Pressing system and pressing tool for a pressing system, and method for producing a workpiece

Abstract

The invention relates to a pressing system (100), comprising: - a press (1,1´) having a first pressing tool (2) and a second pressing tool (3), the first pressing tool (2) and the second pressing tool (3) being movable relative to one another to form a working space (8), - a workpiece (19), - a pressure generating device (22) for generating a pressure curve acting on the workpiece (19) in the working space (8), - a temperature generating device (23) for generating a temperature curve acting on the workpiece (19) in the working space (8) - the workpiece (19) running through an elongation curve (DVW) depending on the pressure curve acting in the working space (8) and on the temperature curve acting in the working space (8) - the first pressing tool (2) and the second pressing tool (3) running through a respective elongation curve (DVP1, DVP2) depending on the pressure curve acting in the working space and on the temperature curve acting in the working space, characterised in that the first pressing tool (2) and / or the second pressing tool (3) are designed such that their elongation curve (DVP1, DVP2) deviates by no more than 3.5% from the elongation curve (DVW) of the workpiece (19) during at least 97.5% of the elongation curve. The invention further relates to a pressing tool and to a method for producing a workpiece.

Description

[0001] The invention relates to a pressing system comprising: a press with a first pressing tool and a second pressing tool, wherein the first pressing tool and the second pressing tool are movable relative to one another to form a working space, a workpiece, a pressure generating device for generating a pressure curve acting on the workpiece located in the working space, a temperature generating device for generating a temperature curve acting on the workpiece located in the working space, wherein the workpiece undergoes an expansion curve as a function of the pressure curve acting in the working space and the temperature curve acting in the working space, wherein the first pressing tool and the second pressing tool undergo a respective expansion curve as a function of the pressure curve acting in the working space and the temperature curve acting in the working space.

[0002] The invention further relates to a method for producing a workpiece. Pressing systems and pressing tools have been known for a long time. In contrast to a casting system, a casting tool or a casting device, a pressing system, a press and a pressing tool are always referred to when the pressing system comprises at least two pressing tools arranged such that they can move relative to one another or when the press is suitable for receiving at least two pressing tools arranged such that they can move relative to one another, wherein a working space is enlarged or reduced by relative movement of the at least two pressing tools and wherein the pressure acting on the workpiece to be machined is independent of a filling pressure of at least one material component of the workpiece.

[0003] In contrast to the press itself, a component of a pressing system is therefore also the workpiece to be produced in the press, whereby in the sense of this document the term "production" should also be understood to include the processing of a workpiece.

[0004] Accordingly, centrifugal casting, RTM or other processes and their arrangements in which at least one (material) component of the workpiece to be produced is introduced in liquid form into the closed or at least substantially closed working space are alien to the press system, the press and the pressing process on which the invention is based.

[0005] However, the RTM process, in particular, is frequently used in various variants for the production of workpieces made of fiber-reinforced composite materials, such as carbon fiber composites (CFRP), according to the state of the art, although the RTM process generally has significant disadvantages compared to a compression molding process. Among other things, the achievable results in terms of homogeneity, quality, and stability with such processes fall far short of those that would be achievable with a compression molding process.

[0006] Fiber-reinforced composites are composite materials that essentially consist of two main components: reinforcing fibers and a plastic in which the fibers are embedded ("matrix" or "resin"). By combining the two main components, the composite material can exhibit better overall properties than either component would have alone. For example, the fibers contribute to increasing the tensile strength of the composite material due to their high tensile strength in the fiber direction. The matrix, on the other hand, ensures that the fibers are held in place and protected from mechanical and chemical influences.

[0007] However, pressing processes have so far been plagued by the problem that different thermal expansion coefficients arise within the pressing systems consisting of the workpiece to be produced and the pressing tools acting on the workpiece during the pressing process. This phenomenon is well known. Those skilled in the art are aware that during cooling, either the pressing tool shrinks onto the workpiece or the workpiece shrinks onto the pressing tool.

[0008] Since composites with carbon fiber components, especially thermoplastics with embedded carbon fiber networks, e.g. CFRP, themselves have extremely low linear or volume expansion (with sometimes strong differences in the direction of the fiber layer or at an angle to it, especially orthogonally to it, which also applies to a much lesser extent to glass fiber plastics GFRP), the production of CFRP workpieces in a pressing process is particularly difficult. In contrast to their extremely low thermal expansion behavior, such composites can therefore hardly withstand forced expansion, at least not during their thermal production or processing process, or at least not without unwanted changes to their matrix, which is so important for later use. In addition, unwanted air inclusions can threaten, which in turn significantly reduces the achievable durability.

[0009] Particularly when so-called "prepregs" or "Orango sheets" are to be processed in a temperature-controlled process, the thermal expansion behavior of the pressing tools or dies can easily represent the decisive limit of processing possibilities, since the pressing tools or dies themselves must be sufficiently temperature-resistant. In addition, they must be designed for cost-effective use and long service life. Furthermore, the pressing tools or dies must be manufactured with suitable accuracy, and their surfaces must be easy to polish. Therefore, to date, they have been made of steel with virtually no alternative.

