Device and method for processing a flat semi-finished product

Abstract

A device for machining a flat semi-finished product (1) comprises an upper part (2) with at least one recess (3), wherein at least one edge of the recess (3) is designed as a cutting edge (4). Furthermore, a lower part (5) is provided, which is designed such that the flat semi-finished product (1) can be placed and fixed between the upper part (2) and the lower part (5), and at least one movable holding device (6) which extends through the at least one recess (3) and, when the flat semi-finished product (1) is inserted into the device, is in contact with a first surface (1a) of the flat semi-finished product.In addition, a first pressure generating device (7) which is designed to exert a first pressure force on the movable holding device (6) and a second pressure generating device (8) which is designed to exert a second pressure force on a second surface (1b) of the flat semi-finished product opposite the first surface (1a) are provided.

Description

[0001] The present invention relates to a device and a method for processing a flat semi-finished product.

[0002] In the industrial processing of semi-finished products, separation processes are regularly used, with cutting processes playing a particularly important role. Shear cutting processes are predominantly used for cutting industrially manufactured sheet metal products. A special type of shear cutting is so-called fine blanking, which involves the use of particularly small cutting gaps (approximately 0.5–2% of the thickness of the sheet to be cut) and counterholders. This process delivers the best accuracy and cut surface quality in shear cutting. The sheet thickness range is between 0.5 mm and 18 mm.

[0003] Another special shear cutting process is so-called high-speed shear cutting (HGSS). This process is performed without a counterholder but at higher speeds (up to approximately 10 m / s). The achievable accuracy is generally between that achieved with shear cutting and fine blanking. This process is typically used for sheet thicknesses >3 mm. However, this process is occasionally also used for sheet thicknesses of 100 µm in bipolar plate production.

[0004] As a rule, sheets < 0.5 mm thick are no longer manufactured by fine blanking or high-speed shear cutting, but by conventional shear cutting / punching. In the field of bipolar plate production, foils (i.e., very thin sheets) with thicknesses of approximately 75 µm are already being processed. The cutting gaps can only be achieved with very high manufacturing effort. Furthermore, a certain cutting burr in the µm range is created. The alignment of the punch to the die is particularly challenging for sheet thicknesses < 100 µm, resulting in very high manufacturing effort.

[0005] For some applications, the cutting burr mentioned above must be removed using complex subsequent tool operations such as burr stamping or mechanical operations such as vibratory grinding. However, depending on the material and sheet thickness of the component, both of these options can lead to damage. Other manufacturing processes such as laser or waterjet cutting are hardly more promising in terms of producing a burr-free component, especially since these processes are also less cost-effective for high-volume production because the trimming time is longer than with shear cutting. Currently, the only option is to cut very thin sheet metal products in stacks. This is used, for example, in electrical discharge machining. In shear cutting, the stacking leads to a significantly deteriorated cut surface quality, which is why this method is rarely used in practice.

[0006] DE 10 2020 102 638 A1, for example, discloses a laminated core formed from a plurality of laminations. The laminations are burr-free. This is achieved by separating the laminations from a strip of soft magnetic alloy using laser sublimation cutting. The material to be cut from the strip is locally vaporized with a high-energy laser pulse to a depth of, for example, 30-50 µm. By stringing together several such pulses, a linear material removal occurs. By repeating this removal at the same location, it is deepened until a continuous cutting kerf is created. A particular disadvantage of this process is that it is time-consuming, thus significantly reducing its cost-effectiveness.

[0007] The present invention is therefore based on the object of proposing a device and a method for processing a flat semi-finished product, in which burr-free components can be produced without post-processing and without increased heat input into the component.

[0008] This object is achieved according to the invention by a device for processing a flat semi-finished product according to claim 1 and by a method for processing a flat semi-finished product according to claim 6. Advantageous embodiments and further developments are described in the dependent claims.

