Molding core

Abstract

Molding Core The invention relates to a molding core (1) for molding a part (2) having a hollow section (3), particularly an undercut. The molding core (1) is formed of at least two molding elements (4) and a cohesive material (5), the molding elements (4) being assembled and held together by the cohesive material (5) to form a single-piece molding core (1). Figure to be published with the abbreviation: Figure 4

Description

Title of the invention: Molding core TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of molding and, more particularly, of undercut molding.

[0002] The present invention relates to a molding core and, in particular, a molding core introduced into a mold so as to obtain hollow undercut parts in a molded part. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] In the field of molding, it is common to use a mold core in addition to the mold itself. A mold core is a piece, usually rigid, for example made of sand or metal, inserted into a mold during assembly so as to obtain hollow sections in a molded part.

[0004] A molding core can also be used without a mold when it is used to manufacture a part by adding material around the core, without using a mold for an exterior of the part, as in filament winding molding around the core.

[0005] Draft angle is the inclination of the mold walls necessary to facilitate demolding of the part. Undercut refers to a shape of the part that prevents direct demolding, that is, when the molded part has a retention cavity that prevents molding material used to seal it from escaping.

[0006] In the field of undercut molding, several solutions exist to be able to extract the molding core from the molded part.

[0007] For example, cores made of fusible material are known at temperatures of at least a few degrees above the temperature required for solidification of a constituent material of the molded part and, at most, a melting temperature compatible with non-degradation of the molded part.

[0008] Cores made of material soluble in a solvent compatible with non-degradation of the molded part are also known.

[0009] These two techniques allow the molded part to be demolded by complete destruction of the molding core.

[0010] The use of a molding core made of fusible material is not suitable for molding parts made from a heat-sensitive material, for example, in the case of moldings containing a resin or a polymer. Indeed, such moldings are damaged when the fusible material is heated to melt it. Furthermore, the time required to melt the molding core can be lengthy, This increases the duration and cost of molding processes using a molding core made of fusible material.

[0011] The use of a molding core made of soluble material is not always advantageous because the solvent used to dissolve the soluble material core is likely to attack the molded part, when the latter includes a resin or a polymer, which impairs the quality of the surfaces and the strength of the molded part.

[0012] Another technique involves using a molding core with at least one deformable outer surface, for example, made of silicone, which allows for the extraction of the molded part. However, such a technique is only usable in molding processes where no pressure or vacuum is exerted on the molding core, which considerably limits its use. Furthermore, such a technique is notably incompatible with molding processes such as draping, resin transfer molding, and filament winding.

[0013] It is also possible to use an inflatable bladder, but such a solution does not allow for precise molding of the internal surfaces. Furthermore, removing the bladder after molding can prove difficult when the cavity is large and the opening small. Finally, the bladder must maintain its airtightness and flexibility during molding, which is not always compatible with the temperatures and molding materials used.

[0014] Other molding solutions use a shrinkable core, in which the core comprises several parts arranged to be moved between an assembled position, for molding, and a shrinkable position, for demolding. Snap-in cores and expandable cores, which are quite similar solutions, are also known. The major disadvantage of such cores is their high cost. Furthermore, such cores cannot always be adapted to all undercut shapes.

[0015] An alternative solution is to use a mold core made up of an assembly of removable parts. However, the process of assembling and disassembling the core is very time-consuming, considerably increasing the duration and cost of such molding processes using this type of mold core. Furthermore, the reconditioning of the removable parts can also be problematic.

[0016] Solutions based on a mold core made up of several elements are also disadvantageous when these elements are not perfectly immobilized relative to each other. Indeed, in such a case, the mold core is likely to deform, leading to molding errors and resulting in a non-conforming molded part.

[0017] Similarly, when the constituent elements of the mold core are not perfectly assembled, unwanted gaps may be present. Thus, molding material can become lodged in these gaps, creating inaccuracies in molding and can resist the removal of the mold core from the molded part. It is then necessary to force the extraction of the mold core, which can cause tearing of molding material at the point of excess material and damage the molded part.