[0010] Therefore, as already mentioned above, many CFRP components are still cast using the so-called RTM process instead of being pressed from prepregs, even though this entails the disadvantages already described above.

[0011] If, for example, even just one pressing tool or die part experiences a change in length or volume that differs from the change in length or volume of the prepregs or Orango sheets or generally of the workpiece to be produced or machined, it inevitably follows that at least parts of the carrier layer experience displacements at least in some areas, internally or up to a surface, and as a result, at least structural parts often break and can therefore no longer maintain the planned structural strength.

[0012] This is particularly problematic when designing large workpieces, as varying wall thicknesses are difficult to prevent and cooling rates vary depending on the wall thickness. Furthermore, large workpieces result in correspondingly large effective lever lengths. A distortion of a few tenths of a degree is significantly more noticeable in a large workpiece, for example, over 3 or even over 5 meters in length, than in a workpiece of normal dimensions, with maximum lengths ranging from a few centimeters to about one or one and a half meters.

[0013] This can easily lead to distortion and damage to the workpiece being manufactured. As a result, the scrap rate increases or the amount of rework required increases. In some cases, however, the production of large workpieces, preferably in one piece, may also be impossible due to the occurrence of structural damage caused by the resulting stresses.

[0014] This problem becomes more acute the greater the maximum length(s) of a large piece of equipment.

[0015] In order to be able to press such large components with sufficiently uniform pressure, pressing devices and processes are known which apply hydrostatic pressure to the workpiece, which is in contact with a fixed tool, via a membrane.

[0016] An example of this is the device and method for manufacturing components made of fiber composite material known from DE 10 2017 113 595 A1. Uniform pressure is applied to the component to be manufactured by applying a flexible membrane to the component, with oil pressure acting on the membrane from the side of the membrane facing away from the component. The membrane is thus pressed onto the component surface by oil pressure. This ensures that the oil pressure acts on all sides, even with curved component surfaces, and thus that the force acting from the membrane on the component surface is the same at every point, in particular the force component acting orthogonally on the component surface.

[0017] The use of such a "membrane press" for the production of components made of fiber composite material is also known from US 2016 / 0297153 A1.

[0018] One challenge of using a diaphragm is that the diaphragm must have the smoothest possible surface throughout the entire manufacturing process to ensure uniform pressure transfer to the component surface. At the same time, the diaphragm must be reliably sealed against the cavity in which the oil pressure is built up, yet still be flexibly mounted to maintain its smooth surface even during thermally induced expansion or contraction.

[0019] Nevertheless, even with such pressing devices, processes or systems, the fundamental problem of different thermal expansion behavior within the pressing system, in particular of the pressing tool(s) compared to the workpiece(s), remains unsolved.

[0020] EP 1 666 170 A1 discloses a pressing system according to the preamble of claim 1.

[0021] Against this background, the object of the invention is to provide a pressing system with which high-quality workpieces can be produced in thermally controlled pressing processes.

[0022] In particular, it should be possible to produce workpieces with high structural strength without any loss of quality even if the workpieces are to be made from materials and / or material mixtures that have particularly low thermal expansion coefficients.

[0023] In addition, damage to the structural design of the workpiece to be manufactured should be avoided or at least reduced.

[0024] At least one of these objects is achieved in a pressing system of the type mentioned at the outset in that the first pressing tool and / or the second pressing tool are designed in such a way that their expansion curve deviates from the expansion curve of the workpiece by a maximum of 3.5% during at least 97.5% of the expansion curve.

[0025] The strain curve corresponds to the strain amount plotted over a period of time. Thus, unlike previous approaches, the invention does not merely compare the maximum amounts of thermally induced strain between two interacting materials—in this case, the press tool material and the workpiece material—but rather limits their curves and their temporal differences to a maximum of 3.5%.

[0026] The inventors have recognized that adjusting the maximum strain amounts is not effective, since the strain behavior of different materials, especially composite materials, is not linear.

[0027] In addition, there is a common misconception that the strain behavior depends solely on the material.

[0028] According to the invention, the first pressing tool and the second pressing tool are designed in such a way that their elongation curve deviates from the elongation curve of the workpiece by a maximum of 3.5% during at least 97.5% of the elongation curve, wherein the deviation from the elongation curve corresponds to the deviation of the elongation amount at the same time within a period of time, which is then preferably defined by the pressing process.

[0029] The strains or strain curves of the pressing tools and the workpiece can be determined directly (measured) or indirectly (calculated / simulated) during the pressing process. Contact or non-contact measuring methods can be used for metrological determination, for example optical measuring methods with image processing and image analysis. In computational determination, however, measured variables must be recorded from which the strain curve is calculated taking known coefficients into account. These measured variables include, in particular, the temperature or temperature curve and / or the pressure or pressure curve. These measured variables can also be determined contact-based or non-contact (e.g. temperature determination by measuring infrared radiation). The relevant coefficients include, in particular, the strain coefficient, which depends on the material used.Furthermore, factors such as the volume of a component, the surface area of ​​a component, the heat absorption capacity of a component, and form coefficients can be used in the calculation. When determining the temperature of the pressing tools and the workpiece, the determined temperature of a cooling or heating medium flowing through the pressing system can also be used if heat transfer or heat transport takes place in between. In order to determine the strains and strain curves of the pressing tools and the workpiece as precisely as possible, the highest-frequency measurement and / or calculation methods should be used. The measured or determined strain curves can be used to regulate them, for example by adjusting the temperature during the pressing process.

