Cluster of wax models and mould for manufacturing a plurality of turbine engine elements by lost-wax casting

Abstract

The invention relates to a cluster of wax models, around which a mould (1) for manufacturing a plurality of bladed elements by lost-wax casting is intended to be formed, the model having a longitudinal axis (X) and comprising: a replica of a casting cup (2), a replica of a central sprue (3), a plurality of replicas of mould elements (4), and a plurality of replicas of source feed ducts (5) of the mould elements (4). According to the invention, each replica of a source feed duct (5) is connected to a replica of a mould element (4) via replicas of fluid communication elements (6a, 6b, 6c).

Description

[0001] DESCRIPTION

[0002] TITLE: CLUSTER OF MODELS MADE IN WAX AND MOULDED FOR THE MANUFACTURE BY LOST WAX CASTING OF A PLURALITY OF TURBOMACHINE ELEMENTS

[0003] Field of invention

[0004] The present invention relates to the field of cluster manufacturing of bladed elements of turbomachines, and more particularly of aircraft turbomachines, by the lost wax casting technique.

[0005] A bladed element refers to both a vane and a blade assembly. Each bladed element can therefore be a sector comprising a plurality of blades, such as a low-pressure distributor sector, or an individual blade such as a compressor or turbine wheel blade.

[0006] The invention relates more particularly to the design of a cluster of models and that of the mold intended to be formed around this partially wax model, mold in which the metal is intended to be cast to obtain the turbomachine elements.

[0007] The invention thus proposes a cluster of models and a mold for obtaining at least one piece of foundry equipment independent of the formed turbomachine elements, as well as an associated manufacturing method by lost wax casting of a plurality of bladed elements.

[0008] The invention relates to all types of aircraft turbomachine, in particular turbojets and turboprops.

[0009] State of the prior art

[0010] The lost wax casting technique for simultaneously manufacturing several bladed elements, i.e. blades or blades, of aircraft turbomachines, such as moving blades, is well known in the prior art. Such a technique is for example described in French patent application FR 3 061 051 A1.

[0011] As a reminder, lost wax precision casting involves creating a wax model of each of the desired bladed elements by injection into tools. The assembly of these models makes it possible to create a cluster, which is then immersed in different substances in order to form a ceramic mold of approximately uniform thickness around it. The cluster is also commonly referred to as a "cluster assembly" or "wax tree," although its components are not necessarily all made of wax or another sacrificial material.

[0012] The process continues by melting the wax, which then leaves its imprint in the ceramic mold, into which the molten metal is poured, via a pouring cup assembled on the metal distributor. After the metal has cooled, the mold is destroyed and the metal pieces are separated and finished.

[0013] This technique offers the advantage of dimensional precision, allowing certain machining operations to be reduced or even eliminated. In addition, it offers a very good surface appearance.

[0014] In the field of lost wax casting, the principle of drop casting, or gravity casting, of molten metal is known, which consists of casting the metal from above into the mold cavities intended to form the turbomachine parts. According to this principle, the molten metal is poured into the cup and then generally reaches an annular system for supplying the plurality of cavities intended to form the turbomachine parts, as described in French patent application FR 2 985 924 A1.

[0015] Furthermore, in the field of lost wax casting, we also know the principle of source casting of the molten metal which consists on the contrary of pouring the metal from below into the mold cavities intended to form the turbomachine parts. Most often, the molten metal is poured into the cup and then specific conduits connected to the cup then allow the injection of the metal from the lower part of the cavities.

[0016] Due to the increase in the need for parts made using this lost wax casting technique, there is a need to increase the production rate of these parts.

[0017] To achieve this, it was considered to increase the size of the cluster without changing the other components so as to allow the production of an additional number of parts while limiting the costs of implementing this increase in size.

[0018] However, it has been noted that such a configuration does not provide a satisfactory result because increasing the size of the cluster without any other change causes metal feed shortages, which creates microporosity defects in the resulting parts. The resulting parts consequently have a relatively high number of breakages and therefore a high reject rate.

[0019] There is therefore a need to optimize the current lost wax casting technique, particularly within the framework of the principle of source casting with a cluster of models. In particular, there is a need to allow both the number of blades manufactured to be increased without degrading the quality of the output parts, i.e. without degrading the metallurgical health of the turbomachine parts produced.

