Method for creating a nonpermanent model

Abstract

The invention provides a method of assembling together a first core (12) and a second core (14) in order to make a non-permanent model configured for use in lost wax molding to form a part having a first cavity and a second cavity corresponding respectively to the first core and to the second core. The invention is characterized by the fact that the first and second cores (12, 14) are assembled together with a first spacer (20), the first spacer (20) being arranged between the first and second cores.

Claims

1. A method of assembling together a first core and a second core in order to make a non-permanent model configured for use in lost wax molding to form a part having a first cavity and a second cavity corresponding respectively to the first core and to the second core, wherein the first and second cores are assembled together with a first spacer, the first spacer being arranged between the first and second cores, wherein the first and second cores are separated by a first distance, wherein the first spacer presents a thickness less than the first distance, so as to define a first gap between the first spacer and one of the first or second cores, and wherein the first gap is dimensioned in such a manner as to prevent wax from penetrating into a space defined between the first and second cores while wax is being injected.

2. The method according to claim 1, wherein the first spacer includes a meltable material.

3. The method according to claim 1, wherein the first gap is dimensioned as a function of a viscosity of wax used for making the non-permanent model.

4. The method according to claim 1, wherein the gap between the first spacer and one of the first or second cores lies in the range 0.01 mm to 0.35 mm.

5. The method according to claim 1, further comprising a step in which the first spacer is fixed on one of the first or second cores.

6. The method according to claim 1, wherein the gap between the first spacer and one of the first or second cores lies in the range 0.03 mm to 0.30 mm.

7. The method according to claim 1, wherein the gap between the first spacer and one of the first or second cores lies in the range 0.05 mm to 0.25 mm.

8. The method according to claim 1, wherein the first spacer includes wax.

9. The method according to claim 1, wherein the first spacer is fixed on one of the first or second cores.

10. The method according to claim 9, wherein the first spacer is fixed to the one of the first or second cores via complementary shapes.

11. The method according to claim 1, wherein one or more of the first or second cores includes at least one complex surface.

12. The method according to claim 11, wherein the first spacer includes one or more of a cavity, an orifice, or a protuberance that, in each case, has a shape complementary to at least a portion of the at least one complex surface.

13. A method of assembling together a first core and a second core in order to make a non-permanent model configured for use in lost wax molding to form a part having a first cavity and a second cavity corresponding respectively to the first core and to the second core, wherein the first and second cores are assembled together with a first spacer, the first spacer being arranged between the first and second cores, wherein the first spacer includes a first spacer element arranged between the first and second cores and configured to maintain the position of the first spacer relative to the first and second cores, and wherein the first spacer element includes a first housing configured to receive the second core.

14. The method according to claim 13, wherein the first spacer element is arranged between the first core and the second core so as to present at least a first point of contact with the first core.

15. A method of assembling together a first core and a second core in order to make a non-permanent model configured for use in lost wax molding to form a part having a first cavity and a second cavity corresponding respectively to the first core and to the second core, wherein the first and second cores are assembled together with a first spacer, the first spacer being arranged between the first and second cores, wherein the method further includes a step of assembling a third core and a second spacer with the first and second cores, the second spacer being arranged between the first and third cores, and wherein the second spacer has a second spacer element, the first and second spacer elements being configured to be assembled together in an out-of-part zone.

16. The method according to claim 15, wherein the first and second spacer elements are configured for being assembled together by complementary shapes.

17. The method according to claim 15, wherein the first and second spacer elements are configured so as to be fixed relative to each other in at least one direction.

18. The method according to claim 15, wherein the first and second spacer elements are fixed to each other.

19. The method according to claim 15, wherein the second spacer element includes a second housing configured to receive the third core.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention and its advantages can be better understood on reading the following detailed description of various embodiments of the invention given as nonlimiting examples. The description makes reference to the sheets of accompanying figures, in which:

(2) FIG. 1 is a diagram showing a step of injecting wax in order to make a non-permanent model in the prior art;

(3) FIGS. 2A, 2B, and 2C are diagrams showing the various steps of a method of fabricating a non-permanent model in a first embodiment of the present invention;

(4) FIG. 3 is a diagram showing a detail of how the first and second cores are assembled by means of the first spacer in the first embodiment of the present invention;

(5) FIGS. 4A and 4B are diagrams showing how the first and second cores are assembled in a second embodiment of the present invention; and

(6) FIG. 5 is a diagram showing a detail of how the first and second spacer elements are assembled in the second embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

(7) FIG. 1 is a diagram showing how a non-permanent model is made in the prior art for use in a lost wax casting or molding process in order to fabricate a part that presents first, second, and third cavities. To do this, use is made of first, second, and third cores 12, 14, and 16, e.g. made of ceramic type material.