[0018] The object of the invention is, in particular, to provide a new molding technique for manufacturing a non-removable form, especially one with undercuts, based on the use of a molding core. The molding core should preferably be compatible with draping molding, for example, hand draping, with or without autoclave, resin transfer molding, filament winding, and / or thermocompression molding.

[0019] Such a molding core should preferably be easy, quick, and inexpensive to produce. It should be rigid, mostly reusable, provide accurate molding, and be adaptable to all undercut shapes.

[0020] The constituent parts of the molding core must be perfectly assembled and immobilized relative to each other, without unwanted gaps between the constituent elements of the molding core.

[0021] In addition, the placement, use and removal of the molding core should preferably be easy and quick. Summary of the invention

[0022] The invention offers a solution to the problems mentioned above, by providing a molding core, in particular undercut, formed of several molding elements, in particular several rigid molding elements, assembled and immobilized together by a cohesive material, in particular a rigid cohesive material, in particular a degradable cohesive material and more specifically a rigid cohesive degradable material.

[0023] One aspect of the invention relates to a molding core for molding a part having a hollow part, in particular undercut, in which the molding core is formed of at least two molding elements, in particular at least two reusable rigid molding elements, and of a cohesive material, in particular of a degradable cohesive rigid material, in which the molding elements are assembled and immobilized together by the cohesive material to form a one-piece molding core.

[0024] The molding core of the invention has many advantages and addresses all the disadvantages previously mentioned.

[0025] Formed from several molding elements assembled together, the molding core advantageously allows a great freedom of shape and makes it possible to obtain any molding shape.

[0026] Consisting particularly solely of elements which are in a rigid state during molding and immobilized together by the cohesive material, the molding core of the invention does not deform during molding and can advantageously be used in most molding processes, in particular those where pressure or depression is exerted on the molding core.

[0027] The cohesive material which assembles the molding elements together being degradable, it can be melted, dissolved or broken up, so that the molding elements can easily be disassembled after molding and extracted from the molded part so that they can be reused later.

[0028] Although the cohesive material can be in a rigid state when used as the molding core, it can advantageously be supplied in liquid form, for example, polymerizable or molten, during the manufacturing of the molding core and during the assembly of the molding elements. Thus, during the production of the molding core, the use of a cohesive material in liquid form also allows for the quick and easy assembly of the molding elements, without creating undesirable gaps between them. Indeed, since the cohesive material fills all the spaces in the core that are not required for molding, the core presents no unwanted retention areas for the molding material.

[0029] Since they are not damaged during molding, the molding elements can be reused indefinitely, without having to manufacture new ones, which advantageously reduces the production costs of the molding core and the molded part.

[0030] Indeed, only a small part of the molding core, formed by the cohesive material, is potentially damaged, or even destroyed, during the molding process. The molding core is advantageously designed so as to use the smallest possible amount of cohesive material.

[0031] According to one aspect of the invention, the cohesive material is positioned at the interface of at least two molding elements, which advantageously allows these molding elements to be assembled easily and quickly, while using little cohesive material.

[0032] According to another aspect of the invention, the cohesive material is a fusible material, capable of having a melting point lower than that of the material constituting the molding elements.

[0033] This advantageously allows the molding elements to be easily and quickly released for extraction from the molded part by melting the cohesive material. It also allows the molding elements to be quickly and easily bonded to the cohesive material to create the molding core.

[0034] According to another aspect of the invention, the cohesive material is a soluble material, capable of dissolving in the presence of a solvent, in particular one that does not damage the material constituent of the molding elements.

[0035] This advantageously allows the molding elements to be easily and quickly released for extraction from the molded part by dissolving the cohesive material, without any risk of damaging the molding elements when the solvent used is compatible with them.

[0036] According to another aspect of the invention, the cohesive material is a fractionable material, capable of breaking apart when it receives an appropriate amount of energy.

[0037] This advantageously allows for the easy and rapid release of molding elements for extraction from the molded part using a cohesive material, for example, a friable material, or a very hard but also very brittle material, and / or one that cannot be easily and rapidly dissolved or melted. It also allows for the release of molding elements for extraction by applying a mechanical retraction force to them, but also by using an external source of mechanical energy, for example, a shock or ultrasonic source, capable of fragmenting the cohesive material without affecting the molding elements.