[0020] Statement of the invention

[0021] The invention aims to remedy at least in part the drawbacks mentioned above relating to the techniques of the prior art. To this end, the invention relates to a cluster of models made of wax, around which a mold is intended to be formed for the manufacture by lost wax casting of a plurality of turbomachine elements, the wax being intended to be eliminated by melting and replaced by injected metal, said model having a longitudinal axis X and comprising: a replica of a casting cup capable of allowing the injection of molten metal into the mold; a replica of a central descendant extending along the longitudinal axis X, capable of being in fluid communication with the casting cup to receive the molten metal;a plurality of replicas of mold elements, each intended for obtaining one of the turbomachine elements, each mold element comprising a first upper end portion and a second lower end portion, separated by a middle portion; a plurality of replicas of source supply conduits of the mold elements, capable of being in fluid communication with the central descendant so as to allow source casting of the mold elements.;

[0022] According to the invention, each source supply conduit replica is connected to a mold element replica by means of fluid communication element replicas comprising a first communication element in the upper part, a second communication element in the lower part, and a third communication element in the middle part.

[0023] The invention also makes it possible to carry out source castings, thus protecting fragile cores which would be inserted into the various mold elements so as to form the ducts of the bladed elements.

[0024] The invention also relates to a mold for the manufacture by lost wax casting of a plurality of turbomachine elements, said mold having a longitudinal axis X and comprising: a casting cup capable of allowing the injection of molten metal into the mold; a central descender extending along the longitudinal axis X of the mold, in fluid communication with the casting cup to receive the molten metal; a plurality of mold elements, each intended to obtain one of the turbomachine elements, each mold element comprising a first upper end portion and a second lower end portion separated by a third middle portion; a plurality of conduits for supplying the mold elements with a source, in fluid communication with the central descender so as to allow the mold elements to be cast with a source.

[0025] According to the invention, each source supply conduit is connected to a mold element by means of fluid communication elements comprising a first communication element in the upper part, a second communication element in the lower part, and a third communication element in the middle part.

[0026] Thus, the invention proposes a new and inventive approach making it possible to at least partially resolve the drawbacks of the prior art.

[0027] In particular, and because several communication points are implemented to convey the injected metal from the various source supply conduits to the mold elements, this makes it possible to ensure a filling front of the mold elements both at the bottom, at the top, and in the middle, thus limiting the turbulence of the injected metal flow when it arrives at the location of the mold elements and therefore limiting the stresses applied to the various components during the casting of the metal.

[0028] Such an achievement can thus make it possible to increase the number of bladed elements manufactured without degrading the quality of the output parts, that is to say without degrading the metallurgical health of the turbomachine parts produced.

[0029] As a result, the scrap rate of parts cast in this way is relatively limited, which leads to a reduction in production costs.

[0030] In addition, such a solution makes it possible to ensure a relatively efficient mileage compared to the existing one.

[0031] Finally, such an implementation makes it possible to optimize the footprint, by producing a greater number of parts using a single cluster model and mold, and therefore to optimize production costs.

[0032] According to a particular aspect of at least one embodiment of the invention, the mold comprises a central element with an axis coinciding with the longitudinal axis X of the mold and fixed to the central descender.

[0033] Furthermore, a plurality of radial arms extend from said central element and come into contact with the communication elements at the lower part so that each of said radial arms comes into support of a second lower end part of a separate mold element.

[0034] In this way, the central element allows the different components of the mold to be held and rigidified during metal injection.

[0035] According to a particular aspect of at least one embodiment of the invention, the mold comprises sealing means provided between said central element and said central descender so as to create a mechanical seal during the injection of metal.

[0036] In this way, the central element is isolated from the central descendant due to its watertight mechanical connection to the metal during casting, the central element can therefore ensure its function of holding and stiffening the different components of the mold during metal injection.

[0037] According to a particular aspect of at least one embodiment of the invention, each of the source supply conduits of the mold elements forms an angle of between 10° and 40° with the central descendant. In this case, according to a particular aspect of at least one embodiment of the invention, each of the source supply conduits of the mold elements forms an angle of between 12° and 30° with the central descendant.

[0038] This allows for optimal filling of the mold elements by limiting turbulence during filling.

[0039] According to a particular aspect of at least one embodiment of the invention, the mold comprises between 8 and 32 mold elements, preferably sixteen mold elements, regularly spaced circumferentially around the longitudinal axis X.