[0030] It is particularly preferred that the strain profile of the first pressing tool and the second pressing tool deviates from the strain profile of the workpiece by only a maximum of 3.0% during at least 98.0% of the strain profile or even by only a maximum of 2.5% during at least 98.5% of the strain profile.

[0031] Such a pressing system is therefore particularly well-suited for the production of components made of fiber-reinforced composites based on the use of prefabricated fiber-resin semi-finished products (so-called "prepregs", short for "preimpregnated fibers"). In such semi-finished products, the fibers are coated with a resin system that has not yet fully reacted, so that the semi-finished products are still in a flexible form (e.g., web-like, on rolls, or sheet-like). Only during component production are the prepregs formed and cured at high pressure and high temperatures by completing the chemical reaction. This step can then be carried out with great advantage in the present pressing system.

[0032] Accordingly, it is preferred that the workpiece comprises at least one first component and at least one second component.

[0033] This allows for the production of particularly stable workpieces, and the advantages of the pressing system can be utilized even when only one of the two material components is typically sensitive to expansion deviations. It is particularly advantageous when the first and second components bond together within the working space during a pressing process under the influence of pressure and temperature.

[0034] This allows for the production of particularly high-quality workpieces, while the use of this pressing system eliminates the risk of displacement, weakening, or overstretching that would otherwise occur in practice. This is especially true when the first component is made of fibers, e.g., in the form of a fiber mesh, especially a carbon fiber mesh, and the second component is made of a bedding matrix, especially a resin.

[0035] The prepregs already mentioned represent a mixture of these two components.

[0036] Prepregs are processed in large quantities in the aviation industry, for example. One challenge in processing is that very complex component geometries are often required in the aviation industry, for example due to reinforcement elements such as stringers. Furthermore, the aim is to reduce assembly effort, which is achieved by using fewer, but larger components. The combination of complex geometries and large component dimensions places increased demands on the devices and processes used to manufacture these components. One requirement, for example, is to ensure uniform pressure application during component production.

[0037] It is therefore also particularly advantageous if the pressing system further comprises a membrane, wherein the membrane is connected to one of the pressing tools, wherein a cavity for a working medium is formed between the membrane and the pressing tool connected to it.

[0038] This creates a hydrostatic pressure on the workpiece during the pressing process; in other words, the workpiece is reliably subjected to the same pressure in all areas. Fluctuations that occur in specific areas can also be compensated for by adding thickness tolerances between stacked prepreg sheets or panels.

[0039] Furthermore, if the diaphragm is pre-tensioned before the press closes, this ensures that the diaphragm has a smooth surface right from the start of its action on the workpiece, rather than being "smoothed" by the working fluid in the cavity. This has the advantage that the diaphragm exerts a uniform effect on the workpiece right from the start of the temperature and pressure exposure.

[0040] According to at least some of the advantages already mentioned above, it is preferred in some cases if the membrane is designed in such a way that its strain profile also deviates from the strain profile of the workpiece by a maximum of 3.5% during at least 97.5% of the strain profile.

[0041] However, since this severely limits the design options for the membrane, it may be preferable in other cases if the membrane is designed in such a way that its strain curve deviates from the strain curve of the workpiece by more than 5.0% for at least 5.0% of the strain curve.

[0042] Many aspects must be considered when designing the diaphragm. On the one hand, the diaphragm should be as flat as possible to allow rapid heat transfer. To achieve this, it can be designed to be temperature-controlled by the medium, especially oil, stored at least temporarily in the cavity. Furthermore, the diaphragm must be able to withstand high tensile loads, so manufacturing from sheet steel with thicknesses between 0.9 mm and 4.2 mm, and especially between 1.5 mm and 3.0 mm, is preferred.

[0043] In addition, the surface of the membrane is transferred to the surface of the workpiece. For this purpose, it may be desired that the membrane be particularly smooth or structured according to a specific, repeating pattern or to create a specific individual image, for example, in the form of a relief.

[0044] In addition, it may be desirable in some cases for the membrane to be magnetic.

[0045] In order to have sufficient design options here, it is desirable if the membrane does not have to be particularly restricted in terms of its expansion behavior.

[0046] Instead, it can advantageously be provided that the pressing system has a pressing plane and that the membrane is arranged to be movable relative to the pressing tool connected to it, preferably with at least one directional component, preferably running substantially parallel to the pressing plane.

[0047] For this purpose, it can advantageously be provided that the membrane, preferably by subjecting the membrane to pressure and / or temperature, preferably by means of a working medium in the cavity, past which it can be guided in relation to the seal sealing the pressing tool, and preferably that the membrane is guided past the seal at least in sections due to the expansion force associated with its expansion occurring during the pressing process, in particular temperature-induced expansion.

