Stamping tool with multiple movements

Abstract

The invention relates to a tool for stamping a composite blank having a thermoplastic matrix reinforced by continuous fibres, as well as a stamping method using such a tool, the tool comprising: - a die comprising a cavity (110) having a bottom (111) and side walls (112); - a punch (120), the outer shape of which matches the cavity of the die, said punch comprising a middle portion (123) and at least two moveable side portions (121, 122) slidingly connected to the middle portion (123), such that when the side portions are blocked from moving translatably in the strike direction (190) against the bottom of the die, the movement of the middle portion (123) in the same direction causes the side portions to move translatably perpendicularly to the strike direction (190).

Description

Multi-mobility stamping tools

[0001] The invention belongs to the field of tools, more particularly to the field of stamping tools used for shaping thermoplastic matrix composite materials.

[0002] More specifically, the invention relates to a stamping tool comprising mobilities and specifically multiple mobilities.

[0003] Stamping is a shaping technique consisting of deforming a blank between a punch and a die of complementary shapes separated by an air gap corresponding to the thickness of the part produced.

[0004] This shaping is carried out by a relative translational movement of the punch tending to bring it closer to the die, then to penetrate into it, forcing the blank, initially covering the entrance to the impression of the die, and caught in the air gap between the die and the punch, to deform so as to reproduce the shapes of the punch and the die during the penetration of said punch into said die.

[0005] Generally, the assembly is installed on a press, the die being fixed and the punch being fixed to the press slide, the striking being carried out according to a vertical translation.

[0006] A tool is said to be "movable" when it includes elements that move differently from the striking movement. These elements are located on the punch or die, but are generally located on the punch.

[0007] According to non-limiting examples of mobility, these elements move during the strike in a direction comprising a component perpendicular to the direction of the strike, or in the direction of the strike but at a speed different from the strike speed, or even in the opposite direction to the direction of the strike.

[0008] These mobilities can be driven by electric, pneumatic or hydraulic effectors or be generated by appropriate mechanical links driven by the striking movement itself.

[0009] Document EP 2 243 617 describes an example of such a mobile tool for stamping a blank made of a thermoplastic matrix composite, and comprising an element movable in a direction perpendicular to the striking direction so as to carry out folding.

[0010] A mobility tool is particularly useful for producing a part with rolled edges by stamping when the composite blank has a continuous fiber reinforcement with fibers that have little or no plasticity, such as glass or carbon fibers.

[0011] In fact, the deformation of such a blank occurs by interlaminar and interfiber sliding, that is to say by local modifications of the distance between the fibers within acceptable limits.

[0012] Thus, to deform such a blank, it must be brought to a sufficient temperature, generally equal to or greater than the melting temperature of the polymer constituting the matrix of the composite, so that this polymer no longer opposes, or very little, resistance to the interlaminar movements of the reinforcements and allows their relative sliding.

[0013] In simplified terms, the stamping of a thermoplastic matrix composite blank, reinforced with continuous fibers having little or no plasticity, involves placing this blank, by heating, in a state where it loses a good part of its cohesion. This cohesion is restored at the end of stamping by compacting the blank between the walls of the punch and the die, so that when the final part includes at least two flanged edges, mobility is necessary to obtain both the forming of the blank and then the compaction of said flanged edges.

[0014] The re-compaction phase at the end of stamping is essential because it must both eliminate voids in the lamination and avoid wringing, as excessive compaction tends to eject the resin from between the fibers. The ability to control thicknesses in a tool with mobility is therefore essential.

[0015] Document EP 1 543 942 describes another example of mobility tooling for stamping a composite blank with a thermoplastic matrix and continuous fiber reinforcement, in particular for producing a part with rolled edges in the shape of a half-box.

[0016] This prior art device comprises a punch, provided with movable side pieces connected to the punch by elastic connections, said side pieces are capable of moving away from a central part of said punch, said central part comprising a wedge-shaped part connected to the punch and capable of moving vertically relative to the side pieces when, during stamping, the punch reaches the bottom of the die, this relative movement of the wedge-shaped part causing the side pieces to move apart, thus making it possible to compact the fallen edges of the half-box-shaped part.

