Method for producing hybrid moulds for parts made of composite materials and hybrid mould obtained

Abstract

The present invention relates to a method for producing moulds for parts made of composite materials, which makes a mould (1) formed by a mould base (2) that is made by additive manufacturing and in which a mould surface (2.1) that serves as a model to form a mould bed (3) is machined. Once the mould bed (3) and the mould base (2) are made, they are attached to each other by means of joint connectors (5, 6), which define a floating assembly arrangement that absorbs the differences in expansion of both parts making up the mould, which are caused by temperature variations.

Description

[0001]

[0002] MANUFACTURING PROCEDURE FOR HYBRID MOLDS FOR COMPOSITE MATERIAL PARTS AND HYBRID MOLD OBTAINED

[0003] TECHNICAL SECTOR

[0004] The present invention relates to the manufacture of molds for parts formed from composite materials, proposing a process that allows for the efficient manufacture of molds composed of multiple materials with different coefficients of thermal expansion.

[0005] BACKGROUND OF THE INVENTION

[0006] The manufacturing of composite parts relies, in most applications today, on the use of curing molds. Composite materials, consisting of a reinforcement and a matrix, typically incorporate polymer matrices that must be cured in a thermal process. This process is carried out once the material is positioned on a mold, so that the resulting part replicates the geometry of that mold.

[0007] However, these molds for composite parts must meet a series of requirements, primarily structural, geometric, porosity, and temperature. Since curing temperatures can be high, especially for resins with high mechanical properties, the molds must withstand thermal cycles while maintaining tightly controlled geometries so that the molded parts meet the desired specifications.

[0008] Furthermore, applications requiring high-property resins are primarily found in the aeronautical sector, where the dimensions of the manufactured parts are also large, so the influence of expansion coefficients is more noticeable.

[0009] Therefore, to manufacture these composite parts, molds made of special steels, such as Invar steel, with a very low coefficient of expansion, are typically used. Molds are also made of continuous carbon fiber composite material. This allows the mold's coefficient of expansion to approximate that of the parts to be manufactured, simplifying the calculation and the process. However, the manufacture of these molds involves complex processes, long lead times, and significant costs, while the manufacture of composite molds also requires the production of a model.

[0010] There are currently options for manufacturing molds using faster and more efficient processes, such as additive manufacturing. However, the materials used in this technology and the configuration of the parts to be manufactured result in parts with a much higher thermal cycle deformation than traditional materials such as Invar steel or continuous carbon fiber composites, making it difficult to achieve results within the geometric tolerances allowed in high-property resin curing processes. There are also references, such as document US10427330, for making molds made from multiple materials, but using special materials with low coefficients of expansion, with which improvements in mold manufacturing processes are very limited.

[0011] One solution to these problems is the use of different materials within the same mold, which can generate a simpler mold structure based on materials with worse but more efficient properties, combined with a mold bed surface with better thermal expansion properties that can slide relative to the mold support structure. In this regard, document AT503547 describes a solution that solves the expansion problem by means of a mold composed of a metal base and a mold bed made of a different material. The mold bed, where the material for the part to be manufactured is deposited, is made of a composite material reinforced with glass or carbon fiber, while the base, on which the mold skin rests, is a metal structure that provides stability, with the mold surface being fixed to the base by means of threaded rods that compensate for possible geometric deviations.This document does not describe the mold bed manufacturing process, so it is understood that it is formed according to a traditional model manufacturing process for mold manufacturing.

[0012] In view of the aforementioned disadvantages of current solutions, a solution with an efficient multi-material mold manufacturing process that ensures optimal dimensional performance in the production of composite material parts is considered necessary.

[0013] EXPLANATION OF THE INVENTION

[0014] In order to achieve this objective and solve the technical problems discussed so far, as well as providing additional advantages that may arise later, the present invention relates to a method for manufacturing molds for parts made of composite materials, which comprises the following steps:

[0015] - manufacturing of a mold base by additive manufacturing with a molding surface with the geometry of the part to be manufactured,

[0016] - machining of the molding surface of the mold base,

[0017] - manufacturing, on the machined moulding surface, of a mould bed by lamination in composite material,

[0018] - machining on the mold bed of some housings,

[0019] - removal of the mold bed from the mold base, and machining of housings in said mold base,

[0020] - incorporation of the mold bed by fixing, in the housings of the mold base or in the housings of the mold bed, some connectors for joining the mold base and the mold bed, at least one of the connectors being a fixed connector configured for connecting the mold base and the mold bed without the possibility of movement between both, being able to allow relative rotation between them, and the rest of the connectors being mobile connectors configured to allow relative movement between the mold base and the mold bed in one or two directions and / or a rotation, generating a flexible connection between the mold bed and the mold base.