[0048] It is preferred that at least the first pressing tool and / or at least the second pressing tool comprises a cast iron material having a nickel content between 36.0% and 48%, preferably between 37.5% and 47%, very preferably between 39.25% and 46%, and in particular is formed from it to at least 90% by volume, in particular at least 98%, preferably in one piece.

[0049] This has the advantage that the cast iron material is cooled from the authentic crystal lattice and exhibits extremely low volume and length changes (in the positive direction: volume or length expansion) in the temperature range from -60°C to 440°C, and particularly in the temperature range from 0°C to 420°C. Another advantage is that the volume change behavior of such a cast iron material is, at least within the specified temperature ranges, largely consistent with that of CFRP materials and, depending on the precise definition of the nickel content to be selected within these limits, can be precisely tailored to individual CFRP material compositions. Furthermore, the thermal conductivity of cast iron material is significantly better than that of cast steel due to the carbon precipitated in the form of graphite, resulting in more favorable component behavior during the thermal process.

[0050] A particularly advantageous feature is that the volume change behavior of such a cast iron material is very similar to that of a GRP material, and especially to that of a CFRP material. Surprisingly, this applies not only to the absolute value related to a temperature difference to be overcome, for example, a temperature difference predetermined by a process, but also, quite unlike previous alloys produced for comparable purposes in other application areas, to the entire course of the length and / or volume change. Only in this way can the goal of minimizing or preventing microscopic or macroscopic displacements within the developing workpiece structure be achieved.

[0051] Furthermore, the alloy offers significant advantages as a cast iron material compared to a cast steel alloy: Due to the precipitation of dissolved carbon from the melt during the solidification process, the cast iron ultimately forms a composite material. This precipitation process, which is associated with a volume change in the material, has a positive effect on the shrinkage behavior of cast iron compared to cast steel. This subsequently leads to lower shrinkage behavior, ultimately also to less shrinkage cavity formation and the presence of a significantly more defined behavior - especially with regard to the course of the length or volume change behavior under the influence of temperature. Furthermore, components manufactured from this material are easier to produce in solid quality, which ultimately also represents an economic advantage.At the same time, no further heat treatment is often necessary, in contrast to cast steel, which regularly has to be subjected to heat treatment following the initial solidification process, which offers considerable economic advantages, especially for large components, for example press tools for large workpieces.

[0052] It's also important to note that cast iron allows for significantly more dampened vibration behavior of a press tool than cast steel. This is particularly important because the cycle time in which a press system opens and closes, as well as the closing time (and, of course, the opening time), can be crucial for the economically successful use of the press system.

[0053] With this in mind, it is therefore particularly preferred that the cast iron material further comprises 1.0% to 5.5%, preferably 1.5% to 4.0% carbon.

[0054] The cast iron material is most preferably characterized as follows: Cast iron material which comprises at least the following proportions in percent by weight as elements or as compounds of: carbon in the range from approximately 1.0% to 4.0%, silicon in the range from approximately 1.0% to 5.0%, manganese in the range from approximately 0.1% to 1.5%, nickel in the range from approximately 36.5% to 48.0%, chromium in the range from approximately 0.01% to 0.25%, phosphorus up to approximately 0.08%, copper up to approximately 0.5%, magnesium up to approximately 0.15%, the remainder comprising iron. The cast iron material may also have a magnesium content in the range of approximately 0.020% to 0.150%, preferably approximately 0.040% to 0.100%, particularly preferably approximately 0.065% to 0.090%. Furthermore, the cast iron material may comprise a silicon content in the range of approximately 1.0% to 4.5%, preferably approximately 1.0% to 2.5%, particularly preferably approximately 1.3% to 2.0%.

[0055] Preferably, the pressing system for producing the workpiece undergoes a pressing cycle and the pressing cycle undergoes a temperature difference in the working space of 100 K to 500 K, preferably of 170 K to 450 K, most preferably of 190 K to 250 K.

[0056] The pressing cycle, which includes the actual pressing process as well as the opening and closing of the press, should therefore undergo a temperature difference of at least 100 K (1 K = 1 degree Kelvin) at least once. However, the temperature difference should not exceed 500 K.

[0057] The range mentioned, but also the preferred ranges within this range, should generally have their starting point from an ambient or room temperature prevailing depending on the season and local environment, normally from -20°C to +45°C.

[0058] This temperature window is sufficient and appropriate for most thermally controlled processes for the production of workpieces, especially from CFRP or GFRP.

[0059] Furthermore, it is advantageous if the working space is defined by a first spatial axis, a second spatial axis and a third spatial axis and is formed at least in the direction of one of the spatial axes along a distance of at least 1.3 m, preferably at least 3.5 m, very preferably at least 5 m, more preferably at least 8 m and very particularly preferably at least 10.5 m.

[0060] In this way, workpieces with large overall lengths, e.g. body parts for vehicles, especially cars, trucks, aircraft, boats and ships, but also rotor blades for wind turbines or similarly large workpieces, can be manufactured.