[0038] According to another aspect of the invention, on a face in contact with the cohesive material, the molding element has a raised element forming a mechanical grip in the cohesive material.

[0039] The raised element advantageously strengthens the bond between the molding element and the cohesive material, so that the molding elements are rigidly assembled and immobilized together. When the cohesive material is a fragmentable material, the raised element also facilitates the fragmentation of the cohesive material, particularly when the molding elements are separated.

[0040] According to another aspect of the invention, on a face in contact with the cohesive material, a molding element has a hollow part forming a retention cavity occupied by cohesive material.

[0041] The retention cavity advantageously strengthens the bond between the molding element and the cohesive material. It also allows one molding element to be joined to another without having to encase it in cohesive material or to apply cohesive material to the entire interface between the two molding elements.

[0042] According to another aspect of the invention, a molding element has a channel having at least a first orifice opening onto a face in contact with the cohesive material, and a second orifice opening towards the outside of the molding core, the channel being at least partially occupied by the cohesive material.

[0043] In addition to the advantages provided, the preceding aspect of the invention also allows the cohesive material to be introduced in a liquid state through the channel for insertion between the molding elements to be assembled. The channel is also particularly advantageous when planned in conjunction with a retention cavity provided in another molding element located opposite, because it allows in particular to fill the retention cavity with cohesive material during the making of the molding core.

[0044] In addition to the characteristics just mentioned, the molding core according to one aspect of the invention may have one or more complementary characteristics from among the following, considered individually or according to all technically possible combinations: - the molding core is formed from two molding elements assembled and immobilized together by the cohesive material; - the molding elements are assembled by injecting a cohesive material; - the molding core is formed by overmolding with a degradable material; - the cohesive material is metal, a metal alloy, a thermosetting polymer, a thermoplastic polymer or a salt.

[0045] Another aspect of the invention relates to a molding method for a part having a hollow part, in particular undercut, in which the hollow part is obtained by means of a molding core as described above.

[0046] According to one aspect of the invention, the preceding molding process comprises at least: - an assembly stage, during which molding elements are assembled with cohesive material to create a molding core; - a step in the production of the molded part during which molding material is added around the molding core; - a stage of rupture, fusion, dissolution and / or fragmentation, during which the cohesive matter is broken, melted, dissolved and / or fragmented; and - a removal step, during which the cohesive material and molding elements are removed from the molded part.

[0047] In addition to the characteristics just mentioned, the molding process according to one aspect of the invention may have one or more complementary characteristics from among the following, considered individually or according to all technically possible combinations: - the molding is a draping molding, a resin transfer molding, a filament winding molding, a compression molding and / or a foundry-type molding; - when the cohesive material is a fusible material, it is melted by induction or by placing the molded part in an oven; - when the cohesive material is a fractionable material, the mechanical energy necessary for its fragmentation is supplied by exerting a mechanical force of removal on the molding elements connected by the fractionable material, using shocks or using ultrasound.

[0048] An additional aspect of the invention relates to a molded part having a hollow part, in particular undercut, the molded part being obtained by the process as described above.

[0049] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0050] The present invention will be better understood and other features and advantages will become apparent upon reading the following detailed description, which includes embodiments given by way of illustration with reference to the accompanying figures, presented by way of non-limiting examples, which may serve to complete the understanding of the present invention and the explanation of its implementation and, where appropriate, contribute to its definition, on which:

[0051] [Fig. 1] is a perspective view of a molding part having a hollow undercut section.

[0052] [Fig.2] is a perspective view of a molding shape to be inserted into a mold in order to obtain the undercut part of the molding part of [Fig.1].

[0053] [Fig.3] is a schematic cross-sectional view of the molded part of [Fig.1] and of a molding core according to a first embodiment of the invention.

[0054] [Fig.4] is a schematic cross-sectional view of the molded part of [Fig.1] and of a molding core according to a second embodiment of the invention.