[0009] A device for processing a flat semi-finished product comprises an upper part with at least one recess, wherein at least one edge of the recess is designed as a cutting edge. Furthermore, a lower part is provided, which is designed such that the flat semi-finished product can be placed and fixed between the upper part and the lower part. At least one movable holding device is also provided, which extends through the at least one recess and is in contact with a first surface of the flat semi-finished product when the flat semi-finished product is inserted into the device.In addition, the device for processing a flat semi-finished product has a first pressure generating device which is designed to exert a first pressure force on the movable holding device and a second pressure generating device which is designed to exert a second pressure force on a second surface of the flat semi-finished product opposite the first surface.

[0010] Here, “contact” is understood to mean any direct or indirect mechanical contact. This design makes it possible to process or cut the flat semi-finished product without a cutting gap. This is made possible, among other things, by completely dispensing with a cutting punch, thus preventing the formation of a cutting gap between the cutting punch and cutting die. This device therefore also has the advantage that ultra-thin semi-finished products with thicknesses << 100 µm can be processed in such a way that the cut edges of the semi-finished product are burr-free after cutting, thus improving the quality of the manufactured components. “Burn-free” is typically defined in accordance with VDI Guideline 2906, where the burr is defined by a burr width and a burr height. Thus, “burr-free” means in particular that no burr protrudes.

[0011] By using pressure generating devices, it is possible to apply a defined compressive force to both sides of the flat semi-finished product, preventing warping of the flat semi-finished product throughout the entire machining process. This further increases the quality of the cut surface. Furthermore, the manufacturing costs for cutting punches are eliminated, allowing the device to be manufactured more cost-effectively. This device can also be used to process highly brittle materials (e.g., amorphous metals) and very ductile or highly adhesive materials (e.g., nickel). Furthermore, the elimination of the cutting punch reduces wear on the entire device.

[0012] Furthermore, the upper and lower parts can be designed so that they can be pressed against each other. This design makes it possible to easily fix the flat semi-finished product by applying a pressing force to the semi-finished product. This allows the flat semi-finished product to be easily held in the predetermined position between the upper and lower parts for the duration of the machining process. Therefore, machining errors caused by the flat semi-finished product slipping can be effectively avoided.

[0013] In addition, the first pressure generating device and / or the second pressure generating device can comprise a fluid pressure unit, in particular an oil pressure unit.

[0014] The use of a fluid pressure unit has the advantage that the device can be made very compact. It is also possible to quickly and easily vary the pressure on both sides of the flat semi-finished product independently of one another. This allows pressure differences to be quickly created between the first pressure force on the first surface of the semi-finished product and the second pressure force on the second surface of the semi-finished product. The build-up of this pressure difference or pressure gradient between the first pressure force and the second pressure force is directly proportional to the speed at which the position of the holding device changes (hereinafter referred to as the position change speed). This position change speed of the holding device is in turn directly related to the cutting speed, which means that the faster the build-up orThe faster the pressure gradient is created between the first and second pressure forces, the faster the cutting speeds. The faster cutting speed leads to an increase in the quality of the cut surface.

[0015] Furthermore, the first pressure-generating device and / or the second pressure-generating device can have a pressure-transmitting device, in particular a fluid pressure spring, particularly preferably an oil pressure spring. In this case, the first pressure force is not transmitted directly to the holding device, but rather via the pressure-transmitting device. This can improve the possibility of continuously variable movement of the holding device. The fluid pressure spring also allows the pressure changes of the pressure-generating device to be transmitted in a simple manner via the holding device to the flat semi-finished product. Furthermore, it can also be provided that the holding device is formed from at least one hold-down device.

[0016] In addition, the upper part can be guided within the lower part by a column guide. The column guide has the advantage that the upper and lower parts can always be brought together in the same way, i.e., repeatably. This means that the initial conditions at the beginning of machining can always be reproducibly created. The column guide prevents displacement of the upper or lower parts in a direction perpendicular to the applied pressing force. This increases the reliability of the device during operation.

[0017] In a method for machining a flat semi-finished product, the flat semi-finished product is placed and fixed between an upper part and a lower part, wherein the upper part has at least one recess in which at least one edge is designed as a cutting edge. Subsequently, a first pressure-generating device exerts a first pressure force on at least one movable holding device which is designed through the at least one recess in contact with a first surface of the flat semi-finished product. At the same time, a second pressure-generating device exerts a second pressure force on a second surface of the flat semi-finished product opposite the first surface, wherein the first pressure force is initially greater than the second pressure force.Next, the first compressive force is reduced or the second compressive force is increased, so that the holding device moves in the direction of action of the second compressive force and thereby a portion of the flat semi-finished product is guided past the at least one cutting edge and thereby the flat semi-finished product is separated.