[0021] A composite mold bed ensures thermal behavior that is as similar as possible to the part itself, thereby reducing problems caused by expansion. This composite material can be carbon fiber, fiberglass, or other reinforcing fibers, preferably in a continuous fiber configuration. Thermosetting resins capable of withstanding high temperatures are also preferred, although other options can be implemented.

[0022] Furthermore, the connecting connectors allow for the absorption of different thermal expansions due to temperature variations between the mold bed where the part is manufactured and the mold base, without generating deformations that affect the geometry or structural loads of the part to be manufactured. Preferably, the connecting connectors can be located either inside or outside the surface of the part, depending on the specific needs of the mold and / or the geometry of the part to be manufactured. These connecting connectors will allow the connection between the mold base and the mold bed without affecting the tightness necessary for its functionality as a mold.

[0023] Furthermore, by manufacturing the mold bed on the mold base, the need for additional models for the manufacture of said bed is avoided.

[0024] By manufacturing mold bases using additive manufacturing, mold bases for creating geometries can be produced more quickly and more efficiently. The mold base is preferably based on thermoplastic resins, including PES11, PEI, PPE / PS, PPO, ABS, PA, PC, PC / PBT, PET, and PA, preferably reinforced with carbon fiber or short-form fiberglass.

[0025] The machining of the base is expected to include roughing, refining, and thermal stabilization processes to serve as a mold for manufacturing a mold bed. This machining leaves the mold base ready to serve as a template for manufacturing the mold bed.

[0026] Preferably, after machining the mold base, a surface treatment is applied to the machined surface of the mold base to facilitate demolding from the mold bed after manufacturing. This treatment results in a surface finish with improved characteristics for the part.

[0027] According to a feature of the invention, in the manufacture of the mold bed, the composite material is applied by manual or automatic means, and subsequently cured, prior to its removal.

[0028] According to another characteristic of the invention, the mold bed is manufactured with an oversize, and prior to its removal from the mold base, surface machining and trimming of the same is carried out on the surface of said mold bed.

[0029] Thanks to this configuration, the mold bed will be provided with the necessary exterior and surface geometry to be used later as a curing surface for the parts for which the mold was designed.

[0030] According to another feature of the invention, additional machining is performed on the mold base to incorporate seals and vacuum inlets that allow the mold bed to be properly secured to the mold base. This configuration allows for flexible positioning and securing of the mold bed, thus facilitating the machining and trimming processes indicated above, converting the mold base into a machining tool.

[0031] Preferably, the joint connectors are configured to allow a geometric fit between the mold bed and the mold base. This allows for adjustment based on the tolerances required for each part. In addition, additional manufacturing benefits are achieved, such as the ability to compensate for springback.

[0032] Additionally, subsequent machining operations can be performed to adapt the mold to new requirements after use. This increases the mold's versatility, allowing it to manufacture multiple parts, each with different characteristics.

[0033] Finally, according to another aspect, the invention also contemplates a mold for manufacturing parts in composite materials, obtainable according to a manufacturing process in accordance with the characteristics described above, which comprises a mold base made by additive manufacturing, a mold bed made of composite material, and said mold bed arranged on the mold base with joining connectors that allow relative movement between both component parts of the mold to absorb differences in thermal expansion during the mold process of the part.

[0034] BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 shows an exploded perspective view of the component assembly of a mold made according to the manufacturing process object of the invention.

[0036] Figure 2 is a perspective view of the raw mold base produced by additive manufacturing in the manufacturing process of the invention. Figure 3 is a perspective view showing the machining performed in the process of the invention to configure the mold base as a model for manufacturing the mold bed that is part of the mold for producing the parts to be obtained.

[0037] Figure 4 is a perspective showing the mold bed on the mold base once completed.

[0038] Figure 5 is a perspective view of the mold base with a machining tool.