[0061] The advantages of the pressing system mentioned above are particularly evident when it comes to large workpieces.

[0062] In a pressing tool for use in a press with a first pressing tool and a second pressing tool, wherein the first pressing tool and the second pressing tool are movable relative to one another to form a working space, and wherein the pressing tool is designed in such a way that it can be brought into operative connection with a pressure generating device for generating a pressure curve acting on the workpiece located in the working space and a temperature generating device for generating a temperature curve acting on the workpiece located in the working space, at least one object underlying the invention is achieved in that the pressing tool is designed for a pressing system according to one of claims 1 to 11.

[0063] The associated advantages will be apparent to those skilled in the art from the part of the present patent application describing the pressing system and apply here mutatis mutandis. Naturally, the pressing tool is therefore intended not only for use in a press, but also for use in a pressing system.

[0064] In a method for producing a workpiece, comprising the following steps: providing a press with a pressure generating device and a temperature generating device; providing a workpiece (to be produced); placing the workpiece in a work area to form a pressing system; closing the press; Applying pressure and / or temperature to the workpiece; Opening the press; At least one of the objects underlying the present invention is achieved in that the workpiece undergoes an expansion curve as a function of the pressure curve acting in the working space and the temperature curve acting in the working space, wherein the first pressing tool and the second pressing tool undergo a respective expansion curve as a function of the pressure curve acting in the working space and the temperature curve acting in the working space and the first pressing tool and / or the second pressing tool are designed in such a way that their expansion curve deviates from the expansion curve of the workpiece by a maximum of 3.5% during at least 97.5% of the expansion curve.

[0065] It is preferred that a pressing system according to one of the associated claims is used to carry out the method.

[0066] Furthermore, it is preferred that the workpiece to be formed is placed in the form of several prepregs in a solid aggregate state into the press, in particular into the working space.

[0067] The advantages associated with the method according to the invention and / or its preferred embodiments are apparent to the person skilled in the art from the part of the present patent application describing the pressing system and apply here mutatis mutandis.

[0068] The invention is explained in more detail below with reference to a drawing which merely represents a preferred embodiment. The drawing shows: Fig. 1A: a first embodiment of a press for carrying out a method according to the invention in cross section in the open position without inserted workpiece, Fig. 1B: the press from Fig. 1A in open position with inserted workpiece, Fig. 1C: the press from Fig. 1A in closed position, Fig. 2: expansion curves Fig. 3: the sequence of a method according to the invention in a schematic representation.

[0069] Fig. 1A shows a first embodiment of a press 1 for forming a pressing system 100 and for carrying out a method according to the invention for producing a workpiece 19, in cross section in the open position without inserted workpiece 19. The press 1 comprises a first - upper - pressing tool 2 and a second - lower - pressing tool 3. The two pressing tools 2, 3 are movable relative to each other, for example in the vertical direction (Z direction) (in Fig. 1 indicated by arrows). In addition, the press comprises a membrane 4, which is connected to the upper pressing tool 2. As an alternative to the Fig. 1 In the embodiment shown, the membrane 4 could also be connected to the lower pressing tool 3. In a further alternative embodiment, a second membrane could also be provided in addition to the membrane, so that both the first and the second tool would be connected to a membrane. Furthermore, it would be conceivable for a single membrane to be connected to both the first pressing tool 2 and the second pressing tool 3 and, for this purpose, preferably be deflected, for example, by 180°.

[0070] A cavity 5 for a working medium, such as oil, is formed between the membrane 4 and the upper pressing tool 2 connected to it. The membrane 4 is made of metal and preferably has a thickness in the range between 0.05 mm and 3.5 mm, but preferably between 0.2 mm and 2.2 mm. The cavity 5 can be filled with the working medium via a channel 6. Both the upper pressing tool 2 and the lower pressing tool 3 are provided with bores 7 through which a heating and / or cooling medium can be passed.

[0071] At the Fig. 1A In the embodiment of the press 1 shown, a working space 8 is provided in the lower pressing tool 3, into which a (in Fig. 1A not yet shown) workpiece 19 can be inserted. Alternatively, part of the working space can also be formed by the second pressing tool 3. Since the Figur 1B and 1CHowever, since the workpiece 19 shown is preferably to be formed from a first component 24 and a second component 25, which are joined together during a pressing process within the working space 8 under the influence of pressure and temperature, it is advantageous if the free space provided for forming the working space 8 is provided in the lower pressing tool 3.

[0072] The two pressing tools 2, 3 have a guide 9, which can be formed, for example, by a projection 9A and a recess 9B, wherein the projection 9A can be provided on the lower pressing tool 3 and wherein the recess 9B can be provided on the upper pressing tool 2.

[0073] The action of the pressure generating device 22 and the temperature generating device is indicated by arrows. Of course, it is preferred that the temperature generating device 23 also acts on both pressing tools 2 and 3, while the pressure generating device 22 automatically acts on all components delimiting the working space 8 when the press is closed. In particular, the pressure generating device can also act, at least with part of its power, on the cavity 5 delimited by the membrane 4.