[0017] The kinematics of this prior art device cause the lateral parts to move in a pivoting motion under the effect of the wedge-shaped part being pressed in. The pivot point being close to the bottom of the die, on the one hand the compacting pressure on the edges is not uniform, and furthermore, the kinematics of this device does not allow the production of parts with flanged edges having a pinch, that is to say for which the distance between two flanged edges, measured parallel to the bottom, decreases as one moves away from said bottom.

[0018] Such parts, in the shape of a half-box with pinched edges, are particularly found in aeronautics, for example for wing ribs.

[0019] In addition, the mobility mechanism does not allow precise adjustment of the compaction of the part obtained by these mobilities as well as the pairing of the punch with the die.

[0020] Document FR2717735 describes a tool comprising lateral pressing means for consolidating a box-shaped part into shape. This tool is not suitable for stamping a consolidated composite thermoplastic blank.

[0021] Similarly, document DE741682 describes a tool for consolidation in shape whose technical solutions are not applicable to the stamping of a consolidated composite blank.

[0022] The tooling and method described below aim to resolve the shortcomings set out above and, to this end, relate to a stamping tool comprising:

[0023] - a press comprising a fixed plate, a movable plate and a slide for moving the movable plate towards the fixed plate in a striking direction;

[0024] - a forming die capable of being fixed on the fixed plate of the press and comprising an imprint comprising a bottom, side walls and an entry width;

[0025] - a punch capable of being mounted on the movable plate of the press, the external shape of which is matched with the imprint and comprising a central part and at least two movable lateral parts in sliding connection with the central part, the central part comprising an end located between the at least two movable lateral parts and forming a corner between the at least two lateral parts,

[0026] - pressure means acting on the at least two movable lateral parts to press them against the central part, so that a width of the punch is less than the entry width;

[0027] such that the at least two movable lateral parts being stopped in translation in the direction of striking against the bottom of the impression, a continuation of the movement of the central part in the direction of striking relative to the at least two movable lateral parts, causes the movement of the at least two movable lateral parts relative to each other in translation towards the side walls of the impression, perpendicular to the direction of striking, achieving a first lateral expansion of the punch in a direction of expansion towards the side walls of the impression and that the width of the expanding punch is equal to or greater than the entry width.

[0028] Thus the lateral expansion of the punch is achieved by translation kinematics of the movable lateral parts which allows, on the one hand, a uniform compaction of the fallen edges of the part between these movable lateral parts and the side walls of the impression and on the other hand, allows said punch to carry out the stamping of a part with fallen edges with a strong pinching of these.

[0029] The tooling can be implemented according to the embodiments and variants set out below, which are to be considered individually or according to any technically effective combination.

[0030] Advantageously, the central part of the punch comprises a shoulder forming a stop at its end between the at least two movable lateral parts, the at least two movable lateral parts being stopped in translation in the direction of striking relative to the central part, pressed against the shoulder forming a stop by at least one spring acting on the at least two movable lateral parts movable in the direction of striking between the at least two movable lateral parts and the movable plate of the press. This arrangement makes it possible to retract the expansion of the punch and to raise it after striking during the simple movement of withdrawing the punch even if the part has fallen edges with strong pinching.

[0031] According to one embodiment, the punch comprises two additional movable lateral parts in sliding connection with the central part forming a wedge between the two additional movable lateral parts, so as to produce a second lateral expansion of the piston in an expansion direction perpendicular to the expansion direction of the first expansion. This embodiment is suitable for the manufacture of a half-box-shaped part comprising 4 fallen edges.

[0032] Advantageously, the wedge-shaped central part comprises two parts and comprises between these two parts means for adjusting a width of the central part according to the direction of expansion. This embodiment allows precise pairing of the mobility punch with the die and precise adjustment of the thicknesses of the parts obtained by stamping using this tooling.