[0039] Figure 6 is a perspective view of the mold bed with the housings for the joining connectors machined.

[0040] Figure 7 is a perspective view of the mold base with the housings for the joining connectors machined.

[0041] Figure 8 is a perspective view of the mold base with the joining connectors fixed in the housings of said mold base.

[0042] Figure 9 is a perspective view of the mold base with the mold bed on the mold base and with the connectors already attached.

[0043] Figure 10 is a sectional view through the midpoint of the mold housings after the manufacturing process has been completed, with the mold bed connected to the mold base with the joining connectors.

[0044] Figure 11 is an exploded view of an embodiment of a mobile joint connector.

[0045] Figure 12 is a sectional view of the movable joint connector of Figure 11 when assembled.

[0046] PREFERRED EMBODIMENT OF THE INVENTION

[0047] The object of the invention relates to a method for manufacturing molds for molding parts formed from composite materials, allowing said molds to be made in an efficient manner with a multi-material composition.

[0048] The multi-material mold (1) that is manufactured with this method of the invention comprises, as can be seen in Figure 1, a mold base (2), a mold bed (3) and joining connectors (5, 6) with which the mold base (2) and the mold bed (3) are fixed together, determining an assembly that allows thermal expansions between the component parts of the mold (1) joined together, without generating tensions and where the contact surface with the pieces to be molded, configured by the mold bed (3), can have a thermal behavior close to that of the pieces being molded, such that with the molds thus made, pieces of composite materials can be manufactured without significant geometric variations with respect to the expected specifications.

[0049] The process for manufacturing said molds comprises, firstly, as can be seen in Figure 2, the manufacturing of the mold base (2) by means of additive manufacturing, to obtain said mold base (2) according to a blank piece.

[0050] After obtaining the blank of the mold base (2), a machining of molding surface (2.1) conformation is carried out on that piece, for example, by roughing, refining and thermal stabilization, so that the same mold base (2) serves as a manufacturing model of the mold bed (3). Preferably, in addition, surface treatments are applied to the machined molding surface (2.1), to facilitate the demolding of the mold bed (3) with a suitable surface finish, as can be seen in figure 3.

[0051] Once the mold base (2) has been made in the indicated manner, the mold bed (3) is manufactured, preferably in composite material reinforced with continuous fiber, glass or carbon, and preferably using thermosetting resins such as epoxy, phenolic, vinyl esters, bismaleimides, or others; but also with the possibility of using advanced thermoplastic resins such as PEEK, PAEK, PEI, or others. The manufacture of the mold bed (3) is carried out by molding the material on the machined molding surface (2.1) of the mold base (2), with subsequent curing. Prepreg materials or materials in dry format can be used, requiring in the case of dry materials a resin injection or infusion process prior to curing. A mold bed (3) is then obtained on the mold base (2) as can be seen in Figure 4.After curing of the molded mold bed (3), the mold bed (3) can optionally be removed and machining performed on the mold base (2) to give it capabilities for use as a machining tool, as can be seen in figure 5. Thus, if necessary, surface machining and trimming will be performed on the surface of said mold bed (3) that will provide the mold bed with the exterior and surface geometry necessary to be used later as a curing surface for the pieces to be manufactured by means of the mold (1). Optionally, slot machining will be performed on said mold base (2) for vacuum distribution, as well as for the placement of sealing gaskets and vacuum inlets to facilitate the machining and trimming process.

[0052] According to figure 6, the machining of some housings (4.2) necessary to place the joining elements (5, 6) for mounting the mold (1) will then be carried out on the mold bed (3), and after removing the mold bed, as shown in figure 7, the machining of the housings (4.1) on the mold base (2) will be carried out.

[0053] As can be seen in figure 8, the joining connectors (5, 6) will subsequently be placed in the housings (4.1) of the mold base (2).

[0054] The mold bed (3) will then be fixed with the joining connectors (5, 6) to the mold base (2) to form the mold (1) as can be seen in Figure 9.

[0055] The joining connectors for the relative fixing between the mold bed (3) and the mold base (2), can be fixed connectors (5) or mobile connectors (6), depending on the specific configuration of the geometry of the pieces to be manufactured with the mold (1), said joining connectors being able to allow a geometric adjustment of the component parts of the mold (1), to obtain additional benefits in the use of the mold, such as the compensation of the elastic return. Within the mobile connectors (6), depending on the geometry of the piece, connectors will be used that allow movement in one or several directions, allowing both in the case of fixed connectors (5) and mobile connectors (6) the relative rotation.