[0018] First, the "direction of action of the second compressive force" refers to the direction perpendicular to the flat semi-finished product and pressing against the second surface of the flat semi-finished product. Essentially, the first compressive force and the second compressive force act against each other. As already mentioned, this process makes it possible to cut without a cutting gap, so that the manufactured components have burr-free cut surfaces. Therefore, any post-processing steps for removing the burr on the finished component can be omitted. This shortens the process time and thus increases cost-effectiveness.

[0019] This process also minimizes the amount of heat introduced into the component, preventing potential damage. Furthermore, a wide range of cutting speeds can be achieved, increasing production rates and thus reducing costs.

[0020] In addition, a constant pressing force can be maintained by pressing the upper and lower parts together during the separation process. This ensures that the flat semi-finished product remains fixed throughout the entire machining process, thus preventing burr formation due to slippage of the semi-finished product.

[0021] In addition, a cutting speed of up to 10 m / s can be achieved, which can significantly increase production rates and component quality. These high cutting speeds result from a rapid change in compressive force, creating a pressure gradient between the first and second compressive forces. This means that by rapidly generating a pressure difference, also known as a pressure drop or pressure gradient, the spatial position of the holding fixture changes accordingly. The speed at which this position of the holding fixture changes, i.e., the position change rate, is directly proportional to the speed at which the pressure gradient is created.

[0022] Furthermore, the flat semi-finished product can have a thickness in a range of 0.1 µm - 3 mm, preferably 1 µm - 0.5 mm, particularly preferably 10 µm - 100 µm. The flat semi-finished product can also be in the form of a metallic sheet or metallic foil, which refers to components whose length and width are significantly greater than their thickness, typically at least twice as large. Furthermore, flat semi-finished products include semi-finished products with flat surfaces as well as semi-finished products with curved surfaces. This means that already formed semi-finished products with a three-dimensional structure can also be used. Therefore, three-dimensional cut surfaces can also be present after trimming. By using thin semi-finished products, they can now be manufactured economically and burr-free without any edge finishing. This significantly increases the cost-effectiveness of cutting processes for thin semi-finished products.

[0023] The method can be carried out with the device described, ie the device is suitable for carrying out the method described.

[0024] Embodiments of the invention are illustrated in the drawings and are described below with reference to Fig. 1 and Fig. 2. Recurring features are provided with identical reference symbols.

[0025] They show: Fig. 1 a schematic drawing of a device for processing a flat semi-finished product with a flat semi-finished product in the open state; and Fig. 2 a schematic drawing of a device for processing a flat semi-finished product with a flat semi-finished product in the closed state.

[0026] In Fig. 1 shows a variant of a device for machining a flat semi-finished product 1, wherein the device here is divided into an upper part 2 and a lower part 5. The lower part 5 is aligned with the upper part 2 by a column guide 9, so that a reliable joining for fixing the flat semi-finished product 1 and the application of the pressing force is reliably possible. In the lower part 5 there is a chamber that is open upwards, i.e. in the direction of the upper part 2, and is completely filled with a cutting oil, for example with a hydraulic oil. A second external oil pressure unit is connected to this chamber, so that a second pressure generation device 8 is formed here from the oil chamber with the hydraulic oil and the second oil pressure unit. Thus, in this exemplary embodiment, the second pressure force is generated using compressed fluids.

[0027] Alternatively, the pressure generating device 8 can also use other fluids, such as water, or even gaseous fluids to generate pressure. This also includes the generation of pressure differences using vacuum chambers. Furthermore, it is also possible for the pressure force to be generated purely mechanically and / or electrically. Alternatively, the pressure in the active medium can also be generated by the movement of the press ram.

[0028] Furthermore, the flat semi-finished product 1 is placed on the chamber in the lower part 5, so that a surface 1b of the flat semi-finished product 1 can come into direct contact with the hydraulic oil. The position in which the device is located in Fig. 1 is referred to as the open state in which the insertion or removal of the flat semi-finished product 1 is carried out.