[0033] The tooling may be implemented in a method for producing a part comprising a core with a core thickness and at least two flanged edges each having a flanged edge thickness, at least one of the at least two flanged edges being oriented relative to the core at an angle of less than 90°, the method comprising steps:

[0034] - match the punch with the die imprint by means for adjusting the width of the central part of the punch according to the core thickness and the thicknesses of the fallen edges;

[0035] - obtain a composite blank comprising a thermoplastic polymer matrix and continuous fibrous reinforcements whose width is greater than the entry width;

[0036] - heating the composite blank to a temperature equal to or greater than a melting temperature of the polymer matrix;

[0037] - position the composite blank above the impression and stamp the composite blank between the punch and the impression according to a striking stroke of the movable plate until the end of the punch reaches a distance from the bottom of the impression equal to the thickness of the core;

[0038] - continue the stroke of the movable plate to move the movable lateral parts of the punch to distances from the side walls of the impression equal to the thicknesses of the fallen edges and that a width of the expanding punch is greater than or equal to the entry width to compact the part;

[0039] - cooling the part under pressure between the punch and the impression to a temperature below the melting temperature of the polymer matrix to consolidate the part; and

[0040] - move the mobile plate in the opposite direction and unmold the part.

[0041] This process allows for the mass production and cost-effective manufacture of high-quality composite structural parts with high structural performance relative to their mass, in particular aircraft wing ribs with pinched edges.

[0042] The invention is implemented according to the preferred embodiments set out below, which are in no way limiting, and with reference to in which: Fig. 1

[0043] represents, according to a simplified schematic sectional view, an example of the production of the tooling at the start of the stamping stroke; Fig.2

[0044] shows according to the same cut as the, the tooling at the end of the stamping stroke; Fig.3

[0045] is a perspective view of an exemplary embodiment of a punch comprising lateral parts movable in two intersecting directions; Fig.4

[0046] shows the punch according to a partial and exploded perspective view; Fig.5

[0047] schematically represents the section of an aircraft wing according to a cut defined in this same figure; Fig.6

[0048] shows a flowchart of an example of a process implementation using the tooling.

[0049] Throughout the text, the term "blank" refers to a rigid flat blank, cut to a suitable contour and intended to be deformed to obtain a three-dimensional part.

[0050] In this case, the tooling is shown without the finished part.

[0051] , according to an exemplary embodiment, the tooling comprises a press (not entirely shown) comprising a fixed plate (101) and a movable plate (102). The movable plate is capable of being moved towards the fixed plate, for example by means of a hydraulic cylinder, in a striking direction (190), so as to carry out a stamping operation.

[0052] According to this exemplary embodiment, a forming die (110) comprising an imprint (115) is fixed to the fixed plate (101) by suitable means. The imprint is delimited by a bottom (111) and side walls (112). According to this exemplary embodiment, the side walls (112) of the imprint have a pinch, at an angle (192) measured relative to the striking direction (190), so that the width of the imprint is greater at the bottom (111) than at the entrance of the imprint on the opposite face of the forming die.

[0053] A punch (120) is attached to the movable platen (102) and moves with it. The punch comprises a wedge-shaped central part (123) inserted between movable side parts (121, 122).

[0054] According to this embodiment, the central part comprises at its end, between the movable lateral parts (121, 122), a shoulder part (125) forming a stop.

[0055] The two movable lateral parts (121, 122) are in sliding connection on the central wedge-shaped part (123), and are pushed against the shoulder (125) forming a stop by compression springs (130) acting between said movable lateral parts (121, 122) and the fixed plate (102) of the press.

[0056] The position of the stop provided by the shoulder is advantageously adjustable by suitable means such as peelable shims (126).

[0057] According to this embodiment, a tension spring (135) tends to press the movable lateral parts (121, 122) into contact with the wedge-shaped central part (123).

[0058] The shapes of the punch (120) and the imprint (115) are matched, so that the punch is able to be inserted into the imprint leaving between the punch and the imprint an air gap corresponding to the thickness of the part to be produced (not shown).

[0059] , the punch (120) descending into the imprint (115), when the ends of the movable side pieces (121, 122) come into contact with the bottom (111) of the imprint (115), directly in this figure but in practice with the bottom of the part to be produced, the latter being included between the bottom of the imprint and the end of the punch, if the striking movement (190) is continued, then the central part (123) of the punch moves in the striking direction (190) between the movable side pieces (121, 122) and relative to them.Given the wedge shape of the sliding connection between the movable side pieces (121, 122) and the central part (123) of the punch, this relative movement produces an expansion of the punch, the movable side pieces moving in directions (291, 292) perpendicular to the striking direction (190) and approaching the side walls (112) of the impression, while the compression springs (130) acting on the movable side parts in the striking direction are compressed.