[0074] The membrane 4 is connected to the upper pressing tool 2 in the following way: The upper pressing tool 2 has a circumferential edge element 10 which is screwed to the upper pressing tool 2 (the screw connection is in Fig. 1A not shown). A gap 11 is formed between the upper pressing tool 2 and its edge element 10, through which the membrane 4 is guided. The gap 11 opens into a cavity 12 in which a clamping device 13 is provided, into which the membrane 4 is clamped. The clamping device 13 is connected to a tension rod 14, which is led out through an opening from the upper pressing tool 2 and the edge element 10 and is pressed outwards there by a spring 15 supported on the outer surface, whereby the membrane 4 is provided with a preload. To seal the cavity 5, a seal 16 is provided in the gap 11, which allows movement of the membrane 4. Adjacent to the seal 16, a device 17 for varying the sealing force FD is provided. Adjacent to the spring 15, a device 18 for varying the spring force FF is provided.

[0075] Fig. 1B shows the press 1 from Fig. 1A in open position with inserted workpiece 19. Those areas of the press 1 which have already been described are in Fig. 1B with corresponding reference symbols. The difference to the Fig. 1A shown position is that the workpiece 19 (to be formed) has been placed in the working space 8 of the lower pressing tool 3.

[0076] The workpiece 19, which is preferably still to be formed, consists of a first component 24 and a second component 25, which are stacked one above the other in a plurality of thin layers in the form of so-called prepregs or organic sheets. The individual prepregs have thicknesses of 0.12 mm to 0.72 mm, preferably 0.16 mm to 0.32 mm, and consist of fiber, in particular carbon fiber, braids embedded in a resin matrix. The chemical bond between the matrix (resin) and the fibers, or the fiber braid, is only completed within the pressing system 100, i.e., during a pressing cycle, under the influence of pressure and temperature.

[0077] Fig. 1C shows the press 1 from Fig. 1A in closed position. Those areas of press 1 that have already been described are also in Fig. 1C with corresponding reference symbols. Press 1 was closed by moving the two pressing tools 2, 3 towards each other. In the Fig. 1C In the position shown, the workpiece 19 is subjected to pressure and temperature. The pressure is applied by feeding a working medium, for example oil, through the channel 6 into the cavity 5, whereby the membrane 4 is pressed towards the workpiece 19. Alternatively, the cavity 5 can also already be filled with the working medium. The working medium can be stored against a pressure relief valve in the cavity and already pre-tensioned. When the press is closed, the pressure of the working medium can then increase within the cavity and thus also be exerted on the (forming) workpiece in response. The pressure of the working medium can then increase when the press 1, 1' is closed, for example, from a pre-tension range between 1.2 bar and 2.5 bar to a working range between 16 bar and 50 bar, in extreme cases even up to 70 bar, and can be maintained at this level for the duration of the press.

[0078] The application of temperature can be achieved in different ways: One possibility is to heat the working medium fed through the channel 6 into the cavity 5, so that the heat from the working medium in the cavity 5 is transferred through the membrane 4 to the workpiece 19. Conversely, the working medium could be cooled in order to cool the workpiece 19. Alternatively or additionally, it can be provided that the bores 7 are flowed through by a heating and / or cooling medium, whereby first the two pressing tools 2, 3 and subsequently also the workpiece 19 can be heated or cooled. As a result of the pressure effect, the workpiece 19 is in the Fig. 1C compressed in the position shown.

[0079] The illustrated pressing system 100 comprises: a press 1, with a first pressing tool 2 and a second pressing tool 3, wherein the first pressing tool 2 and the second pressing tool 3 are movable relative to one another to form a working space 8, a workpiece 19, a pressure generating device 22, for generating a pressure curve acting on the workpiece 19 located in the working space 8, a temperature generating device 23 for generating a temperature curve acting on the workpiece 19 located in the working space 8, wherein the workpiece 19, depending on the pressure curve acting in the working space 8 and the temperature curve acting in the working space 8, Figur 2 shown expansion curve DVW, whereby the first pressing tool 2 and the second pressing tool 3, depending on the pressure curve acting in the working chamber and the temperature curve acting in the working chamber 8, each have a respective expansion curve, also shown in Figur 2 shown expansion curve DVP1, DVP2, is characterized here by the first pressing tool 2 and / or the second pressing tool 3 being designed in such a way that their expansion curve DVP1, DVP2 is as shown in Figur 2 visible while at least 97.5% of the strain curve deviates by a maximum of 3.5% from the strain curve DVW of the workpiece 19.

[0080] The pressing system 100 thus undergoes a pressing cycle to produce the workpiece 19. The pressing cycle can involve a temperature difference of 100 K to 500 K, preferably 170 K to 450 K, and most preferably 190 K to 250 K, acting in the working chamber 8. During the entire pressing cycle, the strain curve DVP1, DVP2 deviates from the strain curve DVW of the workpiece 19 by a maximum of 3.5% for at least 97.5% of the strain curve.

[0081] For this purpose, the first pressing tool 2 and / or the second pressing tool 3 is preferably formed from a cast iron material which has a nickel content of between 36.0% and 48%, and in particular is formed therefrom to at least 90% by volume, preferably in one piece.