[0055] [Fig.5] is a schematic cross-sectional view of the molded part of [Fig.1] and of a molding core according to a third embodiment of the invention.

[0056] [Fig.6] is a view similar to [Fig.5], in which molding elements are during the extraction of the molded part.

[0057] [Fig.7] is a schematic cross-sectional view of the molded part of [Fig.1] and of a molding core according to a fourth embodiment of the invention.

[0058] [Fig.8] is a schematic cross-sectional view of the molded part of [Fig.1] and of a molding core according to a fifth embodiment of the invention.

[0059] [Fig.9] is a perspective view of a molding core according to the invention intended to molding the undercut hollow parts of a thrust reverser grid for a turbojet nacelle. DETAILED DESCRIPTION

[0060] The figures are shown by way of illustration and in no way limit the invention. In Figures 1 to 8, the shape of a part to be molded and that of a molding core or molding form are intentionally simplified and illustrate only one very simple case theoretical whose sole purpose is to better explain the invention.

[0061] Fig. 1 is a perspective view of a moldable part 2 having a hollow undercut. More particularly, in Fig. 1, the moldable part 2 is a tube bent at a sharp angle, while the molding form 1 or the molding core 1 suitable for molding the hollow part of the bent tube is shown in Fig. 2.

[0062] The molding core 1 according to the invention is intended for molding the part 2 having a hollow portion 3 with an undercut. To this end, the molding core 1 is designed to create hollow portions in the molded part 2.

[0063] The molding core 1, according to the invention, is formed of at least two molding elements 4, in particular and particularly advantageously reusable, and of a cohesive material 5.

[0064] The molding elements 4 are assembled and immobilized together by the cohesive material 5.

[0065] Advantageously, the molding elements 4 are rigid.

[0066] The term “cohesive” refers to a material or substance that ensures cohesion, unity between two elements.

[0067] According to the invention, the cohesive material 5 is degradable. Furthermore, the cohesive material 5 can also be rigid.

[0068] The term “degradable” means a material or substance which, as a result of chemical, thermal and / or mechanical action, loses a cohesive character, for example by becoming liquid, friable, decomposing, breaking down and / or fragmenting.

[0069] Such a degradable material or substance can also be reusable.

[0070] Thus, according to the invention, the degradable cohesive material 5 can be removed from a narrow and / or hard-to-reach place where it is located.

[0071] The term “rigid” means a part, material or solid substance, capable of resisting mechanical stresses, in particular torsion and / or shear, chemical and / or thermal stresses, which does not deform during molding.

[0072] The term "reusable" means a part, material or substance which is not permanently damaged during molding or demolding and which can be used again to make another mold.

[0073] Positioned between the molding elements 4 to be assembled, the cohesive material 5 ensures the cohesion of the molding elements 4 to form a one-piece molding core 1, i.e., a single, assembled unit. Since it is located in a region where molding elements 4 could not be extracted from the molded part 2 after molding, at least a portion of the cohesive material 5 is situated in the part of the molding core 1 intended to form the undercut hollow portion 3 of the molded part 2.

[0074] Figures 3 and 4 are respectively schematic cross-sectional views of the part 2 to be molded of [Fig.1] and of the molding core 1 according to a first embodiment and a second embodiment of the invention.

[0075] In figures 3 and 4, the cohesive material 5 can be preferentially positioned at the interface of at least two molding elements 4, that is to say where two neighboring molding elements 4 meet.

[0076] Preferably, the least amount of cohesive material 5 is used as possible, especially when it is expensive.

[0077] According to one embodiment of the invention, the cohesive material 5 is a fusible material, that is, a material that can be melted or liquefied. After molding, it is then possible to melt the cohesive material 5, for example by induction or by placing the molded part 2 in an oven. The cohesive material 5 then loses its cohesive character and allows the molding elements 4 to be released for extraction from the molded part 2.

[0078] The melting point of the cohesive material 5 is lower than that of the constituent material of the molding elements 4, which makes it possible not to degrade the molding elements 4 during the melting of the cohesive material 5.