[0040] This makes it possible to produce a large number of bladed elements while limiting the costs of implementing the production means because these elements are produced simultaneously.

[0041] According to a particular aspect of at least one embodiment of the invention, the mold elements are turbomachine bladed elements.

[0042] According to a particular aspect of at least one embodiment of the invention, the mold is made of ceramic.

[0043] The invention also relates to a method of manufacturing by lost wax casting a plurality of turbomachine bladed elements, the method being implemented using a mold according to one of the aforementioned embodiments and / or using a cluster-shaped model according to the aforementioned embodiment, the method comprising a step of casting the metal into the mold so as to melt the wax to form at least the turbomachine bladed elements.

[0044] According to a particular aspect of at least one embodiment of the invention, the method further comprises a step of manufacturing a material other than metal, in particular ceramic, so as to form the mold.

[0045] Presentation of figures

[0046] The invention, as well as the various advantages that it presents, will be more easily understood in the light of the following description of an illustrative and non-limiting embodiment thereof, and of the appended drawings among which:

[0047] [Fig. 1] represents a perspective view of a bladed element of a turbomachine intended to be obtained by implementing the method according to the present invention, said bladed element being in the form of a low pressure distributor sector;

[0048] [Fig. 2] represents a perspective view of a mold according to an embodiment of the invention for the manufacture by lost wax casting of a plurality of turbomachine bladed elements, and

[0049] [Fig. 3] represents a detailed perspective view of a mold part according to the embodiment of Figure 2. Description of the embodiments

[0050] Throughout the description, the possible terms “top”, “bottom”, “above” and “below” are understood according to the orientation of the views in the figures.

[0051] With reference to Figure 1, there is shown a low pressure turbine distributor sector 100 for an aircraft turbomachine. This sector comprises a plurality of blades 200 arranged between a first end 400 and a second end 600. The two ends 400, 600 respectively form an outer crown angular sector and an inner crown angular sector, and each comprising a platform 800 delimiting a main gas circulation vein 300. In addition to the platform 800 to which an aerodynamic function is attached, each end also comprises a conventional structure allowing the mounting of this bladed element on the turbomachine module.

[0052] The invention therefore aims to manufacture the distributor sector 100 by a lost wax casting process, using a mold 1 or using a cluster-shaped model made of wax, around which the mold 1 is intended to be formed.

[0053] It should be noted that the choice of the low pressure distributor sector is only one example among others, the invention also making it possible to manufacture other turbomachine elements, which may for example be mobile compressor or turbine blades, or even compressor or turbine stator blades, produced individually or in sectors therefore comprising one or more blades.

[0054] First, in this process, a cluster of models (not shown) is made, also called a replica, around which a mold is formed. This cluster is essentially composed of sacrificial elements made of wax.

[0055] The mold formation step is carried out in a material other than metal, and more particularly in ceramic. This formation step is carried out in a known manner by dipping the wax model in successive baths. After drying, the mold 1 obtained has a general cluster shape, and includes mold elements.

[0056] We now present, in relation to figures 2 and 3, an exemplary embodiment of a mold 1 according to the invention, for the manufacture by lost wax casting of a plurality of turbomachine elements, and in particular for the manufacture of bladed elements.

[0057] In the following description, even if the characteristics mentioned are described in connection with the mold 1, it is understood that they apply in an analogous manner to the cluster-shaped model made of wax, around which the mold 1 is intended to be formed.

[0058] As illustrated in Figure 2, the mold 1 comprises a casting cup 2 which is capable of allowing the injection of molten metal into the mold 1. This casting cup 2 has a revolutionary conical shape, with a central axis X, therefore coinciding with the central axis of the entire mold 1.

[0059] It also has a peripheral rim 21 provided on the outer circumference.

[0060] The mold 1 also comprises a central descender 3 extending along the longitudinal axis X of the mold. This central descender 3 is arranged in fluid communication with the pouring cup 2 to receive the molten metal.

[0061] In this embodiment, the central descendant 3 takes the form of a hollow cylinder so that the injected metal can pass through it.

[0062] The mold 1 also comprises a plurality of mold elements 4, each of which is intended to obtain one of the turbomachine elements.

[0063] Depending on the embodiments, the mold comprises between 8 and 32 mold elements.

[0064] In the illustrated embodiment, the mold 1 comprises sixteen mold elements 4, regularly spaced circumferentially around the longitudinal axis X.