[0060] Thus, the use of this tooling makes it possible to compress a thickness of material located between the punch and the impression, and more particularly between the movable side parts and the side walls of the impression, including in connection zones between the side walls (112) and the bottom (111) of the impression. This ability of the tooling to carry out this lateral compression allows the stamping and then the consolidation of a composite blank with a thermoplastic matrix and continuous fiber reinforcement, previously brought to a temperature close to the melting temperature of the polymer constituting its matrix.

[0061] Returning to the, in this figure the movable lateral parts (121, 122) of the punch are brought closer to each other so that the width (100) of the punch is less than the entry width (116) of the opening of the impression and that it can penetrate into the impression although the lateral walls of the impression are pinched.

[0062] , the penetration of the central part (123) of the punch between its movable lateral parts (121, 122) causes an expansion of the width of the punch so that its width (200), under the effect of this expansion, can become greater than the entry width of the impression.

[0063] Thus, the tooling is suitable for stamping a part comprising rolled edges with a high pinch angle (192), up to 30°.

[0064] At the end of a stamping operation, the movable platen (102) is raised so as to move it away from the fixed platen (101). The compression springs (130) continue to press the movable side parts (121, 122) of the punch towards the impression, while the tension spring (135) presses the movable side parts against the central part (123) of the punch, so that the relative movement of the wedge-shaped central part (123) causes the movable side parts to tighten and the punch to shrink, which can be removed from the impression.

[0065] , the wedge-shaped central portion is shown with symmetrical slopes so that for a given relative displacement along the striking direction (190) of the central portion (123), the movable lateral portions (121, 122) move laterally by the same stroke (291, 292). A person skilled in the art understands that the central portion (123) may have asymmetrical slopes so that a given relative displacement of the central portion (123) along the striking direction (190) leads to different strokes (291, 292) of the right-hand movable portion (122) and the left-hand movable portion (121) in the figure, in order to adapt to a specific part geometry, in particular different pinching of the flanged edges on each side.

[0066] Returning to the, the central part (123) is advantageously made up of two parts (1231, 1232) and comprises means (127), for example peelable shims, between said two parts so as to adjust the width of the central part (123) and thus precisely define the air gap between the movable lateral parts and the lateral walls of the imprint at the end of the stroke of the punch as well as the precise pairing of the punch with the imprint.

[0067] , according to an exemplary embodiment the punch (320) comprises movable lateral parts (321, 322, 323, 324) capable of carrying out an expansion along intersecting planes. Thus, with reference to the x, y, z reference frame, during the descent of the punch, 2 of the movable lateral parts (321, 322) carry out an expansion of the punch along a direction y in a plane zy and the two other movable lateral parts (323, 324) carry out an expansion of the punch along a direction x in a plane xz.

[0068] All the characteristics and embodiments developed above apply both to the movable lateral parts (321, 322) in one plane and to the movable lateral parts (323, 324) in another plane.

[0069] The person skilled in the art understands that the intersecting planes in which the different expansions are carried out are not necessarily perpendicular on the one hand, and on the other hand that this embodiment is not limited to a combination of expansions along only two intersecting planes but that the mobilities can act in a plurality of intersecting planes.

[0070] , the central part (423) of the tooling may comprise an assembly of several parts, and means (4271, 4272) between these parts for precise adjustment of the air gaps between the punch and the side walls of the impression.

[0071] According to this embodiment, the central part (423) and the movable lateral parts (321, 322, 323, 324) are connected by grooves (425) made in the central part (423) which cooperate with tenons (426) on the internal faces of the movable lateral parts. These assemblies ensure the translational stop of the movable lateral parts perpendicular to their respective direction of expansion but also the technical functions of the shoulder (125) forming a stop.

[0072] The selection of materials constituting the various parts of the tooling depends on the nature of the materials constituting the shaped blank and in particular on the stamping temperature and the thermal expansion characteristics of these materials.

[0073] By way of non-limiting examples, the various parts are made from a carbon tool steel comprising chromium, magnesium and molybdenum, or from an INVAR® type steel comprising iron and nickel.

[0074] The tool's ability to produce thermoplastic matrix composite parts by stamping, including pinched edges, is advantageously used to integrate functions on certain parts which can thus be produced in one piece whereas, according to prior art techniques, these required the assembly of several components. Reducing the number of components and the number of assemblies makes it possible to reduce manufacturing costs and lighten the structural elements.