[0079] The melting of the cohesive material 5 does not need to be complete, provided that after melting, even partial melting of the cohesive material 5, the molding elements 4 are released for extraction from the molded part 2 and that the cohesive material 5 has become sufficiently viscous, liquid and / or reduced to be able to be extracted from the molded part 2.

[0080] Within the framework of the invention, a material is considered fusible if, for example, it has a melting point at least 20°C lower than the melting point of the constituent material of the molding elements 4. In addition, the melting point of the fusible cohesive material 5 is less than 1000°C.

[0081] According to another embodiment of the invention, the cohesive material 5 is a soluble material, that is to say, a material that can be solubilized or dissolved. After molding, it is then possible to dissolve the cohesive material 5, for example in the presence of a solvent, water also being considered as a solvent, arranged so as not to damage the material constituting the molding elements 4. The dissolution of the soluble cohesive material 5 can be accelerated by thermal and / or mechanical actions.

[0082] The dissolution of the cohesive material 5 does not need to be complete, provided that after dissolution, even partial, of the cohesive material 5, the molding elements 4 are released for extraction from the molded part 2 and that the cohesive material 5 has become sufficiently viscous, liquid and / or reduced to be able to be extracted from the molded part 2.

[0083] In the context of the invention, a material is considered soluble if, for example, it has a solubility greater than 0.1 mole per liter of solution at room temperature.

[0084] According to a further embodiment of the invention, the cohesive material 5 is a fractionable, decomposable, or fragmentable material, that is, a material that can be reduced to smaller elements. After molding, it is then possible to fractionate, decompose, break, fragment, and / or break down the cohesive material 5 by supplying it with suitable energy, particularly mechanical energy, so as to release the molding elements 4 for their extraction from the part 2. The cohesive material 5 must be able to break down into pieces small enough for these to be extracted from the molded part 2.

[0085] The energy required to fractionate the cohesive material 5 can be supplied simply by applying a mechanical retraction force to the molding elements 4 connected by the fractionable cohesive material 5. Such energy can also be supplied in the form of impacts, for example by striking the molded part 2 and the molding core 1 while taking care not to damage them. It can also be supplied in the form of ultrasound, for example by immersing the molded part 2 and the molding core 1 in an ultrasonic bath.

[0086] Within the scope of the invention, a material is considered fractionable if it withstands the various stresses that may occur during molding without breaking, while it does not withstand other stresses that could reasonably be anticipated during demolding. Thus, according to the invention, a cohesive material 5 will be considered fractionable if, while resisting the various mechanical stresses resulting from molding, the cohesive material 5 is nevertheless brittle or friable with respect to greater mechanical stresses that are foreseeable by a person skilled in the art.

[0087] The cohesive material 5 that can be split can, for example, be a relatively hard but also very brittle material. The cohesive material 5 that can be split can also be in the form of a compacted material whose cohesion can be broken by supplying it with suitable energy.

[0088] It should be noted that the cohesive material 5 can also be a combination of the characteristics previously mentioned, that it can exhibit any combination of fusible, soluble and / or fractionable characteristics.

[0089] Thus, the cohesive material 5 according to the invention can be fusible, soluble, and fractionable, which allows for several possible means to be available for releasing the molding elements 4 for their extraction from the molded part 2. Such means can be used alone, jointly, and / or sequentially, the person skilled in the art choosing how they wish to release the elements rigids assembled and immobilized together by the cohesive material 5.

[0090] By way of example, it is particularly possible to supply the cohesive material 5 according to the invention in the form of a solidified sand, compacted and bonded by an additive. In such a cohesive material 5, the sand provides the necessary rigidity and a low-cost mass of material, while the additive provides cohesion to the cohesive material 5 and enables it to bond and immobilize the molding elements 4. In such a case, the additive may be soluble or fusible, while the sand solidified by the additive may be fractionable, for example by crumbling and / or becoming powdery.

[0091] Within the same molding core 1 according to the invention, not all the molding elements 4 are necessarily assembled together by the cohesive material 5. Only some of them can be mutually assembled by the cohesive material 5, while others are assembled in a different way.