[0082] The cast iron material further comprises 1.0% to 5.5%, preferably 1.5% to 4.0% carbon and is preferably characterized as follows: Cast iron material which comprises at least the following proportions in percent by weight as elements or as compounds of: carbon in the range of approximately 1.0% to 4.0%, silicon in the range of approximately 1.0% to 5.0%, manganese in the range of approximately 0.1% to 1.5%, nickel in the range of approximately 36.5% to 48.0%, chromium in the range of approximately 0.01% to 0.25%, phosphorus up to approximately 0.08%, copper up to approximately 0.5%, magnesium up to approximately 0.15%, the remainder comprising iron. The cast iron material may also have a magnesium content in the range of approximately 0.020% to 0.150%, preferably approximately 0.040% to 0.100%, particularly preferably approximately 0.065% to 0.090%. Furthermore, the cast iron material may comprise a silicon content in the range of approximately 1.0% to 4.5%, preferably approximately 1.0% to 2.5%, particularly preferably approximately 1.3% to 2.0%.

[0083] The working room 8 of the Fig 1 A bis 1C and Figur 2 The pressing system 100 shown is defined by a first spatial axis X, a second spatial axis Y and a third spatial axis Z, and is formed at least in the direction of one of the spatial axes X, Y, Z along a distance L of at least 1.3 m, preferably at least 3.5 m, very preferably at least 5 m, more preferably at least 8 m and very particularly preferably at least 10.5 m.

[0084] In Figur 2 The time course of a pressing cycle of the pressing system 100 is shown along the horizontal axis. The strain amounts are plotted over time along the vertical axis, resulting in the strain curves DVM, DVW, DVP1 and DVP2, the values ​​of which depend on the influence of the pressure curve acting in the working space and the temperature curve acting in the working space. Press tools 2 and 3 experience the pressure and temperature curves acting in the working space, or at least the temperature curve acting in the working space only secondarily, since it is not the task of a pressing system 100 to subject as many system components as possible to thermal stress. This would be nonsense from an ecological and economic point of view. Nevertheless, the strain curves DVP1 and DVP2 of the two pressing tools 2 and 3 deviate from the strain curve of the workpiece 19 by a maximum of 3.5% over at least 97.5% of their strain curve.In fact, apart from a small time delay, which is even enlarged here out of scale for better visibility, and lasts a maximum of up to 1%, but extremely maximum up to 2% of the press cycle time and in which the maximum difference in the elongation behavior between DVP1 or DVP2 to DVW is still less than 1.5%, the curves lie practically exactly on top of each other during the entire process cycle time and are therefore also shown on the same line in the further course of t.

[0085] In contrast, Figur 2 It is also clear that the strain curve of the membrane 4 deviates by more than 5% from the strain curve of the workpiece at the same time during at least 7.5% of its strain curve.

[0086] The expansion behavior of the membrane 4 is also much more linear. Of course, the expansion curves of the workpiece and the pressing tools can also take on other curve shapes. The decisive factor remains that the first pressing tool 2 and / or the second pressing tool 3 are designed such that their expansion curves DVP1, DVP2 deviate from the expansion curve DVW of the workpiece 19 by a maximum of 3.5% during at least 97.5% of the expansion curve.

[0087] The sharper drop in the curves shown in the example depends on the rapid cooling of the selected pressing process. In principle, however, the heating and cooling rates can also be equivalent. In some cases, it is also conceivable that the heating process is carried out more rapidly than the cooling process. As shown, a holding section is normally provided between the heating and cooling sections of the process, in which pressure and temperature are maintained at a constant level. The expansion behavior then generally adapts, but can creep slightly and therefore assume a slightly rounded shape, which is also somewhat exaggerated.

[0088] Fig. 3 Finally, FIG. 1 shows a schematic representation of the sequence of a method 100 according to the invention. The method 100 comprises the following steps: 101: Providing a press, 102: Providing a workpiece, 103: Inserting the workpiece, 104: Closing the press, 105: Applying pressure and / or temperature to the workpiece, 106: Opening the press. Bezugszeichenliste:

[0089] 1, 1':Press 2:First (upper) pressing tool 3:Second (lower) pressing tool 4:Membrane 5:Cavity 6:Channel 7:Bore 8:Working space 9:Guide 9A:Protrusion 9B:Recess 10:Edge element 11:Gap 12:Cavity 13:Clamping device 14:Tie rod 15:Spring 16, 16':Seal 17, 17':Device (for changing the sealing force FD ) 18:Device (for changing the spring force FD ) 19:Workpiece 22:Pressure generating device 23:Temperature generating device 24:First component 25:Second component 26:Pressing level 100:Pressing system AStart of the pressing cycle EEnd of the pressing cycle DVM: Strain curve of the membrane DVP1: Strain curve of the first pressing tool DVP2: Strain curve of the first pressing tool DVW: Strain curve of the workpiece L:Route p:pressure t:time T:temperature X:First spatial direction (longitudinal direction) Y:Second spatial direction (width direction) Z:Third spatial direction (height direction)