[0075] By way of non-limiting example, the wing (510) of an aircraft (500) comprises a plurality of ribs (550) extending between the lower surface (520) and the upper surface (530).

[0076] These ribs (ouribs) are presented as pieces with rolled edges, comprising a core (551) and soles (552, 553), said soles being rolled edges relative to the core and ensuring the junction of said ribs with the skins of the sail, intrados and extrados sides.

[0077] Due to the section of the wing which tapers towards its end and widens towards its connection with the fuselage, some of these ribs, in order to be able to be connected to the skins, must have edges which are dropped with a pinch, that is to say that at least one of the angles (591, 592) between the web (551) and the soles (552, 552) of the rib is less than 90°.

[0078] According to the prior art, these ribs are then produced by adding a specific component in place of at least one of the fallen edges.

[0079] The implementation of the tooling allows these parts to be produced in one piece, i.e. without any additional parts, directly by stamping.

[0080] Thus, according to one embodiment, a method uses the tooling for the production by stamping of a composite blank with a thermoplastic polymer matrix and continuous fiber reinforcement.

[0081] The final part to be obtained is, for example, a sail rib, comprising a core and at least two flanges with flanged edges, at least one of said flanges extending in a direction forming an angle of less than 90° relative to the core.

[0082] According to an adjustment step (610), the punch is adjusted in particular by means of the peelable shims between the two parts of the central part so that the air gap between the impression and the various parts of the punch at the end of the striking stroke of the press is adapted to the target thicknesses of the part.

[0083] According to a obtaining step (620), a composite blank (601) intended to be formed by the method is obtained according to techniques known from the prior art. The composite blank comprises a thermoplastic polymer matrix characterized in particular by a melting temperature, and if relevant by a crystallization temperature or a glass transition temperature depending on the nature of the polymer. As non-limiting examples, for aeronautical applications, said polymer is a polyetheretherketone (PEEK), a polyetherketone-ketone (PEKK), a polyetherimide (PEI) or a polyphenylene sulfide (PPS),

[0084] The blank is reinforced by continuous reinforcing fibers (611), i.e. extending continuously between two edges of the blank (601), of glass, carbon or aramid, alone or in combination, without these examples being limiting. These fibers have the particularity of not exhibiting plasticity at the temperatures of use of the part as well as at the temperatures of implementation of the process.

[0085] The blank is obtained by techniques known from the prior art. It is for example obtained by high-pressure water jet cutting in a pre-consolidated composite plate, or by a process as described in document EP 3 096 940.

[0086] The blank thus obtained is flat and rigid.

[0087] According to a heating step (630), the plane is heated to a temperature equal to or higher than the melting temperature of the polymer matrix. For this purpose and according to an exemplary implementation, the plane is transported on a polyimide sheet or in a tool as described in document EP 3 065 931 under an infrared radiant panel (621) and heated in the open air to this temperature.

[0088] According to a stamping step (640) the hot blank (601) is placed on the forming die while the punch is moved away from it.

[0089] A width of the blank (616, 617) is, in all directions, greater than the width of the opening (116) of the impression, so that the blank (601) rests on the edges of the forming die and can only conform to the shapes of the impression if it is pushed into the impression and deformed by the punch.

[0090] Then, the punch is moved towards the forming die so as to deform the blank. This deformation is possible by the relative sliding of the continuous fibers of the composite in the polymer matrix heated to a temperature where it offers almost no resistance to this relative movement, the blank having been deconsolidated during the heating step and also decompacted during this first stamping phase.

[0091] During a compacting step (645), which is practiced, the stamping phase continuously follows, when the striking stroke comes to wedge the bottom of the part, which will constitute the core, between the end of the punch and the bottom of the impression under a certain pressure, which depends on the characteristics of the compression springs between the punch and the movable plate (130); the continuation of the stroke of the movable plate of the press produces the lateral expansion of the punch which has the effect of compacting the edges fallen between the side walls of the impression and the movable side walls of the punch.

[0092] Compaction eliminates voids between fibers ensuring uniform distribution of fibers and matrix throughout the entire thickness of the part.

[0093] During a consolidation step (650) the part is cooled while maintaining the pressure in the tooling, i.e. without moving the movable plate of the press relative to the previous step, until the part reaches a temperature suitable for its demolding. To this end, according to exemplary embodiments not shown, the forming die may comprise heating and cooling means for better temperature control during the different phases.