(8) With reference to the arrangement of the corresponding cavities in the blade that is to be formed from the non-permanent model made by the assembly of the first, second, and third cores 12, 14, and 16, those cores may be referred to respectively as the central core, the suction side core, and the pressure side core.

(9) In the known prior art method, the first, second, and third cores 12, 14, and 16 are assembled to one another prior to being arranged in a wax injection mold 100.

(10) In order for it to be possible to assemble the cores without impacting the cooling circuit that is to be present inside the resulting part at the end of the lost wax casting process, the cores 12, 14, and 16 are assembled to one another in out-of-part zones, i.e. in the zones that are eliminated from the final blade.

(11) As shown in FIG. 1, while wax 10 is being injected into the wax injection mold 100, with the injection usually being performed at high pressure, large forces, as symbolized by horizontal arrows in FIG. 1, become applied between the cores 12, 14, and 16 in such a manner that the distances between the various cores run the risk of being modified; during this high-pressure injection and as a result of these large forces, there is also a risk of the cores 12, 14, and 16 being degraded or even broken.

(12) FIGS. 2A, 2B, and 2C are diagrams showing the various steps of a method of fabricating a non-permanent model in a first embodiment of the present invention.

(13) As shown in FIG. 2A, the first, second, and third cores 12, 14, and 16 are arranged in such a manner that a first distance d1 lies between the first and second cores 12 and 14, and a second distance d2 lies between the first and third cores 12 and 16.

(14) In the method of the present invention, first and second spacers 20 and 22 are provided which have dimensions enabling them to be placed respectively between the first and second cores 12 and 14, and between the first and third cores 12 and 16.

(15) For reasons of clarity, FIG. 2A shows the assembly of the first, second, and third cores 12, 14, and 16 prior to putting the first and second spacers 20 and 22 into place, so as to show the distances d1 and d2 between the cores. The method of the present invention is naturally not restricted to assembling the spacers 20 and 22 after the cores 12, 14, and 16 have been assembled together, and it also covers simultaneously assembling together all or some of the cores 12, 14, and 16 with all or some of the spacers 20 and 22.

(16) For example, and in nonlimiting manner, the first and second spacers 20 and 22, and also the first and second spacer elements 24 and 26 of the first and second spacers 20 and 22 (which elements are described below with reference to the second embodiment of the method of the present invention) are made of a meltable material such as wax, resin, polymer, . . . . By way of example, the first and second spacers 20 and 22 may be formed using an injection method or a method of the additive manufacturing type.

(17) The term meltable material is used to mean a material that is meltable in the temperature ranges used for making a shell around the non-permanent model.

(18) The meltable material forming the first spacer is configured to melt in a temperature range from 50 C. to 90 C., preferably from 55 C. to 80 C., and more preferably from 60 C. to 70 C.

(19) The first spacer is configured to be eliminated during the de-waxing step.

(20) In order to facilitate manipulating the first and second spacers 20 and 22, they may also be formed using a wax that presents advantageous flexibility properties.

(21) By way of example and in nonlimiting manner, the first and second spacers 20 and 22 are in the shape of plates presenting respective first and second widths e1 and e2. In this example, the plates are curved. The term in the shape of plates is used herein to mean shapes of thicknesses that are small relative to their lengths or their widths.

(22) As shown in FIG. 3, the first spacer 20 is of dimensions such that its thickness e1 is less than the first distance d1 between the first and second cores 12 and 14; in other words, the first spacer 20 is of dimensions such that gap j1 is formed between the first spacer 20 and one of the first and second cores 12 and 14, specifically the second core 14, when the first spacer 20 is placed between said cores 12 and 14.

(23) The gap between the first spacer and one of the first and second cores lies in the range of 0.01 mm to 0.35 mm, preferably in the range of 0.03 mm to 0.30 mm, preferably in the range of 0.05 mm to 0.25 mm.

(24) The characteristics that apply to the first gap j1 between the first and second cores 12 and 14 also apply to second gap between the first and third cores 12 and 16.

(25) The second gap is formed between the second spacer 22 and one of the first and third cores 12 and 16, specifically between the second spacer 22 and the third core 16.

(26) The presence of such gaps serves to ensure that inserting the first and second spacers 20 and 22 between the corresponding cores does not constrain the relative position of said cores.

(27) By way of example and in nonlimiting manner, the first and second spacers 20 and 22 are fixed by adhesive or by any other fixing method to one of the spacers between which they are arranged; specifically, the first and second spacers 20 and 22 are both fixed to the first core 12.

