy current testing sensor, in particular a 3MA testing sensor, can be arranged outside the testing device. This further eddy current testing sensor can, for example, be arranged in the drawing die of the forming tool. The material properties or measured values ​​acquired with this further eddy current testing sensor can serve to verify and validate (determine the validity of) the properties or measured values ​​acquired with the testing device.

[0021] The invention is explained in more detail below by way of example and in a non-restrictive manner with reference to the single figure not to scale. Fig. Figure 1 shows a section of a forming tool according to the invention in two separate sectional views.

[0022] The forming tool 100 according to the invention, which is a deep drawing tool, comprises a tool upper part 110 with a tool working surface 112 and a tool lower part 120 with a tool working surface 122. Fig. Figure 1a shows the forming tool 100 in the open state with tool parts 110 and 120 spaced apart from each other. A sheet metal material M is positioned between the tool parts 110 and 120, in particular a steel sheet which is formed during a closing stroke D when the upper part of the tool 110 is lowered by the press (as illustrated by the arrow) by the corresponding tool working surfaces 112 and 122.

[0023] The forming tool 100 according to the invention has an integrated testing device 200 with which the sheet metal material M located between the tool parts 110 and 120 can be tested with regard to its forming properties during a closing stroke D. The test takes place virtually parallel or simultaneously with the forming of the sheet metal material M.

[0024] The testing device 200 comprises a circular-cylindrical test punch 210 rigidly arranged in the upper tool part 110, the spherical segment-shaped punch head 211 of which projects substantially perpendicularly from the tool working surface 112. Opposite the test punch 210 in the lower tool part 120, a test die 220 with a draw ring 221 is arranged, which can also be assigned to the testing device 200. A force measuring sensor for recording the punch force is designated by 230, and an eddy current test sensor arranged at a suitable location in the punch head 211 of the test punch 210 is designated by 240; these components can also be assigned to the testing device 200. The test punch 210 and the test die 220 can also be arranged in reversed positions on the tool parts 110 and 120. The test device 200 enables a so-called destructive test of the sheet metal material M, as explained in more detail below.

[0025] The test device 200 is arranged in an area A located outside the component geometry (of the sheet metal component to be produced by forming), as explained above. The material area A is subsequently separated from the actual sheet metal part (to the left of the cutting line C), for example, in a later cutting operation.

[0026] During a closing stroke D, the test punch 210 is pressed in a direction perpendicular to the sheet surface into, or from another perspective onto, the sheet material M located between the tool parts 110 and 120, whereupon the sheet material M is drawn through the drawing ring 221 and thus locally deformed. Fig. Figure 1b shows the closed state (press ram and tool upper 110 at bottom dead center). Local deformation of the sheet metal material M caused by the test die 110 can result in local sheet thinning and tears in the sheet metal material M.

[0027] During the closing stroke D, the punch travel can be recorded by a displacement measuring device (not shown). The resulting punch force can be recorded over time or over the punch travel using the force measuring sensor 230. Simultaneously, the local deformation of the sheet metal material M caused by the test punch 210 is recorded using the eddy current test sensor 240 in the punch head 211. This can be done, for example, by recording force and / or stress states (and possibly also strain states) over time or over the punch travel. All recorded values ​​can be immediately correlated and evaluated, allowing conclusions to be drawn about the forming properties and the associated formability of the sheet metal material M used. The evaluation and further processing of the recorded values ​​can be carried out using a computer system (not shown). Preferably, a relative analysis is performed.Relative evaluation, as explained above.

[0028] The predetermined indentation path of the test punch 210 can be adjusted by changing its projection (relative to the tool working surface 112). Both the test punch 210 and the drawing ring 221 are removable from the forming tool 100 and can be completely removed or replaced with functionally equivalent components of different dimensions. Reference symbol list 100 forming tools 110 Tool top 112 Tool working surface 120 Tool base 122 Tool working surface 200 test device 210 inspection stamps 211 Stamp head 220 test die 221 Draw ring 230 force measuring sensor 240 Eddy current test sensor Area A (outside the sheet metal component) C section line D Closing stroke M Sheet metal UT bottom dead center

Claims

Forming tool (100) for the press-based production of sheet metal components by forming a sheet metal material (M), with at least two mutually movable tool parts (110, 120) between which the sheet metal material (M) to be formed is arranged and can be formed by performing a closing stroke (D) generated on the press side, characterized in that this forming tool (100) has a testing device (200) with which the sheet metal material (M) located between the tool parts (110, 120) can be tested with regard to its forming properties during a closing stroke (D), comprising: - a test punch (210) which is pressed into the sheet metal material (M) in an area (A) lying outside the sheet metal component geometry during the closing stroke (D), and - an eddy current test sensor (240) with which the forming of the sheet metal material (M) brought about by the test punch (210) can be detected simultaneously. Forming tool (100) according to claim 1, characterized in that the test punch (210) has a spherical or at least spherical segment-shaped punch head (211). Forming tool (100) according to claim 1 or 2, characterized in that the eddy current test sensor (240) is a 3MA test sensor. Forming tool (100) according to one of the preceding claims, characterized in that the eddy current test sensor (240) is arranged in the test punch (210) and in particular in the area of ​​its punch head (211). Forming tool (100) according to one of the preceding claims, characterized in that the test die (210) is rigidly arranged in one of the tool parts (110, 120). Forming tool (100) according to one of the preceding claims, characterized in that the area (A) lying outside the sheet metal component geometry is a waste piece to be subsequently cut out or trimmed. Forming tool (100) according to one of the preceding claims, characterized in that it can also be used to perform a cutting operation on the sheet metal material (M). Forming tool (100) according to one of the preceding claims, characterized in that at least one further eddy current test sensor, in particular a 3MA test sensor, is arranged outside the test device (200). Forming tool (100) according to one of the preceding claims, characterized in that the test device (200) is assigned a separate hold-down device and / or at least one braking or locking groove. Forming tool (100) according to one of the preceding claims, characterized in that it is a deep drawing tool and that the testing device (200) is suitable to test the consistent suitability of the sheet material (M) for forming by deep drawing.

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