Claims

1. Pressing system (100) comprising: - a press (1, 1') with a first pressing tool (2) and a second pressing tool (3), wherein the first pressing tool (2) and the second pressing tool (3) can be moved relative to one another to form a working space (8), - a workpiece (19) - a pressure generating device (22) for generating a pressure profile acting on the workpiece (19) located in the working space (8) - a temperature generating device (23) for generating a temperature profile acting on the workpiece (19) located in the working space (8) - wherein the workpiece (19) passes through an expansion profile (DVW) as a function of the pressure profile acting in the working space (8) and the temperature profile acting in the working space (8) - wherein the first pressing tool (2) and the second pressing tool (3) pass through a respective expansion profile (DVP1, DVP2) as a function of the pressure profile acting in the working space and the temperature profile acting in the working space, characterised in that the first pressing tool (2) and / or the second pressing tool (3) are designed in such manner that their expansion profile (DVP1, DVP2) deviates by a maximum of 3.5% of the expansion profile (DVW) of the workpiece (19) during at least 97.5% of the expansion profile.

2. Pressing system (100) according to claim 1, characterised in that the workpiece (19) comprises at least one first component (24) and at least one second component (25).

3. Pressing system (100) according to claim 2, characterised in that the first component (24) and the second component (25) connect to one another during a pressing process within the working space (8) under the influence of pressure and temperature.

4. Pressing system (100) according to any one of the preceding claims, characterised in that the pressing system (100) further comprises a membrane (4), wherein the membrane (4) is connected to one of the pressing tools (2, 3), wherein a cavity (5) for a working medium is formed between the membrane (4) and the pressing tool (2, 3) connected thereto.

5. Pressing system (100) according to any one of the preceding claims, characterised in that the membrane (4) is designed in such manner that its expansion profile (DVM) also deviates by a maximum of 3.5% from the expansion profile of the workpiece (DVW) during at least 97.5% of the expansion profile.

6. Pressing system (100) according to any one of claims 1 to 4, characterised in that the membrane (4) is designed in such manner that its expansion profile (DVM) deviates by more than 5.0% from the expansion profile of the workpiece (DVW) during at least 7.5% of the expansion profile.

7. Pressing system (100) according to any one of the preceding claims, characterised in that the pressing system (100) has a pressing plane (26) and in that the membrane (4) is arranged so as to be movable with respect to the pressing tool (2, 3) connected thereto, preferably with at least one directional component running preferably substantially parallel to the pressing plane (26).

8. Pressing system (100) according to any one of the preceding claims, characterised in that at least the first pressing tool (2) and / or at least the second pressing tool (3) comprises a cast iron material with a nickel content of between 36.0% and 48%, preferably of between 37.5% and 47%, quite preferably of between 39.25% and 46%, and is formed in particular at least 90%, in particular at least 98% by volume fraction, preferably integrally, therefrom.

9. Pressing system (100) according to any one of the preceding claims, characterised in that the cast iron material further comprises 1.0% to 5.5%, preferably 1.5% to 4.0% carbon.

10. Pressing system (100) according to any one of the preceding claims, characterised in that the pressing system (100) passes through a pressing cycle for manufacturing the workpiece (19) and the pressing cycle passes through a temperature difference of 100 K to 500 K, preferably of 170 K to 450 K, quite preferably of 190 K to 250 K, acting in the working space (8).

11. Pressing system (100) according to any one of the preceding claims, characterised in that the working space (8) is defined by a first spatial axis (X), a second spatial axis (Y) and a third spatial axis (Z) and is designed at least in the direction of one of the spatial axes (X, Y, Z) along a distance (L) of at least 1.3 m, preferably at least 3.5 m, quite preferably at least 5 m, more preferably at least 8 m and quite particularly preferably at least 10.5 m.

12. Method for manufacturing a workpiece, comprising the following steps: - Providing (101) a press (1) with a pressure generating device (22) and a temperature generating device (23) - Providing (102) a workpiece (19) (to be produced) - Inserting (103) the workpiece (19) into a working region (8) to form a pressing system (100) - Closing (104) the press (1) - Applying (105) pressure (p) and / or temperature (T) to workpiece (19) - Opening (106) the press, characterised in that the workpiece (19) passes through an expansion profile (DVW) as a function of the pressure profile acting in the working space (8) and the temperature profile acting in the working space (8), wherein the first pressing tool (2) and the second pressing tool (3) pass through a respective expansion profile (DVP1, DVP2) as a function of the pressure profile acting in the working space and the temperature profile acting in the working space and the first pressing tool (2) and / or the second pressing tool (3) are designed in such manner that their expansion profile (DVP1, DVP2) deviates by a maximum of 3.5% from the expansion profile (DVW) of the workpiece (19) during at least 97.5% of the expansion profile.

13. Method according to the preceding claim, characterised in that a pressing system (100) according to any one of the associated claims is used to carry out the method.

14. Method according to the preceding claim, characterised in that the workpiece (19) to be formed is inserted into the press (1), in particular into the working space (8), in the form of a plurality of prepregs in a fixed aggregate state.

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