(28) The first and second spacers 20, 22 may also be fixed to the first core 12 by complementary shapes.

(29) By way of example, the first core 12 has a surface that is complex. The first core 12 may include at least one cavity, at least one orifice, or indeed at least one protuberance, and the second spacer 20 may include at least one cavity, at least one orifice, and/or at least one protuberance of shape that is complementary to at least a portion of the surface of the first and/or second core.

(30) As shown in FIG. 3, the assembly comprising the cores 12, 14, and 16 together with the spacers 20 and 22 is then placed in the wax injection mold 100, into which wax 10 is injected, generally under high pressure, in order to form the non-permanent model.

(31) As can be seen in FIG. 2C, the first and second gaps j1 and j2 are given dimensions such that the wax 10, given in particular its viscosity, is prevented from penetrating into the spaces formed either between the second spacer 20 and the second core 14, or else between the second spacer 22 and the third core 16.

(32) The dimensions of the first and second gaps are determined as a function of the viscosity of the wax used for making the non-permanent model so as to prevent wax from penetrating into said space while wax is being injected.

(33) By way of example, the viscosity of a conventional wax used in lost wax molding processes is 15 Pa.Math.s for the wax at a temperature of 70 C.

(34) Thus, the presence of the first and second spacers 20 and 22 limits any risk of the cores moving relative to one another, and also any risk of said cores deteriorating while the wax 10 is being injected into the wax injection mold 100.

(35) It should be observed that the fact that the above-described gaps are not filled in with wax 10 while the wax 10 is being injected into the wax injection mold 100 does not compromise the integrity and the dimensional accuracy of the part that is to be formed from the non-permanent model, insofar as the metal for forming the part is cast only after the wax 10 has been eliminated, which may be referred to as de-waxing.

(36) It can be understood that the shape and the dimensioning of the first and second spacers 20 and 22 depend on the characteristics of the cavities that are to be formed in the part that is to be made, and more particularly on the way they are arranged relative to one another, and consequently on the characteristics of the cores 12, 14, and 16 between which the spacers are configured to be located.

(37) FIGS. 4A and 4B are diagrams showing how the first, second, and third cores 12, 14, and 16 are assembled in the out-of-part zone in an alternative or additional, second embodiment of the present invention.

(38) More particularly, FIGS. 4A and 4B are diagrams showing how a first spacer element 24 of the first spacer 20 and a second spacer element 26 of the second spacer 22 are arranged with the first, second, and third cores 12, 14, and 16.

(39) Unlike FIGS. 2A to 2C, which are section views of the set of cores 12, 14, and 16 in a working zone corresponding to the part that is to be obtained at the end of the lost wax casting or molding process, FIGS. 4A and 4B are diagrams showing section views of the set of first, second, and third cores 12, 14, 16 in an out-of-part zone in which they are fastened to one another.

(40) The first spacer 20 has a first spacer element 24 and the second spacer 22 has a second spacer element 26, which elements are configured to cooperate with each other so as to maintain the respective distances dl and d2 between the first and second cores 12 and 14 and between the first and third cores 12 and 16.

(41) The first and second spacer elements are 24 and 26 are arranged in an out-of-part zone.

(42) Specifically, instead of, or as well as, fixing together the first and second spacer elements 24 and 26 and the first, second, and third cores 12, 14, and 16 in the working zone, it is possible to assemble together the first and second spacer elements 24 and 26 and the first, second, and third cores 12, 14, and 16 in the out-of-part zone.

(43) The first and second spacer elements 24 and 26 are configured for being assembled together by complementary shapes.

(44) The first core 12 has a first out-of-part portion. The first out-of-part portion includes an assembly opening. The assembly opening has first and second bearing edges.

(45) The second and third cores 14 and 16 have respective second out-of-part portions. As shown in FIG. 4A, the method in this second embodiment begins with a step in which the first spacer element 24 is placed against the first bearing edge of an assembly opening in the first out-of-part portion between the first edge and a second bearing edge of the assembly opening of the first core 12. Positioning is ensured by the presence of at least one point of contact between the first spacer element 24 and the first bearing edge of the first core 12. Said at least one point of contact is reached, for example and in nonlimiting manner, when the first spacer element 24 is moved along the direction symbolized by the arrow shown in FIG. 4A. In order to ensure that the positioning of the first spacer element 24 is stable relative to the first core 12, a plurality of points of contact may be reached, which points are arranged on the body of the first core 12 along a direction that extends transversely to the section plane shown diagrammatically in FIGS. 4A and 4B.