[0029] Located in the upper part 2 is an oil pressure spring which is pressurised via a first external oil pressure unit. The oil pressure spring, in combination with the second oil pressure unit, forms a first pressure generating device 7. The oil pressure spring is connected to a movable holding device 6. The holding device 6 is designed as a hold-down device which is movable in the upper part 2 in a direction perpendicular to the first surface 1a of the flat semi-finished product 1. In addition, the holding device 6 is designed such that it is arranged through a recess 3 in which the two edges are designed as two cutting edges 4. The hold-down device is designed such that it moves in the direction of the pressure gradient as a result of a pressure gradient between the first pressure force and the second pressure force, i.e. the hold-down device is moved by the second pressure force.

[0030] After the flat semi-finished product 1 has been placed in the device, the upper part 2 and the lower part 5 are closed under the influence of a previously defined pressing force and the device is in the closed state as in Fig. 2. As a result, the flat semi-finished product 1, here designed as a thin sheet with a thickness of 100 µm, is clamped between the upper part 2 and the lower part 5. More precisely, the flat semi-finished product 1 is now in direct contact with the hold-down device via the surface 1a and with the lower part 5 via the surface 1b. This means that the holding device 6, at this stage of the process, extends completely through the recess 3 in order to come into contact with the flat semi-finished product 1. This position is referred to below as the starting position of the holding device 6.

[0031] The pressing force generated by joining the upper part 2 and the lower part 5 is subsequently kept constant throughout the entire cutting process, preventing the sheet metal from slipping during the cutting process and thus preventing burr-prone cut surfaces. The constant pressing force ensures, among other things, the reproducibility and burr-free nature of the cut flat semi-finished products 1. Furthermore, the blank holder is permanently held in its initial position by the first pressure force generated by the first pressure generation unit and transmitted to the blank holder via the oil pressure spring.

[0032] Subsequently, a second pressure force is applied to the second surface 1b of the flat semi-finished product 1 with the aid of a second external oil pressure unit in the oil chamber in the lower part 5, which is completely filled with hydraulic oil, by pressing the hydraulic oil against the second surface 1b of the flat semi-finished product 1. The pressure forces used are calculated in advance depending on the cutting geometry and material, so that at the beginning of the process, the first pressure force is greater than the second pressure force. This means that at the beginning, there is a pressure gradient from the oil pressure spring in the upper part 2 and the chamber in the lower part 5, between which a section 10 of the flat semi-finished product 1 is clamped. In particular, the first pressure force is significantly higher than the second pressure force. For example, the pressure to generate the first pressure force is 100 bar, whereas the pressure to generate the second pressure force is only 80 bar. This leads to a "preload" of the flat semi-finished product.

[0033] In order to carry out the cutting process in the further course of the process, the first compressive force is reduced very quickly. In the example given above, this means that the pressure used to generate the first compressive force is suddenly reduced from 100 bar to 0 bar, so that the trimming takes place at 80 bar using the pressure used to generate the second mechanical compressive force. In this context, “very quickly” is understood to mean a time period in the millisecond range, i.e., in particular in the range of up to 10 ms. This creates a pressure gradient, whereby the second compressive force is now greater than the first compressive force. As a result, the second compressive force presses section 10 of the flat semi-finished product 1 in the direction of the pressure gradient, compressing the oil pressure spring. This means that the holding device 6 is moved in the direction of the pressure gradient from the starting position at a defined position change rate, i.e., away from the lower part 5.The cutout 10 of the clamped and pressurized sheet or foil is thus moved into the upper part 2 and guided past the cutting die, which is formed from the two cutting edges 4, and thus separated from the rest of the flat semi-finished product 1.

[0034] The device shown can also be controlled via a sensor unit and a control unit. This allows the device and method to be integrated into automated production environments.

