Abstract
The invention relates to a method for producing molded parts from fiber composite material, including the following steps: a) providing a press having a first press tool, a second press tool and a membrane. The first press tool and the second press tool are movable relative to each other. The membrane is connected to one of the press tools, a cavity for a working medium being formed between the membrane and the press tool connected thereto, a working chamber for a workpiece being formed in the other press tool, and the volume of the working chamber being modifiable by a movement of the membrane when the press is closed, b) providing at least one workpiece having a workpiece volume. The workpiece has a matrix and fibers inserted therein, c) inserting the workpiece into the working chamber of the press, d) closing the press. The working chamber takes up a first volume, e) applying pressure and/or temperature to the workpiece by means of the membrane. The working chamber takes up a second volume, a hardened molded part being created from the workpiece, and f) opening the press and removing the molded part. In order to ensure continuous and uniform pressure distribution, according to the invention the first volume of the working chamber is smaller than the workpiece volume, and therefore the workpiece is already compressed at step d) and before step e).
Claims
1. A method for manufacturing moulded parts from fibre composite material, comprising the following steps: a) providing a press having a first pressing tool, a second pressing tool, and a membrane, wherein the first pressing tool and the second pressing tool can be moved relative to one another, wherein the membrane is connected to one of the pressing tools, wherein a cavity is formed between the membrane and the pressing tool connected to it for a working medium, wherein a working space is formed in the other pressing tool for a workpiece, and wherein, when the press is closed, the volume of the working space can be changed by moving the membrane, b) providing at least one workpiece with a workpiece volume, wherein the workpiece has a matrix and fibres inserted therein, c) inserting the workpiece into the working space of the press, d) closing the press, wherein the working space occupies a first volume, e) applying pressure and/or temperature to the workpiece by means of the membrane, wherein the working space occupies a second volume, and wherein a hardened moulded part is formed from the workpiece, and f) opening the press and removing the moulded part, wherein first volume of the working space is smaller than the workpiece volume, so that the workpiece is already compressed in step d) and before step e).
2. The method according to claim 1, wherein second volume of the working space is smaller than the workpiece volume, so that the workpiece is also compressed during step e).
3. The method according to claim 1, wherein step b), at least one core with a core volume is also provided, in that in step c), the core is also inserted into the working space of the press and in that the first volume of the working space is smaller than the sum of the workpiece volume and the core volume, so that the workpiece is already compressed in step d) and before step e).
4. The method according to claim 3, wherein second volume of the working space is smaller than the sum of the workpiece volume and the core volume, so that the workpiece is also compressed during step e).
5. The method according to claim 1, wherein membrane is manufactured from metal and preferably has a thickness in the range between 0.05 mm and 0.5 mm, in particular between 0.25 mm and 0.4 mm.
6. The method according to claim 1, wherein during step e) the pressure and/or the temperature of the working medium in the cavity are changed.
7. The method according to claim 1, wherein step e), the pressure of the working medium in the cavity is increased to a maximum pressure in the range between 10 bar and 50 bar, in particular between 15 bar and 30 bar.
8. The method according to claim 1, wherein step e), the temperature of the working medium in the cavity is increased to a maximum temperature in the range between 300° C. and 500° C., in particular between 330° C. and 410° C.
9. The method according to claim 1, wherein step b), a plurality of separate workpieces are provided, which are placed in step c) into the working space of the press and are connected to one another in step e), wherein a continuous hardened moulded part is formed from the workpieces.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] The invention will be explained in more detail below with reference to a drawing which simply represents a preferred exemplary embodiment, in which is shown:
[0031] FIG. 1A: a first configuration of a press for carrying out a method according to the invention in the cross-section in the open position without an inserted workpiece,
[0032] FIG. 1B: the press from FIG. 1A in open position with inserted workpiece,
[0033] FIG. 1C: the press from FIG. 1A in closed position,
[0034] FIG. 2A: a second configuration of a press for carrying out a method according to the invention in cross-section in the open position without inserted workpieces and without inserted cores,
[0035] FIG. 2B: the press from FIG. 2A in open position with inserted workpieces and inserted cores,
[0036] FIG. 2C: the press from FIG. 2A in closed position, and
[0037] FIG. 3: the sequence of a method according to the invention in a schematic representation.