(46) Thereafter, in this second embodiment, the method has a step during which the second spacer element 26 of the second spacer 22 is placed between the first spacer element 24 and the second bearing edge of the core 14, e.g. by being moved in the direction symbolized by the arrow shown in FIG. 4B. During this step, the first and second spacer elements are assembled together by complementary shapes. Once assembled, the surfaces in contact with the first and second bearing edges of the first and second spacer elements converge, downwards in FIG. 4B.

(47) As can be seen in FIG. 4B, the second spacer element 26 includes a fixing device 28 that, by way of nonlimiting example, is in the form of a lug configured to cooperate with a flat 30 formed on the first spacer element 24. It can be understood that by fixing the fixing device 28 of the second spacer element 26 against the first spacer element 24, e.g. against its flat 30, relative movement between the first and second spacers 20 and 22 is prevented in the section plane shown diagrammatically in FIGS. 4A and 4B.

(48) In addition, the first and second spacer elements 24 and 26 are blocked relative to each other in a direction substantially perpendicular to the section plane shown diagrammatically in FIGS. 4A and 4B, and as shown in FIG. 5, by the fixing device 28 co-operating with a notch 36 formed in the first spacer element 24, where FIG. 5 is a diagrammatic detail of the assembly between the first and second spacer elements 24 and 26 in a plane substantially perpendicular to the plane of FIGS. 4A and 4B. FIG. 4B is a section view of FIG. 5 on a plane arranged at the level of the fixing device 28.

(49) It can thus be understood that the first spacer 20 is shaped in such a manner that the first and second spacer elements 24 and 26 have no degree of freedom to move relative to each other after the fixing device 28 has been fixed against the first spacer element 24. A fixing device 28 of any other shape could be devised.

(50) Without going beyond the ambit of the present invention, it would naturally be possible to devise first and second spacer elements 24 and 26 shaped in such a manner as to allow at least one degree of freedom to move between said elements, so as to enable gap to be created between the first and second spacers 20 and 22 and the first core 12. By way of example, such freedom to move could be achieved by eliminating the fixing device 28 formed on the second spacer element 26.

(51) Once more, and for reasons of clarity, one particular sequential representation of the method of the present invention is given above, however, and without going beyond the ambit of the present invention, it is just as possible to devise a method performed in a different order, or indeed a method in which all or some of the first and second spacer elements 24 and 26 and all or some of the first core 12 are assembled together in simultaneous manner.

(52) Furthermore and by way of nonlimiting example, the first and second spacer elements 24 and 26 define respective housings 32 and 34 that are configured to receive the second and third cores 14 and 16, respectively. The housings 32 and 34 are shaped in such a manner that gap is created between the second and third cores 14 and 16 arranged in said housings 32 and 34 and the corresponding spacer element so that the arrangement of said cores relative to said first and second spacer elements 24 and 26 is not constrained. Thereafter, the presence of gaps between the second and third cores and the respective spacer elements is configured to avoid constraining the arrangement of the first core 12.

(53) The first and second spacer elements 24 and 26 are thus shaped in such a manner as to be arranged easily and without special tooling between the first, second, and third cores 12, 14, and 16, while ensuring stability for the distances separating said cores from one another.

(54) In the example shown in the figures relating to the second embodiment, cooperation between the first and second spacer elements 24 and 26 takes place over end portions of said elements, e.g. over root portions of said elements, such that the spacer elements 24 and 26 present sections that vary along their longitudinal directions.

(55) The cores 12, 14, and 16 may be parts that are distinct, or they may be constituted by distinct branches of a common core. In other words, without going beyond the ambit of the present invention, it is possible to devise an assembly method in which all or some of the first, second, and third cores 12, 14, and 16 are connected to one another. Also, the present invention is naturally not limited to assembling three cores with two spacers.

(56) It can thus be understood that the use of spacers makes it possible to ensure that the cores are arranged relative to one another for the purpose of forming a non-permanent model without requiring the structure of said cores to be modified.

(57) The spacers may also include cooperation means, such as grooves, that are configured to cooperate with one of the cores, for the purposes, among others, of reinforcing the spacer and of improving the stability with which the spacer is positioned relative to said core.

(58) Although the present invention is described with reference to specific embodiments, it is clear that various modifications and changes may be undertaken on those embodiments without going beyond the general ambit of the invention as defined by the claims. In particular, individual characteristics of the various embodiments mentioned above may be combined in additional embodiments. Consequently, the description and the drawings should be considered in a sense that is illustrative rather than restrictive.

(59) It is also clear that all of the characteristics described with reference to a method can be transposed, singly or in combination, to a device, and vice versa, all of the characteristics described with reference to a device can be transposed, singly or in combination to a method.