[0035] Using this tool, a wide range of cutting speeds (local strain rates comparable from shear cutting to HGSS) can be achieved. Furthermore, this process can be used to cut flat semi-finished products 1 with thicknesses in a range of 0.1 µm - 3 mm, preferably 1 µm - 0.5 mm, and particularly preferably 10 µm - 100 µm. Until now, burr-free finished parts have been produced using conventional cutting processes and corresponding post-processing such as burr stamping or vibratory grinding. This is only possible to a limited extent with thin sheet metal or foils. While cutting using laser or waterjet systems would be possible in principle, laser cutting results in a significant thermal input, which alters the material properties and can potentially damage the component. Abrasive deposits can also damage the manufactured component.In addition, these processes are cost- and energy-intensive and not suitable for large-scale production. To enable cost-effective single-step trimming, there is no alternative to the described device or process.

[0036] The punch-free cutting process with a movable hold-down device and compressed fluids enables, for the first time, the burr-free trimming of very thin foils with sheet thicknesses well below 100 µm. Due to the high support effect of the compressed fluids, even very brittle materials can be cut. The trimming is independent of the contour and potentially critical radii. A major field of application here is hydrogen technologies and the general electronics industry. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2020 102 638 A1

[0006]

Claims

[1] Device for processing a flat semi-finished product (1), comprising: an upper part (2) with at least one recess (3), wherein at least one edge of the recess (3) is designed as a cutting edge (4), a lower part (5) which is designed such that the flat semi-finished product (1) can be placed and fixed between the upper part (2) and the lower part (5), at least one movable holding device (6) which is formed through the at least one recess (3) when the flat semi-finished product (1) is inserted into the device in contact with a first surface (1a) of the flat semi-finished product (1), a first pressure generating device (7) which is designed to exert a first pressure force on the movable holding device (6), and a second pressure generating device (8) which is designed to exert a second pressure force on a second surface (1b) of the flat semi-finished product (1) opposite the first surface (1a). [2] Device for processing a flat semi-finished product (1) according to claim 1, characterized by that the upper part (2) and the lower part (5) are designed to be pressed against each other. [3] Device for processing a flat semi-finished product (1) according to one of the preceding claims, characterized by that the first pressure generating device (7) and / or the second pressure generating device (8) comprise a fluid pressure unit, in particular an oil pressure unit. [4] Device for processing a flat semi-finished product (1) according to one of the preceding claims, characterized bythat the first pressure generating device (7) and / or the second pressure generating device (8) have a pressure transmission device, in particular at least one fluid pressure spring, particularly preferably an oil pressure spring. [5] Device for processing a flat semi-finished product (1) according to one of the preceding claims, characterized by that the upper part (2) can be guided in the lower part (5) by a column guide (9). [6] Method for processing a flat semi-finished product (1), in which the flat semi-finished product (1) is placed and fixed between an upper part (2) and a lower part (5), whereby the upper part (5) has at least one recess (3) in which at least one edge is designed as a cutting edge (4) and then by a first pressure generating device (7), a first pressure force is exerted on at least one movable holding device (6) which is formed through the at least one recess (3) in contact with a first surface (1a) of the flat semi-finished product (1), and at the same time a second pressure force is exerted by a second pressure generating device (8) on a second surface (1b) of the flat semi-finished product (1) opposite the first surface (1a), wherein first the first pressure force is greater than the second pressure force and then the first pressure force is reduced or the second pressure force is increased, so that the holding device (6) is moved in the direction of action of the second pressure force and thereby a section (10) of the flat semi-finished product (1) is guided past the at least one cutting edge (4) and thereby the flat semi-finished product (1) is separated. [7] Method for processing a flat semi-finished product (1) according to claim 6, characterized by that a constant pressing force is maintained by pressing the upper part (2) and the lower part (5) together during the machining process. [8] Method for processing a flat semi-finished product (1) according to one of claims 6 and 7, characterized by that a cutting speed of up to 10 m / s is achieved. [9] Method for processing a flat semi-finished product (1) according to one of the preceding claims, characterized by that the flat semi-finished product (1) has a thickness in a range of 0.1 µm - 3 mm, preferably 1 µm - 0.5 mm, particularly preferably 10 µm - 100 µm. [10] Method for processing a flat semi-finished product (1) according to one of the preceding claims, characterized by that the flat semi-finished product (1) is designed as a metallic sheet or as a metallic foil.

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