[0094] During a demolding step (660) the movable platen is moved away from the forming die and the part is demolded.

[0095] The part is then water-jet or milled to remove any uncompacted edges.

[0096] The above description and the embodiments show that the invention achieves the intended purpose and allows in particular, by stamping a composite blank with continuous fiber reinforcement, the production of a part with pinched edges, while providing precise control of the thicknesses of both the base and the flanged edges. Of course, the tooling and the method described are also suitable for producing a part with flanged edges without pinching or even flaring. In the latter case, the presence of mobilities offers increased control of the thicknesses of both the core and the flanged edges, and consequently better part quality in terms of material health.

Claims

Stamping tooling comprising: - a press having a fixed platen (101), a movable platen (102) and means for moving the movable platen towards the fixed platen in a striking direction (190); - a forming die suitable for being fixed on the fixed platen of the press and having an impression (110) comprising a bottom (111), side walls (112) and an entry width (116) measured between the side walls; - a punch (120) suitable for being mounted on the movable platen of the press, the external shape of which is matched with the impression and comprising a central part (123) and at least two movable side parts (121, 122, 321, 322, 323, 324) in sliding connection with the central part (123), the central part comprising an end situated between the at least two movable side parts and a wedge shape between the at least two movable side parts;- pressure means (130, 135) acting on the at least two movable lateral parts to press them against the central part (123), so that a width of the punch (100) is less than the entry width (116); characterized in that the at least two movable lateral parts being stopped in translation along the direction of impact (190) against the bottom of the impression, a continuation of the movement of the central part (123) in the direction of impact relative to the at least two movable lateral parts causes the movement of the at least two movable lateral parts relative to each other in a translation (291, 292) towards the lateral walls of the impression, perpendicular to the direction of impact (190), achieving a first lateral expansion of the punch in an expansion direction towards the lateral walls (112) of the impression and that the width (200) of the expanding punch is equal to or greater than the entry width (116).; Tooling according to claim 1, wherein the central part (123) of the punch comprises a shoulder (125) forming a stop at the end between the at least two movable lateral parts (121, 122) stopped in translation in the direction of the strike relative to the central part (123) and pressed against the shoulder forming a stop by at least one spring (130) acting on the at least two movable lateral parts (121, 122) in the direction of the strike between the at least two movable lateral parts and the movable plate (102). Tooling according to claim 1, wherein the punch (320) comprises two additional movable side parts (323, 324) in sliding connection with the central part comprising a wedge shape between the two additional movable side parts, so as to achieve a second lateral expansion of the piston (320) along an expansion direction (x) perpendicular to the expansion direction (291, 292) of the first expansion. Tooling according to claim 1, wherein the wedge shape of the central part (123, 423) comprises two parts (1231, 1232) and includes between these two parts means (127, 4271, 4272) for adjusting a width of the central part according to the direction of expansion. A method for producing a part comprising a core (551) with a core thickness and at least two folded edges (552, 553), each having a folded edge thickness, at least one of the two edges being oriented relative to the core at an angle (591, 592) less than 90°, the method employing tooling according to claim 4 and comprising steps of: - matching (610) the punch with the cavity by means (127, 4271, 4272) to adjust the width of the central portion as a function of the core thickness and the thicknesses of the folded edges; - obtaining (620) a composite blank (601) comprising a thermoplastic polymer matrix and continuous fibrous reinforcements (611) having a width (616, 617) greater than the entry width (116); - heating (630) the composite blank to a temperature equal to or greater than the melting temperature of the polymer matrix;- position the composite blank above the mold cavity and stamp (640) the composite blank (601) between the punch and the mold cavity with a striking stroke until the end of the punch reaches a distance from the bottom (111) of the mold cavity equal to the core thickness; - continue the stroke of the moving platen to move the movable lateral parts of the punch until distances from the lateral walls of the mold cavity equal to the thicknesses of the dropped edges and a width (200) of the expanding punch is greater than or equal to the entry width (116) to compact (645) the part; - cool the part under pressure between the punch and the mold cavity to a temperature below the melting temperature of the polymer matrix to consolidate (650) the part; and - move the moving platen in the opposite direction and demold (660) the part.

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