[0065] These mold elements 4 each comprise a first upper end portion 4a and a second lower end portion 4b separated by a third middle portion 4c.

[0066] In order to connect the mold elements 4 to the central descender 3, the mold 1 comprises a plurality of source feed conduits 5 of the mold elements 4, which are formed in fluid communication with the central descender 3 so as to allow source casting of the mold elements 4.

[0067] Thus the metal is poured from below into the mold elements. The molten metal is poured into the pouring cup 2 to be conveyed to the mold elements 4 via the central chute 3 and then the source feed pipes 5.

[0068] To do this, each source supply conduit 5 is connected to a separate mold element 4 by means of fluid communication elements comprising a first fluid communication element 6a in the upper part, a second fluid communication element 6b in the lower part, and a third fluid communication element 6c in the middle part.

[0069] In other words, for each of the mold elements 4, the first fluid communication element 6a connects the source supply conduit 5 to the upper part 4a of the mold element 4, while the second fluid communication element 6b connects the source supply conduit 5 to the lower part 4b of the mold element 4, and the third fluid communication element 6c connects the source supply conduit 5 to the middle part 4c of the mold element 4.

[0070] Therefore, with these three communication points implemented between the source supply conduit 5 and the mold elements 4 to convey the injected metal, a filling front of the mold elements is ensured first at the bottom, then in the middle, and finally at the top, thus limiting the turbulence of the injected metal flow when it arrives at the location of the mold elements and therefore limiting the stresses applied to the various components during the casting or injection of the metal. More particularly, with these three communication points implemented between the source supply conduit 5 and the mold elements 4 to convey the injected metal, the areas where the flow speed of the injected metal is greater than 1 m / s, corresponding to the factor making the elements fragile and therefore making them susceptible to breakage, prove to be relatively reduced or even eliminated.

[0071] In addition, this allows the quality of the parts to be maintained during cooling and solidification which is satisfactory.

[0072] Furthermore, and due to the reduction in scrap and therefore in metal waste, such a solution makes it possible to obtain a gain in terms of the material used and therefore in the cost price.

[0073] Such a solution also allows for better betting per mile.

[0074] According to the invention, and similarly, the cluster of models made of wax comprises: a replica of a casting cup; a replica of a central descendant extending along the longitudinal axis; a plurality of replicas of mold elements; a plurality of replicas of conduits for supplying the mold elements with a source, capable of being in fluid communication with the central descendant so as to allow the mold elements to be cast with a source,

[0075] Here, and according to the invention, each of the source supply conduit replicas is connected to a mold element replica by means of fluid communication element replicas comprising a first communication element in the upper part, a second communication element in the lower part, and a third communication element in the middle part.

[0076] As more particularly visible in figure 3, the mold also comprises a central element 7 with an axis coinciding with the longitudinal axis X of the mold 1 and fixed to the central descender 3.

[0077] More particularly, the central element 7 is arranged in the continuity of the central descender 3 and also takes the form of a cylinder extending along the longitudinal axis X.

[0078] Furthermore, and as visible, a plurality of radial arms 8 extend from this central element 7 and come into contact with the second fluid communication elements 6b in the lower part so that each of the radial arms supports a second lower end part 4b of a separate mold element 4.

[0079] In this way, this plurality of radial arms forms a base on which the mold elements rest while awaiting metal injection.

[0080] In other words, the central element 7 and the radial arms 8 make it possible to maintain and stiffen the mold elements, the source supply conduits, and the central descender. So that these base-forming elements are sealed during the injection of the metal, the mold further comprises sealing means arranged between the central element 7 and the central descender 3.

[0081] These sealing means may, for example, include ceramic plugs which would be inserted between the central element and the central descender.

[0082] It is also possible to provide for the implementation of sealing means between the radial arms and the second lower end parts 4b of the mold elements 4.

[0083] Likewise, these sealing means between the radial arms and the second lower end parts 4b of the mold elements 4 may for example comprise ceramic plugs which would be inserted between the central element and the central descender.

[0084] Furthermore, and in order to obtain optimal filling of the mold elements by limiting turbulence during filling, each of the source supply conduits 5 of the mold elements 4 forms an angle of between 10° and 40° with the central descender 3, and more particularly in this embodiment between 12° and 30°.

[0085] The illustrated embodiment not being limiting, the invention is not limited to the exemplary embodiment described above.