[0092] Similarly, the cohesive material 5 is not necessarily the same everywhere, and different cohesive materials 5 can be used within the same molding core 1 according to the invention.

[0093] Although the cohesive material 5 is preferentially positioned at the interface of at least two molding elements 4, it can also be provided differently between the molding elements 4 so as to assemble and immobilize them mutually.

[0094] Figures 5, 7 and 8 are respectively schematic cross-sectional views of the molded part 2 of [Fig.1] and of the molding core 1 according to a third embodiment, a fourth embodiment of the invention and a fifth embodiment of the invention.

[0095] Thus, as shown in [Fig.8], the cohesive material 5 can be provided around the periphery of a molding element 4 in order to immobilize it from the outside, for example by at least partially enveloping it.

[0096] In figures 5, 7 and 8, the cohesive material 5 can also be introduced into at least one hollow part 6 of a molding element 4 in order to immobilize it by retaining the hollow part 6 filled at least partially by the cohesive material 5.

[0097] Of course, it is possible to consider different ways of arranging the cohesive material 5 between the molding elements 4 which can be combined within the same molding core 1.

[0098] Similarly, the molding elements 4 may have a specific shape or arrangement intended to improve the binding character of the cohesive material 5.

[0099] According to an embodiment of the invention shown in Figures 4, 5 and 6, a molding element 4 has a raised protrusion 7 on a face in contact with the cohesive material 5. The raised protrusion 7 forms a mechanical grip in the cohesive material 5. The shape of the raised protuberance 7 can also be adapted and made more complex in order to aid in the rupture and fragmentation of the cohesive material 5, as shown in [Fig.5].

[0100] Thus, when a mechanical withdrawal force is exerted on the molding element 4 with the aim of extracting it from the molded part 2, the cohesive material 5 is broken and is fragmented into several pieces 5', as shown in [Fig.6], on which molding elements are shown being extracted from the molded part 2.

[0101] According to another embodiment of the invention, as shown in particular in Figures 7 and 8, a molding element 4 has a hollow part 6 on a face in contact with the cohesive material 5 in order to improve the holding of the assembly of the molding element 4 with another molding element 4 by the cohesive material 5.

[0102] When a molding element 4 has a raised protrusion 7, this is also likely to define hollow parts 6 for the molding element 4, as can be seen in particular in figures 4 and 5.

[0103] The recessed portion 6 can be in the form of a simple groove, as shown in [Fig. 8], or in a more complex form. In [Fig. 8], since the core has a round cross-section, the recessed portion 6 can be in the form of an annular groove.

[0104] By way of example, a molding element 4 shown on the left in [Fig.7] has the hollow part 6 in the form of a retention cavity 8, that is to say a cavity 8 whose shape prevents the decoupling of the molding element 4 when the retention cavity 8 is occupied by cohesive material 5.

[0105] By way of example, as shown in [Fig.7], the retention cavity 8 may have an inlet orifice 9 with a smaller diameter than that of a main section of the retention cavity 8.

[0106] According to other examples, the retention cavity 8 can have a moon shape, a zig-zag shape, a spiral shape... that is to say, an undercut shape.

[0107] By way of example, a molding element 4 shown on the right in [Fig.7] has a hollow part 6 in the form of a channel 10. The channel 10 is preferably through-channel, with a first orifice 11 opening onto the face of the molding element 4 in contact with the cohesive material 5 and a second orifice 12 opening towards the outside of the molding core 1. The channel 10 is through-channel and is at least partially occupied by the cohesive material 5.

[0108] In the molding core 1 shown in [Fig.7], the channel 10 communicates with the retention cavity 8, which advantageously allows cohesive material 5 to pass through the channel 10 to enter the retention cavity 8 during the assembly of the molding elements 4.

[0109] The cohesive material 5 is, according to a particular embodiment, metal, a metal alloy, a thermosetting polymer, a thermoplastic polymer, a salt and / or a combination of such compounds.

[0110] The molding elements 4 are, according to a particular embodiment, made of metal. However, not all the molding elements 4 are necessarily made of the same material within the same molding core.