DESCRIPTION OF THE INVENTION
[0038] FIG. 1A shows a first configuration of a press 1 for carrying out a method according to the invention in the cross-section in the open position without an inserted workpiece. The press 1 comprises a first, upper pressing tool 2 and a second, lower pressing tool 3. The two pressing tools 2, 3 can be moved relative to one another, for example in the vertical direction (indicated by arrows in FIG. 1). In addition, the press comprises a membrane 4 which is connected to the upper pressing tool 2. As an alternative to the configuration shown in FIG. 1, the membrane 4 could also be connected to the lower pressing tool 3. A cavity 5 is formed between the membrane 4 and the upper pressing tool 2 connected to it for a working medium, for example oil. The membrane 4 is manufactured from metal and preferably has a thickness in the range between 0.05 mm and 0.5 mm. The cavity 5 can be filled with the working medium via a channel 6. Bores 7 are provided in both the upper pressing tool 2 and the lower pressing tool 3 through which a heating and/or cooling medium can be guided.
[0039] In the configuration of the press 1 shown in FIG. 1A, a working space 8 is provided in the lower pressing tool 3 in which a workpiece (not shown in FIG. 1A) can be inserted. The working space 8 has a first volume Vi when the press is open. The two pressing tools 2, 3 have a guide 9 which can for example be formed by a protrusion 9A and a recess 9B, wherein the protrusion 9A can be provided on the lower pressing tool 3 and wherein the recess 9B can be provided on the upper pressing tool 2.
[0040] The membrane 4 is connected to the upper pressing tool 2 in the following manner: The upper pressing tool 2 has a circumferential edge element 10, which is screwed to the upper pressing tool 2 (the screw connection is not represented in FIG. 1A). 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 hollow space 12 in which a clamping device 13 is provided in which the membrane 4 is clamped. The clamping device 13 is connected to a tension anchor 14, which is led out of the upper pressing tool 2 and the edge element 10 through an opening and is pressed outwards there by a spring 15 supporting itself on the outer surface, whereby the membrane 4 is provided with prestressing. In order to seal the cavity 5, a seal 16 is provided in the gap 11, which allows movement of the membrane 4.
[0041] FIG. 1B shows the press 1 from FIG. 1A in open position with inserted workpiece 17. The areas of the press 1 that have already been described are provided in FIG. 1B with corresponding reference numerals. The difference with the position shown in FIG. 1A is that the workpiece 17 has been inserted into the working space 8 of the lower pressing tool 3. The workpiece 17 has a workpiece volume Vw1 which is slightly larger than the first volume V1 of the working space 8. As a result, the workpiece 17 must be slightly compressed in order to be inserted into the working space 8, whereby the workpiece 17 is exposed to a prestressing.
[0042] FIG. 1C shows the press 1 from FIG. 1A in closed position. The areas of the press 1 that have already been described are also provided in FIG. 1C with corresponding reference numerals. The press 1 has been closed by moving the two pressing tools 2, 3 towards one another. In the position shown in FIG. 1C, pressure and temperature are applied to the workpiece 17. Pressurisation is carried out by guiding a working medium, for example oil, through the channel 6 into the cavity 5, whereby the membrane 4 is pressed in the direction of the workpiece 17. The application of temperature can take place in different ways: One possibility is to heat the working medium guided into the cavity 5 through the channel 6 such that the heat is transferred from the working medium in the cavity 5 through the membrane 4 to the workpiece 17. Conversely, the working medium could be cooled in order to cool the workpiece 17. Alternatively or additionally to this, 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 17 can be heated or cooled. As a result of the pressure action, the working space 8 in the position shown in FIG. 1C is further reduced and has a second volume V.sub.2. This results in further compression of the workpiece 17, which in the position shown in FIG. 1C, has a second workpiece volume Vw.sub.2 corresponding approximately to the second volume V.sub.2 of the working space 8.
[0043] FIG. 2A shows a second configuration of a press 1′ for carrying out a method according to the invention in cross-section in the open position without inserted workpieces 17 and without inserted cores. The areas of the press 1′ that have already been described are also provided in FIG. 2A with corresponding reference numerals. The second configuration of the press 1′ shown in FIG. 2A differs from the first configuration of the press 1′ shown above, in particular by an enlarged working space 8′, which enables the use of cores (not represented in FIG. 2A). The enlarged working space 8′ has a first volume V.sub.1′ when the press is open.