[0086] For example, an embodiment could be provided in which each of the source feed conduits forms an angle of 50° to 90° with the central descender to feed the mold. In this feeding mode, achieving a filling that is free from metallurgical defects, for example in areas of thin thickness, requires seeking to clog the elements upstream of the mold as early as possible. Such clogging as early as possible can, for example, be obtained for angles of 60° to 85° between each of the source feed conduits and the central descender.

[0087] A specific need could also require an angle less than 10°, in which case the filling of the source supply conduit is carried out as in a standard case of equiaxed cluster filling.

[0088] For example, according to alternative embodiments of the invention, the principle described above can obviously be applied to any other type of cluster configuration which would be adaptable.

[0089] The use of any suitable material other than wax and ceramic could also be envisaged for the process steps associated with these materials.

Claims

CLAIMS 1. Cluster of models made of wax, around which a mold (1) is intended to be formed for the manufacture by lost wax casting of a plurality of bladed elements, the wax being intended to be eliminated by melting and replaced by injected metal, said model having a longitudinal axis (X) and comprising: a replica of a casting cup (2) capable of allowing the casting of molten metal into the mold (1); a replica of a central descender (3) extending along the longitudinal axis (X), capable of being in fluid communication with the casting cup (2) to receive the molten metal; a plurality of replicas of mold elements (4), each intended to obtain one of the turbomachine elements, each mold element (4) comprising a first upper end portion (4a) and a second lower end portion (4b), separated by a middle portion (4c);a plurality of replicas of source supply conduits (5) of the mold elements (4), capable of being in fluid communication with the central descendant (3) so as to allow source casting of the mold elements (4), characterized in that each replica of source supply conduit (5) is connected to a replica of mold element (4) by means of replicas of fluid communication elements (6a, 6b, 6c) comprising a first communication element in the upper part (6a), a second communication element in the lower part (6b), and a third communication element in the middle part (6c).; 2. Mold (1) for the manufacture by lost wax casting of a plurality of turbomachine elements, said cluster-shaped mold having a longitudinal axis (X) and comprising: a casting cup (2) capable of allowing the casting of molten metal into the mold (1); a central descender (3) extending along the longitudinal axis (X) of the mold (1), in fluid communication with the casting cup (2) to receive the molten metal; a plurality of mold elements (4) each intended to obtain one of the turbomachine elements, each mold element (4) comprising a first upper end portion (4a) and a second lower end portion (4b) separated by a third middle portion (4c); a plurality of source supply conduits (5) for the mold elements (4), in fluid communication with the central descender (3) so as to allow source casting of the mold elements (4), characterized in that each source supply conduit (5) is connected to a mold element (4) by means of fluid communication elements (6a, 6b, 6c) comprising a first communication element in the upper part (6a), a second communication element in the lower part (6b), and a third communication element in the middle part (6c). . Mold according to claim 2, characterized in that it comprises a central element (7) with an axis coinciding with the longitudinal axis (X) of the mold (1) and fixed to the central descender (3), and in that a plurality of radial arms (8) extend from said central element (7) and come into contact with said communication elements in the lower part (6b) so that each of said radial arms supports a second lower end part (4b) of a separate mold element (4). .Mold according to claim 3, characterized in that it comprises sealing means arranged between said central element (7) and said central descender (3) so as to create a mechanical seal during the casting of metal. . Mold according to one of claims 2 to 4, characterized in that each of the source supply conduits (5) of the mold elements (4) forms an angle of between 10° and 40° with the central descender (3). . Mold according to one of claims 2 to 5, characterized in that it comprises between 8 and 32 mold elements (4), preferably sixteen mold elements (4), regularly spaced circumferentially around the longitudinal axis (X). . Mold according to one of claims 2 to 6, characterized in that the mold elements (4) are turbomachine bladed elements. . Mold according to one of claims 2 to 7, characterized in that it is made of ceramic. .Method of manufacturing by lost wax casting a plurality of turbomachine bladed elements, characterized in that it is implemented using a mold (1) according to any one of claims 2 to 8 and / or using a cluster of models according to claim 1, the method comprising a step of casting the metal into the mold (1) so as to melt the wax to form at least the turbomachine bladed elements.

10. Method according to the preceding claim, characterized in that it further comprises a step of manufacturing a material other than metal, in particular ceramic, so as to form the mold (1).

Images