[0056] The joining connectors (5, 6) can be fixed, as is the case of the fixed connector (5) shown in Figures 8 and 9, such that at that point the mold base (2) and the mold bed (3) are fixed without the possibility of relative movement between them, but they can rotate, or they can be mobile connectors (6), with the capacity to slide and / or rotate in one or several directions. In the practical example shown in the figures, the mobile connector (6) has the configuration shown in more detail in Figures 11 and 12, said mobile connector (6) having a sliding channel (6.1) in the form of a slot, which determines a flexible arrangement that allows absorbing different thermal expansions of the mold bed (2) and the mold base (1) in said direction, without generating deformations that affect the structural geometry between both parts (2, 3).

[0057] In the case shown, the fixing of the joining elements (5, 6) is carried out on the mould base (2) to complete the fixing with the mould bed (3), however, it is contemplated that it can be carried out in the opposite way by fixing the joining elements (5, 6) to the mould bed (3) depending on the requirements of the piece to be manufactured. In figure 10 of the section of the mould (1) the relative arrangement between the mould bed (3) and the mould base (2) can be seen.

[0058] The example shown in the figures is an example of a practical embodiment, however it will be evident to those skilled in the art that it is not a limiting example and may have different configurations as long as it does not affect the scope defined by the claims.

Claims

CLAIMS 1.- Procedure for manufacturing moulds (1) for parts made of composite materials, which comprises the following stages: - manufacturing of a mold base (2) by additive manufacturing with a molding surface (2.1) with the geometry of the part to be manufactured, - machining of the molding surface (2.1) of the mold base (2), - manufacturing, on the machined moulding surface (2.1), of a mould bed (3) by lamination in composite material, - machining in the mould bed (3) of some housings (4.2), - removal of the mold bed (3) from the mold base (2), and machining in said mold base (2) of housings (4.1), - incorporation of the mold bed (3) by fixing, in the housings (4.1) of the mold base (2) or in the housings (4.2) of the mold bed, some connectors for joining the mold base (2) and the mold bed (3), at least one of the connectors being a fixed connector (5) configured for connecting the mold base (2) and the mold bed (3) without the possibility of movement between the two but with the possibility of rotation, and the rest of the connectors being mobile connectors (6) configured to allow relative movement between the mold base (2) and the mold bed (3) in one or two directions and / or a rotation, generating a sliding connection between the mold bed (3) and the mold base (2). 2.- Method for manufacturing molds (1) according to the first claim, in which surface treatments are applied to the machined surface (2.1) in the mold base (2) to facilitate demolding from the mold bed (3). 3.- Method for manufacturing molds (1) according to any one of the preceding claims, where in the manufacture of the mold bed (3) the composite material is applied by manual or automatic means, and subsequently cured, prior to its removal. 4.- Method for manufacturing molds (1) according to any one of the preceding claims, wherein the mold bed (3) is manufactured with an oversize, and prior to its removal from the mold base (2), surface machining and trimming are carried out on the surface of said mold bed (3). 5.- Mold manufacturing procedure (1) according to the previous claim, where machining is carried out on the mold base (2) to incorporate joints and vacuum inlets that allow the correct fastening of the mold bed (3) on the mold base (2) during the surface machining and trimming process. 6.- Method for manufacturing molds (1) according to any one of the preceding claims, wherein the joining connectors (5, 6) are configured to allow a geometric adjustment between the mold bed (3) and the mold base (2) at different levels of thermal expansion between them. 7.- Method for manufacturing molds (1) according to any one of the preceding claims, where successive machining operations are carried out to adapt the mold to the new requirements after its use. 8.- Mold (1) for manufacturing parts in composite materials obtainable according to a manufacturing process according to any one of the preceding claims, comprising a mold base (2) made by additive manufacturing, a mold bed (3) made of composite material, and said mold bed (3) arranged on the mold base (2) with joining connectors (5, 6) that allow relative movement between both component parts of the mold (1) to absorb the differences in thermal expansion during the molding process of the part.

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