[0111] The molding core 1 according to the invention can be made in several ways. It can, for example, be formed by overmolding the molding elements 4 with cohesive material 5. It can also be formed by injecting the cohesive material 5 between the molding elements 4.

[0112] To illustrate a concrete example of a molding core 1 according to the invention, the molding core 1 intended for molding the undercut hollow parts of a thrust reverser grid for a turbojet nacelle is shown in [Fig. 9]. In [Fig. 9], the cohesive material 5 is shown hatched.

[0113] The invention also relates to a molding method for part 2 having at least one undercut hollow part 3, in which the undercut hollow part 3 of part 2 is obtained by means of a molding core 1 as described above.

[0114] Such a molding process comprises at least: a. an assembly step, during which molding elements 4 are assembled with the cohesive material 5 to create a molding core 1; b. a step in the production of the molded part 2, during which material is added around the molding core 1, while maintaining the integrity of the cohesive material 5 connecting the molding elements 4; c. a stage of rupture, melting, dissolution and / or fragmentation, during which the cohesive matter 5 is broken, melted, dissolved and / or fragmented; and d. a removal step, during which the cohesive material 5 and the molding elements 4 are removed from the molded part 2.

[0115] During the realization step b), the addition of material is preferably carried out by a molding process of the draping type, resin transfer, filament winding, compression or casting type.

[0116] The molded part 2 is preferably made from thermosetting resins, in particular epoxy, polyester, etc., or thermoplastic resins, in particular polyetheretherketone, polyaryletherketone, polyetherimide, etc.

[0117] A further aspect of the invention relates to a molded part 2 having the hollow part 3 in undercut, obtained by the process as described above. previously.

[0118] Unless otherwise specified, the same element appearing on different figures has a unique reference.

Claims

Demands

1. Molding core (1) for molding by draping, resin transfer, filament winding and / or thermocompression of a part (2) having a hollow part (3) of non-demolding shape, characterized in that it is rigid and formed of at least two molding elements (4) and a cohesive material (5), and in that the molding elements (4) are assembled and immobilized together by the cohesive material (5) to form a one-piece molding core (1).

2. Molding core (1) according to claim 1, characterized in that the cohesive material (5) is positioned at the interface of at least two molding elements (4).

3. Molding core (1) according to any one of the preceding claims, characterized in that the cohesive material (5) is a fusible material, capable of having a melting point lower than that of the constituent material of the molding elements (4).

4. Molding core (1) according to any one of the preceding claims, characterized in that the cohesive material (5) is a soluble material, capable of dissolving in the presence of a solvent, in particular not deteriorating the material constituting the molding elements (4).

5. Molding core (1) according to any one of the preceding claims, characterized in that the cohesive material (5) is a fractionable material, capable of breaking apart when it receives an appropriate energy.

6. Molding core (1) according to any one of the preceding claims, characterized in that, on a face in contact with the cohesive material (5), a molding element (4) has a raised element (7) forming a mechanical hook in the cohesive material (5).

7. Molding core (1) according to any one of the preceding claims, characterized in that, on a face in contact with the rigid cohesive material (5), a molding element (4) has a hollow part (6) forming a retention cavity (8) occupied by cohesive material (5).

8. Molding core (1) according to any one of the preceding claims, characterized in that a molding element (4) has a channel (10) having at least a first orifice (11) opening onto a face in contact with the cohesive material (5), and a second orifice (12) opening towards the outside of the molding core (1), the channel (10) being at least partially occupied by the cohesive material (5).

9. A molding process for a part (2) having a hollow portion (3) of non-removable shape, characterized in that it comprises at least: - an assembly step, during which molding elements (4) are assembled with cohesive material (5) to produce a molding core (1) according to any one of the preceding claims; - a step in the production of the molded part (2), during which an addition of molding material around the molding core (1) is carried out by draping, by resin transfer, by filament winding and / or by thermocompression; - a stage of rupture, fusion, dissolution and / or fragmentation, during which the cohesive matter (5) is broken, melted, dissolved and / or fragmented; and - a removal step, during which the cohesive material (5) and the molding elements (4) are removed from the molded part (2).

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