[0044] FIG. 2B shows the press 1′ from FIG. 2A in open position with inserted workpieces 17 and inserted cores 18. The areas of the press 1′ that have already been described are also provided in FIG. 2B with corresponding reference numerals. In addition to the workpiece 17 already described in FIG. 1A to FIG. 1C, two further workpieces 17′ are now inserted into the working space 8′ of the press 1′, wherein the workpieces 17′ can for example be already prefabricated reinforcement elements with Z-shaped cross-section (e.g. “stringers” of an aircraft fuselage). The workpieces 17′ should be connected to the workpiece 17 in the subsequent production step. In order to enable a uniform pressure distribution despite the complex geometry of the workpieces 17′, a plurality of cores 18 are inserted into the working space, the shape of which is adapted to the shape of the working space 8′ and to the shape of the workpieces 17, 17′. The workpieces 17, 17′ together have a first workpiece volume V.sub.w1′ and the cores 18 together have a first core volume V.sub.k1′. The sum of the first workpiece volume V.sub.w1′ and the first core volume V.sub.k1′ (V.sub.w1′+V.sub.k1′) is slightly greater than the first volume V.sub.1′ of the working space 8′. As a result, the workpieces 17, 17′ and the cores 18 must be slightly compressed in order to be inserted into the working space 8′, whereby the workpieces 17, 17′ and the cores 18 are exposed to a prestressing.
[0045] FIG. 2C shows the press 1′ from FIG. 2A in closed position. The areas of the press 1′ that have already been described are also provided in FIG. 2C with corresponding reference numerals. The press 1′ has been closed by moving the two pressing tools 2, 3 towards one another. In the position shown in FIG. 2C, the pressure and temperature are applied to the workpieces 17, 17′. Pressurisation is carried out by guiding a working medium, for example oil, through the channel 6 into the cavity 5, whereby the membrane 4 is pressed in the direction of the workpieces 17, 17′. The application of temperature can take place in different ways: One possibility is to heat the working medium guided into the cavity 5 through the channel 6 such that the heat is transferred from the working medium in the cavity 5 through the membrane 4 to the workpieces 17, 17′. Conversely, the working medium could be cooled to cool the workpieces 17, 17′. Alternatively or additionally to this, 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 workpieces 17, 17′ can be heated or cooled. As a result of the pressure action, the working space 8′ in the position shown in FIG. 2C is further reduced and has a second volume V.sub.2′. This results in further compression of the workpieces 17, 17′ and also of the cores 18. In the position shown in FIG. 2C, the workpieces 17, 17′ together have a second workpiece volume V.sub.w2′and the cores 18 together have a second core volume V.sub.k2′. The sum of the second workpiece volume V.sub.w2′ and the second core volume V.sub.k2′ (V.sub.w2′+V.sub.k2′) corresponds roughly to the second volume V.sub.2′ of the working space 8′.
[0046] FIG. 3 finally shows the sequence of a method 100 according to the invention in a schematic representation. 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.
LIST OF REFERENCE NUMERALS
[0047] 1, 1′: Press [0048] 2: First (upper) pressing tool [0049] 3: Second (lower) pressing tool [0050] 4: Membrane [0051] 5: Cavity [0052] 6: Channel [0053] 7: Bore [0054] 8, 8′: Working space [0055] 9: Guide [0056] 9A: Protrusion [0057] 9B: Recess [0058] 10: Edge element [0059] 11: Gap [0060] 12: Hollow space [0061] 13: Clamping device [0062] 14: Tension anchor [0063] 15: Spring [0064] 16: Seal [0065] 17, 17′: Workpiece [0066] 18: Core [0067] V.sub.1, V.sub.1′: First volume (of the working space 8, 8′) [0068] V.sub.2, V.sub.2′: Second volume (of the working space 8, 8′) [0069] V.sub.w1, V.sub.w1′: First workpiece volume (of the workpieces 17, 17′) [0070] V.sub.w2, V.sub.w2′: Second workpiece volume (of the workpieces 17, 17′) [0071] V.sub.k1: First core volume (of the cores 18) [0072] V.sub.k2: Second core volume (of the cores 18)
